In 1996, the Environment Agency proposed that toxicity limits in discharge consents could be used in regulating chemically complex effluents. The idea got a stormy response from industry (ENDS Report 262, pp 19-21 ).
Industry bodies argued that the proposals would be too costly and a recipe for protracted legal disputes. The Agency toned down its plans and proposed a jointly led demonstration programme to show how DTA would work in practice. Other UK regulators have also been involved via the Scottish and Northern Ireland Forum for Environmental Research.
Despite the Agency's softer line, many of the tensions with industry were still evident at a February meeting on DTA at the Society of Chemical Industry. Derek Tinsley of the Agency's National Centre for Ecotoxicology and Hazardous Substances told the meeting that the emphasis is no longer on using toxicity conditions as a trigger for enforcement, but as a signal for dischargers to take action.
"If a discharger fails to take action we would regard that as an indifference to their duty of care to the environment," he said.
But the Agency's goal of zero chronic toxicity at the point of discharge to the environment was dismissed by industry representatives. Graham Whale of Shell Research said it was "unrealistic", "prohibitively expensive" and presented "severe practical difficulties".
John Solb&eacu. of Unilever agreed that the goal would be "too expensive", adding that industry favoured cost/benefit analysis "so that the degree of protection given is in accordance with the willingness to pay."
Dr Tinsley defended the zero toxicity target as "necessary for the environment", but conceded that it was "not practicable everywhere". He accepted the need to consider costs and benefits, but emphasised the need to move towards the goal in the longer term: "Just because the first steps are met the process is not necessarily over. There is a need for constant review."
The DTA demonstration programme begins in March and is being coordinated by representatives from the Agency and industry. It will attempt to identify sources of toxicity in four areas: 46 kilometres of the river Aire, 5.5km of the Tees Estuary, 11km of the river Esk and 0.75km of the Spey.
Many of the companies affected will be dischargers to sewer. Yorkshire Water's trade effluent manager, Kevin Prior, envisaged that sewerage undertakers would have to sign up to toxicity investigation and improvement programmes with the Agency - leading in turn to water companies imposing controls on their customers.
"It's a fair bet that there will be toxicity consents on discharges to sewer," he warned. Two water companies have already introduced `inhibition' clauses in effluent agreements to protect the nitrification process at sewage works which removes ammonia from sewage and industrial effluents.
On the issue of enforceability, Mr Prior noted that the inhibition clauses had "gone through Ofwat" with apparent approval. Twenty other sites also had toxicity conditions on their consents. He concluded: "The message is that if there is a [legal] loophole it is rapidly being closed up."
The first step for the programme in West Yorkshire was to discuss the matter with local dischargers, Mr Prior said. "The issue is how to get it on the agenda in a non-threatening way. Only 18 companies have expressed an interest, but there are 2,500 on our books. Many companies do not realise it will affect them."
Mr Prior said the sectors most likely to be affected were waste companies tankering liquids for disposal at treatment works, chemical manufacturers and textile businesses with effluents containing mothproofers or other pesticides.