A Regulatory Impact Assessment (RIA) has been proposed by Defra for the Priority Substances Directive which will run alongside the Water Framework Directive. The proposed directive "aims to ensure a high level of protection against risks to or via the aquatic environment stemming from 33 priority (chemical) substances by setting environmental quality standards."

The RIA identifies three options for meeting the environmental quality standards in water for Priority Substances:

·         Do nothing.

·         Meeting the environmental quality standards through end-of-pipe-controls – this assumes that end-of-pipe controls are placed on point source discharges of the substances to the aquatic environment.

·         Meeting the environmental quality standards and cessation or phase-out requirement through end-of-pipe-controls and other measures – this assumes that meeting the environmental quality standards, achieving good chemical status in surface waters and, in particular, the cessation or phase-out requirement for PHS will require not only end-of-pipe controls at point source discharges but also source controls on specific products or processes which are responsible for discharges, emissions and losses.

The RIA estimates that the costs of meeting the proposed environmental quality standards by reducing discharges at waste water treatment plants are estimated as around £1 billion. This figure suggests that around 10 per cent of sewage treatment works in the UK would require tertiary treatment in order to comply with the standards. These extra requirements will lead to another 8,000 tonnes of sludge per year requiring disposal.