By Mayor Charles â€œPheezeâ€ Kemper and Gene Hinshaw, P.E.; as reported by Veronica Salmons
Investing in a wastewater treatment system is often more necessity than choice for community leaders. Whether it\'s brought on by regulatory requirement, growth, or a failing existing system; there is no choice but to expend resources in order to meet the latest needs of the system.
But community leaders do have a choice in the results of that expenditure. When looking towards the future, it\'s often a choice of frugal building for now or investing in progressive building for later.
The City of Troy, Mo., faced that decision recently. Located about 50 miles outside of St. Louis, the City has experienced phenomenal growth over the last fifteen years that made building a new plant an absolute necessity. The City chose to invest in membrane bioreactor (MBR) technology as a way to head off future system changes and regulatory issues. This article will explore the new technology while following the City\'s decision-making process in choosing MBR over less costly, more traditional treatment processes.
The MBR Process
Membrane bioreactor treatment for wastewater is a relatively new concept in the United States. While the technology has been utilized overseas for more than two decades, only a small number of MBR facilities are in operation in the US today.
MBR treatment costs more than traditional wastewater treatment processes, but delivers remarkable effluent quality and the ability to meet almost any discharge limit. Membrane bioreactor treatment relies on familiar methods of screening and biological treatment; then the membranes filter out unwanted particles of an incredibly small scale. The result is high quality effluent that can be used for non-potable applications, or discharged to almost any receiving body of water.
As more communities face new facilities and upgrades with tightening NPDES permit restrictions, it\'s likely that MBR will become a treatment of choice. In addition to the achievable effluent quality, membrane bioreactor systems can offer smaller footprint areas, a somewhat simplified treatment process, and relatively easy add-on capacity for the future.
Choosing MBR over Traditional Treatment
The City of Troy facility was built to discharge into the Cuivre River. The river itself is part of Cuivre River State Park, which boasts fishing, swimming and boating as major attractions. Naturally, effluent that discharges into such a recreational area is subject to public and regulatory scrutiny.
In 1999, the City\'s traditional 1.3 million gallon per day (MGD) wastewater facility was reaching 80% capacity. Community leaders had recognized the need for a second plant years earlier, but had taken the planning process slowly. But in the early 2000\'s, there was no more time to waitâ€”the City hit a major building boom. There were very real fears that progress could be halted because of the lack of capacity at the single existing plant. In fact, at one point the City was required to report building permits to DNR on a regular basis.
Speed was a crucial factor by the time the actual decision making process began. Meanwhile, the Missouri Department of Natural Resources, in response to an US Environmental Protection Agency mandate, was in the process of analyzing Missouri waterways to determine impaired status. The City needed to plan for effluent limitations, and there was no time left to wait and see what restrictions the new permit might impose. Given all of these factors, the City Council decided a proactive approach was best. They made a point of building the new facility to meet foreseeable current and future permit levels using the best available technology on the market.
Planning the Solution
Consulting engineering firm Trabue, Hansen & Hinshaw, Inc. (THH) presented membrane bioreactor technology as the answer. More traditional treatment processes were also considered but all were eventually rejected. After studying cost basis vs. expected effluent limitations that could be achieved, it was clear that MBR was the way to address all of the City\'s concerns.
City leaders including council members, the city administrator, public works director, and water operator joined THH professionals on a research trip to explore an MBR system in operation in Atlanta, Ga. The team was impressed by what they saw as an efficient, compact and achievable operation. MBR operations closer to Troy were also toured, although those operations consisted of smaller, limited-use plants that did not compare to the 1 MGD municipal usage that the City was aiming for. In fact, the new treatment facility in Troy is currently the largest-capacity membrane bioreactor plant in the State of Missouri.
Financing the Solution
When preliminary budget numbers were announced for the new plant and substantial collection system improvements, there were worries that the $11 million dollar price tag would be difficult to meet. But the City found an answer in certificates of participation (COP). The certificatesâ€”financing in which an investor buys a share of lease revenues from an agreement made by a government entityâ€”allowed the City to use proceeds to build the treatment facility.
To secure the COP, tap fees for both residential and commercial building permits were raised from $500 to $4,000. Research in surrounding communities showed that the new $4,000 fee was on par with area trends. One advantage to the COP over a traditional bond arrangement is that long-time city residents are not affected by the tap fee increaseâ€”but can still enjoy advantages of growth allowed by the new treatment plant. Other than rate changes in conjunction with scheduled fee studies, basic sewer rates have not changed.
