Teaming With Technology

The staff in Commerce Township, Mich., uses old-fashioned persistence and ingenuity to make the most of a new BNR process with SCADA control.
Teaming With Technology

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In 2004, plagued by filamentous growth that threatened performance, the operators of the Commerce Township (Mich.) Wastewater Treatment Plant devised a makeshift chlorine dosing system using 55-gallon drums and manual measurement to get the plant back into compliance.

"The staff really stepped up," recalls Chris Coffey, who recently retired as superintendent and is now a consultant to the plant. "I've never been more proud of a group of guys. They worked around the clock for two weeks. It's an example of what this staff is willing to do."

That sense of dedication has helped the Commerce Township facility win Peak Performance Awards from the National Association of Clean Water Agencies (NACWA) for eight consecutive years, and is essential today as the plant adapts to a new biological nutrient removal system started up in 2010.

"Our overall concern is how we serve our clients," says Greg Knauf, who took over as superintendent last year. "We do whatever we can to maintain water quality standards and keep our customers happy."

Coffey adds, "Wastewater treatment is really about making changes to find and maintain the environment that allows the treatment process to work. It's attention to detail and it comes from our supervision on down through our staff."

Tough on nutrients

The plant is operated by the Oakland County Water Resources Commissioner's Office, which facilitates regional cooperation in infrastructure, environment and water quality and also operates the Walled Lake-Novi Wastewater Treatment Plant in Oakland County. The Commerce plant serves 29,000 people in Commerce Township and several neighboring communities. While design capacity is 8.5 mgd, the average daily flow is just under 2.0 mgd.

Wastewater is collected through a sprawling network of pressure and gravity-flow sewers and grinder stations. It flows into the plant through Ovivo screens and into a PISTA grit removal system (Smith & Loveless).

From there, the water moves on to Ovivo Carrousel oxidation ditches and clarifiers for biological treatment and nutrient removal. The system uses rotor aerators and includes anaerobic and anoxic zones that enable the plant to meet stringent limits for phosphorus and nitrogen. These high standards (less than 0.2 mg/L P and 0.5 mg/L NH3) are driven by the sensitive nature of the receiving stream and the presence of the endangered redside dace minnow.

After biological treatment, disc filters (Aqua-Aerobic Systems) further reduce suspended solids, and a UV unit (Siemens Water Technologies) disinfects the flow. Effluent discharges to a tributary of the Seeley Drain, which ultimately flows into the Rouge River.

Biosolids are stored and thickened by a belt press (Ashbrook) that delivers cake at about 15 percent solids. Outside contractors' trucks haul the cake to a landfill. The operation has neighbors close to the fence line, so the new system includes packed tower odor scrubbers. Two units are located in the headworks building, and another serves the solids processing area.

An elaborate SCADA system provides precise process control and off-site monitoring and response. "The system provides many benefits," says Knauf. "It's a hybrid system integrated by a local firm, Commerce Controls. It gives us information we never had before."

The remote alarm and operation capability also saves money. "Before, we couldn't make changes without sending an operator on a two-hour call out to the site," says Knauf. Now, operators can make changes remotely via laptop computers.

An on-site laboratory handles operational samples only. Reportable numbers are run at the Walled Lake-Novi treatment facility.

Big improvement

The upgraded plant offers several improvements over the previous operation, in the eyes of Knauf and Coffey. For one thing, the selector zones in the BNR system have eliminated filamentous growth. With the collections system spread out over several communities, and population only a little more than a third what the system is designed for, septicity and hydrogen sulfide in the influent wastewater promote undesirable bacteria.

Coffey notes that the team became skilled at dealing with filamentous growth back in 2004, with help from Dan Holmquist and Doug Hill of the Michigan Department of Environmental Quality. So far, there have been no such issues with the new system.

The SCADA control system gets high marks, as well. "For example, we once got a call at 3 a.m. showing a high level in the influent wet well," says Knauf. "We then had an instrumentation failure, causing all the pumps to turn on and push solids out of the clarifier. The laptop controls we have now sure would have been a big help then."

Coffey observes, "SCADA is something we really needed. It has made an unbelievable difference in response time and control over the process." In the old plant, the aerators were either off or on at a high or low setting. That promoted over-aeration and wasted energy.

"It drove DO levels way beyond what they needed to be," says Coffey. "Now we can keep DO at levels necessary to nitrify, by setting the desired DO level in the SCADA system, and the system then uses variable-frequency drives to ramp the rotor speed up or down."

Enhanced processes

Soda ash is another thing of the past. Before the BNR system, the plant would nitrify and use up alkalinity. "We'd get significant swings in alkalinity and pH," Coffey says. "Operation wasn't as stable as we would have liked. So we started using soda ash to maintain the proper pH in the mixed liquor. We did that for six or seven years, adding soda ash on a daily basis."

Today, the BNR process stabilizes alkalinity. "We don't have to lug bags of soda ash out to the system anymore," says Knauf.

Increased sludge storage capacity is another positive. "We used to rely on a rotary drum thickener to prepare the biosolids before land application," Knauf says. "We had 500,000 gallons of storage capacity — not a lot of flexibility there. We could get up to our eyeballs in solids."

Obviously, that had implications on the treatment process, since the plant wasted up to 50,000 gallons of solids daily to maintain the proper cell residence time (CRT). The new solids handling train includes a second (redundant) belt press, which can be brought into service if solids volume warrants it.

Knauf and Coffey say the old plant ran well, but was nearing its hydraulic and organic loading capacity. "Our capacity was around 2.4 mgd, and we were running at 1.7 to 1.8 mgd," says Coffey. "We had no emergency fallback, no place to divert any excess flow."

CRT-driven

Some things don't change, even with a new process. In the case of Commerce Township, it's the operational team's approach to good performance. "Consistency is the key to effective wastewater treatment," Coffey says. "You'll be successful if you establish a good environment for your process and then keep it the same."

He and Knauf say the run of NACWA awards is due in large measure to the plant staff finding the right environment for the bugs to thrive. Their team members are Assistant Superintendent Adam Hopper; operators II Mike Severs, Tom Wood, Mike Gibbons and Isaiah Johnson; and operator I John Aitken.

The team worked diligently to find the best food-to-mass ratio and the best CRT to maintain. "We developed spreadsheets that allowed our operators to establish consistency and achieve the same ratios every day," Knauf says.

After experimentation, a food-to-mass ratio of around 0.1 and a CRT of around 20 days seemed to yield the best treatment performance. "Our operators monitor the solids content in mixed liquor samples every day and plug it into the spreadsheet," says Coffey. "That allows us to dial in the gallons of solids to waste every day. Once we're dialed in, we see good, consistent numbers on a daily basis."

Different hats

All the operators and managers at the Commerce Township treatment plant are involved in monitoring and control because this is a jack-of-all-trades shop. "We all wear different hats," says Knauf. "We don't have different sections or staffs. Everybody does what needs to be done — lab work, maintenance, troubleshooting."

There's both a drive for perfection and for problem-solving, as evidenced by a recent operator solution to a grease issue with the belt presses. "The grease fittings were hard to get to," Knauf says. "So our operators devised a new system, running remote grease lines to the fittings.

But they did it like a professional would — neatly, not messy with lines running all over the place. It looks good. We treat the place like it's our own. We're not only concerned with performance, but also how the place looks."



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