When the McGraw Hill Data Center in East Windsor, N.J., was being built, the local municipal authority informed the company that it did not have the capacity to support the makeup water for the data center’s condensers or chill water plant. A new well was drilled to serve the plant; however, the groundwater supply had iron and manganese levels that exceeded regulatory limits.
Iron and manganese levels in the groundwater were 5 mg/L and 0.11 mg/L respectively, well above the U.S. Environmental Protection Agency’s secondary maximum contaminant levels of 0.3 mg/L for iron and 0.05 mg/L for manganese. The water chemistry also presented a problem due to a low pH of 5. The cooling towers fed by the groundwater supply aerate the iron in the water to ferric hydroxide, which fouls the towers and creates significant maintenance issues.
After the civil engineer at the site tested the well and confirmed the high iron and manganese concentrations, he recommended AdEdge Technologies Inc. to McGraw Hill for its treatment solution. McGraw Hill contacted AdEdge in late 2007 to design and implement an iron and manganese removal system for the facility.
System Basics
The treatment system AdEdge provided is a skid-mounted AD26 oxidation and filtration packaged unit rated for a maximum design flow of 150 gal per minute (gpm). AdEdge Packaged Unit (APU) systems are designed as turnkey treatment solutions for a variety of contaminants. System features include differential pressure switches, local control panel and gauges, flow sensors and totalizers, and a central hydraulic panel with sample ports for pH and chlorine monitoring.
The APU system is fully automated and integrated into the existing building space and linked to the data center’s supervisory control and data acquisition (SCADA) system to provide continuous remote monitoring. The treatment system’s three carbon steel vessels are configured in parallel and each vessel utilizes 20 cu ft of AdEdge’s AD26 media. The NSF 61-certified manganese dioxide media is highly catalytic for the oxidation and removal of iron and manganese.
Treatment Process
Prior to entering the treatmentsystem, water from the well is injected with potassium hydroxide via a chemical feed module to raise the pH from 5 to between 7.5 and 8. After the pH is raised, the water is injected with sodium hypochlorite via a chemical feed and monitoring module to oxidize the iron and make it more receptive to the AD26 media. After the chemical introduction, the raw water is treated in the iron and manganese treatment system using the AD26 media.
The system is equipped with automated control valves and harnesses, a central control panel with programmable logic controller (PLC) and a color user interface screen. The PLC performs the automated functions needed for proper operation of the control valves, system pressure and differential pressure to activate backwashing, alarm status and other parameters such as low- or high-flow status. The PLC is integrated into the SCADA system, providing remote monitoring for the treatment system.
Treated water enters two 5,000-gal cooling tower water supply tanks that are fed by an AdEdge-supplied duplex VFD-controlled booster pump skid. The system’s PLC controls the backwashing of the treatment vessels from a backwash supply pump skid. This occurs once or twice daily to remove precipitated solids captured in the filters.
Positive Results
The treatment system began operation in July 2008 and has experienced little to no down time since installation. It has a high utilization factor, receiving water nearly 22 hours per day to meet cooling tower demands. Approximately 110 gpm of well water with iron and manganese levels exceeding 4 mg/L and 0.1 mg/L respectively is being consistently treated to below the treatment goals of 0.3 mg/L for iron and 0.05 mg/L for manganese.
Onsite technicians perform chemical testing daily and have found that iron and manganese are at non-detectable levels. Al Turner, technical services manager at the McGraw Hill Data Center, said “the system is very low maintenance [and] very successful in the iron removal.”
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