Bacterial bioaugmentation as an efficient approach to enhance the quality of activated sludge-treated effluent

ABSTRACT The present study aimed to investigate the ability of four bacterial isolates to polish and enhance the quality of activated sludge (AS)-treated effluent for potential reuse using bioaugmentation technology following the AS treatment. The expected future increase in the wastewater flow and organic matter load due to the increase in the handling rate of huge containers with more equipment at Alexandria Containers and Cargo Handling Company (ACCHC) necessitate searching for new approache(s) to be integrated with the established AS treatment in order to enhance secondary effluent quality for potential recycling. Four indigenous bacterial candidates (AI 11, AI 12, AO 11, and AO 12) were isolated from the raw wastewater and screened in batch mode to select the most efficient for polishing the secondary effluent. Results indicated variant capabilities among the candidates for the removal of the tested parameters with AO 11 and AO 12 considered the most efficient. They achieved the highest removals (63.39%, 88.66%, 84.32%, and 92.77%) of total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and oil and grease (OG) from initial concentration (IC) of 112, 97, 185 and 7.33 mg L -1 , respectively. Also, AO 12 produced highest total dissolved solids (TDS) increase (IC: 570 mg L -1 , 15.79%) indicating high biodegradation ability. AO 11 and AO 12 were selected for bioaugmentation of AS-treated wastewater as individual and mixed culture in a free-living batch mode. AO 11 achieved the highest removal of 52.08%, 37.84%, 32.85% and 74.79% for TSS, BOD, COD, and OG as well as the highest TDS increase (50.82%) from ICs of 96.0, 74.0, 137.0, 8.53, and 610 mg L -1 , respectively reaching safe limits for discharging according to their maximum permissible limits (MPLs) stated by the laws. GenBank accession number (NR0428611) with the highest sequence similarity (99.91%) as well as the closest neighbor(s) to the 16S rDNA gene partial sequences identified AO 11 as Paenibacillus dendritiformis strain T168. Results present effective, economic and fast solution to enhance the quality of the AS-treated effluents. The study also recommend augmentation of P. dendritiformis in the activated sludge unit or as a separate biofilm unit following the AS treatment in order to protect the environment and recycle the produced water in a wider sense and locally to cope with the expected enlargement in the wastewater flow of the ACCHC company.