Production of fertilizer (biosolids) from human excrement for use as soil conditioners.

 

CHAPTER ONE

  INTRODUCTION

 1.1  BACKGROUND OF STUDY

The average person excretes 72.5 kg of waste and urinates 500 gallons per year. With a world population of over seven billion people, we're talking about 507.5 billion kg of feces and 3,500 billion liters of urine per year. The single flush of a toilet may easily dispose of many people's wastes. However, the World Health Organization believes that a billion individuals are affected. People who do not have access to sanitation infrastructure defecate in pits and drains all over the world. Human excrement and urine now have immediate access to aquifers, contaminating drinking wells on a regular basis. Sanitation systems that are designed to recover resources in a safe and effective manner can aid in overall resource management in a community. On a scale ranging from a single rural household to a city, a variety of technologies and approaches can be used to acquire hugely beneficial resources and make them usable for safe, beneficial applications that support human well enough and overall sustainable development. But what if organic waste could be kept out of the water and used to generate electricity for farming? Excreta are most commonly used as a manure and soil enhancer in agriculture. This is also known as a "closing the loop" strategy for cleanliness in agriculture. It's an important part of the ecological sanitation strategy. Human feces include a variety of resources, including plant nutrients, organic materials, and energy. This study discusses the modeling of the variable parameters in developing safe fertilizer from human excreta to fertilize farms and gardens, which is especially important in areas without alternative sewage infrastructure.

1.2 PROBLEM STATEMENT  

The indiscriminate disposal of human waste is mostly due to the fact that around one billion people around the world lack access to sanitary amenities rather they defecate in sewers and pits. Human excrement and urine now have immediate access to aquifers, contaminating water wells on a regular basis. If this is not addressed, the rate/level of pollution in the environment will rise to the point where it is unhealthy for everyone. As a result, it is critical that these wastes be processed and repurposed for environmental reasons.

1.3 OBJECTIVE OF STUDY                                                                                            

Biosolids (organic fertilizer) are an environmentally beneficial and highly easy-to-handle commodity that may be used to harness organic wastes for use as fertilizer in farming. Biosolids are solid, semi-solid, or watery products of sewage treatment that have been properly processed to allow safe land application as an alternative to landfilling or cremation. This research aims to find the optimum biosolids  properties by modeling the variable parameters in the production of fertilizer (biosolids) from human excreta to improve biosolids handling features and land economic feasibility, as well as reduce the risk to human health, the environment, and unpleasantness issues that come with them.

1.4 SIGNIFICANCE OF STUDY

Biosolids are often burnt, landfilled, or applied to the ground. General standards, numerical restrictions on pollutant and pathogen amounts, managerial approaches, and technical requirements are all part of each disposal technique. Biosolids are now thought of to be valuable. This research sheds more light on the effects of biosolid properties that can be modified to achieve better grade biosolids, higher nutrient recovery, and the achieved properties can help effect a better public perceptive and approval in order promote the use of bisolids in agriculture.

 

1.5 SCOPE OF STUDY

The following topics are the subject of this research:

a)     A process for producing fertilizer (biosolids) from human excrement for use as soil conditioners.

b)     The advantages of reusing human feces.

c)     The advantages of using biosolids over chemical fertilizers.

d)     Development of models to show the effects of various variable parameters on organic fertilizer (biosolids) produced from human excreta.

The land application processes of biosolids, the regulations governing biosolids application, and the biosolids utilization rate in Nigeria are not included in this study.

CHAPTER TWO

2.0                                         LITERATURE REVIEW

2.1 FERTILIZER                                                                                                                          

To maintain sufficient food production, it is critical to ensure that plants receive the proper nutrients. Any natural or manmade substance (excluding liming materials) that is added to soil or plant tissues to give one or more plant nutrients required for plant growth is referred to as a fertilizer. Fertilizer comes in a range of natural and synthetic forms. Commercial fertilizer consumption has continuously expanded over the previous 50 years, nearly doubling to a present pace of 100 million tonnes of nitrogen per year. One-third of today's food could not be cultivated without industrial fertilizers, according to estimates.

2.1.1 Mechanism                                                                                                                

Fertilizers speed up the growth of plants. There are two ways to accomplish this goal. The first method is to employ nutrient-dense additions. The second method by which some fertilizers act is by modifying water retention and oxygenation in the soil. Fertilizers usually contain the following ingredients in varied proportions:

2.1.1.1 Three main macronutrients:                                                                                   

Nitrogen (N): contributes to leaves growth Phosphorus (P): Root, flower, seed, and fruit growth. Potassium (K): Promotes flowering and fruiting by promoting stem growth and water transport in plants 

2.1.1.2 Three secondary macronutrients                                                                              

 Sulfur (S), Magnesium (Mg), and Calcium (Ca).

2.1.1.3 Micronutrients                                                                                                               

Zinc (Zn), Boron (B), Manganese (Mn), Molybdenum (Mo), Copper (Cu), Iron (Fe) and Silicon (Si), Cobalt (Co), vanadium (V).

The elements are used to define the nutrients that plants require, but they are not employed as fertilizers. Fertilizers, on the other hand, are made up of compounds that include these components. The essential nutrients are consumed in increasing quantities and are present in plant tissue in concentrations ranging from 0.15 % to 6.0 % dry matter (0% moisture). The four fundamental elements found in plants are hydrogen, oxygen, carbon, and nitrogen. Carbon, hydrogen, and oxygen are common in water and carbon dioxide. Regardless of the fact that nitrogen constitutes up the bulk of the atmosphere, plants are unable to use it. Nitrogen is an essential fertilizer since it is present in proteins, DNA, and other constituents. To be a nutrient for plants, nitrogen must be made available in a "fixed" form. Only a few bacteria and their host plants (most notably legumes) are capable of converting nitrogen (N₂) in the atmosphere to ammonia. Phosphate is required for the synthesis of DNA, ATP (the cell's primary energy carrier), and some lipids.

Micronutrients are absorbed in smaller amounts and are detected in plant tissue at concentrations ranging from 0.15 to 400 parts per million (ppm) (less than 0.04% dry matter). These elements are typically found around the active sites of plant metabolic enzymes. Water-soluble salts are used to provide these nutrients. Iron converts into insoluble (bio-unavailable) molecules at moderate soil pH and phosphate concentrations, providing unique problems. As a result, iron is frequently given as a chelate complex, such as the EDTA derivative. Micronutrient requirements are determined by the plant and its surroundings. Sugar beets, for example, tend to require boron, while legumes require cobalt, and climatic factors such as heat or dryness reduce boron availability for plants. These elements have a significantly greater impact than their weight % because they enable catalysts (enzymes).

2.1.2 Classification                                                                                                          

Fertilizers are classified in several ways. Straight fertilizers are classified as single-nutrient fertilizers since they only provide one nutrient (e.g., K, P, or N). Multinutrient fertilizers (also known as "complex fertilizers") are fertilizers that contain two or more nutrients, such as nitrogen and phosphorus. Fertilizers are also classed as inorganic or organic (which is the subject of this article). Except for ureas, inorganic fertilizers do not contain carbon-containing compounds. Organic fertilizers are often made up of (recycled) plant or animal debris. Because of the multiple chemical processes necessary for their synthesis, inorganic fertilizers are sometimes referred to as synthetic fertilizers.

2.1.2.1 Single nutrient ("straight") fertilizers                                                                         

The most often used nitrogen-based direct fertilizers are ammonia or its solutions. Ammonium nitrate (NH₄NO₃) is also extensively used. Urea, like ammonia and ammonium nitrate, is a basic nitrogen source having the benefit of being solid and non-explosive. Calcium ammonium nitrate (Ca(NO₃)₂ • NH₄ • 10H₂O) has just a little share of the nitrogen fertilizer market (4 percent in 2007). Superphosphates are the most common straight phosphate fertilizers. SSP is made up of 14–18 percent P₂O₅, this time in the form of Ca(H₂PO₄)₂, as well as phosphogypsum (CaSO₄ • 2H₂O). TSP is normally made up of 44-48 percent P₂O₅ and no gypsum. Double superphosphate is a compound composed of single and triple superphosphate. A typical superphosphate fertilizer is water soluble to the tune of 90%. Muriate of Potash is the most common potassium-based straight fertilizer (MOP). Muriate of Potash is commonly offered as a 0-0-60 or 0-0-62 fertilizer and contains 95-99 percent KCl.

2.1.2.2 Multinutrient fertilizers                                                                                             

Fertilizers like this are routinely utilized. They're made up of at least two nutrients.           

♦Binary fertilizers (NP, NK, PK): Major two-component fertilizers provide both nitrogen and phosphorus to plants. They're referred to as NP fertilizers. The two most commonly utilized NP fertilizers are monoammonium phosphate (MAP) and diammonium phosphate (DAP) (DAP). The water solubility of MAP and DAP fertilizers is around 85%.

♦NPK fertilizers:                                                                                                                          

The three components of NPK fertilizers are nitrogen, phosphorus, and potassium. The NPK rating system is a method of characterizing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings (e.g., 10-10-10 or 16-4-8) are three digits spaced by dashes that characterize the chemical composition of fertilizers. The first figure indicates the product's nitrogen content; the second, P₂O₅; and the third, K₂O. Although fertilizers do not include P₂O₅ or K₂O, the system is a common abbreviation for the quantity of phosphate (P) or potassium (K) in a fertilizer. A 50-pound (23 kg) bag of fertilizer branded 16-4-8 includes 8 pound (3.6 kg) of nitrogen (16 percent of the 50 pounds), 2 pounds of phosphorus (4 percent of the 50 pounds), and 4 pounds of potassium (K₂O) (8 percent of 50 pounds). The N-P-K method is used by the majority of fertilizers, however the Australian system, which employs an N-P-K-S system, adds a fourth number for sulfur and uses elemental values for all components, including P and K.

2.1.2.3 Organic fertilizers                                                                                                          

The term "organic fertilizers" relates to fertilizers of an organic biologic origin, that is, fertilizers derived from live or previously living materials. Organic fertilizers can also refer to commercially produced and regularly packaged products that aim to satisfy the demands and restrictions set forth by "organic agriculture" and "environmentally friendly" gardening related food and plant production systems that use synthetic fertilizers and pesticides to a considerable extent or avoid them entirely. Certain organic materials, as well as appropriate additives such as nutritious rock powders, ground sea shells (crab, oyster, etc. ), other prepared products such as seed meal or kelp, and cultivated microorganisms and derivatives, are generally included in organic fertilizer products.

