The compartment bag test (CBT) for enumerating fecal indicator bacteria: Basis for design and interpretation of results

For the past several years, the compartment bag test (CBT) has been employed in water quality monitoring and public health protection around the world. To date, however, the statistical basis for the design and recommended procedures for enumerating fecal indicator bacteria (FIB) concentrations from CBT results have not been formally documented. Here, we provide that documentation following protocols for communicating the evolution of similar water quality testing procedures. We begin with an overview of the statistical theory behind the CBT, followed by a description of how that theory was applied to determine an optimal CBT design. We then provide recommendations for interpreting CBT results, including procedures for estimating quantiles of the FIB concentration probability distribution, and the confidence of compliance with recognized water quality guidelines. We synthesize these values in custom user-oriented 'look-up' tables similar to those developed for other FIB water quality testing methods. Modified versions of our tables are currently distributed commercially as part of the CBT testing kit

Local drinking water filters reduce diarrheal disease in Cambodia: a randomized, controlled trial of the ceramic water purifier.

A randomized, controlled intervention trial of two household-scale drinking water filters was conducted in a rural village in Cambodia. After collecting four weeks of baseline data on household water quality, diarrheal disease, and other data related to water use and handling practices, households were randomly assigned to one of three groups of 60 households: those receiving a ceramic water purifier (CWP), those receiving a second filter employing an iron-rich ceramic (CWP-Fe), and a control group receiving no intervention. Households were followed for 18 weeks post-baseline with biweekly follow-up. Households using either filter reported significantly less diarrheal disease during the study compared with a control group of households without filters as indicated by longitudinal prevalence ratios CWP: 0.51 (95% confidence interval [CI]: 0.41-0.63); CWP-Fe: 0.58 (95% CI: 0.47-0.71), an effect that was observed in all age groups and both sexes after controlling for clustering within households and within individuals over time

The operation, flow conditions and microbial reductions of an intermittently operated, household-scale slow sand filter

Nearly one-fifth of the world\u27s population lacks access to safe, reliable sources of drinking water. Point of use (POU) household water treatment technology allows people to improve the quality of their water by treating it in the home. A promising emerging POU technology is the biosand filter (BSF). The BSF is a household-scale, intermittently operated slow sand filter that maintains a wet media bed containing a schmutzdecke and allows periodic water dosing by the user. Step input chemical tracer tests indicated that the BSF operates at near-plug flow conditions. Six-to-eight week longitudinal challenge studies were conducted with daily charges of surface water spiked with E. coli strain B bacteria, coliphages MS2 and PRD-1 and human enteric virus echovirus type 12. The BSF ripened in a manner similar to conventional SSFs. Flow rate slowed and microbial reductions improved over time with ripening. E. coli reductions were ~90% following filter startup but improved to 95—99.5% over time. Microbial reductions were greater with greater residence time within the filter, especially for water retained in the filter bed overnight. E. coli and echovirus 12 reductions were greater than those of coliphages MS2 and PRD-1

Bacterial Contamination on Household Toys and Association with Water, Sanitation and Hygiene Conditions in Honduras

There is growing evidence that household water treatment interventions improve microbiological water quality and reduce diarrheal disease risk. Few studies have examined, however, the impact of water treatment interventions on household-level hygiene and sanitation. This study examined the association of four water and sanitation conditions (access to latrines, improved sanitation, improved water and the plastic biosand filter) on the levels of total coliforms and E. coli on existing and introduced toys during an on-going randomized controlled trial of the plastic biosand filter (plastic BSF). The following conditions were associated with decreased bacterial contamination on children’s toys: access to a latrine, access to improved sanitation and access to the plastic BSF. Overall, compared to existing toys, introduced toys had significantly lower levels of both E. coliand total coliforms. Results suggest that levels of fecal indicator bacteria contamination on children’s toys may be associated with access to improved water and sanitation conditions in the home. In addition, the fecal indicator bacteria levels on toys probably vary with duration in the household. Additional information on how these toys become contaminated is needed to determine the usefulness of toys as indicators or sentinels of water, sanitation and hygiene conditions, behaviors and risks

Evaluation of the Impact of the Plastic BioSand Filter on Health and Drinking Water Quality in Rural Tamale, Ghana

