Water and Effluent Treatment Magazine
Issue link: https://read.utilityweek.co.uk/i/867569
18 WET NEWS SEPTEMBER 2017 This approach is now being used in some UK factories including distilleries and dairies. The biogas generated can provide on-site energy for the production of ready meals, cheese or even beer, or, as biomethane, to fuel the HGVs that distribute products from factory to retailer. A growing concern for the resource-hungry food industry is the volume of potable water used throughout the food chain, from farms to manufacturing sites, not only in production processes but also for factory hygiene and bio-security. Also, a challenge for food importing regions such as the EU, that already depend on access to external water resources, is whether individual countries and business sectors can reduce their position as net 'virtual' water importers. With global water demand for production of food, fibre and energy crops increasing, the agri-food sector must become more efficient to supply products in a more water- sustainable way. Food processors can do this not just with measures like rainwater harvesting but also by reducing water use and losses in the manufacturing and supply chain. Bio-digestion can allow cleansed water to be reused within the factory, as well as re-charging watercourses. With cost-effective chemical oxygen demand (COD) removal from process residues and washwaters, costs of cleaning up grey water can be reduced. Some of the AD plants Clearfleau has built discharge to sensitive water courses. On such sites, grey water could also be recycled for non-food contact use. Increasingly we expect this to be a key part of future on-site bio-energy projects. Generating clean energy from process residues is one way of promoting better water management in the food sector, and should be part of the government's long-awaited clean growth strategy, due to be announced in the Autumn. With national agencies, such as the Environment Agency (EA), promoting a more circular approach to resource use, to curb carbon emissions and improve use of raw materials, water use will become part of the equation. In future, they may penalise factory sites that are more profligate or fail to take measures to cut energy use, reduce emissions or conserve water. Cleansed water is one of the three outputs from the on-site digestion process, with biogas and bio-solids. Bio-solids can provide nutrients to help grow barley or vegetables (or the grass to produce milk), raw materials for production processes. Two current projects illustrate how the food and drink industry could combine its investment in bio-energy with on-site water re-use. We are about to commission a digestion plant on a vegetable processing operation close to East Anglia, one of country's most water challenged regions. Current regulations, despite surprising EA concerns over the impact on the flood plain, in a region with a low rainfall, allow the factory to discharge the cleansed water into the local watercourse. Grey water re-use is an option. The EA and other stakeholders should encourage sites in water-scarce areas to use recycled process water to wash their vegetables or for the irrigation of crops grown nearby. Another project in Scotland, in the drinks sector, will replicate the approach of several distilleries, where a"er digestion cleansed water is being discharged into the River Spey. Here we are undertaking a feasibility study to explore whether cleansed water a"er AD can be further polished, using reverse osmosis, to allow it to be re-used on the site in process applications – reducing the proportion of water to be extracted from nearby aquifers. This will be a major innovation for the drinks sector, with a significant impact on the site's water footprint. Projects like these two will show that grey water re-use is a viable proposition, as Britain's food and drink industry seeks to improve its environmental impact by extracting energy from liquid processing residues. Future on-site digestion projects will not only supply bio-energy but also produce clean water for factory use. Recycling of cleansed water, to enable production sites to reduce net water consumption, should be part of the government's clean growth strategy. Richard Gueterbock is director at Clearfleau. 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