John Lande remembers a time when he AND his staff didn’t enjoy going to work. In the late 1990s, a new permit imposed chlorine, ammonia and metals limits on the City of Monroe (Wash.) Wastewater Treatment Plant that the fixed-film rotating biological contactor (RBC) process just couldn’t meet.

For a few years, until completion of a new activated sludge process in 2002, work life was a daily struggle to get into compliance.

“We tried all kinds of ideas and all kinds of methods,” says Lande, plant manager and a Class IV operator. “And although those efforts did make things better, they weren’t enough to get us under the limits. It wore on us. It wore on our morale, it wore on each other. It was bothersome that we couldn’t be successful in our work.”

What a difference a few years can make. In 2004, two years after the new process went online, the plant received the first of its three Outstanding Performance Awards from the state Department of Ecology. “After years of writing red circles on our monthly Discharge Monitoring Reports, to go a 12-month cycle without a permit violation — we were very proud of that,” says Lande. “We threw that plaque up on the wall right away.”

The pride from that first award persists today as Lande and a long-tenured team work together to keep on improving, solve treatment challenges in-house when possible, and produce the best possible effluent for discharge to the Skykomish River.

Road to recovery

The plant (2.84 mgd design, 1.5 mgd average) serves a western Washington community of 16,000, plus 2,000 prisoners and staff at the Washington State Reformatory. Lande, with Monroe for 17 years, leads a team made up of plant supervisor Donovan Sheppard, (Class IV, 12 years), lab analyst/pretreatment coordinator Linda Gleason (Class IV, 16 years), and operators Theresa Davis (Class III, 10 years), Jim Tobacco (Class IV, 7 years), José Agudelo (Class IV, 4 years) and Randy Oesch (Class II, 11 years).

The plant was built in 1954 with primary treatment and upgraded in 1976 with secondary treatment using the RBC process. A 1995 upgrade expanded the secondary process, added primary clarification, and increased aerobic digestion. The 2002 upgrade replaced the RBCs with a modified Ludzack Ettinger (MLE) activated sludge process, added secondary clarification, and replaced chlorine disinfection with UV.

The plant’s compliance issues began in 1995 when the Department of Ecology imposed new limits on ammonia, chlorine, copper, mercury and zinc. “When that permit was issued, the treatment plant we had wasn’t really in position to be in compliance,” recalls Lande. “We were disinfecting with chlorine, but we didn’t have dechlorination facilities. The copper limit on effluent was below what came out of our citizens’ taps, and with the RBC plant, we couldn’t nitrify year-round to meet the ammonia limits. As a consequence, we had monthly violations that went on for some time.

“The first thing we did was take out chlorine disinfection and put in UV. The problem was that although the UV system resolved the chlorine issue, the RBCs could not meet the water-quality criteria that would make the UV systems successful. We couldn’t provide the transmittance level of 60 percent that was necessary. So we traded one effluent problem for another.

“In 1997, we went into engineering to design the activated sludge facility, which would provide the effluent quality needed for UV disinfection and also would nitrify, and so resolve the ammonia issue we were having. Along the way, in 2001, the city received notice from an environmental group, Waste Action project, of its intent to sue for Clean Water Act violations.”

Back on track

Now, the plant consistently complies with its permit, in part because the Department of Ecology removed the ammonia, copper and zinc limits after a mixing zone study showed they were unnecessary, but mainly because the new treatment process is highly effective.

Wastewater enters a wet well from which a series of Crane Deming influent pumps lift it to the headworks. It passes through a Parkson Monoscreen elliptical step screen and then goes to an aerated grit chamber and primary clarification.

The activated sludge process uses Hoffman/Lamson centrifugal aeration blowers and fine-bubble diffusers (ITT Water & Wastewater). Hach instruments and a Hach sc1000 control unit monitor and regulate dissolved oxygen, pH and ORP in the MLE process. From aeration, the water flows to two Enviroquip secondary clarifiers (Ovivo). The secondary effluent passes through three Aquionics 8000 in-vessel medium-pressure UV disinfection systems.

Discharge is by gravity, except that an effluent pump station is used in times of high river flows or high treatment plant flows, which usually coincide.

