A comparison of oil and grease removal from automobile workshop stormwater runoff using gravel, granular activated carbon, rice husk and conventional oil and grease (O&G) trap

Oil and grease (O&G) removal efficiencies using 4 automobile stormwater treatment systems were investigated and compared. The treatment systems used were: low-cost granular activated carbon–rice husk (GAC–RH) filter system, river gravel–granular activated carbon (GR–GAC) filter system, rice husk only (RH) filter system and the conventional PVC O&G trap (COT). Sampling of automobile stormwater from the five selected automobile workshops was carried out using the manual grab sampling methods. The treatment involved filtration using the low-cost technologies and O&G separation from stormwater. GAC–RH exhibited the highest O&G removal with an average removal efficiency of 43.2% from all the automobile workshops, followed by RH with an average removal efficiency of 31%. O&G removal using GR–GAC and COT resulted in average removal efficiencies of 28.6% and 26.8%, respectively. Further studies need to be carried out to optimize the GAC and RH low-cost filter materials for the purpose of achieving the USEPA and Nigerian effluent standards of 0.1 mg/L, since all the treatment systems produced effluents with minimum concentrations ranging between 0.8 mg/L and 3.6 mg/L.