The Dee Estuary was industrialised from quite early on in the Industrial Revolution, and some industry remains today. Notable among these are Shotton Steel, formerly owned by John Summers & Sons, and now owned by Tata Steel; the gas-fired power station at Connah's Quay; three separate paper mills; a chemical manufacturing plant; and numerous smaller manufacturing industries. The estuary also receives the treated sewage effluent from Queensferry works and from Chester sewage treatment works. At the mouth of the estuary is the natural gas sweetening plant at Point of Ayr on the site of the former colliery. There are also commercial docks at Mostyn although their use is limited by the tide.