by Giovanni Roverso
Big changes, namely anaerobic digesters, are in store for Bellingham’s wastewater treatment plant at Post Point, Fairhaven.
The digesters would replace a pair of aging incinerators. They are the core features of the Resource Recovery project which will come online around 2027. The plant would become more eco-friendly, sustainable and cost-effective according to various city documents.
Implementing the digesters and related systems is estimated to cost $196 million to the city, according to the project technical memorandum dated May 9, 2019.
Included in the $196 million project would be a methane recovery and scrubbing system. The gas would then be sold and injected into the line which currently feeds the incinerators. Solids from the digesters would then be turned into a class A biosolid, which means it is made safe by removing pathogens. Then this would be trucked away for preparation at a fertilizer plant.
Single family sewer cost will increase by 50 percent. The cost per single family was about $43 a month in 2018. The new cost, adjusted for 2023 inflation, would be $75 a month.
Over the next 30 years, the memorandum estimated, the city should expect to pay $400 million, with a yearly debt service of $13.8 million. The city would be paying 5 percent interest and 1 percent issuance cost. Projected inflation in the United States from 2023 to 2050 is about 95 percent, which explains why the figure seems to double.
The total cost of the upgrades, however, is still up in the air and will depend on how stringent the Washington State Department of Ecology’s (Ecology) limits are determined in the next few years, with current estimates for the entire nitrogen removal project in the ballpark of $450 million.
Sea Level Rise
The Post Point plant is located near sea level. Until recently, the city of Bellingham only had to account for a 28-inch sea level rise in new shoreline developments.
But on June 22, the City Council stated it is now considering a 2018 study by the Washington Coastal Resilience Project for Waterfront District projects, which estimates sea levels could rise 50 inches over the next century in a worst-case scenario. Post Point is not in the Waterfront District per se, so the restriction may not apply. A 50-inch sea level rise would also be a non-issue if the plant is not going to be in use in 100 years’ time.
The new sea level requirements are still being evaluated for the adaptation section of the climate change action plan currently under development by the environmental resources division of public works, according to the city’s Shoreline Master Program (BMC 22). Johnson said Natural Resources would know about a more stringent sea level rise requirement. Natural Resources Assistant Director Renee LaCroix could not be reached for comment. _____________
Residents can expect to see 22,000 square feet redeveloped in the northeast corner of the plant near the intersection of 4th Street and McKenzie Avenue. The space, owned by the city, is currently occupied by a gravel lot and three warehouse-like buildings, one of which is currently used by a company called Cypress Designs, and the others are used by city staff, Plants Superintendent Robert Johnson said.
If you walk down McKenzie Avenue toward the plant entrance, you would pass by the current location of the HomesNOW! Safe Haven tent and tiny home village. Before the street turns left toward the plant, you can see an enclosed garden with a sign that says, “Recovered resources at work.”
Johnson said the garden was set up as a demonstration of the usefulness of fertilizer derived from wastewater treatment plant biosolids. The city bought a palette of this kind of fertilizer from outside Bellingham for the demonstration.
Currently, solid waste is separated and incinerated at the plant every day and inert ash is trucked away to the landfill. One furnace is 42 years old and the other is 22, and the usual lifespan is 25 years. The furnaces burn about 25,000 cubic feet of methane every day, or 2.5 million kilowatt-hours of energy every year. Bellingham’s 2007 climate action plan found that Post Point contributes a high amount of greenhouse gases. One of these, carbon dioxide, also contributes to ocean acidification.
A 2010 planning study found the incinerators should be replaced. The chance of the furnaces failing increases with age and maintenance is costly and frequent. Costs could even surpass $20,000 per day if they have to go down for repairs, according to City Council agenda bill 21397.
The study was updated in 2012 to factor in tighter Environmental Protection Agency air quality regulations, which made sticking with an incineration system less attractive.
The city of Bellingham’s sewer system dates back almost 130 years.
Wastewater Treatment in Bellingham
In 1892, a clay pipe network was first implemented and combined sewage and rainwater, discharging it into Whatcom Creek and Bellingham Bay. Additional storm sewers were installed in 1908.
