Resource recovery in anaerobic microfiltration osmotic membrane bioreactors: liquid fertilizer application

Abstract The anaerobic microfiltration osmotic membrane bioreactors (AnMF-OMBRs) and up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactors (UASB MF-OMBRs) are innovative systems treating high-strength wastewater and recovering resources. The microfiltration (MF) and forward osmosis (FO) permeates of these systems contain varying amounts of nitrogen and phosphorus, which enrich soils and boost crop growth. Utilizing these permeates as fertilizers reduces dependency on chemical fertilizers, conserves natural resources, and valorizes wastewater. This study evaluates the application of MF and FO permeates of an AnMF-OMBR and a UASB MF-OMBR treating slaughterhouse wastewater as liquid fertilizer. Firstly, the permeates were blended with tap water to provide irrigation water quality, considering the national standards. Then, fertigation was applied using the blended MF (NH 4 + -N: 73–95 mg L −1 ; TP: up to 2.6 mg L −1 ) and FO (NH 4 + -N: 3.5–28 mg L −1 ; TP: < 0.5 mg L −1 ) permeates with tap water and their combination with nitrogen, phosphorus, and potassium fertilizers. After 22-day irrigation, analytical hierarchy process was applied to decide the best scenario for grass growth. Grass growth was assessed based on grass colour, soil and plant water retention capacity, coverage percentage, the number of fringes and shoots, and grass and root length. The results showed that the permeates of both bioreactors could be used as liquid fertilizer. Furthermore, in case of one-year full-scale operation of the systems, treating slaughterhouse wastewater, sufficient water was saved for the daily consumption of 240 people. The nutrient quantities in the MF permeates could fulfill 122%, 12%, and 46% of the nitrogen, phosphorus, and potassium needs for grass growth.