Aerobic Granulation of Micrococcus Aloeverae Strain SG002 and Its Application in Oil Remediation and Polyhydroxyalkanoates (PHA) Production

Aerobic granulation technology is an effective outcome in industrial wastewater treatment. Granulation technique became popular for its simple operation with less space and resource consumption having highly settleable compact sludge granules consisting of numerous pollutant tolerant microbial populations. In oily wastewater treatment, mixed sludge aerobic granules often suffered from slow granulation and rapture in high oil concentration. Micrococcus aloverae strain SG002 isolated from effluent treatment plant of Indian Oil Corporation Limited, Guwahati, India, featured fast self granulation in an aerobic granular reactor (AGR) while treating complex oily wastewater containing 1000 mg/L chemical oxygen demand (COD) and 250 mg/L emulsified diesel. In 50 days, granule biomass concentration and extracellular polymeric substances reached up to 6.34±0.55 mg/L and 216±2.14 mg/g VSS (volatile suspended solids), respectively. Electron microscopic images revealed dense spherical microbial granule structure. Granules were capable of 99±0.23% COD and 95.34±1.12% oil removal within 50 days of operation. However, at the end of feast phase granules produced approximately 312±10 mg/g VSS biodegradable polymer polyhydroxyalkanoates (PHA) which is considered to be an ecofriendy bioplastic. AGR treated effluent was reused for watering Cicer arietinum legume plants. AGR effluent (oil concentration: 12.5±0.5 mg/L) proved to be very less phototoxic providing good plant growth with 0.67±0.011 mg/g F.W (fresh weight) cholorophyll, 0.11 µ mole H₂O₂ split/mg F.W. catalase and 0.056±0.002 Δ Absorbance/mg F.W. peroxidase contents after 4 weeks. Hence, this granulation strategy revealed a new scope in petroleum wastewater treatment with potential biomaterial production and water reuse in agricultural irrigation.