Design of a bioaugmented multistage biofilter for accelerated municipal wastewater treatment and deactivation of pathogenic microorganisms

Abstract

Biological treatment of municipal wastewater for reuse in irrigation is highly required, especially with the current global financial and water shortage crises. Bioaugmentation is a simple and cost-effective technology which could be a useful tool in alleviating this challenge. Thus, this study aimed to enhance the biological treatment of municipal wastewater using a bioaugmented substance supplemented in a three-stages bio-filter consisting of a sedimentation step followed by gravel biofiltration and then sand biofiltration at a laboratory scale. Also, a toxicity assay, the antimicrobial effect of the bioaugmented substance against pathogenic microorganisms, and identification of the synergistic effect of the bacterial consortium involved in the bioaugmented substance were studied. The bioaugmented substance was nontoxic and had an antimicrobial effect against the tested potentially pathogenic microorganisms (Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, and Candida albicans). The minimum effective concentration of the bioaugmented substance for organic, inorganic and microbial pollutants removal from high strength wastewater was 2.5 ppm with a contact time of 6–8 h. The removal efficiencies of H2S, COD, BOD5, total solids (TS), total dissolved solids, total suspended solids, ammonia, nitrate, phosphorus, and oil and grease reached 85, 93.4, 83.5, 37, 49.2, 93.4, 100, 55.7, 76.6 and 76.6%, respectively in the treated effluent after sand biofiltration. The physicochemical parameters of the treated wastewater effluent were below the Egyptian recommended limits (Law 84/1984) for use in irrigation. However, COD and BOD values were 90.33 and 38.46 mgO2/L, respectively, and were still above the regulations (COD ≤60 and BOD ≤20). The high fecal coliforms count in the wastewater influent (8.4 × 108 MPN-index/100 mL) were 95.1% removed after the sedimentation stage, and 99.99% removal was achieved after gravel and sand biofiltration. Thus, this study successfully designed a bioaugmented multistage biofiltration system for the effective removal of pollutants from wastewater, especially in resource-limited areas.