On the solids side, Gorman-Rupp pumps move return and waste activated sludge. The primary and waste activated sludge are anaerobically digested and dewatered to about 16 percent solids in an Ashbrook 1.5-meter belt press. Until 2009, the city composted its biosolids, but by then, according to Lande, the cost of sawdust “priced us out of composting operations.” Now the Class B material is carried by a contract hauler for application to wheat fields.

Nitrify anyway

Although the ammonia limit in the permit has been removed, Monroe uses the MLE process, which reduces effluent ammonia levels.

“We take aeration basin effluent, which is relatively high in nitrate from the nitrification in the process, and pump that back to the head of the basins to our anoxic selectors,” says Lande.

“That nitrate, in the anoxic environment, allows denitrification to occur. We operate this mode primarily to recover alkalinity and so maintain the pH of the system. If we did not recover that alkalinity, the nitrification that occurs in the basins would drop the alkalinity to where our pH could fall below the level our microbes need to live, and our effluent pH would drop below our permit limits.”

The staged selector is a compartment at the head of the aeration basin where no air is introduced to it. Certain bacteria, in the absence of dissolved oxygen, utilize the oxygen from the nitrate, and release it as nitrogen gas. “We feel this process makes the plant more stable and helps us produce a better effluent,” Lande says.

Always ingenious

Since the 2002 plant upgrade stabilized the treatment process, staff morale has been high. Plant supervisor Sheppard observes, “For the most part we’re local people. We like working for the community. The city of Monroe is a good employer, and the benefit package is competitive. Overall, it’s just a good place to work.

“We have a great mix of people from different backgrounds. Operator José Agudelo comes from Colombia. We have a range of ages. I’m the youngest at 33, and it goes up to Jim Tobacco, at 63. We’re all different, but we enjoy each other’s company and like to come to work and see each other.”

Lande, meanwhile, sees his job as “treating the water to the finest level, and doing it safely and efficiently. There’s a lot to that. We ask a lot of the folks who work here. I try to give them an environment where they can be successful.

“We’ve done a lot of things to make the plant run better. Our group does a really good job in identifying and addressing problems. If they see that they’re spending too much time doing one thing or another, they’re going to let me know, and we’re going to try to come up with a solution. We try to tweak things and make our efforts show in that clean water coming out the end of the pipe. We all understand the importance of clean water, and that’s our drive.”

Creative solutions

In 1995, the staff observed that the self-cleaning bar screen in the headworks was too coarse and was allowing materials to pass through and cause issues in downstream processes. “We looked at that and said, ‘We really need to improve this,’” Lande recalls. “So we took it on internally, without outside engineering.

“We went through the procurement process and purchased the two Parkson step screens we have today, with the conveyor systems and the screw wash press. Our own staff took out the old screens and installed the new equipment. That was a rewarding project, and just one of several that we’ve done.”

Another involved concrete deteriorating on a secondary clarifier launder, exposing the aggregate. Algae then accumulated and the staff spent excessive time brushing and cleaning the weirs. “One thing I ask of my group is to have really clean clarifiers, so they look nice when visitors come, or even when I stick my head out and look at the water coming over the weir,” says Lande.

“Two summers ago, we applied a Tnemec product that was like a grout over the exposed aggregate. Then we put a two-part finish over it. For two years, it has been quite resilient and has remedied the man-hours we used to spend keeping our clarifiers clean.”

In another case, after installation of the belt press, the staff experienced repeated failures in a double-diaphragm sludge pump that fed the press. “We had to speed that pump up to meet the capacities required for the press, and we were blowing diaphragms, seals and gaskets on almost a weekly basis,” Lande recalls. The solution was to install a new seepex progressive cavity sludge pump.

More changes coming

For 2011, the Monroe team was looking at more improvements, including a new headworks with step screens, submersible influent pumps, and a vortex grit system with accompanying classifier. Also planned was a switch to a low-pressure, high-intensity in-vessel UV disinfection system to increase flow capacity and enhance energy efficiency.

For their constant efforts to improve, team members have been rewarded with additional Department of Ecology Outstanding Performance Awards in 2006 and 2009.

“This isn’t just a job to us,” says Lande. “The recognition was a long time coming. For those who lived through all the struggles when we were having compliance problems, it has been very gratifying.”