Organic fertilizers include animal wastes, agricultural plant wastes, compost, and treated sewage sludge (biosolids). Aside from manures, animal supplies can include bloodmeal, bone meal, feather meal, hides, hoofs, and horns from animal slaughter. Organically produced items available to industry, such as sewage sludge, may not be ideal components of organic farming and gardening due to difficulties ranging from residual toxins to public perception. Processed organics, on the other hand, may be incorporated in and promoted by commercially available "organic fertilizers" due to their consumer appeal. The majority of these items, regardless of definition or composition, have less concentrated nutrients that are more difficult to assess. They may have soil-building properties and appeal to those who want to farm or garden in a more “natural” way.

In terms of volume, peat is the most widely utilized commercially available organic soil supplement. It's an immature form of coal that improves soil aeration and water absorption while giving plants no nutritional value. As a result, it is classified as an amendment rather than a fertilizer, as stated at the beginning of the article. Coir (made from coconut husks), bark, and sawdust all behave similarly (though not identically) to peat when applied to soil because of their restricted nutrient inputs. Organic soil additions and texturizers are other names for them. Some organic texturizers (as well as compost and other materials) can have a negative impact on nutrition. Fresh sawdust can deplete soil nutrients, lowering pH, but organic texturizers (as well as compost, etc.) can improve nutrient availability by boosting cation exchange or promoting the proliferation of microbes, which in turn raises the availability of certain plant nutrients. Organic fertilizers such as composts and manures can be distributed locally without going through the production process, making accurate tracking of actual consumption more challenging.

 

2.2 HUMAN EXCRETA                                                                                                   

According to research, (Niwagaba C.B., 2009) on (Treatment Technologies for Human Feces and Urine): Feces and urine, which make up human excreta, are waste products of biological metabolism. The aesthetic, physical, and chemical characteristics of urine and feces vary depending on the health of the person excreting the waste, as well as the amount and type of food and fluids eaten (Lentner et al., 1981; Feachem et al., 1983). Material that passes through the intestines undigested is combined with material absorbed from the bloodstream or shed from glands and the intestines (Guyton, 1992), mucus, and bile, giving feces their unique brown hue (Featherstone, 1999). Feces include large amounts of dangerous viruses, bacteria, protozoa cysts, and helminth eggs (Faechem et al., 1983; WHO, 2006). Urine is the blood's excreta portion, which is filtered by the kidneys (Guyton, 1992). Because the body uses urine to balance liquids and salts, the amount of urine excreted by an individual varies (Jönsson et al., 2004). Water makes up 93-96 percent of urine (Vinners et al., 2006), with high amounts of water-soluble plant nutrients (Jönsson et al., 2004).

2.2.1 Generation rate                                                                                                                  

The volume of feces produced by an individual is determined by the type of food ingested. Foods that are low in fiber, such as meat, produce less feces (both in terms of mass and volume) (Guyton,1992). Feces output in affluent countries ranges from 80 to 140 g/p,d (wet weight), equivalent to 25 to 40 g/p,d dry matter (Lentner et al., 1981; Feachem et al., 1983; Jönsson et al., 2005; Vinners et al., 2006). The average fecal excretion rate in developing countries is 350 g/pd in rural areas and 250 g/pd in urban areas (Feachem et al., 1983). In China, Gao et al. (2002) reported 315 g/p,d, while Pieper (1987) found 520 g/p,d. Schouw et al. (2002) determined that the wet feces generation rates of 15 people in three different areas of Southern Thailand ranged from 120 to 400 g/p,d. One stool per person per day is the normal rate of feces excretion, but it can range from one stool per week to five stools per day (Lentner et al., 1981; Feachem et al., 1983).                               

The amount of urine excreted is determined by how well a person drinks and sweats, as well as other factors like nutrition, physical action, and weather (Lentner et al., 1981; Feachem et al., 1983). Excessive sweating produces concentrated urine, whereas excessive liquid ingestion dilutes the pee. The average adult's urine production rate is between 1000 and 1300 g/p,d (Feachem et al., 1983). Based on observations in Sweden, Vinners et al. (2006) proposed a design value for pee generation of 1500 g/p,d, while Schouw et al. (2002) discovered that 600-1200 g/p,d of urine was excreted in Southern Thailand. Rossi et al. (2009) reported a urine generation rate of 637 g/p,d on working days and 922 g/p,d on weekends based on measurements in Switzerland, which is consistent with Jönsson et al. (1999) who reported 610-1090 g/p,d based on measurements in Sweden.

2.2.2 Nutrients in excreta

The nutrients in feces are derived from the food that has been consumed. (Berger, 1960; Lentner et al., 1981; Guyton, 1992; Vinners et al., 2006) estimate that 10-20% nitrogen (N), 20-50% phosphorus (P), and 10-20% potassium (K) are transferred to the fecal fraction in proportions of 10-20% N, 20-50% P, and 10-20% K. (K). Ammonia, which is biochemically degraded from proteins, peptides, and amino acids, accounts for 20% of fecal nitrogen, while live bacteria account for 17%, and the rest is organic nitrogen mixed in with substances like uric acid and enzymes (Lentner et al., 1981). (Jönsson et al., 2005; Vinners et al., 2006) found that feces in Sweden contain an average of 550 grams of nitrogen, 183 grams of potassium, and 365 grams of potassium per person and year. Among the waste and wastewater portions, urine contains the largest concentration of plant nutrients (Figure 4). Plant nutrients evacuated by urine have been measured at 2.5-4.3 kilogram N, 0.4-1.0 kg P, and 0.9-1.0 kg K per person and year (Lentner et al., 1981; Vinners et al., 2006).

Figure 2.1: Proportions of nutrients found in household wastewater fractions and biowaste in Sweden. Source: Jönsson et al., 2005.

Jönsson et al. (2005) and Vinners et al. (2006) looked at previous urine nutritional content studies and found that the annual excretion rate per person in Sweden is roughly 4000g N, 330-365 g P, and 1000 g K. In Sweden, 4500-4600 g N, 500-550 g P, and 1400 g K are discovered in urine and feces per year (Jönsson et al., 2005; Vinners et al., 2006). Based on FAO food supply figures, Jönsson and Vinners (2004) calculated the amount of nutrients in Ugandan excreta to be 2500 g N and 400 g per person per year.

 

2.2.3 Pathogens in excreta

A healthy person's feces include a significant number of bacteria from a variety of non-pathogenic species, referred to as normal intestinal microbiota. Pathogenic bacteria in the gastrointestinal tract are not found in the normal microbiota of the intestine (Feachem et al., 1983). Their presence in feces indicates infection in the population that contributed to the analyzed feces. However, some commensal bacteria, also known as normal gut microbiota, might cause disease on rare occasions. This scenario is more likely to occur when a person's immune system has been impaired, such as during illness or old age, allowing opportunistic infections to flourish (Madigan and Martinko, 2006).

Many other intestinal pathogenic or potentially pathogenic microorganisms enter a new host through ingestion (dirt, water, food on fingers and lips, aerosols captured in the nose and swallowed), inhalation (after inhalation of aerosol particles), or eye (when eyes are rubbed with contaminated fingers) (Feachem et al., 1983). After infecting the host, a large number of germs may be discharged. Depending on the population's health, harmful bacteria, viruses, parasite protozoa, and helminths may be detected in the feces of the population, and hence in the mixed wastewater. In terms of hygiene, any contact with fresh/untreated excrement offers a risk (Feachem et al., 1983; Schönning and Stenström, 2004; WHO, 2006). Esrey et al. (1998) developed a disease transmission channel chart that began with the letter F and ended with the letter F. As a result, it's known as the F-diagram (Figure 2.2).

 

 

 

 

Figure 2.2: The F-diagram, showing the faecal disease transmission routes to a new host and the possible sanitation barriers. Adapted from Esrey et al., 1998.

Bacteria of various species are among the pathogens that can be found in feces (e.g. Aeromonas spp., Campylobacter jejuni/coli, Shigella spp., pathogenic E. coli, Pleisiomonas shigelloides, Vibrio cholerae and Yersinia spp.), Salmonella typhi/paratyphi, Salmonella spp., viruses (e.g. Enteric adenovirus 40 and 41, Hepatitis A virus, Hepatitis E virus, poliovirus and rotavirus), parasitic protozoa (e.g. Entamoeba histolytica, Cryptosporidium parvum, Giardia intestinalis) and helminths (e.g. Trichuris trichiura (whipworm), Ancylostoma duodenale/Necator americanus (hookworm),  Schistosoma spp. (blood flukes),  Taenia solium/saginata (tapeworm), and Ascaris lumbricoides (roundworm)) (Schönning and Stenström, 2004; WHO, 2006). Most  fecal pathogens induce gastrointestinal symptoms such diarrhoea, vomiting, and stomach cramps, but some can also cause symptoms in other organs (Schöning and Stenström, 2004; WHO, 2006).

Few  pathogens, such as Salmonella typhi, Schistosoma haematobium, Leptospira interrogans, and Salmonella paratyphi, are found in urine during infection (Feachem et al., 1983; WHO, 2006), while others, such as Mycobacterium tuberculosis, are in urine during renal tuberculosis infection (Feachem et al., 1983; WHO (Daher et al., 2007). Viruses including BK virus and Simian virus 40 have also been found in the urine of children (Vanchiere et al., 2005). Leptospira interogans is conveyed via diseased animals' urine, and human urine transmission is uncommon (Feachem et al., 1983). Despite the fact that Salmonella typhi and Salmonella paratyphi can be discharged in urine from typhoid and paratyphoid patients after the bacteria have been disseminated by blood, environmental transmission via urine is limited due to Salmonella sppshortshort .'s survival time in urine (only a few hours) (WHO, 2006).

Feces were discovered in 22% of the source-diverted urine samples tested in a Swedish examination. Höglund et al. (2002) found an average of 9 mg of feces per litre of pee in the contaminated samples. The urine must first be cleansed before it can be used as a fertilizer.

