Microbial Water Quality Management Research Articles

Innovative microbial water quality management in water distribution systems using in-pipe hydropowered UV disinfection: envisioning futuristic water-energy systems

ABSTRACT Hydropower UV disinfection has not been explored as a possible alternative for off-grid disinfection. Hydropowered UV LED technology was developed using off-the-shelf UV-C LEDs and pico – and femto-scale hydro turbine generators and evaluated across point-of-use relevant flow rates. Commercially available UV LED flow through reactors were subjected to microorganism challenge testing with 3 power schemes: wall-plug, hydropower, and hydropower-charged battery. UV LEDs powered by hydropower-charged battery demonstrated similar disinfection as wall-plug powered UV LEDs, achieving 0.5-1.8 MS2 log10 reduction at flow rates 0.5-2.3 L min−1, corresponding to reduction equivalent doses (RED) up to 16 or 30 mJ/cm2 for 254 and 285 nm, respectively. With hydropowered UV LEDs alone, MS2 log10 reduction decreased to <0.3 log10 reduction due to an underperforming and grossly inefficient turbine, with RED of 8 or 18 mJ/cm2 for 254 and 285 nm, respectively. Assessment of existing markets of UV disinfection systems and pico-hydro turbines demonstrated that hydropowered UV systems are already theoretically feasible for scales at point-of-entry (POE) and above. Economic feasibility will improve if turbines and/or UV system efficiencies improve. Prototype hydropower UV LED systems ranged from $145 to 220 depending on the UV LED reactor, and the battery system added $81. This study demonstrates the practicality of sustainable, renewable energy POU UV disinfection technology that can benefit decentralised, off-grid, rural and remote communities. The system may also scale up to provide renewable energy disinfection at larger scales, such as buildings and water distribution systems, for protecting human health in highly populated areas.

Impact of Freeze-Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses.

Characterising faecal indicator organism (FIO) survival in the environment is important for informing land management and minimising public health risk to downstream water users. However, key gaps in knowledge include understanding how wildlife contribute to catchment-wide FIO sources and how FIO survival is affected by low environmental temperatures. The aim of this study was to quantify E. coli and intestinal enterococci die-off in dairy cow versus red deer faecal sources exposed to repeated freeze–thaw cycles under controlled laboratory conditions. Survival of FIOs in water exposed to freeze–thaw was also investigated to help interpret survival responses. Both E. coli and intestinal enterococci were capable of surviving sub-freezing conditions with the faeces from both animals able to sustain relatively high FIO concentrations, as indicated by modelling, and observations revealing persistence in excess of 11 days and in some cases confirmed beyond 22 days. Die-off responses of deer-derived FIOs in both faeces and water exposed to low temperatures provide much needed information to enable better accounting of the varied catchment sources of faecal pollution and results from this study help constrain the parameterisation of die-off coefficients to better inform more integrated modelling and decision-making for microbial water quality management.

Rainfall-driven E. coli transfer to the stream-conduit network observed through increasing spatial scales in mixed land-use paddy farming karst terrain

Karst aquifers have distinctive hydrology and supply 25% of the world’s population with drinking water, making them a critical geological setting for understanding and managing microbial water pollution. Rainfall causes elevated concentrations and loading of faecal microorganisms, e.g. E. coli, in catchment surface and groundwater systems, increasing the risk of human exposure to faecally-contaminated water. However, effective management of microbial water quality in complex karst catchments is constrained by limited understanding of E. coli - discharge responses to rainfall. We analysed how rainfall events of varying magnitude (2.4–100 mm) control E. coli-discharge dynamics at increasing spatial scales in a mixed land-use karst catchment in southwest China. During the wet season, hourly water sampling was undertaken throughout five storm events to characterise in high detail E. coli emergence with resulting flow across multiple sites of varying catchment area, stream order, and land-use. E. coli concentration was found to increase by 1–3 orders of magnitude following rainfall events. Maximum E. coli concentration and speed of E. coli recession were influenced by rainfall (amount, intensity), timing of agricultural activities, and position in the hydrological system. For high intensity events ∼90% of the cumulative E. coli export occurred within 48 h. E. coli concentration increased with increasing discharge at all sites. E. coli concentration at low discharge was higher in the headwaters than at the catchment outlet, while the rate of increase in E. coli concentration with increasing discharge appears to follow the opposite trend, being higher at the catchment outlet than the headwaters. This was attributed to the decreasing flow path gradient and increasing degree of development of the fissure network, but further event monitoring at varying catchment scales is required to confirm this relationship. The results provide novel insight into how rainfall characteristics combine with land-use and catchment hydrology to control E. coli export in karst landscapes.

