Seashells from food waste used to produce drinking water

Wastewater could be treated using seashells left over from restaurants, hotels, commercial farming and other foodservice outlets, according to research by scientists at Bath University. This could provide "significant" savings if the system can be scaled up to industrial level.

Traditional wastewater treatment takes three stages. The first involves the removal of any solids and oils, the second filters the water and degrades the biological content of the sewage derived from human waste, food waste, soaps and detergent.

Finally, a tertiary treatment – called ‘polishing’ – is used to further improve the quality of the water before it is released. This process also removes unwanted substances like hormones, pharmaceuticals and fertilisers.

There are different methods of tertiary treatment, and one of the most effective is the photocatalysis of water to remove any final trace contaminants. This process normally uses titanium dioxide, which is expensive.

By replacing this with a material from the calcium derived from seashells called hydroxyapatite – which can also be found in teeth and bones – researchers are aiming to significantly reduce the cost of water treatment by reusing a renewable unwanted waste product.

“Mussel and other seashell farming is a fast growing industry around the world and the increase in the production of shellfish generates a large amount of shell waste,” explained Darrell Patterson from the University’s Department of Chemical Engineering.

“Shells are a calcium rich resource that can be used to produce calcium oxide (lime). This lime can be used in several different ways in environmental technologies, and our study has shown that the hydroxyapatite formed from them is an effective, green and potentially cost-efficient alternative photocatalyst for wastewater treatment.”

The research was carried out using mussel shells, but other types of seashell could feasibly be used to produce photocatalysts, making this technique globally applicable, said Patterson.

The project will now look at wider applications of the technology and the scaling up of shell-based photocatalysts to industrial level.

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