Washington Suburban Sanitary Commission (WSSC) Seneca Waste Water Treatment Plant Weir Gate Replace Clarifier Distribution

Meltech completed this project for the replacement of the existing clarifier distribution box at the Weir Gates at the Seneca wastewater treatment plant. A clarifier distribution box is generally used to remove solid particulates or suspended solids from liquid for clarification and/or thickening. Concentrated impurities, discharged from the bottom of the tank are known as sludge, while the particles that float to the surface of the liquid are called scum. In smaller wastewater treatment facilities only one clarifier it is useful to know the clarifier’s surface level. In larger waste water treatment plants where influent flow is routed through a distribution box (splitter box) to many clarifiers, there may be insufficient room inside the distribution (splitter) box to accommodate level instrumentation. In this instance level monitoring of the clarifier will help attain proper load balance. 

Meltech completed the replacement of the existing clarifier distribution box. All of the shutdowns were coordinated with plant operations, limited to four (4) in duration and planned from 1:00am – 5:00am. 

Meltech provided temporary pumps for the pump around system. We provided two 6” trailer trash pumps with a total of 240 feet of solid flexible pipe and strainers. 

Each pump was specified for; 2400 gpm capacity, 18 feet left suction, 150 feet total dynamic head and 6×6 inch suction x discharge. 

The suction location was located from the Mix Liquor Channel and the discharge location was completed into boxes of clarifier gates not being replaced. Two (2) sump pumps (115v) were provided to pump the water draining into the Mix Liquor Channel. 

Meltech also completed the construction of the temporary wooden weir structure behind the gate opening to contain the flow in the event the weir gate replacement could not be completed. The corresponding clarifier was drained to install the wooden weir structure. 

Meltech completed the shutdown of the entire system to complete the work. We completed the installation of stop logs, demolition of the weir gate, installation of temporary wooden weir gates and the installation of the stainless steel weir gates which took place under separate plant shutdowns. 

The project required protection of the existing facilities and limited interference requirements for vehicular traffic entering and leaving existing facilities.