Quantitative Microbial Risk Assessment of Swimming in Sewage Impacted Waters Using CrAssphage and Pepper Mild Mottle Virus in a Customizable Model

Fecal indicator bacteria currently employed for microbial water quality management are poor representatives of viruses. Viral water quality indicators have recently been proposed based on the human gut bacteriophage crAssphage and the food virus pepper mild mottle virus (PMMoV) due to their high abundance in sewage and association to human waste. Here, we develop a model relating crAssphage and PMMoV abundance to the risk of swimmer illness in a recreational water contaminated with fresh, untreated domestic sewage. This model, entitled QMRAswim, is available via a Web-based user interface and is generalizable to any indicator or pathogen. The majority of predicted illnesses from exposure to untreated domestic sewage-contaminated water were attributable to viruses, primarily norovirus. The mean crAssphage and PMMoV concentrations correlating with 30 illnesses per 1000 bathers were 4648 GC/100 mL and 5054 GC/100 mL, respectively, approximately 50 times their standard detection limit. This study reaffirms th...

Pepper mild mottle virus: Agricultural menace turned effective tool for microbial water quality monitoring and assessing (waste)water treatment technologies.

Domestic wastewater pollution in environmental waters or water reuse supplies represents a threat to public health because of high concentrations of diverse pathogens associated with human excreta [1]. Since it is difficult to directly measure waterborne pathogens of concern, microbial water quality monitoring efforts often use surrogates or indicator organisms that are easily detected and whose presence reflects pathogen persistence [2]. Here, we describe an unconventional viral indicator of wastewater pollution, pepper mild mottle virus (PMMoV), a plant pathogen that was first proposed as a water quality indicator in 2009 [3] and promises to improve microbial water quality management worldwide [4].

High resolution characterisation of E. coli proliferation profiles in livestock faeces

Agricultural intensification can lead to high volumes of livestock faeces being applied to land, either as solid or liquid manures or via direct defecation, and can result in reservoirs of faecal indicator organisms (FIOs) persisting within farmland. Understanding the survival of FIOs, e.g. E. coli, in agricultural environments, and in particular within different livestock faeces, is key to developing catchment management practices for the protection of ecosystem services provided by clean water. Frequently, controlled laboratory studies, under constant temperature regimes, are used to determine the impact of environmental factors on E. coli persistence in livestock faeces; however, such studies oversimplify the diurnal variations and interactions of real world conditions. The aim of this study was to investigate the survival of E. coli using a controlled environment facility, which simulated diurnal variation of temperatures typically experienced during a British spring and summer. The approach provided a comparison of E. coli persistence profiles within faeces of sheep, beef cattle and dairy cattle to allow novel interpretations of E. coli regrowth patterns in contrasting livestock faeces in the period immediately post-defecation. Thus, the coupling of a tightly controlled environment facility with high resolution monitoring enabled the development of a new non-linear, asymptotic description of E. coli proliferation in livestock faeces, with increased potential for E. coli growth observed during warmer temperatures for all livestock types. While this study focused on temperatures typical of the UK, the occurrence of a phase of E. coli regrowth has implications for microbial water quality management worldwide.

To what extent does hydrological connectivity control dynamics of faecal indicator organisms in streams? Initial hypothesis testing using a tracer-aided model

