Concentrations Of Faecal Indicator Organisms Research Articles

Bathing water signage and predictive water quality models in Scotland

The Scottish Environment Protection Agency (SEPA) has developed, and runs, real-time bathing water quality predictions at ten sites throughout Scotland since 2004. Daily bathing water quality predictions are posted on electronic variable message signs at 10 beach locations networked to a central communication centre and updates are simultaneously made on the SEPA website, phone and text message service. Antecedent rainfall and subsequent river flow can significantly increase the concentrations of faecal indicator organisms in bathing waters. The SEPA signage prediction tool, an Excel spreadsheet based model, was developed and used to set site-specific criteria for rainfall and river flow to predict bathing water quality based on historical data. Real-time predictions against the current EU Bathing Water Directive were correct or precautionary on 99% of days and correct for 82% of compliance samples during 2007, and 81% of compliance samples during the 2008 season. The revised 2006 Directive sets out more stringent bathing water quality standards which require increased model performance. New predictive models are now being trailed using decision tree statistical software and are intended to replace the existing prediction tool by 2012.

Faecal indicator organism concentrations and catchment export coefficients in the UK

Characterisation of faecal indicator organism (FIO) concentrations and export coefficients for catchments with particular combinations of land use and under specific climatic regimes is critical in developing models to predict daily loads and apportion sources of the microbial parameters used to regulate water quality. Accordingly, this paper presents a synthesis of FIO concentration and export coefficient data for the summer bathing season, with some comparative winter data, for 205 river/stream sampling points widely distributed across mainland UK. In terms of both geometric mean (GM) FIO concentrations and export coefficients (expressed as cfukm−2h−1), the results reveal (1) statistically significant elevations at high flow compared with base flow, with concentrations typically increasing by more than an order of magnitude and export coefficients by about two orders; (2) significantly higher values in summer than in winter under high-flow conditions; and (3) extremely wide variability between the catchments (e.g. four orders of magnitude range for GM faecal coliform concentrations), which closely reflects land use—with urban areas and improved pastures identified as key FIO sources. Generally, these two most polluting land uses are concentrated in lowland areas where runoff (m3km−2h−1) is low compared with upland areas, which in the UK are dominated by rough grazing and forestry. Consequently, contrasts in export coefficients between land use types are less than for FIO concentrations. The GMs reported for most land use categories are based on ⩾13 sites and exhibit quite narrow confidence intervals. They may therefore be applied with some confidence to other catchments in the UK and similar geographical regions elsewhere. Examples are presented to illustrate how the results can be used to estimate daily summer base- and high-flow FIO loads for catchments with different land use types, and to assess the likely effectiveness of certain strategies for reducing FIO pollutant loadings in areas with extensive areas of lowland improved pasture.

Quantification and control of microbial pollution from agriculture: a new policy challenge?

Faecal indicator organisms (FIOs) are commonly used to quantify pollution of public health significance. Health protection, as indexed by FIO control, is a central aim of new ‘catchment-scale’ water quality management required in the USA by the Clean Water Act and in the European Union (EU) by the Water Framework Directive (WFD). Experience of the former, after a decade of implementation, suggests that the most significant reason for water quality ‘impairment’ is elevated FIO concentrations, mainly in recreational and shellfish harvesting waters. This provides an early warning of possible problems which the EU regulatory authorities are likely to face. To date, however, a surprising lack of EU attention has been given to prediction and control of catchment fluxes of this key parameter. This is likely to prove embarrassing if the experience of the US regulatory community is not acted upon with some urgency. There is a growing, though still partial, body of empirical science to form the ‘evidence-base’ for good regulatory practice. However, adoption of ‘best management practices’ (BMPs) to effect remediation of impacted waters will require close integration of water policy with policies on financial support for the farming community. This is likely to require enhanced communication and integration within the discrete policy communities addressing the agricultural sector through the Common Agricultural Policy and water regulation through the Water Framework Directive.