A randomized controlled trial of the plastic BioSand filter (BSF) was performed in rural communities in Tamale (Ghana) to assess reductions in diarrheal disease and improvements in household drinking water quality. Few studies of household water filters have been performed in this region, where high drinking water turbidity can be a challenge for other household water treatment technologies. During the study, the longitudinal prevalence ratio for diarrhea comparing households that received the plastic BSF to households that did not receive it was 0.40 (95% confidence interval: 0.05, 0.80), suggesting an overall diarrheal disease reduction of 60%. The plastic BSF achieved a geometric mean reduction of 97% and 67% for E. coli and turbidity, respectively. These results suggest the plastic BSF significantly improved drinking water quality and reduced diarrheal disease during the short trial in rural Tamale, Ghana. The results are similar to other trials of household drinking water treatment technologies

Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces

Assessment of the risks posed by severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) on surfaces requires data on survival of this virus on environmental surfaces and on how survival is affected by environmental variables, such as air temperature (AT) and relative humidity (RH). The use of surrogate viruses has the potential to overcome the challenges of working with SARS-CoV and to increase the available data on coronavirus survival on surfaces. Two potential surrogates were evaluated in this study; transmissible gastroenteritis virus (TGEV) and mouse hepatitis virus (MHV) were used to determine effects of AT and RH on the survival of coronaviruses on stainless steel. At 4°C, infectious virus persisted for as long as 28 days, and the lowest level of inactivation occurred at 20% RH. Inactivation was more rapid at 20°C than at 4°C at all humidity levels; the viruses persisted for 5 to 28 days, and the slowest inactivation occurred at low RH. Both viruses were inactivated more rapidly at 40°C than at 20°C. The relationship between inactivation and RH was not monotonic, and there was greater survival or a greater protective effect at low RH (20%) and high RH (80%) than at moderate RH (50%). There was also evidence of an interaction between AT and RH. The results show that when high numbers of viruses are deposited, TGEV and MHV may survive for days on surfaces at ATs and RHs typical of indoor environments. TGEV and MHV could serve as conservative surrogates for modeling exposure, the risk of transmission, and control measures for pathogenic enveloped viruses, such as SARS-CoV and influenza virus, on health care surfaces

Evaluation of Three Different Selective Media for Enumeration of Clostridium perfringens in Untreated and Treated Wastewater

Current and emerging legislation in North Carolina and other regions calls for the enumeration of Clostridium perfringens as a surrogate indicator for protozoan parasites in various types of waters. Past studies that have evaluated selective media for the detection of this bacterium have provided limited, conflicting, and inconclusive results. In this study, membrane filtration was used to enumerate C. perfringens as culturable spores or total culturable cells in 19 samples of untreated and 25 samples of partially treated wastewaters on 3 candidate media, Tryptose Sulfite Cycloserine Agar (TSC), CP ChromoSelect Agar (CPCS), and membrane Clostridium perfringens Agar (m-CP) in parallel, and the results were compared. Presumptive isolates from each agar were further subjected to phenotypic confirmation tests for acid phosphatase production and stormy fermentation to further determine the performance of each agar. The CPCS agar was determined to have the highest enumerative capacity of total C. perfringens cells when compared to both TSC agar and m-CP agar (p-value < 0.05), but there was no significant difference in its ability to detect spores when compared to TSC agar (p-value > 0.05). The overall specificity of CPCS agar as determined by agreement of results from both confirmation tests was 0.81, while the specificity of TSC agar was only 0.28. Based on its performance, ease of preparation and use and consistency of colony characteristics, CPCS agar is recommended as the preferred medium for C. perfringens enumeration in wastewater

A Review of Chitosan as a Coagulant of Health-Related Microorganisms in Water and Wastewater

