Nutrient recovery from domestic wastewater using a UASB-duckweed ponds system

The pilot-scale wastewater treatment system used in this study comprised a 40-l UASB reactor (6-h HRT) followed by three duckweed ponds in series (total HRT 15 days). During the warm season, the treatment system achieved removal values of 93%, 96% and 91% for COD, BOD and TSS, respectively. Residual values of ammonia, TKN and total phosphorus were 0.41 mg N/l, 4.4 mg N/l and 1.11 mg P/l, with removal efficiencies of 98%, 85% and 78%, respectively. The system achieved 99.998% faecal coliform removal during the warm season with final effluent containing 4 x 10(3) cfu/100 ml. During the winter, the system was efficient in removing COD, BOD and TSS but not nutrients. The system was deficient in the removal of faecal coliforms during the winter, producing effluent with 4.7 x 10(5) cfu/100 ml. During the warm season, the N removal consisted of 80% by plant uptake, 5% by sedimentation and 15% unaccounted for. A duckweed production rate of 33 t dry matter per hectare per 8 months was achieved.     

Causal model to describe the variation of faecal coliform concentrations in a pilot-scale test consisting of ponds aligned in series

In this study, the application of path analysis was tested to validate a causal model developed to verify the influence on several factors of the variation of faecal coliform concentration in pilot-scale ponds that treat domestic wastewater under distinct physical and operational characteristics. The ponds, aligned in series, are located in the city of Campina Grande, Northeastern Brazil. The model proved to be efficient for describing the variation in both secondary facultative and maturation ponds. The coefficient of determination (R²) ranged between 0.66 and 0.84 for the facultative ponds and between 0.54 and 0.95 for the maturation ponds. Effluent faecal coliform concentration was negatively affected by solar radiation in shallow ponds and positively affected by influent faecal coliform concentration in deep ponds. Typically the effects related to phytoplankton photosynthetic activity were well characterized in all shallow maturation ponds. Faecal coliform concentration was negatively affected by pH in almost all the cases. This model is not suitable for anaerobic ponds.     

Relationships between macroalgal biomass and microbiological quality of water in a phytotreatment pond

The microbiological quality of wastewater in phytotreatment ponds with foliose macroalgae can be influenced by biofilm formation on thallus surface. This hypothesis was tested with an in situ experiment which was carried out in a pond with Ulva spp. receiving wastewater from a land based fish farm at Piombino (Italy). The total bacterial load (TBL) was determined in the inflowing and outflowing waters and a multifactorial design was employed to investigate the effect of different macroalgal biomass. Microbiological analysis revealed a high TBL in the water column (18.4 ± 7.4 × 10⁸ cells ml⁻¹). TBL of inlet water was significantly correlated with quantity and quality of particulate organic matter (POM) of inflowing water, whereas no correlation was found between TBL and POM in the outlet water. A significant decrease in the POM concentration was detected within macroalgal ponds, due to the mechanical action of thalli which favoured POM sedimentation. Nevertheless, great TBLs were found in the outlet water. These findings suggest that TBL probably depended upon macroalgae. Indeed high bacterial density was found on macroalgal thallus surface (~10⁸ cells cm²). Furthermore, high plate counts of faecal bacteria (faecal enterococci) were determined on thallus surface (~ 40 CFU cm²) and outlet water (11 886 ± 3984 CFU 100 ml⁻¹) supporting the evidence that macroalgae negatively affect the microbiological quality of treated water. Bacterial activities in terms of exoenzymatic rates and secondary production were two folds higher in the water within macroalgal beds, than in the open water. These preliminary results suggest that high macroalgal biomass represents a ‚hot spot’ of bacterial density and activity that may affect microbiological quality of the treated water. Bacterial control of inlet water and management of macroalgal biomass through periodic removal are essential for a more efficient treatment of wastewater in phytotreatment ponds.     

Evaluation of a fluorescent antibody technique for the rapid enumeration of Bacteroides fragilis group of organisms in water

The Bacteroides fragilis group has been evaluated as a prospective rapid indicator of faecal contamination of water. Fluorescent antibody (FA) stained B. fragilis group bacteria were enumerated microscopically and compared with faecal coliform or Escherichia coli counts as indicators of faecal contamination. Environmental samples included surface waters (raw drinking water and known contaminated water). Laboratory disinfection experiments with ozone, chlorine and u. v. radiation were also performed. Bacteroides FA counts specifically detected recent human faecal contamination in field samples in 2–3 h. Samples with a high content of particulates or debris limited the sensitivity to about 10 FA counts/ml. Viable counts showed that the sensitivity to all three disinfection agents was essentially the same for Bacteroides and E. coli. Fluorescent antibody counts of Bacteroides , conversely, were not altered by any of the agents. Therefore, the Bacteroides FA method is not recommended for routine monitoring but may be useful for cases where extensive human faecal contamination is suspected (e.g. pipeline rupture or pollution of recreational water) and where rapid remedial action must be taken to protect the public health.     

