EVANSVILLE - The Evansville Water & Sewer Utility is starting three construction projects — altogether costing $22 million — at its East and West wastewater treatment plants, both of which were built in the 1950s.
According to a news release from the city, the three projects involve:
Anaerobic digester rehabilitation ($13 million) — Eight anaerobic digester tanks, each 30 feet tall and approximately 75 feet wide, cumulatively hold 8 million gallons of anaerobic digested sludge that is converted to biosolids, methane and other gases. This project rehabilitates the digesters’ metal lids. Each of the 300,000-pound lids will be removed by 450-ton cranes so they can be cleaned, sandblasted and repainted. Two lids will be rehabbed at a time, starting at the East plant on Waterworks Road, ensuring treatment continues at normal levels. Utility officials said this rehabilitation is estimated to save approximately $250,000 a year by allowing the utility to capture the methane gas and use it as a power source.
Aeration blower rehabilitation ($5.6 million) — High-speed, industrial-sized blowers force air through the secondary aeration to speed the process of organic digestion of waste in the water. The blowers, which currently run at all times, are being replaced with ones that cycle on demand at peak times. The stainless steel pipes used to channel air to the blowers are also being moved above ground to allow crews easier access for maintenance and repairs.
New centrifuges and metal recoating ($4.2 million) — Existing belt press technology, which squeezes liquids from the sludge, is being replaced with centrifuges. The air released from the centrifuges will be processed through new filtration beds, and wood chips are being added to filter the air, greatly reducing the odor surrounding the two plants. Additionally, because sludge treatment emits an acid that deteriorates the surrounding metal structures, interior metal surfaces will be recoated to extend their functionality, utility officials said.
The East plant is on Waterworks Road and the West plant is on Tekoppel Avenue.
“Residents will notice a lot of construction at the East and West Wastewater Treatment Plants this summer,” Mayor Lloyd Winnecke said in the release. “We are making this investment to ensure our plants operate efficiently and, in the long run, reduce our operating expenses.”
The upgrades are part of the utility’s master plan. Allen Mounts, director of the utility, said authority to finance $120 million worth of sewer projects came from City Council when it approved rate increases for last year, this year and 2016.
Mounts said the three projects are being funded from a state revolving fund that enables lower interest rates than would a general revenue bond issued through the city.
“Treatment plants use complex techniques to treat the sewage, and keeping the systems working properly takes a significant investment,” Mounts said. “Our wastewater treatment plants are more than 60 years old and we want to upgrade their capabilities to maximize operations as we look to the future.”