Residents face higher charges over each of the next 10 years after legislators approved what officials termed a 'mild' rise in sewage-treatment charges. With backing from Liberal and DAB legislators, environment officials yesterday pushed through a law raising the charges annually for the next decade. The charges had not been adjusted for more than 12 years. Opponents from the Democratic Party and Civic Party said the 10-year specification forfeited the rights of lawmakers to later review the annual fee increases, despite a lack of any official assurance that the system would be upgraded from chemical to the more superior biological treatment of sewage. The charge will increase 9.3 per cent on April 1 every year from 2008 until 2017. Water users pay HK$1.20 per cubic metre of water. This will rise to HK$1.31 next April, reaching HK$2.92 in 2017. It is estimated that the monthly payment for the average household will rise from HK$11 to HK$27 over the period. Lobbying for support yesterday, Secretary for Environment, Transport and Works Sarah Liao Sau-tung said the government would report annually on the charge account and on progress of sewage projects. While pledging a review of the fee rise and treatment upgrade in 2011, Dr Liao reiterated that the 10-year increase plan was vital to realise polluter-pay principles aimed at changing public behaviour. 'I hope the harbour's water will not turn dark and reach a tipping point that restoration will become impossible if we fail to provide the necessary finance now and let the water quality deteriorate,' she told legislators. Civic Party leader Audrey Eu Yuet-mee, who tried in vain to move an amendment to modify the 10-year rise plan to four years, said her proposal would urge officials to formulate a treatment upgrade plan when they sought further fee rises. 'The only power legislators can exercise is to approve or disapprove the fee rise, and if we don't press officials to do more at this time, those supporters [of the legislation] will owe the public an explanation when things go wrong,' she said. The fee rise aims to cut the government's subsidy of treatment costs from 47 per cent to 20 per cent by 2017. The revenue will finance operating costs at existing and planned sewage treatment facilities. At least 41 new projects, costing HK$20 billion, are planned for the next decade, including the HK$8 billion Harbour Area Treatment Scheme Stage 2A.