Evaluation of a fluorescent antibody technique for the rapid enumeration of Bacteroides fragilis group of organisms in water

The Bacteroides fragilis group has been evaluated as a prospective rapid indicator of faecal contamination of water. Fluorescent antibody (FA) stained B. fragilis group bacteria were enumerated microscopically and compared with faecal coliform or Escherichia coli counts as indicators of faecal contamination. Environmental samples included surface waters (raw drinking water and known contaminated water). Laboratory disinfection experiments with ozone, chlorine and u.v. radiation were also performed. Bacteroides FA counts specifically detected recent human faecal contamination in field samples in 2-3 h. Samples with a high content of particulates or debris limited the sensitivity to about 10 FA counts/ml. Viable counts showed that the sensitivity to all three disinfection agents was essentially the same for Bacteroides and E. coli. Fluorescent antibody counts of Bacteroides, conversely, were not altered by any of the agents. Therefore, the Bacteroides FA method is not recommended for routine monitoring but may be useful for cases where extensive human faecal contamination is suspected (e.g. pipeline rupture or pollution of recreational water) and where rapid remedial action must be taken to protect the public health.     

Cadmium tolerance and antibiotic resistance in Escherichia coli isolated from waste stabilization ponds

The incidence pattern of cadmium tolerance and antibiotics resistance by Escherichia coli was examined periodically from the samples of water, sludge and intestine of fish raised in waste stabilization ponds in a sewage treatment plant. Samples of water and sludge were collected from all the selected ponds and were monitored for total counts of fecal coliform (FC), total coliform (TC) and the population of Escherichia coli, which was also obtained from the intestine of fishes. Total counts of both FC and TC as well as counts of E. coli were markedly reduced from the facultative pond to the last maturation pond. Tolerance limit to cadmium by E. coli tended to decline as the distance of the sewage effluent from the source increased; the effective lethal concentration of cadmium ranged from 0.1 mM in split chamber to 0.05 mM in first maturation pond. E. coli isolated from water, sludge and fish gut were sensitive to seven out of ten antibiotics tested. It appears that holistic functions mediated through the mutualistic growth of micro algae and heterotrophic bacteria in the waste stabilization ponds were responsible for the promotion of water quality and significant reduction of coliform along the sewage effluent gradient.     

Faecal indicator bacteria at fish farms

The observed concentrations of bacteria at two large fish farms were not high, but due to the great volume of the discharge the total amount of bacteria was large. Total coliform (TC) bacteria identified belonged mainly to the genera Enterobacter, Citrobacter and Aeromonas. The majority of faecal coliform (FC) strains were Escherichia coli. E. coli was absent, or occurred at very low concentrations, in the influent water, but was present in the effluent water, in the sediment, and at one fish farm also in fish faeces. FC bacteria were not observed in the fish feed. The concentrations of faecal streptococci (FS) in the influent water were low, but strains isolated were identified as group D streptococci. The concentrations of FS were low in the feed and sediment samples but were elevated in the fish faeces and also in the effluent.     

Prevalence and transmission of antimicrobial resistance among <Emphasis Type="Italic">Aeromonas</Emphasis> populations from a duckweed aquaculture based hospital sewage water recycling system in Bangladesh

In order to investigate the influence of a duckweed aquaculture based hospital sewage water recycling plant on the prevalence and dissemination of antibiotic resistance, we made use of an existing collection of 1,315 Aeromonas isolates that were previously typed by the biochemical fingerprinting PhP-AE system. In these treatment plant, hospital raw sewage water is first collected in a settlement pond (referred to as sewage water in this study) and is then transferred to a lagoon, where the duckweed (Lemnaceae) is grown (referred to as lagoon). The duckweed is harvested and used as feed for the fish in a separate pond (referred to as fish pond). From this collection, representatives of 288 PhP types were subjected to antibiotic susceptibility testing for eight antimicrobials by broth microdilution method. The overall resistance rates among Aeromonas isolates from the treatment plant were highest for ampicillin (87%) and erythromycin (79%) followed by cephalothin (58%), nalidixic acid (52%), streptomycin (51%), tetracycline (31%), chloramphenicol (13%) and gentamicin (8%). A significantly lower prevalence of antibiotic resistance was found in Aeromonas from environmental control water, patient stool samples, duckweed and fish compared to sewage water isolates. The prevalence of resistance in the sewage water was not significantly reduced compared to the lagoon water and fish pond. Throughout the treatment system, the frequencies of resistant strains were found to diminish during the sewage water purification process, i.e. in the lagoon where sewage water is used to grow the duckweed. However, the frequency of resistant strains again increased in the fish pond where sewage grown duckweed is used for aquaculture. Among the selected isolates, two multiresistant clonal groups of Aeromonas caviae HG4 were identified that exhibited indistinguishable PhP and amplified fragment length polymorphism fingerprints and shared a common plasmid of approximately 5 kb. Representatives of both groups were recovered from almost every part of the sewage treatment plant but not in the control ponds nor in human samples, which suggests that specific multiresistant Aeromonas clones are able to persist and spread throughout the entire purification process.     

