Raising the Standards
The city of Klamath Falls will soon have one of the most innovative, "green" industrial facilities in North America, thanks to a creative new approach in wastewater and cogeneration technology. This south-central Oregon municipality is busy completing a new 500 mw cogen plant (which is a facility that has one source of fuel and generates two forms of energy, i.e. electricity and steam). It is upgrading the 4.3 million gallons a day (average dry weather flow) city wastewater treatment plant (WWTP) and extending a geothermal water loop to heat the WWTP control building, melt sidewalk snow and provide back-up heat for the digester.
Many believe the project includes such a wide array of environmentally mitigating approaches that it will serve as an example for years to come. Briefly, these approaches include:
"Green" Aspects of the Project
- Using treated WWTP effluent as cooling water for the cogen plant;
- Evaporating more than 65 percent of the effluent from the cogen plant, significantly reducing discharge into the Klamath River;
- Removing chlorine and reducing temperature of cogen cooling system blowdown prior to discharge into the Klamath River;
- Diverting steam from the cogen plant to several local industries, which will reduce their need to fire their own boilers, decrease overall costs to local industries and reduce area pollution;
- Including a geothermal loop to heat parts of the WWTP; and
- Improving stormwater treatment by replacing an aboveground storm sewer with an aesthetically pleasing vegetated treatment swale (low area of land).
Reuse of the WWTP effluent is now essentially and ultimately a revenue generator, because profits from the power sales will eventually come back to the city.
All and provide electricity to energy-starved California and the Northwest - enough electricity for the equivalent of 400,000 homes.
Klamath Falls city officials chose two expert international companies to manage the project: PacifiCorp Power Marketing Inc. (PPM) for the $300 million plus cogen plant, and Brown and Caldwell for the WWTP reliability upgrades. PPM formed a project-specific limited liability company - Pacific Klamath Energy LLC, which in turn is managing the main design, supply and construction contract with the joint venture of Black & Veatch and Jones Construction (BVJ). For the WWTP construction project, the city hired a company with extensive construction experience in the Northwest - IMCO General Construction.
Groundbreaking for the cogen plant occurred in June 1999, and the upgrade to the WWTP began in JMay 2000. The WWTP work is complete, and at press time the cogen plant was scheduled to go online in July of 2001. The City will own the plant and it will be operated and maintained by Pacific Klamath Energy LLC.
According to City Manager Jeff Ball, the city was approached by Pacific Power in the late 1970s to explore the possibility of a hydro project. But that didn't work out - especially not after the nearby Klamath River was declared a wild and scenic river by the then Secretary of the Interior, Bruce Babbitt. After environmental regulations in the 1980s reshuffled the local economic deck, this once-prosperous logging town found itself mired in no-growth and double-digit unemployment. "We needed to do something to help pull the city out of its problem, so we initiated an 'Operation Bootstrap,' " related Ball.
By the mid 1990s the idea for a cogen plant began to develop, and the state set conditions for one 500 mw plant to be built in Oregon. A beauty contest among three contestants, the major issue was which project had the best environmental mitigation package.
City Manager Keller's philosophy was simple: Talk first, design second. Negotiate and resolve the issues before the project is set, and then design the plant.
In the end, the Klamath Falls proposal won the endorsement of Oregon's Energy Facility Siting Council (EFSC). The certificate to build was received in late 1997 with final amendments accepted in 1998. Perhaps just as importantly, the project gained the support of several key environmental groups.
City Manager Jim Keller's strategy was clear -- get everyone on board in the beginning. Take the time to build consensus. "We understood that we would have to design a project that would gain the approval of local and regional environmental groups," he said, "so we sat down with them early on and sought their input. Many of the environmentalists were very good to work with."
Keller's philosophy was simple: Talk first, design second. Negotiate and resolve the issues before the project is set, and then design the plant. "There needs to be economic and environmental checks and balances," he said. In this project, we decided that we did not want to spend our money in court, but instead spend it on working with industry and environmentalists to find solutions."
With this approach, Keller helped lay the foundation for a project that could succeed long-term - partly because he had done his homework, partly because he refused to cut corners. The cogen plant at Klamath Falls, as he envisioned it, would "raise the bar technologically and environmentally."
The plant is being financed by revenues from a city-sponsored $300 million bond. These bonds were purchased primarily by institutional investors. This allowed the city to use private money to build a large public project that would provide opportunities for many private businesses, while generating energy for local and West Coast businesses.
Q and A
The cogen plant is incorporating state-of-the-art equipment throughout the facility. Bill Byrnes, site construction manager for PPM's subsidiary Pacific Klamath Energy (representing the owner) and veteran of many power and industrial projects, explained that construction challenges in projects this size can begin early. "The site is zoned for industrial use," he said, "and formerly this location was a log yard for the Weyerhaeuser mill, which is now Collins Products. When the excavator, LTM Inc of Medford, began digging, he had to cut as far down as 20 to 30 feet to hit a workable base. He removed approximately 200,000 cubic yards that were filled with bark and wood debris."
