Environmental Technology
ISSN: 0959-3330 (Print) 1479-487X (Online) Journal homepage: http://www.tandfonline.com/loi/tent20
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire K. R. Effebi, G. T. Ballet, M. A. Seka, D. T. Baya & B. L. N’takpe To cite this article: K. R. Effebi, G. T. Ballet, M. A. Seka, D. T. Baya & B. L. N’takpe (2017): Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire, Environmental Technology, DOI: 10.1080/09593330.2017.1387610 To link to this article: http://dx.doi.org/10.1080/09593330.2017.1387610
Accepted author version posted online: 03 Oct 2017.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tent20 Download by: [University of Sherbrooke]
Date: 10 October 2017, At: 09:56
Publisher: Taylor & Francis & Informa UK Limited, trading as Taylor & Francis Group Journal: Environmental Technology DOI: 10.1080/09593330.2017.1387610
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
K. R. Effebia*, G. T. Ballet b, M. A. Sekab, D. T. Baya c and B. L. N’takpe a a
Laboratory of Geoscience and Environment, University of Nangui Abrogoua, 02 BP 801 Abidjan 02,
Côte d’Ivoire; b
Laboratory of Environment Sciences, University of Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte
d’Ivoire; c
Laboratory of Water and Sanitation, University of Liège, Arlon, Belgium.
* Corresponding Author, *E-mail: [email protected] (K.R. Effebi*); tel: +225 09 29 25 49 E-mails: [email protected] (G. T. Ballet), [email protected] (M. A. Seka), [email protected] (D.T. Baya); [email protected] (B. L. N’takpe)
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire Abstract We assessed the physicochemical and microbiological properties of composting toilets products in Abidjan, (Côte d’Ivoire) for their potential use in agriculture. Samples of urine and feces were collected and analysed after 123 days of storage in plastic cans (urine) and 8 months of storage in closed
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
composting bags (feces). Selected physicochemical parameters (ammonium, phosphorus, potassium, calcium, magnesium, cadmium, copper, lead and zinc) and pathogens (bacteria and helminths eggs) were monitored. Results showed that temperature and pH values were 26.0 °C and 7.2, and 27.6 °C and 8.6 for the feces-based compost and urine, respectively. The physicochemical analysis revealed high nutrient contents and low trace metal levels in the feces-based compost. Concentrations of magnesium, cadmium, copper, lead and zinc ranged from 0.46 to 54.98 mg/kg; whilst those of phosphorus, potassium and calcium, were > 700 mg/kg on average. In urine the concentrations of phosphorus, potassium, calcium, copper and zinc were 930, 1240, 1402.8, 0.0672, and 0.121 mg/L, respectively. Whereas ammonium concentration was 2012 mg/kg in feces-based compost and 57 mg/L in urine. Various bacteria including total coliforms, fecal coliforms, fecal streptococci, and anaerobic sulfite-reducers (ASR), along with Ascaris lombricoïds (1.66 eggs/g) were found in the feces-based compost. In the urine the analysis showed 20 Forming Colonies Unit (UFC) of fecal streptococci in 100 mL and 33 UFC of ASR in 50 mL. Our findings indicate that the feces-based compost was not homogeneous, namely with regards to the microbiological parameters, and an additional time would be necessary to bring it to stability. Keywords: by-products, compost, ecological sanitation, s latem, ttae iltam (1)
Subject classification codes: Ecological sanitation with compost production
1
Introduction Recent developments in household wastewater treatment and management are promoting dry
sanitation or dry toilet technology because of their better contribution to environmental sustainability [1, 2, 3]. For many years the conventional understanding of adequate sanitation was referred to the interruption of pathogen cycles without necessarily considering the effects on other human communities (downstream, for example) or on the environment. New definitions and criteria for sustainable sanitation are being developed to address these gaps. Indeed, various studies and reports including those from The
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
World Health Organization (WHO), United Nations Children's Fund (UNICEF) [4], and Bracken [5], mention that socially, economically and ecologically sustainable sanitation systems should incorporate equity, health promotion and protection from disease, and of the environment. The benefits of using dry sanitation systems are diverse. Cordova [3], Schönning [6] and Tonner-Klank [7] pointed out that through waterless, on-site treatment of excreta, these systems reduce water supply needs for cities, protect water quality from high nutrient and pathogen-laden discharges and produce a soil amendment material free from urban run-off and industrial contaminants, which can be reutilized in agriculture. The use of compost from composting toilets in agriculture indeed could reduce the risk of pollution and eutrophication. Compost from dry sanitation systems also contributes to reduce the use of chemical fertilizers [8, 9]. Furthermore, dry sanitation systems allow for economic savings due to the volumes of water that are no longer necessary to supply, distribute, collect and treat, and the lower capital investment costs they can imply [10]. Although, the amount of by-products generated from composting toilets is limited compared to those from classical sanitation technologies using water, the by-products from both systems have to be properly managed. Composting toilet is a naturally occurring aerobic process, whereby native microorganisms convert biodegradable organic matter into humus like product [11]. The majority of pathogens (e.g., total coliforms; fecal coliforms; fecal streptococci, anaerobic sulfite-reducers, Ascaris lombricoïds and Trichuris trichiuras) can be found in the human feces [11], and are major threats to soil and water quality.
