The potential for self-sanitisation of faecal sludge by intrinsic ammonia

Faecal sludge has the potential to be used as a sustainable fertiliser in agriculture, but the sludge must be sanitised due to its content of pathogenic microorganisms. The intrinsic ammonia from the urine may be sufficient for sanitisation of the sludge if it is not too diluted by flush water or lost by ventilation. To evaluate the potential for this sanitisation method, inactivation of Enterococcus faecalis, Salmonella typhimurium and Ascaris suum eggs during treatment were assessed. The inactivation was studied at different storage temperatures (10–28 °C) and in several sludge mixes with different contents of urine, faeces and flush water, and with ammonia concentrations from 40 to 400 mM. All pathogens were inactivated by the ammonia, and ascaris eggs were the most persistent. Lower flush water volume and higher urine content favoured inactivation, mainly due to increased uncharged ammonia (NH₃) concentration. The lag phase in ascaris inactivation was shortened by increasing temperature and NH₃ concentration, while post-lag phase inactivation was not influenced by NH₃ concentration. Faecal sludge can be sanitised by airtight storage without the use of additives when flush water volumes are sufficiently low. For temperatures of 23–28 °C, a 3 log reduction of ascaris egg viability can be achieved within 1–6 months depending on ammonia concentration and temperature.     

Solid-liquid separation of faecal sludge using drying beds in Ghana: implications for nutrient recycling in urban agriculture

This study investigated the possibility of recycling nutrients in human excreta and municipal solid waste for use in agriculture. It reports on the use of drying beds in separating solid and liquid fractions of faecal sludge (FS) so that the solids can be co-composted and the organic matter and part of the nutrients captured for urban agriculture. Sludge influent onto drying beds, percolate effluent, and dewatered sludge (biosolids) were monitored over eight loading cycles in 2002. The unplanted drying beds were made of 15 cm of sand (0.2-0.6mm diameter) and 25 cm gravel (10 and 19 mm diameter). The loading rate of sludge ranged from 196 to 321 kg total solids (TS) /m(2)y. Biosolids with TS 20% were obtained after an average drying time of 2 weeks. The drying beds retained 80% of solids and 100% of helminth eggs. The biosolids had average organic matter content of 61%; hence, allowing for co-composting with biodegradable organic solid waste for hygienisation. The process is being investigated further to attain higher efficiency and reliability.     

The effects of temperature, pH, and ammonia concentration on the inactivation of Ascaris eggs in sewage sludge

The reported inactivation of Ascaris eggs during alkaline sludge stabilization is highly variable. The objective of our research was to better understand the sources of this variability by quantifying the effects of temperature, pH, and ammonia concentration on the inactivation of indigenous Ascaris eggs in wastewater sludge. Primary sludge was supplemented with ammonia (0, 1000, and 5000mg/l NH(3)-N) and Ca(OH)(2) and incubated in sealed bottles across the range of temperatures (20, 30, 40, and 50 degrees C) and pH (7 and 12) that may be encountered during treatment. Changes in egg viability over time were fit to a two-parameter kinetic model (shoulder and first-order region); to compare treatment conditions, the time for 99% inactivation (t(99)) was also calculated. Each 10 degrees C increase in temperature caused a significant decrease in t(99) at every pH and ammonia concentration tested. At 50 degrees C, the effect of temperature was dominant, such that no effect of pH or ammonia was observed. At 30 and 40 degrees C, raising the pH from 7 to 12 decreased t(99), but at 20 degrees C no pH effect was seen over 80 d (very little inactivation occurred). At 20, 30, and 40 degrees C, the addition of ammonia dramatically decreased t(99). The effect of pH could not be completely separated from that of ammonia, as the unamended sludge samples contained 100-200mg/l indigenous ammonia. Because temperature, pH, and ammonia all contributed to Ascaris egg inactivation, it is essential that these parameters are measured and accounted for when assessing the effectiveness of alkaline stabilization. Furthermore, inactivation by ammonia could be exploited to improve the effectiveness of alkaline sludge stabilization.     

