A full-scale biological treatment system application in the treated wastewater of pharmaceutical industrial park

A full-scale combined biological system is used for the treatment of treated wastewater discharged from a pharmaceutical industrial park. This treated water is rich in NH4+–N (average in 86.4 mg/L), low in COD/NH4+–N (average in 3.4) and low in BOD5/COD ratio (average in 0.24) with pH varying from 7.16 to 7.78. The final effluent of the combined treatment process was stably below 100 mg/L COD and 20 mg/L NH4+–N, separately, with organic loading rate of 4954 kg COD/d and 92.5 kg NH4+–N/d. It is found that the BOD5/COD ratio could be raised from 0.24 to 0.35, and the production of total VFAs account for 9.57% of the total COD via the treatment of hydrolysis/acidification. MBBR and oxidation ditch represent 35.4% and 60.7% of NH4+–N removal, 30.2% and 61.5% of COD removal, separately, of the total treatment process. PCR-DGGE is used for microbial community analysis of MBBR and oxidation ditch.