MPW's mobile ultrafiltration system can treat up to 1 million gallons of wastewater per day for as long as 8 months. |
The feed water comes from three disparate sources. The first is a basin that collects runoff water from the plant's coal piles, which can experience significant swings in turbidity (from 20 to 1,000 NTU), especially during periods of heavy rain. The second basin contains water from metals cleaning processes, including condensate from the washing of air handlers and the backwash of membranes in the mobile UF trailer. The third basin contains runoff water from the plant's other surfaces.
To treat wastewater from all sources, MPW is providing one trailer-mounted unit and one container unit.
The trailer contains UF technology, which is capable of removing total suspended solids, organics, iron, manganese, and other contaminants. The system consists of two independent racks, each capable of processing 400 gallons per minute. Redundant racks enable one to be cleaned while the other processes wastewater. The "outside-in" hollow-fiber membranes in the UF trailer are capable of rejecting particles as small as 0.02 micron. The trailer also contains automated chemical feed systems for dechlorination, prefiltration, scale inhibiting, and pH control.
The container unit, meanwhile, neutralizes the water and controls the entire wastewater process, which is conducted on a batch basis 24 hours per day with one MPW worker per shift. Four totes with double containment, pipes, pumps, computers, and a lab all fit in a container box measuring just 53 feet by 8.5 feet.
In accordance with state permits, treated water must meet turbidity and pH requirements before being discharged. Average turbidity cannot exceed 100 NTU on a daily basis and 30 NTU on a monthly basis. The pH must be between 6 and 9. To meet compliance requirements, turbidity and pH are measured online during processing. In addition, composite samples are collected on a 24-hour basis and analyzed at an independent laboratory.
A custom-built and installed network enables workers in the power plant's control room to monitor the wastewater system remotely. Information technology experts from MPW worked on site with their counterparts at the power plant so the signals from the computer program that controls the wastewater system could be sent via a wireless transmitter to the system that controls the plant's other operations.