In 1947, the city began treating wastewater near the mouth of Whatcom Creek. Early sewer lines had to be intercepted. And the effluent was pumped into a shallow part of Bellingham Bay.
When the city needed to upgrade its capacity, it moved wastewater treatment to the Post Point recovery plant at 200 Mckenzie Avenue near Marine Park, the railway, and a heron colony and forage area.
The new system handled up to 55 million gallons per day and received wastewater from 250 miles of sewer connection mains. It could also accommodate for septic tank collections.
The plant was upgraded to include secondary treatment in 1993, a system removing 95 percent of contaminants at a cost of $55 million. In 2011, construction began to increase plant capacity to a peak of 72 million gallons per day.
Completed in 2014, capacity was increased, as required by the city’s 2009 Comprehensive Sewer Plan, at a cost of $53.3 million and developed by Carollo Engineers.This allows the plant to process 34 million gallons a day for a month straight. To put things in perspective, December 2015 had the highest flow that year of an average 18 million gallons a day. Moving forward, the city must juggle sustainability and environmental regulations, population increases and costs.
Pros and Cons
The engineering firms, Carollo and CDM Smith, were tasked to help evaluate different ways to deal with the biosolids. In 2016, the city’s public works department reached out to Brown and Caldwell to develop a digestion solution.
Brown and Caldwell, an employee-owned engineering and construction firm which has been operating for over 70 years, has worked on major city wastewater treatment projects around the world.
The firm helped Tacoma develop improvements to its wastewater plant’s digestion and liquid stream systems to be more effective and efficient in 2010.
For the Bellingham project, a variety of environmental, financial, social and technical criteria were used to select the best digester alternative. Core strategies in the city of Bellingham’s 2018 Climate Action Plan, like energy efficiency and conservation and waste reduction, influenced some of the criteria. Anaerobic digestion is more efficient than aerobic digestion because it saves on the cost of providing oxygen for the biological and chemical reactions to occur.
The Tacoma Central Wastewater Treatment Plant started producing a line of soil amendments from its class A biosolids called TAGRO in 1991. The city of Tacoma says this type of fertilizer is much more cost-efficient than synthetic ones and releases nutrients into the ground much more steadily and reliably.
However, the Tacoma plant, which uses a combination of aerobic and anaerobic stages, had a rough start with TAGRO. Back in 2004, Daniel Thompson, operations division manager at the plant, wrote a feature about how his predecessors had trouble selling TAGRO products because they stunk in warm weather.
The smell of the product was addressed by reducing the temperature of the anaerobic digesters from 130 degrees Fahrenheit to 115 degrees Fahrenheit. But plant workers would still get sick from the fumes (which were near the safety limit). So, as Thomson described, he had the process modified to what is known as temperature-phased.
As such, the first digester was kept at 130 degrees Fahrenheit, which is where thermophilic bacteria thrive. These make mostly methane, but are also the smelliest. The second, intermediary digester was kept at 100 degrees Fahrenheit. The third digester was lowered to 90 degrees Fahrenheit. This temperature encourages mesophilic bacteria to grow and reduces smelly gases, but also methane.
For Post Point, by May 9, 2019, planners whittled the options down to three:
• Mesophilic anaerobic digestion: considered reliable and efficient, but produces Class B biosolids, which would have to be further processed to be a completely safe Class A product.
• Autothermal Thermophilic Aerobic Digestion Plus Temperature-Phased Anaerobic Digestion (ATAD/TPAD): this is like the Tacoma system. The aerobic stage helps kill pathogens by feeding bacteria oxygen or air, then gradually cools in the anerobic digesters.
• Temperature-Phased Anaerobic Digestion (TPAD): similar to Tacoma’s anaerobic phase, but without an aerobic phase preceding it. Instead pathogens are killed by using more energy to heat the first stage and requires a lot of heat exchangers to cool it down in the following stages.
