ANAEROBIC TREATMENT OF RAW AND PRECLARIFIED POTATO-MAIZE WASTEWATERS IN A UASB REACTOR

The feasibility of the upflow anaerobic sludge bed process for the tre atment of raw potato-maize waste-water (PMW) of chip-processing indust ry with a high concentration of suspended solids (up to 7 g/l), a high insoluble fr action of COD content (up to 60% of total GOD) and signi ficant quantities of potentially foaming substances, such as proteins and fats, has been demonstrated by operating a 1.8 litre reactor at 35 degrees C. The influent waste strength was 5.3-18.1 g COD/litre, of w hich the soluble fraction was 3.2-7.4 g COD/litre. The organic loading rate (OLR) achieved in this laboratory-scale reactor was approximatel y 14 g COD/litre day with treatment efficiencies higher than 75 and 63 % on the basis of centrifuged and total COD of the effluent, respectiv ely. Some problems with excessive foaming and sludge flotation, as wel l as with accumulation of undigested ingredients that occurred at a hi gh OLR (> 10 g COD/litre day) and moderate hydraulic retention times ( HRT > 1 day), cart be mostly eliminated by applying shorter HRT (< 1 d ay, e.g. by recycling some part of effluent) or temporarily decreasing OLR. The preclarification of raw PMW by applying a commercial floccul ant led to a better reactor operation at an elevated OLR, though the e ffluent quality on the basis of centrifuged COD was practically, the s ame as for the treatment of raw PMW The UASB reactor showed a rapid ad aptation to sharp changes in the OLR without significant losses in the treatment efficiency of both wastewaters. (C) 1998 Published by Elsev ier Science Ltd. All rights reserved.