Waste Seashells can Solve Waste Water Problem

The thousands of tonnes of waste seashells created by the edible seafood sector are being put to use by the University of Bath (UK) in a new waste water cleaning project.

Dr Darrell Patterson, from the University’s Department of Chemical Engineering, used waste mussel shells to create a cheaper and more environmentally friendly way of ‘polishing’ waste water, which could be used to remove unwanted substances like hormones, pharmaceuticals or fertilisers.

Traditional wastewater treatment broadly 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 which are derived from human waste, food waste, soaps and detergent.

Finally a tertiary treatment is used to further improve the quality of the water before it is released. 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, Dr Patterson is aiming to significantly reduce the cost and reusing a renewable unwanted waste product.

Dr Patterson said: “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.

“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 waste water 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.

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

The University of Bath is building a large portfolio of water-related research, having recently announced a new partnership with Wessex Water.