Somerset-based Hydro International has developed products to control stormwater and treat wastewater to improve quality. Its products include technologies used to control urban run off, treat storm water, for combined sewerage outflows and treat municipal waste water. This includes removing rubbish, oil and sediment from rain water and removing grit during water treatment. The UK, Ireland and the US are the main markets. Hydro was formed in 1980 and it originally floated on the main market of the London Stock Exchange. It moved to Aim in 2004.