From The Mountain Mail (Casey Kelly):
City staff led residents through Salida’s largest capital improvement project to date, the Wastewater Treatment Plant, during an open house Thursday [August 15]. Salida Wastewater Treatment Plant Manager Randy Sack led about 37 residents through the plant for the first tour of the day, explaining the process that raw sewage takes through the plant to become clean, disinfected water.
Raw sewage enters the facility in the pretreatment area of the plant’s west side. The sewage is run through a bar screen to separate inorganic and organic material and sent to the primary treatment area. In primary treatment, the waste is run through the plant’s clarifier to be separated. Heavy organic materials sink to the bottom and are sent to the anaerobic digester, while the liquids are sent to the secondary treatment area.
In the secondary treatment area, the sewage flows into the Integrated Fixed-film Activated Sludge (IFAS) system, which removes ammonia nitrogen and suspended solids with the help of bacteria in the IFAS system.
After the IFAS system, the water is run through a second clarifier to further separate the materials. Organic material is sent to the anaerobic digester, and liquids are sent to tertiary treatment.
In tertiary treatment, the liquids are run through disk filters to remove any remaining organic material, and the water is then passed under ultraviolet light to kill any remaining bacteria or viruses before flowing out into the Arkansas River.
Organic materials removed from the sewage during the process are taken to the anaerobic digester, where bacteria break down the material into gases, biosolids and water. The biosolids are removed and sent to processing, and the gas is captured and used to heat the facility.
In biosolid processing, the solids are laid out to dry, decompose and sanitize for 1 year. After a year, the facility offers the material free of charge to the public for use as fertilizer.
The new plant has improved the plant’s ability to filter out gases and solids from the water that is drained into the Arkansas River. The outgoing water now meets Environmental Protection Agency regulations that weren’t met prior to the plant’s upgrade.
For instance, the plant has seen a 99.9-percent reduction in ammonia nitrogen in outgoing water, from 27.6 milligrams per liter in 2012 to 0.008 milligrams per liter in July. The EPA maximum limit for ammonia nitrogen is 18 milligrams per liter. The plant has seen a 91-percent decrease in the amount of “suspended solids” in water sent from the plant into the river, from 40 milligrams per liter in 2012 to 3.5 milligrams per liter in July. The EPA maximum limit for suspended solids is 30 milligrams per liter.
More from the article:
Wastewater Treatment Plant finances
• Total cost of the project: $17.6 million.
• How it’s being financed: a $12.1 million loan from the U.S. Department of Agriculture, a $1.35 million Department of Local Affairs grant (with matching funds from the city) and a $2.6 million USDA loan the city received in 2009.
• Terms/rates: 40-year term at an interest rate of 2.5 percent.
• How it’s being paid for: City Administrator Dara MacDonald said in April when the city adjusted sewer rates, it was done in anticipation of the facility upgrade and the debt service that would come along with it. She said then that revenue from the city’s sewer enterprise fund is projected to cover the cost of the annual payments, along with the plant’s operation and annual maintenance costs.
• Annual payments: The city is required to make a minimum payment of $480,405 each year, but it can make higher payments to lower the amount of total interest paid over the life of the loan. If the city makes only the minimum payments, it will pay $7.1 million in interest over the life of the loan.
City Finance Director Jan Schmidt suggested at a February city council meeting that the city make payments of $542,844, which assumed the previous higher interest rate, which would have the city paying off the loan 8 years earlier and saving nearly $2.5 million in interest. Council will decide each year during the annual budget process whether to pay the minimum or the higher annual payment. She said the city is scheduled to make its first annual payment of $542,844 in September.
More wastewater coverage here.