Aquabio gets to the root of a particularly potent problem
Aquabio is pioneering the use of large-scale recycling and reuse systems in the industrial sector.In 2007, the Worcester-based supplier took on a project at a salad and vegetable processing plant in Cambridgeshire.
G's Beetroot found that expansion of its factory, due to a rise in the demand for beetroot, meant its water and effluent treatment costs were rising.
Aquabio first did a three-month pilot study to evaluate the process before the system was scaled up. Due to the use of large amounts of vinegar in the upstream process, and the washing, cutting and cooking of the beetroot, the raw wastewater is extremely strong, with chemical oxygen demand (COD) of between 5,000mg/l and 20,000mg/l - 15 to 70 times stronger than domestic sewage.
The plant is designed to treat 130m3/d of raw wastewater and produce a potable water volume of up to 90m3/d for reuse back in factory processes and boilers. Most of the recycled water from the plant is returned back to the factory mains water tank, where it is monitored for conductivity, and topped up with water from Anglian Water's municipal supply.
The production cost of the recycled water is 25% of the cost of the main supply into the factory. A proportion is pH corrected and reused directly from the reverse-osmosis (RO) unit as demineralised boiler-feed water.
This also saves on heat and softening/antiscalent chemicals, as well as significantly reducing boiler blowdown frequency, which saves even more water.
Aquabio says its AMBR is an aerobic wastewater treatment solution, which combines jet aeration with membrane bioreactor technology.
The company says it has a number of specific advantages:
- It is very compact with a small carbon footprint, compared with other membrane bioreactors, saving both space and cost
- The cost of the membranes is significantly lower than other MBRs. Modular standardisation of the system gives the user a choice of membrane suppliers
- It has reliable and high-flux performance, and permits out-of-tank operation and maintenance of the membrane separation system, giving clean, fully automated and safe operation
- Membrane cleaning frequency is low, about once every three to four months
- Construction at G's Beetroot is modular and containerised, making it ideal for expansion at a later date
- High molecular cut-off (0.04µm) membranes are used to optimise good hydraulic performance with high-quality treated water. This is particularly important when feeding onto the tertiary RO system, reducing long-term membrane fouling
The product water is reliable, safe, and of a higher standard, and more uniform consistency, than potable water available from the mains.
Water recycling and reuse in internal loops and end of pipe is becoming an important means of meeting stringent Environment Agency Integrated Pollution Prevention Control requirements. The reuse of water to process, and softened recycled water to boilers, for more efficient energy generation, is particularly beneficial.
The project was the first to be awarded an eligibility certificate under the government's enhanced capital allowance (ECA) scheme for efficient membrane systems. G's Beetroot was able to obtain a 100% tax allowance in the first year on all of the capital cost of the project.
The Aquabio system has exceeded the ECA target for reuse, with up to 70% of the wastewater produced being reused as potable-quality water in the factory and soft water to the boilers.
Since the project at G's, a further certificate has also been granted to a combined anaerobic/AMBR/RO Aquabio plant at Unilever Marmite. Several other projects are now in the application stage under the scheme.
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