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The wastewater from a food processing factory, characterised by fluctuations of flow rate, organic strength, and pH, were originally treated by a traditional suspended-biomass digester working at about 25°C. In order to improve the digester efficiency, either in terms of degradation ability or biogas production yield, a set of tests has been carried out on laboratory scale, whose results indicated the way to correctly transform it into an anaerobic hybrid filter. The unacceptable conversion yield of organic substances into biogas observed in the original system has been improved by the presence of the filling medium, due to a marked increase in biomass retention time.The start-up of anaerobic digestion has been studied in this reactor at two different temperatures (25 and 30°C), in order to evaluate the possible advantage of heating the system, simulating continuous variations in feed strength, pH, and composition. IntroductionWastewaters from food processing plants can effectively be treated by anaerobic digestion because of the favourable characteristics of these effluents, such as their content in organic substances, relatively high temperature [1], and good biodegradability [2]. In fact, due to this last peculiarity, their digestion does not require any hydrolytic pre-treatment like that proposed for entirely hemicellulosic or lignocellulosic wastes [3,4], hardly ever the exocellular hydrolysis being the limiting step of the process. Further reasons of the increased interest towards anaerobic digestion of these residues, with respect to traditional aerobic processes, are the formation of valuable products [5] as well as the savings of the high costs of energy to run aerobic alternative process [1].At the moment, most of the organic effluents and wastes coming from industrial, municipal or agricultural activities are treated favourably by anaerobic digestion [6].The traditional suspended-biomass digester, that is in general the optimal solution for the treatment of wastewater with relatively high suspended solids and organic content, working at an average hydraulic residence time of only 72 hours, does not allow the development and the retention of a stable population of low growth rate methanogenic bacteria. So, it is necessary to change the digester configuration, in order to promote the micro-organism retention time and to make it independent of the hydraulic residence time.Among the alternative solutions that have been proposed to this purpose, the fluidised bed reactor is certainly the most attractive, but, at the same time, it is still quite complex for full scale industrial applications. Food processing wastes with high organic content were successfully digested in a fluidised bed reactor jointly with wastewater coming from the washing operations of wine industry [7]. A methane production yield ranging from 98.6 to 85.0% of the maximum theoretical value was in satisfactory agreement with the results obtained by Boening and Larsen for whey [8].A simpler solution is provided by the anaerobic hybrid filter...

The aim of this study was to assess the potential of utilizing Lactobacillus delbrüeckii spp. bulgaricus in order to improve the characteristics of dairy wastewater and produce biomethane. Nuclear magnetic resonance was utilized to assess the metabolites present in the unprocessed wastewater. It was determined that wastewater is a good source of important bio-refinery relevant compounds and therefore wastewater has a potential to be utilized during fermentation as nutrients source. Upon wastewater fermentation, the chemical oxygen demand and biological oxygen demand significantly decreased (respectively 97.0 and 97.8%). Protocols were tested for one- and two-stage fermentation. During the one-stage fermentation, lactic acid bacteria were not added to the wastewater. During the two-stage fermentation, acetogenesis and methanogenesis occurred separately with the addition of L. delbdueckii during the acetogenesis stage. The highest yield of methane was obtained from wastewater upon two-stage fermentation (76% two-stages compared to 38% one-stage). Therefore, L. delbrüeckii have the potential to be utilized to ferment dairy WWs and produce methane. Such treatment of wastewater not only produces methane, but also decreases the polluting effect of the waste streams, by reducing the chemical oxygen demand and biological oxygen demand to 0.199 and 0.031 g/l, respectively

Olive oil extraction is one of the ancient agricultural industries all over the Mediterranean area and even today it is of fundamental economic importance for many industries found over the whole Mediterranean. However, this industry generates large amounts of olive mill wastewater (OMW) and due to its physicochemical characteristics it causes severe environmental concerns and management problems in the Mediterranean area, which is facing water scarcity. Technologies to reuse this wastewater will have a high impact at the economic and environmental level. The work presented aims to improve the use of jet-loop reactors technology for the aerobic biotreatment of OMW. A jet-loop reactor (100 L) coupled with an ultrafiltration (UF) membrane (MBR) system (JACTO.MBR_100 L) were tested for the influence of hydraulic parameters on OMW degradation and scale-up to 1,000 L. Chemical oxygen demand and total phenols (TP) decreased notably (up to 85% and 80% removal efficiency, respectively) after the biological treatment. The treated OMW (UF permeate) was evaluated as a source for irrigation and its impact on the soil and plant growth and their quality parameters.