Factors associated with the presence of coliforms in the feed and water of feedlot cattle

The objective of this study was to investigate coliform counts in feedlot cattle water and feed rations and their associations with management, climate, fecal material, and water Escherichia coli O157 using a cross-sectional study design. Coliform counts were performed on feed samples from 671 pens on 70 feedlots and on water samples from 702 pens on 72 feedlots in four U.S. states collected between May and August 2001. Management and climate factors were obtained by survey and observation. Month of sampling (higher in May and June), presence of corn silage in the ration (negative association), temperature of the feed 1 in. (ca. 2.5 cm) below the surface at the time of sampling (negative association), and wind velocity at the time of sampling (positive association) were significantly associated with log10 coliform levels in feed. Month of sampling (lower in May versus June July and August), water pH (negative association), and water total solids (positive association) were significantly associated with log10 water coliform levels. Coliform counts in feed and water were not associated with prevalence of E. coli O157 in cattle feces or water. Management risk factors must be interpreted with caution but the results reported here do not support the use of coliform counts as a marker for E. coli O157 contamination of feed or water.     

The role of visible faecal material as a vehicle for generic Escherichia coli,coliform, and other enterobacteria contaminating poultry carcasses during slaughtering

AIMS: A comparison of Enterobacteriaceae, coliform and Escherichia coli counts in chicken carcasses with and without visible faecal contamination was conducted to evaluate the role of contamination as a vehicle for generic E. coli, coliform and other enterobacteria contaminating broiler chicken carcasses when processed under routine commercial operations. METHODS AND RESULTS: Samples were removed from the processing line immediately after evisceration, inside-outside shower and chilling for microbiological analysis. After evisceration, mean counts were significantly different only for E. coli (P < or = 0.05) in chicken carcasses with and without visible faecal contamination. While the spray wash practice was not efficient enough for complete removal of the visible contamination from carcasses, leading to microbiological reduction percentages lower than expected, 25 ppm chlorinated water chilling did reduce the contamination level considerably in all samples. CONCLUSIONS: Carcasses with and without visible faecal contamination harboured E. coli and other potentially hazardous enterobacteria. E. coli was the predominant strain isolated in all samples, Enterobacter cloacae being next most frequent. SIGNIFICANCE AND IMPACT OF THE STUDY: The zero tolerance of visible faecal contamination requirement alone is not sufficient to assure safety and to improve the microbial quality of carcasses.     

Factors Associated with the Presence of Coliforms in the Feed and Water of Feedlot Cattle

The objective of this study was to investigate coliform counts in feedlot cattle water and feed rations and their associations with management, climate, fecal material, and water Escherichia coli O157 using a cross-sectional study design. Coliform counts were performed on feed samples from 671 pens on 70 feedlots and on water samples from 702 pens on 72 feedlots in four U.S. states collected between May and August 2001. Management and climate factors were obtained by survey and observation. Month of sampling (higher in May and June), presence of corn silage in the ration (negative association), temperature of the feed 1 in. (ca. 2.5 cm) below the surface at the time of sampling (negative association), and wind velocity at the time of sampling (positive association) were significantly associated with log₁₀ coliform levels in feed. Month of sampling (lower in May versus June July and August), water pH (negative association), and water total solids (positive association) were significantly associated with log₁₀ water coliform levels. Coliform counts in feed and water were not associated with prevalence of E. coli O157 in cattle feces or water. Management risk factors must be interpreted with caution but the results reported here do not support the use of coliform counts as a marker for E. coli O157 contamination of feed or water.     