Quantification of pathogenic microorganisms and microbial indicators in three wastewater reclamation and managed aquifer recharge facilities in Europe

Managed Aquifer Recharge (MAR) is becoming an attractive option for water storage in water reuse processes as it provides an additional treatment barrier to improve recharged water quality and buffers seasonal variations of water supply and demand. To achieve a better understanding about the level of pathogenic microorganisms and their relation with microbial indicators in these systems, five waterborne pathogens and four microbial indicators were monitored over one year in three European MAR sites operated with reclaimed wastewater. Giardia and Cryptosporidium (oo)cysts were found in 63.2 and 36.7% of the samples respectively. Salmonella spp. and helminth eggs were more rarely detected (16.3% and 12.5% of the samples respectively) and Campylobacter cells were only found in 2% of samples. At the Belgian site advanced tertiary treatment technology prior to soil aquifer treatment (SAT) produced effluent of drinking water quality, with no presence of the analysed pathogens. At the Spanish and Italian sites amelioration of microbiological water quality was observed between the MAR injectant and the recovered water. In particular Giardia levels decreased from 0.24-6.14 cysts/L to 0-0.01 cysts/L and from 0.4-6.2 cysts/L to 0-0.07 cysts/L in the Spanish and Italian sites respectively. Salmonella gene copies and Giardia cysts were however found in the water for final use and/or the recovered groundwater water at the two sites. Significant positive Spearman correlations (p < 0.05, r_s range: 0.45-0.95) were obtained, in all the three sites, between Giardia cysts and the most resistant microbial markers, Clostridium spores and bacteriophages.     

Stability and maturity of thickened wastewater sludge treated in pilot-scale sludge treatment wetlands

Thickened wastewater activated sludge was treated in 13 pilot-scale sludge treatment wetlands of various configurations that operated continuously for three years in North Greece. Sludge was loaded for approximately 2.5 years, and the beds were left to rest for the remaining period. Three different sludge loading rates were used that represented three different population equivalents. Residual sludge stability and maturity were monitored for the last year. Sludge was regularly sampled and microbial respiration activity indices were measured via a static respiration assay. The phytotoxicity of sludge was quantified via a seed germination bioassay. Measurements of total solids, organic matter, total coliforms, pH and electrical conductivity were also made. According to microbial respiration activity measurements, the sludge end-product was classified as stable. The germination index of the final product exceeded 100% in most wetland units, while final pH values were approximately 6.5. The presence of plants positively affected the stability and maturity of the residual sludge end-product. Passive aeration did not significantly affect the quality of the residual sludge, while the addition of chromium at high concentrations hindered the sludge decomposition process. Conclusively, sludge treatment wetlands can be successfully used, not only to dewater, but also to stabilize and mature wastewater sludge after approximately a four-month resting phase.     

Sourcing faecal pollution: a combination of library-dependent and library-independent methods to identify human faecal pollution in non-sewered catchments

Library-dependent (LD) (biochemical fingerprinting of Escherichia coli and enterococci) and library-independent (LI) (PCR detection of human-specific biomarkers) methods were used to detect human faecal pollution in three non-sewered catchments. In all, 550 E. coli isolates and 700 enterococci isolates were biochemically fingerprinted from 18 water samples and compared with metabolic fingerprint libraries of 4508 E. coli and 4833 enterococci isolates. E. coli fingerprints identified human unique biochemical phenotypes (BPTs) in nine out of 18 water samples; similarly, enterococci fingerprints identified human faecal pollution in 10 water samples. Seven samples were tested by PCR for the detection of biomarkers. Human-specific HF134 Bacteroides and enterococci surface protein (esp) biomarkers were detected in five samples. Four samples were also positive for HF183 Bacteroides biomarker. The combination of biomarkers detected human faecal pollution in six out of seven water samples. Of the seven samples analysed for both the indicators/markers, at least one indicator/marker was detected in every sample. Four of the seven PCR-positive samples were also positive for one of the human-specific E. coli or enterococci BPTs. The results indicated human faecal pollution in the studied sub-catchments after storm events. LD and LI methods used in this study complimented each other and provided additional information regarding the polluting sources when one method failed to detect human faecal pollution. Therefore, it is recommended that a combination of methods should be used to identify the source(s) of faecal pollution where possible.     

