Lessons Learned

A meticulous startup process built around careful hiring and effective training gets a world-class membrane bioreactor plant off to a solid start

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Anyone about to start up a brand newwastewater treatment plant would do well to talk to Bob Canham, Mike Rumke, Ray Kirkpatrick and Sam Richardson at Loudoun Water in Loudoun County, Va. They’ve learned some valuable lessons while commissioning the Broad Run Wastewater Reclamation Facility, one of the world’s largest and newest reclamation plants to use membrane bioreactors (MBRs).

Canham’s lifelong career as a consulting engineer and wastewater trainer, combined with Richardson’s, Rumke’s and Kirkpatrick’s many years in wastewater operations, resulted in a three-step process that assured success when Broad Run went through its shakedown period and opened for business in May 2008.

The keys were meticulous planning for every unit process, detailed training, and an approach to staff selection that sought team players who could generalize and become proficient at operating everything in the plant. “It was a long, drawn-out process,” says Rumke, operations supervisor. “But it was the right way to do this. I wouldn’t change it for the world.”

Says plant manager Canham, “It was the most successful startup I’ve ever been through.” The Broad Run WRF has been recognized by the American Association of Environmental Engineers as the first application of membrane bioreactors with carbon contact and UV light disinfection, and the first plant of its kind to meet stringent nutrient removal requirements.

Many barriers

Loudoun Water was created in 1959 by the Loudoun County Board of Supervisors to provide water and wastewater services to the unincorporated areas of the county.

Wastewater at the Broad Run WRF flows through an extensive series of barriers and treatment steps to make sure it is as pure as technically possible when it leaves the plant. Designed by CH2M HILL for up to 11 mgd, the plant now takes about 3.5 mgd from the eastern unincorporated areas of Loudoun County.

That is just a portion of the wastewater collected in the county — much of it is conveyed to the Blue Plains Wastewater Treatment Plant in the District of Columbia under a long-standing contract (see sidebar).

In Broad Run’s preliminary treatment stage, three 6.0-mm coarse screens (Parkson, Schreiber, and SPIRAC) remove large solids and debris. Tangential motion PISTA grit chambers (Smith & Loveless Inc.) then remove grit and sand, which is washed and compacted in a WEMCO system for disposal at the county landfill.

Next, the flow passes through primary clarifiers and then an additional set of 2.0-mm fine screens (Jones & Attwood Inc., a subsidiary of Eimco Water Technologies­). Scum is removed from the primary clarifiers with equipment from JWC Environmental and WEMCO, and a Moyno pump moves settled primary sludge to the anaerobic digestion system. Aluminum sulfate is added for phosphorus removal in the biological reactor basin.

The biological system consists of a five-stage Bardenpho process (Eimco Water Technologies), providing anaerobic, anoxic and aerobic zones, coupled with the membrane bioreactor. The plant uses a 12-train ZeeWeed 500 membrane system (GE-Zenon) submerged in separate tanks of mixed liquor pumped up from the bioreactor basins (ITT Flygt Corp. pumps).

Each membrane train is equipped with two cassettes of 48 modules each and is expandable to four cassettes per membrane train in the future. Effluent from the MBR flows by gravity to permeate tanks supplied by The Crom Corp., where it can be stored for distribution to the water reuse system, scheduled to come online in early 2010.

Or, it can be passed through granular-activated Calgon carbon contactors and a Calgon Sentinel UV disinfection system before cascading down a step-aerated effluent channel to the Broad Run waterway and ultimately the Potomac River.

Tall cylinder-shaped anaerobic digesters (The Crom Corp.) receive raw primary sludge, while waste activated sludge is thickened in GEA Westfalia separator centrifuges to about four percent solids before entering the digesters. The digesters operate in the mesophilic range (95 degrees F) and achieve an average volatile reduction of 38 percent over a 20-day period. Methane gas is recovered and used to heat the digesters and fuel boilers for plant heat. Additional Westfalia centrifuges further dewater the solids to around 21 percent for land application.

The plant effluent is of exceptional high quality. Some of the permit numbers are “real eye-openers,” remarks Canham. For example, effluent COD must be below 10 mg/l, the limit for total nitrogen is 4 mg/l, and total phosphorus must be 0.1 mg/l or lower.

No problem here, however. After a year of operation, Broad Run posted less than 5.0 mg/l of COD, 3.2 mg/l of total nitrogen without supplemental methanol, and an average phosphorus level of less than 0.05 mg/l.

Starting from scratch

Performance like this is a testimony to the viability of the Broad Run startup plan. “We started working on this plan literally years in advance,” says Canham. “We divided the plant into five groups of processes, and nine phases of operation. Working with the design engineer, contractors, vendors and our operations team, we developed a detailed plan for each.”