Sources separating dry sanitation systems offer an alternative to meet the sanitation requirement; while plant nutrient, sand, and organic material from collected human excreta can be used for food production [12]. Separating fecal matter at the source would minimize the occurrence of Ascaris eggs in other wastewater fractions, such as sewage sludge and wastewater. However, it would increase the need for high energy-demanding sanitation methods for the fecal matter since it is no longer subjected to dilution. Nowadays, the most common treatment of source-separated fecal matter is low temperature composting, i.e., long-term storage with little or no increase of ambient temperature. However, reliable pathogen
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
inactivation is crucial for safe reuse of human excreta [13]. Pathogens and parasites found in human excreta are responsible of various diseases in developing countries [14, 15]. Sossou et al. [16] mentioned that composting matrixes (sawdust, rice husk and charcoal) and composting process did not significantly affect the inactivation rate of pathogenic bacteria. It did however impact their lethal capacity (namely when a pH increase is observed during composting). Human urine normally does not contain pathogens which could be responsible of human enteric diseases. Only in special cases, e.g., a systemic infection with fever or fecal cross-contamination, pathogens organisms will be present in urine [6]. In this paper we focused on composting toilets, especially on toilets with separation of urine and fecal matter. According to Schönning [6], this type of toilet offers different advantages including the reduction of pathogens, absence of odour and leaching to the water table. Several studies have examined the agricultural use of urine from this type of toilets in regions in Côte d'Ivoire, e.g. Dabou [17] and Aguié [18], and in Ouagadougou, Burkina Faso [19]. In Côte d'Ivoire, the use of human feces and urine from compsoting toilets as agricultural fertilizers is still at a pioneering stage and cannot be effective without a detailed characterization of human feces and urine. The main objective of this work was to characterize the human feces and urine from composting toilets in urban slums, Abobo Sagbé, Abidjan (Côte d'Ivoire) for their potential use in agriculture. First, the physicochemical and microbiological
parameters in the urine and feces-based compost were quantified. Then, the composts derived from fecal matter were assessed to check whether they were homogeneous and proper to agricultural use. 2
Materials and methods
2.1
Study area Located in the North of Abidjan, the municipality of Abobo is one of the thirteen (13)
municipalities of the Autonomous District of Abidjan. Its population is estimated at 1.5 million
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
inhabitants [20]. Twenty-eight (28) neighbourhoods and villages make up the municipality of Abobo, including a dozen precarious suburbs where 60% of its population live [21]. The study area, Sagbé, is one of the south-western suburbs of Abobo. 2.2
Implemented project The study was part of a project implemented in south Sagbé, a slum of the municipality of Abobo,
since 30 May 2013, which aims at (i) offering composting toilets to people in urban slums in order to stop open-air defecations, and (ii) generating new job opportunities while ensuring the management of excreta in households and their healthy use as fertilizer in agriculture. At the time of the study thirty-seven (37) composting toilets were involved in the project. Users were estimated at seven hundred and one (701). The filling time of the receptacles of materials is highly dependent on users. Thus, the filling of urine cans spanned thirteen (13) to twenty-six (26) days; with circa 740 L of urine collected and stored in 37 urine cans of 20 L each. Additionally, from six (6) to eight (8) months, 37,000 kg of feces were collected in 740 bags of 50 kg each and were left to stability. 2.3
Description of the composting toilets The composting toilets were built. The separation technique at the source in the monitored
composting toilets made it possible to manage the by-products (urine and fecal matter) separately through specific orifices. Thus, the urine was channelled via a PVC pipe and collected in a receptacle located outside the latrine, whereas fecal matters were collected directly in a pit mounted above ground. The fecal
matters were treated in two phases to allow an efficient elimination of pathogens. The first treatment of desiccation occurred during collection in a ventilated pit and consisted of the addition of bulking agent (e.g., sawdust, chips, etc.) after each defecation. This enables the moisture absorption and reduces the risk of odour and proliferation of flies. The second treatment or dehydration began after the filling up of the receptacle and its closure during a given time (i.e., 6 months). 2.4
