Quantitative catchment profiling to apportion faecal indicator organism budgets for the Ribble system, the UK's sentinel drainage basin for Water Framework Directive research.

Under the EU Water Framework Directive (WFD) 20/60/EC and the US Federal Water Pollution Control Act 2002 management of water quality within river drainage basins has shifted from traditional point-source control to a holistic approach whereby the overall contribution of point and diffuse sources of pollutants has to be considered. Consequently, there is a requirement to undertake source-apportionment studies of pollutant fluxes within catchments. The inclusion of the Bathing Water Directive (BWD), under the list of 'protected areas' in the WFD places a requirement to control sources of faecal indicator organisms within catchments in order to achieve the objectives of both the BWD (and its revision - 2006/7/EC) and the WFD. This study was therefore initiated to quantify catchment-derived fluxes of faecal indicator compliance parameters originating from both point and diffuse sources. The Ribble drainage basin is the single UK sentinel WFD research catchment and discharges to the south of the Fylde coast, which includes a number of high profile, historically non-compliant, bathing waters. Faecal indicator concentrations (faecal coliform concentrations are reported herein) were measured at 41 riverine locations, the 15 largest wastewater treatment works (WwTWs) and 15 combined sewer overflows (CSOs) across the Ribble basin over a 44-day period during the 2002 bathing season. The sampling programme included targeting rainfall-induced high flow events and sample results were categorised as either base flow or high flow. At the riverine sites, geometric mean faecal coliform concentrations showed statistically significant elevation at high flow compared to base flow. The resultant faecal coliform flux estimates revealed that over 90% of the total organism load to the Ribble Estuary was discharged by sewage related sources during high flow events. These sewage sources were largely related to the urban areas to the south and east of the Ribble basin, with over half the load associated with the relatively small subcatchment of the River Douglas. The majority of this load was attributed to two WwTWs that discharge through a common outfall close to the tidal limit of this catchment. Budgets adjusted to accommodate the impact of proposed UV disinfection of these effluents showed that the load from these sources would be reduced significantly during base flow conditions. However, during high flow events loads would still remain high due to the operation of storm sewage overflows from stormwater retention tanks. The study identified untreated storm sewage spills from urban infrastructure and WwTW stormwater retention tanks as the dominant component of the high flow flux of faecal indicators to receiving waters of the Fylde coast and the associated bathing waters.

Assessing the impact of nutrient enrichment in estuaries: susceptibility to eutrophication.

The main aim of this study was to develop a generic tool for assessing risks and impacts of nutrient enrichment in estuaries. A simple model was developed to predict the magnitude of primary production by phytoplankton in different estuaries from nutrient input (total available nitrogen and/or phosphorus) and to determine likely trophic status. In the model, primary production is strongly influenced by water residence times and relative light regimes. The model indicates that estuaries with low and moderate light levels are the least likely to show a biological response to nutrient inputs. Estuaries with a good light regime are likely to be sensitive to nutrient enrichment, and to show similar responses, mediated only by site-specific geomorphological features. Nixon's scale was used to describe the relative trophic status of estuaries, and to set nutrient and chlorophyll thresholds for assessing trophic status. Estuaries identified as being eutrophic may not show any signs of eutrophication. Additional attributes need to be considered to assess negative impacts. Here, likely detriment to the oxygen regime was considered, but is most applicable to areas of restricted exchange. Factors which limit phytoplankton growth under high nutrient conditions (water residence times and/or light availability) may favour the growth of other primary producers, such as macrophytes, which may have a negative impact on other biological communities. The assessment tool was developed for estuaries in England and Wales, based on a simple 3-category typology determined by geomorphology and relative light levels. Nixon's scale needs to be validated for estuaries in England and Wales, once more data are available on light levels and primary production.

Dissolved oxygen as a physico-chemical supporting element in the Water Framework Directive.

For transitional and coastal waters the Water Framework Directive identifies 5 "General chemical and physiochemical elements supporting the biological elements". The five elements are transparency, thermal conditions, oxygenation conditions, salinity and nutrient conditions. "Supporting" in the context of the directive means that the values of the physicochemical quality elements are such as to support a biological community of a certain ecological status, recognising the fact that biological communities are products of their physical and chemical environment. Physicochemical and hydromophological aspects fundamentally determine the type of water body and habitat, and hence the type specific biological community. The directive does not intended that these supporting elements should be used as surrogates for the biological elements in monitoring. The monitoring and assessment of the physical and physicochemical quality elements will support the interpretation, assessment and classification of the results arising from the monitoring of the biological quality elements. This paper considers the challenges involved in the development of oxygen standards for the directive, their relationship to the biological elements and normative conditions of the directive and to regulatory requirements.

Estimation of diffuse and point source microbial pollution in the ribble catchment discharging to bathing waters in the north west of England.

Achieving compliance with the mandatory standards of the 1976 Bathing Water Directive (76/160/EEC) is required at all U.K. identified bathing waters. In recent years, the Fylde coast has been an area of significant investments in 'point source' control, which have not proven, in isolation, to satisfactorily achieve compliance with the mandatory, let alone the guide, levels of water quality in the Directive. The potential impact of riverine sources of pollution was first confirmed after a study in 1997. The completion of sewerage system enhancements offered the potential for the study of faecal indicator delivery from upstream sources comprising both point sources and diffuse agricultural sources. A research project to define these elements commenced in 2001. Initially, a desk study reported here, estimated the principal infrastructure contributions within the Ribble catchment. A second phase of this investigation has involved acquisition of empirical water quality and hydrological data from the catchment during the 2002 bathing season. These data have been used further to calibrate the 'budgets' and 'delivery' modelling and these data are still being analysed. This paper reports the initial desk study approach to faecal indicator budget estimation using available data from the sewerage infrastructure and catchment sources of faecal indicators.

The impact of bird populations on the microbiological quality of bathing waters.

To ensure optimum quality at Bathing Waters, the control of diffuse sources of bacterial contamination is receiving increasing attention. As part of an initiative to improve the quality of the EU designated bathing waters on the Fylde Coast (North West England), a project was undertaken to quantify the faecal indicator load from birds and assess the significance on water quality. High bird counts are encountered on the Fylde Coast with gulls, feral pigeons and starlings being prominent. The piers at Blackpool make an attractive roost for starlings with numbers peaking at over 30,000 in late summer. Systematic recording of bird numbers and locations was undertaken during 2001/2. Estimates were also made of the daily faecal organism production by the different species. The spatial distribution of faecal organisms from the bird population was statistically linked to synoptic water quality data. This allowed estimates to be made of the contribution from birds to the faecal pollution load at the bathing waters. The work confirmed a statistically significant link between bird populations and water quality with a marked seasonal bias.

The distribution of mercury and other trace metals in the sediments of the Mersey Estuary over 25 years 1974-1998.

Mercury and other heavy metals have been monitored in the surface sediments of the Mersey Estuary in NW England for a period of 25 years, using a consistent methodology and sampling grid. This has produced one of the most comprehensive data sets available in the literature and demonstrated some of the difficulties associated with undertaking long-term environmental monitoring. The data indicate that the concentration of mercury and other metals in the sediments of this estuary are strongly correlated to the organic matter and particle size content. This has resulted in the metal distribution patterns reflecting the sediment characteristics and dynamics, irrespective of the position of the input sources. The trend data has indicated a continual, although somewhat uneven, decline in the concentration of most of the metals studied. Remobilisation of previously consolidated saltmarsh sediments can cause significant perturbations in contaminant reduction trends, and needs to be considered in the design of long term monitoring programmes.