As an example, Canham says, the membrane manufacturer had specific requirements for mixed liquor suspended solids levels going to the membranes. “We identified procedures to start up the biological process,” he says. “We brought in seed activated sludge, and we sat down with our operations staff and the design engineer and went step-by-step, each day following the plan we had developed.”

Training was just as thorough. “We were sticklers on training,” Canham says. “The engineer provided background on each process in language that operators could comprehend. We conducted half-day classes with the design engineer and equipment vendors for nearly a year before startup. As we went along, we encouraged staff members to share something they learned each day with the others.”

Greenfield staff

Staff selection remained the critical element in operational success, because if this was a greenfield plant, it was also a green staff. Canham, Rumke, Richardson and maintenance supervisor Ray Kirkpatrick took an unusual approach.

“Everyone was new here,” explains Rumke. “We had no experienced veterans of this facility — no seniority.” Thus, the interview process was a bit like picking players for an Olympic basketball squad. “We didn’t ignore qualifications,” says Rumke, “but we were really looking for people who could work together — form a good team. We asked ourselves: Will these people work with us? What do they bring to the table?

“There were too few jobs for all the talent that applied, but in the end we hired the candidates best suited to meet the unique needs and requirements of the plant and the organization. We were able to build a strong foundation.”

The Broad Run management team also knew they needed true generalists on the staff — people who could become proficient at operating and maintaining all parts of the process. “We’re lean here, with only 12 in shift operations,” says Canham. “As it has evolved, we have our champions — people who have become subject-matter-expert at running certain sections of the plant. But everyone on staff is familiar with all the processes, from one end of the operation to the other.”

In some organizations, knowledge is power, but at Broad Run, that type of mindset is unacceptable. Sharing of expertise is the bottom line. “This is a finely-tuned machine,” says Canham. “Cross-training is essential. We can’t afford to withhold knowledge. Sharing knowledge empowers us to be successful and good stewards of our environment.”

Because the plant was brand new, the Broad Run staff had the opportunity to run the complex processes on potable water for several months before accepting wastewater. Canham compares this to a sports team’s exhibition season. The approach helped facilitate repairs and adjustments without jeopardizing performance. “It was also nice to be able to turn the flow off at night and on weekends, and turn it back on when regular hours resumed,” Kirkpatrick says.

Key lessons

When asked what other lessons were learned during the startup of this $180 million, award-winning operation, the Broad Run team members scratched their heads and claimed there were far too many to mention. But here are some key experiences:

Flow equalization. A pair of 5-million-gallon equalization tanks (The Crom Corporation) positioned after the fine screens have been crucial to maintaining consistent flows and optimum operation. “We’ve wired them into the SCADA system as part of our regular operation,” says Canham. “They were instrumental in the startup process, providing steady flows to the MBRs and assuring COD and total nitrogen removal.”

Multiple pathways. Along with the equalization tanks, the Broad Run managers feel they gained desirable flexibility through multiple drain lines, bypasses, and pathways built into the plant. This flexibility was especially helpful during startup, as it gave the staff a variety of ways to control the flow through the various unit processes.

Automation. The plant is fully automated with a state-of-the-art SCADA system (ICONICS).

Odor control. Broad Run has the latest in odor control (Twin City Fan & Blower). All structures are enclosed, and air is drawn off to a football-sized “moon-rock” biofilter (Verantis – Environmental Solutions Group, BioRem Technologies Inc.).

“It’s important that we ‘keep the lid on,’” says Canham. Doors left open or hatches not closed can cause odorous air to escape and annoy employees in the nearby administration building and visitors to the park. “We basically have to subscribe to a no-tolerance odor policy here. All our operators carry hatch-key openers, and our biofilter has done an excellent job.” The staff received only three odor complaints in the first year of operation.

Membrane cleaning. The use of alum for phosphorus removal has increased mixed liquor suspended solids, and has had an impact on membrane permeability. Rumke and Kirkpatrick have found success cleaning the membranes with a solution of sodium hypochlorite and citric acid.

Carbon essential. The Broad Run team reports that the six granular-activated carbon contactors have been essential in meeting the stringent COD and TKN effluent requirements.

With more than a year of operation now in the books, reuse of the high-quality effluent is up next. Loudoun Water is putting the purple pipes (which designate recycled water) in the ground and is looking for end-users.

“We’re starting to work with a local golf course and a few local establishments and commercial lawn owners to see if reuse is feasible,” says Rumke. Costs are a factor, and end-users need to calculate tax credits, LEED certification (for accredited green buildings), and water availability into their decision to take the reclaimed water. Loudoun Water is paying for most of the infrastructure costs. Economics aside, projections from planners are that the demand for recycled water may be greater than the supply.


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