Most lifelong residents of North Platte, Nebraska, don’t know where the wastewater treatment plant is. That’s exactly how Doug Meyer, superintendent, wants it: “It means we’re doing our job.”

Producing effluent cleaner than the receiving water pushes the five operators to their limit. The last upgrade split the screening stations, creating a temperamental treatment train. Recommended changes from consultants took months to evaluate and barely improved conditions. After three years of trying it their way, Meyer threw up his hands and told his operators, “Make it run.”

They did. It took time to learn the plant as it went through the seasons, but the operators mastered the correct formulas. In 2017, the Nebraska Water Environment Association gave the plant a Best-in-Class Award for medium-sized facilities (2 to 5 mgd) and, for the ninth consecutive year, the Scott Wilber Outstanding Facility Award for excellent operations and maintenance.

Extended aeration

Built in 1965 and upgraded in 1994 and 2007, the 4 mgd (design) activated sludge plant averages 3.23 mgd from 24,000 residents. Some 100 miles of sewers and 11 lift stations deliver wastewater to the wet well. The headworks includes a mechanically cleaned bar screen (Parkson Corp.) and vortex grit chamber (Smith & Loveless).

A splitter box directs influent to the north and south extended aeration basins, each with three 20-foot-wide concentric channels. From there, the flow enters two 666,000-gallon clarifiers. Three 40 hp hydrofoil pumps from Weir Specialty Pumps (WEMCO) deliver return activated sludge through the drum screens (Parkson Corp.). The 3 to 5 tons of inorganic materials trapped weekly ensure trash-free land-applied biosolids.

Screened RAS returns to the aeration basins or is pumped to two sidestream interchange tanks, each holding 540,000 gallons. Operators work on the north tank one day and the south tank the next. Tanks are decanted to the aeration basins. The liquid sludge is mixed with polymer (ChemTreat). Some 3,800 pounds of sludge flow daily to a Klampress eight-roller belt press (Alfa Laval). The resulting cake at 14 to 16 percent solids then dries in a bed. The facility produces 370 dry tons of biosolids annually.

Effluent from the clarifiers travels in a trough to a chamber that directs the flow to two parallel UV disinfection channels, each with two rows of 30-lamp modules (Glasco Ultraviolet). The water is discharged to the North Platte River. Tom Carson does most in-house laboratory testing; a contract laboratory handles required certified tests.

Environmental protector

Meyer, a Grade 4 (highest) wastewater operator and Grade 1 (highest) and Grade 6 (backflow prevention) water operator, was the plant’s chief operator before advancing to his current position in January 2016. He has worked 24 of his 26 years with the city in the Wastewater Department, gaining valuable historical knowledge.

The plant, on the city’s east edge between the North and South Platte rivers, once boasted the largest lagoon system in the state, with two 10-acre aerated cells and four contained settling ponds totaling 280 acres. Each river is 2 miles from the facility. During the planning stage for the mechanical plant, the city wanted to convert the lagoon acreage to an industrial park.

“North Platte is developing in our direction, and this is valuable real estate,” Meyer says. “I had to fight to keep two total retention ponds by reminding city officials that they protect the rivers from hazardous spills. The next emergency is always out there.” The ponds stayed, and that decision was vindicated in 2006.

“We were constructing the current plant and using the ponds to hold influent,” Meyer says. “One day, we saw oil at the headworks.” Investigation found that the oil had come from a nearby railroad classification yard. Within an hour, the railroad’s hazmat crew had strung a containment boom across the first pond and was skimming oil.

Oil wasn’t the only threat. In 2013, 13 million gallons of floodwaters hit the plant, overwhelming its maximum capacity of 8.8 million gallons. “We split the flow, sending half for treatment and half to the ponds,” Meyer says. Three fine-bubble Aire-O2 aerators (Aeration Industries International) aerate the first pond.

Operational challenges

Emergencies aside, the 11-year-old facility presents various challenges. Plant chemistry is one of them. “We knew we should be seeing better numbers in our final effluent,” Meyer says. He reminded the team to take notes, then turned them loose to find the answers.

