The effect of hydraulic retention time on microalgae-based activated sludge process for Wupa sewage treatment plant, Nigeria

摘要

This study evaluated the efficiency of microalgae activated sludge (MAAS) for wastewater treatment by investigating the influence of hydraulic retention time (HRT) on MAAS using batch regime pilot scale photobioreactors at Wupa Wastewater Treatment Plant. The outcome of the study showed that MAAS has a comparably high wastewater treatment performance in comparison with the current Wupa Wastewater Treatment Plant (WWTPA) activated sludge (AS) method and is capable of treating wastewater to the defined Nigerian effluent standards. It was further revealed that treatment performance for most parameters were optimal from HRT3 (6-day hydraulic retention time). Precisely, total nitrogen (TN), total phosphorus (TP), and BOD5 had highest removal efficiency at HRT3 with average total removal of 81.36%, 91.77% and 87.04% respectively. Correspondingly, the average percentage DO increment peaked at HRT3 with a value of 269.7%. In addition, there was a general deterioration of SVI with increasing HRT, particularly after HRT2 (4-day HRT). Notably, SVI30 was significantly good at HRT1 and HRT2 with SVI values of 48.6 ml/g and 105.52 ml/g; however, from HRT3 down to HRT9, the SVI30 became remarkably increases greater than that of HRT1 and HRT2, with values ranging from 685.61 to 1832.46 ml/g, which indicates a badly bulking sludge. The MAAS system is recommended as an attractive alternative to the conventional AS wastewater treatment in Nigeria and by extension West African subregion.