In 2000, a new wastewater treatment plant was built in the Chinese city of Dalian to treat wastewater from 432 000 persons (120 000 m3/day).

To manage the specifications set for the plant, a biological treatment with fixed bed was chosen. The water first undergoes pre-treatment by screening and grit/grease removal.

Filtralite® Clean is used for fixed bed wastewater treatment

Primary sedimentation is done in 4 tanks with lamellar sedimentation. The first step in the biological treatment consists of BOD, COD and SS removal in 12 Biofor filters. In these filters round expanded clay aggregates, Filtralite® Clean HR 3-6, is used as carrier for the biofilm. The second biofilter stage is nitrification in 12 Biofor filters with the same surface area as in the first step. The filter media used in these filters is Filtralite® Clean HC 2,5-5

In both types of biofilters, process air is supplied by blowers.

About 40% of the treated water is disinfected by chlorine and used as recycled water for industrial use.