 

2.3 TREATMENT OF URINE

2.3.1 Urine Storage and Treatment                                                                                       These studies investigated how dilution (and hence ammonia content) and temperature affect organism inactivation, as well as how solar exposure affects the rate of inactivation and the time required to sanitize urine. Three urine dilutions and four storage temperatures were studied in triplicate for seven months in the laboratory. The dilutions (urine:water) ranged from undiluted urine (6.0 g N_NH3/NH4 L^-1) to 1:1 to 1:3 (1.5 g N_NH3/NH4 L^-1) to represent urine dilutions found in practice in sanitation systems, and  the was carried out at 4, 14, 24, or 34 °C to account ambient storage temperatures found around the world. At the above dilutions and temperatures, the die-off of  S. Typhimurium phage 28B, coliphage ɸx 174, Enterobacteriophage MS2, Enterococcus faecalis (E. faecalis) and Salmonella Typhimurium (S. Typhimurium) was investigated.                                                                                                                                  The treatment of urine in 10 L plastic jerry cans was evaluated in the field for three months in Kampala, Uganda, under three different ambient exposures: totally in the sun (S), partly in the sun near a wall (W), and within a ventilated room (R). Complementary research was conducted on urine in 50 mL centrifuge tubes in a laboratory incubator adjusted to mimic a cyclic temperature pattern comparable to that obtained from the field study's exposure to the sun. The researches were motivated by the fact that the majority of the existing literature focused on pathogen die-off in preserved urine at constant temperature. However, in real-world modest treatment systems, such as jerry can storage, the urine temperature varies during the day. The temperature of the contents of exposed containers can be raised by direct sunshine. It's crucial to know how many hours of direct sunshine are required to elevate the temperature of urine in exposed containers. The monthly average daily relative sunlight duration in Kampala is approximated to be between 0.31-0.62 hours, equating to 3.7-7.4 hours (Mubiru and Banda, 2007; Mubiru et al., 2007), which is consistent with the approximated 2-3 hours of bright sunlight per day during the research (Mubiru and Banda, 2007; Mubiru et al., 2007).                    E. coli O157:H7, Enterococcus spp., S. Typhimurium, and Ascaris suum eggs were researched in the field. Instead of Enterococcus spp., E. faecalis was researched in the lab, and the phages studied were included.

 

2.3.1.1 Dilution and temperature

The concentration of ammonia in urine is affected by dilution. At 24 °C, the predicted concentrations of uncharged ammonia (NH3) in 1:0, 1:1, and 1:3 urine:water dilutions were 156 11, 60 4, and 24 6 mM, respectively (Paper IV). Organism inactivation was slow and showed little dependence on ammonia concentration below a concentration of approximately 40 mM of unionised ammonia (Figure 2.3).

Figure 2.3: Time (days) for one decimal reduction (t₉₀) plotted as a function of uncharged ammonia for S. Typhimurium (● ), Enterococcus faecalis (○ ), MS2 (■ ) and ɸ x 174 (□ ) and S. Typhimurium phage 28 B (× ) in urine stored at temperatures a) 34, b) 24, c) 14 and d) 4 °C. The correlation trend is indicated with thin lines for the bacteria (Enterococcus faecalis broken line) and with bold lines for the phages (ɸ x 174 broken).

 

pH was only marginally influenced by the rate of dilution investigated, making single inactivation effects owing to pH difficult to separate. The pH values match up favorably to those obtained from Ugandan urine. After spiking with the organisms, the average pH of the collected urine decreased slightly to 8.8. The lower the pH changes between the temperatures, the less diluted the urine is. At 4 and 14 °C, the pH of concentrated urine (1:0) was 9.1; at 24 and 34 °C, it was 9.0. At 4 and 14 °C, the pH of diluted urine was 8.8, 8.7-8.8 at 24 °C, and 8.8 at 34 °C. At 4 °C, the pH of diluted urine was 9.1, 8.9 at 14 °C, and 8.7 at both 24 and 34 °C. Even when free ammonia was 50 mM, the reduction in E. faecalis and phages (MS2, ɸx, and 28B) was slow at 4 and 14 °C, as seen by significant t₉₀ values (Table 2.1), and the inactivation rate was less linked with free ammonia concentration. To sanitize urine stored at 4-14 °C, lengthy retention times of up to 6 months are required (Schönning and Stenström, 2004; WHO, 2006).

 

Table 2.1: Decimal reduction (t₉₀) in days ± S.D(%) for the bacteria S. Typhimurium, E. faecalis, MS2, ɸ x 174 and phage 28B at different temperatures and urine concentrations.

NR = no reduction detected during 182 days, except for the temperature control (0:1) which was studied during 40 days.

The death of S. Typhimurium occurs at 24 °C. According to the t₉₀ values in Table 2.1, its die off was rapid regardless of the dilution. E. faecalis t₉₀ values rose dramatically (by around 20 times) from pure urine through 1:1 to 1:3 dilutions (Table 2.1). Only in unadulterated urine did the t₉₀ values for MS2, ɸx, and 28B differ slightly, and they all climbed to t₉₀ values around 5 to 6 times as long with 1:3 dilution (Table 2.1; Figure 2.3).

The reduction rates of all species studied at 34 °C exhibited a linear relationship with NH₃. S. Typhimurium and E. faecalis were decreased to less discovery limits between a day and three days, respectively, at this temperature, resulting in extremely short t₉₀ values (Table 2.1). This data, along with the decrease in apparently stable phages with t₉₀ of 2 days to 2 weeks (Table 2.1), suggests that urine should not be stored at 34 °C for more than 2 months, even if it is used to fertilize lettuce. At 34 °C and with urine diluted 1:0, 1:1, and 1:3, no live Ascaris suum eggs were identified on days 7, 8, and 10, with 440 to 1,446 eggs seen on each day (Nordin et al., 2009a). Chandran et al. (2009) recommended that undiluted urine held for roughly 1 week at 30 C should be safe for use as a crop fertiliser based on E. coli, S. Typhimurium, and MS2 studies.

For every 10 degrees Celsius increase in temperature, biological activity is projected to double (Madigan and Martinko, 2006). The rate of ammonia permeability entering a cell is affected by temperature, with low permeability at low temperatures (Jenkins et al., 1998).

When the concentration of free ammonia in urine is above 40 mM, e.g. 2.8 g N_NH3/NH4 L^-1 and pH 8.8, low or no numbers of organisms remain after just brief storage times at 24^oC, according to Figure 2.3 and the short t₉₀ values (Table 2.1). A slightly lower ammonia concentration would result in the same concentration of unionised ammonia at a higher pH or temperature (NH₃). At 34°C, all dilutions, as well as 1:0 and 1:1 at 24°C, exceeded the sterilising concentration of approximately 40mM of free ammonia, below which almost all organisms demonstrated a much longer life span according to t₉₀ values (Figure 2.3), whereas only the undiluted urine (1:0) reached this dilution at 4 and 14°C. As a result, urine is sanitized by a combination of warmth and free ammonia.

 

2.3.1.2 Microbial Inactivation

When the urine was diluted, the t₉₀ values for E. faecalis were higher than those for S. Typhimurium (Table 2.1). The reduction in S. Typhimurium was not highly associated to the various urine dilutions examined, as t₉₀ was unaffected by the 1:1 and 1:3 dilutions and was only 6.5 days at most (Table 2.1). At 34 °C, regardless of urine content, E. faecalis was rapidly reduced, however at lower temperatures, undiluted urine had a substantially shorter t₉₀ than diluted urine (Table 2.1). At all temperatures, the t90 of undiluted urine was less than 7 days, whereas the t₉₀ of 1:3 dilution was 33 days at 4°C. During the 40 days of study, only a tiny decline was discovered in the temperature controls at 34°C, and the reduction was slight at 24°C and below (Table 2.1). E. coli O157:H7 was shown to be more susceptible to ammonia than S. Typhimurium when tested in a 1:1 urine:water dilution at 4 and 34 °C. According to Mendez et al. (2004), the outcome of ammonia treatment of S. Typhimurium and E. coli 0157:H7 are consistent. The lowest NH₃ concentration examined was 15 mM, which corresponds with Park and Diez-Gonzalez (2003), who found that 5 mMNH₃ was the lowest inhibitory concentration for S. E. coli and Typhimurium In a broth solution, there are E. coli. As a result of this, E. S. coli and E. coli Typhimurium appears to be particularly sensitive to uncharged ammonia, and will always be killed off quickly, even at levels lower than those commonly encountered in source separating sewage systems. E. S. coli and E. coli in urine collected and retained from these systems for short periods of time (days to weeks), especially at temperatures over 20°C, Typhimurium should not be a concern.

 

Figure 2.4: Log concentration (pfu mL^-1) of MS2, studied in triplicate, as a function of time (days) in urine diluted 1:1 at 34 °C. 

MS2 and ɸx 174 reduction kinetics diverged from first order kinetics, with an initial fast decrease followed by a breakpoint, followed by a slower decline. The reduction in MS2 phage in urine diluted 1:1 and held at 34°C demonstrates this (Figure 2.4). The ostensibly initial quick reduction phase was left out of the fitting since it would have exaggerated sanitation effectiveness and was explained by artefacts like urine particle adhesion.

Chandran et al. (2009) found a rapid drop of MS2 in urine held at 30°C and 15°C (within 1 week), which differs significantly from the model depicted in Figure 2.4. Their urine was not diluted and was maintained in locked containers for 6 months before to their experiments, resulting in a high ammonia/ammonium content of 8.57 g L^-1. Chandran et al. (2009) found that the ammonium concentration in urine was roughly twice that previously measured, and that storing it at 30°C resulted in significant quantities of aqueous ammonia, which is the most likely reason for the pee's quick cleanliness.

The t₉₀ for ɸx 174 and MS2 at 4°C and 14°C ranged from 28 to 240 days, with little link to urine dilution and no difference in sensitivity between the two phages. At 4 and 14°C, S. Typhimurium phage 28B showed little or no decrease. Höglund et al. (2002) found very little decline in S. Typhimurium phage 28B at 5°C after 200 days, which corresponds with our findings. Höglund et al. (2002) found that rhesus rotavirus had a significantly shorter inactivation period (T₉₀ = 35 days) than S. Typhimurium phage (T₉₀ = 71 days). Studies of the ammonia sensitivity of coated viruses, such as Avian influenza, show that coated viruses reduce ammonia levels significantly faster than phages previously used (Emmoth et al., 2007). As a result, pathogenic viruses appear to be more susceptible to ammonia treatments than the phages investigated, providing a buffer when urine is treated.

 

2.3.2 Urine storage at varying temperatures

2.3.2.1 Organism Inactivation

In a field research in Uganda, neither Salmonella spp. nor E. coli were discovered in large amounts in fresh urine, although Enterococcus spp. were (106 cfu mL^-1 urine). The starting concentration of all organisms tested was 105-108 cfu mL^-1 urine after spiking. After 24 hours of urine exposure at any of the three exposure locations, S. Typhimurium and E. coli were inactivated and undetectable (sun, wall and room). E. coli and S. Typhimurium were decreased from 6log10 to non detectable amounts (10 cfu mL^-1 urine) in just 11 and 14 hours, respectively, in a separate laboratory research.

