About 18,000 restaurants and big producers of sewage would have to pay the full cost of treatment by 2015 under a new government proposal. The Environment, Transport and Works Bureau and the Environmental Protection Department set out the goal in a consultation paper due to come out next month. Businesses belonging to 30 trades pay a trade effluent surcharge on top of a sewage charge as they discharge more pollutants than domestic users. They pay a surcharge of between $0.11 to $3.78 per cubic metre, depending on the nature of their business. For eight of these trades, including restaurants, the surcharge is 80 per cent of the treatment cost. Wong Chee-keung, the director of drainage services, yesterday said it was important to implement the 'polluter pays' principle. He said the authorities wanted to consult all relevant parties on the best and most convenient way to recover the full costs of treatment. Subjects to be covered included the charging model and fee-adjustment mechanism. Mr Wong, who took up the position last month, expects fierce resistance, especially from restaurants which make up of 73.1 per cent of the group and contributed 88.2 per cent of all trade effluent surcharges last year. The department received $209.1 million in such surcharges last year. At the moment, domestic users pay about $1.20 for every cubic metre of waste water discharged - about half the sewage treatment cost.