Samples collection
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
Sample collection was carried out on 18 January 2016 at the storage site. Bottlers were subjected to target sampling first, followed by a random sampling within the latter’s. A urine can was thus selected and the temperature and pH values were determined in situ. The urine sample to be analysed in laboratory was subjected to a 2-step sampling process. First, 0.5 L of urine was sampled from each of the 37 cans (carefully wiggled beforehand) and was put in a new can. Then, from the 18.5 L of “new” urine sample 1 L was sampled and stored in a sterilized polyethylene bottle for laboratory analysis. Regarding fecal matters, they were collected from the pits into woven polypropylene bags. Note that during the 6-month storage in the pit, they were not rolled back before bagging. After a 2-day sun drying period, the content of each bag was bagged again and stored during 2 months. Sawdust or chips was used as bulking agent during the composting. At the end of the composting, 0.5 kg of fecal matter was removed from each of the bags (whose contents were homogeneously wiggled beforehand) and pooled, that is a total of 370 kg. This content was then homogeneously wiggled and put into different bags. Then, one bag was randomly selected and three samples were collected at 3 levels: below the surface (0-10 cm), at mid-depth (15-25 cm) and at depth (at 10 cm from the bottom). Each collected compost sample was further placed in a plastic bag and weighed (1 kg). The final urine and fecal matter samples were conserved in a cooler at 4°C and transported to the laboratory of the Ivoirian Anti-Pollution Center (CIAPOL), where the physicochemical and microbiological characteristics were determined.
2.5
Analysis The temperature and pH values of urine and fecal matter samples were measured using a
multiparametric probe HACH HQ 4O D. Metals [cadmium (Cd), lead (Pb), copper (Cu), mercury (Hg), and zinc (Zn)] and nutrients [potassium (K), calcium (Ca), and magnesium (Mg)] in urine and fecal matter were analysed using the Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Perkin Elmer 2000 DV. Whereas phosphorus (P) and ammonium (NH4+) were determined by HACH method 8190 and HACH method 10071, respectively, using spectrophotometers HACH DR 6000 and
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HACH DR 6000 (indophenol blue), respectively. The microbiology analysis focused on bacteria and helminths eggs by enumeration. A detailed description of the analysis is provided in the next subsections. Temperature and pH were determined according to [22, 23] standards. The pH values of the urine were obtained by immersing the probe into the urine can. For feces, 20 mg of compost was dissolved in 100 mL of distilled water. The whole was stirred for 5 minutes at room temperature with a mechanical stirrer. After settling, measurements were made on the liquid portion only. Metals, calcium, potassium, magnesium and phosphorus were determined through digestion process and analysis by ICP OES according to [24]. Regarding the feces-based compost, first, 30 mL of distilled water was added to a sample of 20 mg of compost and mixed. The solution obtained was then filtered through a membrane with a diameter of 0.45 μm. The membrane and the residue were treated with 4 mL of 65% nitric acid and 4 mL of hydrogen peroxide (H2O2) in a digestion vessel connected to a reflux condenser. The compound obtained was heated until a clear mineral was obtained, which was evaporated to 2 ml and cooled. Then, 10 mL of 0.2M hydrochloric acid was added. For the urine, a volume of 100 mL was sampled for analysis. After the filtration, treatment, heating and cooling steps, the dilution was carried out in the 15th and the addition of 10 mL of 0.2M hydrochloric acid. The whole was heated in a microwave oven at 175 ° C for 20 minutes in order to dissolve any residual material. After cooling, the solution was filtered again. Volumes of 20 mL were taken and placed in optical spectroscopy. The spectra were dispersed by a network spectrometer and the intensity of the lines was evaluated by a
detector (K: 578 nm, P: 880 nm, Ca: 239 nm, Mg: 202 nm, Cd: 228 nm, Cu: 324 nm, Zn: 213 nm, Pb: 217 nm). Ammonium was determined according to [25]: After digestion of 20 mL of urine, 1 mL was taken and diluted in the 100th. This same volume of distilled water was used to allow the digestion of 20 mg of compost. These solutions were filtered and volumes of 20 ml sampled. The ammonium ions in these different filtrates react with the mixture of 1 ml of phenol + 1 ml of hypochlorite + 1 ml of
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nitroprusside. The compound obtained was placed in a spectrophotometer, and the reading was made in absorbance at 630 nm. Dry matter was determined according to [26]. 10 g of compost was sampled and put in an aluminium container. The sample was then dried in an oven at 105 °C and cooled in a desiccator. The result is expressed as follows (equation 1): (1)