Enterococcus spp. were far more resistant than the other bacteria studied, and they were discovered in the field research until day 37, but at concentrations close to the discovery limit (10 cfu mL^-1), with nearly identical t₉₀ values for all locations (S, W and R; Table 2.2). In a separate experiment, Enterococcus spp. reached non-detectable levels on day 6 (t₉₀ = 1.8 days). In the complementing investigations, the inactivation rate for Enterococcus spp. was more than four times higher than in the field study (Table 2.2). MS2 was the most sensitive of the three phages investigated, and on day 22, it was close to the discovery limit (1 cfu mL^-1 urine). With t₉₀ values of 37 and 55 days, respectively, the ɸX and S. Typhimurium phage 28B, which were sampled for 42 and 48 days, respectively, expressed slower inactivation (Table 2.2).

 

Table 2.2: Reduction coefficients with standard error, k±SE (log10 cfu/pfu d^-1) for the linear regression of exponential inactivation of the organisms studied. Time for 1log₁₀ reduction (t₉₀) is given as mean/upper 95% confidence interval in days.

At day 42 of the field investigation, the viability of the Ascaris suum eggs in the sun site was 1%, whereas the viability in the wall and room locations was 4±1% and 40±5%, respectively (Figure 2.5) When compared to the initial viability, the NaCl end-controls from days 40 to 42 exhibited no significant loss.

A lag phase with no inactivation or even higher viability than the initial was reported in the supplementary study until day 15. A lower inactivation rate was found starting on day 24, when the viability had dropped to 12%, (Figure 2.5). There were no viable eggs on day 40, (Figure 2.5). The best fit for the sun location for an equation giving the die-off for a lag duration of 18.5 days and a T₉₀ of 27.6 days was used to fit lag phase models for shouldered survival curves of Ascaris suum (Table 2.2).

Figure 2.5: Viability of Ascaris suum eggs (% of initial viability) incubated in urine in 10 L jerry cans exposed to sun (●), wall (×) and room (□ ) location

 Table 2.3: Reduction models for the inactivation of Ascaris suum eggs. Times of lag and for 1log₁₀ reduction (t₉₀) are given as mean/upper 95% confidence interval in days.

The lag phase was less pronounced at the wall and room locations, therefore a simple exponential inactivation equation was adopted (Table 8), albeit linear regressions fit almost equally well due to the few data points and large variation between repetitions.

 

2.4 TREATMENT OF FAECES

Fresh feces should always be treated with caution due to the possibility of high pathogen concentrations (Feachem et al., 1983; WHO, 2006). As a result, feces should be sanitized at all times. Storage, composting, burning, and chemical treatment are examples of treatment and sanitation methods.

 

2.4.1 Storage

The number of microorganisms (including pathogens) in feces should decrease after removal due to natural die-off. This is especially true because enteric bacteria and pathogens (as well as faecal markers) are accustomed to body temperature and a little above, and thus are thought to grow best at 37 to 44 ℃. Certain bacteria, such as Salmonella, and some indicator organisms, such as E. coli, will grow in their storage medium/environment if conditions suitable to their growth are kept. The number of E. coli and Enterococcus spp. may increase (Schönning and Stenström, 2004; WHO, 2006). Pathogen counts are affected by pH, moisture, temperature, nutrition, oxygen, ammonia content, and UV exposure during storage (Peasey 2000; Schönning and Stenström, 2004; WHO, 2006; Wichuk and McCartney, 2007; Austin and Cloete, 2008; Winker et al., 2009).

In areas where the ambient temperature reaches 20 degrees Celsius, a total storage time of 1.5 to 2 years (including time spent storing during primary treatment, i.e. under the toilet vault) will remove most bacterial pathogens and greatly reduce viruses, protozoa, and parasites (Schönning and Stenström, 2004; WHO, 2006),because pathogens die quicker at higher temperatures (up to 35 °C), a one-year total storage duration will achieve the same result in regions with higher ambient temperatures (Schönning and Stenström, 2004; WHO, 2006). This is consistent with Strauss and Blumenthal (1990), who claimed that under tropical circumstances (28-30 °C), one year was adequate for inactivation of diverse types of faecal pathogens, whereas at lower temperatures (17-20 °C), 18 months would be required. At 22-37 °C, however, Ascaris has been found to have a prolonged survival period of 2-3 years (Moe and Izurieta, 2004). Enterococcus spp. were not reduced after 50 days of storage at 20 °C, while Salmonella spp. were not reduced at 4 °C, according to Vinners et al. (2007). As a result, at low temperatures, extensive storage times are required to provide adequate faecal sanitation.

 

2.4.2 Composting

Composting is the microbial biological decomposition of organic waste into a humus-like stable product in an aerobic, moist, and self-heating environment. Composting is often used to recycle potentially biodegradable trash, sterilize potentially pathogen-contaminated materials, and bioremediate toxic waste (Haug, 1993). A well-run and managed thermophilic compost process generates a product free of pathogens and plant seeds that may be applied to land to give nutrients, humus, and organic matter for soil improvement (Epstein, 1997; Arvanitoyannis et al., 2006; Arvanitoyannis and Kassaveti, 2007).

When a well-conditioned substrate (enough energy, nutrients, moisture, structure, etc.) is composted, aerobic breakdown of organics occurs. Exothermic denotes that the process generates heat and raises the temperature. The heat generated either remains in the compost mass, exits by conduction, convection, and radiation, or is lost as a byproduct of the exiting gas. Enough heat should be retained in the compost matrix to keep the material in the composting process hot enough for sanitation. This demands a well insulated compost, at least on a small and medium scale. The outer sections of large compost piles act as insulators for the inside parts of the pile, resulting in a temperature gradient within the pile, with the highest temperature in the interior (Finger et al., 1976).

Microorganisms perform organic degradation, which is a biological process. Elements that affect microbial development have an impact on the composting process. Moisture, oxygen, pH, temperature, and the C/N ratio are all factors affecting substrate composition (Miller, 1993; Haug, 1993).

Moisture: Moisture in the compost substrate provides a pathway for dissolved nutrients to be transported to microorganisms for metabolic and physiological processes (McCartney and Tingley, 1998).  In a liquid environment with 100 percent MC (Finger et al., 1976), the highest rate of transfer of nutrients and waste products occurs, but controlling aerobic composting systems in these conditions becomes problematic. The ideal moisture for efficient composting of various forms of garbage was 25-80 percent (Ahn et al., 2008) and 50-60 percent (Tiquia et al., 1998), according to Suler and Finstein (1977); Bishop and Godfrey (1983); McKinley and Vestal (1984); Tiquia et al., 1998). (Suler and Finstein, 1977; Bishop and Godfrey, 1983; McKinley and Vestal, 1984; Tiquia et al., 1998). The wide range of ideal moisture content observed reflects the differing structural properties of the various substrates undergoing composting. Wood chips, for example, can compost at high moisture levels, whereas poorly structured substrates, such as food waste, require lower moisture levels. At low beginning moisture (e.g., 25%), early drying of the compost material happens readily, halting the biological process and resulting in physically stable but biologically unstable composts (Liang et al., 2003). (de Bertoldi and colleagues, 1983).  Waterlogging can induce anaerobic conditions in most substrates, preventing aerobic compost breakdown and creating acid production and odor concerns (Schulze, 1962; Tiquia et al., 1996). (Schulze, 1962; Tiquia et al., 1996).

Oxygen: To function properly, microorganisms engaged in aerobic composting of substrate organic matter require oxygen. Composts can be oxygenated through mechanical aeration, convective air flow (passive aeration), diffusion, and manual stirring (Epstein, 1997). Regardless of the method used for oxygen supply, oxygen diffusion in the aqueous layer around the substrates and into the pores of the substrate is crucial during composting. The barrier to oxygen diffusion in the compost matrix causes an oxygen gradient throughout the pile, with the lowest oxygen concentrations in the interior (Finger, 1976).

pH: The early phases of the composting process cause pH to drop due to the formation of organic acids, which are created by the fermentation of easily degradable organic matter (Beck-Friis et al., 2003). Organic acids interfere with microbial life processes when they are in their undissociated condition, that is, when the pH is low (Sundberg, 2005). During the initial phase of composting, organic acids tend to lower pH, but the carbonic and ammonia systems, depending on the substrate, balance the pH drop to varying degrees of efficacy (Sundberg, 2003). As the acids are used and ammonium is produced later in the process, the pH rises to roughly 7.5-8.5 (Beck-Friis et al., 2003). (Beck-Friis et al., 2003; Jeris and Regan, 1973). Most bacteria are unable to survive at pH 3 or lower, and they begin to die at pH 10.5 and above, with substantial mortality occurring at pH 11.5, (Haug, 1993).

Temperature: Due to microbial metabolism, the temperature rises as the composting process advances. The temperature increase inside composting materials is influenced by the initial temperature, biological heat evolution, and heat conservation (Miller, 1993). Based on temperature development, the composting process can be divided into three basic phases: mesophilic, thermophilic, and curing. During the mesophilic phase, temperatures reach roughly 40 degrees Celsius. The transition from mesophilic to thermophilic happens about 40-45 °C. The thermophilic phase is defined by temperatures ranging from 45 °C to 70 °C, and sometimes even higher (Miller, 1996), while the curing phase is defined by temperatures below 40-45 °C (Chiumenti et al., 2005). Thermal sanitation occurs during the thermophilic phase.

Temperature affects the rate of decomposition, which can be described as the rate of carbon dioxide evolution. Temperatures below 20 degrees Celsius have been demonstrated to hinder or impede composting (Mosher and Anderson, 1977). Depending on the type of substrate composted, the temperature at which maximal decomposition occurs is predicted to be between 50 and 67 degrees Celsius (Suler and Finstein, 1977; Haug, 1993; Miller, 1993; Richard and Walker, 1999; Eklind et al., 2007). Pathogen inactivation is achieved, according to Schönning and Stenström (2004) and WHO, when temperatures above 50 °C are maintained for at least one week (2006). The larger the temperature margin above 50 °C and the longer this temperature is maintained, the stronger the sanitation impact. High temperatures cause protein denaturation, which leads to cell death (Madigan and Martinko, 2006).

The temperature in the center of a composting heap is usually higher than at the edges (Haug, 1993). Insulation should be employed to prevent heat loss in order to attain and maintain high temperatures throughout the pile (Karlsson and Larsson, 2000; Björklund, 2002; Vinners et al., 2003a). Insulation is also necessary while composting in tiny heaps in tropical climes (Karlsson and Larsson, 2000). Even with insulation, low temperatures will exist in some locations of the compost, such as at the air inlet. To subject the material to high temperatures in such cold climates, the compost must be well mixed on a regular basis (Epstein, 1997; Vinners et al., 2003a).

