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Waste Activated Sludge

Sludge that has been aerated and subjected to bacterial action, used to remove organic matter in raw sewage during secondary waste treatment.

Waste Permit

Permit issued to allow, with certain conditions, waste discharge into the System. This includes discharge of hauled waste.


Soiled water from homes, businesses and other buildings destined for treatment plants. Water in the combined sewer system becomes wastewater even when a mix of stormwater and wastewater.

Wastewater Treatment Plant

An arrangement of pipes, equipment, devices, tanks and structures for treating wastewater and industrial wastes. A water pollution control plant.

Wastewater User Charge

The costs related to the amount of wastewater discharged to the sanitary sewer system. Measured in hundred cubic feet (CCF’s) for customers with water meters and the number of rooms and indoor plumbing fixtures for customers without water meters.

Water Backup Insurance Program

The financial assistance available to homeowners for MSD-related issues causing backups:

    Overcharged Sewer Line - If excessive rain falls in a short timeframe, it can fill the sewer line so much that it can't hold any more water. If sewer lines discharge into your building as a result, MSD will reimburse up to current limits -- to cover damage that occurs. Because damages may exceed this amount, MSD recommends homeowners obtain additional coverage through their insurance company.

    Blocked Sewer Line - If a sewer line collapses or is blocked by tree roots, or other debris that has washed into the sewer, it can cause a building backup. If this is the cause, MSD will reimburse the homeowner for the adjusted losses. See Financial Assistance for Building Backups for more details.

Water Quality

The suitability of water for given uses as measured by the levels of pollutants it contains. Water use classification, as defined by the State of Missouri, includes: public water supply; recreation; propagation of fish and other aquatic life, agricultural use and industrial use.

Water Quality Rainfall Amount

A value used for design purposes that accounts for the majority of the rainfall events in a given area, but excluding high volume events.

Water Quality Volume (WQv)

The volume of water needed to be captured and treated from a given area for a storm that is equal to the water quality rainfall event.


A natural or artificial channel for the passage of water, either continuously or intermittently.


A region or area bounded peripherally by water parting and draining ultimately to a particular watercourse or body of water.

Winter Quarter (WQ)

Winter Quarter is the average billing calculated on readings, for Residential Metered customers, obtained by your water provider for the timeframe of January 15th through April 30th (representing water usage from mid-December through March) each calendar year.


Wastewater Treatment Plant