Assessment of the anaerobic baffled reactor for treatment of vegetable oil effluent

Abstract

The vegetable oil industry produces effluent containing quantities of fat, oil, sodium, phosphates as well as other pollutants. Oils and greases tend to clog sewers and pumps, thus creating difficulties within the municipal wastewater treatment works. Physico-chemical treatment methods, such as (Dissolved Air Flotation) OAF, gravity separation and the use of coagulants have been attempted providing a considerable reduction in organic loading; however, discharge standards are still not met. Thus, biological treatment methods are being sought after. Aerobic treatment has been attempted however, shock loads cause problems while running such a process. The objective of this study was to assess the efficiency of anaerobic digestion to degrade Vegetable Oil Effluent (VOE) as well as the efficiency of the Anaerobic Baffled Reactor (ABR). Anaerobic digestion involves the breakdown of organic matter by the action of microorganisms in the absence of oxygen, producing methane-rich biogas. The VOE was characterized, providing significant information on its chemical composition. It was found that the effluent had high sulphate content as well as a high COD content. High sulpahte content of wastewaters have known to promote growth of Sulphate Reducing Bacteria (SRB), which utilize the same energy source as Methane Producing Bacteria (MPB) and therefore compete for the same energy source. Sulphate and lipid reduction pretreatment experiments were carried out, using barium chloride and gravitational separation respectively. The results obtained, showed that the use of barium chloride to reduce sulphate content in VOE was successful, with significant sulphate reduction. The lipid reduction experiments however, did not show any significant lipid reduction. Batch tests were conducted in serum bottles to assess the extent of biodegradation of the VOE in its raw state as well as with reduced sulpahte content. Methanogenic toxicity tests on the raw and pretreated VOE provided a range of toxicity results. These assays are relatively simple and inexpensive. Gas production was monitored to determine the rate and extent of biodegradation. The efficiency of digestion was assessed by COD reduction. Results indicated potential inhibition of the methanogenic bacteria responsible for methane production by the