A multi-million dollar sewage-treatment plant designed to handle waste from the new airport and Tung Chung new town will initially only 'sieve' sewage. The $400 million plant at Siu Ho Wan, now being commissioned, will provide the lowest level of treatment - preliminary. Environmental Protection Department officials have defended the decision, saying water quality objectives would not be exceeded and treatment would be upgraded before waste was piped from other parts of Lantau. But Friends of the Earth spokesman Lisa Hopkinson said water quality objectives failed to take into account ecological factors - such as the Chinese white dolphins which inhabit the area. 'It is the irony of spending billions and billions of dollars on this first-class state of the art new airport, and what do we have? A screening sewage-treatment plant. 'Twenty million dollars is spent every day on the new airport. No expense has been spared, and yet the environment is bottom of the heap.' The head of Hong Kong University's Department of Ecology and Biodiversity, Dr John Hodgkiss, said preliminary 'sieving' could increase the bacterial load - to the detriment of the dolphins. Principal environmental protection officer David Hall said preliminary treatment was adequate until Tung Chung and sewage from other parts of Lantau was piped to the plant. By early next century the plant would be upgraded to either primary or chemically enhanced treatment, he said.