The coagulation and flocculation properties of chitosan, an organic biopolymer derived from chitin, have been researched as an alternative to synthetic polymers and inorganic metal salt coagulants currently used in water and wastewater treatment. In an effort to encourage further research into the practical uses of chitosan as green chemistry in water and wastewater treatment and to promote the efficacious removal of microbial contaminants in drinking and wastewater, we have summarized the current state of research pertaining to the treatment of microorganisms in water and wastewater. A search of PubMed revealed 720 possible titles and abstracts, of which 44 full-text articles were identified as matching the eligibility criteria for inclusion in this systematic review. Results are presented based on the type of water matrix treated (i.e., drinking water, wastewater, and recreational waters) and a summary table providing details on the types and forms of chitosan utilized and the treatment mechanisms and processes described in the study. We find chitosan to be an effective coagulant, flocculant, and adsorbent for removing microbes from water and wastewater; some modified forms of chitosan can inactivate microbes and achieve disinfection, such as those containing metals like silver and antimicrobial chemicals like quaternary ammonium compounds or other strong oxidants, and use with filtration or electrochemical processes can achieve extensive reductions in microbes to meet performance targets of the World Health Organization

Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment

The World Health Organization (WHO) reports that two billion people worldwide lack access to safely managed water sources, including 1.2 billion who already have access to improved water sources. In many countries, household point-of-use (POU) water-treatment options are used to remove or deactivate microorganisms in water, but not all POU technologies meet WHO performance requirements to achieve safe drinking water. To improve the effectiveness of POU technologies, the use of multiple treatment barriers should be used as a way to increase overall treatment performance. The focus of this research is to evaluate multiple barrier treatment using chitosan, an organic coagulant–flocculant, to improve microbial and turbidity reductions in combination with sand filtration. Bench-scale intermittently operated sand filters with 16 cm layers of sands of two different grain sizes representing slow and rapid sand filters were dosed daily over 57 days with microbially spiked surface water volumes corresponding to household use. E. coli bacteria and MS2 coliphage virus reductions were quantified biweekly (N = 17) using culture methods. Bacteria and virus removals were significantly improved over sand filtration without chitosan pretreatment (Wilcoxon Rank-Sum, p < 0.05). When water was pretreated at an optimal chitosan dose of 10 mg/L followed by sand filtration, log10 reductions in bacteria and viruses met the two-star WHO performance level of effectiveness. Microbial and turbidity reductions generally improved over the filter operating period but showed no trends with filtration rates

Environmental monitoring of antimicrobial resistant bacteria in North Carolina water and wastewater using the WHO Tricycle protocol in combination with membrane filtration and compartment bag test methods for detecting and quantifying ESBL E. coli

Antimicrobial resistance (AMR) threatens human and animal health; effective response requires monitoring AMR presence in humans, animals, and the environment. The World Health Organization Tricycle Protocol (WHO TP) standardizes and streamlines global AMR monitoring around a single indicator organism, extended-spectrum-β-lactamase-producing Escherichia coli (ESBL-Ec). The WHO TP culture-based method detects and quantifies ESBL-Ec by spread-plating or membrane filtration on either MacConkey or TBX agar (supplemented with cefotaxime). These methods require laboratories and trained personnel, limiting feasibility in low-resource and field settings. We adapted the WHO TP using a simplified method, the compartment bag test (CBT), to quantify most probable numbers (MPN) of ESBL-Ec in samples. CBT methods can be used correctly in the field by typical adults after a few hours’ training. We collected and analyzed municipal wastewater, surface water, and chicken waste samples from sites in Raleigh and Chapel Hill, NC over an 8-month period. Presumptive ESBL-Ec were quantified using MF on TBX agar supplemented with cefotaxime (MF+TBX), as well as using the CBT with chromogenic E. coli medium containing cefotaxime. Presumptive ESBL-Ec bacteria were isolated from completed tests for confirmation and characterization by Kirby Bauer disk diffusion tests (antibiotic sensitivity) and EnteroPluri biochemical tests (speciation). Both methods were easy to use, but MF+TBX required additional time and effort. The proportion of E. coli that were presumptively ESBL in surface water samples was significantly greater downstream vs upstream of wastewater treatment plant (WWTP) outfalls, suggesting that treated wastewater is a source of ESBL-Ec in some surface waters. The CBT and MF+TBX tests provided similar (but not identical) quantitative results, making the former method suitable as an alternative to the more complex MF+TBX procedure in some applications. Further AMR surveillance using MF+TBX and/or CBT methods may be useful to characterize and refine their performance for AMR monitoring in NC and elsewhere