PRETREATMENT OF PHARMACEUTICAL WASTEWATER BY INTERNAL MICRO-ELECTROLYSIS AND COAGULATION

Pharmaceutical wastewater from hypo soda production is characterized by high concentrations of chemical oxygen demand (COD), suspended solids (SS), chrominance, as well as poor biodegradability and microbial toxicity. Therefore, it is not suitable to be treated directly with biological processes. In this study, internal micro-electrolysis combined with coagulation was used to pretreat the wastewater before the biological processes. Primarily, the optimal operational conditions for iron-carbon internal micro-electrolysis were determined. With these parameters, continuous tests were then developed and polyacrylamide (PAM) was added in a concentration of 5 mg/L wastewater as coagulant to study the efficiency of internal micro-electrolysis and coagulation treating COD, S super(2-), chrominance and total nitrogen (TN). The results showed that the best operational parameters of the internal micro-electrolysis to remove COD and chrominance were pHs of 2.063.0, mass ratio of Fe/C = 30/1, reaction time of 120 min, and 0.1 mm diameter of scrap iron. The pretreatment averagely removed up to 66.6% COD, 98.3% S super(2-), 85.1% chrominance and 25.6% TN from the wastewater, respectively, and enhanced the biodegradability of wastewater from 0.16c0.02 to 0.41c0.02. Moreover, microbial toxicity of contaminants was eradicated, which made sure the stable operation of subsequent biological processes. This pretreatment method was put into effect in a pharmaceutical plant. Long-term monitoring results from the full-scale application supported that iron-carbon internal micro-electrolysis and coagulation was applicable to pretreat pharmaceutical wastewater from hypo-soda production.