Faecal indicator organism concentrations in sewage and treated effluents

The importance of faecal indicator organism (FIO) fluxes within drainage basins is increasing as the European Union (EU) Water Framework Directive and the United States Clean Water Act place requirements on regulators to manage point and diffuse sources of microbial pollution causing non-compliance (EU) or impairment (US) of receiving waters. Central to this management task is knowledge of the likely FIO concentrations in raw sewage and treated effluents, but few empirical data have been published in the peer-reviewed literature. Accordingly, this paper presents results for 1933 samples from 162 different sewage discharge sites in the UK and Jersey, which encompass 12 types of sewage-related discharge, representative of untreated sewage and primary-, secondary- and tertiary-treated effluents. Geometric means (GMs) and 95% confidence intervals (CIs) have been used to characterise base- and high-flow FIO concentrations. The data sets and sub-sets are mostly quite large ( n⩾40) and may therefore be applied with some confidence to comparable discharge sites in similar geographical regions. Very marked, statistically significant reductions in GM FIO concentrations result from secondary and tertiary treatment, and there are statistically significant differences between some secondary and some tertiary treatments. Flow conditions are also shown to be important: untreated sewage and effluent from primary treatment plant have lower concentrations at high flow, due to dilution within combined sewerage systems, whereas some treated effluents (e.g. from activated sludge plant) have higher concentrations at high flow because of the shorter residence time within the plant. Under base-flow conditions, secondary treatments result in estimated GM FIO reductions of 95.22–99.29% (cf. primary-treated effluent). Corresponding figures for tertiary treatment plants (cf. secondary-treated effluent) are 93.24–96.59% for reedbed/grass plots and 99.71–99.92% for UV disinfection. Results suggest that secondary and tertiary treatment plants are less effective under high-flow conditions, but further high-flow sampling is required to confirm this.

Faecal contamination of watercourses from farm waste disposal for three sites in the UK with contrasting soil types

. Despite considerable investment, some UK bathing waters fail to comply with mandatory standards as defined by the EU Bathing Water Directive (76/160/EEC). Continued non-compliance has been associated with diffuse sources of faecal indicator organism (FIO) contamination, in particular those deriving from agricultural land. This paper examines concentrations of FIOs in surface, subsurface and instream water samples at field sites considered to pose a high potential risk of FIO contamination. Quality of samples was compared with FIO standards for bathing water compliance in the UK. FIO concentrations exceeding mandatory and guideline standards were recorded frequently at all sites. In freely draining soils, FIO mobilization by rainfall was predominantly via subsurface flow, with occasional surface water flow linked to intensive rainfall events. In slowly permeable soils, surface mobilization of FIOs predominated, with the occurrence of limited subsurface samples linked to seasonal desiccation cracking within the soil, and to intense rainfall events. Watercourse FIO concentrations were significantly increased as the stream passed-by fields with freely draining soils. The data imply a generally higher risk of FIO transfer from freely draining soils and occasional increased risk from less permeable soils due to temporal changes in soil structure and rainfall intensity.

Processes driving the episodic flux of faecal indicator organisms in streams impacting on recreational and shellfish harvesting waters

Understanding the process controls on episodic fluxes of faecal indicator organisms (FIOs) is becoming increasingly important for the sustainable management and accurate modelling of water quality in both recreational and shellfish harvesting waters. Both environments exhibit transitory non-compliance with microbiological standards after rainfall episodes despite significant expenditures on control of sewage derived pollutant loadings in recent years. This paper demonstrates the role of wave propagation in the entrainment of FIOs from river channel beds as a contributor to episodes of poor microbial water quality. Previously reported data is reviewed in the light of relationships between wave and mean water travel velocities. High flows and rapid changes in river flow, driven by releases of bacterially pure reservoir water, resulted in elevated FIO concentrations and transient peaks in concentration. The new interpretation of these data suggest three modes of entrainment: (i) immediate wave-front disturbance, (ii) wave propagation lift and post-wave transport at mean flow velocity, and (iii) stochastic erosional mechanisms that maintain elevated bacterial concentrations under steady high flow conditions. This is a significant advance on the previously proposed mechanisms. Understanding these mechanisms provides an aid to managing streams intended for recreational use and emphasises the need to control the timing of high flow generation prior to use of the water body for e.g. canoeing events. In addition the processes highlighted have relevance for the protection of shellfish nurseries, drinking water supply intakes and episodes of poor bathing water quality, and associated health risks.

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 km 2) 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 ( r 2 : 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.

Derivation of numerical values for the World Health Organization guidelines for recreational waters

In April 2001, draft ‘Guidelines’ for safe recreational water environments were developed at a World Health Organization (WHO) expert consultation. Later the same month, these were presented and discussed at the ‘Green Week’ in Brussels alongside the on-going revision of the European Union Bathing Water Directive 76/160/EEC. The WHO Guidelines cover general aspects of recreational water management as well as define water quality criteria for various hazards. For faecal pollution, these include faecal indicator organism concentrations and an assessment of vulnerability to faecal contamination. Central to the approach set out in the WHO Guidelines are: (i) the concept of beach profiling to produce a ‘sanitary inspection category’ which implies a priori hazard assessment as a core management tool and (ii) the prediction of poor water quality to assist in real time risk assessment and public health protection. These management approaches reflect a harmonized approach towards the assessment and management of risk for water-related infectious disease being applied by WHO. Numerical microbiological criteria for intestinal enterococci are proposed in the new Guidelines. These were developed using a novel approach to disease burden assessment, which has been applied to both recreational waters and urban air quality. This paper explains the scientific rationale and mathematical basis of the new approach, which is not presented in the WHO Guidelines for recreational waters.

