The potential for self-sanitisation of faecal sludge by intrinsic ammonia (original) (raw)
African Journal of Environmental Science and Technology, 2014
To promote the use of eco-toilets is an alternative to the lack of sanitation and high cost of artificial fertilisers in developing countries. Human urine is the fraction of excreta containing most nitrogen, phosphorus and potassium which are essential nutrients for plant growth. The major concern related to the use of the urine as fertiliser is the possible presence of enteric pathogens. The reduction in the numbers of Escherichia coli, Enterococcus faecalis, Salmonella sp., Staphylococcus aureus, Clostridium perfringens spores during urine storage was studied in diluted and undiluted urine samples. These experimental samples were stored in ambient air and at temperatures of 25, 35 and 42°C. The initial concentration of ammoniacal nitrogen reduced from 8260 to 1070 mg/L in quarterdiluted urine (1:3), while the pH values remained stable at 8.6 (± 0.2). E. faecalis survived for 35 days in the quarter-diluted urine at 25°C. Survival times of the tested bacteria were more shortened in ammonia concentrated samples, on storage at 35, 42°C. Except C. perfringens spores, E. faecalis was the least sensitive to storage conditions as compared to S. aureus and the two Gram-negative bacteria tested. Therefore, temperature and ammonia acted synergistically to remove bacteria in the stored urine. Likewise, C. perfringens spores were the most persistent bacteria, with only 1-log 10 reduction within 100 days storage at ambient temperature. This study shows that a period of at least 30 days of undiluted urine storage at temperatures ≥ 25°C is sufficient to sanitize urine, considering only vegetative bacteria. Since urine from eco-toilets may contain other enteric organisms (viruses, protozoa, etc) appearing more persistent in external media, storage time must be lengthened for a satisfactory sanitation.
The reduction in pathogenic bacteria and Ascaris suum were determined during storage of sedimented, dewatered sewage sludge at 7, 13 and 21°C. The kinetics of Salmonella Typhimurium reduction differed over time as the initial decrease was temperature dependent while other factors influenced the survival in the later stages of storage. Temperature and reduction rate were highly correlated over time for Enterococcus spp., while the coliform bacteria showed an inconsistent reduction. A temperature of 21 °C during 214 days of storage was not enough to inactivate the Ascaris suum eggs.
Ammonia Inactivation of Ascaris Ova in Ecological Compost by Using Urine and Ash
Applied and Environmental Microbiology, 2012
Viable ova of Ascaris lumbricoides , an indicator organism for pathogens, are frequently found in feces-derived compost produced from ecological toilets, demonstrating that threshold levels of time, temperature, pH, and moisture content for pathogen inactivation are not routinely met. Previous studies have determined that NH 3 has ovicidal properties for pathogens, including Ascaris ova. This research attempted to achieve Ascaris inactivation via NH 3 under environmental conditions commonly found in ecological toilets and using materials universally available in an ecological sanitation setting, including compost (feces and sawdust), urine, and ash. Compost mixed with stored urine and ash produced the most rapid inactivation, with significant inactivation observed after 2 weeks and with a time to 99% ovum inactivation ( T 99 ) of 8 weeks. Compost mixed with fresh urine and ash achieved a T 99 of 15 weeks, after a 4-week lag phase. Both matrices had relatively high total-ammonia conc...
Water Research, 2004
The presence of helminth eggs (Ascaris eggs) in sewage sludge may constitute a sanitary risk when used as agricultural fertiliser. Sanitisation of sewage sludge can be achieved by treatment with quick lime, a process that destroys sludge pathogens in two ways: pH increase and temperature rise. Among the pathogens of epidemiological relevance, Ascaris eggs are the most resistant to liming, and, hence, may serve as indicators of hygienic quality of biosolids. This research aims at defining, between 50 C and 60 C, the time required in the case of limed sludge to obtain a product with a negligible level of viable Ascaris eggs. To achieve this objective, investigations on inactivation kinetics of Ascaris eggs were conducted in the following products: contaminated milk of lime; naturally contaminated sludge treated with slaked lime and heat; naturally contaminated sludge treated with quick lime; and sludge treated at full scale with quick lime. For the inactivation kinetics where a negligible level of Ascaris eggs was reached, the inactivation threshold was determined. Depending on the experimental situation, the inactivation threshold period was found to fluctuate between 5 and 75 min at 55 C and between 1 and 8 min at 60 C.
