Biological nitrification and denitrification of opto-electronic industrial wastewater

Development and application of biological nutrient removal processes accelerated significantly over the past decade due to more stringent nutrients (nitrogen and phosphorus) discharge limits being imposed on wastewater treatment plants. The opto-electronic industry has developed very fast over the past decade in the world. The wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio of over 95% in organic nitrogen (Org-N) to total nitrogen (T-N). In this study, a 2-stage Anoxic/Aerobic pre-denitrification process was established and the efficiency of wastewater treatment was evaluated. Wastewater from an actual LCD-plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment. Hydraulic retention time (HRT) and mixed liquor recycle rate (MLR) were controlled independently to distinguish between the effects of these two factors. Under suitable HRT and mixed liquor recycle ratio, effluents of NH4-N, NOx-N and COD can fall below 20 mg/l, 30 mg/l and 80 mg/l.