Browsing by Author "Finnegan, Chris J."
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Item Open Access Continuous-flow laboratory simulation of stream water quality changes downstream of an untreated wastewater discharge.(Elsevier Science B.V., Amsterdam., 2009-04-01T00:00:00Z) Finnegan, Chris J.; van Egmond, R. A.; Price, O. R.; Whelan, M. J.In regions of the world with poor provision of wastewater treatment, raw sewage is often discharged directly into surface waters. This paper describes an experimental evaluation of the fate of two organic chemicals under these conditions using an artificial channel cascade fed with a mix of settled sewage and river water at its upstream end and operated under continuous steady-state conditions. The experiments underpin an environmental risk assessment methodology based on the idea of an “impact zone” (IZ) – the zone downstream of wastewater emission in which water quality is severely impaired by high concentrations of unionised ammonia, nitrite and biochemical oxygen demand (BOD). Radiolabelled dodecane-6-benzene sulphonate (DOBS) and aniline hydrochloride were used as the model chemical and reference compound respectively. Rapid changes in 14C counts were observed with flow-time for both these materials. These changes were most likely to be due to complete mineralisation. A dissipation half-life of approximately 7.1 h was observed for the 14C label with DOBS. The end of the IZ was defined as the point at which the concentration of both unionised ammonia and nitrite fell below their respective predicted no-effect concentrations for salmonids. At these points in the cascade, approximately 83 and 90% of the initial concentration of 14C had been removed from the water column, respectively. A simple model of mineral nitrogen transformations based on Michaelis–Menten kinetics was fitted to observed concentrations of NH4, NO2 and NO3. The cascade is intended to provide a confirmatory methodology for assessing the ecological risks of chemicals under direct discharge conItem Open Access Development of simulation tests to assess the fate of Unilever ingredients under untreated discharge conditions(Cranfield University, 2007-12) Finnegan, Chris J.; Warner, P.Unilever product ingredients are discharged into the environment via a number of routes, in many regions of the world there is a lack of municipal waste water treatment and the discharge of chemicals directly into the environment in the presence of untreated sewage is a major pathway. An absence of data on the behaviour of the fate and effects of chemicals under such conditions requires overly stringent and unrealistic assumptions when assessing risk (e.g. no biodegradation is assumed). Traditional risk assessment fails since water quality is compromised by pollutants associated with raw sewage (e.g. BOD and ammonia) and the relevance of the ‘standard’ risk assessment approach has thus been questioned. An alternative risk assessment model, based on the ‘impact zone’ concept, has been proposed for direct discharge conditions. In this model, chemicals are assessed in terms of their predicted environmental concentration (PEC) at the end of an impact zone, within which the ecosystem is impacted by the pollutant, free ammonia, and beyond which it is not. Linear alkylbenzene sulphonate (LAS) was used a model compound to understand the fate of materials classified as readily biodegradable in this scenario. Batch and dynamic test systems simulating conditions associated with untreated discharge, confirmed that LAS was degraded quicker than the general organics present in settled sewage and that beyond the defined ‘impact zone’ it is extensively removed. Predicted no effect concentrations (PNECs) can also be generated for chemicals on the inhibition of key microbial processes (biological oxidation and nitrification) which are essential in rivers for self purification. A variety of detergent ingredients (ranging from readily biodegradable to anti-bacterial) were investigated in short term toxicity tests. The tests produced a range PNECs and confirmed that these ingredients can show selective inhibition towards heterotrophic or autotrophic bacterial populations. All of the PNECs generated were above the PEC for these ingredients.