Assessment of the Potential Costs to the Water
Industry of Reducing Oestrogenic Steroid Discharges in Treated Sewage
Effluent – Final Report
Over recent years it has become apparent that in certain rivers in the United Kingdom the presence of natural vertebrate steroids such as oestrone (E1), 17β-oestradiol (E2) and oestriol (E3) and the synthetic steroid 17α-ethinyloestradiol (EE2) has resulted in adverse effects on aquatic organisms, principally fish, through an oestrogenic mode of action. It has become evident that these substances are entering rivers via sewage treatment works (STW) effluents with the resulting concentrations in the receiving waters depending on a number of site–specific factors. The Environment Agency have commissioned studies relating to these endocrine-disrupting effects and from these predicted-no-effect-concentrations (PNECs) have been proposed for some oestrogenic steroids where data has permitted. Data also indicates that in a significant number of rivers concentrations of these steroids may exceed these PNEC values.
The Department for Environment, Food and Rural Affairs (Defra) has recognised that there is a need to assess the practical implications and potential costs to the water industry should a reduction in the oestrogenic steroid content of STW discharges be required. To this end Defra has commissioned this study whose overall objective has been to provide an indication of the costs of reducing the oestrogenic steroid concentrations in STW discharges, together with a prioritised list of work which would be required to refine the estimate. There are three distinct phases to this study:
This report summarises the results of the study and comprises:
Analysis of survey data from the most comprehensive study undertaken in the UK would indicate the following ranges (lower 5 percentile to upper 95 percentile values) of concentrations for three oestrogenic steroids and for the total steroids:
|Oestrone||0.25 to 2.91 ng l-1|
|17β-oestradiol||0.25 to 1.67 ng l-1|
|17α-ethinyloestradiol||0.25 to 0.91 ng l-1|
|Total steroids (as 17αa-ethinyloestradiol)||0.31 to 1.08 ng l-1|
Estimates of the lower bound values are constrained as many reported values were below the limit of detection. Predicted river concentrations based on data for 467 sewage treatment works having a population equivalent greater than 10,000 gave similar range values:
|Oestrone||0.122 to 15.8 ng l-1|
|17β-oestradiol||0.020 to 2.54 ng l-1|
|Oestriol||0.116 to 15.1 ng l-1|
|17α-ethinyloestradiol||0.004 to 0.48 ng l-1|
|Total steroids (as 17&alpha-ethinyloestradiol)||0.008 to 1.08 ng l-1|
Review of the proposed PNEC values concluded;
Based on current views of the scope of steroid oestrogen pollution and the likely concentration values required to achieve a protective standard the regulatory scenario adopted assumes the following:
Applying these assumptions to a sample dataset (representing 467 of the approximately 711 works over 10,000 pe in England and Wales) the likely additional treatment requirements were estimated. Analysis of this data showed that whilst 32% of works were not likely to require any further treatment, 52% would require greater than 50% additional removal. It would seem unlikely that this higher degree of removal could be met through low-cost improvement options and, therefore, costs were estimated for the addition of further treatment processes. Two options were identified as suitable candidates on which to base cost estimates; these were tertiary granular activated carbon (GAC) and tertiary biological treatment.
Cost estimates were developed for these process options. From these estimates the following conclusions were drawn:
Capital and operating costs would fall proportionately where lower degrees of oestrogenic steroid removal were required.
Biological treatment cost estimates are subject to a high degree of uncertainty and, using a more optimistic assumption regarding the rate of steroid removal, the capital and operating costs could be significantly lower giving NPC values (20 year lifetime at 5%) ranging from £1.1M to £39.4M per works.
Copies of this report may be available as an Acrobat pdf download under the 'Completed Research' heading of the Research Page on the DWI website.