PROJECT DESCRIPTION
BACKGROUND
The wine production industry generates almost as much liquid effluent as wine. The amount depends on the year, the type and the process of wine production, combined with the system of water and effluent management within the company. Although it is obligatory to treat effluents, wine production raises specific problems due to its composition, high organic load, seasonal variations of flow and COD (chemical oxygen demand) charges and composition. This represents a serious challenge to all the European countries with extensive wine production e.g. France, Spain, Italy or Portugal. The wastewater from wine is generally non-toxic and non-hazardous, as it comes primarily from washing bottles and other equipment, and from the cooling process. But a problem arises with the variability of the volumes and pollution loads in different stages of the wine production process (vintage, racking, bottling) and to the winemaking technologies used. The COD charges produced vary, on average, from more than 15 Kg/m3 during the harvesting period to less than 1 Kg/m3 during the later racking and bottling operations. In general, the waster water from the wine production should not be sent directly to the municipal wastewater treatment plants without a previous suitable treatment. The optimization of water management within the winery requires a consistent reduction of waste volumes. The development of unconventional biotreatments appear to be the only possible strategy to solve the problems of winery wastewater (WW) disposal. So far, however, aerobic columns reactors characterized by high oxygen transfer efficiencies have not been used in WW treatment. Jet loop reactors (JLR), the efficiency of which has been shown in both chemical and biological processes, appear to represent the ideal reactor for an economically viable solution. The jet of liquid from the nozzle produces high mixing and turbulence that guarantees optimal mass transfer and good biological conversion. Moreover they are generally characterized by reduced volumes, therefore needing limited space requirements, involving reduced costs in installation, maintenance and energy consumption.
OBJECTIVES
The purpose of the project was to assess the technical feasibility of using a JLR in the aerobic treatment of Winery Wastewater (WW) carrying out laboratory tests to demonstrate the necessary process conditions, including the adaptability of the system to sudden variations in organic load.The project would be developed jointly between the seven Portuguese and the Italian partners. Winery waste water would be obtained from Italian wineries and fed into the JLR, specially built in the Department of Biotechnology in INETI. The reactor would consist of a cylindrical aerated bubble type column with a central tube and a cylindrical degassing tank. This would function on the principle of venturi-aspiration of air. The mixed liquor would be pumped through a nozzle orifice where the air would be drawn into the liquid through an air tube. This aerated mixed liquor would pass from the column reactor to the degassing tank where it would be recycled again into the column reactor. The degassing tank would be connected to a settling tank where the displaced mixed liquor would be collected. In this way the effluents to be treated would be continuously recycled through the reactor. Stainless steel would be used to guarantee good mechanical and corrosion resistance and virtual zero maintenance. It would have a cylindrical configuration to facilitate construction with a flat bottom and an open top. The expected outcome was a treatment efficiency of 97-98% of the entry volume. The results obtained in the laboratory would enable an EDAR prototype to be constructed.
RESULTS
The project demonstrated that the aerobic treatment of winery wastewater using jet-loop reactors is technically feasible and economically viable. The JACTO reactor system represented a singular example of the importance of taking into account the interaction between process-design-effluent in this area of agro-industrial effluents. The reactor system proved able to produce high oxygenation of the wineries effluent and generated a microbiologically unique composition highly adapted to this treatment technology. The overall efficiency was good and in most cases higher than those obtained with more technologically advanced solutions, even though the reactor is a relatively simple piece of equipment, easy to control, operate and maintain. Conversions of around 30 Kg/m3/day are a good indicator of its productivity with COD abatement yields at these high loads, in the order of 80-90%. This represents a high volumetric to productivity ratio, with concomitant reduced reactor volumes, particularly when consideration is taken of the lack of mechanical agitation and the effectiveness of the liquid to total volume occupation. Another important consideration, was the waste biomass produced in the process. Here the JLR reactor showed unique performing characteristics that merit further study. Instead of increasing with the increasing load rate and processing time, the amount of MLSS (Mixed Liquor Suspended Solids) were controlled depending on the desired productivity, giving values lower than 1.0kg/m3. The possibility of operating at a high F/M ratio is extremely important as it means low amounts of waste sludge are produced. However, settleability, although often within the acceptability limits was shown to need improvement by the use of more efficient settling systems. To this end, scaling up studies would be necessary, equipped with a new settling tank. The project also demonstrated the need for optimal water management practices within the winery so as to reduce the volume of effluent and to ensure the segregation of effluents where possible e.g. from cleaning and refrigeration operations. The system showed itself not to be affected by seasonal variations and to have a high buffering capacity in terms of chemical composition, COD load, pH and even temperature. Moreover, no need for inorganic supplements was demonstrated suggesting some auto-regulatory mechanism of nutrients supply unrelated to the efficiency of the organic pollution degradation. The vertical design of the reactor represented a further advantage in terms of availability of land and site requirements. Furthermore, when the smaller installation and maintenance costs are taken into account together with the reduced energy consumption, the reactor appears to offer a competitive solution and represent a benefit for the wine industry and for the environment.
