An integrated process of Fe/C micro-electrolysis-anaerobic hydrolyze-microalgae for treatment of high concentration pharmaceutical wastewater

Abstract

As a high concentration wastewater of high organic matter content, many toxic substances, large amounts of organic solvents and poor biochemistry, pharmaceutical wastewater is challenging to handle with a single water treatment technology. In this study, a combined process of Fe/C micro-electrolysis (Fe/C-ME)-anaerobic hydrolyze-microalgae was developed to treat high-concentration pharmaceutical wastewater (i.e. 100,000 mg/L chemical oxygen demand (COD), 2800 mg/L ammonia nitrogen (NH3-N) and 130 mg/L total phosphorus (TP)). Firstly, in the Fe/C-ME process, under optimal experimental conditions, the removal rates of COD, NH3-N and TP were 55 %, 36 % and 63 %, and it was worth mentioning that the removal of ammonia nitrogen and total phosphorus may be attributed to the complexation and flocculation of hydrated iron ions. Secondly, the outer circulation anaerobic reactor (OCAR) performed biochemical treatment on pretreated pharmaceutical wastewater, 85 % of COD was removed, and it was found that through anaerobic digestion, and further hydrolyzed and acidified macromolecular pollutants into small molecules to reduce the impact load, which was conducive to the subsequent digestion and absorption of microalgae and improved the treatment efficiency of the aerobic section. The microalgae cultivated by heterotrophy using anaerobic effluent, directly used NH3-N and TP in wastewater to synthesize substances needed for self-growth and reproduction, and removed 88 %, 91 % and 83 % of COD, NH3-N and TP, respectively. The final results indicated that the removal rates of COD, NH3-N and TP in the integrated process of Fe/C-ME-anaerobic hydrolysis-microalgae were 99.8 %, 98.6 % and 98.5 %, respectively, demonstrating that the coupling process is an effective method for treating high-concentration pharmaceutical wastewater.