Survival of fecal coliforms in dry-composting toilets

The dry-composting toilet, which uses neither water nor sewage infrastructure, is a practical solution in areas with inadequate sewage disposal and where water is limited. These systems are becoming increasingly popular and are promoted to sanitize human excreta and to recycle them into fertilizer for nonedible plants, yet there are few data on the safety of this technology. This study analyzed fecal coliform reduction in approximately 90 prefabricated, dry-composting toilets (Sistema Integral de Reciclamiento de Desechos Orgánicos [SIRDOs]) that were installed on the U.S.-Mexico border in Ciudad Juárez, Chihuahua, Mexico. The purpose of this study was to determine fecal coliform reduction over time and the most probable method of this reduction. Biosolid waste samples were collected and analyzed at approximately 3 and 6 months and were classified based on U.S. Environmental Protection Agency standards. Results showed that class A compost (high grade) was present in only 35.8% of SIRDOs after 6 months. The primary mechanism for fecal coliform reduction was found to be desiccation rather than biodegradation. There was a significant correlation (P = 0.008) between classification rating and percent moisture categories of the biosolid samples: drier samples had a greater proportion of class A samples. Solar exposure was critical for maximal class A biosolid end products (P = 0.001). This study only addressed fecal coliforms as an indicator organism, and further research is necessary to determine the safety of composting toilets with respect to other pathogenic microorganisms, some of which are more resistant to desiccation.     

Identification of strains isolated as total and fecal coliforms and comparison of both groups as indicators of fecal pollution in tropical climates

This study was undertaken to better characterize the groups of total coliforms (TC) and fecal coliforms (FC) and to evaluate both groups as indicators of fecal contamination of drinking well water in a tropical climate (The Ivory Coast, West Africa). Isolated colonies obtained as TC or FC on membrane filters were identified using the API-20E system. From the well water samples, 58 golden-green colonies with a metallic sheen isolated on Endo medium (TC) were identified as Escherichia coli (55%), Enterobacter (26%), Klebsiella (14%), Proteus (3%), and Citrobacter (2%). Among 132 colonies isolated on Endo medium as non-TC (not showing the characteristic golden metallic sheen), 10% were identified as E. coli. The 196 blue colonies isolated on M-FC medium at 44.5 degrees C (FC) were identified as E. coli (66%), Klebsiella (12%), Enterobacter (10%), Citrobacter (5%), Salmonella (3%), Serratia (3%), Proteus (2%), and Yersinia (0.5%). Among 24 nonblue colonies on M-FC medium, none were identified as E. coli. Of the colonies isolated from human feces, E. coli represents 92% of the TC and 89% of the FC. Although these results are limited, they tend to confirm the greater specificity of the fecal coliform technique over that of total coliform for the detection of fecal contamination of untreated well water. From the results presented here and the observations of other workers, it is suggested that the use of FC instead of TC should be considered as the method of choice for determining drinking water pollution of untreated groundwater supplies.     

Validity of fecal coliforms, total coliforms, and fecal streptococci as indicators of viruses in chlorinated primary sewage effluents.

Quantities of combined chlorine that usually destroyed more than 99.999% of the indigenous fecal coliforms, total coliforms, and fecal streptococci in primary sewage effluents destroyed only 85 to 99% of the indigenous viruses present. Viruses were recovered from five of eight chlorinated primary effluents from which fecal coliforms were not recovered by standard most-probable-number procedures. The limited volumes of such chlorinated effluents that can be tested for indicator bacteria with currently available multiple-tube and membrane filter techniques restrict the value of fecal coliforms, fecal streptococci, and even total coliforms as indicators of viruses in these effluents. Although fecal coliforms and fecal streptococci are useful indicators of viruses in effluents from which these bacteria are recovered, the absence of these bacteria and even total coliforms from disinfected effluents (in standard tests) does not assure that viruses are also absent.     

在饮用水中协同检测“粪型大肠菌群”的试验方法

阐述了在饮用水中检测"粪型大肠菌群"的意义,强调了大肠菌群与粪型大肠菌群的关系,总结出"粪型大肠菌群"的检测条件。     

Comparison of culturable fecal coliforms and Escherichia coli enumeration in freshwaters

Fecal coliforms (FC) counts were compared with Escherichia coli counts in differently contaminated freshwater samples (n = 166). FC were enumerated by plate count on triphenyl 2,3,5-tetrazolium chloride Tergitol medium. Escherichia coli were enumerated by the most probable number microplate method based on the detection of glucuronidase activity. FC and E. coli counts were highly correlated; an average E. coli/FC ratio equal to 0.77 was found, meaning that on average, 77% of FC were E. coli. Knowing the E. coli/FC ratio allows us to convert the historical microbiological quality data expressed in FC counts into E. coli abundance and thus to compare with present and future monitoring data that are (or will be) based on E. coli enumeration.     

