EVANSTON — Frank Sheets, Evanston’s wastewater treatment plant manager, and Gordon Robinson, director of Public Works, recently led a fascinating tour of the plant. Sheets superior knowledge of the plant’s equipment and workings was impressive as he explained each step in the process of removing contaminants and treating the wastewater. Sheets began his career working with water pumps and then as a building inspector for Evanston. He started at Evanston’s wastewater treatment plant in 1986.

Before you flush, Sheets said, make sure you are not trying to dispose of anything down your toilet that isn’t human waste or flushable toilet paper. Products on the market that claim to be flushable may go down, but when that product reaches the wastewater treatment plant, it must be removed in order for the oxidation and biological treatment of wastewater to occur.

“I have taken a lot of classes and worked every aspect of the plant,” Sheets said. “You don’t pick this job — it picks you. Not everybody can do this job.”

In 1985, the Evanston wastewater treatment plant went online. It is located approximately 2 miles northwest of the city and serves a population of approximately 13,000 people. The wastewater comes through a gravity feedline downhill from the city.

There are four operators at the plant: Sheets, the manager, who is classified as Level IV; Kelly Morris, also Level IV; Trevor Valentine, Level III; and Daniel Sowers, Level III. The classifications are determined by experience and training and facilitated by the Wyoming Department of Environmental Quality (DEQ). Level IV is the highest certification.

The treatment plant is an oxidation ditch with activated sludge treatment. It is designed for an average daily flow of two million gallons per day (mgd) with a peak hydraulic capacity of 8.7 mgd. Sheets said the plant currently treats an average daily flow of 1.3 mgd, so there is plenty of room for growth.

Raw wastewater is lifted from the influent sewer into the treatment plant by one of three giant corkscrew-like pumps. The wastewater then flows through a mechanical step screen. Screenings (the non-biodegradable waste called “rags”) are then pressed and discarded to a bagging system for later removal to the landfill.

The wastewater then passes through a grit chamber and a flume for flow measurement. The grit, which is removed, is pumped to a cyclone and classifier and stored in an elevated hopper for later removal. This grit contains sand, small particles of rock and corn — lots of it. Corn is not digested well by humans and exits through the human system pretty much whole.

After influent flow measurements, the water enters the oxidation ditch for biological treatment. The oxidation ditch consists of four elongated ponds where the water is circulated around and around in a continuous process of aerating. After aeration in the oxidation ditch, the flow passes over an adjustable weir to one of two secondary clarifiers for solids to settle. The clarifiers are housed in dome-like structures, and only one is currently being used.

The solids are removed from the clarifiers and are returned to the influent junction box by one of three pumps and mixed with influent before returning to the oxidation ditch. The process continues until all solids are removed. The clarifier captures the waste solids, which are then removed from the process via the mixed liquid junction box prior to clarification. 

These dilute waste solids are pumped to a thickener to coagulate the sludge for easier removal. It is then transferred to an equalization tank for storage. The contents of the equalization tank are pumped to a belt press for removing the remaining water. The dewatered sludge is conveyed to an elevated hopper for disposal on an adjacent surface disposal site using a tractor and spreader.

“We monitor the clarification process twice a week to keep the system balanced,” Sheets said. “We try to create and maintain the balance so the biological action will take care of the microorganisms and natural aeration takes place. The seasons play a part in that, and winter is tougher to manage.”

After the clarification process is complete, the water flows to the UV room, where it is treated with intense ultraviolet light to kill all bacteria — each UV system has 57 ultraviolet lights inside to disinfect the water. The disinfected water is then released into Yellow Creek and from Yellow Creek, it eventually reaches the Bear River. From there, it flows to Willard Bay in Utah, and eventually ends up in the Great Salt Lake.

“We can use this water to irrigate our lawns here, and ranchers can use it for irrigation, as it is completely safe once it leaves the plant,” Sheets said. “We are committed to the quality of effluent discharged into the environment.”

The four operators collect and conduct daily testing for process control and discharge monitoring reports. They also provide plant maintenance, cleaning, janitorial and grounds maintenance. They have equipment for snow removal and summer mowing and trimming.

The plant has office space, a computer control room, a testing laboratory and showers. Operators remove their street clothes on arrival and put on their work clothes, and at end of shift, they change their clothes again.

As the plant is operated 100% with electricity, they are required by the federal government to have a backup generator in case of power outage. In that case, the generator automatically comes on and restores all power. The generator is periodically tested to make sure it works effectively.

The operators work eight-hour shifts, Monday through Friday, check and monitor equipment on weekends and are alerted through a computer system — by text, email, cellphone and a backup landline — to any problem at any time.

Over its years of operation, Evanston’s wastewater treatment plant has received several awards: the U.S. EPA Region VIII Excellence Award for operation, maintenance and management in 1988; honorable mention in 1986; and second place for the same award in 1995. In 1987, they received the WWQ & PCA Good Housekeeping Award.