Seafood shells to treat wastewater

The edible seafood sector creates thousands of tonnes of waste seashells, but now the University of Bath has found a way to re-use these shells in a wastewater cleaning project. Their study can be found here.

Traditional wastewater treatment takes three stages: the removal of any solids and oils; filtering the water and degrading the biological content of the sewage which are derived from human waste, food waste, soaps and detergent; and a tertiary treatment to further improve the quality of the water before it is released. One of the most effective methods of tertiary treatment is the photocatalysis of water to remove any final trace contaminants - but this process normally uses titanium dioxide, which is expensive.

Dr Darrell Patterson, from the university’s Department of Chemical Engineering, aims to replace titanium dioxide with a material from the calcium derived from seashells called hydroxyapatite (also found in teeth and bones). He says this would be a cheaper and more environmentally friendly way to remove from wastewater unwanted substances such as hormones, pharmaceuticals or fertilisers.

“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,” Dr Patterson said.

The research was carried out using mussel shells but it is feasible that other types of seashell could be used to produce photocatalysts, making the technique globally applicable. The project will go on to look at its wider applicability and the scaling up of shell-based photocatalysts to industrial level.

Dr Patterson noted, “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.” Re-using this waste for the treatment of wastewater is thus an extremely useful application.