Cleveland-area plant receives Envision Silver award for sustainable infrastructure
- Name: Southerly Wastewater Treatment Plant
- Location: Cuyahoga Heights, Ohio
- Size: 120 mgd
- Infrastructure: Renewable energy facility, primary settling tanks, sludge spiral lift pumps
The Northeast Ohio Regional Sewer District (NEORSD) plays host to three wastewater treatment facilities that service the greater Cleveland area. While each fulfills its necessary function, the largest of the collection is the Southerly Wastewater Treatment Plant located in Cuyahoga Heights, Ohio.
The plant initially became operational in 1927, and has demonstrated a consistent history of upgrading operations, with significant upgrades made in 1930, 1938, 1955 and the early 1960s. However, the facility did not fall under the control of NEORSD until 1972. Soon thereafter, in 1974, the plant underwent its largest rehabilitation, touting nearly $400 million in investments.
Producing an average daily flow of 120 million gal per day, the Southerly Plant is among the largest of its kind in the U.S. and is responsible for servicing a population of more than 530,000. Sprawled across a 288-acre plot of land, the plant was recently awarded the Envision Silver award for sustainable infrastructure by the Institute for Sustainable Infrastructure (ISI).
Ordinarily, ISI would apply its system to plants undergoing planning and design stages for infrastructure upgrades, but a pilot initiative was implemented in the case of the Southerly Plant for which ISI verified operations well into the plant’s life, considering the environmental, social and economic impacts the plant has had on its region. The Southerly Plant is now the oldest infrastructure project to be verified by the Envision infrastructure rating system.
The incinerator used in the renewable energy facility incinerates sludge, septage and grease.
With consideration to the Envision system verification criteria, the economic, social and environmental impacts of the plant are many.
Southerly is responsible for roughly 70% of total employment in Cuyahoga Heights, providing work for approximately 200 employees, making the plant a massive economic touchstones for the village.
The plant also provides internal training and education to its workers for career advancement, while also offering tuition assistance and maintenance and operator programs to foster the growth of its hometown. NEORSD also offers outside workshops to local citizens who are curious to learn about about water quality, sewage and sustainability, including both historical and future practices.
Environmentally, the plant recently made significant strides. In 2014, the plant successfully completed construction of a renewable energy facility (REF) that incinerates sludge, septage and grease from all three NEORSD plants to generate energy. This, along with phasing out the plant’s biosolids thermal conditioning System, will allow for a reduction of natural gas consumption by 137 million cu ft per year.
Outflow releases effluent into Lake Erie.
All NEORSD treatment facilities utilize similar treatment operations for the wastewater that runs through its various systems. Specifically, in the case of the Southerly Plant, the operation implements an activated sludge process, specialized bacteria, filtration and disinfection.
Upon arrival at the facility, the wastewater goes through the preliminary screening process during which bar rakes remove large debris to be sent to landfills. The water then moves through a detritor tank where a collector arm slowly removes heavy inorganic material from the water.
The water then proceeds to the primary treatment process, first undergoing further removal of heavy organic material in primary settling tanks. Chain flights remove solids and grease from the water by skimming the top of the surface and bottom of the tank continuously. Grease and skimmings are mixed together to eventually be incinerated in the plant’s REF.
Next, the water is put through the secondary process involving the activated sludge process. Air diffusers inject compressed air into the flow, which then moves to the final settling tank, where the remainder of organic material is collected at the bottom of the tank and returned into the process. The plant also uses specialized bacteria in order to remove ammonia and nitrogen from the flow, as well as spiral lift pumps for sludge.
Finally, the effluent moves to chlorine contact tanks for disinfection. Sodium hypochlorite is introduced into the effluent and is allowed the proper time to kill any remaining pathogens.
Sodium bisulfite is then added to neutralize the hypochlorite, rendering the effluent ready for reintroduction to Lake Erie.