Steel Mill Water Recycle

For a strip steel mill in the central United States, the need for a system that was more consistently compliant with discharge regulations to a small stream, with reduced expenses for sludge disposal, and that allowed them to recycle water were critical objectives for their new wastewater treatment system. The solution was a Duraflow Tubular Membrane Filtration process followed by a Reverse Osmosis (RO) system.

The major contaminants the mill needed to remove include Nickel, Copper, Iron, Cobalt and Zinc. To work, the system first starts with a flow equalization collection tank followed by caustic precipitation. Then the heavy metal solids are filtered by the Duraflow Tubular Membrane Filters and filtrate is desalted with an RO system. The RO permeate is then returned to an on-site reservoir for re-use as rinse water in the production process while the reject stream is directed to a NPDES-permitted discharge or to the city POTW.

The entire Duraflow Tubular Membrane Filtration system is comprised of 96 modules with each module containing 10 one-inch diameter tubes. Using a cross-flow configuration for the maximum efficiency, the system is in operation 24 hours a day, seven days a week. The modules are split into two skids with one in operation and one in standby mode at all times.

For servicing, the Duraflow Tubular Membrane Filtration system requires cleaning every 3-4 days to maintain maximum efficiency and the modules are replaced every 5-6 years. For the RO unit, the system is cleaned every 5-6 months and those modules are replaced every 4-5 years.

To see a complete analysis of the entire system, including details about the filtration system, the chemical precipitation process and a diagram of the components, read the full case study.