Treatment Technologies for Human Faeces and Urine
2009
This thesis examines simple, cheap, environmentally friendly and resource efficient technologies for the treatment of source-separated human faeces and urine to enable safe recycling of their plant nutrients for plant production in developing countries. Composting of faeces-to-food waste (F:FW) in wet weight mix ratios of 1:0, 3:1 and 1:1 was studied in 78 L reactors insulated by 25 mm styrofoam; and of F:FW in wet volume/weight ratios of 1:0, 1:1 and 1:3 in 216 L reactors insulated by 75 mm styrofoam. At both scales, composting without insulation produced temperatures that differed from the ambient by 15 °C. A sanitised compost product was produced when the temperature was maintained above sanitising levels (>50 °C) for a sufficiently long time (at least 2 weeks). High moisture levels (>60%) led to low pH (<6), which impeded composting and the attainment of sanitising temperatures. Incineration of well prepared source-separated faeces with ash as cover material produced high temperatures (800-1000 °C). This process decreased the organic matter, total N and plant-available P by 70->90%. Mass decrease was 15-36% due to high ash content of the incoming material. Incinerating faeces/ash mixtures with DM<90% resulted in a strong smell that lessened when DM was higher. The ash produced by incineration can be used as cover material for faeces during toilet use, which is advantageous in urban areas of developing countries where access to ash is limited. In urine treatment, a breakpoint concentration of ammonia was found at approximately 40 mM NH 3 (e.g. 2.1 g NH 3-N L-1 and pH 8.9 at 24 °C), below which all studied organisms, except Salmonella Typhimurium (S. Typhimurium), persisted considerably longer irrespective of treatment temperature, showing that urine dilution rate is highly important for pathogen inactivation. The time to no detection in urine stored in the sun (Uganda; mean temperatureramplitude 24±7.5 °C, NH 4-N of 4±1.5 mg L-1 and pH 9) for E. coli, Salmonella and Ascaris suum was 11 hours, 14 hours and 40 days respectively. Under similar conditions, Enterococcus spp. reached non-detection levels in 50 days, while the phages studied persisted considerably longer. The t 90 for MS2, ĭx 174 and S. Typhimurium 28B was 8.2, 37 and 55 days respectively. Fluctuating temperatures in combination with ammonia were shown to inactivate pathogens in urine faster than the same average steady temperature.
Inactivation of fecal bacteria in sewage sludge by alkaline treatment
Bioresource Technology, 1994
The efficacy of aqueous alkaline solutions to purify wastewater sludges destined for agricultural land application was evaluated. Some fecal bacteria were tested as sanitary-quality indices, these included fecal streptococci, which were found to be more resistant than coliforms. Hygienization within 10 days was obtained with ammonium hydrate at a dose that brought the pH of the sludge to about 10. Such a treatment was effective above IO*C. The total-bacteria number dropped only slightly, so that the sludge retained its potential biological activity. The efficacy of the treatment with NH40H was better than that observed with KOH.
The Effect of Physical Factors on Fecal Coliform Viability Rate in Sewage Sludge
Journal of Geoscience and Environment Protection, 2014
Experiments were conducted on the survival rate of fecal coliform after spreading the sewage sludge for desiccation on sludge beds in an open field throughout the year. The ambient temperature, humidity, sunlight intensity and solar radiation were measured during the period of sludge desiccation. The maximum average temperature, sunlight intensity and solar radiation were recorded throughout the year. During May and August the minimum microbial counts were recorded after four weeks of sludge desiccation. Relative humidity did not have significant effect on survival rate. The minimum microbial counts were taken after four weeks of sludge drying. When the sludge was mixed with three different media, the maximum count of fecal coliform was presented when soil mixed with sludge and irrigated with treated sewage effluent (TSE). When soil mixed with sludge irrigated with well water, the number of fecal coliform count dropped significantly. The minimum count occurred when compost was used instead of sludge. This was a clear indication that the source of contamination was from sludge and was mostly contributed by the TSE irrigation. The use of dried sludge after four weeks of treatment had the lowest fecal coliform count and was safe to be used as fertilizer for farming. Oman is located in a semi-equatorial belt with arid environmental conditions which are ideal for elimination of microbial pathogens. Thus, sludge desiccation in such environmental conditions, specifically during the hot months of the year, is perfect for such practice.
