Challenge

CMS Energy needed to design and build a water treatment system to feed the turbines at the 155-megawatt Livingston Generating Station. The system had to withstand extreme cold and satisfy stringent environmental regulations. It also needed to meet a peaking station's intermittent need for reliable demineralized water.

The peaking station, located in Northern Michigan, faced the following challenges:

• Winter temperatures of 25 degrees below zero
• Intermittent water needs, between May and September only
• Designing, building, installing, and starting up a water system in less than four months, in the middle of winter
• Designing a water system that could run by itself with no operator to monitor the controls
• Designing a system that would not discharge wastewater to the environment and could handle NOx reduction requirements in aeroderivative engines
  
  

Solution

In four months, Evoqua Water Technologies designed and built a 200-gallon-per-minute demineralization system and also supplied mobile deionizers to keep Livingston Generating Station up and running whenever they needed to generate power, no matter what the weather. Evoqua drilled the 200-foot wells and erected the outdoor storage tank and the pre-fab building that houses the water treatment system.

The system includes:

• chlorination and dechlorination
• 60,000-gallon storage tank
• Recirculation pumps
• Three FlexTrex® service carbon units
• Ultraviolet sterilizer
• Two FlexTrex mixed-bed demineralizers
• Programmable logic controller (PLC) and alarms for system monitoring
• Mobile deionization trailer from an Evoqua branch that treats well water and sends it to the storage tank during peak demand between May and September
  
  

Results

The system does not discharge any wastewater to the environment. A concrete sump below the floor holds any wastewater produced by the process water system and drain-down water from the mobile trailer. Wastewater is drained from all the exchange carbon and mixed-bed polishing vessels into the sump. When the new mobile trailer arrives, the sump water is pumped into the trailer, where it is treated before being sent to the storage tank for reuse.

During the off-season, there is no well water going into the system. The water that is already in the storage tank is sent to the DI recirculation pumps, into the carbon, through the ultraviolet sterilizer and into the FlexTrex mixed beds. The water then goes to the pump skid in the turbine building, where a closed valve re-directs the water back to the storage tank rather than to the turbines. This way, water is circulated through all the distribution lines to prevent any bacterial buildup.

Despite the weather and system design challenges, Evoqua met the project's tight deadline. The mobile trailer from the Columbus, Ohio branch and local service from the Hazel Park, Michigan branch on the carbon units, demineralizers and ultraviolet sterilizers ensure reliable, demineralized water for this peaking station.