Hungry microbes are being used in a pilot project to clean up waste water coming from meat plants. An NUI Galway research team believes its system will produce an effluent clean enough to discharge directly into a river or stream.
Funding for the work by Dr Xinmin Zhan and Dr Mark Healy of Galway's department of civil engineering comes from the Environmental Protection Agency (EPA) via its new Environmental Technologies Programme.
The EU Environment Commissioner, Stavros Dimas, joined the Minister for the Environment, Heritage and Local Government, Dick Roche, last week to launch the new programme.
The EPA announced funding worth almost €2 million for 15 separate research projects in universities and in private sector companies. Money for the environmental technologies scheme comes from the plastic bag and landfill levies brought in to help protect and improve the environment.
Zhan and Healy's project was one of the inaugural 15 studies to be funded under the new programme. Its goal is to clean up the waste water coming from meat production plants, explains Zhan, who is principal investigator for the project.
He and colleagues had proposed the project to the EPA, he says. Their success was based on the university's long track record on the use of bacterial "biofilm reactors" as a way to clean up pollution.
"The department of civil engineering had done a lot of processing work on biofilm technology," says Healy. "This was an area where we had a huge amount of experience."
Zhan and his collaborators devised a four-step batch-processing system to handle the complex mix of substances found in the liquid waste stream coming from slaughterhouses. The waste includes organic solids and also phosphorus, nitrogen and ammonia, hence the multipart process.
The process has several steps because it switches between aerobic and anaerobic bacterial digestion, Zhan explains.
"Some organisms are responsible for organic pollutant removal and others for ammonia removal and nitrate removal," he says.
The EPA-funded project description specifically highlights nitrogen removal from the waste stream, using a process of simultaneous nitrification and denitrification to clear the pollutants. However, the process is designed to clear the waste stream of all solids and contaminants, adds Zhan. Early work on the process suggests it will prove effective at scrubbing up the waste water.
"We have found the quality of the effluent is very good," Zhan says, certainly good enough to run directly into water courses. It can remove 75 per cent to 85 per cent of the nitrogen. "The total nitrogen will be removed from the system."
Supporting bacteria grown in a digester can be handled in a number of ways depending on the process. This includes suspending the bacteria in the solution or growing films of bacteria on polyethelene substrates, says Healy.
For this project, a "mixed media biofilm" is being used, with the bacteria carried on particles suspended in the digester.
The EPA is a significant research funder, with an annual budget of about €7 million, states its director general, Dr Mary Kelly.
