Plans to more than double the capacity of the Zeeland Clean Water Plant, to allow it to accept wastewater from Zeeland and Holland townships, remained stalled for 15 years while the city of Zeeland and the two neighboring communities negotiated a wastewater treatment contract. The ongoing delays eventually caused challenges for the existing 1.65 million gallons per day (mgd) facility to maintain efficient aeration system control. The plant needed a solution for its outdated manually operated system, which combined with inadequate mixing capabilities, resulted in over-aeration and wasted energy.
In 2016, plans to expand and upgrade the plant finally moved forward, and the city resolved its aeration system challenges with the Xylem Sanitaire CASPERSON activated sludge solution process, which allowed the plant to eliminate the use of lime to treat waste and drastically reduced the volume of biosolid residuals, a main goal of the plant from the beginning of the process. However, this was only the first of several issues the city encountered in the massive project to expand the Zeeland Clean Water Plant from 1.65 mgd to 3.5 mgd.
Overcoming challenges gives way to improvement
Originally built in 1915, the 100-year-old facility was last upgraded in 2009, according to Doug Engelsman, superintendent for the Zeeland Clean Water Plant. The city had experienced years of wear and tear on plant equipment, resulting in frequent problems in every area of the plant except for the headworks. Before embarking on the plant expansion and equipment upgrades, the city decided to map out its goals to determine the solution that best fit the facility’s needs.
After reviewing the issues, the city set several goals to help overcome those challenges. Primarily, the plant needed to implement upgrades that would enable better control of the treatment process to improve total nitrogen and phosphorus removal and reduce energy and chemical consumption along with reducing wear on the blower.
In order to achieve these goals, the city hired engineering firm Moore & Bruggink, which in turn engaged water solutions provider Xylem Inc. Together, the two companies developed a complete solution to double the plant’s existing average flow to 3.5 mgd. The expanded flow enabled Zeeland and Holland townships to become wholesale sewer customers.
New biological treatment process reduces need for chemicals
The Sanitaire CASPERSON solution included updates for the Zeeland Clean Water Plant, such as aeration systems for the aerobic tanks and a digester, six Flygt 4410 mixers and two Flygt 4630 mixers. The solution also included new blowers, air control valves, air flow meters and fiberglass baffle walls.
As part of the CASPERSON aeration system solution, the Zeeland Clean Water Plant also implemented an OSCAR performance optimizer control system with dissolved oxygen (DO), ammonium, nitrate and phosphate control.
The biological process eliminates the need for the polymer and alum the Zeeland Clean Water Plant previously used as part of its treatment process.
“Any time chemicals are reduced, it is a win for the receiving waters and biosolids disposal program,” said Engelsman.
Not only does the aeration system solution allow the Zeeland Clean Water Plant to have a process that is environmentally friendly, it also reduces the overall amount of electricity used by the community.
The Zeeland Clean Water Plant today
Now, the Zeeland Clean Water Plant has five primary tanks, eight aeration tanks with CASPERSON, the biological nutrient removal system, five final clarifiers, an ultraviolet disinfection system building, a RAS blower building, a laboratory building addition, two aerobic digesters, an odor control system and new integrated OSCAR and SCADA controls.
The adoption of online instrumentation has dramatically increased the DO measurement functionality. Modern online instruments are capable of measurements at a frequency, accuracy and reliability suitable for process control at a reasonable cost. Strict control of DO is required in order to create the conditions necessary to achieve biological removal of nitrogen and phosphorous.
The OSCAR control system automatically controls the blower speed operations, which helps the Zeeland Clean Water Plant to improve total nitrogen removal and reduced energy consumption and wear on the blower. Additionally, the controller optimizes the process for biological phosphorus removal, resulting in effluent total phosphorus concentrations consistently below 1 mg/l with minimal to no chemical addition.
Overall, the new automation controls have not only increased plant efficiency, but they have also improved process performance, minimized energy consumption and chemical usage throughout the plant. The city of Zeeland is saving an estimated $24,500 per year as a result of ongoing monitoring of plant processes.
Since it began operation, the digester aeration system has considerably reduced the total volume of biosolids residuals to be processed. At a 30% volatile suspended solids (VSS) reduction, 342,210 pounds of solids no longer need to be disposed of per year. In turn, improved VSS destruction means less lime is needed to stabilize the biosolids. The plant has realized a savings of $47,000 per year in lime costs, as well as a $20,000 per year decrease in biosolids hauling costs.
Automated controls also allow more efficient use of staff at the plant. The ability to remotely control parts of the facility minimizes the need to access the system both hands-on or come in during the day or night to resolve problems.
Overall, the expansion allows the Zeeland Clean Water Plant to receive and treat an additional 1.1 million gallons of wastewater per day from Zeeland and Holland townships. On a daily basis, 2.2 million gallons of wastewater now flows through the plant.
Ultimately, the plant expansion project has helped the city of Zeeland realize its goals of more efficient plant operation, resulting in a positive impact on the environment and achieving energy savings of more than $22,000 per year.
About the Author: Dennis J. Barnes is a process engineering manager for Xylem. For more information, visit www.xylem.com.