Study of a hybrid process combining PACs and membrane operations for antibiotic wastewater treatment

An integrated process combining powdered activated carbons (PACs) with ultrafiltration (UF) and reverse osmosis (RO) was studied for the treatment of waste liquor coming from tetracycline (TC) production. The aim was to purify water and to recover the TC present in the waste stream. Using RO alone, results showed that the concentration of COD and TC in the permeate could be reduced from about 8000 mg.L−1 to less than 200 mg.L−1 and from 850 mg.L−1 to 70 mg.L−1, respectively. However, irreversible fouling occurred that dramatically shortened the lifetime of RO operation. The integration of UF with RO showed that UF could reduce COD from about 8000 mg.L−1 in the feed to 3600 mg.L−1 in the permeate without an effect on TC concentration. The fouling in the RO was reduced, and in addition it could be recovered by a backflushing operation. Experimental results showed that TC recovery efficiency and purity were improved with UF pretreatment. Further studies indicated that the UF–RO performance was improved by addition of PACs to the waste liquor; the optimized amount of PACs was 8.0 mg.L−1, which showed that the permeate flux of RO maintained a high value even when the volume reduction coefficient was up to 3.5. The water collected from RO permeate was significantly purified (TOC = 56 mg·mL−1; COD = 98 mg·mL−1; TC = 46 mg·mL−1) compared to the initial feed solution (TOC = 3200 mg·mL−1; COD = 8000 mg·mL−1; TC = 850 mg·mL−1). The TC present in the RO retentate was recovered by precipitation. The TC recovery efficiency and purity were 72.0% and 88.0%, respectively. The results showed that integrated PACs–UF–RO combined with precipitation can be a promising method to treat the wastewater and recover TC.