Learning New Tricks

The staff at Marco Island makes a successful transition from an activated sludge facility to highly automated membrane bioreactor treatment

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If you grew up right-handed, it’s not easy to switch to left-handed. that’s the kindof change the operations staff at the Marco Island (Fla.) Reclaimed Water Production Facility had to make in changing from a contact-stabilization plant to membrane bioreactors two years ago.

 

“It was a challenge, to say the least,” says manager of utility operations Jeff Poteet. “It’s pretty hard to go from one mindset — activated sludge — to highly automated membrane treatment. It doesn’t run by itself. Our operators had to learn to watch for different issues.”

 

Poteet, wastewater treatment manager Jake Hepokoski, lead wastewater operator Charley Remaks, senior project manager Dr. Bruce Weinstein, and their crew have learned the new system, and it’s operating very well. That’s the result of a comprehensive training program and extra attention they’ve paid to automation and control, including the creation of a new position devoted to instrumentation and troubleshooting.

 

More water, more treatment

The big change at Marco Island was necessitated by increased flows and stricter discharge requirements. In an effort to protect the clean Gulf of Mexico waters that lap the local beaches and draw tourists and winter residents, city officials have launched a seven-year plan to phase out all septic systems (see sidebar).

 

That program was about 60 percent complete by the end of 2009, and it has only begun to increase flows. More flow will develop as the septic tank elimination program is completed and the largest parts of the expanded sewer system come online over the next two years. At the same time, the Marco Island facility had little room to expand, as it’s located alongside one of the island’s main canals and hemmed in by new commercial and residential development.

 

Combined, these factors led to the selection of the membrane bioreactor (MBR) process, which offers a high level of treatment while also saving space by eliminating conventional secondary clarifiers and tertiary filtration systems. “It was the only way to go,” says Weinstein. “It’s tight, but we’ve been able to triple our treatment capacity in the same footprint.”

The Marco Island facility is about 40 years old, and the original treatment technology has been improved and expanded in many phases since the 1970s. Until the recent process change, the plant operated as a 3.5-mgd contact-stabilization-mode activated sludge process.

 

The changeover took place in three phases. The first phase did not increase the permitted capacity, but it added the first section of the MBR process while keeping a portion of the contact-stabilization-treatment train online. The staff took a 1.0-mgd package plant and converted it to a 3.0-mgd MBR. In the second phase, additional MBR units went into operation, and the remaining contact-stabilization process was taken out of service and demolished.

 

In subsequent phases, completed in late 2009, additional MBR capacity was installed so that the facility now has four trains online to handle up to 5 mgd, plus a fifth train that provides process redundancy.

 

Watching the calendar

Construction managers had to keep a sharp eye on the calendar: They had to squeeze activity in between the rainy season (May-August) and the arrival of winter residents around the first of January. “That’s a major reason we did this upgrade and expansion in phases,” Weinstein says. “We had a finite window to get things done each season.”

 

Today, raw sewage enters the Marco Island facility through a headworks equipped with 2-mm rotary drum screens. The flow then passes to one of two equalization tanks (750,000 gallons and 500,000 gallons). Then a splitter box directs the water to twin-modified Ludzack-Ettinger (MLE) biological processes where denitrification occurs in the anoxic zone, and nitrification in the aerobic zone.

 

After biological treatment, the mixed liquor from the aeration basin feeds the four trains of a ZeeWeed membrane system supplied by GE-Zenon (a Division of GE Water & Process Technologies).

 

Each membrane tank is designed to hold six cassettes of reinforced hollow-fiber membranes with a nominal pore size of 0.04 microns. The MBR operates at a mixed liquor suspended solids (MLSS) concentration of some 8,000 to 12,000 mg/l — quite a bit higher than for conventional treatment.

 

The membrane fibers are automatically cleaned with a clean-in-place back-pulsing process that forces permeate water back through the membranes. The membranes are also aerated to scour debris from the fibers, provide mixing within the process tank, and provide oxygen for the microorganisms.

