Using shellfish to clean wastewater

By Blair Andrews, Farm & Food Care

University of Windsor chemist Bulent Mutus holds samples of chitosan that were tested in his lab to filter phosphorus and micronutrients from wastewater. Encouraged by promising results, the method will be tested this growing season in the field.

(Windsor) – Ontario researchers are testing a new way of removing phosphorus and micronutrients from wastewater. Dr. Bulent Mutus, a chemist at the University of Windsor, has developed a bio-filter made from chitosan, the hard material from shellfish.

The filters, which have produced promising results in the lab, are going to be tested this year at three agricultural sites.

“It’s very heartening that we can do this in a laboratory scale,” says Mutus. “This agricultural scale will tell us whether our lab results can be extrapolated to the real situation.”

Dr. Mutus’ project was one of 17 that were funded partially through the Water Resource Adaptation and Management Initiative (WRAMI) administered by Farm & Food Care. The WRAMI project supported research into improved agricultural water management.

The release of nutrients from agricultural and other wastewater systems is a major environmental issue. The growth of algal blooms in Lake Erie resulting from an excess of nutrients in the water has been a key concern in recent years. After the blooms die off, bacteria remove the oxygen from the water for fish and other aquatic life.

“It’s not the algae that are killing the lake, it’s the abundance of algae and the bacteria getting rid of the dead algae that is the problem,” says Mutus.

Mutus’ team has been testing different chitosan-based materials in the search for a simple and inexpensive solution. The chitosan can be broken down and made into a powder that can then be shaped into different forms. In one case, the powder was converted to tiny beads by treating it with chemicals and then drying it.

“These beads were very efficient in removing micronutrients like copper, zinc, iron and manganese,” says Mutus.

They found that beads also removed significant amounts of phosphate. But converting the powder to beads is an expensive process. The researchers found that they could boost the effectiveness of chitosan flakes by treating them with copper.

“Making those beads consumes a lot of energy and chemicals, whereas you just buy the flakes off the shelf and put copper on them and they’re ready to go,” says Mutus. “You don’t have to waste any extra energy or money on them making them from scratch.”

Moving from the lab to the field, the chitosan-based filters will be tested alongside two other types of filters at three agricultural source points – wash stations at two vegetable farms and the tile drain of a sod farm. The other systems use wood chips and red sand, respectively.

“These will be put side-by-side and essentially it’s to see which one works best,” adds Mutus.

The chitosan system consists of two filtration units. One will contain the copper-treated chitosan. The second one will only have chitosan to guard against the chance of any copper leaking into the environment. There will also be a pre-filter that will remove solids, such as mud in the water.

Whereas the lab was a more controlled environment, Mutus notes that dealing with rainfall, temperature changes and other water quality variables will be among the main challenges of testing the systems in the field. If all goes well with the field tests, Mutus says the filter systems can be installed where there are source points of phosphorus.

“We see it as the end-user would purchase these and the company would supply them with re-generated filters,” says Mutus, noting that there is a potential to generate some economic spin-off from the idea. “The company we’re collaborating with is an Ontario industry, which would develop that business and also help in the lessening of the phosphate load of point sources into waterways.”

This article is one in a series of innovation profiles about projects underway in Ontario agriculture produced by Farm & Food Care Ontario.

 

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