The pretreatment by the Fe-Cu process for enhancing biological degradability of the mixed wastewater.

The Fe-Cu process in combination with cyclic activated sludge system (CASS) was used to treat the mixed wastewater composed of industry wastewater and urban sewage in this work. The results showed that the pretreatment by the Fe-Cu process removed 20% of COD(cr) and 32% of total phosphorus (TP), which reduced the loading rate of the subsequent biological treatment. Mean while, biodegradability of the wastewater was enhanced, which created favorable condition for the subsequent biological treatment. The formation of heavy, lumpy or granular, absorbent, enriched with microorganisms bio-ferric activated sludge with good setting performance promoted degradation of various refractory organic contaminants. The increase by 10 times of nitrifying and denitrifying bacteria counts (total biofilm biomass increased by 59%) and 0.4 of pH value enhanced the biological nitrification and denitrification to ensure the final effluent NH(3)-N and TN to be 8 and 20mg/L, respectively. Agglomeration, passivation and clogging of iron were not observed in three months of continuous operation. Furthermore, the consumption of iron was low. All these led to an easy maintenance and low operating cost.