Over three years, they switched aeration discs on and off (each channel has a dozen 54-inch-diameter discs) and adjusted the volume of RAS, the amount wasted, and the sludge levels in the clarifiers and interchange tanks. “Today, we’re kicking out numbers better than we could have imagined,” Meyer says. Monthly averages are 3.1 mg/L BOD and 5 mg/L TSS.

Spring brings outbreaks of filamentous bacteria. Instead of feeding a chemical to control the foam, operators increase the speed of the aeration discs and adjust RAS volumes. “My guys know what to watch for and when to act,” Meyer says. “I can’t say enough good things about them.”

Ready for action

The plant’s Grade 2 wastewater operators include Carson, Eric Farritor and Tyson Geisler. Adam Anderson joined the team 18 months ago. Sam Trent, maintenance worker, was employed part time until Meyer created the full-time position in October 2017. None shirk responsibilities or getting dirty.

One project involved digging for a 4-foot-diameter lift station 5 feet deep and installing a 14 hp pump (Sulzer Pumps Solutions) from a decommissioned lift station. Throughout winter, the pump sends 700,000 gpd to the first pond to increase the level, keeping both ponds from drying out in summer. “We try to pump when the UV lights aren’t on,” Meyer says. “Disinfection is required from May through September because the North Platte River is considered recreational.”

Occasionally, help comes from outside the plant. An ongoing project by Tom Werblow, city engineer, is benefiting operators. To date, Werblow has eliminated five lift stations installed in the 1960s and 1970s. Some were unnecessary, others had chronic conditions, and some were too small to handle flows from a new development.

Rather than build a larger station, Meyer and Werblow devised a solution. In 2002, the city built a 2,600 gpm lift station to serve a massive travel and truck stop south of Interstate 80. The plan is to eliminate two undersized lift stations, gravity-flow the sewage to the 2002 station, and pump it to the plant. “We’re looking forward to implementation because consolidation reduces maintenance and frees operators,” Meyer says. 

Strong support

Sometimes repairs or upgrades are beyond the operators’ expertise. That includes curing wave action through the treatment train. Influent collects in the wet well before three 40 hp pumps from Weir Specialty Pumps (WEMCO) deliver it to the plant. “We hired HOA Solutions, who installed our SCADA system, to mount variable-frequency drives on the pumps,” Meyer says. “My guys are bragging how well they equalized the flow.”

The operators enjoy strong support from Jim Hawks, city administrator, and other officials: “They trust us to do what needs to be done and are involved in every project,” Meyer says. “If my guys need special tools, Jim never argues about their purchase. He knows we’re saving the city tens of thousands of dollars by keeping work in-house.”

The operators also participate in yard art. Over the years, they installed underground sprinklers in the 40,000-square-foot front yard, put up an outdoor sign board and planted a flower bed around it. In 2014, they added steps, laid stone, and planted grass around the headworks building.

Last year, they erected a flagpole. A 26-foot galvanized steel streetlight pole had been hit in an accident. The operators cut off the dented bottom, topped the pole with an eagle, and set it in an area they landscaped with stone and bushes. Meyer says, “Their pride of ownership is outstanding.”

Answering the call

Operators at the North Platte Wastewater Treatment Facility routinely take on projects, but replacing a 1,000-pound drum screen exceeded their job description. Without a monorail crane, they had no way to lift and move the elevated drum to an overhead garage door for extraction. “We called the local crane service, but the crane head was too large for the job,” says Doug Meyer, superintendent.

A friend suggested a local outdoor advertising company. The head of their boom was small enough to telescope through the garage door and hook onto the drum screen, provided it was closer to the opening. The ball was back in the operators’ court.

“Safety was paramount,” Meyer says. “The job had the potential to turn ugly fast.” His solution ran flat-eye slings under the 12-foot-long drum. Then Meyer slid pipes through the eyes and positioned five men per side to distribute the weight. Working like pallbearers, they carried the drum 6 feet to within range of the boom.

“The boom operator telescoped back out of the building with the screen, set it in our dump truck, hooked onto the replacement, and lifted it into the building,” Meyer says. “Then we rigged the slings underneath the drum and carried it home.”

Plans are in place for when the second screen needs to be removed. “The upgrade splits our screening at the headworks, not out in the middle of the plant,” Meyer says. “This is one project we won’t be doing.”