CONTROLLING AND DE-CONTAMINATING SITE WASTEWATER

摘要

The Castleford site of Hickson & Welch is situated astride the river Aire, just below its confluence with the River Calder. The site handles a wide range of toxic and corrosive organic chemicals, which have the potential to produce severe effects in the river, were they allowed to reach it. The protection of the river has assumed ever-greater importance during the last decade and the company has adopted a comprehensive strategy to protect the river from both accidental contamination and routine discharge. The paper will describe the elements of the strategy, which includes action now completed, and the current programme of work. The completed strategies include: a site kerb, a low wall round the site which prevents accidental spillage and fire water from reaching the river; rigorous segregation of clean cooling water, which can be returned to the river, from process and rain water, which goes to the site effluent treatment plant; and site-wide renewal of the effluent collection system, bring it above ground into custom made piping systems. Work in progress includes: the generation of a site storage register which is coupled to a storage risk assessment system - being developed with HSE - to assess potential risks from the storages onsite; a ground water survey to ensure that legacy pollution is understood; and work on the safe storage of drummed materials around the site. At the centre of the strategy is a new best practice standard setting, wastewater Treatment Plant. This combines a Loprox~(~R), wet oxidation plant using liquid oxygen at moderate temperature and pressure to detoxify otherwise hard to treat waste streams; and a Vitox~(~R) biological treatment plant, using an oxygen fed activated sludge. This holistic approach has enabled the site to treat most aqueous waste streams on site and to cease sending site effluent to the local municipal sewage treatment plant. The final treated stream is now discharged direct to river with consequent improvements in the quality of the site effluent stream. This has also enabled the local sewage treatment plant to improve its discharge. These two changes have contributed to a significant improvement in river quality. The paper will describe these various initiatives in technical detail and indicate the site's vision for the future.