Integrated treatment of black wastewater using sedimentation, constructed wetland, and nanoparticles coagulation

The aim of the present investigation was to achieve an efficient treatment for black wastewater for non-restricted reuse. The treatment included sedimentation followed by horizontal flow constructed wetland (HF-CW), and finally chemical coagulation using magnetite (Fe3O4) nanoparticles. For the wetland, the average organic loading rate (OLR) was 42.83 biochemical oxygen demand (BOD)/m2day and 71.30 g chemical oxygen demand (COD)/m2 day, while average surface loading rate was 0.185 m3/m2 day. The obtained results revealed that removal percentage of COD, BOD, and total suspended solids (TSS) by sedimentation followed by processing through wetlands was 80.3, 81.6, and 80%, which corresponds to 76, 42.56, and 54 mg/l, respectively. When magnetite nanoparticles were added to the HF-CW effluent at the optimum dose of 25 mg/l in combination with 10 mg/l FeCl3, the overall removal rate increased to reach 95.9, 99.1, 99.17, 92.3, 94.3, 94.3, and 91.3% for turbidity, COD, BOD, TSS, phosphate (PO4), total nitrogen (TN), and sulphide, respectively. The corresponding residual concentrations were 5 NTU, 8, 5, 32, 0.07, 1, and 1.04 mg/l, respectively. According to the national and international regulations, the present final treated effluent can be safely reused as a non-restricted source for agriculture purposes. The overall results revealed that the implemented study is simple, efficient, reliable, and economical, particularly for remote areas, according to the non-restricted reuse requirements. HIGHLIGHTS Integration of sedimentation/wetland processes is efficient for treatment of blackwater. The removal of pollutants via sedimentation/wetland complies with national regulations. Chemical coagulation using nanoparticles is efficient for treatment of blackwater. The overall removal of pollutants' treatment train complies with the non-restricted reuse regulation.