A temporary pre-treatment solution for remote coal ash disposal

Meeting new discharge limits while controlling costs

Challenge

When state regulators issued new discharge permits for a major power utility’s ash basin, the remote location and its lack of permanent power made it extremely challenging to comply. the utility needed a system that could remove water from an ash basin where precipitation continued to enter, as well as meet the new water quality requirements for tss and Ph. a dewatering system that offered pre-treatment was needed to maintain water quality until a full-scale water treatment facility was required. this system had to be able to monitor several variables such as pond level, tss, and Ph limits, and daily discharge limits. in addition, the entire system had to be fully automated and monitored continuously during operation with data recorded automatically and retained for record keeping requirements.

“This system had to be able to monitor several variables such as pond level, tss, and Ph limits, and daily discharge limits. ”

Solution

To provide complete control of the system, Xylem built a custom control panel with an HMI (human-machine interface). to eliminate the need for a generator, a solar powered skid was added with three chemical injection pumps to provide pretreatment when needed. the addition of automated valves to the system eliminated the need for an operator except for daily starting and stopping of the system. if water quality limits were approached, the system would begin dosing the needed chemical to adjust the water quality. if the limit continued to climb, the system would send out an alarm, actuate the valves, and go into recirculation mode back to the raw water source until water quality improved. Once levels returned to normal the system would switch valve positions and start discharging again. MJK Flowmeters on both sides of the valves provided verification that valves changed position, while YSI TSS and pH probes ensured water quality of the effluent. For greater peace of mind, the Godwin custom control panel also provided remote viewing of the system’s run status, as well as the required data recording and storage this project demanded.

Result

Pretreatment Image 3.png Xylem’s dewatering and pretreatment solution allowed our customer to meet their regulatory permit requirements while controlling labor and fuel costs – eliminating the need for a complicated, expensive water treatment system for several years. remote system status and

“The addition of automated valves to the system eliminated the need for an operator except for daily starting and stopping of the system.”

data recording and storage provided peace of mind for the power utility. the custom control panel with solar skid reduced the need for any operators onsite to monitor multiple variables. and because all of these products were manufactured and rented by Xylem, our cross-product engineering support ensured seamless integration and reliable performance.

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