Treatment Plant History
The existing Piqua Wastewater Treatment Plant was originally constructed in 1957-1958. It had a nominal design capacity of 4.0 mgd and a peak-pumping rate of 7.0 mgd. The original plant consisted of barminutors, raw sewage pumps, raw sewage metering, chemical mix basin for feeding lime and ferric chloride, pre-aeration basin equipped with grit collector equipment, two (2) primary settling tanks, four (4) aeration basins, two (2) secondary settling tanks, one (1) plant effluent pump, two (2) anaerobic digesters with floating covers, and a sludge dewatering vacuum filter.
In 1969, additional treatment units were added in order to upgrade the performance of the plant. The additional units included one (1) secondary settling tank, chlorination building with a chlorine contact tank, and an aerobic digester process.
In 1984, modifications were made to the existing anaerobic digestion system, gas handling, and flow monitoring systems. This was needed to meet the increasing and more stringent discharge regulations. The modifications included replacement of an existing anaerobic digester cover to a fixed lid configuration. The gas mixing handling system was modified to include three (3) gas bubble-mixing guns. Flow metering equipment and modifications were added to existing primary and secondary settling tanks.
The 1988-1989 Plant Expansion added many new tanks and equipment to help meet the Clean Water Act Regulations of 1972. The Methane Gas created in digestion of sludge is used to burn in the sludge heat exchanger for the pathogen treatment of biosolids. During this time period a new “Caterpillar” methane-burning engine with blower was added, for the plant’s aeration purposes and to save on electrical energy costs. Three (3) new screw-type raw sewage pumps were added along with a new wet well area. A new grit and grease process removal system with new flow channels and equipment was also added. A new primary settling tank, two (2) new aeration basins (2 passes per basin) with all the aeration receiving four (4) new internal recycling pumps to aid in the ammonia removal, and two (2) final settling clarifiers (with piping and electrical for a 5th tank expansion, if needed). The plant tunnels were expanded, all plant mechanical HVAC and separate plant electrical power supply feeds with a main switch – over gear were installed, administrative offices were added and a new plant computer operating system was installed at this time. A Centrifuge for dewatering sludge with all associated piping and pumps were added along with a new building to house it. Three (3) new river pumps were added at the Post Aeration Well (pumping allows discharge to river, even when the river level is higher than the plant’s discharge line). Along the entire length of the plant on the gravel pit quarry side, a retention wall was built and the entire plant was enveloped with 6’ high chain link fence (approx. 6 acres).
Since the 1988-1989 Plant upgrade, numerous modifications include adding more equipment onto the flushing water system (recycles the plant effluent discharge water that goes into the river and reduces the costs of using City of Piqua treated water). A building was erected for the grit & grease facility along with installing a new grit classifier and rag press. A dechlorination system was added due to EPA regulating more stringent limits on Chlorine. A new three (3) bay Maintenance Garage plus work area, office/storage loft, and basement for storage at the Wastewater Plant has been erected and it houses all plant parts and equipment.
In 2009 the city and the OEPA agreed that the city would build a EQ Basin to capture the smaller SSO’s (Sanitary Sewer Overflows) that would normally happen during small rain events due to I & I (Inflow & Infiltration) in the collection system, along with continuing to work toward the elimination of most all SSO’s. This EQ Basin can capture up to a million gallons of wastewater at this point,that would have gone directly to the receiving stream. Along with that project OEPA required that we install a backup generator at the WWTP facility to keep the treatment process running during a power outage. A 750 KWH Onan Generator powered by a Cummins Diesel Motor was installed along with current switchgear being modified to handle the switchover.
The City of Piqua received its new NPDES permit that became effective on August 1, 2011. In this permit the Ohio Environmental Protection Agency has a compliance schedule for the SSO. The major item is that by February 28, 2020 the city shall complete all work identified as necessary to eliminate the West Interceptor Sewer SSO. We are currently in design of WWTP improvements to eliminate the SSO from the system.
For more information Piqua Wastewater contact:
Piqua Wastewater Department
121 Bridge Street
Piqua OH 45356