Faecal indicator organism inputs to watercourses from streamside pastures grazed by cattle: Before and after implementation of streambank fencing.

Faecal indicator organisms (FIOs) are major pollutants in many catchments world-wide, with streamside pastures on livestock farms being potentially significant sources. Hitherto, few empirical studies have quantified FIO fluxes from such areas or investigated streambank fencing (SBF) and other possible mitigation measures. The aim of this two-phase (before/after intervention) study of the effectiveness of SBF was to generate an empirical evidence-base to enable regulatory authorities to make better-informed decisions concerning the implementation of this measure. It was undertaken during the summer bathing season along a 271 m stream reach in the River Tamar catchment, SW England. The study included: cattle distribution surveys; monitoring of changes in E. coli (EC) and intestinal enterococci (IE) concentrations and fluxes down the reach and of concentrations in ditch flow and surface runoff; phage tracer studies of surface runoff from pasture land; and experimental streambed trampling to investigate streambed FIO sources. The results show that cattle spend a disproportionately large amount of time in the watercourse/riparian zone along unfenced streams; identify direct defecation to the stream by wading livestock and the release/mobilisation of FIOs from cowpats by surface runoff from the adjacent pastures at times of high flow as key transmission routes; and demonstrate that FIOs become incorporated within streambed sediments, from which they may subsequently be released by trampling. Partial exclusion of cattle through SBF with a drinking bay greatly reduces the time cattle spend in streams. Total exclusion SBF, with provision of an alternative drinking supply, considerably reduces FIO load inputs to the stream reach, e.g. at times of high flow, which are critical in terms of pollutant fluxes to coastal waters, the mean EC and IE input loads to the reach fell by 0.842 and 2.206 log10, respectively.

Predicting microbial pollution concentrations in UK rivers in response to land use change.

The Water Framework Directive has caused a paradigm shift towards the integrated management of recreational water quality through the development of drainage basin-wide programmes of measures. This has increased the need for a cost-effective diagnostic tool capable of accurately predicting riverine faecal indicator organism (FIO) concentrations. This paper outlines the application of models developed to fulfil this need, which represent the first transferrable generic FIO models to be developed for the UK to incorporate direct measures of key FIO sources (namely human and livestock population data) as predictor variables. We apply a recently developed transfer methodology, which enables the quantification of geometric mean presumptive faecal coliforms and presumptive intestinal enterococci concentrations for base- and high-flow during the summer bathing season in unmonitored UK watercourses, to predict FIO concentrations in the Humber river basin district. Because the FIO models incorporate explanatory variables which allow the effects of policy measures which influence livestock stocking rates to be assessed, we carry out empirical analysis of the differential effects of seven land use management and policy instruments (fiscal constraint, production constraint, cost intervention, area intervention, demand-side constraint, input constraint, and micro-level land use management) all of which can be used to reduce riverine FIO concentrations. This research provides insights into FIO source apportionment, explores a selection of pollution remediation strategies and the spatial differentiation of land use policies which could be implemented to deliver river quality improvements. All of the policy tools we model reduce FIO concentrations in rivers but our research suggests that the installation of streamside fencing in intensive milk producing areas may be the single most effective land management strategy to reduce riverine microbial pollution.

Evaluating short-term changes in recreational water quality during a hydrograph event using a combination of microbial tracers, environmental microbiology, microbial source tracking and hydrological techniques: a case study in Southwest Wales, UK.

Quantitative assessment of multiple sources to short-term variations in recreational water quality, as indexed by faecal indicator organism (FIO) concentrations, is becoming increasingly important with adoption of modern water quality standards and catchment-based water quality management requirements (e.g. the EU Water Framework Directive, Article 11 'Programmes of Measures' and the US Clean Water Act, 'Total Maximum Daily Loads'). This paper describes a study combining microbial tracers, intensive FIO measurement, open channel hydrology and molecular microbial source tracking (MST) to enhance understanding of recreational water quality at Amroth in southwest Wales, UK. Microbial tracers were released from four stream inputs during a moderate hydrograph event. Tracers from two local streams impacted simultaneously with a period of maximum FIO concentrations at the near-shore compliance monitoring site. Connection between these inputs and this site were rapid (9-33 min). Water quality impairment from a more remote stream input followed, 12.85 h after tracer release, sustaining FIO concentrations above desired compliance levels. MST analysis showed dominance of ruminant Bacteroidales genetic markers, associated with agricultural pollution. This integration of tracers and MST offers additional information on the movement and individual sources causing water quality impairment.