The role of hydrological connectivity in driving the dynamics of faecal indicator organisms (FIOs) in streams is poorly characterised. Here, we demonstrate how a tracer-aided hydrological model can be used within a coupled modelling approach to explore the role of connectivity in governing stream faecal coliform (FC) dynamics. To do so, we tested a hypothesis that in northern upland catchments, the dynamics of hydrological connectivity between major landscape units (hillslopes and riparian zone) and the stream exert a dominant control on stream FC loads by facilitating generation of runoff-driven FC fluxes. This hypothesis was conceptualised within a simple FC model that was coupled to a tracer-aided hydrological model developed for a small (3.2 km2) data-rich catchment in NE Scotland. The model was dual-calibrated to daily discharge and stable isotope data for the period August 2008 to September 2009; stream FC loads were also simulated but not used as a calibration target. Behavioural models successfully captured the general dynamics of the discharge and isotope data (average Kling-Gupta efficiencies of 0.72 and 0.53, respectively), providing confidence in the realism of simulated hydrological processes. The models simulated a seasonally-varying role of connectivity in driving stream FC loads. In summer, connectivity of the catchment hillslope was crucial in providing a source of FC to the riparian zone for transfer to the stream; this countered the decline in fresh FC input to the riparian zone in summer which reflected the seasonal movement of red deer (the principal source of FC) onto higher ground. In winter when this seasonal movement caused FC to be predominantly stored in the riparian zone, simulated hillslope connectivity primarily provided water to the riparian zone that permitted increased runoff generation and associated mobilisation of FC. Comparison of observed and simulated stream FC loads revealed model performance to be variable (R2 range: 0–0.34). The better performance of the model in summer was consistent with hydrological connectivity being a dominant control on stream FC loads at this time. However, failure of the model to capture low FC loads in winter indicated that additional processes not considered in the model may also govern stream FC dynamics during this period. Incorporating the impact of freeze-thaw cycles on FC mortality, or a dilution effect of hillslope connectivity in winter, could be potential next steps in refining the hypothesis conceptualised in the FC model presented here. The novel coupled modelling approach used in this study successfully allowed a hypothesised role of connectivity in driving stream FC dynamics to be tested, contextualised by the accuracy of discharge and isotope-tracer simulations as indicators of hydrological process realism. Therefore, coupling FIO and tracer-aided hydrological models has clear promise for furthering understanding of FIO dynamics, which is a vital precursor to the successful management of microbial water quality. Based on the experiences in this study, a “roadmap” for the future development and application of coupled approaches is also presented.

Microbial water quality management of dental unit water lines at a dental school

Contaminated dental unit water lines (DUWLs) are a possible source for spreading micro-organisms in dental practices. This study reports the microbial load of the water from DUWLs of a large dental school over time. The water quality of 231 dental chairs was tested three times over 1.5 years; 175 DUWLs at student clinics and 56 DUWLs at staff clinics. DUWLs at the staff clinics met the Dutch requirement of 100colony-forming units/mL. An increasing number of DUWLs at the student clinics complied with this requirement, indicating that the local protocols are adequate but that compliance can be improved.

Predicting microbial water quality with models: Over-arching questions for managing risk in agricultural catchments

The application of models to predict concentrations of faecal indicator organisms (FIOs) in environmental systems plays an important role for guiding decision-making associated with the management of microbial water quality. In recent years there has been an increasing demand by policy-makers for models to help inform FIO dynamics in order to prioritise efforts for environmental and human-health protection. However, given the limited evidence-base on which FIO models are built relative to other agricultural pollutants (e.g. nutrients) it is imperative that the end-user expectations of FIO models are appropriately managed. In response, this commentary highlights four over-arching questions associated with: (i) model purpose; (ii) modelling approach; (iii) data availability; and (iv) model application, that must be considered as part of good practice prior to the deployment of any modelling approach to predict FIO behaviour in catchment systems. A series of short and longer-term research priorities are proposed in response to these questions in order to promote better model deployment in the field of catchment microbial dynamics.

Solid Manure As a Source of Fecal Indicator Microorganisms: Release under Simulated Rainfall.

Understanding and quantifying microbial release from manure is a precondition to estimation and management of microbial water quality. The objectives of this work were to determine the effects of rainfall intensity and surface slope on the release of Escherichia coli, enterococci, total coliforms, and dissolved chloride from solid dairy manure and to assess the performance of the one-parametric exponential model and the two-parametric Bradford-Schijven model when simulating the observed release. A controlled-intensity rainfall simulator induced 1 h of release in runoff/leachate partitioning boxes at three rainfall intensities (30, 60, and 90 mm h(-1)) and two surface slopes (5% and 20%). Bacterial concentrations in initial release were more than 1 order of magnitude lower than their starting concentrations in manure. As bacteria were released, they were partitioned into runoff and leachate at similar concentrations, but in different volumes, depending on slope. Bacterial release occurred in two stages that corresponded to mechanisms associated with release of manure liquid- and solid-phases. Parameters of the two models fitted to the bacterial release dependencies on rainfall depth were not significantly affected by rainfall intensity or slope. Based on model performance tests, the Bradford-Schijven model is recommended for simulating bacterial release from solid manure.

