Membrane News: Tonka Water’s Fountain Hills Facility Featured in WE&T Magazine
A recent Tonka Water wastewater treatment plant was featured in WE&T magazine highlighting a recent project in Fountain Hills, AZ. This plant was struggling with aging microfiltration membranes and experiencing pitting and leaks. A new ultrafiltration system by Tonka Water increased capacity and reduced backwash and maintenance needs.
Problem: An aging microfiltration system experienced pitting and leaks.
Solution: A new ultrafiltration system increased capacity and reduced backwash and maintenance needs.
When the Fountain Hills (Ariz.) Sanitary District advanced water treatment facility went into operation in 2001, its design life was expected to be 10 years. So in 2013, it came as no surprise that the facility’s microfiltration system began experiencing problems that required regular maintenance.
“It gave us 12 years of reliable service,” said district manager Ron Huber, “but we had started to be burdened by pitting and leaking in the system’s stainless steel piping. While we were looking at the costs of workable replacements for the piping and related valves and instrumentation, considering each separately, Tonka Water [Minneapolis] developed a proposal for a complete system.”
The new system also included an upgrade to ultrafiltration from microfiltration and automation of cycles for clean-in-place and chemically enhanced backwash.
The district chose the replacement ultrafiltration system. Upgrading to ultrafiltration technology helped the district end a troublesome maintenance burden, provided it with redundancy, and enabled its qualification for a higher-capacity aquifer protection permit.
Water flows to the advanced water treatment facility after passing through the district ‘s water resource recovery facility (WRRF).
The district needs to meet the requirements of an Aquifer Protection Permit from the Arizona Department of Environmental Quality that includes maximum contaminant limits for nutrients, organics, inorganics, turbidity, and fecal coliform. The permit also regulates water elevation levels in recharge and monitor wells, and requires maintaining the integrity of various treatment facility components, compliance with aquifer water quality standards, and demonstration of best available demonstrated control technology.
Customizing an ultrafiltration system
Tonka Water was “open to adapting their product,” as well as revising their original proposal to work with the design and plans of district staff and consultants, Carollo Engineers (Walnut Creek, Calif.) , said Clark A. Moskop, operations manager for the district’s WRRF.
“Tonka’s support for programming integration and controls was extremely helpful,” said Boyce Clock, facility lead for operator-communications.
The installation process for the complete system, which also includes chemically enhanced backwash, succeeded within 5 months and allowed uninterrupted seasonal aquifer storage and recovery (ASR) of reclaimed water in the advanced facility’s five ASR wells.
“The timing for this project was crucial,” said Huber, referring to the installation window of May 31 through Oct. 1 in 2013. “We had to be sure we could continue to put reclaimed water in the ground when we needed to. Our staff, consulting engineer, contractor, UF system manufacturer, and their rep were all in unison to make it work. We were back to recharging on time, and up and running.”
MGC Constructors Inc. (Phoenix) worked with Tonka Water to keep the demolition of the former equipment and the installation of the new ultrafiltration units on track, which included providing all system components and ancillary pieces, all within the same footprint, Moskop said.
Technology offers automated high performance
Tonka Water’s ultrafiltration systems are automated fully, with Internet-based control systems that provide online factory support in real-time. The company offers complete system capability, including full system control to eliminate fragmented responsibility. Pressurized water passes onto a membrane in a dead-end flow configuration, resulting in a membrane effluent. Designs enable continuous removal of contaminants while minimizing fouling, which allows operating for long periods between cleanings. The pressure-driven purification process tor aquifer recharge includes automated backwashing strainers with 130-µm protection and is designed to preserve integrity and long-term capacity of injection wells. It also minimizes the need for chlorine treatment and can serve as pretreatment for future nanotiltration, reverse osmosis, ion exchange, or other add-ons that might be needed to meet future requirements.
The facility received three membrane trains. Each train includes 54 modules with advanced control features . The system can operate with any number of trains in service and still backwash effectively. It also can handle a wide range of flows without sacrificing finished water quality.
The modules incorporate advanced ultrafiltration membrane technology from Dow™ (Edina, Minn.). They include double-walled “outside-in” hollow fiber and can be isolated individually for repairs in-place. They are designed to provide effluent turbidity quality of less than 0.1 NTU; remove such pathogens as Giardia, Cryptosporidium, viruses, and Escherichia coli; and provide superior resistance to membrane fouling and chemical attack.
New operation improves performance
The advanced facility’s new ultrafiltration system features 0.03-µm membranes – reduced from 0.1 µm. The five ASR wells provide recharging and recovery of reclaimed water. The district now builds recharge credits with the Arizona Department of Environmental Quality and has a current maximum volume of annual aquifer withdrawal at 2.8 million m3 (2240 ac-ft).
In addition, the district reports significant reduction of backwash/reject water to sewer and retreatment. Originally the system produced backwash/reject water amounting to 10% to 15% of average daily flow, or about 946,250 Lid (250,000 gal/d). With the ultrafiltration system, the advanced facility produces backwash/reject water that’s 5% to 6% of average daily flow, or about 378,500 Lid (100,000 gal/d).
“Whatever backwash water we produce in the [advanced facility] has to be conveyed back to the [WRRF] for complete retreatment, and then pumped back to the [advanced facility], so we’ve gained very significant savings there,” he said.
“In addition to relieving the manual burden for [clean-in-place cycles], we also gained improvement in frequency,” Huber said. “What had taken us 6 to 9 hours per rack every month and a half is now an automated process once every 6 months or longer,” Huber said.