Northwest Harris County MUD No. 15 Wastewater Treatment Plant

An aging above grade steel package activated sludge plant had previously been downgraded from 750,000 gpd to 546,000 gpd due to limited clarifier area. Development in the area among several utility districts required the District to expand the plant to 1,530,000 gpd.

The activated sludge treatment plant expansion includes a new concrete aeration/clarifier unit that has the aeration basin divided into two basins, allowing use of part of it for sludge digestion up to a flow of 920,000 gpd. Above that flow, all the aeration basin volume will be used for aeration and waste sludge will be sent to the existing package plant, which was converted to sludge stabilization and thickening use.

Included in the design were two rotating drum fine screens, each with its own ram type screenings compactor to provide total backup in case of mechanical failure.  Also included in the design were; new multistage centrifugal blowers in a new blower/operations building; a high capacity non-potable water supply system; and a sludge pumping system to transfer aeration basin mixed liquor to the digester or alternately, to the plant sewer for odor control of the influent sewage, if required.

Effluent disinfection is accomplished using liquid sodium hypochlorite (bleach).  Sodium bisulfite is used for dechlorination after the disinfection process to protect the receiving stream. Two 6,000 gallon bleach storage tanks and two 2,000 gallon sodium bisulfite storage tanks are installed under a roof cover structure. Chemical metering pumps are installed in separate fiberglass shelters adjacent to the storage tanks.  

A comprehensive plant site layout provides for expanding the plant to up to 3.0 MGD average daily flow with space allocated for future effluent filters and sludge dewatering facilities.