The new advanced combined-cycle cogeneration plant will use two gas turbines that will each produce 165 megawatts of power. The hot exhaust gases go from the turbines to two heat recovery steam generators (HRSG) which power the ALSTOM (formerly ABB) steam turbine. This combined cycle will produce net power at a very low heat rate - less than 7000 British thermal units per kilowatt hour, HHV basis. Some steam will be sold and piped to other industrial users in the industrial park.
For this project, the boilers were so large they had to be assembled on-site. Each of the three turbines required 1,000 cubic yards of concrete for the base since the site is located in a seismic zone. The total cubic yards of concrete used was over 18,000.
Next to the cogen plant is the large electrical switchyard, which connects to an existing 500 kilovolts line less than a mile away. The evaporative cooling tower system consists of eight cells and will evaporate 65 percent of the effluent.
The WWTP will provide the cogen plant with an estimated 2.8 to 4.2 million gallons a day in cooling water with over 65 percent of the water being evaporated in the cooling towers.
There were many unique aspects to this project; one of the more unusual involved extending the city's geothermal heat loop. "The city uses the 180 degree natural geothermal water to heat many of its buildings, sidewalks and even some of the downtown businesses," IMCO's Project Manager,Todd Vasey explained. "In this project, the city wanted to extend the geothermal loop to provide space heating to the WWTP's control building as well as provide a reliable backup heat source to the digesters. The plan for routing the geothermal pipe even included a number of plant sidewalks to melt the snow. " In addition, all geothermal work and the construction upgrade to the WWTP had to be accomplished while the treatment plant was operating 100 percent of the time.
Engineers from both the WWTP and the cogen plant worked closely together to produce a WWTP effluent that met the cooling water quality needs. The effluent was super-chlorinated to kill the algae and the process was modified to remove phosphorus. Effluent turbidity monitoring was added to provide immediate indication if the effluent quality deteriorated.
Other significant improvements included:
- Complete redesign of an existing complete-mix aeration basin to provide multiple treatment options including plug-flow, step-feed, sludge re-aeration, nitrification-denitrification and biological nutriment removal (BNR);
- Design and construction of a new 110-foot diameter secondary clarifier with the existing clarifier to be used as back up; and
- Waste activated sludge pumping and metering to a new dissolved air floatation thickener.
The WWTP will provide the cogen plant with an estimated 2.8 to 4.2 million gallons a day in cooling water with over 65 percent of the water being evaporated in the cooling towers. The remainder of the water, called the blowdown, is returned to the WWTP where it is dechlorinated and reduced in temperature prior to its discharge into the Klamath River.
"This recycling of the WWTP effluent through the cogen does two things," commented Vasey. "One, it alleviates the dependency of the cogen plant to use freshwater in its cooling process. And secondly, the evaporation process reduces the amount of discharge going into the river by approximately 2.3 million gallons per day."
And that's not all. Added to this, reuse of the effluent is now essentially and ultimately a revenue generator because profits from the power sales will eventually come back to the city. In addition, profit from the steam sales will go to supporting the on-going maintenance, operation and expansion of the City's geothermal system, which will include over 100 offices and buildings.
Scheduling has been a critical element, as well, since the cogen plant depends on the WWTP. Because the cogen plant is dependent on the cooling water from the treatment plant, a back-up system for the plant's processes had to be designed and built. This meant redundancy in all the major components -- more pumps, storage, chlorination capabilities and greater operational flexibility. Water had to be flowing to the cogen plant by November 1, 2000.
"Even with all the unique design and construction issues in this innovative project, change orders were less than one percent of the budget for the treatment plant," said Ronalt Walz, Senior Engineer for Brown and Caldwell.
One of the Greenest
Walz called it one of the "greenest" projects he had ever worked on. Advanced combustion technology, for example, will contribute to the plant's overall fuel efficiency of 62 percent - almost twice the efficiency of a coal-fired plant. But from Walz's perspective, "the wastewater treatment plant and the cogen plant have been designed to make the most efficient use of resources while minimizing the impact on the environment in every way possible." The project received the Oregon Governor's "Sustainability Award" for the year 2000.
IMCO President Frank Imhof said cooperation and higher standards made the difference in the WWTP portion of the project. "The entire project has so many unique, trendsetting aspects to it that it is a privilege to be able to provide our expertise," said Imhof. "The team has made this project successful."
IMCO project manager Todd Vasey agreed. The partnering approach to construction management allowed for the project to be completed on time and within budget."
A Revenue Source, Too
Once the cogen plant is on-line, the city of Klamath Falls will also be able to participate in revenues generated by the cogen plant. Depending on market price of the electricity and once the bonds are paid off, the city could financially benefit $10 to $15 million per year - which is more than annual revenues generated from property taxes.
"In the first few years, the city expects to make approximately $3 million with additional revenues going to early retirement debt retirement. The city will be use its project revenues in part to reduce taxes, build city services and improve the parks. In addition, the revenues will be used to encourage economic development by providing low interest business loans and installing new infrastructure," said City Manager Jeff Ball.
