Development and adoption of wastewater treatment system for peri-urban agriculture in Multan, Pakistan

The present research was conducted to assess the feasibility of biological treatment of a typical wastewater (WW) stream in Multan, Pakistan, using daily trends of WW characteristics and to design a wastewater treatment (WWT) system for that stream. The pH (5.8–6.2), temperature (24–30 °C), biological oxygen demand (BOD5: 128–265 mg/L), ultimate BOD (BODu: 227–438 mg/L), BOD/total Kjeldahl nitrogen (BOD5/TKN:5.9–11.2), BODu/BOD5 (1.6–2.0), carbonaceous BODu/nitrogenous BODu (CBODu/NBODu:1.6–2.8) of the WW was found to support the biological WWT. The inclusion of NBOD also indicated the need for nitrification-denitrification. The linear regression analysis of volatile suspended solids (VSS) with total suspended solids (TSS) indicated the high content of organic solids, which also made the WW suitable for biological treatment. The BOD/COD (chemical oxygen demand) <0.8 indicated the requirement for biomass acclimation. The major process units of the WWT system developed included a primary clarifier, cascade aeration, trickling filter, adsorption filter and chlorination contact tank. During the validation of design procedures, considerable removal of TSS (91%), TDS (46%), BOD5 (88%), COD (87%) was observed over the 15 week operational period of the secondary WWT system. The WWT system developed was appropriate as a sustainable WWT system that consumed less energy and had lower operational costs.