Precision and accuracy of an assay for detecting Ascaris eggs in various biosolid matrices

This paper presents quality assurance data and quality control data on the recovery of Ascaris suum eggs from various biosolid matrices: acid-treated, alkaline-treated, amended-soil blended, and lagoon stored biosolids. Over a period of years, the same procedure, the "Tulane Method," was performed on different matrices, and in this work, the data collected on the recovery of the eggs from the different matrices is examined and compared. The egg recoveries are discussed in terms of precision (the comparison of the recovery of eggs from a sample processed in duplicate) and in terms of accuracy (the percentage of eggs recovered from a sample to which eggs were added at the beginning of the extraction procedure). This form of quality analysis/control is typically called the "Split/Spike" method. This method of biosolid processing for helminth egg recovery had an overall accuracy of about 60% or greater and a percent variation from the mean density (an indirect method of assessing precision) of only 3-35%.     

Development of microbial and chemical MST tools to identify the origin of the faecal pollution in bathing and shellfish harvesting waters in France

The microbiological quality of coastal or river waters can be affected by faecal pollution from human or animal sources. An efficient MST (Microbial Source Tracking) toolbox consisting of several host-specific markers would therefore be valuable for identifying the origin of the faecal pollution in the environment and thus for effective resource management and remediation. In this multidisciplinary study, after having tested some MST markers on faecal samples, we compared a selection of 17 parameters corresponding to chemical (steroid ratios, caffeine, and synthetic compounds), bacterial (host-specific Bacteroidales, Lactobacillus amylovorus and Bifidobacterium adolescentis) and viral (genotypes I-IV of F-specific bacteriophages, FRNAPH) markers on environmental water samples (n = 33; wastewater, runoff and river waters) with variable Escherichia coli concentrations. Eleven microbial and chemical parameters were finally chosen for our MST toolbox, based on their specificity for particular pollution sources represented by our samples and their detection in river waters impacted by human or animal pollution; these were: the human-specific chemical compounds caffeine, TCEP (tri(2-chloroethyl)phosphate) and benzophenone; the ratios of sitostanol/coprostanol and coprostanol/(coprostanol+24-ethylcopstanol); real-time PCR (Polymerase Chain Reaction) human-specific (HF183 and B. adolescentis), pig-specific (Pig-2-Bac and L. amylovorus) and ruminant-specific (Rum-2-Bac) markers; and human FRNAPH genogroup II.     

Persistence of microbial and chemical pig manure markers as compared to faecal indicator bacteria survival in freshwater and seawater microcosms

Natural seawater and freshwater microcosms inoculated with pig manure were set up to determine the persistence of pig faecal microbial and chemical markers in these two types of surface water. The concentrations of Lactobacillus amylovorus, the Bacteroidales Pig-2-Bac 16S rRNA genetic marker, five stanols and the evolution of two ratios of stanols, R₁ (coprostanol to the sum of coprostanol and 24-ethylcoprostanol) and R₂ (sitostanol to coprostanol) were analyzed during two months along with the concentration of Faecal Indicator Bacteria (FIB). Pig manure was inoculated to unfiltered water microcosms incubated aerobically at 18 °C in the dark. The faecal contamination load represented by the concentrations of culturable Escherichia coli and/or enterococci remained for two months in the freshwater and seawater microcosms water column. These concentrations followed a biphasic decay pattern with a 97% reduction of the initial amount during a first rapid phase (<6 days) and a remaining proportion undergoing a slower or null second decline. The L. amylovorus marker and five stanols persisted as long as the indicators in both treatments. The Pig-2-Bac marker persisted 20 and 27 days in seawater and freshwater, respectively. The ratios R₁ and R₂ were in the range specific to pig manure until day 6 in both types of water. These results indicate that Pig-2-Bac, L. amylovorus and stanol ratios might be used in combination to complement FIB testing to determine the pig source of fecal pollution. However, stanol ratios are to be used when the time point of the discharge is known.     