Where S is the percentage dry matter (% DM); A and B refer to the mass of the sample (g) after and before drying (g). Organic matter was determined according to [27] after determination of the dry matter (DM), the sample was calcined in a muffle furnace at 550 ° C. The residual material resulting from the combustion was the mineral matter (MM). The organic matter in percentage (OM (%)) was determined by calculating the difference between DM and MM (Equation 2). (2)
Pathogen bacteria: the method used for the detection of bacteria was based on membrane filtration according to the standard [28]. 5 mL of urine were transferred to a jar, then 1 mL was taken and diluted in the 100th. Regarding the feces-based compost, 20 mg were sampled and dissolved in 100 mL
of distilled water. After stirring and settling, 1 mL was sampled and filtered through sterile filter membrane (0.45 μm in diameter). After filtration, the membrane was placed under sterile conditions on petri dishes containing a solid culture medium (agar) before being incubated for 30 minutes at precise temperatures permitting the identification of the bacteria. For seeding, the culture media used varied according to the bacteria sought. ● Fecal Coliforms were searched using the "COMPASS® cc Agar". The reading was carried out
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after 18 to 24 hours of incubation at 44 ° C. Colonies of Fecal Coliforms appear in blue. ● Fecal Streptococci were identified after culture on 'Slanetz and Bartley agar'. The reading occurred after 44 ± 4 hours of incubation at 37 ° C. Colonies appear in dark roses or reds with or without a white aureole. Total Coliforms included all blue and pink or dark red colonies with or without a white aureole present in the culture media. They correspond to the bacterial load of the seeded inoculum. Taking into account the dilution rates of the samples, the number of bacteria was calculated according to equation (3). The results are expressed in Forming Colonies Unit (UFC). (3)
Where: Cs: number of bacteria in the reference volume Vs Vs: reference volume chosen to express the bacterial load N: sum of all colonies counted in the dishes from dilutions d1 and d2 n1, n2: number of boxes counted for dilutions d1 and d2 v1, v2: test volumes used for dilutions d1 and d2 d1, d2: dilutions used for the sampling v1, v2
Anaerobic sulfite-reducers (ASRs) were enumerated according to [29]. For the urine, 1 mL of urine was diluted to the 50th. Whereas for feces-based compost, 20 mg were sampled and dissolved into 50 ml of distilled water. Then after settling, 1 ml of solution was sampled. The samples were placed in an anaerobic tube containing 20 ml of agar supplemented with sulphites and iron III ammoniacal citrate. After incubation at 37° C, a black precipitate was formed from sulfites and sulfides. Each of the precipitates correspond to an ASR.
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Helminths eggs (Schistosomamansoni, Trichuristrichiuras and Ascaris lombricoïdes eggs) were determined using a method involving sodium acetate-acetic acid-formaldehyde (SAF) [30]. With regards to urine, 1 mL was sampled and diluted in the 100th. For feces-based compost, 1 g was sampled and dissolved into 100 ml of distilled water. For both solutions, a mixture of 5 ml of sodium acetate + 5 ml of acetic acid was then added in order to destroy any vegetative forms. Then, two drops of formalin were added to concentrate the eggs. These formal solutions were filtered through a filter membrane and the eggs collected. Eggs were identified according to their aspects using a microscope (10 × 40). 3 3.1
Results
Physicochemical and microbiological characteristics of the urine sample Table 1 shows the physicochemical and microbiological parameters analysed in the urine. These
results revealed that the temperature in urine sample was 27.6°C and the pH was basic (8.61). The concentration of calcium was the highest, followed by that of potassium, phosphorus, magnesium and ammonium. There were Metallic Trace Elements (MTE) in different proportions in the urine sample (Table 1). The zinc concentration was the highest, followed by that of copper, lead, cadmium and mercury. The concentration of the latter which was less than the reading threshold (
ISSN: 0959-3330 (Print) 1479-487X (Online) Journal homepage: http://www.tandfonline.com/loi/tent20
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire K. R. Effebi, G. T. Ballet, M. A. Seka, D. T. Baya & B. L. N’takpe To cite this article: K. R. Effebi, G. T. Ballet, M. A. Seka, D. T. Baya & B. L. N’takpe (2017): Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire, Environmental Technology, DOI: 10.1080/09593330.2017.1387610 To link to this article: http://dx.doi.org/10.1080/09593330.2017.1387610
Accepted author version posted online: 03 Oct 2017.