Evaluating the operational utility of a Bacteroidales quantitative PCR-based MST approach in determining the source of faecal indicator organisms at a UK bathing water.

Microbial source tracking techniques are used in the UK to provide an evidence-base to guide major expenditure decisions and/or regulatory action relating to sewage disposal. Consequently, it is imperative that the techniques used robustly index faecal indicator organisms (FIOs) that are the regulatory parameters for bathing and shellfish harvesting areas. This study reports a 'field-scale' test of microbial source tracking (MST) based on the quantitative PCR analyses of Bacteroidales 16S rRNA genetic marker sequences. The project acquired data to test the operational utility of quantitative Bacteroidales MST data, comparing it with FIO concentrations in streams, effluents and bathing waters. Overall, the data did not exhibit a consistent pattern of significant correlations between Bacteroidales MST parameters and FIOs within the different sample matrices (i.e. rivers, bathing waters and/or effluents). Consequently, there was little evidence from this study that reported concentrations and/or percentages of human and/or ruminant faecal loadings (that are based on Bacteroidales MST gene copy numbers) offer a credible evidence-base describing FIO contributions to receiving water 'non-compliance'. The study also showed (i) there was no significant attenuation of the Bacteroidales gene copy number 'signal' through the UV disinfection process; and (ii) single non-compliant samples submitted for Bacteroidales MST analysis, do not reliably characterise the balance of faecal loadings due to the high variability in the MST signal observed. At this stage in the development of the MST tool deployed, it would be imprudent to use the percentage human and/or ruminant contributions (i.e. as indicated by MST data acquired at a bathing water) as the sole or principal element in the evidence-base used to guide major expenditure decisions and/or regulatory action.

Microbial source tracking: a forensic technique for microbial source identification?

As the requirements of the Water Framework Directive (WFD) and the US Clean Water Act (USCWA) for the maintenance of microbiological water quality in 'protected areas' highlight, there is a growing recognition that integrated management of point and diffuse sources of microbial pollution is essential. New information on catchment microbial dynamics and, in particular, the sources of faecal indicator bacteria found in bathing and shellfish harvesting waters is a pre-requisite for the design of any 'programme of measures' at the drainage basin scale to secure and maintain compliance with existing and new health-based microbiological standards. This paper reports on a catchment-scale microbial source tracking (MST) study in the Leven Estuary drainage basin, northwest England, an area for which quantitative faecal indicator source apportionment empirical data and land use information were also collected. Since previous MST studies have been based on laboratory trials using 'manufactured' samples or analyses of spot environmental samples without the contextual microbial flux data (under high and low flow conditions) and source information, such background data are needed to evaluate the utility of MST in USCWA total maximum daily load (TMDL) assessments or WFD 'Programmes of Measures'. Thus, the operational utility of MST remains in some doubt. The results of this investigation, using genotyping of Bacteroidetes using polymerase chain reaction (PCR) and male-specific ribonucleic acid coliphage (F + RNA coliphage) using hybridisation, suggest some discrimination is possible between livestock- and human-derived faecal indicator concentrations but, in inter-grade areas, the degree to which the tracer picture reflected the land use pattern and probable faecal indicator loading were less distinct. Interestingly, the MST data was more reliable on high flow samples when much of the faecal indicator flux from catchment systems occurs. Whilst a useful supplementary tool, the MST information did not provide quantitative source apportionment for the study catchment. Thus, it could not replace detailed empirical measurement of microbial flux at key catchment outlets to underpin faecal indicator source apportionment. Therefore, the MST techniques reported herein currently may not meet the standards required to be a useful forensic tool, although continued development of the methods and further catchment scale studies could increase confidence in such methods for future application.

