Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant

Abstract

Abstract Due to the disposal of different wastewater into the water bodies, the rate of surface water pollution is increasing. The virginia initiative plant (VIP), one of the most efficient and economical wastewater treatment systems, was assessed. The experiments were carried out by a laboratory-scale VIP system used for this study, with a flow rate of 100 L/day and a solid retention time rate estimated at 10 days. The system works on three different ratios for internal rotation (100, 150, and 200%) and three for external rotation (80, 90, and 100%), and the effective volumes were 20, 40, and 60 L for anaerobic, anoxic, and oxic reactors, respectively. The results showed that the VIP system achieved the best removal efficiency of organic matter represented by COD, phosphorous, and ammonia (86, 94, and 93%, respectively). The impact of internal and external rotation ratios was tested by removing COD, phosphorous, and ammonia. The percentages of internal rotation significantly affect the biological removal of nitrates. The relationship between them is inverse, while the percentages of external rotation significantly impact the biological removal process of phosphorus. The relationship between them is positive, whereas the internal and external rotation percentages did not considerably affect the efficiency of removing both ammonia and COD. According to the research results, internal and external rotation ratios enhanced the removal efficiency of phosphorus and nitrates. The VIP system proved to be an effective method for domestic wastewater treatment with a flow conforming to Iraqi standards for draining wastewater with all organic matter, phosphorous, and nitrogenous compounds to rivers.