Anaerobic bioconversion of liquid and solid wastes from the winemaking process

[摘要] ENGLISH ABSTRACT: South Africa is a developing country that relies on its agricultural sector as a main source of overalleconomic welfare. Development does not only give rise to new technology and new products butalso results in increased amounts of liquid and solid waste.Generally, the production of wine is considered an environmentally friendly process, butsignificant amounts of natural resources and organic amendments are necessary, while generatinglarge amounts of liquid and solid wastes. Anaerobic digestion (AD) is an attractive and proventreatment option for both liquid and solid wastes as valuable products and depollution can beobtained. AD of liquid waste results in an effluent and biogas, while anaerobic composting of solidwaste results in an organic amendment, leachate and biogas.The overall objective of this study was to investigate the operational feasibility of the cotreatmentof leachate produced during the anaerobic composting (AnC) of grape skins in an upflowanaerobic sludge blanket (UASB) reactor while treating winery wastewater. This first aim of thisstudy was to investigate the efficiency of the anaerobic composting of grape skins. Laboratoryscaleddigesters (1L) were utilised as anaerobic composting units. The most important operationalparameters were identified (pH, moisture content and inoculum (size, ratio, composition)) in orderto produce a pH stable, odour free compost in 21 days.Experimental studies highlighted the importance of shredding waste as well as the additionof calcium oxide and green waste to increase the initial pH of the composting mixture. Afteroptimising a 50% (m.m-1) cow manure inoculum, lower inoculum concentrations (10, 15 and 25%(m.m-1)) were investigated to make the process more economically viable. A 10% (m.m-1)anaerobic compost (AC) inoculum was found to produce the most favourable results in terms of pHstabilisation and leachate generation. A 50% (m.m-1) moisture level performed the best byattaining a pH > 6.5 on day 6 and having the highest end pH (7.65) on day 21, while white and redgrape skins in an equal ratio were found to generate a higher end pH. With all these optimumparameters in place (shredded waste, green waste, CaO, inoculum, moisture, grape skins), acompost with a final pH (7.09), moisture (58%), nitrogen (2.25%), phosphorous (0.22%) andpotassium content (1.7%) was obtained. The optimised parameters were scaled-up (1:10) byusing polyvinyl chloride anaerobic digesters (20 L) to suit the operational requirements of the AnCprocess and also produced a stable compost within 21 days. The second aim of this study was to investigate the combined anaerobic digestion of winerywastewater (WWW) and leachate obtained from the anaerobic composting of grape skins in anupflow anaerobic sludge blanket (UASB). This involved the operation of a 2.3 L laboratory-scaleUASB reactor for 205 days. The reactor successfully co-treated WWW and leachate atca. 8.5 kgCOD.m-3d-1 with a final chemical oxygen demand (COD) reduction of over 90%, a stablereactor effluent pH (7.61) and alkalinity (3 281 CaCO3 mg.L-1). This study showed the feasibilityfor the combined treatment of liquid and solid waste from the winemaking process. Although the legal limits for reactor effluent disposal onto land was not met, significant reduction in CODconcentrations were achieved, whilst producing a soil amendment that could potentially result incost savings for chemical fertilisers. The benefits related to using anaerobic bioconversion as atreatment option for liquid and solid waste could possibly be advantageous to the wine industry asan environmental control technology, by converting liquid and solid waste into valuable resources.

[发布机构] Stellenbosch University