Monitoring of bacterial and parasitological contamination during various treatment of sludge
Water Research, 2001
Abstract}Wastewater treatment results in the production of large quantities of sludge. Agricultural use is an interesting alternative provided that the health risks are taken into account. In France, a decree (1998) defines ''sanitized'' sludge as sludge that has been treated so that pathogens (Salmonella, enteroviruses, viable nematode eggs) are no longer detectable. The aim of this study was to determine the impact of various sludge treatments on 2 types of pathogens (Salmonella and nematode eggs). We also assessed the levels of micro-organisms that indicate faecal contamination (E. coli, Enterococci, sulfite-reducing anaerobes spores). Various treatment processes were analyzed: 4 biological, 3 chemical, 1 heat , 2 storage and 4 sampling campaigns were carried out. Concerning the parasitological contamination of sludge at the entrance of all sites, concentrations of total nematode eggs and viable nematode eggs were highly heterogeneous (respectively, from 2 to 53 eggs/10 g DM and from 2 to 45 eggs/10 g DM) with viable eggs present in all samples. The total concentration of nematode eggs in the sludge was not greatly affected by treatment or storage, and was in the range 51-66 eggs/10 g DM. However, the situation was different for mean viable egg counts. For four treatments, no viable eggs were detected. Mesophilic processes are inefficient at eliminating viable nematode eggs. Salmonella were systematically detected in all sludge samples at the entry to the station, except for limed sludge intended for storage. At the end of four treatments Salmonella had been totally eliminated. For the fecal contamination indicators, the largest decrease in E. coli contamination was observed following liming and after thermophilic treatment. The mesophilic treatments resulted in very small decreases in contamination. A similar pattern was observed with Enterococci. For the spores of sulfite-reducing anaerobe bacteria, with the exception of heat treatment, which reduced contamination by 3.2 log units, the maximum decrease in contamination was 1.7 log. For storage of sludge, E. coli and Enterococci levels had decreased at first but then increased between 6 and 8 months of storage. #
Comparison of Composing and Urea Treatment for Sanitising of Faecal Matter
ABSTRACT The second most nutrient-containing fraction from households, faecal matter, is highly likely to con- tain pathogens and thus requires some form of sanitising treatment. Two alternatives for this treatment, composting and urea treatment, were evaluated and compared to storage for 50 days. Thermal composting of faeces together with food waste (35% DM) resulted in a treatment temperature of over 65°C for 3 con- secutive days. However, not all the material maintained this high temperature, i.e. close to the inlet of air. In the urea treatment, the added 3%N-NH3 increased the pH in the faecal material (10% DM) from 8 to >9 within one hour of application ,and resulted in a ,good reduction in the ,indicator organisms ,for bacteria (Salmonella and E-coli D r < 0.7 days), viruses (D r
The present study investigated the optimum time and temperature for inactivation of bacteria and parasites in cow dung and pit faecal sludge, a forthcoming fertilizer. Samples were collected from different areas of Bangladesh and were examined through modified centrifugal flotation and conventional culture techniques to isolate parasites and bacteria respectively. A cow dung sample from Gopalganj and a pit sample from Dohar that were found to be the most contaminated among the samples tested were heated to annihilate the pathogens present there. After 30 min of exposure at 60°C, all bacteria lost their ability to grow on culture media except enterococci. Among the parasites found in the pit sample, Entamoeba histolytica was the least heat resistant, which was killed at 60°C within 30 min followed by Ancylostoma duodenale larva, Strongyloides stercoralis larva, Trichuris trichiura, Ancylostoma duodenale eggs and Strongyloides stercoralis egg. Ascaris lumbricoides and Hymenolepis nana were the most resistant to heat, inactivated at 75°C within 15 min. In cow dung, Paramphistomum was the most resistant, became inactivated at 65°C within 60 min whereas Haemonchus at 65°C within 30 min. The study findings showed the best time dependent temperature to deactivate the pathogens present in faecal sludge in Bangladesh context.
