The development of an audit procedure and treatment technologies for Rupert and Rothschild vignerons' winery wastewater

[摘要] ENGLISH ABSTRACT: Ecosystems and natural water sources are constantly under threat frompollutants and all efforts should be made to minimise polluting factors. In thelast decade growing concern has been expressed with regard to theenvironmental threat posed by wastewater produced by wineries anddistilleries. Research into winery wastewater commenced in the early ninetiesmainly in Australia and France. These investigations characterised winerywastewater, indicating a large diversity in quality and quantity betweenwastewaters emanating from wineries. Owed to changes in South Africanlegislation, in conjunction with an augmented environmental awareness, theneed for an environmental assessment of wineries became apparent. InSouth Africa, research of this nature had not yet been conducted. Previousresearch on winery wastewater treatment employed mostly biologicaltechnologies, with success but also shortfalls.In South Africa the majority of wineries are located in the Western CapeProvince, several within the same water catchment area. Wineries mayproduce approximately 1 to 10 litres of wastewater per litre of wine produced,which are turbid and acidic and typically contain high levels of organiccompounds (thus oxygen deficient), and suspended material. Usually thesewastewaters are irrigated onto land, in close proximity to natural waterresources. The pollution of water tables and down-stream water sources mayoccur. The quantification, qualification and treatment of this type ofwastewater are addressed in this study.Winery wastewater produced from the predominantly red wine producingRupert and Rothschild Vignerons, served as case study for a two-yearwastewater audit strategy. The most common analyses performed on winerywastewater include the Chemical Oxygen Demand (COD), suspended solids(SS), pH and turbidity. A thorough analysis in the form of a comprehensiveaudit was performed on the water and vinification processes. This allowed foran accurate determination of contamination sources and properties. The auditentailed a designed sampling protocol, the format of which was tailored as aninitial environmental assessment for the development of an EnvironmentalManagement System (EMS) unique to Rupert and Rothschild Vignerons. TheEMS includes projected future objectives for wastewater quality (COD, SS,pH, turbidity), as well as an environmental policy. In order to reach theproposed quality objectives, a suitable wastewater treatment system must beinstalled.The efficiency of the treatment system present at Rupert and RothschildVignerons was evaluated and piloted the investigation of physico-chemicaltreatment technologies. Research into the applicability of inducedsedimentation (coagulation) and chemical oxidation (ozone) was the first ofits kind for winery wastewater as substrate, and provided an interestingdimension in the sense of pragmatic and economic feasibility.Dissolved and suspended particles present in winery wastewater do not settleby gravity alone, thus requiring sedimentation agents (coagulants). Benchscaleexperiments were conducted employing four types of pre-polymerisedmetal salt coagulants (polyaluminium chloride). Successful sedimentation ofturbidity inducing compounds (up to 98 %) and suspended solid fractions (upto 92%) was achieved. These coagulants are highly suitable for the treatmentof winery wastewater since the investigation showed that they are effectiveover a broad pH and dosage range. In addition, rapid sedimentation rateswere observed, favouring thickener design economy.Ozone is a potent oxidising agent, and has been reported to increase thebiodegradability of dissolved organic compounds and result in the decolouringof wastewaters. Ozonation is highly pH dependent, with hydroxyl radicalactivity dominating at alkaline pH. In the majority of gas-liquid contactingsystems, the kinetics of the heterogeneous reaction is not limited by thechemical reaction rate, but by the transport of ozone to the liquid phase. Tocompensate, the ozone concentration in the gas phase is increased. Coupledto the primary investigation on the applicability of ozone treatment for winerywastewater, thus emerged a secondary investigation into an enhanced masstransfer system, realised by the use of impinging stream technology. Theozone transfer in a conventional bubble-column was compared to that of animpinging-stream jet-reactor. The latter significantly improved the ozonetransfer to the winery wastewater, resulting in the rate-limiting step being thechemical reaction rate. Ozonation resulted in the increased biodegradabilityof the winery wastewater, and complete colour and odour elimination.Concerning jet-reactors, the principal importance lies in the substantialreduction in the initial ozone concentration requirement, thereby rendering theprocess more economically feasible.Following the investigation of the wastewater dynamics, the determination ofeco-toxicology during irrigation should be conducted in future. Whenconsidering induced sedimentation, further studies should be directed towardsascertaining the most economic yet efficient dosage of the coagulant.Similarly, a study concerning the economic viability of ozone efficiency shouldbe realised in terms of the energy requirements for both ozone generation andthe operation of jet-reactors. Although the jet reactor poses a benefit forenhanced mass transfer, the essential criterion concerning residence time inthe reactor must be addressed for positive results.Since no single solution exists for the treatment of winery wastewaters, theapplication of the considered technology must be carefully selected andincorporated in a treatment design; the two foremost criteria for selectionbeing efficiency and economy.

[发布机构] Stellenbosch University