Wastewater treatment of bottle oil washing water (BOWW) by hybrid coagulation–flocculation and biological process

The efficiency of physico-chemical and biological combined treatment processes of bottle oil washing wastewater (BOWW) was investigated. The coagulation and flocculation process followed by activated sludge treatment was carried out in order to produce a suitable chemical oxygen demand (COD) and oily effluent in conformity with the regulatory standards. Attempts were made in this study to examine the effectiveness of the coagulation and flocculation process using aluminium sulfate and polyelectrolyte (non-ionic preastol) for the treatment of BOWW. The removal of organic matter (COD), oil and color using Al2(SO4)3·18H2O and preastol during coagulation–flocculation process was investigated. Also, the optimum conditions for the coagulation–flocculation process, such as coagulant dosage, polyelectrolyte dosage, and solution pH were investigated using jar-test experiment. Results revealed that in the tested pH range tested, the optimal operating pH was 6.5. Removal percentage of 87, 95, and 97% for COD, oil and color, respectively, and were achieved by the addition of 180 mg/L Al2(SO4)3.18H2O, whereas 87, 99, and 99%, were achieved with the addition of 1 g/L preastol to 180 mg/L Al2(SO4)3·18H2O. The treatment of oily wastewater by an aerobic biological process was conducted using acclimated consortium and lipolytic strain isolated from lipidic effluent. The results of this investigation show that the system is capable of achieving high levels of purity; 93% COD removal, 99% oil removal, and 92% color removal. A comparison between the results shows that the physico-chemical single system was more improved than the physico-chemical and biological combined treatment. It can be concluded from this study that coagulation–flocculation may be a useful pre-treatment process for beverage industrial wastewater prior to biological treatment.