Enhancement of the biodegradability of grain distillery wastewater to improve upflow anaerobic sludge blanket reactor efficiency

[摘要] The distillery industry generates large volumes of heavily polluted wastewater and thuseffective wastewater treatment is essential. It has been reported that a chemical oxygendemand (COD) reduction of more than 90% can be achieved when wine distillery wastewater(WDWW) is treated in an upflow anaerobic sludge blanket (UASB) reactor. The first objectiveof this study was to investigate UASB treatment of WDWW and to try to enhance theefficiency by using ozonation treatments. Secondly, the impact of grain distillery wastewater(GDWW) on UASB granules was determined. The third objective was to determine whetherozonation and enzymatic treatment combinations might improve the biodegradability ofGDWW and thus make GDWW more amenable to UASB treatment.It was found that UASB treatment combined with ozonation improved the WDWWtreatment efficiency. When diluted WDWW (chemical oxygen demand COD = 4 000 mg.L-1)was ozonated (dose = 47 mg.L-1) in a 50 L venturi circulating contactor system, the CODreduction was 7%. When WDWW was treated in a laboratory-scale UASB reactor (substratepH = 7.0, COD = 4 000 mg.L-1 and organic loading rate (OLR) = 4.0 kg COD.m-3.d-1), theCOD reduction was 92%. When the UASB treatment was combined with either pre- or postozonation,the COD reduction was 94 and 96%, respectively. When UASB treatment wascombined with pre- and post-ozonation, a COD reduction of 98% was achieved. The activityof the UASB granules was also found to improve over time, despite the addition of theozonation treatment.It has been reported that operational problems occur when GDWW is treated in anUASB reactor as a result of the encapsulation of the granules. This was confirmed whengranules from a full-scale UASB treating WDWW became encapsulated in a layer after beingexposed to GDWW (COD = 4 000 mg.L-1) for 24 d. The results showed that the lipid contentof the granules increased from 1.25 to 60.35 mg lipid.g-1 granule over the 24 d exposureperiod. Therefore, granules exposed to GDWW were encapsulated in a lipid-rich layer and asa result the contact between the GDWW and microbial consortium in the granules wasreduced. The operational problems found during the industrial UASB treatment of GDWWwere ascribed to the encapsulation of the granules.Combinations of ozonation (dose = 1 476 mg.L-1) generated in a 2 L bubble columnand enzymatic treatments (1% FogFreeTM (FF) dosage and 2 d incubation at 35°C) were found to improve the biodegradability of GDWW. This improvement was in terms of lipidreduction in GDWW, granule activity and visual appearance of the encapsulating layer of thegranules. The highest lipid reduction (90%), highest granule activity, lowest lipid content ofthe granules (3.74 ± 0.10 mg.g-1 granule) and best visual appearance were achieved inozonated GDWW treated with 1% FF, followed by just ozonation. The higher lipid reductionand subsequent higher granule activity were ascribed to the reduction in lipids which resultedin the fact that fewer lipids were available to encapsulate the granules. As a result of the lipidreduction, the granule activity improved and the GDWW was made more amenable to UASBtreatment.This study proved that UASB treatment combined with ozonation led to anenhancement of the treatment efficiency of WDWW. It was also found that the cause of theoperational problems during UASB treatment of GDWW was as a result of the granules beingencapsulated in a lipid-rich layer. It was established that treating GDWW prior to UASBtreatment improved the biodegradability of GDWW. The data from the study showed thathigh lipid reduction in the GDWW directly led to better granule activity, lower granule lipidcontent and a thinner encapsulating layer. Based on the data from this study, it isrecommended that GDWW be ozonated prior to other treatments because it can be done inlineand the costs would be lower than that of enzymatic treatments.

[发布机构] Stellenbosch University