Submit your article to this journal
Article views: 3
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tent20 Download by: [University of Sherbrooke]
Date: 10 October 2017, At: 09:56
Publisher: Taylor & Francis & Informa UK Limited, trading as Taylor & Francis Group Journal: Environmental Technology DOI: 10.1080/09593330.2017.1387610
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
K. R. Effebia*, G. T. Ballet b, M. A. Sekab, D. T. Baya c and B. L. N’takpe a a
Laboratory of Geoscience and Environment, University of Nangui Abrogoua, 02 BP 801 Abidjan 02,
Côte d’Ivoire; b
Laboratory of Environment Sciences, University of Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte
d’Ivoire; c
Laboratory of Water and Sanitation, University of Liège, Arlon, Belgium.
* Corresponding Author, *E-mail: [email protected] (K.R. Effebi*); tel: +225 09 29 25 49 E-mails: [email protected] (G. T. Ballet), [email protected] (M. A. Seka), [email protected] (D.T. Baya); [email protected] (B. L. N’takpe)
Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire Abstract We assessed the physicochemical and microbiological properties of composting toilets products in Abidjan, (Côte d’Ivoire) for their potential use in agriculture. Samples of urine and feces were collected and analysed after 123 days of storage in plastic cans (urine) and 8 months of storage in closed
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
composting bags (feces). Selected physicochemical parameters (ammonium, phosphorus, potassium, calcium, magnesium, cadmium, copper, lead and zinc) and pathogens (bacteria and helminths eggs) were monitored. Results showed that temperature and pH values were 26.0 °C and 7.2, and 27.6 °C and 8.6 for the feces-based compost and urine, respectively. The physicochemical analysis revealed high nutrient contents and low trace metal levels in the feces-based compost. Concentrations of magnesium, cadmium, copper, lead and zinc ranged from 0.46 to 54.98 mg/kg; whilst those of phosphorus, potassium and calcium, were > 700 mg/kg on average. In urine the concentrations of phosphorus, potassium, calcium, copper and zinc were 930, 1240, 1402.8, 0.0672, and 0.121 mg/L, respectively. Whereas ammonium concentration was 2012 mg/kg in feces-based compost and 57 mg/L in urine. Various bacteria including total coliforms, fecal coliforms, fecal streptococci, and anaerobic sulfite-reducers (ASR), along with Ascaris lombricoïds (1.66 eggs/g) were found in the feces-based compost. In the urine the analysis showed 20 Forming Colonies Unit (UFC) of fecal streptococci in 100 mL and 33 UFC of ASR in 50 mL. Our findings indicate that the feces-based compost was not homogeneous, namely with regards to the microbiological parameters, and an additional time would be necessary to bring it to stability. Keywords: by-products, compost, ecological sanitation, s latem, ttae iltam (1)
Subject classification codes: Ecological sanitation with compost production
1
Introduction Recent developments in household wastewater treatment and management are promoting dry
sanitation or dry toilet technology because of their better contribution to environmental sustainability [1, 2, 3]. For many years the conventional understanding of adequate sanitation was referred to the interruption of pathogen cycles without necessarily considering the effects on other human communities (downstream, for example) or on the environment. New definitions and criteria for sustainable sanitation are being developed to address these gaps. Indeed, various studies and reports including those from The
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
World Health Organization (WHO), United Nations Children's Fund (UNICEF) [4], and Bracken [5], mention that socially, economically and ecologically sustainable sanitation systems should incorporate equity, health promotion and protection from disease, and of the environment. The benefits of using dry sanitation systems are diverse. Cordova [3], Schönning [6] and Tonner-Klank [7] pointed out that through waterless, on-site treatment of excreta, these systems reduce water supply needs for cities, protect water quality from high nutrient and pathogen-laden discharges and produce a soil amendment material free from urban run-off and industrial contaminants, which can be reutilized in agriculture. The use of compost from composting toilets in agriculture indeed could reduce the risk of pollution and eutrophication. Compost from dry sanitation systems also contributes to reduce the use of chemical fertilizers [8, 9]. Furthermore, dry sanitation systems allow for economic savings due to the volumes of water that are no longer necessary to supply, distribute, collect and treat, and the lower capital investment costs they can imply [10]. Although, the amount of by-products generated from composting toilets is limited compared to those from classical sanitation technologies using water, the by-products from both systems have to be properly managed. Composting toilet is a naturally occurring aerobic process, whereby native microorganisms convert biodegradable organic matter into humus like product [11]. The majority of pathogens (e.g., total coliforms; fecal coliforms; fecal streptococci, anaerobic sulfite-reducers, Ascaris lombricoïds and Trichuris trichiuras) can be found in the human feces [11], and are major threats to soil and water quality.
