The potential for self-sanitisation of faecal sludge by intrinsic ammonia (original) (raw)
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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. #