Regrowth of enterococci indicator in an open recycled-water impoundment

Proliferation of microalgae and enterococci in the Lake Okeechobee, St. Lucie, and Loxahatchee watersheds

This study is an analysis of relationships between microalgae (measured as chlorophyll a) and the fecal indicator bacteria enterococci. Microalgae blooms and enterococci exceedances have been occurring in Florida's recreational waterways for years. More recently, this has become a management concern as microalgae blooms have been attributed to potentially toxic cyanobacteria, and enterococci exceedances link to human infection/illness. Since both the microalgal blooms and bacterial exceedances occur in regions that receive managed freshwater releases from Lake Okeechobee, we hypothesized that both the blooms and exceedances are related to excess nutrients from the lake. Two experimental sites, on Lake Okeechobee and the St. Lucie River (downstream of the lake), plus a control site on the Loxahatchee River (which does not receive lake flow) were evaluated. The hypothesis was evaluated through three study components: 1) analysis of available long-term data from local environmental databases, 2) a year-long monthly sampling and analysis of chlorophyll a, enterococci, nutrients, and physical-chemical data, and 3) microcosm experiments with altered water/sediment conditions. Results support the hypothesis that excess nutrients play a role in both chlorophyll a and enterococci levels. For the St. Lucie River, analyses indicate that chlorophyll a correlated significantly with total Kjeldahl nitrogen (TKN) (R² = 0.30, p = 0.008) and the strongest model for enterococci included nitrate-nitrite, TKN, total phosphorus, orthophosphorus, and turbidity in our long-term analysis (n = 39, R² = 0.83, p ≤ 0.001). The microcosm results indicated that chlorophyll a and enterococci only persisted for 36 h in water from all sources, and that sediments from Lake Okeechobee may have allowed for sustained levels of chlorophyll a and enterococci levels. Overall similarities were observed in chlorophyll a and enterococci relationships with nutrient concentrations regardless of a Lake Okeechobee connection, as underscored by a study of flow out of the lake and downstream areas. This suggests that both nutrient-rich lake water and untreated surface water runoff contribute to microalgae blooms and enterococci exceedances in southeast Florida.

Poikilothermic Animals as a Previously Unrecognized Source of Fecal Indicator Bacteria in a Backwater Ecosystem of a Large River

Quantitative information regarding the presence of Escherichia coli, intestinal enterococci, and Clostridium perfringens in poikilotherms is notably scarce. Therefore, this study was designed to allow a systematic comparison of the occurrence of these standard fecal indicator bacteria (SFIB) in the excreta of wild homeothermic (ruminants, boars, carnivores, and birds) and poikilothermic (earthworms, gastropods, frogs, and fish) animals inhabiting an alluvial backwater area in eastern Austria. With the exception of earthworms, the average concentrations of E. coli and enterococci in the excreta of poikilotherms were equal to or only slightly lower than those observed in homeothermic excreta and were 1 to 4 orders of magnitude higher than the levels observed in the ambient soils and sediments. Enterococci reached extraordinarily high concentrations in gastropods. Additional estimates of the daily excreted SFIB (E. coli and enterococcus) loads (DESL) further supported the importance of poikilotherms as potential pollution sources. The newly established DESL metric also allowed comparison to the standing stock of SFIB in the sediment and soil of the investigated area. In agreement with its biological characteristics, the highest concentrations of C. perfringens were observed in carnivores. In conclusion, the long-standing hypothesis that only humans and homeothermic animals are primary sources of SFIB is challenged by the results of this study. It may be necessary to extend the fecal indicator concept by additionally considering poikilotherms as potential important primary habitats of SFIB. Further studies in other geographical areas are needed to evaluate the general significance of our results. We hypothesize that the importance of poikilotherms as sources of SFIB is strongly correlated with the ambient temperature and would therefore be of increased significance in subtropical and tropical habitats and water resources.IMPORTANCE The current fecal indicator concept is based on the assumption that the standard fecal indicator bacteria (SFIB) Escherichia coli, intestinal enterococci, and Clostridium perfringens multiply significantly only in the guts of humans and other homeothermic animals and can therefore indicate fecal pollution and the potential presence of pathogens from those groups. The findings of the present study showed that SFIB can also occur in high concentrations in poikilothermic animals (i.e., animals with body temperatures that vary with the ambient environmental temperature, such as fish, frogs, and snails) in an alluvial backwater area in a temperate region, indicating that a reconsideration of this long-standing indicator paradigm is needed. This study suggests that poikilotherms must be considered to be potential primary sources of SFIB in future studies.

