Coal, Emissions, Gas

Regulations Mandate Zero Discharge of Wastewater

Issue 9 and Volume 106.

THE TWELFTH LARGEST electric utility and the fifth largest gas utility in the U.S., CMS Energy, serves 1.7 million electric customers and 1.6 million gas customers. It is also the 10th largest U.S.-based developer and operator of independent power projects.

In constructing a new 155 MW peaking station in the wilds of Northern Michigan, with winter temperatures of 25 degrees below zero and strict local environmental regulations, CMS Energy faced some unique problems. Besides the plant’s location, the schedule called for the plant to be designed, constructed and in operation in less than four months in the middle of winter. Another mandate for the plant was to have zero wastewater discharge from the plant’s de-mineralized water treatment system. The water is used for controlling gas turbine NOx emissions.

After a meeting between USFilter and CMS Energy in the latter part of 1998, a contract was awarded to USFilter for the design and construction of a de-mineralization water treatment system and to provide a mobile DI system. The new plant, Livingston generating station, is a peaking unit. Final design of the water treatment plant and the project’s details were completed in February 1999. Not only was the 200 gpm water treatment plant required to be fully operational by April 1, 1999, it also had to meet very strict environmental regulations for wastewater discharge.

The water treatment system includes a 600,000-gallon storage tank, re-circulation pumps, three FlexTrex service activated carbon filter units, an ultraviolet (UV) sterilizer and two FlexTrex mixed-bed de-mineralizers. Chlorination and de-chlorination systems have also been installed. During peak demand, May to September, a mobile trailer from USFilter provides additional de-ionized water. This water is also stored in the 600,000-gallon on-site storage tank.

Construction

After breaking ground in mid-February 1999, a heated 132 by 132-foot vinyl tent, with an eave height of 26 feet and 35 feet at the center, was erected. However, three weeks after the tent was erected a freak windstorm destroyed it and all of the equipment that had been installed. As a result, construction had to start all over again, says Livingston Generating Station plant manager Dave Carni.

USFilter drilled 200-foot wells and constructed the outdoor 600,000-gallon storage tank and pre-fabricated building that houses the water treatment system. In order for the system to blend into the rural environment, the tank and building were painted green.

Because the plant is zero discharge a concrete sump was designed and constructed below the floor of the water treatment building. This sump holds wastewater from the de-mineralized water treatment system, the mobile unit and water from the TOC and silica sample testers.

In the off-season there is no demand for the well water. However, to prevent bacterial buildup during the off-season months, the water in the storage tank is circulated through the carbon filters, the ultraviolet sterilizer and the FlexTrex mixed-beds. After leaving the mixed-beds the water is pumped through the turbine building where a closed valve re-directs the water back to the storage tank rather than to the turbines.

Despite the windstorm and system design challenges, the April 1, 1999 target was met. According to Paul Martin, de-mineralized water treatment plant coordinator for CMS, the water treatment plant took less than four months from initial design, procurement and construction.

Carni says he is pleased with the system’s performance and with the servicing of the equipment. “We’ve been happy with the mobile trailer service and also with the service on the water treatment equipment,” Carni says. USFilter replaces the carbon filters, regenerates the demineralizers and maintains the UV sterilizers on a regular basis.