Modelling faecal indicator concentrations in large rural catchments using land use and topographic data

To characterize and model spatial variations in faecal-indicator organism concentrations in watercourses draining a large rural catchment during the bathing season. Presumptive coliform (PC), presumptive Eschericia coli (PE) and presumptive enterococci (PEnt) concentrations were determined under base- and high-flow conditions at 24 monitoring points in the Rheidol/Ystwyth catchment, Wales. Relationships with land use and topographic variables within their 'subcatchments' were investigated. Geometric mean (GM) concentrations typically increase more than 10-fold at high flow. The proportion of improved pasture within subcatchments explains 81.6, 73.0 and 85.8%, respectively, of the variance in high-flow GM PC, PE and PEnt concentrations. Distributed modelling suggests that organisms derived from more distant parts of subcatchments may be lost through die-off and sedimentation along watercourses at base flow, although not at high flow. Reductions in concentrations are also evident downstream of reservoir impoundments. Large rural catchments may contribute substantially to faecal indicator loadings in coastal waters. Indicator concentrations can be modelled successfully using land use and topographic data. Development of a modelling approach that provides valuable insight into faecal indicator sources and the transport and survival of these organisms within large catchments.

Evaluation of faecal contamination and microbial die-off in urine separating sewage systems

An important feature for recirculated products from a sewage system is that the risk for transmission of disease is low. In a urine source separating system faeces may contaminate the collected urine through the toilet. The concentrations of faecal indicator organisms were measured in 14 urine collection tanks. The survival of these and some pathogenic microorganisms in source separated human urine was studied. Total coliforms, E. coli and clostridia were found in low concentrations while faecal streptococci occurred in concentrations up to 105/ml urine solution. The results from phenotyping of faecal streptococci and the high counts indicate growth within the system. The majority of the pathogenic microorganisms investigated had a rapid die-off. A higher temperature, a low degree of dilution and a pH far from neutral had a negative effect on survival. E. coli had a rapid die-off and is not suitable for indicating faecal contamination of the collected urine. Quantification of faecal sterols is a possible alternative to microbial analysis for this purpose. The amounts of coprostanol showed that the faecal contamination varied from not detected to up to 13.3 mg/ml urine solution with a concentration in the urine sludge of up to 417.5 mg/kg.

Evaluation of faecal contamination and microbial die-off in urine separating sewage systems

An important feature for recirculated products from a sewage system is that the risk for transmission of disease is low. In a urine source separating system faeces may contaminate the collected urine through the toilet. The concentrations of faecal indicator organisms were measured in 14 urine collection tanks. The survival of these and some pathogenic microorganisms in source separated human urine was studied. Total coliforins, E. coli and clostridia were found in low concentrations while faecal streptococci occurred in concentrations up to l05/ml urine solution. The results from phenotyping of faecal streptococci and the high counts indicate growth within the system. The majority of the pathogenic microorganisms investigated had a rapid die-off. A higher temperature, a low degree of dilution and a pH far from neutral had a negative effect on survival. E. coli had a rapid die-off and is not suitable for indicating faecal contamination of the collected urine. Quantification of faecal sterols is a possible alternative to microbial analysis for this purpose. The amounts of coprostanol showed that the faecal contamination varied from not detected to up to 13.3 mg/ml urine solution with a concentration in the urine sludge of up to 417.5 mg/kg.

Indicator organism sources and coastal water quality: a catchment study on the island of Jersey.

Compliance monitoring of bathing waters at La Grève de Lecq on the North coast of Jersey revealed a significant deterioration in water quality between 1992 and 1993, as indexed by presumptive coliform, presumptive Escherichia coli and streptococci concentrations. During the 1993 bathing season the beach failed to attain the compliance with the EC Guideline criteria for presumptive E. coli and streptococci. A bacteriological survey of the stream catchment draining to the beach revealed that: (i) concentrations of faecal indicator organisms were enhanced at high discharge after rainfall; and (ii) a captive water fowl population, which expanded between 1990 and 1993, was a potential source of faecal pollution. Strategies for catchment management are discussed.