Key Caboratory of Chinese Ministry of Education of northwest Water Resource and Environmental ecolog School of environmental and Municipal Engineering 声建墨群骨 xi'an University of Architecture and Technology Plain settling for 2 hours An average SS removal of 57% gained by plain Plain settling for 2 hours - COD a Raw sewage COD removal of36.6% gained by plain ettling, which equivalent to suspended CODKey Laboratory of Chinese Ministry of Education of Northwest Water Resource and Environmental Ecology School of Environmental and Municipal Engineering Xi’an University of Architecture and Technology