by Dennis Dalman
editor@thenewsleaders.com
Wastewater-sewage treatment – so often out of sight, out of mind – is now once again on the radar of the Sartell City Council and other councils in the greater St. Cloud area.
At a recent council meeting, two employees of the St. Cloud Wastewater Treatment facility presented an overview of the treatment process. The two presenters were Pat Shea of Sartell, public-services director; and Tracy O’Dell of Becker, assistant public-utilities director.
Sartell is one of the five cities surrounding St. Cloud that pays, through contract, money to be part of the St. Cloud treatment plant. The other city members – besides St. Cloud – are St. Joseph, Sauk Rapids, St. Augusta and Waite Park. Each city must share in the costs of operating the plant itself, as well as the cost of pipes, lift stations and related costs to get wastewater piped to the St. Cloud treatment plant, which is located in St. Augusta near the New Flyer manufacturing firm.
For its share of the water-treatment service, Sartell pays anywhere from $600,000 to $650,000 per year, said Sartell Administrator/Financial Director Mary Degiovanni. Those costs vary depending on operational costs for the plant, as well as how much total sewage is piped specifically from Sartell annually to the plant. Each member city pays only for its specific costs. For example, St. Joseph’s sewage pipes connecting to the plant do not affect Sartell’s part in the overall plan, so Sartell and the other cities would not be charged for such city-specific needs and vice versa.
The member cities will be asked to help pay for a project that will be undertaken within the next two years – an innovative solution being worked out as to how the plant will use solid-waste products that remain after the treatment process. Sartell’s share of that cost will be an estimated $400,000. Degiovanni noted the project is being timed, so when it begins, Sartell’s sewer-debt service will have dropped down, thus reducing impacts of the new charge on the city budget.
The new project, estimated to cost about $23 million, is a way for the treatment plant to create fertilizer pellets and to commercially distribute them for use in agriculture, lawns, greenhouses, landscaping and other uses. The plan also calls for other innovative uses for the by-products of waste-water treatment.
For years – and currently – treated solids from the plant’s process are spread on farm fields. The solid waste that remains after water has been treated and released is treated by heat and monitored for bacteria and viruses before it’s allowed to be used on fields.
In a recent interview with the Sartell-St. Stephen Newsleader, Shea said the program to develop innovative ways to process the solid waste, including the fertilizer pellets, will be up and running by autumn of 2019 at the latest.
History
The St. Cloud Wastewater Treatment Facility began operation in 1976, owned and operated by the City of St. Cloud, with contract agreements from the other five cities in the area.
Before the new plant was built, sewage was treated at a plant that was built in 1956 located south of the St. Cloud State University campus. Before 1956, raw sewage – untreated – was dumped right into the Mississippi River.
The federal 1972 Clean Water Act allowed the use of federal funds to help cities build treatment plants, including the one in St. Cloud. The St. Cloud facility has received at least a dozen major awards for pollution prevention and energy management in its 40-year history.
The WWTF was designed to process 13-million gallons of wastewater-sewage per day generated by nearly 100,000 residents of the greater St. Cloud area.
Between 2010 and 2013, there was a massive expansion program at the wastewater plant, which cost $48 million – the costliest public project in St. Cloud history. The member cities all chipped in to pay for that project.
The sewer rate charges for Sartell are $6.03 per 1,000 gallons of wastewater piped to the St. Cloud plant.
O’Dell explained to the council the ongoing operations necessary to keep the plant functional: the lift station constructed near the St. Cloud Country Club in 1974, a bypass system installed, repairs or replacement of huge valves that are very expensive to buy, generator replacements and upkeep of the four huge pumps at the lift station.
Last year, an energy-efficiency program was completed, which saved enormous amounts of money. It involved using on-site bio-gas as fuel, LED lighting and generators run by biofuels. In 2013, the plant used 6.5-million kilowatt-hours of electricity. In 2016, thanks to energy-saving efforts, that was down to 5.2-million kilowatt-hours. That is expected to decrease to 300,000 kilowatt-hours in 2018.
How it works
Wastewater treatment involves five steps: preliminary treatment, primary treatment, secondary treatment, final clarification of the water and solids processing.
In Step One, most of the wastewater flows to the main lift station, and that station pumps the water to the treatment facility.
In Step Two, primary separation involves the separation of liquids and solids by using four huge rectangular tanks in which solids settle out of the water.
In Step Three, a process removes suspended solids, dissolved solids, nutrients and metals. The system is a continuous flow and a biological process in which micro-organisms use the organic material in the wastewater as an energy source. Also during the process, organic matter is reduced to carbon dioxide and water.
In Step Four, solids are allowed again to settle out in a final clarification process. A portion of the solids is used for “seed” and recycled back to the activated solids process. The remaining solids are further processed. The liquid portion is disinfected by exposure to ultraviolet light and then discharged into the Mississippi River.
In Step Five, solids are generated in two stages during wastewater treatment of primary and secondary steps. The solids are mixed together and residual water removed from them. The liquid is returned to the beginning of the treatment process, and the solids portion is sent to an anaerobic digester. During that digestion process, the solids are heated and mixed for a minimum of 15 days. That process produces liquid, gas and solids. The liquid is returned again for treatment; the gas is used to heat the digestion process; and the solids (called “biosolids”) can then be applied on farm lands.
That latter process is what will be largely changed, with new options (such as the fertilizer pellets) in the new solids program that will begin in autumn 2019.
This is a bird’s-eye view of the St. Cloud Wastewater Treatment Facility, located in St. Augusta. Five member cities pipe wastewater to the plant and chip in to pay for the process.
