Case study: Membrane technology allows water recovery and savings at beetroot processing site

Transcription

1 Case study: Membrane technology allows water recovery and savings at beetroot processing site

2 WRAP s vision is a world where resources are used sustainably. We work with businesses, individuals and communities to help them reap the benefits of reducing waste, developing sustainable products and using resources in an efficient way. Find out more at Adapted from Envirowise Publication CS855, published 2009 While we have tried to make sure this guide is accurate, we cannot accept responsibility or be held legally responsible for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. This material is copyrighted. You can copy it free of charge as long as the material is accurate and not used in a misleading context. You must identify the source of the material and acknowledge our copyright. You must not use material to endorse or suggest we have endorsed a commercial product or service. For more details please see our terms and conditions on our website at 2

3 Background This Case Study at G s Fresh Beetroot demonstrates the cost savings and environmental benefits that can be achieved when implementing environmental initiatives to reduce water use and effluent strength. It also demonstrates the added cost benefit through Enhanced Capital Allowance available from the Water Technology List. The company has used membrane technology to successfully treat its effluent, producing a water of sufficient quality for re-use on site. The benefits to G s of taking action to minimise water use and waste include: Total cost savings of 152,000/year Annual water consumption reduced by 22,400 m 3 Water-related cost savings of 16,000/year Effluent-related cost savings of 126,000/year About G s Fresh Beetroot G s Fresh Beetroot is part of the G s Marketing group, a family business that was founded in 1952 by Guy Shropshire, the current President, and is now run by his eldest son, John Shropshire. G s supplies many UK food businesses including a number of the leading quality supermarkets for whom G s supplies a range of own-label salads and vegetables. For more than 40 years G s has also supplied the independent retail, food service & catering, and food manufacturing sectors under the G s trademark. G s Fresh Beetroot employs some 120 staff at its 3.5-acre site in March, Cambridgeshire, and produces around 12,000 tonnes of beetroot a year. The site opened in 2001 and currently produces around 12,000 tonnes of beetroot a year. The company supplies a number of the leading quality supermarkets as well as independent retail, food service & catering, and food manufacturing sectors. With the cost of effluent disposal increasing every year, the site sought advice from its water provider and discussed ways to reduce effluent volume and load, allowing G s to ensure compliance and reduce disposal costs. Review of effluent costs and treatment Prior to 2007, G s treated its effluent using an aerobic digester. By July 2005 the site s effluent costs, based on the Mogden formula, had risen to around 5.40/m 3 with annual costs of around 141,750. With the site s processing capacity expected to increase along with the annual increase in trade effluent charges, G s estimated that effluent costs would be over 160,000 the following year. Initial investigations found that the clarifier was providing poor retention and therefore inadequate solids removal. A cone was inserted into the clarifier to create a vortex, providing better retention. Furthermore, after discussing the options with the site s mains water provider, Anglian Water, G s decided to look at using membrane technology to further improve effluent

4 treatment and reduce costs. G s teamed up with Aquabio to trial a membrane filtration system that was designed to treat all effluent generated on site (typically m 3 /day), allowing up to 70% recovery for re-use. The benefits of membrane technology When used for wastewater treatment, membrane filtration processes offer a high level of purification, allowing the wastewater to be recovered and re-used. Moreover, the technology offers a low footprint and has relatively low energy consumption. Initially G s undertook a three-month pilot study to ensure that the effluent could be adequately treated using the proposed membrane technology. The pilot effluent treatment plant consisted of a membrane bioreactor (MBR) comprising an aerobic bioreactor and ultrafiltration (UF) followed by reverse osmosis (RO). Fig 1 shows the effluent at different stages of treatment. The coarse solids are removed from the effluent before it is pumped into the bioreactor (A) where the majority of the chemical oxygen demand (COD) is removed. The effluent is then treated by ultrafiltration to remove the biomass (B). The UF treated effluent (UF permeate) is then polished by reverse osmosis, removing the residual colour (C). Overall this treatment removes >99% COD and suspended solids loads. The pilot proved successful in recovering 70% water (permeate) for re-use, with the remaining 30% (retentate) being discharged to drain. In addition, the quality of the recovered water was such that it can be used for boiler make-up without pretreatment. Previously the boiler make-up comprised mains water that had to be softened prior to use. Fig 1 Effluent at different stages of treatment Since the success of the pilot, the site has commissioned a full-scale MBR achieving the following high performance: Table 1 MBR performance COMPONENT COD AVERAGE Bioreactor feed 8, UF permeate UNITS mg/l kg/day mg/l kg/day Every day samples are analysed on-site for a number of parameters including COD. Data are entered into the monitoring spreadsheet to track performance and ensure quality standards are met. Enhanced Capital Allowance (ECA) The Enhanced Capital Allowance (ECA) scheme enables businesses to claim 100% firstyear capital allowances in investment in efficient membrane filtration systems for the treatment of wastewater for recovery and re-use. G s has become the first company to gain ECA approval for tax relief, worth more than 100,000, for the capital costs of an efficient membrane filtration system. 2

5 The company was awarded a Certificate of Environmental Benefit from Defra that demonstrates that the installation is water efficient and allows G s to claim ECAs on the costs of the investment. ECA for the G s membrane bioreactor has shortened the payback period of the project by 12 months, which gave senior management the confidence to invest. Further information and advice on ECA can be found at Cost savings Installing and running the MBR is a high cost. However, with savings of around 152,000/year, the initiative has a payback period of 2.6 years, taking into account the benefits realised with ECA (see Table 2). Given that the site s processing capacity is expected to increase, the effluent load will almost certainly increase and as such savings are likely to exceed those reported in Table 2. Table 2 Summary of costs and savings ITEM SAVINGS ( /YEAR) COSTS ( /YEAR) Water 16,000 - Effluent 126,000 - Solid waste (screenings) 10,000 - Sludge disposal - - Other running costs - 52,650 Capital investment - 500,000 PAYBACK PERIOD Total 152, , years With ECA benefit 2.6 years Environmental benefits The use of the MBR has resulted in the following environmental benefits: A reduction in mains water use of 70% (22,400 m 3 /year). Reduced effluent strength by 726 kg/day COD and 138 kg/day suspended solids. Ensured compliance with the trade effluent consent. 3

6 Fig 2 Schematic of membrane bioreactor (MBR) ECA eligibility has really made the difference. It has provided us with a major incentive to invest. Not only will we be able to significantly reduce our water and effluent costs, but the ECA has also shortened the payback period of the project by 12 months, giving the board the confidence to invest. Graham Forber, Managing Director, G s Fresh Beetroot 4