Aquatic environment

Effect of powdered activated carbon on Chinese traditional medicinewastewater treatment in submerged membrane bioreactorwith electronic control backwashing


LIU Xiao-lei , REN Nan-qi , MA Fang

DOI:

Received November 17, 2006,Revised January 25, 2007, Accepted , Available online

Volume 19,2007,Pages 1037-1042

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Chinese traditional medicine wastewater, rich in macromolecule and easy to foam in aerobic biodegradation such as Glycosides, was treated by two identical bench-scale aerobic submerged membrane bioreactors (SMBRs) operated in parallel under the same feed, equipped with the same electronic control backwashing device. One was used as the control SMBR (CSMBR) while the other was dosed with powdered activated carbon (PAC) (PAC-amended SMBR, PSMBR). The backwashing interval was 5 min. One suction period was about 90 min by adjusting preestablished backwashing vacuum and pump frequency. The average flux of CSMBR during a steady periodic state of 24 d (576 h) was 5.87 L/h with average hydraulic residence time (HRT) of 5.97 h and that of PSMBR during a steady periodic state of 30 d (720 h) was 5.85 L/h with average HRT of 5.99 h. The average total chemical oxygen demand (COD) removal e ciency of CSMBR was 89.29% with average organic loading rate (OLR) at 4.16 kg COD/(m3·d) while that of PSMBR was 89.79% with average OLR at 5.50 kg COD/(m3·d). COD concentration in the e uent of both SMBRs achieved the second level of the general wastewater e uent standard GB8978-1996 for the raw medicine material industry (300 mg/L). Hence, SMBR with electronic control backwashing was a viable process for medium- strength Chinese traditional medicine wastewater treatment. Moreover, the increasing rates of preestablished backwashing vacuum, pump frequency, and vacuum and flux loss caused by mixed liquor in PSMBR all lagged compared to those in CSMBR; thus the actual operating time of the PSMBR system without membrane cleaning was extended by up to 1.25 times in contrast with the CSMBR system, and the average total COD removal e ciency of PSMBR was enhanced with higher average OLR.

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