A TOTAL of $6.8 billion will be sought from legislators for a trading fund to reduce water pollution. Secretary for Works James Blake told the Legco Environmental Affairs Panel yesterday that the money would allow the Government to proceed with projects to improve water quality in Victoria Harbour. It would sponsor the setting up of sewage collection, treatment and disposal systems, different from the present drainage and river control systems provided by the Drainage Services Department. Mr Blake said the operational cost of the scheme would, however, need to be supported by charging polluters fees, which he expected to begin by August, with an estimated annual increase of 10 per cent afterwards. The fees collected would support the operational costs of the new sewage scheme, such as the maintenance of drainage systems, administration fees and staff salaries. But independent legislator Emily Lau Wai-hing queried the estimated annual rate increase of 10 per cent. ''Will a large reserve be accumulated with a 10 per cent increase every year? Or what would be the case if the charges were not enough to support the services?'' she asked. Drainage Services Department development manager Peter George Winder said the charges in the first few years would amount to more than actual expenditure. The legislators will vote on the resolution for the establishment of the trading fund on February 23.