The thousands of tons of waste seashells created by the edible seafood sector are being used to treat wastewater in a new project undertaken by researchers at the University of Bath in the UK.
Dr Darrell Patterson, from the University’s Department of Chemical Engineering, used waste mussel shells to create what he says is a cheaper and more environmentally friendly way of ‘polishing’ wastewater, which could remove unwanted substances such as hormones, pharmaceuticals or fertilizers.
Traditional wastewater treatment takes place in 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; and 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, which removes any final trace contaminants.
The photocatalytic process normally requires titanium dioxide. Patterson says replacing the expensive compound with a material from the calcium derived from seashells, called hydroxyapatite — which can also be found in teeth and bones — can significantly reduce the cost of the process, while reusing a traditionally wasted 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,” Patterson said. ‘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, according to Patterson.
The project will now go on to look at the wider applicability of this technology and the potential scalability of shell-based photocatalysts to industrial level.
The full text research paper can be seen here: http://opus.bath.ac.uk/34853/.
The UK seems to be bursting recently with innovative solutions to food waste: London-based startup Rubies in the Rubble is employing out-of-work locals to make hand-crafted chutneys and jams using previously wasted fruits and vegetables from nearby markets; grocery chain Waitrose announced last fall it had achieved its aim of sending zero food waste to landfill two months earlier than planned, converting all leftover food to biogas through anaerobic digestion; and in June, Edinburgh-based start-up Celtic Renewables announced it is turning waste matter from whisky production into biobutanol, a “next-generation biofuel.” If the new process proves effective and scalable, the researchers say it could result in a $90 million dollar value for the biofuel industry.