How do a number of large food processing plants and a sensitive waterfowl habitat co-exist in a relatively small agricultural community? In Grandview, Wash., the key is the municipal wastewater treatment facility.

Treatment system supervisor David Lorenz and his team run a versatile process capable of handling the high-solids wastewater from the food industry, while recycling treated water to nearby Washington State Wildlife Department lands used by migrating ducks and geese. Biosolids from the plant are applied to area farms.

Normally, Grandview uses an oxidation ditch system to treat an average of 1.5 mgd from this central Yakima Valley community. But the facility also relies on an old lagoon system to gain extra capacity and store wastewater, and to supply water to the state lands in late winter while algae growth is dormant and before the new bird hatch commences.

Lorenz, who once farmed in the area before entering the clean-water profession 25 years ago, likes the flexibility of his operation and the positive impact it has on  the local ecosystem. He’s also proud of the facility’s industrial pretreatment program, which helps area businesses handle high solids discharges and sustain production and is heralded as one of the best in the state.

“Our process is really interesting and exciting, especially storing water and using it to enhance water quality on the state game land,” he says. “The whole facility here is really unique.”

Following the flow

Wastewater from residential and industrial customers moves through the sewer system to a lift station on the north bank of the Yakima River, the plant’s receiving stream. From there, it is pumped under the river to the south side, and then another mile to the treatment facility.

In the headworks, the flow is raised by the primary lift stations, then sampled and measured with a Magmeter flowmeter (Toshiba). The wastewater passes through a fine screen equipped with a Muffin Monster grinder and auger (JWC Environmental). Screenings are collected and taken to an area landfill.

An 80-foot-diameter clarifier is available as a bypass in case the headworks is taken offline for maintenance. Next, the alternative treatment patterns at Grandview kick in. In the most common scenario, wastewater moves from the headworks to a 500,000-gallon primary clarifier, then through a splitter box to a lift station that feeds four 230,000-gallon anoxic treatment tanks that promote phosphate removal.

After anoxic treatment, the flow is directed to a straight-ditch activated sludge system (designed by the late Larry Esvelt, a Spokane engineer). The system consists of two ditches, each powered by two rotor aerators designed to operate at 100 hp. Treated wastewater then settles in a pair of circular secondary clarifiers with mechanical brush systems that clean the sides, bottom and weirs. Lorenz reports that his team runs the ditch-clarifier systems in parallel, with a solids residence time (SRT) of 10 to 12 days in summer and as long as 18 days in winter.

A UV system (UltraTech Systems Inc.) with four chambers and 160 lights disinfects the effluent, which then passes through a Parshall flume. Some water discharges to the Yakima, while another portion is returned to the facility for various uses, including hosing and rinsing the belt press, and operation of the heat pumps in the laboratory-office building.

Grandview does not yet have a SCADA system — the team uses traditional hands-on techniques to control operations. Observes Lorenz, “I’d rather have my operators in the field recording instrument values than in a control room removed from the process.” Those operators are Rick Revard, Nick Suarez, Jeff Cochrane, Kim Endicott and Ray Rodriguez.

Big on biosolids

In accepting a large volume of food processing wastewater, the Grandview facility produces a large amount of biosolids. That’s good news to area farmers who grow wheat, corn and hops: the more biosolids, the more material to augment their soil and increase crop production.

In the treatment process, waste activated sludge from the secondary clarifiers is pumped to a holding tank and then to a belt filter press (Andritz) after polymer addition. The press yields a cake containing 17 to 18 percent solids.

After dewatering, the biosolids material travels on a serpentine belt to a truck, which transports it to a staging area where it is held for about a year. Then the solids are moved to a 177,000-square-foot asphalt drying bed area on the plant grounds. There, the biosolids are spread about an inch thick to dry out to about 95 percent solids. The process achieves about a 40 percent reduction in volatile solids and near-complete pathogen reduction.

“It’s classified as a Class B biosolids,” Lorenz says. A private firm — Natural Selection Farms — hauls it to farms, where it is incorporated into the soil. Some is used to grow corn near the plant to feed deer and other wildlife. “We have a lot of wildlife around the facility — coyotes, bobcats, pheasants, maybe some elk,” says Lorenz. “It’s almost like a private game preserve.”

Different approach

While at many treatment plants the process would end there, it doesn’t at Grandview. Old lagoons, built back in the 1970s when they provided all the treatment, give the facility extra capacity for storage and more options for discharge. They’re like having more in the cupboard, as it were. “It’s what we call a directional flow pattern,” says Lorenz. “There are 27 lagoons, about 200 acres in all. Some are aerated, some not.”

Any wastewater not treated in the biological system simply overflows into the lagoons, which can store primary-treated wastewater until periods —such as at night — when flow through the plant is reduced. Then, the stored water can be fed into the biological system for full treatment.

Or — and this is what really gets Lorenz talking and no doubt contributed to the number of awards his plant has received from the Washington State Department of Ecology — the lagoon water can be brought back into the system, disinfected, and sent some four miles to the state wildlife area.

“From the middle of February through the end of March, we pump the water to the state lands — about 50 million to 80 million gallons a year,” Lorenz says. The state land encompasses about 2,500 acres and is a prime site for migrating geese and ducks on their annual treks up and down the Pacific Flyway.

“This is the time when the algae dies off,” explains Lorenz. “It’s about a 30-day window. We supply treated water, and the state wildlife area lagoons fill to capacity and are ready when the waterfowl return in the spring.”

There are up to 10,000 hatches of waterfowl on the state land during that period. The water greatly benefits the state lands, according to Robby Sak, assistant manager of the Sunnyside Wildlife Area. “The water is pumped through HDPE pipe into our Byron Unit,” he explains. “Byron is a little like a moonscape, with salt rock outcroppings and little craters. The water fills the craters, forming small ponds that became nesting areas for waterfowl. If the weather’s right, the water will stay in the ponds until summer. Without that source, we’d be dependent upon the small amount of natural water available to us.”

Adds Lorenz, “Overall, we send more discharge to the river than to the wildlife area.” But he and his staff take pleasure in achieving something beyond treating and discharging wastewater. “While we’re limited as to what we can send them, we like sending water to the state land,” he says. He and his operators can directly witness the benefits of treatment efforts and, more important, “it lets Mother Nature take her course.”