Wastewater Treatment Project at a Steel Mill in Birmingham, UK

Project Title: Wastewater Treatment Project at a Steel Mill in Birmingham, UK

Type of Pollution Treatment: Wastewater treatment from metallurgical steel production

Treatment Scale: Daily treatment capacity of 2,000 tons

Treatment Technology and Process: Physicochemical + Biochemical

Product Used: Polyaluminum chloride, Polyacrylamide, Quicklime

Case Details:

The wastewater discharged during steel production is characterized by large volumes, multiple types, and complex and variable water quality. The wastewater contains production raw materials, intermediate products, finished products, and pollutants generated during the production process that are lost with the water. Indirect cooling water, which is only thermally polluted during use, can be reused after cooling. Direct cooling water, which comes into direct contact with product materials and other substances, contains pollutants and must be treated before it can be reused or used in a series. The metallurgical wastewater mainly contains harmful substances such as acids, cyanides, petroleum products, and heavy metals, as well as alkalis, phenols, cyanides, petroleum products, and heavy metals. If these wastewaters are discharged without meeting standards, they will cause severe environmental pollution, and therefore must be treated.

Wastewater Treatment Process Flow:

The wastewater first passes through a fine grid, which retains a large amount of iron oxide scale and larger suspended solids in the water. Then, it flows by gravity into a regulation tank. After the water quality is balanced, it is lifted by a submersible sewage pump to a distribution well. The wastewater, with a uniform flow rate, enters the contact flocculation sedimentation tank through a tubular mixer. The floating oil is drained into an oil floating tank through an oil collecting pipe. The effluent from the sedimentation tank flows by gravity into a clear water tank, and a water supply pump draws water from the clear water tank to various water consumption points. The sludge from the contact flocculation sedimentation tank is discharged into a sludge thickening tank. After thickening, the sludge is lifted by a sludge pump to a sludge dewatering machine for dehydration. The mud cake is transported outside, and the supernatant from the thickening tank is discharged into the regulation tank for recycling. The dosing system includes three auxiliary chemicals: polyaluminum chloride, polyacrylamide, quicklime, and an acid dosing system is used to adjust the pH value of the effluent.

Considering the actual situation and various factors comprehensively, a suitable treatment process flow was carefully selected to achieve appropriate treatment effects and economic benefits. The main treatment process for steel mill wastewater uses physicochemical methods such as coagulation and sedimentation for removal, with stable treatment effects and simple methods. Most of the oil in the wastewater is removed through oil collecting pipes and flocculation sedimentation, and temporary hardness is removed using the most commonly used lime softening method.