Pharmaceutical Wastewater Treatment With Electrochemical-biological Method

Systematic analysis of the sources and characteristics of the pharmaceutical waste water was conducted. Based on the experience of practical projects, we found that it was unfeasible to treat the pharmaceutical wastewater only with biological methods. Because of high COD and recalcitrant organic compounds in pharmaceutical wastewater and effectiveness and ease in operation of electrolysis, an schemes of electrolysis-biochemistry was established.Experiments were conducted to study the role of electrolysis in removing chromaticity and COD and improving the biodegradability of pharmaceutical wastewater. The objective of this paper is to advance the knowledge of the influence of residence time, polar distance, initial wastewater concentration, voltage, pH and electrolyte on the electrolysis efficiency. The results showed that the use of electrolysis technology could remove more than 94% of chromaticity and 36.1% of COD and improved the biodegradability of pharmaceutical wastewater from 0.24 to 0.36 at 30 voltages. 9 of pH value could be advantageous to the removal of chromaticity. A retention time of 30 minutes was recommended for the process design of electrolysis.So far, many investigations have been focused on direct anodic oxidation of pollutants in electrochemical treatment. It should be noted that chloride is widely presented in many wastewater and potentially, it can be oxidized to form chlorine during an electrochemical oxidation process, which may be a promising technology for the treatment of organic wastewaters due to increase of chromaticity and COD removal. The main reaction occurring during the anodic oxidation in the presence of NaCl are:Anode: Cr+2OH-->OCr+H2O + 2e~ (1)4OH ~ -> 2H2O + O2 + 4e~ (2)Cathode: 2H2O + 2e~ -*H2 + 2OH~ (3)In this investigation, the effects of NaCl on removing chromaticity and COD of pharmaceutical wastewater were studied. Study was also done to advance the knowledge of the influence of NaCl dosage on the electrolysis efficiency. Compared with the effects of Na2SC?> NaNCb on the electrolysis efficiency, the results showed that the COD removal can be mainly attributed to the indirect oxidation effect of NaCl in electrolysis process. In practical pharmaceutical wastewater treatment, the results indicate that the use of NaCl can achieve higher COD removal. In addition, the existence of ammonium would result in a decreased COD removal efficiency.After the pre-treatment of pharmaceutical wastewater with electrolysis, the liquid was filtrated and then was added to biological reactor. Compared with the pharmaceutical wastewater without electrolysis, results showed that the biodegradability of pharmaceutical wastewater was improved and the removal rates of both chromaticity and COD were increased.