OVERVIEW

This ash pond at an electric power plant was scheduled to be cleaned and closed. The engineers on site anticipated the wastewater treatment plant on-site could not handle the heavy solids in the water as they lowered the pond. They determined the need for a system to pretreat the water to remove solids at 1,500-gpm. This flow rate would allow them to remove the water from the pond and catch up with rain events as they occurred. They wanted to capture and dewater the solids and then load them up and send them to the landfill nearby.

SOLUTION

WaterSolve was called in to test the residuals in the ash pond for optimum chemical treatment and recommend a dewatering system that would handle the 1,500-gpm of flow.  The plant engineers wanted a system that would provide individual dumpster dewatering tubes that could be hauled to a landfill. WaterSolve worked in conjunction with the engineers to develop a containment pad, a chemical feed building, and an automated chemical feed system.

A dewatering tube containment pad was designed to contain a minimum of 24 dumpster tubes each having a capacity of 30 cubic yards. A 10” HDP pipe entered the pad with 24 valves having 3” male camlocks that connected hoses to the tubes. This allowed some to be filling, some dewatering and drying, and some staged and ready to fill.

The WaterSolve automated chemical feed system had a 10” flow meter sending flow data to a computer which could start and stop the system as well as adjust the chemicals relative to the flow rate in the 10” pipeline. The WaterSolve products Solve 426 (a coagulant) and Solve 9330 (a flocculant) were found to bring the best water release, clarity, and flocculation. They were injected into the pipeline at strategic locations to flocculate the residuals prior to entering the dumpster tubes.

The chemical feed building was designed to keep the automated chemical feed system and supplies out of the weather and protected from rain and winter cold. A 3-month supply of chemicals and tubes was stored in this insulated building. A 2” water supply line was plumbed, and a booster pump was available to raise water pressure if needed. Lighting and an ample supply of electrical service were also installed in this building.

THE RESULT

Two WaterSolve technicians were on-site to install the chemical feed system and get it running. One stayed to train those on-site to operate and maintain the system. The design for this project was a huge success. The overall solids in the water were lighter than anticipated. Those on-site decided the tubes could be placed in or out of the dumpsters and the tubes outside the dumpsters dewatered better and faster. The 1,500-gpm capacity was met and they kept pace with rain events and lowered the water table in the pond as planned. The wastewater plant operators were happy with the water they received from the process as they kept pace with the daily flow while the project progressed.