How to get rid of industrial waste: feed it to bacteria

A spin-out company is pioneering the use of bacteria that literally eat the toxic by-products of high-tech engineering.

Microbial Solutions Ltd has developed a clever solution to the disposal of ultra-high toxicity fluids, a serious issue for high-tech metal working companies such as those that manufacture aircraft and cars. Extremely precise engineering is required to create something like an aeroplane’s wing or a modern fuel efficient engine, and the interface between the metal and the machine cutting it has to be constantly lubricated with a carefully emulsified mixture of high-grade oils and water. The fluid carries away metal swarf, facilitates the most accurate cut possible, and absorbs heat which could otherwise damage the product and the tool.

There is a problem, however: bacteria love these oil and water mixtures. They are warm and full of hydrocarbons which the bacteria feed on, providing a perfect breeding ground. Under normal working conditions the fluids can rapidly become so contaminated with bacteria that they have to be replaced. This is expensive, and therefore the lubricating fluids contain biocides to make them as toxic as possible, resulting in fluids that last much longer, give better machining performance and save companies money.

In the long run, though, even these fluids become unusable, and this creates another problem: a highly toxic waste product that has to be disposed of. Expensive and energy-intensive chemical methods can be used to break up the fluids, but these will not remove all the toxic components. The poisonous sludge left behind also has to be disposed of – incinerated, or in some parts of the world buried in landfill, where it will slowly break down anaerobically, but at the cost of releasing the greenhouse gases methane and CO2 into the atmosphere. The disposal process can cost companies hundreds of thousands of pounds a year.

It was research by Chris van der Gast, a DPhil student affiliated to the Department of Engineering Science and working at the NERC Centre for Ecology and Hydrology (CEH), which began to address this problem. In conjunction with Professor Ian Thompson (then at the CEH, but now at Oxford University), Chris investigated whether bacteria could be employed to deal with the poisonous waste. It seems counterintuitive to use bacteria to consume something that has deliberately been treated with biocides, but in fact almost anything can be eaten by bacteria – it is just a question of finding the right ones.

After a careful worldwide search of the hundreds of bacteria that survive naturally in metal working fluids, five were selected, and this mix of bacteria was able to create a self-sustaining system. At ambient temperature and pressure, with no need for high energy inputs, the bacteria gradually consume the toxic fluids (including the waste oil), producing small amounts of carbon dioxide. Toxicity, carbon and nutrient balancing keeps bacterial growth at a stable level and prevents algal bloom. The grey water left over at the end of the process can be recycled or released directly into the sewers, and the system has proved capable of running for years at a time without the need to add more bacteria.

The research led to the spin-out of Microbial Solutions in 2008. Industry was quick to see the potential of the company’s patented MicrocycleTM bacterial treatment, since it helped them to meet increasingly stringent targets for reduction of pollution, landfill waste and greenhouse gas emissions, as well as saving them considerable amounts of money. The technology has been trialled by British Aerospace and the Ford Motor Company, with highly successful results; Microbial Solutions has won Technology Awards from both companies, as well as a UK Award for Environmental Excellence, and the future of its innovative bioreactors looks extremely promising. Meanwhile, further research into the innovative uses of bacteria in environmental engineering is continuing in the Department of Engineering Science.

Peter Fish, Systems Estates Manager for British Aerospace, said: ‘Microbial Solutions reactor solves a number of problems at once: it can save costs and also helps us meet our environmental obligations. We have a site of special scientific interest near our Brough plant, and we have to be very careful when transporting, treating, or disposing of waste. Being able to remove the toxins from metal working fluids so effectively is a huge benefit. We’re very pleased the trial has worked so well and look forward to continuing our excellent working relationship with the Microbial Solutions team.’

Original research funded by the Natural Environment Research Council

Visit the Microbial Solutions website

This is one of the Oxford University research impact case studies