C:N ratio: One of the criteria that impacts the composting process and quality is the C:N ratio (de Bertoldi et al., 1983; Michel et al., 1996). When microorganisms are growing, they require digestible carbon for energy and nitrogen for cell formation (Epstein, 1997). During aerobic metabolism, microbes need around 15 to 30 parts C for every part N. (Haug, 1993). At C/N ratios of 15 to 30, nitrogen is present in sufficient proportions for cell synthesis, therefore no rate limit should be implemented (Haug, 1993). If the C/N ratio is more than 35 in the start, the bacteria will have to go through numerous lifecycles to oxidize the excess carbon until they reach the C/N ratio that is best for their metabolism (de Bertoldi et al., 1983). When composting substrates with low C/N ratios, excess nitrogen is lost by ammonia volatilisation, which is exacerbated at high pH and temperature (de Bertoldi et al., 1983; Eklind et al., 2007). When nitrogen is released as ammonia or nitrous oxide, it diminishes the usefulness of compost as a fertilizer and pollutes the air.

 

2.4.2.1 Moisture and pH   

Substrates with an initial moisture content of 37-57 percent self-heated swiftly to sterilizing temperatures, reaching >65 °C in just two days, but those with a moisture level of more than 63 percent self-heated slowly or not at all. This shows that starting the composting process somewhat drier and adding water as needed is preferable to starting with a high moisture level that could hinder the process. A moisture content of 40-60% is recommended for composting operations (Golueke, 1977, cit. Epstein, 1997; Haug, 1993; Chiumenti et al., 2005). Composting appears to be impeded beyond a moisture content breakpoint of 60-65 percent in the faeces/ash and food waste substrate, restricting the temperature increase. When substrates with an initial moisture content of >63 percent were composted, the moisture content remained high, resulting in evident water-logging. In fact, the mixtures dissolved into wet pastes. Spreading the combinations on a polyethylene sheet and drying them in the open air to roughly 50-60% moisture content did not cause them to heat up since they had lost their structure. According to Golueke, moisture content greater than 60% in composts impacts particle aggregation and air-filled porosity, which inhibits oxygen transfer throughout the composting process (1977, cit. Epstein, 1997).

Moisture affects pH; in one experiment, with a moisture content of 63 percent and a low pH, self-heating took 37 days to achieve 65 degrees Celsius. As seen in Figure 2.6, there appears to be a relationship between moisture and pH, with materials with a high initial moisture content (>65%) exhibiting low pH after composting. This is in line with other researchers' findings, and it's most likely the result of organic acid generation and buildup in anaerobic conditions (Sundberg et al., 2004; Nakasaki et al., 2009). Organic acids restrict microbial activity and development at low pH. (Sundberg et al., 2004). In the high-moisture-content experimental runs, this could have repressed microbial activity, preventing temperature rise even after sun-drying. The production of the cakes, as well as their lack of structure, may have hindered the composting process.

Figure 2.6: Minimum pH during composting plotted against the initial moisture content of the substrates.

 

The larger the amount of faeces/ash mixture, the higher the initial pH of the substrates. Materials with a pH of at least 6.9 (and up to 9.3) composted well, achieving thermophilic and sanitizing temperatures from the beginning or later. Thermophilic temperatures could not be reached by materials having a pH of less than 6. There appears to be a pH breakpoint between 6 and 7 below which thermophilic composting of substrates/materials is impeded, and above which the composting process proceeds easily, with thermophilic and sanitizing temperatures achieved. This is supported by Haug (1993), Epstein (1997), and Sundberg (2001). (2005). The quick rise in temperature in substrates with pH as high as 9.8 implies that the composting process can continue at this pH.

 

2.4.2.2 Substrate conditioning for moisture and energy

The ability of the compost to reach sterilizing temperatures is determined by feed conditioning. Co-composting with food waste or other organic waste may be necessary since a feces/ash mixture may not contain enough organics to maintain sterilizing temperatures (>50^oC) for a long enough duration (at least one week) to achieve sanitation. Haug (1993) developed a set of guidelines for determining whether the energy content of a material is sufficient for thermal composting. Because water evaporation consumes the most energy in composting, the ratio of water to the mass of biological volatile matter (W) can be used to determine whether enough energy is available to heat and evaporate the water. The ratio W is calculated using Equation 1 according to Haug (1993).

W = ………………………………………………..Equation (1)

Where k_S denotes the percentage of the substrate volatile solids that can be composted; Vs denotes the volatile solids content of the dry solids; Ss denotes the fractional solids (dry matter) content of the substrates; and Xs denotes the wet weight of the feed substrate.

To see if the compost substrate has enough energy to raise the temperature and evaporate the water, the computed W is compared to the recommended literature value of W8. When W>10, there is usually insufficient energy to raise the temperature and evaporate enough water. Equation 2 is also used to calculate another important statistic, the energy ratio (E) (Haug, 1993).

E = …………………………………………………….…..….Equation (2)

Hs denotes the amount of heat released per gram of biodegraded volatile solids. Haug, (1993) calculates Hs = 23.24 MJ g^-1 deteriorated Vs (5550 cal g^-1 degraded Vs). Composts with E>700, on the other hand, theoretically have enough energy for composting and drying, whereas composts with E˂600 do not (Haug, 1993).

Haug (1993) gives a rule of thumb for how much water a compost can store while remaining thermophilic. The thermodynamic conditions for temperature elevation and water evaporation during thermophilic composting are not met if the energy ratio, E (Calculated according to Eqn. 1), is less than 600 cal g^-1 and the water ratio, W (Calculated according to Eq. 2), is greater than 10. The calculated E and W values for all of the composts are presented in Figure 2.7, demonstrating that the E and W rule of thumb agrees well with the data. Except for one, all well-functioning composts had E>600 cal g^-1 and W˂10. The exception is the W1:0 compost in Experiment 2, which had E=500 cal g^-1, close to 600 cal g^-1, while its W was 11, i.e. just over 10 (Figure 2.7). This demonstrates the validity of the basic rule of thumb that E and W are important indicators of compost performance.

Figure 2.7:  Theoretical energy ratio, E (cal g^-1) versus water ratio, W. Dotted lines are limit values for non-functional composts (Haug, 1993).

 

 

2.4.3 Incineration

Incineration of feces is a treatment method that eliminates germs while also being a compact and quick operation that allows for rapid inactivation. Furthermore, the amount of material left diminishes until all that is left is ashes. There is little need for extra disposal because the ashes can be reused as cover material during the collecting process in UDD toilets. As a result, the issue of providing cover material for the collecting phase, which is common, can be addressed.

The temperature is raised to such a high level during incineration that any germs present should be rendered inactive after only a few minutes of exposure. Low-cost small-scale incinerators made of steel sheets have been promoted by international organisations, mostly for the disposal of healthcare waste. In most of these circumstances, incinerators are used to eliminate potential health risks associated with sharps scavenging, as well as the risk of disease transmission such as hepatitis and HIV/AIDS (WHO, 2004b).

Incinerating materials that contain inorganic or organic chlorides yields more dioxins than non-chloride materials (Shibamoto et al., 2007). Temperatures above 450 °C result in the synthesis of dioxin, which is considerably reduced at temperatures above 850 °C (Shibamoto et al., 2007). This is in accordance with EU directives (89/429/EEC, discussed in Nasserzadeh et al. (1995)), which stipulate that air pollution is reduced when the combustion chamber temperature reaches at least 850 °C and the gases are exposed to this temperature for at least two seconds in the presence of at least 6% oxygen.

90-100 percent losses of N, S, and C (Partridge and Hodgkinson, 1977; Heard et al., 2000) and 24 percent losses of P, 35 percent losses of K, and 75 percent losses of S (Partridge and Hodgkinson, 1977; Heard et al., 2000) have been reported, as well as 24 percent losses of P, 35 percent losses of K, and 75 percent losses of S (Partridge and Hodgkinson, 1977; He (Heard et al., 2000). According to Jönsson et al. (2004), excrement incineration ash has high levels of P and K and can be utilized to fertilize soil for agricultural purposes, just like plant ash.

 

2.4.4 Chemical treatment

To treat feces for pathogen reduction, acids (e.g. phosphoric acid), bases (e.g. ammonia and lime), and oxidizing agents can all be utilized (e.g. chlorine). Agronomically beneficial molecules can be found in disinfection chemicals such Ca(OH)₂, NH₃, KOH, and PO₄^3-. These disinfectants are favored for substrates that will be recycled as fertilizers since the disinfectant's nutritional content increases the product's fertiliser value (Winker et al., 2009; Vinners et al., 2009).

For faecal matter sanitation (Vinners et al., 2003b; Nordin et al., 2009a,b; Vinners et al., 2009), as well as manure sanitation (Vinners et al., 2009), urea has been examined (Vinners et al., 2009). (Ottoson and colleagues, 2008). Ammonia, which is formed by enzymatic breakdown and results in uncharged ammonia, is used as a disinfectant in urea treatment systems. The pH rises as urea degrades, and when pH>9 is achieved, the majority of the ammonium/ammonia is uncharged ammonia, leading in even more bacterial cell disinfection due to ammonia toxicity (Warren, 1962; Pecson et al., 2007). Urea at a dose of 30 g ammonia nitrogen per kilogram of feces (3 percent ammonia nitrogen) is sufficient to make the material generally harmless after two months at 20 °C (Vinners et al., 2003b). In the study by Vinners et al., adding urea to feces resulted in a pH rise of roughly 9.3. (2003b). As a result, effective E. Escherichia coli (E. coli) disinfection E. coli, Enterococcus spp. Salmonella spp. and other bacteria, including E. coli. Within three weeks, there was a >6log10 drop in chemical-resistant phage S, as well as a decrease in chemical-resistant phage S. Typhimurium 28B, which translates to a 7.5-day decimal reduction or a 45-day 6log10 reduction.

