Evaluation of UASB effluent post-treatment in pilot-scale by microalgae HRP and macrophytes pond for nutrient recovery

Abstract

The partially treated effluents discharge into water resources impacts water quality and living beings. These effluents contain nutrients such as phosphorus and nitrogen, which can promote the eutrophication of water sources and, consequently, the development of microalgae and macrophytes at levels above the environmental balance. However, the control of these photosynthetic beings can reduce and even prevent the eutrophication. The present work aims to evaluate the removal and recovery of nutrients from effluent treatment through high rate microalgae ponds (AP) and treatment ponds with the presence of macrophytes (MP) in two steps. In step I, the ponds were operated individually (parallel period), in step II they were operated in sequence, where the effluent from the AP to directed to the MP (series period). On the two steps, the performance evaluation regarding the climatic conditions to divide into two periods: warm (summer and spring) and cold (autumn and winter) and the HDT of 2.2, 3.3, and 4.1 days in each pond to evaluate the removal and recovery of nutrients from Algae Pond (AP) and Macrophyte Pond (MP), cultivation ponds fed with sanitary effluent pretreated by an Upflow Anaerobic Sludge Blanket reactor (UASB). The main results for nitrogen and phosphorus removal and recovery were for 4.1 days Hydraulic Detention Time in the warm period for the series system, reaching values below 1.0 mg/L for phosphorus and close to zero for ammonia nitrogen; non-detection by analysis method. For nutrient recovery, the maximum values found were 0.12 g/m 2 ⋅day for phosphorus and 0.79 g/m 2 ⋅day for nitrogen.