Removal of nutrients in sequential batch polishing ponds in the post-treatment of UASB reactor effluent

ABSTRACT

The indiscriminate release of nutrients into water bodies can lead to the process of eutrophication of these bodies; thus, the prior removal of nitrogen and phosphorus must be sought. An alternative that can satisfactorily perform this role is Sequential Batch Polishing Ponds (SBPP) post-treatment of upflow anaerobic sludge blanket (UASB). The pH in these ponds tends to rise, leading to ammonia desorption and phosphorus precipitation. Thus, the present work aimed to deepen the study of UASB + LPBS addressing the importance of pH in the removal of nitrogen and phosphorus, and to evaluate the influence of depth and temperature on Hydraulic Detention Time (HRT). LPBS was operated for 12 months in the city of Campina Grande, Paraíba, comprising the hot (HP) and cold (CP) periods, with an average temperature of approximately 25 and 21°C, respectively, and evaluating four lakes, L1, L2, L3, and L4 with depths of 0.2, 0.4, 0.6, and 1.0 m, respectively. The efficient anaerobic treatment allowed the pH increase in the LPBS regardless of the period of the year, and the process was favored at lower depths. Ammonia removal was complete, regardless of depth and time of year, with 3, 7, 10, and 25 days for HP and 6, 14, 18, and 27 days for CP. Phosphorus removal occurred efficiently, especially when shallower ponds were used in both periods, although the process is favored during the HP, resulting in a lower TDH, thus requiring a smaller area in this period.

Keywords:
polishing ponds; removal of nitrogen; removal of phosphorus