At high pH, ammonia inactivates bacteria (Warren, 1962; Nordin et al., 2009b), viruses (Cramer et al., 1983; Pesaro et al., 1995; Nordin et al., 2009b), Cryptosporidium oocysts (Jenkins et al., 1998), and Ascaris eggs (Ghiglietti et al., 1997; Pecson et al., 2007; Nordin et al., 2009a). Nordin et al. (2009a) studied the inactivation of Ascaris suum eggs in feces by ammonia at storage temperatures corresponding to different ambient temperatures (4, 14, 24, and 24oC), and reported that uncharged ammonia in concentrations of 60mM was effective in sanitizing feces. Ascaris suum eggs were reduced by 6log10 after one month of storage at 34^oC and six months at 24^oC. At 14^oC or lower, inactivation of Ascaris suum eggs was modest, with viable eggs after 6 months of storage at 60mM NH₃. In 2 months at 14°C or 1 week at 24°C and 34°C, respectively, treatment of feces from source-separating dry toilets with 1 percent urea achieves Salmonella reduction levels that meet the guidelines for safe reuse of feces as fertilizer (i.e. 6log10 reduction) (Nordin et al., 2009b). When 2 percent urea is added to S. Typhimurium phage 28B at 24 ^oC and 34 ^oC, a safe fertiliser for unrestricted use is produced in 8 months and 1 month, respectively (Nordin et al., 2009b).

 

2.5 MULTIPLE BARRIER CONCEPTS FOR SAFE USE IN AGRICULTURE           

Since the 1990s, Sweden has been researching methods to make the safe reuse of pee and feces in agriculture. In 2006, the World Health Organization (WHO) issued guidelines on the safe reuse of wastewater, excreta, and greywater. The many barriers to reuse notions have resulted in a comprehensive grasp of how excreta can be reused properly. The notion is also utilized in food production and water supply, and is commonly regarded as a set of treatment steps and other safety precautions to avoid disease transmission. The amount of treatment that excreta-based fertilizers need before they can be utilized safely in agriculture is determined by a variety of factors. It all depends on the additional obstacles that will be erected as part of the multiple barrier concepts. Choosing the right crop, farming methods, fertilizer application methods, education, and so on are examples of such barriers. In the case of urine-diverting dry toilets (UDDTs), secondary treatment of dried feces can be done at the community level rather than at the household level, and can include thermophilic composting (where fecal material is composted at over 50 °C), prolonged storage (1.5 to two years), chemical treatment with ammonia from urine to inactivate pathogens, and solar sanitation.                                                                                                                                                                                                                                                                                                              

2.6 COMPARISON TO OTHER FERTILIZERS                                                               

Excreta from humans has untapped fertilizing potential. The theoretical amounts of nutrients that can be extracted from human excreta in Africa, for example, are similar to all of the continent's current fertilizer consumption. As a result, reuse can assist enhance food output while also serving as a viable alternative to chemical fertilizers, which are often out of reach for small-scale farmers. Dietary consumption, on the other hand, has a significant impact on the nutritional value of human excreta.                                                                                                                                      

Heavy metals can be found in mineral fertilizers, which are created from mining activities. Heavy metals such as cadmium and uranium are found in phosphate ores and can enter the food chain through mineral phosphate fertilizer. Excreta-based fertilizers are exempt from this, which is a benefit.                                                                                                                                

Animal manure is frequently not applied as precisely as mineral fertilizers in intensive agricultural land usage, resulting in low nitrogen consumption efficiency. Excessive usage of animal manure can be a concern in intensive agriculture areas with large numbers of livestock and little farmland.                                                                                                              

Organic fertilizers' fertilizing ingredients are typically bonded in carbonaceous reduced compounds. The fertilizing minerals are adsorbed on the breakdown products (humic acids) and other degradation products if they have previously been partially oxidized, as in compost. As a result, they have a slower release and are usually less quickly leached than mineral fertilizers.

 

2.7 BIOSOLIDS                                                                                                                

According to studies by (Gregory K. Evanylo, 2003) (Department of Crop and Soil Environmental Sciences, Virginia Tech.):

2.7.1 History of Biosolids                                                                                                  Biosolids are organic wastewater solids that can be reused after sewage sludge treatment techniques such as anaerobic digestion and composting have stabilized the sludge.

Alternatively, municipal rules may define biosolids as wastewater solids that have completed a specific treatment sequence and/or have pathogen and hazardous chemical concentrations that are below prescribed levels. The Clean Water Act was revised as public concern developed about the dumping of larger volumes of particles collected from sewage during the sewage treatment prescribed by the Clean Water Act in the United States. The Water Environment Federation (WEF) needed a new term to distinguish the clean, agriculturally viable product produced by modern wastewater treatment from earlier varieties of sewage sludge, which were infamous for being unpleasant or toxic. Biosolids is credited to Dr. Bruce Logan of the University of Arizona, who was awarded by the World Economic Forum in 1991. The United States Environmental Protection Agency (EPA) defines sewage sludge and biosolids as follows in CFR Title 40, Part 503: Sewage sludge refers to solids separated during the treatment of municipal wastewater (including domestic septage), whereas biosolids refers to treated sewage sludge that meets EPA pollutant and pathogen requirements. A similar name has been used in other countries, such as Australia. It's possible that the term "biosolids" will be regulated by the government. In informal usage, however, sewage or sewage sludge refers to a wide spectrum of semi-solid organic substances. This could include any solids, slime solids, or liquid slurry residue created during the treatment of home sewage, as well as scum and particles eliminated during primary, secondary, or advanced treatment operations. "Wastewater solids" is another word for materials that do not match the regulation definition of "biosolids."

2.7.2 Physiochemical Properties and Nutrient Level Of Biosolids                             

Biological, chemical, and physical analyses can be used to establish a biosolid's appropriateness for land application. The composition of biosolids is determined by wastewater elements and treatment techniques. The qualities that arise will influence the application technique and rate, as well as the level of regulatory control that is required. Biosolids have a number of key qualities, including:

 • Total solids: are made up of suspended and dissolved solids and are usually stated as a percentage of total solids in biosolids. Total solids concentration is determined by the kind of wastewater treatment and biosolids treatment prior to land application. Liquid (2-12 percent), dewatered (12-30 percent), and dry or composted solids are typical solids compositions of various biosolids processes (50 percent).

• Volatile solids: are usually represented as a percentage of total solids and offer an assessment of the rapidly decomposable organic matter in biosolids. At land application sites, volatile solids concentration is a key driver of potential odor issues. To lower volatile solids concentration and hence the possibility for odor, a variety of treatment procedures can be applied, including anaerobic digestion, aerobic digestion, alkaline stabilization, and composting.

• Trace Elements: Biosolids include trace elements in low amounts. Heavy metals are the trace elements that are of particular importance in biosolids. Some of these trace elements (e.g., Cu, Mo, and Zn) are nutrients required for plant growth at low quantities, but at large concentrations, all of these elements can be hazardous to humans, animals, or plants. The potential for phytotoxicity (i.e., plant harm) or a rise in the concentration of potentially dangerous compounds in the food chain are two potential risks linked with trace element accumulation in the soil. The following nine trace elements have federal and state regulations: arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), mercury (Hg), molybdenum (Mo), nickel (Ni), selenium (Se), and zinc (Zn) (Zn).

• pH and Calcium Carbonate Equivalent (CCE): are both measures of a substance's acidity or alkalinity. To lower pathogen concentration and attract disease-spreading organisms, the pH of biosolids is frequently raised with alkaline materials (vectors). Most infections are killed by high pH (higher than 11), and most metals' solubility, biological availability, and mobility are reduced. Lime also causes the ammonia (NH₃) type of nitrogen to gasify (volatilize), lowering the N-fertilizer value of biosolids. The relative liming effectiveness of biosolids is represented as a percentage of the liming capability of calcium carbonate (calcitic limestone).

Figure 2.8: A plot of pH against Time (weeks)

 • Nutrients: These are the nutrients necessary for plant growth that give biosolids their commercial significance. N, P, K, calcium (Ca), magnesium (Mg), sodium (Na), S, B, Cu, Fe, Mn, Mo, and Zn are among them. Biosolids concentrations vary widely, hence the actual material being considered for land application should be examined.

• Organic chemicals: are complex compounds that incorporate both natural and man-made substances. Industrial waste, household items, and insecticides all include chemicals. Many of these chemicals are hazardous or carcinogenic to organisms when exposed to critical quantities for long periods of time, however the majority of them are found in biosolids at such low levels that the U.S. They do not represent a major risk to human health or the environment, according to the EPA. Despite the fact that no organic contaminants are currently included in federal biosolids laws, the National Research Council has advised that more research be done on a number of specific organic substances (2002).

• Pathogens: microorganisms that cause disease, such as bacteria, viruses, protozoa, and parasitic worms. If pathogens are conveyed to food crops cultivated on land where biosolids are treated, included in runoff to surface waters from land application locations, or transported away from the site by vectors such as insects, rodents, and birds, they can pose a public health risk. As a result, pathogen and vector attraction reduction standards for biosolids applied to land are specified in federal and state laws.

2.7.3 Nutrient levels in Biosolids

Over the last 25 years, there have been very few comprehensive surveys of nutrient levels in biosolids. (Stehouwer et al. 2000) conducted a recent study that found that the macronutrient (N, P, and K) concentration of biosolids has remained relatively constant from the late 1970s to the mid 1990s. Between 1993 and 1997, more than 240 samples were collected and examined from 12 publicly owned treatment works (POTWs) in Pennsylvania, and the data in Table 2.4 represents the means and variability of those samples. The POTWs each produced a minimum of 20 analytical records between 1993 and 1997. The 12 POTWs produced 110 to 60,500 tons of biosolids per year and processed them using aerobic digestion (3 facilities), anaerobic digestion (4 facilities), or alkaline addition (5 facilities).

 

Table 2.4: Means and variability of nutrient concentrations^a in biosolids collected and analyzed in Pennsylvania between 1993 and 1997 (Stehouwer et al., 2000).

Nutrient (%)	Total N	NH4-N	Organic N	Total P	Total K
Mean	4.74	0.57	4.13	2.27	0.31
Variability	1.08	0.30	1.03	0.89	0.27

Concentrations are on a dried solids basis. 

 

2.7.4 Benefits of Land Application of  Biosolids

Biosolids might be considered a waste or a beneficial soil enhancement. Rather than landfilling or cremation, land application recycles soil-enhancing materials such as plant fertilizers and organic debris. The delivery of nitrogen (N), phosphorus (P), and lime (L) are the key advantages of fertilizers (where lime-stabilized biosolids are applied). Sulfur (S), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), molybdenum (Mo), and boron (B)] are vital plant nutrients that are rarely acquired by farmers due to the unpredictability of crop reactions to their application.

 

 

2.7.5 Production of Biosolids:

The biological treatment of domestic wastewater is the primary source of biosolids (Figure 2.9). Physical and chemical techniques are frequently used to improve biosolids handling qualities, boost land application economic viability, and lower the risk of public health, environmental, and nuisance issues connected with land application practices. These techniques treat wastewater solids to kill disease-causing organisms and minimize qualities that can attract rats, flies, mosquitoes, or other disease-carrying species. The degree of pathogen reduction achieved and the possibility for odor creation will be influenced by the type and extent of wastewater treatment techniques used. Table 2.5 summarizes common treatment techniques and their implications on biosolids characteristics and land application strategies.