Opening the black box of spring water microbiology from alpine karst aquifers to support proactive drinking water resource management

Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well-defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm-associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high-discharge situations, surface-associated microbes and nutrients such as from soil habitats or human settlements-potentially containing fecal-associated pathogens as the most critical water-quality hazard-may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near-real-time online water quality monitoring, microbial source tracking (MST) and MST-guided quantitative microbial-risk assessment (QMRA) are examples of the proposed analytical tools. In this context, this overview article also provides a short introduction to recently emerging methodologies in microbiological diagnostics to support reading for the practitioner. Finally, the article highlights future research and development needs. This article is categorized under: 1Engineering Water > Water, Health, and Sanitation2Science of Water > Water Extremes3Water and Life > Nature of Freshwater Ecosystems.

Evaluation of the microbiological quality of reclaimed water produced from a lagooning system

The use of lagooning as a complementary natural method of treating secondary effluents of wastewater treatment plants has been employed as an affordable and easy means of producing reclaimed water. However, using reclaimed water for some purposes, for example, for food irrigation, presents some risks if the effluents contain microbial pathogens. Classical bacterial indicators that are used to assess faecal contamination in water do not always properly indicate the presence of bacterial or viral pathogens. In the current study, the presence of faecal indicator bacteria (FIB), heterotrophic bacterial counts (HBC), pathogens and opportunistic pathogens, such as Legionella spp., Aeromonas spp., Arcobacter spp., free-living amoeba (FLA), several viral indicators (human adenovirus and polyomavirus JC) and viral pathogens (noroviruses and hepatitis E virus) were analysed for 1 year in inlet and outlet water to assess the removal efficiency of a lagooning system. We observed 2.58 (1.17-4.59) and 1.65 (0.15-3.14) log reductions in Escherichia coli (EC) and intestinal enterococci (IE), respectively, between the inlet and outlet samples. Genomic copies of the viruses were log reduced by 1.18 (0.24-2.93), 0.64 (0.12-1.97), 0.45 (0.04-2.54) and 0.72 (0.22-2.50) for human adenovirus (HAdV), JC polyomavirus (JCPyV) and human noroviruses (NoV GI and GII), respectively. No regrowth of opportunistic pathogens was observed within the system. FLA, detected in all samples, did not show a clear trend. The reduction of faecal pathogens was irregular with 6 out of 12 samples and 4 out of 12 samples exceeding the EC and IE values, specified in the Spanish legislation for reclaimed water (RD 1620/2007). This data evidences that there is a need for more studies to evaluate the removal mechanisms of lagooning systems in order to optimize pathogen reduction. Moreover, surveillance of water used to irrigate raw edible vegetables should be conducted to ensure the fulfilment of the microbial requirements for the production of safe reclaimed water.