Coliform dynamics and the implications for source tracking

In many parts of the world, coliform counts in recreational waters are unacceptably high. In an attempt to rectify this problem, programmes are under way to develop methods that will allow the sources of the faecal contamination thought to be responsible for these elevated counts to be identified. The success of these efforts depends on the validity of several assumptions that underlie many of the proposed methods. One of the critical assumptions is that the clonal composition of the coliform species being monitored in a water body reflects the clonal composition of the species in the host populations responsible for the faecal inputs into that water body. To determine the extent to which among-strain variation in a coliform species might invalidate this assumption, a series of simple mathematical models was proposed and analysed. The first series of models assumed that all cells of species were identical. The question posed was - is the density of a coliform species in a body of water linearly related to the rate at which cells of the species enter the water body via faecal production? The results of these models suggest that, over a wide range of conditions, cell densities in the water body are linearly related to the rate at which cells enter the water body as a result of faecal contamination. This outcome occurs whether or not cells are capable of division in the external environment. When the rate of cell division depends on the concentration of available nutrients then, when nutrient input rates are 'high' and rates of faecal contamination are 'low', this linear relationship does not hold. The second series of models assumed that the coliform species consists of different strains and that these strains differ in their performance in the external environment. The results of these multistrain models show that the relative abundance of strains in the external environment is unlikely to reflect their relative abundance in the faecal inputs to the environment. Consequently, statements such as - domestic animals are responsible for 30% and wildlife for 70% of the faecal inputs to a water body - may well be meaningless.     

Water quality and public health in northern Sudan: a study of rural and peri-urban communities

Access to adequate supplies of good quality drinking water continues to be limited among many rural and peri-urban communities in Africa, despite several decades of water improvement programmes. The present study investigated water quality at the source and point of consumption among rural and peri-urban communities in northern Sudan. Faecal coliform counts were determined by the membrane filtration technique and geometric mean counts compared in different seasons and among the different communities. Among nomadic pastoralists and riverine villages, both water sources and water stored for consumption had faecal coliform counts grossly in excess of WHO standards, with higher counts at the end of the rainy season. In the peri-urban community on the outskirts of Omdurman, while water quality from the distribution system had faecal coliform counts generally below 10 dl - 1, after storage, water was of considerably lower quality, with faecal coliform counts up to 1000 d1 - 1. The highest counts again occurred in the rainy season. Rates of diarrhoeal disease for Khartoum province were also greatest towards the end of the rainy season. The study has shown that poor quality water continues to be a major risk factor for public health in these communities.     

Evaluation of coliforms as indicators of water quality in India.

The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.     

Evaluation of coliforms as indicators of water quality in India

P.W. RAMTEKE, J.W. BHATTACHARJEE, S.P. PATHAK AND N. KALRA. 1992. The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.     

Microbial contamination of vegetable crop and soil profile in arid regions under controlled application of domestic wastewater

Increasing lack of potable water in arid countries leads to the use of treated wastewater for crop production. However, the use of inappropriate irrigation practices could result in a serious contamination risk to plants, soils, and groundwater with sewage water. This research was initiated in view to the increasing danger of vegetable crops and groundwater contamination with pathogenic bacteria due to wastewater land application. The research was designed to study: (1) the effect of treated wastewater irrigation on the yield and microbial contamination of the radish plant under field conditions; (2) contamination of the agricultural soil profile with fecal coliform bacteria. Effluent from a domestic wastewater treatment plant (100%) in Jeddah city, Saudi Arabia, was diluted to 80% and 40% with the groundwater of the experimental site constituting three different water qualities plus groundwater as control. Radish plant was grown in two consecutive seasons under two drip irrigation systems and four irrigation water qualities. Upon harvesting, plant weight per ha, total bacterial, fecal coliform, fecal streptococci were detected per 100 g of dry matter and compared with the control. The soil profile was also sampled at an equal distance of 3 cm from soil surface for fecal coliform detection. The results indicated that the yield increased significantly under the subsurface irrigation system and the control water quality compared to surface irrigation system and other water qualities. There was a considerable drop in the count of all bacteria species under the subsurface irrigation system compared to surface irrigation. The bacterial count/g of the plant shoot system increased as the percentage of wastewater in the irrigation water increased. Most of the fecal coliform bacteria were deposited in the first few centimeters below the column inlet and the profile exponentially decreased with increasing depth.     

