2.3. Experimental
Z08 was added into soybean wastewater in 250 mL flasks with a concentration of 840 mg/L (dry weight). The flasks were tightened by oxygen enriching membranes and were rotated at 120 rpm with treatment temperature around 26–30 _C. The dissolved oxygen (DO) was kept around 1.0 mg/L. Four levels of ratio of food and microbe (F/M, mg-COD/mg-biomass), 40, 20, 10 and 2 were tested. Two pretreatment methods were used: coagulation and 24 h yeast degradation (Zhang et al., 2005). Post-treatment with activated sludge (sludge concentration of 3400 mg/L) was used after 72 h Z08 treatment.