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Resiliency: Water treatment plant uses innovative technology to protect local ecosystem

In 2016, the Zeeland Clean Water Plant in Michigan moved forward with plans to double its capacity from 1.6 million gallons per day (MGD) to over 3 million MGD. The utility saw the expansion as an opportunity to upgrade aging equipment with innovative, more sustainable approaches, including solutions from Xylem’s Sanitaire, Flygt and YSI brands.

Expanding capacity and removing nutrients more sustainably
 
Maintaining efficient aeration was a key challenge for the treatment plant. In wastewater treatment, bacteria are used to biodegrade waste and nutrients. The right levels of oxygen are needed in the wastewater to ensure the bacteria can do their job, but aerating the water is energy intensive. The Zeeland plant had been manually operating their aeration system, which when combined with inadequate mixing capabilities, resulted in over-aeration and wasted energy.
 
In order to meet these challenges, the city contracted with Moore & Bruggink to provide construction engineering services for a major upgrade to the clean water plant. They engaged Xylem to design a complete Sanitaire CASPERON solution. CASPERON is an activated sludge process that eliminates the use of lime and the volume of bio solids. It includes Sanitaire Silver Series II membrane disc diffusers,, aeration systems for the aerobic tanks and a digester, six Flygt 4410 mixers and two Flygt 4630 mixers.   
 
As part of the CASPERON solution, the Zeeland Clean Water Plant was also upgraded with a Sanitaire OSCAR performance optimizer control software and hardware system, with dissolved oxygen (DO), ammonium, nitrate and phosphate control, which is used with Xylem’s treatment equipment to help a plant meet its desired performance and operating budget goals[1].
 
The CASPERON solution also enables the Zeeland Clean Water Plant to have a treatment process that is environmentally-friendly and saves the community electricity costs.
 
Adding automation
 
The expansion project included automation of the aeration system to increase efficiency. The adoption of online instrumentation has dramatically increased the dissolved oxygen 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 dissolved oxygen (DO)is required in order to create the conditions necessary to achieve biological removal of nitrogen and phosphorus. Adding automation at the Zeeland facility has improved process performance, and minimized energy consumption and chemical usage throughout the plant. Ongoing monitoring of plant processes has resulted in estimated cost savings of $24,500 per year for the City of Zeeland.
 
To support real-time monitoring and control, YSI IQ SensorNet instruments were installed in the basins, including dissolved oxygen probes and VARiON ion selective electrode sensors, which measure ammonium, nitrate and potassium. The sensor control zones take readings and speed up or slow down the removal process to maintain optimum oxygen levels.
 
Now, plant staff can remotely control significant parts of the facility minimizing the need to access the system hands-on or come in during the night to address a problem. They can also monitor energy usage and identify conservation efforts.
 
Advancing environmentally-friendly impact
 
With the new installed solutions, 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. Now, 2.2 million gallons of wastewater flow through the plant daily.
 
Due to the OSCAR control system, which automatically controls blower speed and operation and maintains stable dissolved oxygen concentration, the plant has experienced improved total nitrogen removal and reduced energy consumption and wear on the blower. In addition 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.
 
Since it began operation in 2017, the digester aeration system has also delivered significant energy savings of more than $22,000 per year and considerably reduced the total volume of biosolids residuals to be processed. At a 30 percent Volatile Suspended Solids reduction, that equates to 342,210 lbs. of solids per year that no longer need disposal, which in turn has reduced the amount of lime 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 compared to its previous system.
 
Aside from energy efficiency, Zeeland Clean Water Plant superintendent Doug Engelsman said more precise aeration control has resulted in more efficient use of staff. The installation of reliable, efficient equipment also has improved the quality of the effluent and provided a major reduction in chemical use.
 
To read the original case study. 
 
Read Xylem’s 2019 Sustainability Report

[1] https://www.xylem.com/en-us/products-services/treatment-products-systems/monitoring-control-equipment/biological-treatment-monitoring--control-systems/oscar-process-performance-optimizer-v2