Coliform concentration reduction and related performance evaluation of a down-flow anaerobic fixed bed reactor treating low-strength saline wastewater

Low-strength saline wastewater may be generated by tourist facilities, industries and communities located in coastal areas. Sea salts, mostly chlorides, when present in wastewaters at high concentrations, can cause inhibition on biological treatment processes. In this study, a laboratory down-flow anaerobic fixed bed reactor (DFAFBR) was used for treating saline wastewater. This wastewater was simulated by dilution of piggery manure in a synthetic saline water to obtain a final total COD concentration in the range of 1100-2900 mg/l and a salt concentration of 15 g/l. The DFAFBR was operated at hydraulic retention times (HRT) of 96, 48, 24 and 12 h. The results showed that at sea salts concentrations in the range from 5 to 15 g/l, total coliform concentration reduction efficiencies higher than 97% were achieved. A decrease in the total and faecal coliform concentration reduction efficiencies from 99.5% to 90.5% and 92.5%, respectively, was observed when the HRT decreased from 96 to 12 h. Enumeration of coliform bacteria isolated from the biofilm in different zones of the reactor showed that more than 94% of the total amount was removed in the upper zone. A HRT of 24 h was required to obtain total COD, organic-N, total-P and faecal coliform concentration reduction efficiencies higher than 72%, 51%, 39% and 98%, respectively. A concentration of 8.4 g/l for chlorides, 1.25 g/l for sulphates and 4.6 g/l for sodium did not affect the process performance.     

Inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> and coliform bacteria in traditional brass and earthernware water storage vessels

The detection and enumeration of indicator bacteria such as Escherichia coli is used to assess the extent of faecal contamination of drinking water. On the basis of this approach, the effectiveness of storing water contaminated with faecal indicator bacteria in brass or earthern vessels (mutkas) of the type used in rural India have been investigated. Suspensions of bacteria in sterile distilled water were maintained for up to 48 h in each vessel and enumerated by surface plate counts on nutrient agar (non-selective) and several selective coliform media at 37 °C either under standard aerobic conditions, or under conditions designed to neutralise reactive oxygen species (ROS), e.g. using an anaerobic cabinet to prepare plates of pre-reduced growth medium or by inclusion of sodium pyruvate in the growth medium, with incubation of aerobically-prepared plates in an anaerobic jar. The counts obtained for E. coli decreased on short-term storage in a brass mutka; counts for selective media were lower than for equivalent counts for non-selective medium, with ROS-neutralised conditions giving consistently higher counts than aerobic incubation. However, after 48 h, no bacteria were cultivable under any conditions. Similar results were obtained using water from environmental sources in the Panjab, and from rural households where brass and earthern mutkas are used for storage of drinking water, with enumeration on selective coliform media (presumptive total coliforms). In all cases results indicated that, while storage of water in a brass mutka can inactivate E. coli and coliforms over a 48 h period, standard aerobic plate counting using selective media may not be fully effective in enumerating sub-lethally damaged bacteria.     

Dynamics of manganese,cadmium, and lead in experimental power plant ponds

The purpose of this study was to determine the effect of heated power plant water on the uptake and retention of manganese, cadmium and lead in selected aquatic invertebrates, channel catfish, green sunfish, and aquatic macrophytes and to study the distribution of manganese, cadmium and lead in sediments and water of experimental power plant ponds.The study was accomplished by placing fingerling channel catfish and green sunfish in holding pens in two ponds, one an experimental pond and one a control pond. Whole fish and selected organs of channel catfish and green sunfish were analyzed during the study. The experimental pond received heated power plant water and was maintained 4–6° C above ambient temperature during the study. Sediments, water, Odonata nymphs, tubificid annelids, snails, leeches, fingernail clams and duckweed were also analyzed for the metals.A typical distribution profile for manganese, cadmium and lead in power plant cooling ponds was developed.     

Sourcing faecal pollution from onsite wastewater treatment systems in surface waters using antibiotic resistance analysis

AIMS: To identify the sources of faecal contamination in investigated surface waters and to determine the significance of onsite wastewater treatment systems (OWTS) as a major contributor to faecal contamination. METHODS AND RESULTS: Antibiotic resistance patterns (ARP) were established for a library of 717 known Escherichia coli source isolates obtained from human, domesticated animals, livestock and wild sources. Eight commonly used antibiotics, including amoxicillin, cephalothin, erythromycin, gentamicin, ofloxacin, chlortetracycline, tetracycline and moxalactam, at four different concentrations were used to obtain ARPs for E. coli isolates. Discriminant analysis (DA) was used to differentiate between the ARP of sources isolates. The developed ARP library was found to be adequate for discriminating human from nonhuman isolates, and was used to classify 256 enumerated E. coli isolates collected from monitored surface water locations. CONCLUSIONS: The resulting ARP DA indicated that a majority of the faecal contamination in more rural areas was nonhuman; however, the percentage of human isolates increased significantly in urbanized areas using OWTS for wastewater treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: This study signifies the feasibility of using ARP for source tracking faecal contamination in surface waters, and linking faecal contamination to OWTS. The information will enable regulatory authorities to implement appropriate management practices to reduce the contamination of water resources caused by high densities and failing OWTS.