The mechanism, technology and character of the anaerobic-aerobic treatment of dye wastewater by combination of fixed film with suspended growth after acclimatization are discussed in this paper. The results show that the COD decreased from 600-900mg/l of influent to about 150mg/l of effluent. The BOD and the dilution times of colourity decreased from 200-300mg/l and 200-500 times to less than 50mg/l and about 80 times respectively, when the HRT and COD RBC-area load of anaerobic and aerobic RBC were 7-8hrs and 4.5-5hrs and 40-50g/m2.d and 30-40g/m2 respectively. This treatment process has the advantage of very low waste sludge. Either anaerobic or aerobic RBC has better quality transmission and mixing ability, so that MLSS in the tank were about 1000-3000mq/l without any blockages of RBC. The efficiency of a 3 stage alone oblique cross passageways packing RBC with sludge return was also high, except in regard to colour under aerobic conditions only.