The application of a recently isolated strain of Bacteroides (GB-124) to identify human sources of faecal pollution in a temperate river catchment

Recent work has suggested that bacteriophages infecting Bacteroides are a potential tool for faecal source tracking, but that different host strains may be needed for different geographic areas. This study used a recently identified strain of Bacteroides (GB-124) to detect human sources of faecal pollution in a river catchment in southeast England (UK). A total of 306 river water, municipal wastewater and animal samples were obtained over a 16-month period. Bacteriophages capable of infecting GB-124 were present in all municipal wastewaters but were not detected in faecal samples from animals, and were detected at significantly lower levels (P< 0.001) in river waters directly downstream of a dairy farm. This last observation was despite the presence of high levels of faecal indicator bacteria at this site. The study suggests that GB-124 appears to be specific to human faeces. As such it may represent an effective and low-cost method of faecal source identification.     

Probability of detecting and quantifying faecal contaminations of drinking water by periodically sampling for E. coli: a simulation model study

Drinking water supply companies monitor the presence of Escherichia coli in drinking water to verify the effectiveness of measures that prevent faecal contamination of drinking water. Data are lacking, however, on the sensitivity of the monitoring programmes, as designed under the EU Drinking Water Directive. In this study, the sensitivity of such a monitoring programme was evaluated by hydraulic model simulations of contamination events and calculations of the detection probability of the actual sampling programme of 2002. In the hydraulic model simulations of 16-h periods of 1l h(-1) ingress of untreated domestic sewage, the spread of the contamination through the network and the E. coli concentration dynamics were calculated. The results show that when large parts of the sewage reach reservoirs, e.g. when they originate from the treatment plant or a trunk main, mean detection probabilities are 55-65%. When the contamination does not reach any of the reservoirs, however, the detection probability varies from 0% (when no sampling site is reached) to 13% (when multiple sites are reached). Mean detection probabilities of nine simulated ingress incidents in mains are 5.5% with an SD of 6.5%. In reality, these detection probabilities are probably lower as the study assumed no inactivation or clustering of E. coli, 100% recovery efficiency of the E. coli detection methods and immediate mixing of contaminations in mains and reservoirs. The described method provides a starting point for automated evaluations and optimisations of sampling programmes.     

Influence of physicochemical and operational parameters on Nitrobacter and Nitrospira communities in an aerobic activated sludge bioreactor

To understand how to optimize performance of a partially nitrifying plant, the dynamics of Nitrospira and Nitrobacter abundance were studied over a 1 year period using quantitative polymerase chain reaction (qPCR) and their relative contributions to nitrite oxidation assessed including the affects of temperature and dissolved oxygen (DO). Correlation coefficients linking shifts in the community composition of nitrite-oxidizing bacteria (NOB) to operational or environmental variables indicated Nitrospira was significantly and negatively correlated to nitrite concentrations (r = −0.45, P < 0.01) and DO (r = −0.46, P < 0.01), while temperature showed a strong positive correlation (r = 0.59, P < 0.0001). However, the Nitrobacter portion of the total NOB populations showed a positive correlations with DO (r = 0.38, P < 0.01) and hydraulic retention time (HRT) (r = 0.33, P < 0.05), as well as being negatively correlated with temperature (r = −0.49, P < 0.001) suggesting specific niche adaptations within the NOB community. Nitrospira was dominant being better adapted to the low DO and shorter sludge retention times (SRT) of this plant, while Nitrobacter increased in abundance during the winter months, when temperatures were lower and DO concentrations higher. Principal component analysis (PCA) results supported these findings by the close proximity of Nitrospira and temperature biplots of PC1 and PC2 as well as grouping Nitrobacter, NO₂⁻-N, HRT, and DO in the loadings together. The clustering of samples from specific dates also exhibited a strong seasonality.     