At press time, total costs have come in under the $11 million dollar estimate. The City will use any remaining monies for related expenses, such as building and repairing new trunk lines, and fixing inflow and infiltration issues in the â€œoldâ€ plant\'s collection system.
Bringing Builders on Board
Tap fees would obviously have an effect on builders and area developers. So the City once again got proactive; approaching builders and developers from the start in order to head off negative effects with positive communication. Troy officials met with members of the local builder\'s association to inform them of the new fee structure, as well as share advantages that the new treatment facility provides for the builders themselves, including no more worries about building permit limitations, closer connection lines to many areas under construction, and an environmentally sound treatment process.
It helped, too, that the City already had an excellent relationship with the local builder\'s association. The two groups had met about various issues in the past, and had worked out their differences amicably. Since the rise in tap-on fees, building permit numbers have slowed down somewhat but continue to be steady.
The City also took pains to keep the â€œordinaryâ€ citizen informed. Mayor Charles â€œPheezeâ€ Kemper visited regularly with local groups including Rotary and Kiwanis to give progress updates during planning, construction, and startup of the new facility. And the local paper helped keep citizens informed with regular articles about the project. In the end, the new treatment facility passed through City Council with only a modest amount of criticism from the public.
Choosing an MBR System
Vendors of membrane bioreactor systems each offer a unique MBR process of their own. These differences mean it\'s important to decide on a vendor even before planning facility construction. The City of Troy addressed this by structuring a two-part bidding process for the treatment plant project; the first for vendor selection, and a second phase for actual plant planning and construction.
Three MBR vendors were invited to bid on the Troy project. All three gave a formal proposal and presentation to City officials, as well as offering access to operators, owners and users of systems around the US utilizing their particular system. Potential vendors were â€œgradedâ€ on a points system in order to determine the winning proposal.
City and THH officials paid particular attention to each vendor\'s installation experience, operations and maintenance factors, and post start-up support program. After considering all the factors, the City chose Enviroquip, Inc. in partnership with Kubota Corporation. Enviroquip representatives then became team members for the building design phase of the project.
MBR System Start-Up
Start-up issues with the new plant were minimal. Of course, there were a few kinks in the system to be worked out; including some low-flow issues that are present because the plant was designed for population growth that is not yet contributing to system flow.
THH officials point out that the overall challenge with membrane system design is to spend more time on treatment before waste materials reach the membranes in order to prevent fouling, or an undesirable build-up of particles on the membrane material that causes the system to need cleaning. This includes attention to headworks design (such as screen sizing) and other measures to remove larger particles that may interfere with the membrane\'s ability to filter out the tiniest microorganisms.
The best indicator of the plant\'s success is in the quality of the effluent, which has proven exceptional. The City contracts with operations and maintenance contractor Alliance Water Resources to operate the new facility as well as the â€œold,â€ traditional wastewater plant.
Knowing that growth can come more quickly than expected, Troy officials made sure to build in plans for relatively quick and convenient expansion. Key system components were sized up for future tie-ins of additional membrane units. Those components will allow the plant to more easily upsize when the time comes.
Troy leaders anticipated the need for a new wastewater treatment facility with years to plan ahead. But they caution other community leaders not to fall into the trap of too much planning and not enough action. In particular, City officials recommend a comprehensive plan of action that considers all community systems, rather than focusing on only one particular need. Financing and population growth factors are crucial in this planning.
THH representatives credit planning ahead to include advanced training from the vendor as crucial to the success of the project. This trainingâ€”at both off-site training locations and on-site after start-upâ€”should go above and beyond the standard offered in many vendor contracts. The vendor may also offer remote support options for ongoing support: for example, Enviroquip representatives can tap into the City\'s SCADA system to help trouble shoot issues from their offices in Austin, Tex.
The City of Troy is proud of their state-of-the-art treatment facility and is planning an open house for spring 2007. City officials made a choice that is forward-looking, environmentally conscious, and sets their City apart. And by investing now in treatment technology that will meet expectations well into the future, the choice of MBR treatment may prove to be the best financial option in the long run.
Charles â€œPheezeâ€ Kemper is mayor of The City of Troy, Mo. He can be contacted at Troy City Hall, 636.528.4712.
Gene R. Hinshaw, P.E., is president of Trabue, Hansen and Hinshaw in Columbia, Mo. He can be contacted at firstname.lastname@example.org.
Veronica Salmons is marketing coordinator for Alliance Water Resources, Inc. She can be contacted at email@example.com, or 573.874.8080.