Inactivation of Ascaris Suum by Ammonia in Feces Simulating the Parameters of the Solar Toilet
2012
Ricardo Izurieta, who offered me knowledge and support throughout my entire academic program and research. I thank my committee members and Dr. Bjorn Vinneras for their insight and guidance. I would also like to thank Dr. Lakshminarayan Rajaram for his assistance in data management and statistical analysis. I acknowledge the support provided by the entire Department of Global Health: they created the working conditions that were essential to the accomplishment of this goal. Very special thanks to my colleagues who helped me in the lab. My dearest friend and roommate Ellen McCreedy, she was always there supporting and cheering me up and stood by me through the good and bad times. I will always appreciate her many hours of proofreading and her belief in me. My boyfriend Max J. Moreno, I am grateful for his encouragement, understanding, patience and love in the past few years. Most importantly, I thank my family, for their faith in me and allowing me to be as ambitious as I wanted. It was under their watchful eye that I gained so much drive and an ability to tackle challenges head on. i TABLE OF CONTENTS LIST OF TABLES .
Hygienization of sludge through anaerobic digestion at 35, 55 and 60 °C
Water Science & Technology, 2013
Legislation in Sweden and the European Union concerning the use of sewage sludge in agriculture is under revision and future concentration limits for pathogens in treated sludge are likely to be expected. The aim of this study was to evaluate the hygienization of Salmonella, Escherichia coli, Enterococcus and Clostridium perfringens through continuous anaerobic digestion at 35, 55 or 60 °C, as well as to investigate process stability and methane production at 60 °C. The results indicated that digestion at 55 or 60 °C with a minimum exposure time of 2 h resulted in good reduction of Salmonella, E. coli and Enterococcus and that anaerobic digestion could thus be used to reach the concentration limits suggested for the EU, as well as Sweden. Furthermore, stable continuous anaerobic digestion of sludge was achieved at 60 °C, albeit with 10% less methane production compared to digestion at 35 and 55 °C.
Microbiological quality of sewage sludge after digestion treatment: A pilot scale case of study
Journal of Cleaner Production, 2020
In the frame of the water circular economy, the reuse of the treated sewage sludge supposes a good action. Nevertheless, the reuse might suppose a human health risk because of the presence of pathogen germs, concentrated in the generated sludge during urban wastewater treatment. For this reason, sludge treatments, conventional or advanced, should be focused on the reduction of fermentation capacity and microorganisms presence. This research assess the microbiological quality of the treated sludge, based on the use of faecal pollution indicators such as total coliforms, Escherichia coli, Enterococcus sp., Pseudomonas sp., Staphylococcus aureus and total mesophilic bacteria, after the application of different digestion treatments, and their final aptitude to be reused. Three different pilot scale plants were used: two anaerobic digestion plants with a volume of 2.75 m 3 working in mesophilic (35-37 C) and thermophilic (55-57 C) conditions, and hydraulic retention times (HRT) ranging from 5 to 20 days; and a autothermal thermophilic aerobic digestion plant (ATAD) with a volume of treatment of 3.9 m 3 working at 55-57 C for an HRT of 5e15 days. The raw sludge to be treated came from a full-operative WWTP located in the region of Navarra (Spain), laid within Ebro River Basin. It was concluded that both treatments studied obeyed the current European legislation in therms of E. coli concentration and absence of Salmonella spp., being available for agricultural purposes. Considering other microbiological parameters, the anaerobic thermophilic treatment had the best conditions to reduce the Enterococcus sp. concentrations and the aerobic thermophilic treatment was the best one reducing E. coli, being non-significant the influence of HRT to microbial reduction. For this reason, it is strongly recommended the use of both faecal indicators to assess the microbial quality of the treated sludge.