 

Figure 2.9: Schematic diagram of wastewater treatment facility (G.K. Evanylo , 2003)

2.7

  

6 Disadvantages of Land Application of Biosolids

Because biosolids application rates are modest, large land expanses may be required for agricultural usage. Careful planning is required for transportation and application timing that is compatible with agricultural planting, harvesting, and possible bad weather conditions.

Tractor trucks carrying roughly 20 tons of biosolids are commonly used to transport biosolids to the application location. This equates to about 3-5 dry tons per trailer at a solids concentration of 15-25 percent, or about the amount of biosolids distributed on one acre of land for crops like corn, soybeans, or wheat. As a result, there will be a significant amount of truck traffic for huge sites of several hundred acres over the course of several weeks. Increased traffic on local roads, odors, and dust are all potential community consequences that should be addressed through public informational briefings or public hearings. Biosolids transportation difficulties can be minimized by devising delivery schedules that are least likely to cause disruption.

Even when properly treated, biosolids will emit odors. Even in rural communities accustomed to the use of animal manure, the odors may be objectionable in unfavorable weather conditions. The stabilization process, application method, storage type, climatological circumstances, and site selection, as mentioned below, can all help to eliminate odors.

 • Biosolids are stabilized to reduce biological activity and odor. The scents produced by aerobic digestion, heat treatment, and composting are generally the least offensive. If not done correctly, anaerobic digestion has the potential to produce greater odor than other treatment procedures. Similarly, if not adequately stabilized and maintained, lime-stabilized biosolids, the most often used material in the state, can produce odors.

• The manner of application has an impact on the odor potential at the location. Immediate soil incorporation or direct soil injection will help to avoid odor issues.

 • Biosolids might be stored at the treatment plant, at the application site, or in a temporary facility. The preferred technique is to store the waste at the treatment plant (if it is isolated from the public). Off-site storage necessitates careful site selection and management in order to avoid odor issues.

• When biosolids are applied to the surface, weather factors (such as temperature, relative humidity, and wind) have an impact on odor severity. Spreading early in the morning, when the air is warm and rising, will help to diffuse the odor in the immediate area.

 • The location of the application is critical to the operation's success. The site should ideally be situated away from residential areas.                                                                                            Despite sufficient stabilizing techniques and favorable weather circumstances, objectionable scents will occasionally be present. If nearby property owners are subjected to chronic scents, expect complaints. A well-managed system with the right equipment and stabilized biosolids will greatly limit the risk of odors that are objectionable.

 

 CHAPTER THREE

3.0                                              METHODOLOGY

3.1 PRODUCTION OF FERTILIZER FROM HUMAN EXCRETA   

Biosolids (organic fertilizer) are produced primarily through biological treatment of domestic wastewater. According to studies by (G.K. Evanylo, 2003) as shown in figure 2.9, the Primary Sedimentation tanks are used to settle sludge while grease and oils rise to the surface and are skimmed off. The settled sludge at the bottom of the tank moves to the digester where the sludge is biologically stabilized by converting organic matter to carbon dioxide, water and methane. The effluent (containing sludge) from the primary sedimentation tank moves to the Aeration Tank where the sludge is acted on by denitrifying bacteria. The bacteria convert nitrates to nitrites and consume biodegradable soluble organic contaminants; (this process eliminates the sludge odor). After treatment, the effluent move to the secondary sedimentation tank where the excess sludge is separated and moves to the thickening unit while the settled sludge is recycled back to the aeration tank. In the thickening unit, a coagulant (polymer) is used to thicken the sludge then moved to the digester where it is further treated before being dewatered; (removal of its moisture content). The dewatered sludge (organic fertilizer) is collected and can be use for agricultural purposes.

                                                                                                                                            

3.2 THEORETICAL BACKGROUND (relationship between variable parametric conditions)                                                                                                                                    

The amount to which pathogens are inactivated and the maturity of the compost or organic fertilizer are determined by the chemical and physical variable conditions in the synthesis of fertilizer from human excreta. The variables are as follows:                                           

♦Temperature                                                                                                                                     ♦Time                                                                                                                                          

♦Ammonia concentration 

♦pH

♦Moisture content (MC)   

To create a correlation, we must first identify all of the variables that may influence it. Information on existing relationships was acknowledged as a reference in modeling fertilizer production empirically in a study conducted by Niwagaba (2009). The relationship between the abovementioned criteria has been discovered in order to assess the rate at which infections are inactivated as well as the substrate condition. The amount of moisture in the compost has an impact on aerobic compost deterioration as well as the pH. Pathogens are easily inactivated at a higher temperature for a shorter period of time or at a lower temperature for a longer period of time (according to literature, the higher the temperature beyond 50-55^oC (for feces) and 20, 24 or 30-34^oC (for urine), the shorter the time of inactivation, and vice versa). The links between these factors in achieving pathogen inactivation and compost maturity are explored and simulated in order to successfully model the creation of human excreta. Experiments on the generation of organic fertilizer from human excreta provided the data for the construction of models. The link between the above factors is used to create equations (they are variables in the equations).

3.3 DEVELOPMENT OF MODELS                                                                                           

In this section (section 3.3), some of the models were developed (eqns 3.3 and 3.4) while others (eqns 3.1, 3.2, 3.5) and (eqn 3.6) were obtained from Kamalu, (2010) and Adeyemo, (20..) respectively.

3.3.1 Relationship between Time (days) for decimal reduction and uncharged ammonia in urine stored at temperatures: 34^OC, 24 ^OC, 14 ^OC and 4 ^OC as shown in Figure 2.3:

…………………………….. (3.1)

Where:    

3.3.2 Relationship between Log concentration of MS2 (pathogen) and time (days) in urine diluted at 34 ^OC as shown in Figure 2.4:                                                                                                                                              The relationship between log concentration of MS2 and Time is a straight line graph i.e y = mx + k, where in this; ‘y’ is ‘In C’, ‘x’ is ‘t’ and ‘k’ is constant, so that:

……………………………………..… (3.2)

Where:      

                    m = slope of the graph

3.3.3 Relationship between Viability of Ascaris suum eggs incubated in urine and time (days) as shown in Figure 2.5:

…………………………. (3.3)

where:        

3.3.4 Relationship between Minimum pH during composting and Initial Moisture Content of the substrate as shown in Figure 2.6:

i) y = constant      ;      y = a₀

ii) y α x                 ;      y = a₁x

iii) y α x²               ;      y = a₂x²

iv) y α x³               ;      y = a₃x³    

Hence:

y = ………………………………………… (3.4)

where:        y = pH_min

              x = initial MC

              a₀ = constants

3.3.5 Relationship between Theoretical Energy ratio, E and Water ratio, W as shown in Figure 2.7:

…………………………………………………………………... (3.5)

where:        

3.3.6 Relationship between Time (weeks) and pH from Figure 2.8:

+A+B……………………………... (3.6)

where:       

                   

3.4 DATA COLLECTION                                                                                                         The data presented below were extracted from research works carried out by other international scholars in the net.

Table 3.1: Relationship between Time (days) for one decimal reduction and uncharged ammonia in urine stored at temperatures: 34^OC, 24 ^OC, 14 ^OC and 4 ^OC as shown in Figure 2.3, (Niwagaba, 2009).

Decimal Reduction Time (days)	10	20	40	60	80	100	120	140	150
NH3 Concentration (mM)	95	60	36	26	22	20	17	16	15

 

Table 3.2: Relationship between Log concentration of MS2 (pathogen) and time (days) in urine diluted at 34 ^OC as shown in Figure 2.4, (Niwagaba, 2009).

Time (days)	2.5	5.0	7.5	10	15	20	22.5	25
In (Conc.)	3.13	3.00	2.45	2.12	1.34	0.75	0.34	0

 

Table 3.3: Relationship between Viability of Ascaris suum eggs incubated in urine and time (days) as shown in Figure 2.5, (Niwagaba, 2009).

Time (days)	0	5	10	15	20	25	30	35	40
Viability (%)	100	117.5	118	103	66	27	7	2.5	0

 

Table 3.4: Relationship between Minimum pH during composting and initial moisture content of the substrate as shown in Figure 2.6, (Niwagaba, 2009).

pHmin	8.4	9.26	9.24	8.40	7.15	6.00	5.15	4.86
Moisture Content (%)	40	45	50	55	60	65	70	75

 

Table 3.5:  Relationship between Theoretical Energy ratio, E and Water ratio, W as shown in Figure 2.7, (Niwagaba, 2009).

Energy (cal/g)	2100	1088	600	376	268	223	200
Water Ratio (W)	3.23	5	10	15	20	25	30

 

Table 3.6: Relationship between Time (weeks) and pH from Figure 2.8, (Yadav et al., 2010).

pH	6.50	9.33	9.25	8.90	8.60	8.38	8.25
Time(weeks)	0	1	2	3	4	5	6

 

 

3.5 CURVE FITTING                                                                                                                The numerical values in the tables (experimental values from the works of scholars) were plotted using MATLAB toolbox to obtain scatter diagrams. The models were superimposed on the scatter diagrams. The toolbox was made to apply the models on the scatter diagrams. Profiles will be plotted showing the models following the scatter diagrams and simultaneously, the numerical values of the constants of the models will be declared with 95% confidence bound as well as their statistical goodness of fits.

3.5.1 Goodness of Fit Statistics                                                                                                  The proposed models were fitted into plots corresponding to the data gathered in Tables 3.1-3.6. Curve Fitting Toolbox software was used to do this. The Curve Fitting ToolboxTM software can also be used to assess the goodness-of-fit statistics for parametric models like:

a)     The sum of squares due to error (SSE),

b)      R-square,

c)     Adjusted R-square,

d)      Root mean squared error (RMSE).

3.5.1.1 Sum of Squares Due to Error                                                                                        The overall deviation of the response values from the fit to the response values is measured by this statistic. It's also known as the summed square of residuals, and it's abbreviated as SSE.

 …………………………………………… Equation 3.7

A number around 0 suggests that the model's random error component is smaller, and therefore the fit will be more effective for prediction.

3.5.1.2 R-Square (R²)                                                                                                                 This number indicates how well the fit explains the variation in the data. R-square is the square of the correlation between the response values and the projected response values, to put it another way. It's also known as the multiple correlation coefficient squared or the multiple determination coefficient. The R-square is the ratio of the regression sum of squares (SSR) to the overall sum of squares (SST). SSR is defined as follows:

…………………………………………….  Equation 3.8

SST is also called the sum of squares about the mean, and is defined as

   SST=

Where SST = SSR + SSE.