Relationships between human adenoviruses and faecal indicator organisms in European recreational waters

Human adenoviruses (HAdV) may be implicated in some disease outbreaks associated with recreational water exposures, typically in swimming pools. Modern molecular methods can be used to detect HAdV in environmental water samples. During the EU FP6 Project VIROBATHE a database of over 290 HAdV analyses with corresponding faecal indicator organism (FIO) determinations was gathered and used to explore statistical associations between HAdV and FIO results. The FIOs measured were Escherichia coli, intestinal enterococci and somatic coliphage. Statistically significant trends of increasing proportions of HAdV-positive results in categories of increasing FIO concentration were found in freshwater but not seawater samples. The analysis of these trends in freshwater samples was refined, the trends remaining statistically significant when using categories of 0.5 log₁₀ intervals of FIO concentration. Logistic regression models were then developed to predict the probability of a HAdV-positive outcome from FIO concentration. Potential applications of these models to predict the probability of HAdV-positive outcomes from routine FIO determinations used to describe recreational water quality exposures and to classify recreational water quality are discussed.     

Biodegradation of sulfamethazine by Trametes versicolor: Removal from sewage sludge and identification of intermediate products by UPLC-QqTOF-MS

Degradation of the sulfonamide sulfamethazine (SMZ) by the white-rot fungus Trametes versicolor was assessed. Elimination was achieved to nearly undetectable levels after 20 h in liquid medium when SMZ was added at 9 mg L^− 1. Experiments with purified laccase and laccase-mediators resulted in almost complete removal. On the other hand, inhibition of SMZ degradation was observed when piperonilbutoxide, a cytochrome P450-inhibitor, was added to the fungal cultures. UPLC-QqTOF-MS analysis allowed the identification and confirmation of 4 different SMZ degradation intermediates produced by fungal cultures or purified laccase: desulfo-SMZ, N⁴-formyl-SMZ, N⁴-hydroxy-SMZ and desamino-SMZ; nonetheless SMZ mineralization was not demonstrated with the isotopically labeled sulfamethazine-phenyl-¹³C₆ after 7 days. Inoculation of T. versicolor to sterilized sewage sludge in solid-phase systems showed complete elimination of SMZ and also of other sulfonamides (sulfapyridine, sulfathiazole) at real environmental concentrations, making this fungus an interesting candidate for further remediation research.     

Use of Moringa oleifera seed extracts to reduce helminth egg numbers and turbidity in irrigation water

Water from wastewater-polluted streams and dug-outs is the most commonly used water source for irrigation in urban farming in Ghana, but helminth parasite eggs in the water represent health risks when used for crop production. Conventional water treatment is expensive, requires advanced technology and often breaks down in less developed countries so low cost interventions are needed. Field and laboratory based trials were carried out in order to investigate the effect of the natural coagulant Moringa oleifera (MO) seed extracts in reducing helminh eggs and turbidity in irrigation water, turbid water, wastewater and tap water. In medium to high turbid water MO extracts were effective in reducing the number of helminth eggs by 94-99.5% to 1-2 eggs per litre and the turbidity to 7-11 NTU which is an 85-96% reduction. MO is readily available in many tropical countries and can be used by farmers to treat high turbid water for irrigation, however, additional improvements of water quality, e.g. by sand filtration, is suggested to meet the guideline value of ≤1 helminth egg per litre and a turbidity of ≤2 NTU as recommended by the World Health Organization and the U.S. Environmental Protection Agency for water intended for irrigation. A positive correlation was established between reduction in turbidity and helminth eggs in irrigation water, turbid water and wastewater treated with MO. This indicates that helminth eggs attach to suspended particles and/or flocs facilitated by MO in the water, and that turbidity and helminth eggs are reduced with the settling flocs. However, more experiments with water samples containing naturally occurring helminth eggs are needed to establish whether turbidity can be used as a proxy for helminth eggs.     

Bacterial pathogen incidences in sludge from Swedish sewage treatment plants

This study surveyed the presence of bacterial pathogens in eight Swedish sewage treatment plants (STPs), with four different treatment methods, focusing on detection of zoonotic bacteria in raw and treated sludge. Salmonella spp., Listeria monocytogenes, Campylobacter coli and jejuni, Escherichia coli O157 and indicator bacteria were investigated. Samplings were performed from July 2000 to June 2002, resulting in 64 raw sludge samples and 69 treated sludge samples. The samples from raw sludge (67%) and treated sludge (55%) were positive for Salmonella; 49 different serotypes were detected. Restriction enzyme analysis and pulsed field gel electrophoresis of Salmonella serotypes indicated that Salmonella persists in STPs and that there is a continuous supply of new strains. There are differences in treatment methods concerning the reduction of pathogens and indicator bacteria. If spread on arable land, sludge increases the environmental load of pathogens; this increases the risk for spreading diseases to people and animals.     