Sources separating dry sanitation systems offer an alternative to meet the sanitation requirement; while plant nutrient, sand, and organic material from collected human excreta can be used for food production [12]. Separating fecal matter at the source would minimize the occurrence of Ascaris eggs in other wastewater fractions, such as sewage sludge and wastewater. However, it would increase the need for high energy-demanding sanitation methods for the fecal matter since it is no longer subjected to dilution. Nowadays, the most common treatment of source-separated fecal matter is low temperature composting, i.e., long-term storage with little or no increase of ambient temperature. However, reliable pathogen
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
inactivation is crucial for safe reuse of human excreta [13]. Pathogens and parasites found in human excreta are responsible of various diseases in developing countries [14, 15]. Sossou et al. [16] mentioned that composting matrixes (sawdust, rice husk and charcoal) and composting process did not significantly affect the inactivation rate of pathogenic bacteria. It did however impact their lethal capacity (namely when a pH increase is observed during composting). Human urine normally does not contain pathogens which could be responsible of human enteric diseases. Only in special cases, e.g., a systemic infection with fever or fecal cross-contamination, pathogens organisms will be present in urine [6]. In this paper we focused on composting toilets, especially on toilets with separation of urine and fecal matter. According to Schönning [6], this type of toilet offers different advantages including the reduction of pathogens, absence of odour and leaching to the water table. Several studies have examined the agricultural use of urine from this type of toilets in regions in Côte d'Ivoire, e.g. Dabou [17] and Aguié [18], and in Ouagadougou, Burkina Faso [19]. In Côte d'Ivoire, the use of human feces and urine from compsoting toilets as agricultural fertilizers is still at a pioneering stage and cannot be effective without a detailed characterization of human feces and urine. The main objective of this work was to characterize the human feces and urine from composting toilets in urban slums, Abobo Sagbé, Abidjan (Côte d'Ivoire) for their potential use in agriculture. First, the physicochemical and microbiological
parameters in the urine and feces-based compost were quantified. Then, the composts derived from fecal matter were assessed to check whether they were homogeneous and proper to agricultural use. 2
Materials and methods
2.1
Study area Located in the North of Abidjan, the municipality of Abobo is one of the thirteen (13)
municipalities of the Autonomous District of Abidjan. Its population is estimated at 1.5 million
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
inhabitants [20]. Twenty-eight (28) neighbourhoods and villages make up the municipality of Abobo, including a dozen precarious suburbs where 60% of its population live [21]. The study area, Sagbé, is one of the south-western suburbs of Abobo. 2.2
Implemented project The study was part of a project implemented in south Sagbé, a slum of the municipality of Abobo,
since 30 May 2013, which aims at (i) offering composting toilets to people in urban slums in order to stop open-air defecations, and (ii) generating new job opportunities while ensuring the management of excreta in households and their healthy use as fertilizer in agriculture. At the time of the study thirty-seven (37) composting toilets were involved in the project. Users were estimated at seven hundred and one (701). The filling time of the receptacles of materials is highly dependent on users. Thus, the filling of urine cans spanned thirteen (13) to twenty-six (26) days; with circa 740 L of urine collected and stored in 37 urine cans of 20 L each. Additionally, from six (6) to eight (8) months, 37,000 kg of feces were collected in 740 bags of 50 kg each and were left to stability. 2.3
Description of the composting toilets The composting toilets were built. The separation technique at the source in the monitored
composting toilets made it possible to manage the by-products (urine and fecal matter) separately through specific orifices. Thus, the urine was channelled via a PVC pipe and collected in a receptacle located outside the latrine, whereas fecal matters were collected directly in a pit mounted above ground. The fecal
matters were treated in two phases to allow an efficient elimination of pathogens. The first treatment of desiccation occurred during collection in a ventilated pit and consisted of the addition of bulking agent (e.g., sawdust, chips, etc.) after each defecation. This enables the moisture absorption and reduces the risk of odour and proliferation of flies. The second treatment or dehydration began after the filling up of the receptacle and its closure during a given time (i.e., 6 months). 2.4
