Comparative evaluation of a laboratory and full-scale treatment alternatives for the vegetable oil refining industry wastewater (VORW)

Biomass washed out from an expanded granular sludge bed (EGSB) reactor treating oleate (82%, w/w) was inves-tigated. This biomass had a 50% higher activity compared to granules present in the EGSB reactor. Recirculationof washed out biomass into reactor remarkably improved the treatment performance. The highest methane conversion rate from oleate, 300 mg CH4-COD/g VSS.d, was achieved at a concentration of 4 g oleate-COD/l and a volumetric loading rate of 8 g COD/l.d.

Thermophilic high-rate anaerobic treatment of wastewater containing long-chain fatty acids: Effect of washed out biomass recirculation.

This study investigates the conventional characterization and biological treatability of two different wastewaters that originated from corn oil and sunflower oil refining processes. Our aims for characterization of wastewaters included: total and soluble chemical oxygen demand, total and soluble biological oxygen demand, suspended solid, oil and grease, pH, total kjeldahl nitrogen, ammonia nitrogen, total phosphor, phosphate, color and sulfate analyses. In corn oil wastewaters, total COD is portioned as 80% soluble COD, 20% particular COD, 3.4% total soluble inert COD, 0.5% total particular inert COD, whereas in sunflower oil wastewaters soluble COD, particular COD, total soluble inert COD, total particular inert COD are found as 81.7%, 18.3%, 1.9%, and 5.1%, respectively. In our characterization studies, BOD5/COD ratio were 0.15 and 0.2 for corn oil and sunflower oil wastewaters, respectively. These results indicate that wastewaters are not suitable for biological treatment. But investigation of COD fractions has pointed out that wastewaters contain mostly biodegradable organic substances.

Characterization and biological treatability of edible oil wastewaters

Wastewater discharged from the edible oil industry contains a very concentrated amalgamation of organic and inorganic materials making it a problematic effluent to treat. The aim of this study was to evaluate the activated sludge treatment of edible oil effluent from a sunflower oil processing company in KwaZulu-Natal. A 28 l laboratory-scale modified Ludzack-Ettinger (MLE) activated sludge process was used to treat refinery effluent from the industry. Pre-flocculation of the effluent was necessary to remove the bulk of the fats, oils and greases (FOG) prior to treatment. Routine analyses of chemical oxygen demand (COD), total nitrogen (N), total phosphorus (TP), total suspended solids (TSS), dilute sludge volume index (DSVI) and FOG were conducted in conjunction with microscopic analyses of floc structure, filamentous bacteria and protozoa. An average COD removal of 81% was obtained for the flocculated effluent, at a 15 d sludge age and 24 h hydraulic retention time. However, significantly high TSS values were observed in the treated effluent as a result of sludge-oil aggregation, pin-point floc formation and high numbers of freeswimming bacteria. Microscopic analysis confirmed an absence of filamentous bacteria resulting in poor floc formation, subject to shearing. Periods of soybean oil effluent addition, however, resulted in sludge bulking with DSVI measurements as high as 770 ml /g. Fluctuating protozoan populations were also correlated to fluctuating TSS values and were found to be negatively impacted by uncontrolled pre-flocculation. Water SA Vol.29(3) 2003: 245-250

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H. A. San

Papers

Comparative Evaluation of Treatment Alternatives for Wastewaters from an Edible Oil Refining Industry