The project incorporates many important environmental components as well as technical innovations and is setting a new standard in collaboration between private and public sectors as well as industrialists and environmentalists. In providing efficient power generation while improving water quality and use, the project serves as a model to many communities who strive to provide the best available stewardship of their resources.
"Green" Aspects of the Project
The WWTP will:
- Provide 2.8 to 4.2 million gallons a day of effluent to use in the cooling towers, so the cogen plant does not need to rely on fresh water for cooling.
- Discharge only one-third the usual amount into the river, since over 65 percent of the effluent will be evaporated.
- Remove chlorine and reduce the temperature of the cogen cooling system blowdown prior to discharge in to the Klamath River.
- Use the extension of the geothermal loop to heat buildings and digesters.
- Add bulking agents (such as tree trimmings) to the sludge to make compost, thus providing free fertilizer for the community.
- Convert a 42-inch diameter storm sewer pipe near the WWTP to a 15-foot wide by 500-foot long swale simulating a wetland using indigenous plants and shrubs.
The Cogen plant will:
Provide inexpensive steam to local industries, thus reducing their cost of business and reducing their reliance on their own boilers, which use wood, oil or gas for fuel. This will also reduce these sources of pollution.
Use advanced combustion turbine technology, contributing to the plant's overall fuel efficiency of 62 percent (nearly twice the efficiency of a coal-fired plant).
Additional environmental components:
Using low-NOx combustor technology to reduce NOx emissions.
Initiating a $4.2 million environmental program to offset carbon dioxide emissions from the plant. Some of the elements of this significant program include:
Financing the expansion of the geothermal loop in the city of Klamath Falls to include an additional 78 buildings.
Reforesting of approximately 6,250 acres in Oregon
Funding for the Oregon Climate Trust, a non-profit formed to implement Oregon's offset programs.
Building systems that will capture and convert methane gas to electricity at sewage treatment plants and coalmines.
Funding solar energy projects in developing countries, such as Sri Lanka, to bring energy to 100,000 homes.
Q and A
1. How is the cogen plant dispatched? Is it operated around the clock primarily or does it mostly follow load?
This plant will produce power to the degree that the market traders for PacifiCorp Marketing can sell power. At this point, power from this plant is sold at 100 percent for two years. The plant is also designed for cycling and limited peaking using duct burners to quickly service market conditions. Designed to be highly automated, the plant can go from being completely off-line to full production in two hours.
This particular plant is considered a "one-button" start plant using an automated sequencing program in the plant DCS for initial startup of one or two units, adding or subtracting a unit from service, and shutting down the plant. Once made ready for initial startup, the plant is designed to be started, stopped and restarted the following day using two operators without the necessity of leaving the central control room. The quick restart process after an overnight shutdown is possible because of automatic sequencing of the plant stack dampers, vents and drains and the use of sparging steam from an auxiliary boiler to keep the heat recovery steam generator (HRSG) drums hot and pressurized while shutdown.
There is complete redundancy of all major components in this plant and this, plus complete automation, sets this plant apart from the others.
Also, every piece of major equipment is indoors which reduces maintenance and improves performance.
2. What nitrogen oxides (NOx) emissions limits must the plant adhere to? Is any post-combustion NOx control such as selective catalytic reduction needed?
The emissions limits were set by the Oregon Department of Environmental Quality, and for this plant the maximum allowable NOx emissions was set at 4.5 parts per million (ppm). Our process uses dry low-NOx combustion with the selective catalytic reduction to meet these requirements.
3. Are the heat recovery steam generators (HRSGs) equipped with duct firing to gain additional outputs?
Yes. We have two HRSGs and together they will add 30-50 mw, depending on ambient conditions.
4. Is the cooling water provided to the cogen subjected to any additional treatment before being sent to the cooling towers?
The WWTP was upgraded to include complete redundancy and to refine the effluent, making it suitable for use as cooling water. A main concern was to remove phosphates that come from sources such as home detergents and car washes. The phosphates corrode or foul components in the cooling system. Sodium hypochlorite is added to control bio-fouling. The new treatment includes introducing sodium bi-sulfite to the return blowdown from the cooling towers to remove sodium hypochlorite. The cooling towers evaporate two-thirds of the treated effluent so; the water entering the Klamath River is two-thirds less in volume.
5. What is the water source for the water used in the HRSGs? What water treatment is used at the cogen to prepare this water for use in the HRSG?
The HRSG's use potable fresh water from wells, which is further treated by a demineralizer.
6. Who supplies the natural gas to the plant? Does the cogen have access to multiple natural gas sources to mitigate price pressures?
Gas Transmission owns the transmission line, but the gas itself is supplied by several sources. This option of suppliers will help the plant get the best prices from the suppliers.
This article originally appeared in the September 2001 issue of Water & Wastewater Products, Volume 1, Number 2, page 22.