ISBN: 184057 765 7
Published Date: 04/06/2015
Water and Sewerage Companies (WASCs) recover costs for treating trade effluent using the Mogden formula which ensures that all customers are paying their appropriate share. The formula calculates charges based on the effluent volume and strength discharged, though in practice these may be difficult to measure. Therefore, WASCs apply allowances and fixed strengths to estimate these, which provide WASCs and traders both financial and timesaving benefits. However, the opening of the non-household retail market in 2017 could see increased challenges from traders if volume and strength estimates are not consistent and transparent.
This project provides a robust reference review and industry wide guidance of when and how to apply allowances and fixed strengths. The key findings are that the 25 l/person/day domestic allowance used by most WASCs remains a valid estimate of domestic water use and approaches to non-return to sewer allowances are fair and transparent. It is however recommended that allowances should be calculated in conjunction with a water balance and if trade effluent customers disagree with their allowance they can fit sub meters and effluent meters. Technical guidance documents were developed to facilitate consistency in managing trade effluent.