Investigating the effect of wine and distillery wastewater on the efficacy of an upflow anaerobic sludge blanket (UASB) and enhancing biomass immobilisation by the addition of magnetisable foam glass particles (MP)

[摘要] ENGLISH ABSTRACT: The wine and distillery industry is one the largest contributors in the production of wastewater worldwide. The effluent produced from this industry is classified as high strength wastewater and does not comply with local regulations. Treatment of these effluents is therefore mandatory if it is to be reused or pumped back into the ecosystem. The upflow anaerobic sludge blanket (UASB) has been found to be one of the most successful technologies in treating high strength wastewater, particularly wine and distillery wastewater. Therefore the first objective of this study was to investigate the effect of combined wine, marula and Brandy wastewater on the operation and efficacy of a UASB reactor. In order to simulate the production seasons of the three different waste streams, a feeding strategy was developed where the trial was divided up into different phases. The chemical oxygen demand (COD) reduction percentage throughout each phase remained at an average of 85% and above, as the organic loading rate (OLR) increased from 1 kg COD.m-3.d-1 (phase one) to 10 kg COD.m-3.d-1 (phase four). The biogas production increased from an average of 0.6 L.d-1 (phase one) to 10 L.d-1 (phase four) as well as the methane percentage that showed a similar trend; as the OLR increased throughout the trial so did the methane percentage. The pH and the alkalinity remained stable throughout the trial; however as the OLR reached 6 kg COD.m-3.d-1 some difficulties did occur as the pH dropped to below 5. The reactor was therefore monitored more closely as the OLR increased.The success of the UASB reactor is found in the retention of anaerobic bacteria that are responsible for the digestion of the substrate. Retention occurs as the anaerobic sludge forms aggregates, also referred to as granules, which can withstand the upflow velocity of the incoming substrate. The loss in biomass does however still occur. Therefore the second objective of this study was to investigate whether added magnetisable foam glass particles (MPs) would be a viable medium for biomass attachment to aid in the immobilisation of granular biomass. The third objective was to investigate whether the added MPs would affect the operation and efficacy of the UASB reactor. Scanning electron microscopy (SEM), fluorescent microscopy analysis and activity tests were done on the MPs after a seven month period within a UASB reactor. SEM results showed microbial attachment and colonisation on the surface of the MPs, a distinct difference was found when comparing an uncolonised MP to a fully colonised MP. A fully colonised particle displayed a large variety of organisms attached to its surface and the morphology of these organisms gave an indication that methanobacterium, methanoplanus, methanosaeta, methanobrevibacterium and methanosarcina were present on the surface of the MPs. The attachment and colonisation of bacteria onto the surface of the MPs were confirmed by the results obtained by the fluorescent microscopy analysis. Fluorescence was found after the particles were stained with SYTO 9, a green fluorescent dye that stains the nucleotides of bacterial cells. These results confirmed colonisation of a mixed consortium of bacteria onto the surface of the MPs. Methanogenic attachment was confirmed by autofluorescence; as the MPs were exposed to specific wavelengths of UV a blue colour was observed where methanogenic attachment occurred. Activity tests were performed to investigate whether the MPs produced biogas and methane. Biogas production was found in all three mediums used, which again confirms both the presence of acidogenic as well as methanogenic activity. With the addition of the MPs to the one UASB reactor (RMP), there was no initial influence on the operation of the reactor, however as the OLR reached 6 kg COD.m-3.d-1 and above the pH and alkalinity of Rcontol decreased significantly on three different occasions during the trial whereas this was not found in RMP. Another difference between RMP and Rcontrol was found at the end of the trial when the granular biomass was removed from the reactor. The granules in Rcontrol were much larger the granules from RMP, furthermore the majority of the biomass was in a floccular form rather than granular. Based on the data from this study the digestion of combined wine and distillery effluent is possible, however the reactor should be carefully monitored as the OLR increased above 6 kg COD.m-3.d-1. This study has also proven that using MPs as a medium to improve biomass retention is a viable option, furthermore the addition of MPs to a UASB reactor might have a positive effect on the digestion of high strength wine and distillery wastewater.

[发布机构] Stellenbosch University