Enumeration of heterotrophs, fecal coliforms and Escherichia coli in water: comparison of 3M Petrifilm plates with standard plating procedures

A total of 177 naturally contaminated water samples were analyzed by membrane filtration according to the Standard Methods for the Examination of Water and Wastewater published by the American Public Health Association. Filters were incubated in parallel on mHPC-agar and 3M™ Petrifilm™ Aerobic Count Plates (Petrifilm™ AC plates) for heterotrophic counts. Fecal coliforms and Escherichia coli were enumerated on mFC-agar and 3M™ Petrifilm™ E. coli/Coliform Count Plates (Petrifilm™ EC plates). Typical colonies on each media type were confirmed following standard procedures. Heterotrophic counts were between 10³ and 10⁴ CFU/mL and the average log₁₀ counts obtained on Petrifilm™ AC plates were about two-fold lower than on mHPC-agar. Counts for fecal coliforms and E. coli were between 10² and 10³ CFU/mL. Average log₁₀ counts for confirmed fecal coliforms obtained on Petrifilm™ EC plates were slightly lower than on mFC agar with a correlation coefficient of 0.949. The average log₁₀ counts for confirmed E. coli on Petrifilm™ EC plates and on mFC agar were statistically not different (P=0.126) with a correlation coefficient of 0.879. Specificity of Petrifilm™ EC plates and mFC agar was evaluated by comparing typical colony counts with confirmed counts. On mFC agar, counts for typical colonies were by 2 log₁₀ CFU higher than the actual confirmed counts. In contrast, on Petrifilm™ EC plates typical colony counts were almost identical to confirmed colony counts for both fecal coliforms and E. coli. This comparison illustrates the high specificity of Petrifilm™ EC plates for enumeration of both fecal coliforms and E. coli in water.     

Modification of delayed-incubation procedure for detection of fecal coliforms in water

Three holding media, including the vitamin-free Casitone holding medium (m-VFC) recommended by Standard Methods for the Examination of Water and Wastewater for use with the delayed-incubation membrane filter procedure, were compared for their ability to maintain viability of fecal coliforms. Each medium was tested according to the procedure described in the above reference with 60 to 80 pure cultures of fecal coliforms and a variety of natural water samples containing fecal coliforms. Fecal coliform recovery with m-ST holding medium (containing ethanol, sulfanilamide, and Tris [pH 8.6] was significantly greater than recovery with m-VFC (containing vitamin-free casein hydrolysate, sodium benzoate, sulfanilamide, and ethanol). Recovery with m-VFC, was, in turn, significantly greater than with NSB medium (containing nutrient broth, boric acid, and NaCl as major ingredients). Fecal coliform counts obtained with m-ST by the delayed-incubation membrane filter procedure were higher than counts obtained by the standard immediate incubation. This result suggested that some of the sublethally injured fecal coliforms in natural water samples may have recovered during the incubation period. We propose that m-ST be used in place of m-VFC for the delayed-incubation membrane filter procedure.     

Effect of anaerobic digestion temperature on odour, coliforms and chlortetracycline in swine manure or monensin in cattle manure

Aims: This study evaluated the effect of anaerobic digestion at 22, 38 and 55°C on odour, coliforms and chlortetracycline (CTC) in swine manure or monensin (MON) in cattle manure. Methods and Results: Swine or cattle were fed the respective growth promotant, manure was collected, and 2‐l laboratory methane digesters were established at the various temperatures and sampled over 25 or 28 days. After 21 days, the concentration of CTC in the 22, 38 and 55°C swine digester slurries decreased 7, 80 and 98%, respectively. Coliforms in the 22°C digester slurries were still viable after 25 days; however, they were not detectable in the 38 and 55°C slurries after 3 and 1 days, respectively. After 28 days, the concentration of MON in the 22, 38 and 55°C cattle digester slurries decreased 3, 8 and 27%, respectively. Coliforms in the 22°C cattle digester slurries were still viable after 28 days; however, they were not detectable in the 38 and 55°C slurries after 14 and 1 days, respectively. Conclusions: These studies indicate that anaerobic digestion at 38 or 55°C may be an effective treatment to reduce coliforms and CTC; however, it is not an effective treatment to reduce MON. Significance and Impact of the Study: More studies are needed to determine which pharmaceuticals are susceptible to degradation by a specific manure treatment to prevent negative environmental consequences.     