Samples collection
Downloaded by [University of Sherbrooke] at 09:56 10 October 2017
Sample collection was carried out on 18 January 2016 at the storage site. Bottlers were subjected to target sampling first, followed by a random sampling within the latter’s. A urine can was thus selected and the temperature and pH values were determined in situ. The urine sample to be analysed in laboratory was subjected to a 2-step sampling process. First, 0.5 L of urine was sampled from each of the 37 cans (carefully wiggled beforehand) and was put in a new can. Then, from the 18.5 L of “new” urine sample 1 L was sampled and stored in a sterilized polyethylene bottle for laboratory analysis. Regarding fecal matters, they were collected from the pits into woven polypropylene bags. Note that during the 6-month storage in the pit, they were not rolled back before bagging. After a 2-day sun drying period, the content of each bag was bagged again and stored during 2 months. Sawdust or chips was used as bulking agent during the composting. At the end of the composting, 0.5 kg of fecal matter was removed from each of the bags (whose contents were homogeneously wiggled beforehand) and pooled, that is a total of 370 kg. This content was then homogeneously wiggled and put into different bags. Then, one bag was randomly selected and three samples were collected at 3 levels: below the surface (0-10 cm), at mid-depth (15-25 cm) and at depth (at 10 cm from the bottom). Each collected compost sample was further placed in a plastic bag and weighed (1 kg). The final urine and fecal matter samples were conserved in a cooler at 4°C and transported to the laboratory of the Ivoirian Anti-Pollution Center (CIAPOL), where the physicochemical and microbiological characteristics were determined.
2.5
Analysis The temperature and pH values of urine and fecal matter samples were measured using a
multiparametric probe HACH HQ 4O D. Metals [cadmium (Cd), lead (Pb), copper (Cu), mercury (Hg), and zinc (Zn)] and nutrients [potassium (K), calcium (Ca), and magnesium (Mg)] in urine and fecal matter were analysed using the Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Perkin Elmer 2000 DV. Whereas phosphorus (P) and ammonium (NH4+) were determined by HACH method 8190 and HACH method 10071, respectively, using spectrophotometers HACH DR 6000 and
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HACH DR 6000 (indophenol blue), respectively. The microbiology analysis focused on bacteria and helminths eggs by enumeration. A detailed description of the analysis is provided in the next subsections. Temperature and pH were determined according to [22, 23] standards. The pH values of the urine were obtained by immersing the probe into the urine can. For feces, 20 mg of compost was dissolved in 100 mL of distilled water. The whole was stirred for 5 minutes at room temperature with a mechanical stirrer. After settling, measurements were made on the liquid portion only. Metals, calcium, potassium, magnesium and phosphorus were determined through digestion process and analysis by ICP OES according to [24]. Regarding the feces-based compost, first, 30 mL of distilled water was added to a sample of 20 mg of compost and mixed. The solution obtained was then filtered through a membrane with a diameter of 0.45 μm. The membrane and the residue were treated with 4 mL of 65% nitric acid and 4 mL of hydrogen peroxide (H2O2) in a digestion vessel connected to a reflux condenser. The compound obtained was heated until a clear mineral was obtained, which was evaporated to 2 ml and cooled. Then, 10 mL of 0.2M hydrochloric acid was added. For the urine, a volume of 100 mL was sampled for analysis. After the filtration, treatment, heating and cooling steps, the dilution was carried out in the 15th and the addition of 10 mL of 0.2M hydrochloric acid. The whole was heated in a microwave oven at 175 ° C for 20 minutes in order to dissolve any residual material. After cooling, the solution was filtered again. Volumes of 20 mL were taken and placed in optical spectroscopy. The spectra were dispersed by a network spectrometer and the intensity of the lines was evaluated by a
detector (K: 578 nm, P: 880 nm, Ca: 239 nm, Mg: 202 nm, Cd: 228 nm, Cu: 324 nm, Zn: 213 nm, Pb: 217 nm). Ammonium was determined according to [25]: After digestion of 20 mL of urine, 1 mL was taken and diluted in the 100th. This same volume of distilled water was used to allow the digestion of 20 mg of compost. These solutions were filtered and volumes of 20 ml sampled. The ammonium ions in these different filtrates react with the mixture of 1 ml of phenol + 1 ml of hypochlorite + 1 ml of
