Quantitative evaluation of the effect of parameters affecting biological and physicochemical phosphate removal from wastewaters in a Multi-Soil-Layering system

Abstract

Wastewater disposal is a serious problem in Moroccan rural area. Discharged with high levels of phosphorus and nitrogen can result in eutrophication of receiving waters. Biological processes are the most adapted alternative to the needs of these areas, such as the Multi-Soil-Layering (MSL) system. The process of rural wastewater treatment by MSL, which is an innovative system used for the first time in Morocco, was studied by modelling the relationships between a set of environmental factors and total phosphorus removed, based upon 153 sampling. Three MSL pilot plants, constructed in three 36 cm × 30 cm × 65 cm plastic boxes, were continuously fed with domestic wastewater, with different hydraulic loading rate (HLR) of 250, 500 and 1000 l/m2/day. This study was to investigate and quantify the effect of parameters affecting biological and physico-chemical phosphate removal from wastewaters in this system, using neural networks (NNs) and multiple regression analysis (MRA). The results show the influence of the hydraulic loading rate (HLR), Hydrogen potential (pH), phosphorus load (PL), nitrite (NO2--N), Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5), and the Nitrate-nitrogen (NO3–-N) in the phosphorus removal with a contribution of 36, 16, 15, 12, 9, 7 and 6% respectively.