Environmental remediation is always an ambitious task. And the case of the Lower Fox River remediation project in Wisconsin is no exception. To reduce risk to both human health and the environment, the project aims to remediate PCB-impacted sediments from a 21.4-km stretch of river through dredging, capping, sand separation, sediment dewatering, water treatment, and disposal.
Process 375,000 m of contaminated sediment per year
This project remains one of the largest environmental remediations of its kind in the world. The dewatering phase alone would require a completely new system capable of:
- Reliable, cost-efficient treatment of the riverbed's contaminated sediments
- High-capacity dewatering with minimal human intervention
- Achieving a dry solids content in the filter cake optimized for volume reduction
- Excellent quality of the filtrate for further treatment in the water treatment plant
After careful consideration and comparison of several solutions, the customer's bid evaluation selected ANDRITZ SEPARATION for planning, design, manufacturing, installation, and start-up of the membrane filter presses. Together with the customer, Boskalis Environmental, eight ANDRITZ A4 2000 membrane filter presses were chosen as the ideal set-up.
Eight fully automated, cost-efficient membrane filter presses
Each of the eight presses dewater approximately 18 t/h of filter cake, with more than 55% dry solids content. The filter cake is conveyed to a temporary storage building. The presses are equipped with an automatic cloth washing system that cleans the filter cloths using 100-bar pressure. The wash water is collected by means of drip trays.
Two centrifugal pumps in fail-safe design are used for each membrane filter press. In combination with an intelligent, hierarchically structured control system, this allows all eight presses to be operated from a central control room as each press is fully automated.
Easy operation with throughput rate targets exceeded by 10%
By all measures, the collaboration was a complete success. After starting up the plant ahead of schedule in early 2009, it was soon proven that all customer requirements would be met thanks to the plant's reliable, automated, and cost-efficient operations.
Even these initial results were quickly surpassed before the end of the first year. After only a short period in operation, the planned first-year throughput targets were exceeded by approximately 10%. Throughout the ongoing multi-year project, the system has been operated with complete customer satisfaction.