Anaerobic bioconversion of liquid and solid wastes from the winemaking process

de Kock, Michelle (2015-02-18)

Thesis (MSc Food Sc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: South Africa is a developing country that relies on its agricultural sector as a main source of overall economic welfare. Development does not only give rise to new technology and new products but also results in increased amounts of liquid and solid waste. Generally, the production of wine is considered an environmentally friendly process, but significant amounts of natural resources and organic amendments are necessary, while generating large amounts of liquid and solid wastes. Anaerobic digestion (AD) is an attractive and proven treatment option for both liquid and solid wastes as valuable products and depollution can be obtained. AD of liquid waste results in an effluent and biogas, while anaerobic composting of solid waste results in an organic amendment, leachate and biogas. The overall objective of this study was to investigate the operational feasibility of the cotreatment of leachate produced during the anaerobic composting (AnC) of grape skins in an upflow anaerobic sludge blanket (UASB) reactor while treating winery wastewater. This first aim of this study was to investigate the efficiency of the anaerobic composting of grape skins. Laboratoryscaled digesters (1L) were utilised as anaerobic composting units. The most important operational parameters were identified (pH, moisture content and inoculum (size, ratio, composition)) in order to produce a pH stable, odour free compost in 21 days. Experimental studies highlighted the importance of shredding waste as well as the addition of calcium oxide and green waste to increase the initial pH of the composting mixture. After optimising 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 pH stabilisation and leachate generation. A 50% (m.m-1) moisture level performed the best by attaining a pH > 6.5 on day 6 and having the highest end pH (7.65) on day 21, while white and red grape skins in an equal ratio were found to generate a higher end pH. With all these optimum parameters in place (shredded waste, green waste, CaO, inoculum, moisture, grape skins), a compost with a final pH (7.09), moisture (58%), nitrogen (2.25%), phosphorous (0.22%) and potassium content (1.7%) was obtained. The optimised parameters were scaled-up (1:10) by using polyvinyl chloride anaerobic digesters (20 L) to suit the operational requirements of the AnC process and also produced a stable compost within 21 days. The second aim of this study was to investigate the combined anaerobic digestion of winery wastewater (WWW) and leachate obtained from the anaerobic composting of grape skins in an upflow anaerobic sludge blanket (UASB). This involved the operation of a 2.3 L laboratory-scale UASB reactor for 205 days. The reactor successfully co-treated WWW and leachate at ca. 8.5 kgCOD.m-3d-1 with a final chemical oxygen demand (COD) reduction of over 90%, a stable reactor effluent pH (7.61) and alkalinity (3 281 CaCO3 mg.L-1). This study showed the feasibility for 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 COD concentrations were achieved, whilst producing a soil amendment that could potentially result in cost savings for chemical fertilisers. The benefits related to using anaerobic bioconversion as a treatment option for liquid and solid waste could possibly be advantageous to the wine industry as an environmental control technology, by converting liquid and solid waste into valuable resources.

AFRIKAANSE OPSOMMING: Suid-Afrika is 'n ontwikkelende land wat staatmaak op sy landbousektor as 'n hoofbron van algehele ekonomiese welstand. Ontwikkeling gee nie net aanleiding tot nuwe tegnologie en nuwe produkte nie, maar lei ook tot die verhoogde bydrae van vloeistof sowel as vaste afval. Oor die algemeen, word die produksie van wyn beskou as 'n omgewingsvriendelike proses, maar aansienlike hoeveelhede natuurlike hulpbronne en organiese kunsbemesting word benodig, terwyl groot hoeveelhede vloeistof en vaste afval gegenereer word. Anaërobiese vertering (AV) is 'n aantreklike en bewese behandelingsopsie vir beide vloeistof en vaste afval aangesien waardevolle produkte en suiwering verkry kan word. AV van vloeistowwe lewer uitvloeisel sowel as biogas, terwyl anaërobiese kompostering van vaste afval 'n organiese kunsbemesting, loog en biogas lewer. Die oorhoofse doel van hierdie studie was om die operasionele doeltreffendheid van die mede-behandeling van loog wat gegenereer word tydens die anaërobiese kompostering (AnK) van druiwe doppe in 'n opvloei-anaërobiese-slykkombers (OAS) reaktor terwyl kelderafvalwater behandel word, te ondersoek. Die eerste mikpunt van hierdie studie was om die doeltreffendheid van die anaërobiese komposteringsproses van druiwe doppe te ondersoek. Laboratorium-skaal verteerders (1L) is gebruik as anaërobiese komposteringseenhede. Die belangrikste operasionele parameters is geïdentifiseer (pH, voginhoud en inokulum (grootte, verhouding, samestelling)) om ‘n 'n pH-stabiele, reukvrye kompos te produseer in 21 dae. Die belangrikheid van gesnipperde afval asook die byvoeging van kalsiumoksied en groen afval om die aanvanklike pH van die komposmengsel te verhoog, is deur eksperimentele studies beklemtoom. Na die optimering van 'n 50% (m.m-1) koeimis inokulum, is laer inokulum konsentrasies (10, 15 en 25% (m.m-1)) geondersoek om die proses meer ekonomies uitvoerbaar te maak. Daar is gevind dat ‘n 10% (m.m-1) anaërobiese kompos (AK) inokulum die mees gunstige resultate lewer in terme van pH stabilisering en loog generering. ‘n 50% (m.m-1) vloeistof vlak het die beste presteer deur 'n pH> 6.5 te bereik teen Dag 6 asook die hoogste eind pH (7.65) teen Dag 21, terwyl wit en rooi druiwe doppe in dieselfde verhouding gevind is om ‘n hoër eind pH te genereer. Met al hierdie optimum parameters in plek (gesnipperde afval, groen afval, kalsiumoksied, inokulum, vog, druiwe doppe) is 'n kompos met 'n finale pH (7.09), vog (58%), stikstof (2.25%), fosfor (0.22%) en kalium inhoud (1.7%) verkry. Die optimale parameters is opgeskaal (1:10) deur gebruik te maak van polivinielchloried anaërobiese verteerders (20 L) om aan die operasionele vereistes van die AnK proses te voldoen en ook om 'n stabiele kompos binne 21 dae te produseer. Die tweede mikpunt van hierdie studie was om die gekombineerde anaërobiese vertering van kelderafvalwater en loog, verkry vanaf die anaërobiese kompos van druiwe doppe in 'n OAS reaktor, te ondersoek. Dit het die bedryf van 'n 2.3 L laboratorium-skaal OAS reaktor vir 205 dae ingesluit. Die reaktor het kelderafwater en loog suksesvol behandel by ongeveer 8.5 kgCSV.m-3d-1 met 'n finale chemiese suurstof vereiste (CSV) vermindering van meer as 90%, 'n stabiele reaktor uitvloeisel pH (7.61) en alkaliniteit (3 281 CaCO3mg.L-1). Hierdie studie het die uitvoerbaarheid van die gekombineerde behandeling van vloeistof en vaste afval van die wynmaakproses getoon. Alhoewel die wetlike vereistes van die reaktor uitvloeisel vir storting op grond nie bereik is nie, is ‘n beduidende vermindering in CSV konsentrasies bereik, asook die vervaardiging van kunsbemesting wat die potensiële aankoopkoste van chemiese kunsmis kan verminder. Die voordele verbonde aan die gebruik van anaërobiese bio-omskakeling as 'n behandelingsopsie vir vloeistof en vaste afval kan moontlik voordelig wees vir die wynbedryf as 'n omgewingsbeheerende tegnologie deur om vloeistof en vaste afval om te skakel na waardevolle bronne.

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