WATER POLLUTION CONTROL FACILITY

Plant Description & Function

The Winooski Water Pollution Control Facility is located at the end of West Allen Street adjacent to the Winooski River. The plant went on line in February of 1971, financed by federal, state and local funding. It is equipped with "extended aeration" secondary treatment capabilities with a design capacity of 1.2 million gallons per day (MGD). Extended aeration is a process which creates an environment for naturally present aerobic bacteria to carry out organic digestion of incoming wastewater. Sodium aluminate is added to the process to chemically reduce total phosphorus levels prior to discharge into the Winooski River.

In 1996 the engineering firm of Forcier, Aldrich and Associates performed a 20-year plant evaluation mandated by the State of Vermont. Overall, the study showed the facility to be in excellent condition, however some original equipment at the WPCF was in need of replacement to meet current design standards. Winooski voters passed a $1,200,000 bond vote in March of 1996 to upgrade the WPCF with new equipment. Upgrade of treatment capacity was viewed as being more cost-effective than correcting all of the deficiencies identified in the sewer collection system. Construction was completed in the summer of 1999.

Recent upgrades included the grit collection and secondary clarification systems. Removal of grit from the influent eliminates burden on plant processes (ie., pumps, settling tanks, etc.), improving plant efficiency. New secondary clarifiers replaced inadequate original units; the old units were undersized for peak flows, risking release of sludge into the river. Overall, the plant upgrade has made the facility more flexible and able to handle excessive infiltration.

Flows through the plant vary enormously from 0.8 MGD to 4.0 MGD; high flows are attributed to groundwater infiltration and illegal connections to the collection system --primarily via sump pumps. Such variable flows through the plant can be "tamed" through collection system repair and enforcement of cross-connection ordinances.

Sludge is a by-product of wastewater treatment. The City participates with the Chittenden Solid Waste District (CSWD) for disposal of treatment plant biosolids (sludge). Biosolids are transported to Quebec, Canada and land-applied to agricultural lands. Pollutants, including dangerous heavy metals, are concentrated in sludge; from environmental, social responsibility, and liability standpoints, it is in the best interest of the City to minimize heavy metal content in its sludge.

Citizens are urged NOT to dump hazardous chemicals down the drain. CSWD and the Lake Champlain Basin Program (LCBP) have programs available for disposal of household hazardous waste and hazardous waste reduction. Use of hazardous chemicals is discouraged whenever possible as they can pose a threat to human health and the environment. Simply put, what goes down a drain --even though it is cleaned up as best as possible at the treatment plant-- is discharged into the Winooski River and Lake Champlain; our tap water comes from Lake Champlain. Additionally, the City of Winooski and CSWD will continue to work with local businesses to minimize discharge of pollutants into the collection system and treatment plant.

Collection System Recently the City has been monitoring and documenting its condition via videotape and data collection. In many locations illegal connections of roof and foundation drains, and sump-pumps, contribute clean water to the system. Additionally, cracking, collapse and shifting of Winooski's aging pipes in many areas causes groundwater infiltration which contributes to unnecessary flows into the sewage treatment plant.

Above: A suspected sump pump connection.

It is in Municipal and sewer service rate payers' economic interests to limit groundwater infiltration and eliminate illegal connections to the sanitary system as as such connections contribute excess volume to the plant. This added volume 1) increases treatment costs in terms of energy and chemicals; 2) adds "wear and tear" to the facility, causing premature need for maintenance and repairs; and, 3) "robs" the City of reserve treatment capacity which otherwise could be utilized for new development. Local ordinances are in place which prohibit cross connections into the sanitary sewers; these will be enforced.

Many of the City's damaged sewer pipes can be repaired by in situ slip-lining at a significant cost savings over excavation and replacement. The Engineering, Public Works and Wastewater Department are investigating the possibilities for Winooski. Recent construction cost estimates have indicated that a continuing annual appropriation of at least $100,000 is required to repair Winooski's sanitary collection system.