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Appleton Utilities Department: Commingling Water and Energy while Enhancing Quality of Life
When the city of Appleton, Wis., was incorporated in 1857, the population was just above 2,000 residents and natural water abounded in local rivers and streams. Within a few short years though, the population was competing with commercial industries for access to water and the community mobilized to form a city water works system in 1881. Today, the Appleton Utilities Department (AUD) provides essential water and wastewater treatment services to industrial, commercial and residential customers with state-of-the-art facilities.
Appleton Mayor, Tim Hanna, prides himself on providing essential services to the community while maintaining the highest standards. In 2007, the Hanna had initiated a goal of reducing the city’s energy use by 10 percent. “We have achieved that goal from projects and developing energy awareness,” says Dean Gazza, director of city facilities in Appleton. Automated heating and cooling controls, lighting improvements and projects at the AUD have allowed the utility to substantially reduce its operating costs. Above all, the city’s goal is to mobilize its talented professionals and develop strategies to account for the community’s future needs, while preserving the environment. At both of the utility’s water treatment and wastewater treatment plants, AUD operates with integrity, responsibility and economy.
The original water treatment plant was constructed in 1912, but subsequent upgrades and renovations couldn’t keep up with growing demand. Because of the facility’s age and a need to meet water quality standards, the city completed construction on a brand new 24 million gallon per day surface water filtration facility in 2001. The plant’s construction allowed Appleton continued access to the safest drinking water possible and included a state-of-the-art lime softening technology and a low pressure, ultra filtration membrane process. The ultra filtration process, at the time of construction, was the largest system of its kind in the United States.
“2012 will mark the 100-year anniversary of our water treatment plant, but we’ll be celebrating just by making the plant more efficient,” says Chris Shaw, director of public utilities at AUD. In the last 20 years, Shaw has worked his way through a number of positions at the department and takes pride in helping the AUD team identify major areas to increase efficiency. In the case of its water treatment plant, the team recently began running some of its pumping operations off-peak to save the utility and the taxpayers an estimated $40,000 annually.
Wastewater Treatment, Turning Poop into Power
Grit removal and primary treatment processes remove suspended solids, then wastewater is sent to the aeration tanks where it is aerated so microbes can gorge on thousands of pounds of waste.
The aeration process is the most energy intensive process within a wastewater treatment plant. A wastewater treatment plant itself can be a community’s largest electrical user and the aeration process can account for 50 percent of an electrical bill. When the AUD team began planning to replace its old aeration equipment, the timing seemed perfect to find a system to supplement its energy needs.
“One of the old blower units had to be replaced, and we’re always looking for ways to offset our operation and maintenance costs on any project,” says Shaw. AUD installed a top-of-the-line unit from Turblex Inc. which has been shown to increase the aeration process’ efficiency by up to 40 percent.
Simultaneously, the AUD team installed a system to reuse the methane gas produced in the digestion process. “Ours is not a conventional system. The two digestion tanks hold 2.2 million gallons per tank and are shaped like eggs or hot air balloons,” jokes Shaw. In the process the microbes convert 10,000 pounds of waste into water, methane and carbon dioxide. These microbes are temperature sensitive so, to keep them alive, the tanks have to be kept at 95 degrees Fahrenheit all year round, which in itself involves a considerable amount of energy.
“Currently these microbes digest enough to produce between 150,000 to 200,000 cubic feet of gas,” explains Shaw. Ultimately, the two systems provide enough energy to heat the wastewater treatment facilities and offset the thermal demand of the digestion tanks significantly.
Waste Worth its Weight
As a public utility, AUD looks to make changes across its entire operation that save money and conserve resources. Utilities, in general, are struggling to find ways to properly manage their biosolids, which is the final solid product from a wastewater plant. Appleton produces over 20,000 wet tons of biosolids annually. In turn, AUD developed a system to treat the biosolids and provide them to farmers as fertilizer for no cost. The major glitch in the program is that Wisconsin’s winters are too cold to land-apply the biosolids to agricultural fields during winter months. Instead, AUD constructed a facility that can store a six month supply of processed and treated biosolids.
Once the weather warms up, the biosolids can be applied to the land to provide essential nutrients for farming. In particular, AUD’s biosolids are rich in calcium, nitrogen, phosphorous and potassium, with smaller quantities of copper, zinc and iron. The calcium content is a byproduct of the lime-softening process at the water treatment plant and can help farmers raise the pH of soil, promote better root establishment and decrease the use of commercial fertilizers overall.
There aren’t many industries that haven’t been affected by the economic downturn and AUD shuffled its resources around to adjust accordingly. Instead of planning ahead for more capital investment projects, the team is refocusing on operating the facilities as efficiently as possible and only making investments to directly support those efforts. Regardless of the economic climate, AUD has served the people of Appleton for more than 100 years and the team at Appleton Utilities Department will continue to strategize new ways of providing safe, clean water and sewage services for years to come.