Given these definitions, R-square is expressed as:

 …………………………………………….….  Equation 3.10

R-squared can have any value between 0 and 1, with a value closer to 1 suggesting that the model accounts for a bigger fraction of the variation. An R-square score of 0.9234, for example, indicates that the fit accounts for 92.34 percent of the total variation in the data concerning the average. Although the fit may not improve in a practical sense, R-square will increase as the number of fitted coefficients in your model grows. You should use the degrees of freedom adjusted R-square statistic mentioned below to prevent this problem.                                  It's important to note that equations without a constant term can have a negative R-square. Because R-square is defined as the proportion of variation explained by the fit, it is negative if the fit is worse than fitting a horizontal line. R-square cannot be understood as the square of a correlation in this circumstance. In these cases, a constant term should be included in the model.

 So,0 ≤ R² ≤ 1.

If SSR = SST, then R² = 0, and model is not useful.                                                                       If SSR = 0, then R² = 1, and model fits all points perfectly.                                                               Almost all models will be between these extremes.

3.5.1.3 Degrees of Freedom Adjusted R-Square                                                                      The R-square statistic is used in this statistic, however it is adjusted based on the residual degrees of freedom. The number of response values n minus the number of fitted coefficients m calculated from the response values equals the residual degrees of freedom.

……………………………………………………… Equation 3.11

The amount of independent pieces of information regarding the n data points necessary to calculate the sum of squares is denoted by the letter V. It's worth noting that if parameters are bounded and one or more estimates are at or near their bounds, the estimates are considered fixed. The number of such parameters increases the degree of freedom.                                     When comparing two nested models — that is, a series of models each adding extra coefficients to the preceding model — the modified R-square statistic is often the best indicator of fit quality.

1 - SSR(n−1) SST(v) …………………………………………...Equation 3.12

………………………..... Equation 3.13

Any value less than or equal to 1 can be used for the modified R-square statistic, with a value closer to 1 indicating a better match. When the model incorporates terms that do not help forecast the response, negative values can arise.

3.5.1.4 Root Mean Squared Error                                                                                             The fit standard error and the regression standard error are two terms for the same statistic. It is defined as:

………………………………………….. Equation 3.14

Where: MSE is the mean square error or the residual mean square

 ……………………………………………………… Equation 3.15

 Just as with SSE, an MSE value closer to 0 indicates a fit that is more useful for prediction.

CHAPTER FOUR

4.0                                   RESULTS AND DISCUSSION

4.1 RESULT PRESENTATION                                                                                                The plots and their tables as obtained from the previous section (chapter 3) are as shown here below: figures 4.1-4.6, and tables 4.1-4.6

FIGURES: 

Figure 4.1: A plot of Decimal Reduction Time versus Ammonia concentration

 (Model: , R-square: 99.94%)

Figure 4.2:  A plot of logarithm concentration of MS2 (pathogen) versus Time

 (Model: , R-square: 99.62%)

 

Figure 4.3: A plot of Viability of Ascaris suum eggs versus Time

(Model: , R-square: 99.94%)

 

  Figure 4.4:  A plot of Minimum pH versus Initial Moisture content of compost

(Model: F(x) = p1 × + p2 × + p3 × X + p4, R-square: 99.96%)

Figure 4.5: A plot of Theoretical Energy Ratio versus Water Ratio

(Model: , R-square: 99.42%)

Figure 4.6: A plot of pH against Time (weeks)

 (Model: , R-square: 99.85%)

TABLES:

Table 4.1: table of coefficients and statistical goodness of fit (Decimal reduction time versus Ammonia concentration)

Coefficient (with 95% confidence bounds)	Goodness of fit
	Parameter	Value
a = 129	SSE	3.422
b = -0.07471	R-square	0.9994
c =   35.76	Adjusted R-square:	0.9991
d =  -0.005931	RMSE	0.8273

 

 

Where: X = time in days

Table 4.2: table of coefficients and statistical goodness of fit (Natural log Concentration of MS2 versus Time)

Coefficients (with 95% confidence bounds):	Goodness of fit:
	Parameter	Value
p1 = -0.1428	SSE	0.03906
p2 = 3.56	R-square	0.9962
	Adjusted R-square	0.9955
	RMSE	0.08068

 

 

 

Table 4.3: table of coefficients and statistical goodness of fit (Viability of Ascaris suum eggs versus Time)

Coefficients (with 95% confidence bounds)	Goodness of fit
	Parameter	Value
p1 = -4.741x10-7	SSE	11.69
p2 = 2.991x10-5	R-square	0.9994
p3 = 7.46x10-5	Adjusted R-square	0.9978
p4 = -0.0256	RMSE	2.417
p5 = 0.04836
p6 = 3.706
p7 = 100.1

 

 

F(x) = p1 × + p2 × + p3 × X + p4

Table 4.4: table of coefficients and statistical goodness of fit (Minimum pH versus Initial Moisture Content of compost)

Coefficient (with 95% confidence bounds)	Goodness of fit
	Parameter	Value
p1 = 0.0004485	SSE	0.009463
p2 = -0.08123	R-square	0.9996
p3 = 4.655	Adjusted R-square	0.9993
p4 = -76.56	RMSE	0.04864

 

 

 

Table 4.5: table of coefficients and statistical goodness of fit (Theoretical Energy Ratio versus Water Ratio)

Coefficients (with 95% confidence bounds):	Goodness of fit:
	Parameter	Value
a = 4857	SSE	1.662x104
b = 0.8898	R-square	0.9942
	Adjusted R-square	0.9931
	RMSE	57.65

 

 

Table 4.6: table of coefficients and statistical goodness of fit (pH against Time (weeks))

Coefficient (with 95% confidence bounds)	Goodness of fit
	Parameter	Value
A = 3.3	SSE	0.008282
B = 3.202	R-square	0.9985
K2 = 0.1189	Adjusted R-square:	0.997
K1=2.701	RMSE	0.05254

4.2 RESULTS DISCUSSION AND DEDUCTION                                                                     

A plot of Decimal Reduction Time against Ammonia concentration in the production of organic fertilizer from human excreta is shown in figure 4.1. Note that Decimal Reduction Time is the measure of the die-off of bacteria in stored urine at a particular temperature in relation to the dilution of the urine. They model   simulate the production of organic fertilizer from human excreta with 99.94% (almost excellent) accuracy, leaving an error of 0.06%. They coefficient of the model constant are: a = 129, b = -0.07471, c = 35.76, and d = -0.005931. Observe that when Decimal Reduction Time is reducing rapidly, Ammonia concentration is increasing very slowly up to a point (18-35days Decimal Reduction and 60-100mM Ammonia concentration) where the rate of change of Decimal Reduction with Ammonia concentration ceases to be rapid before the variation change hand that is (where the manure is formed); Decimal Reduction begins to decrease slowly while Ammonia concentration begins to increase rapidly.

 A plot of Viability of Ascaris suum eggs against Time in days is shown in figure 4.2. Viability measures how capable the Ascaris suum eggs are for normal growth and development. The accuracy of the plot is 99.94% (almost excellent) only being fault with 0.06%. In the change of Viability with Time, we observe that the percentage Viability first increased from 100-118% in 8days and begins to decrease thereafter until about 30days when the percentage Viability is almost zero and then maintains a range of 0-8% between 30days and 40days.

A plot of Natural Logarithmic concentration against Time is shown in figure 4.3. A percentage accuracy of 99.62% (good) with a fault of 0.28% was obtained. The model is a straight line profile. It shows the inverse proportion relationship between Natural Logarithmic Concentration and Time (days) that is; as Natural Logarithmic Concentration decreases, the time in days increases.

A plot of Minimum pH against Initial Moisture Content is shown in figure 4.4. An accuracy of 99.96% (almost excellent) with a fault of 0.04% was obtained. As shown in the figure, the Minimum pH increases with time from 8.3 to 9.8 as a peak at about 48% Initial Moisture Content. After this point, the Minimum pH begins to decrease with increase in Initial Moisture Content until it comes to zero at about 74 – 75% Initial Moisture Content.

A plot of Energy against Water Ratio is shown in figure 4.5. The energy source of the compost is the fraction of organics in the substrate and the availability of this affects the heat production in the compost. The heat production together with the loss regulates the temperature increase during composting and this also affects the water evaporation during composting. The variation in figure 4.3 is similar to that in figure 4.1 only that the decrease in energy and the increase in water ratio happen slightly slowly. The formation of the manure is observed to be between 400 – 600cal/g of energy and 7 – 10 water ratios. The percentage accuracy of the model is 99.42% (good) hence having an error of 0.58%.

A plot of pH against Time in weeks is shown in figure 4.6. Observe that pH increase rapidly with slow increase in time until it attained a peak value of 9.45 after which it decreases slowly staying between the ranges of 8 – 9.45. The accuracy of the plot is 99.85% (very good) leaving an error of 0.15%.

From the data presented above, we observe that the variable parameters in the production of fertilizer from human excreta can be represented mathematically and modeled so that the prediction of the variations of these parameters can be achieved outside the laboratory. The prediction of the variance in these variable parameters gives a clear insight on what the nature of the expected end product (fertilizer) should be. Hence, a standard of the properties of organic fertilizer produced from human excreta can be established.   

CHAPTER FIVE

5.0                         CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION                                                                                                                        

In this research work, practical work was not done rather data from works of international scholars were studied and the variable parameters were modeled. The models gave an accuracy of between 99.42% - 99.96% and error of 0.04% - 0.58% only, showing that these variable parameters from the production of fertilizer from human excreta can be modeled.

This work can be very useful to fertilizer production companies and municipal waste water treatment plants in the analysis of the quality of fertilizer they produce from human excreta  ensuring they are eco friendly. It will as well help them not dwell entirely on laboratory test to predict variable parameters changes hence saves them time and cost of production.

 

5.2 RECOMMENDATIONS                                                                                               

Material handling in and around compost and waste water treatment plants should be investigated in order to develop good and practical handling instructions that will help to reduce the danger of disease spread.

More research is needed to develop effective ways to reduce odors and dangerous emissions from waste water treatment plants.

There is a need to look at low-cost, resource-efficient collection techniques, as well as encourage private sector participation in these practices, such as treatment, branding/certification, and the sale of treated excreta.

Finally, research is needed to evaluate the social and cultural acceptability, as well as barriers to the usage and adoption of various facial treatment approaches. Such research is also needed to determine whether the final products, compost, ash, and stored faces, can be used as fertilizer.