Challenge
A steel mill located in the Ohio River Valley of the United States had been treating raw river water via a clarifier, gravity filters, multi-media filters, cartridge filtration, and reverse osmosis(RO) to produce demineralized water for the mill rolling lines. In 2014, the mill began experiencing numerous problems with high solids carryover from their aging clarifier to downstream equipment. The clarifier was designed to provide water with turbidity of < 1 NTU to the downstream equipment, yet due to upkeep was allowing water with turbidity as high as 50 NTU. The high solids carryover from the clarifier overwhelmed the downstream multi-media filters and led to problems with the cartridge filters and reverse osmosis membranes. These issues became crucial when the mill began experiencing lost production due to a shortage of purified water.
The mill elected Evoqua Water Technologies over other suppliers to utilize their mobile ultrafiltration (UF) technology.
Solution
In March of 2014, the mill entered into a short-term operating agreement with Evoqua that included a UF trailer system with operations, maintenance, replacement consumables, chemicals, and a process performance guarantee
by Evoqua. The UF trailer provides up to 1,000 gpm of high quality filtrate enabling the mill to produce the required 560 gpm RO water. The Evoqua UF system is fed directly by river water, bypassing the clarifier, gravity filters, and multi-media filters.
Due to the successful operation of the Evoqua UF system and its economical benefits to the mill, the initial agreement was extended. Within the twelve month period that the trailer has been in operation, the incoming river water ranged in temperature from 32-86 °F and exhibited average turbidity of 38 NTU to peak turbidity exceeding 700 NTU. Evoqua’s UF trailer operated without fail throughout this period, successfully removing suspended solids and reducing the turbidity to an average of 0.16 NTU with silt density index (SDI) consistently below one. Evoqua's UF trailer mounted system placed upstream of the intial RO equipment replaces multiple pieces of alternative equipment while supplying the mill with a consistent supply of purified water.
Results
The high-performing UF equipment enabled the downstream RO equipment to more efficiently eliminate 98 percent of the river water conductivity. The UF
trailer reduced the consumption of cartridge filters to 1x/month
and reduced RO membrane cleaning to once a year. RO membrane life was improved by a factor of greater than three.
Evoqua’s new UF system saved the mill more than $145,000 per year in annual operating expenses. Most importantly, the reliability of Evoqua’s UF trailer has prevented the mill from losing $30,000/hour in lost production costs.