 

When necessary, in-tank chemical cleaning can be automatically performed if membrane fouling reduces permeability below a specified level. The flexible four-train system allows operators to schedule cleaning during periods of low demand with one train offline.

 

Treated effluent flows into a chlorine contact system (Odyssey Manufacturing Co.) that uses sodium hypochlorite for disinfection. Then it is pumped to two 500,000-gallon reclaimed water tanks. The produced water is used for irrigation at two golf courses, Hideaway Beach, the elementary school, condominiums, and hotels.

 

Any excess is pumped to a deepwell injection site. The facility is staffed around the clock: Teams of eight plus a chief operator work 12-hour shifts. A citywide crew of nine specialists provides maintenance. A Wonderware SCADA system controls plant processes.

 

CDM served as the consultant on this project. Dan Higgins Construction built the first phase, and Cardinal Construction is building the second and third phases.

 

A different ballgame

While the Marco Island team agrees that MBRs were the right solution, the change required special attention and training, especially in instrumentation and control. “We were used to monitoring the biological processes here, paying attention to settling in the clarifier as a measure of performance,” Remaks says.

 

“But now we monitor different parameters and have had to learn new tasks. Biology is still important, but our systems now are more mechanical. We listen to make sure the pumps sound right, and we watch the valves and compressors. We’ve had to learn what the data means.”

 

Poteet and Hepokoski explain that Marco Island team members were trained extensively in the new process and were closely involved in construction before the MBRs started up. And as the changeover to membranes neared, plant management and operations took a comprehensive orientation program that included a number of activities:

• Traveling to the membrane manufacturer’s site in Canada to view equipment as well as specific instrumentation and control sequences that would apply to the Marco Island project.

• Visiting other nearby installations that had similar membrane technology. An MBR project at Bonita Springs was being built concurrently with the Marco Island installation and provided useful information.

• Hosting an extensive training program conducted by equipment manufacturer representatives. The training sessions consisted of computer simulations, classroom exercises, and in-the-field applications. All members of the Marco Island operations staff and the utility’s maintenance team took the training.

 

It’s all about control

It didn’t stop there. Mindful of the state-of-the-art instrumentation that controls the MBR system, Marco Island created a new position in instrumentation and control and filled it with an experienced specialist.

 

“We realized that we needed a dedicated instrumentation and control person to manage the system and be able to troubleshoot alarms,” says Poteet. “Your typical operator doesn’t walk around with a laptop.”

 

Ivo Krizek fills that position. He was hired in August 2009 as senior instrumentation and control technician after a career of more than 20 years in systems integration, some of it involving pollution-control processes. “My job is to make sure the equipment is operating properly and to implement changes as necessary, citywide,” Krizek says. “My main focus has been on the new systems at the reclaimed water facility.”

 

Each of the first four MBR systems had its own dedicated equipment. “But with the fifth train, the equipment is shared,” he says. “We had to change code to do that.” Krizek works closely with instrumentation specialists from the membrane manufacturer and appreciates their help and technical support.

 

His responsibilities extend beyond the reclaimed water facility to the eight lift stations on the island and a reverse osmosis plant that treats brackish water for the water utility. “Most of our systems are connected to an Ethernet, some by fiber optics,” Krizek says. “We have PLCs scattered all over the island, running equipment and tied back into our SCADA system.”

Despite the extra effort, Poteet is happy with the results of the Marco Island project. “Overall, I’m extremely pleased,” he says. “We’ve had great support from GE-Zenon, our effluent is superb, and our staff has come a long way in the last two years.

 

“Before, we only knew activated sludge. Now we know membranes, too. I think that gives our people a leg up in wastewater operations, especially in mechanical areas.” As evidence, Hepokoski notes the passing rate for the wastewater operator certification test in Florida is about 50 percent. But recently, all three of Marco Island’s candidates passed it on the first try.



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