Aerobic treatment of winery wastewater using a jet-loop activated sludge reactor
Introduction
As in any other food-processing industry, wine-making operations lead to the production of wastewater that, due to its specific composition and high organic load, represents a serious environmental problem in all wine-producing countries, France and Italy in particular [1], [2].
Winery wastewater (WW), that mainly comes from the washing waters of equipment and bottles and from the cooling processes, is generally non-toxic and non-hazardous [3]. Over the year, however, volumes and pollution loads greatly vary in relation to the working period (vintage, racking, bottling) and to the winemaking technologies used (e.g. in the production of red, white and special wines) [1]. Hence, WW should not be directly conveyed to municipal wastewater treatment plants without previous suitable treatment.
The optimization of water management within the winery requires a consistent reduction of the waste volumes [4], [5]. The development of unconventional biotreatments, either aerobic or anaerobic, such as those using UASB reactors [6] and rotating biological contactors [7] appears to be the only possible strategy to solve the problems related to WW disposal. So far, however, aerobic column reactors characterized by high oxygen transfer efficiencies have not been used in WW treatment.
Jet loop reactors (JLR), the efficiency of which has already been shown in both chemical and biological processes [8], [9], might represent an ideal reactor typology for an economic solution to WW disposal. The jet of liquid from the nozzle produces high mixing and turbulence that guarantees optimal mass transfer and good biological conversion. Moreover, JLRs are generally characterized by reduced volumes, which means limited area requirements, reduced costs of installation and maintenance and limited energy consumption [10].
The aim of this work was to assess the technical feasibility of using a JLR in the aerobic treatment of WW by setting-up process conditions including the adaptability of the system to sudden variations in organic load. Finally, the microbial population developed in either the mixed liquor or the microbial layer formed by adhesion on the inner surface of the reactor was characterized.
Section snippets
Winery wastewater (WW)
WW was obtained from three different wineries, Lungarotti (Torgiano, Perugia, Italy), Coop Vitivinicola of Orvieto (Orvieto, Terni, Italy) and Cantina Cooperativa dei Colli Umbri (Marsciano, Perugia, Italy), and, after adjustment of the pH to 7.5, used as such with no addition of either phosphorus or nitrogen. Analytical characterization of WW is presented in Table 1. Every month, approximately 0.08–0.1 m3 of WW was collected from the wineries; COD values were highest during vintage and
Results and discussion
Compared to other traditional aerobic systems (e.g. activated sludge plant), jet loop reactors (JLR) usually show advantages such as, the absence of mechanical devices for aeration (e.g. blower, impellers, turbines, etc.). A simple centrifuge pump guarantees high-speed passage of the liquid through a nozzle and, as a consequence, large amounts of external air are inhaled through the air inlet of the venturi ejector [13]. Moreover, the inhaled air is micronized, highly increasing the diffusion
Conclusion
The aerobic treatment of winery wastewater using jet-loop reactors is technically feasible and appears to be promising. However, settleability, although often within the acceptability limits, should be improved by the use, for instance, of more efficient settling systems. To this end, scaling up studies of the process at the pilot plant level are in progress at the Co-operative Winery of Dois Portos, Portugal, using a JLR (2.0 m3, working volume) equipped with a new settling tank.
Acknowledgements
Research work supported by the European Commission, DG Environment, within the Program LIFE (Project 96ENV/P/00602/INDW).
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