Modification of delayed-incubation procedure for detection of fecal coliforms in water.

Three holding media, including the vitamin-free Casitone holding medium (m-VFC) recommended by Standard Methods for the Examination of Water and Wastewater for use with the delayed-incubation membrane filter procedure, were compared for their ability to maintain viability of fecal coliforms. Each medium was tested according to the procedure described in the above reference with 60 to 80 pure cultures of fecal coliforms and a variety of natural water samples containing fecal coliforms. Fecal coliform recovery with m-ST holding medium (containing ethanol, sulfanilamide, and Tris [pH 8.6] was significantly greater than recovery with m-VFC (containing vitamin-free casein hydrolysate, sodium benzoate, sulfanilamide, and ethanol). Recovery with m-VFC, was, in turn, significantly greater than with NSB medium (containing nutrient broth, boric acid, and NaCl as major ingredients). Fecal coliform counts obtained with m-ST by the delayed-incubation membrane filter procedure were higher than counts obtained by the standard immediate incubation. This result suggested that some of the sublethally injured fecal coliforms in natural water samples may have recovered during the incubation period. We propose that m-ST be used in place of m-VFC for the delayed-incubation membrane filter procedure.     

Runoff transport of faecal coliforms and phosphorus released from manure in grass buffer conditions

AIMS: To test the hypothesis that faecal coliform (FC) and phosphorus (P) are transported similarly in surface runoff through the vegetative filter strip after being released from land-applied manure. METHODS AND RESULTS: The Hagerstown soil was packed into boxes that were 10 cm deep, 30 cm wide and 100, 200 or 300 cm long. Grass was grown in boxes prior experiments. Same-length boxes were placed under rainfall simulator and tilted to have with either 2% or 4% slopes. Dairy manure was broadcast on the upper 30-cm section. Rainfall was simulated and runoff samples were collected and analysed for Cl, FC and total phosphorus (TP). Mass recovery, the concentration decrease rate k, and the ratio FC : TP showed that there was a consistent relationship between FC and TP in runoff. Conclusion: The FC and TP transport through simulated vegetated buffer strips were highly correlated. SIGNIFICANCE AND IMPACT OF THE STUDY: As a knowledge base on the effect of the environmental parameters on P transport in vegetated buffer strips is substantially larger than for manure-borne bacteria, the observed similarity may enhance ability to assess the efficiency of the vegetated buffer strips in retention of FC currently used as indicator organisms for manure-borne pathogens.     

Isolation of fecal coliforms from pristine sites in a tropical rain forest

Samples collected from water accumulated in leaf axilae of bromeliads (epiphytic flora) in a tropical rain forest were found to harbor fecal coliforms. Random identification of fecal coliform-positive isolates demonstrated the presence of Escherichia coli. This bacterium was also isolated from bromeliad leaf surfaces. These data indicate that E. coli may be part of the phyllosphere microflora and not simply a transient bacterium of this habitat. The isolation of fecal coliforms from these sites was unexpected and raises questions as to the validity of using fecal coliforms as indicators of biological water quality in the tropics.     

Membrane filter method for recovery of fecal coliforms in chlorinated sewage effluents.

The standard one-step M-FC broth-membrane-filter procedure for recovery of fecal coliforms from chlorinated sewage effluents is much less effective than the multiple-tube (most-probable-number) technique. A two-step membrane-filter method, using a pre-enrichment technique with phenol red lactose broth and incubation at 35 degrees C for 4 h, followether 18+/-2 h, enhanced fecal coliform recovery from chlorinated effluents. The results of 126 comparisons using chlorinated effluents from five wastewater plants showed that fecal coliform recovery by using the two-step membrane-filter method is comparable to that using the multiple-tube procedure.     

Isolation of fecal coliforms from pristine sites in a tropical rain forest.

Samples collected from water accumulated in leaf axilae of bromeliads (epiphytic flora) in a tropical rain forest were found to harbor fecal coliforms. Random identification of fecal coliform-positive isolates demonstrated the presence of Escherichia coli. This bacterium was also isolated from bromeliad leaf surfaces. These data indicate that E. coli may be part of the phyllosphere microflora and not simply a transient bacterium of this habitat. The isolation of fecal coliforms from these sites was unexpected and raises questions as to the validity of using fecal coliforms as indicators of biological water quality in the tropics.     

