Challenge
Is it possible to reduce sewer costs in a facility that operates a cooling tower, evaporative condenser, irrigation system, or large humidifier? Many water and sewer utilities offer sewer deducts or evaporation credits if the facility meets their requirements for metering or sub-metering. In most cases, a small investment in equipment and operating procedures is necessary.
Some water utilities require their customers to purchase and install the utilities’ sub-meters. Others will require the customer to purchase, install and maintain their own sub-meters, read the sub-meters periodically, and report the readings to the utility. Failure to report as required can result in the site being pulled from the program forfeiting all future credits. Identifying your local utility’s procedures can be tedious and time consuming.
One major big-box retailer had over 300 cooling towers in service with less than 10% realizing evaporation credits. Working with the retailer’s Facility Maintenance team, a program was established to maximize credits in as many sites as possible.
Best Practice
Where allowed by local sewer authorities or municipal water companies, sub-metering a cooling tower or evaporative condenser is the most effective method of capturing evaporation credits or sewer deducts. Some cities require one sub-meter on the tower makeup line, while many also require a second sub-meter on the tower bleed or blow-down. In rare instances, a third sub-meter may also be required on the tower drain or overflow line.
Many water utilities will read cooling tower sub-meters with their own equipment or meter readers. In cities where the customer is required to read sub-meters, Trident Network’s MeterReader™ is very effective. The MeterReader™ transmits meter readings via cellular connection, eliminating the need to install costly network cables to the penthouse or equipment room of the building.
Trident’s MeterReader™ can be very useful for every cooling tower by providing daily monitoring of the tower’s water flow. Failed bleed or blow-down solenoids can be identified, as well as broken or stuck fill valves. Tower cycles can also be calculated to determine the effectiveness of the water treatment program. Early detection of water flow issues can result in direct savings in water consumption.
Results
Evaporation credits can apply to retailers, hospitals, property management firms, hotels, grocery chains, data centers, and any business that operates cooling towers, evaporative condensers, irrigation systems or large humidifiers. The investment in time and equipment will range from a letter to a sewer authority to engineered drawings, application fees, sub-meters, remote transmitter, and a backflow preventer. Total project costs are generally low with Return on Investment (ROI) averaging 10 to 14 months. Actual ROIs may vary from 2 months to 24 months depending on factors such as tower size, hours of operation, climate, sewer rates, equipment required, etc.
Verification of Efficiency and Savings Captured
Water and sewer charges are reviewed annually for each site in the program. The major big-box retailer referenced above now has 89 sites in their program with annual savings over $500,000. Annual savings will continue to grow as sewer rates increase across the country. Average (ROI) has been under one year, with some sites coming in at two months and others at twenty-four months. Costs vary depending on local requirements and equipment needed. Each site was evaluated individually.
In addition to reduced sewer charges, several equipment malfunctions were identified during the cooling season including:
- FL – makeup and blow-down volume almost same daily. Found bad flow switch – replaced and problem resolved.
- CA – no flow on blow-down meter. Found overflow drain had been cut and re-routed with sump pump to alternate drain. Chemical treatment program not effective risking fouling of chiller tubes.
- FL – Customer’s manual meter reading process stopped after personnel changes. MeterReader™ and new meter installed to capture credits going forward – annual savings approximately $9,734.
Billing issues were also found during the season as a result of annual reviews of each site:
- WA – Monthly sewer credits found to be extremely low. A several week investigation found City miscalculating credits each month for 3 years. Resulting credit was $5,910.
- MD – Sub-meter installed, but not entered into utilities customer billing system. No credits issued. Correction produced a $2,950 credit.
- OH – Review of credits found City’s billing system had omitted credits for much of the year. Resulting credit was $1,169.
Summary
Evaporation credits can produce substantial savings and free up capital for energy projects or other equipment replacements. A small investment can prevent profits from evaporating and reduce water and sewer expenses. In addition, LEED points could be available for sub-metering cooling towers.
