Essex and Suffolk Water (United Kingdom)

Abstract Algae blooms are a seasonal problem in UK waters and during these periods interferences with treatment plants are reported. This paper presents an analysis of data from 2000 to 2005 demonstrating UK experiences of algae at water treatment works. Cell populations are lower than those reported in the 1970s and 1980s, but reach levels that adversely affect treatment processes. Diatoms and cyanobacteria dominate in spring and autumn respectively. A treatment works including pre‐oxidation, coagulation, flotation and filtration removes on average 96% of influent cells, while rapid gravity filters alone remove 63–75%. Cells present in the filtrate are typically either unicellular, micro‐algae, or flagellated algae. filter blockages in the spring and autumn are caused by large cells of complex morphology, including the diatoms Melosira and Asterionella. Overall, since the 1980s the key issue with respect to algae treatment has changed from one of treatability to that of process optimisation and economics.

ABSTRACTThis report paper examines current domestic water demand elasticity, with weather variables, as an aid to assessing the potential impact of climate change on domestic water demand. An empirical model of the relationship between summer domestic water demand and concurrent weather under current climatic and socio‐economic conditions is developed and then applied to weather data which have been produced for 2020AD climate scenarios. The model is based on data for the Essex area supplied by Essex and Suffolk Water. The results suggest an increase in summer seven‐day average domestic‐water demand of 3.3 l/hd. d (range 1.37–5.72 l/hd. d), in addition to an increase in the frequency of large demand events. The analysis forms the basis of a wider exposition, examining future domestic water demand under varying climate‐change scenarios.

Rainbow trout were exposed for 3 weeks (in a flow-through system) to various dilutions of treated effluent (25, 50, 75, and 100%) from Harpenden and Chelmsford sewage treatment works (STW) during November 1994 and August 1996, respectively, and the induction of plasma vitellogenin was measured. Significant (p < 0.05) increases in plasma vitellogenin concentrations occurred in fish held in effluent from Harpenden STW at concentrations of 50% and above. At Chelmsford STW, the effluent appeared to be more potent, causing induction of vitellogenin in fish at concentrations as low as 25% (compared with 50% for the Harpenden effluent). Exposure to lower concentrations of effluent emanating from Chelmsford in April of the following year indicated that estrogenic activity was diluted to no-effect levels at this STW at concentrations between 12 and 25%.