A comparison of the regulatory frameworks governing microbial testing of drinking water in three Canadian provinces

In Canada, the provinces have primary responsibility for water management, including drinking water management; the federal government has comparatively more limited water-related responsibilities. Currently, Canada does not have a harmonized federal drinking water strategy or law (although it does have non-binding guidelines); thus provinces have developed different approaches to drinking water management. In this study, key features of the current regulatory frameworks for microbial testing in drinking water quality management are examined in Canada’s three most populous provinces – British Columbia, Ontario and Quebec. Salient regulatory features including the types of drinking water samples, water quality standards, testing frequency and system size are described and compared. Distinct differences were found in provincial approaches to drinking water quality assessment, and microbial water quality management is variable not only among, but also within, provinces. This finding of inter- and intra-province variability in drinking water quality management shows that these three provinces are approaching similar challenges in different ways. In turn, these different approaches demonstrate that regulatory frameworks can be adapted in response to drinking water management challenges. Regulatory frameworks should be flexible and adaptable to new knowledge and scientific developments, such as molecular testing methods, in order to facilitate their translation into water management tools.

Water Quality Management withBacillusspp. in the High-Density Culture of Red-Parrot FishCichlasoma citrinellum×C. synspilum

Abstract Red-parrot fish (male midas cichlid Cichlasoma citrinellum × female redhead cichlid C. synspilum) is one of the most important tropical fish in Taiwan. In high-density culture, poor water quality often induces emaciation, gill filament ulceration, gill opercula malformation, and high mortality. In an effort to solve these problems in a high-density culture environment, two bacteria, Bacillus subtilis and B. megaterium, were added to the recirculating-water systems of the grow-out facilities. The addition of Bacillus held total ammonia nitrogen concentrations to 5.4 mg/L or less and chemical oxygen demands to 40.8 mg/L or less; it also maintained the transparency of the recirculated aquarium water at 30–50 cm. Survival rate and quality of fish were dramatically improved with this microbial water quality management process. This method is easy to perform and can be adapted effectively in the commercial culture of red-parrot fish.

Management of microbial water quality: new perspectives for developing areas

A case study indicated that the high number of pathogenic micro-organisms in the Rietspruit, South Africa, can impact water uses. Factors contributing to high microbial numbers are high density population with limited services provided per site, sabotage of the sewage reticulation system, lack of money and management skills to provide the essential services and limited integrated development planning for the catchment. Due to non-steady state conditions in the catchment, the specific use and physical characteristics of the river and the difficulty in determining flow, the usefulness of a steady-state stream water quality model as a management tool is limited. Determining the decay rate of micro-organisms by means of chamber studies, may be a first step to predict microbial water quality. Involving the community in preventing microbial pollution may be a more appropriate tool for microbial water quality management in developing areas.

Estimation of the fate of microbial water quality contaminants in a South African river

The aim of this study was to evaluate the validity of assumptions, regarding assimilative capacity for microbial contaminants, implicit in microbial water quality management in South Africa. A one dimensional steady state stream water quality model, assuming first order decay of microbial water quality variables, was employed in an attempt to describe and predict microbial water quality in the chosen catchment. Based on the faecal coliform counts the results indicated that the processes of decay and dilution were inadequate to yield water quality which complied with South African and international guidelines for the domestic and recreational use of water. It was also found that a first order decay model can, with fairly limited data, allow a manager to investigate different microbial water quality scenarios in a cost-effective manner.

Management of microbial water quality: New perspectives for developing areas

A case study indicated that the high number of pathogenic micro-organisms in the Rietspruit, South Africa, can impact water uses. Factors contributing to high microbial numbers are high density population with limited services provided per site, sabotage of the sewage reticulation system, lack of money and management skills to provide the essential services and limited integrated development planning for the catchment.Due to non-steady state conditions in the catchment, the specific use and physical characteristics of the river and the difficulty in determining flow, the usefulness of a steady-state stream water quality model as a management tool is limited. Determining the decay rate of micro-organisms by means of chamber studies, may be a first step to predict microbial water quality. Involving the community in preventing microbial pollution may be a more appropriate tool for microbial water quality management in developing areas.

Estimation of the fate of microbial water quality contaminants in a South African river

The aim of this study was to evaluate the validity of assumptions, regarding assimilative capacity for microbial contaminants, implicit in microbial water quality management in South Africa. A one dimensional steady state stream water quality model, assuming first order decay of microbial water quality variables, was employed in an attempt to describe and predict microbial water quality in the chosen catchment. Based on the faecal cofifotm counts the results indicated that the processes of decay and dilution were inadequate to yield water quality which complied with South African and international guidelines for the domestic and recreational use of water. It was also found that a first order decay model can, with fairly limited data, allow a manager to investigate different microbial water quality scenarios in a cost-effective manner.