Study On The Advanced Treatment Of Pharmaceutical Effluent Containing Antibiotic With Integrated Membrane System

The pharmaceutical effluent containing antibiotic( PECA) has high chroma, high salt and high CODCr concentration, which is difficult to reach the industry discharge standard by conventional physical, chemical and biological treatments. As wastewater discharge regulations become more and more stringent, the advanced treatment with integrated membrane technology for reclamation becomes more and more attractive. This paper explored the possibility of the advanced treatment of PECA with coagulation-sand filtration-MF/UF-RO process.The PECA quality was analyzed. Four coagulants performances were compared, and PFS experienced the highest efficiency. Two different coagulation conditions for PFS existed: the dosage (80 mg/L) with the optimum turbidity removal and the dosage (140 mg/L) with the optimum organics removal, which led to different particle distribution.The effect factors of MF and UF processes, the cleaning methods and fouling mechanisms by SEM, EDX, FTIR and GC-MS analysis were studied in laboratory. Coagulation with PFS had great effects on the performance of MF and UF membranes. At the same time, the feed pH, operation pressure, feed flowrate played important roles as well. The minimum MF flux decline was obtained with PFS dosage of 80 mg/L(the dosage with the optimum turbidity removal). The flux decline was suppressed with lower pH and lower operation pressure. Meanwhile, the results also showed that the extent of membrane fouling decreased when the back-wash frequency increased at a constant total consumed water volume. Small flocculates were attributed to MF membrane fouling, highlighting that the organic foulants might contain carboxylic and phenolic compounds. The permeate flux was almost recovered after chemical cleaning with NaOH aqueous solution. On the other hand, the minimum UF flux decline was obtained with PFS dosage of 140 mg/L(the dosage with the optimum organics removal). The flux decline was suppressed with lower pH, lower operation pressure and higher feed velocity. The main fouling substances of UF membrane were organics, which could be removed by chemical cleaning with two different reagents. The permeate turbidity of MF and UF membrane was below 0.5 NTU, and the permeate SDI15 was lower than 1, which could meet the RO feed requirement. The permeate flux of MF was almost double of that of UF, and the coagulant dosage for MF pretreatment was almost half of that for UF pretreatment. On the basis of the above experiments, coagulation-sand filtration-MF-RO process in a pilot-scale was carried out systemically. The average removal of SS and CODCr by coagulation unit were 86.6% and 32.8%, respectively. The average removal of NH3-N, turbidity and CODCr by MF unit were about 31.8%, 98.4% and 23.2%, respectively. Regardless of the variations of feed qualities, the SDI15 of MF filtrate was lower than 5. The flux of MF was 50～65 L/m2.h with the operation pressure at 0.06MPa. The coagulation-sand filtration-MF process could provide stable and eligible feed for sequent RO membrane. The rejection of RO membranes used for total salt, CODCr and sulphates were higher than 97%, 95% and 92%, respectively. Appropriate chemical cleanings could recover MF and RO membrane performance. The results indicated that NaOH aqueous solution cleaning and air wash could recover the MF membrane flux. Meanwhile, the two step cleaning procedure including acid cleaning and alkali cleaning was effective for recovering RO membrane performance. The permeate quality of the RO membranes could meet the reuse water requirement. On the basis of the above study, a plant with 50 T/h product water was designed. It shows that the plant has good economic benefit and remarkable social benefit.