Comparison of the efficacy of an existing versus a locally developed metabolic fingerprint database to identify non-point sources of faecal contamination in a coastal lake

A comparison of the efficacy of an existing large metabolic fingerprint database of enterococci and Escherichia coli with a locally developed database was undertaken to identify the sources of faecal contamination in a coastal lake, in southeast Qld., Australia. The local database comprised of 776 enterococci and 780 E. coli isolates from six host groups. In all, 189 enterococci and 245 E. coli biochemical phenotypes (BPTs) were found, of which 118 and 137 BPTs were unique (UQ) to host groups. The existing database comprised of 295 enterococci UQ-BPTs and 273 E. coli UQ-BPTs from 10 host groups. The representativeness and the stability of the existing database were assessed by comparing with isolates that were external to the database. In all, 197 enterococci BPTs and 179 E. coli BPTs were found in water samples. The existing database was able to identify 62.4% of enterococci BPTs and 64.8% of E. coli BPTs as human and animal sources. The results indicated that a representative database developed from a catchment can be used to predict the sources of faecal contamination in another catchment with similar landuse features within the same geographical area. However, the representativeness and the stability of the database should be evaluated prior to its application in such investigation.     

Detection and genotyping of Giardia duodenalis in wastewater: relation between assemblages and faecal contamination origin

Among the seven assemblages identified in Giardia duodenalis species, only assemblages A and B infect humans and numerous other mammals as well. On the other hand, assemblage E is considered to be host restricted to livestock. The aim of the present study was to compare the presence of G. duodenalis assemblages A, B and E in wastewater samples from two municipal treatment plants (n=24) and one slaughterhouse (n=12). Thus, PCR assays targeting the tpi gene were developed to detect specifically these three G. duodenalis assemblages. Assemblages A and B were detected in urban wastewater with a predominance of assemblage A, especially for one treatment plant. Concerning slaughterhouse wastewater, assemblage A was found in 58% of the samples, whereas assemblage B was not detected. Assemblage E was not detected in urban wastewater, but was found in 92% of the samples from slaughterhouse. Thus, combination of assemblages A and B seemed to indicate a human contamination origin, while combination of assemblages A and E appeared to correspond to a livestock contamination origin.     

Enhanced settleability and dewaterability of fungal treated domestic wastewater sludge by liquid state bioconversion process

A study was conducted to evaluate the settleability and dewaterability of fungal treated and untreated sludge using liquid state bioconversion process. The fungal mixed culture of Aspergillus niger and Penicillium corylophilum was used for fungal pretreatment of wastewater sludge. The fungal strains immobilized/entrapped on sludge particles with the formation of pellets and enhanced the separation process. The results presented in this study showed that the sludge particles (pellets) size of 2-5mm of diameter were formed with the microbial treatment of sludge after 2 days of fermentation that contained maximum 33.7% of total particles with 3-3.5mm of diameter. The settling rate (measured as total suspended solids (TSS) concentration, 130 mg/l) was faster in treated sludge than untreated sludge (TSS concentration, 440 mg/l) after 1 min of settling time. In 1 min of settling operation, 86.45% of TSS was settled in treated sludge while 4.35% of TSS settled in raw sludge. Lower turbidity was observed in treated sludge as compared to untreated sludge. The results to specific resistance to filtration (SRF) revealed that the fungal inoculum had significant potentiality to reduce SRF by 99.8% and 98.7% for 1% w/w and 4% w/w of TSS sludge, respectively. The optimum fermentation period recorded was 3 days for 1% w/w sludge and 6 days for 4% w/w sludge, respectively, for dewaterability test.