Predicting faecal indicator fluxes using digital land use data in the UK's sentinel Water Framework Directive catchment: the Ribble study.

The Ribble drainage basin is the single UK sentinel study area chosen for examining the implementation of the EU Water Framework Directive (WFD 20/60/EC). The study which has generated the data for this paper was initiated to quantify 'catchment-derived' fluxes of faecal indicators originating from both point and diffuse sources to inform the competent authorities on the potential for, and prioritization of, further options for reducing the faecal indicator loadings to this crucial coastal environment. It represents the first UK drainage basin-scale 'profile' of faecal indicator sources as recommended by WHO [1999. Health Based Monitoring of Recreational Waters: The Feasibility of a New Approach; the "Annapolis Protocol". World Health Organisation Geneva, Switzerland; 2003. Guidelines for Safe Recreational-Water Environments Volume 1: Coastal and Fresh-Waters. World Health Organisation Geneva, Switzerland] and incorporated into current drafts of the revised Bathing Water Directive [Anon, 2004. Council of the European Communities Amended proposal for a Directive of the European Parliament and of the Council concerning the management of bathing water quality. Brussels 23rd June]. This paper focuses on the relationships between land use and faecal indicator organism concentrations in surface waters within this very large drainage basin (1583 km2) containing some extensive urban areas. A geographical information system comprising readily available digital elevation, remotely sensed land cover and digital map data was used to generate the land use variables for subcatchments draining to 41 locations across the study area. Presumptive concentrations of coliforms, Escherichia coli and enterococci (colony forming unit (cfu) 100 ml(-1)) were measured at each location on at least 20 occasions over a 44-day period within the 2002 bathing season. The sampling programme targeted hydrograph events. Hydrometric records were used to allocate results as either base flow or high flow. At each site, geometric mean faecal indicator organism concentrations were significantly elevated at high flow compared to base flow. Stepwise regression modelling produced statistically significant models predicting geometric mean base and high-flow faecal indicator organism concentrations from land use variables (r2: 49.5-68.1%). The dominant predictor variable in each case was the proportion of built-up land in subcatchments, suggesting that this land use type, with associated sewage-related inputs, is a critical source of faecal indicator organisms in this drainage basin.

Sustainable reduction in the flux of microbial compliance parameters from urban and arable land use to coastal bathing waters by a wetland ecosystem produced by a marine flood defence structure.

'Natural' treatment systems such as wetlands and reed beds have been proposed as sustainable means of reducing fluxes of faecal indicator organisms (FIOs) to recreational and shellfish harvesting waters. This is because FIO fluxes to coastal waters from both point (effluent) and diffuse (catchment) sources can cause non-compliance with microbiological standards for bathing and shellfish harvesting waters. The Water Framework Directive requires competent authorities in the member states to manage both point and diffuse sources of FIOs in an integrated manner to achieve compliance with 'good' water quality as defined in a series of daughter Directives. This study was undertaken to investigate the relative sources of FIOs to the popular bathing waters around Clacton, UK. In this predominantly arable (mainly cereal cropping) farming area, the principal land use predictor, explaining 76% of the variance in geometric mean presumptive Escherichia coli concentration at sub-catchment outlets during the bathing season, was the proportion of built-up (i.e. urbanised) land in each sub-catchment. This new finding contrasts with earlier studies in livestock farming regions where the proportion of improved grassland has proven to be the strongest predictor of microbial concentration. Also novel in this investigation, a flood defence wall has been built creating a wetland area which discharges every tidal cycle. The wetland produces over 97% reduction in the flux and concentrations of FIOs to the marine recreational waters. Also, FIO concentrations in water draining through the wetland to the sea were similar to concentrations measured in six UK sewage treatment plant effluents subject to secondary (biological) treatment followed by UV disinfection.