Bacterial regrowth in water reclamation and distribution systems revealed by viable bacterial detection assays

Microbial regrowth needs to be managed during water reclamation and distribution. The aim of present study was to investigate the removal and regrowth of Escherichia coli (E. coli) and Salmonella in water reclamation and distribution system by using membrane integrity assay (PMA-qPCR), reverse transcriptional activity assay (Q-RT-PCR) and culture-based assay, and also to evaluate the relationships among bacterial regrowth, and environmental factors in the distribution system. The results showed that most of the water reclamation processes potentially induced bacteria into VBNC state. The culturable E. coli and Salmonella regrew 1.8 and 0.7 log10 in distribution system, which included reactivation of bacteria in the viable but non-culturable (VBNC) state and reproduction of culturable bacteria. The regrowth of culturable E. coli and Salmonella in the distribution system mainly depended on the residual chlorine levels, with correlations (R(2)) of -0.598 and -0.660. The abundances of membrane integrity and reverse transcriptional activity bacteria in reclamation effluents had significant correlations with the culturable bacteria at the end point of the distribution system, demonstrating that PMA-qPCR and Q-RT-PCR are sensitive and accurate tools to determine and predict bacterial regrowth in water distribution systems. This study has improved our understanding of microbial removal and regrowth in reclaimed water treatment and distribution systems. And the results also recommended that more processes should be equipped to remove viable bacteria in water reclamation plants for the sake of inhibition microbial regrowth during water distribution and usages.

Wastewater treatment by a modular, domestic-scale reedbed system for safe horticultural irrigation

The aim of the study was to assess the sequential treatment performance of a commercial, domestic-scale modular reedbed system intended to provide safe horticultural irrigation water. Previously only mechanical treatment systems involving forced aeration with subsequent disinfection, usually by tablet-chlorination, had been accredited in Australia. The modular design of the hybrid, subsurface-flow reedbed system offered 5 control points where monitoring and management of the treatment train could be carried out. Ten chemical parameters (chemical and biochemical oxygen demand, total organic carbon, total Kjeldahl nitrogen, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, dissolved oxygen percentage saturation and suspended solids) and 4 microbial parameters (total coliform, Escherichia coli, enterococci and Clostridium perfringens) reached satisfactory levels as a result of the treatment process. Health requirements for safe horticultural irrigation were met by the outlet of the second reedbed, providing a high level of treatment-backup capacity in terms of the remaining 2 reedbeds. This suggested that chlorination was a redundant backup precaution in treating irrigation water to the acceptable regional guideline level for all horticultural uses, including the spray irrigation of salad crops eaten raw.

Distribution and persistence of Escherichia coli and Enterococci in stream bed and bank sediments from two urban streams in Houston, TX

The purpose of this research was to determine if Escherichia coli and enterococci in streambed and bank sediments from two urban bayous, Buffalo Bayou and White Oak Bayou, in Houston, TX, USA are a significant source of the chronically high levels of these bacteria in the overlying water. The watersheds of the bayous lie within highly urbanized areas of Greater Houston and there is primary recreational contact with the public. Extensive sampling of the watersheds was conducted from 2008 to 2010. Both fecal indicator bacteria were found at ≥ 10(4)MPNgdry wt.(-1) concentrations in the upper 1cm of sediment cores with declines by orders of magnitude at 15 and 30 cm sediment horizons and in some cases 60 cm, but, nonetheless, indicating that they can remain viable even at depth. No interannual variation was observed. And, there was no correlation with percent organic matter, however there was moderate correlation (R(2)=0.12; p=0.001) of E. coli with sediment moisture. In sediments, most E. coli and enterococci in Buffalo Bayou (76%) and White Oak Bayou (87.5%) were associated with fine sand grains (60 to 250 μm). In the water column, E. coli was associated, in roughly equal percentages, with particle sizes <10, 10-25, 25-63, and ≥ 63 μm (21.9, 25.6, 30.4, and 32.9%, respectively). Enterococci were mostly attached to particle sizes in the ranges of 10-25μm (36.0%) and 25-63 μm (31.1%) as well as ≥ 63 μm (37.7%) (p=0.0001). Fingerprinting of E. coli isolates from both bayous with Rep-PCR and the BOX A1R primer was used to demonstrate translocation of sediments from the upper to lower watersheds.