Author(s): Amyrhul Abu Bakar, Reza Ahmadian, Roger A. Falconer
Linked Author(s): Amyrhul Abu Bakar
Keywords: Hydro-environmental modelling, faecal bacteria, diffuse source, Loughor Estuary, shellfish contamination
Abstract: The Loughor Estuary is a macro-tidal estuarine waterbody which is located on the North of the Bristol Channel, South West of the U. K. This estuary, with a shallow inlet, traps sand and mud from Carmarthen Bay, which are discharged from upstream catchments and resuspended through the tidal cycle in the estuary. Much of the estuary dries during low tides and forms an important site for shellfish beds. The water quality at this site of interest is potentially impaired by receiving bacterial overloading from multiple sources, including: sheep grazing on the intertidal marshland at the southern edge of the estuary. As the point source of bacteria generated from domestic and industrial inputs is well quantified through releases from the wastewater treatment works, the bacterial diffuse sources originating from the marshland during intertidal flooding are considered as being poorly quantified and could be one of the main contributors of the failure of this waterbody to comply with the guideline standards of the EU Shellfish Water Directive. Accurate computations of bacterial loading are required to establish a trade-off between managing livestock grazing practices and improving the water quality status. In this study, a developed two-dimensional hydrodynamic model has been extended to solve the transport process of bacteria within this waterbody. The bacteria loading from the marshland is computed based on the animal density and their faeces production rates during grazing over the drying areas. The bacteria released from the marshland and loading into the waterbody are treated as an instantaneous flush of a diffuse source after flooding during subsequent high tides. The transported bacteria concentrations within the shellfish water are evaluated for the exposure time and severity variables to the filter-feeding shellfish in this waterbody. The improved model for the quantification of diffuse bacteria loading from the intertidal marshland can be used for assessing the impacts of various sources and adopting the best management practices
Year: 2017