Antibiotic resistance among different species of fecal coliforms isolated from water samples.

The distribution of resistance to ampicillin, chloramphenicol, sulfonamides, tetracycline, and streptomycin among fecal coliforms in sewage, surface waters, and sea water was investigated. The incidence of resistant strains among isolates varied significantly among the water samples, without obvious connection with the water source or the level of pollution. The average frequency of multiple resistance was not always high in the same samples in which the overall resistance was high. The species composition varied considerably in different water samples. A significant correlation was observed between the relative frequency of Klebsiella species and the incidence of ampicillin resistance in water samples. The importance of species composition of fecal coliforms, affected by their source and by the aquatic environment, on the resistance pattern is noted.     

Short incubation of presumptive media for detection of fecal coliforms in shellfish.

Positive fecal coliform most-probable number results were compiled from 7,701 shellfish samples examined over 9 years. Generally, less than 2% of all positive reactions in EC medium are results of inoculations from presumptive media positive at the maximum (48-h) incubation period.     

Inactivation of enterococci and fecal coliforms from sewage and meatworks effluents in seawater chambers.

Inactivation in sunlight of fecal coliforms (FC) and enterococci (Ent) from sewage and meatworks effluents was measured in 300-liter effluent-seawater mixtures (2% vol/vol) held in open-topped chambers. Dark inactivation rates (kDs) were measured (from log-linear survival curves) in enclosed chambers and 6-liter pots. The kD for FC was 2 to 4 times that for Ent, and inactivation was generally slower at lower temperatures. Sunlight inactivation was described in terms of shoulder size (n) and the slope (k) of the log-linear portion of the survival curve as a function of global solar insolation and UV-B fluence. The n values tended to be larger for Ent than for FC, and the k values for FC were around twice those for Ent in both effluent-seawater mixtures. The combined sunlight data showed a general inactivation rate (k) ranking in effluent-seawater mixtures of meatworks FC > sewage FC > meatworks Ent > sewage Ent. Describing 90% inactivation in terms of insolation (S90) gave far less seasonal variation than T90 (time-dependent) values. However, there were significant differences in inactivation rates between experiments, indicating the contribution to inactivation of factors other than insolation. Inactivation rates under different long-pass optical filters decreased with the increase in the spectral cutoff wavelength (lambda 50) of the filters and indicated little contribution by UV-B to total inactivation. Most inactivation appeared to be caused by two main regions of the solar spectrum--between 318 and 340 nm in the UV region and > 400 nm in the visible region.     

Use of beta-D-galactosidase and beta-D-glucuronidase activities for quantitative detection of total and fecal coliforms in wastewater

Two enzymatic methods based on the measurement of the beta-D-galactosidase activity of total coliforms and the beta-D-glucuronidase activity of Escherichia coli were used to assess coliform levels in wastewater alongside traditional culture-based techniques, which can be biased by the aggregation of bacteria or their attachment to particles. Enzymatic methods were precise (i.e., coefficients of variation were 9%-15%), rapid (response in 20 min), and correlated well (in log units) with traditional techniques for raw and treated sewage (r2 > 0.75). They were used for rapid assessment of coliform removal efficiency in two different wastewater treatments. These methods could be useful for the estimation of the abundance of coliforms in domestic sewage and their removal by wastewater treatment processes.     

Rapid detection of total and fecal coliforms in water by enzymatic hydrolysis of 4-methylumbelliferone-beta-D-galactoside

Three fluorogenic methylumbelliferone (MU) substrates were evaluated for rapid detection of total and fecal coliform bacteria (TC and FC) in drinking water. 4-MU-beta-D-galactoside, MU-heptanoate, and MU-glucuronide were used to determine enzyme activity as a surrogate measure of coliform concentration. Coliforms occurring in river water and in potable water artificially contaminated with raw sewage were tested. The initial rate of hydrolysis (delta F) of MU-beta-D-galactoside showed promise as an indicator of TC and FC within 15 min. delta F of MU-glucuronide was insufficient in the 15-min assay, and combinations of the MU substrates did not enhance delta F. A direct membrane filter method incorporating MU-beta-D-galactoside into an agar medium allowed the detection of as few as 1 FC per 100 ml within 6 h.