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Pretreatment of palm oil mill effluent by electrocoagulation and coagulation

Chantaraporn Phalakornkule^a,b,*, Juntipa Mangmeemak^b, Kanita Intrachod^b, Boonyarit Nuntakumjorn^a

 
ABSTRACT:     Palm oil mill effluent (POME) is wastewater generated from the palm oil milling process. It is regarded as a highly polluting wastewater as it has a high chemical oxygen demand (COD), and contains high levels of oil and suspended solids. Pretreatment of POME is desirable before a subsequent biological or other treatment. This paper reports a study of POME pretreatment by (1) electrocoagulation and (2) conventional coagulation with Al₂(SO₄)₃. At an optimal condition with a current density of 20 A/m² for 5 min at 313 K and pH 5, the percentage of oil, COD, suspended solids, and total solids removal by electrocoagulation were 72%, 64%, 53%, and 43%, respectively. The electrical consumption under this condition was in the order of 0.10 kWh/m³. The addition of NaNO₃ improved the electrocoagulation, and it may also be beneficial for a subsequent biological treatment. At high current densities and/or long electrocoagulation time, POME treatment produced bubbles, which decrease the efficiency of oil removal. This effect did not occur in conventional coagulation. However, chemical coagulation limits oil removal from POME due to the effect of pH. Overall, electrocoagulation should cause less environmental damage than conventional chemical coagulation by Al₂(SO₄)₃ as it treats POME without the need to add sulphate ions.

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* Corresponding author, E-mail: cpk@kmutnb.ac.th, cphalak21@yahoo.com

Received 26 Oct 2009, Accepted 6 May 2010