Factors Affecting Disinfection and Stabilization of Sewage Sludge
Proceedings of the …, 2006
Effective disinfection and stabilization of sewage sludge prior to land application is essential to not only protect human health, but also to convince the public of its benefits and safety. A basic understanding of the key factors involved in producing a stable biosolid product is a necessary component to ensuring that effective disinfection and stabilization are achieved. Key stressors used to treat sewage sludge, both traditional and some emerging, are discussed including physical, chemical, and biological stressors. Factors that affect a stressor's effectiveness are included where information is available. Examples of methods that employ each stressor are presented.
International Journal of …, 2012
The aim of study was to estimate the sanitization effectiveness of the sludge solar drying process carried out on technical scale in Poland based on the inactivation of bacteria and parasite eggs. Sewage sludge samples inoculated with Escherichia coli, Salmonella Senftenberg W 775 and enterococci and perlon bags containing Ascaris suum eggs were placed inside the carriers fixed in the dried sludge pile and on the shovels and frame of the sludge turner. The number of reisolated microorganisms was determined with MPN method and the percentage of invasive A. suum eggs-with the microscope counting. On the basis of regression equations, the theoretical survivability and elimination rate of bacteria and parasite eggs were calculated. Experiment showed low hygienization efficiency of solar drying method. The theoretical survival time was 46-104 days in summer and 90-98 days in winter for S. Senftenberg W 775 and, respectively 42-55 and 71-148 days for E. coli, depending on the carriers location. Enterococci were able to survive for 52-168 days in summer and in winter its number increased. The decrease in the percentage of invasive A. suum eggs was almost not observed. Results indicated that solar drying is a technology, which does not guarantee biosafety of product.
International journal of environmental research and public health, 2015
In this research, three faecal sludge sanitizing methods-lactic acid fermentation, urea treatment and lime treatment-were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m³ of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated ...
Removal efficiency of faecal coliforms and helminth eggs was evaluated in a small wastewater treatment plant (WWTP) serving a population of 1,000. This system was formed by the association in series of a UASB reactor and four submerged aerated biofilters. The density of faecal coliforms and the count of helminth eggs were estimated in the liquid and solid phases of the system. Two different methods of disinfecting sludge were investigated: (a) chemical treatment with lime and (b) a physical treatment by pasteurisation. As expected, the association UASB + BF was very efficient at removal of helminth eggs from the final tertiary effluent, but coliforms were still present at high densities. Lime treatment and pasteurisation of sludge were very effective methods of disinfection and produced a sludge safe for final disposal.
Hygienization performances of innovative sludge treatment solutions to assure safe land spreading
2014
The present research aims at the evaluation of the hygienization performances of innovative sludge treatment processes applied for the separated treatment of secondary sludge. Namely, two digestion pretreatments (sonication and thermal hydrolysis) and two sequential biological processes (mesophilic/thermophilic and anaerobic/aerobic digestion) were compared to the mesophilic (MAD) and thermophilic anaerobic digestion (TAD). Microbial indicators (Escherichia coli, somatic coliphages and Clostridium perfringens spores) and pathogens (Salmonella and enteroviruses), which show different resistances to treatment processes, were monitored in untreated and treated sludge. Overall, microbial load in secondary sludge was shown to be similar or lower than previously reported in literature for mixed sludge. Notably, the anaerobic/aerobic digestion process increased the removal of E. coli and somatic coliphages compared to the simple MAD and always achieved the hygienization requirement (2-logunit removal of E. coli) proposed by EU Commission in the 3rd Working Document on sludge for the use of treated sludges in agriculture with restriction on their application. The microbial quality limits for the unrestricted use of sludge in agriculture (no Salmonella in 50 g wet weight (WW) and E. coli <500 CFU/g) were always met when thermal digestion or pretreatment was applied; however, the required removal level (6-log-unit removal of E. coli) could not be assessed due to the low level of this microorganism in raw sludge. Observed levels of indicator removal showed a higher resistance of viral particles to thermal treatment compared with bacterial cells and confirmed the suitability of somatic coliphages as indicators in thermal treatment processes.