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nitroprusside. The compound obtained was placed in a spectrophotometer, and the reading was made in absorbance at 630 nm. Dry matter was determined according to [26]. 10 g of compost was sampled and put in an aluminium container. The sample was then dried in an oven at 105 °C and cooled in a desiccator. The result is expressed as follows (equation 1): (1)
Where S is the percentage dry matter (% DM); A and B refer to the mass of the sample (g) after and before drying (g). Organic matter was determined according to [27] after determination of the dry matter (DM), the sample was calcined in a muffle furnace at 550 ° C. The residual material resulting from the combustion was the mineral matter (MM). The organic matter in percentage (OM (%)) was determined by calculating the difference between DM and MM (Equation 2). (2)
Pathogen bacteria: the method used for the detection of bacteria was based on membrane filtration according to the standard [28]. 5 mL of urine were transferred to a jar, then 1 mL was taken and diluted in the 100th. Regarding the feces-based compost, 20 mg were sampled and dissolved in 100 mL
of distilled water. After stirring and settling, 1 mL was sampled and filtered through sterile filter membrane (0.45 μm in diameter). After filtration, the membrane was placed under sterile conditions on petri dishes containing a solid culture medium (agar) before being incubated for 30 minutes at precise temperatures permitting the identification of the bacteria. For seeding, the culture media used varied according to the bacteria sought. ● Fecal Coliforms were searched using the "COMPASS® cc Agar". The reading was carried out
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after 18 to 24 hours of incubation at 44 ° C. Colonies of Fecal Coliforms appear in blue. ● Fecal Streptococci were identified after culture on 'Slanetz and Bartley agar'. The reading occurred after 44 ± 4 hours of incubation at 37 ° C. Colonies appear in dark roses or reds with or without a white aureole. Total Coliforms included all blue and pink or dark red colonies with or without a white aureole present in the culture media. They correspond to the bacterial load of the seeded inoculum. Taking into account the dilution rates of the samples, the number of bacteria was calculated according to equation (3). The results are expressed in Forming Colonies Unit (UFC). (3)
Where: Cs: number of bacteria in the reference volume Vs Vs: reference volume chosen to express the bacterial load N: sum of all colonies counted in the dishes from dilutions d1 and d2 n1, n2: number of boxes counted for dilutions d1 and d2 v1, v2: test volumes used for dilutions d1 and d2 d1, d2: dilutions used for the sampling v1, v2
Anaerobic sulfite-reducers (ASRs) were enumerated according to [29]. For the urine, 1 mL of urine was diluted to the 50th. Whereas for feces-based compost, 20 mg were sampled and dissolved into 50 ml of distilled water. Then after settling, 1 ml of solution was sampled. The samples were placed in an anaerobic tube containing 20 ml of agar supplemented with sulphites and iron III ammoniacal citrate. After incubation at 37° C, a black precipitate was formed from sulfites and sulfides. Each of the precipitates correspond to an ASR.
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Helminths eggs (Schistosomamansoni, Trichuristrichiuras and Ascaris lombricoïdes eggs) were determined using a method involving sodium acetate-acetic acid-formaldehyde (SAF) [30]. With regards to urine, 1 mL was sampled and diluted in the 100th. For feces-based compost, 1 g was sampled and dissolved into 100 ml of distilled water. For both solutions, a mixture of 5 ml of sodium acetate + 5 ml of acetic acid was then added in order to destroy any vegetative forms. Then, two drops of formalin were added to concentrate the eggs. These formal solutions were filtered through a filter membrane and the eggs collected. Eggs were identified according to their aspects using a microscope (10 × 40). 3 3.1
Results
Physicochemical and microbiological characteristics of the urine sample Table 1 shows the physicochemical and microbiological parameters analysed in the urine. These
results revealed that the temperature in urine sample was 27.6°C and the pH was basic (8.61). The concentration of calcium was the highest, followed by that of potassium, phosphorus, magnesium and ammonium. There were Metallic Trace Elements (MTE) in different proportions in the urine sample (Table 1). The zinc concentration was the highest, followed by that of copper, lead, cadmium and mercury. The concentration of the latter which was less than the reading threshold (