As for the smell, the Feb. 15, 2019, technical memorandum stated that it would not be a problem because the digesters would be airtight. Exceptions would be during occasional cleanings and when biosolids are loaded onto trucks headed for the fertilizer plant. Odors would be controlled if the city assessments find them getting out of hand.
Truck traffic would likely increase from one truck a week for ash to one to two trucks a day if they’re transported wet, or just four to five a week if dried out first. Trucks would be scheduled to travel during low-traffic times on less-trafficked routes.
Nitrogen removal was mentioned as a possible requirement in the environmental criteria section of the project technical memorandum dated May 9, 2019. It said that the Washington State Department of Ecology could deem nitrogen removal necessary as it studies its impacts on Puget Sound habitat.
The Puget Sound is naturally rich in nitrogen which comes from the ocean, according to Suzanne Strom, senior marine scientist at Western Washington University. She didn’t expect Bellingham would be affected by man-made nitrogen as much as Pierce County, which has less water circulation.
Strom said Bellingham Bay was more similar to Victoria, B.C., in that sense. She said only certain embayments with restricted circulation, like in the south Puget Sound or the Saanich Inlet, would be very affected by algae overgrowth in the sunnier months of the year. Algae growth can deplete oxygen and causes red tides in the worst cases.
Capstone research by WWU graduate Everitt Merritt indicated that ocean waters contributed 98 percent of Bellingham bay’s nutrients, with the Nooksack River contributing 1 percent and Post Point contributing less than 0.5 percent.
Recent studies considered by Ecology however, found oxygen levels to be lower in the northern part of Bellingham Bay from April to October. Low oxygen, or hypoxia, can harm marine life and was the primary concern of the study. It determined that reducing man-made nutrient inputs could improve the situation considerably.
The Post Point plant discharges its effluent 60 feet down and about a quarter mile out, but Strom said that, since it is fresh water, it would be easy for it to rise up above the denser ocean salt water.
During a Public Works and Natural Resources Committee presentation on July 20, city councilmembers expressed concern about the additional development costs nitrogen removal would entail. Total project costs for the nutrient removal would likely be in the range of $410 million to $510 million (in 2030 dollars).
“We’re a utility service, moneywise. We’re a utility service with the rest of this city hanging off it,” councilmember Michael Lilliquist said. “These are really big decisions and I think we need to understand the technology […] so we don’t need to spend a dime more than we have to, or more accurately, so we don’t charge our customers a dime more than we have to.”
At the meeting, Brown and Caldwell Vice President Tadd Giesbrecht said Ecology will likely complete an individual plant permit within a year, limiting nitrogen levels to what is currently being discharged plus some wiggle-room for population growth.
When the digesters come online around 2026 or 2027, Giesbrecht said, molecules containing nitrogen will spike in the liquid stream as the water removed from biosolids is recycled. Currently, most of these nutrients get destroyed.
A general permit for the Puget Sound would come later, Giesbrecht said, mandating a reduction made more and more stringent over a 10-year period. Ecology would likely be releasing it in two or three years as it continues its modeling research, Giesbrecht said.
He presented a study proposing a moderate reduction scenario where the plant’s effluent would have to contain less than 8 milligrams per liter of inorganic nitrogen between April and October, and a worst-case scenario where no more than 3 milligrams per liter of total inorganic nitrogen would be allowed year-round.
Brown and Caldwell also developed upgrades to the Pierce County regional wastewater plant, Chambers Creek, improving capacity and efficiency and improving nutrient removal.
Brown and Caldwell project engineer Adam Klein, said Pierce County’s DEMON nitrogen removal system has been operational for four years. It cost $7 million to implement. DEMON is an anammox sidestream treatment which removes about 20 to 40 percent of the nitrogen in wastewater in the form of ammonia and nitrate by alternating oxygen and specialized bacteria applications.
“Regulation hasn’t come down yet,” Klein said. He said Ecology has been warning people and they wanted to get ahead of the game.
Giesbrecht said an undetermined sidestream nitrogen removal at Post Point would cost about $10 or $15 million and could be designed alongside the biosolids project be more cost-efficient.
The larger nitrogen removal project would involve the biggest expenses. It would likely occur in the southeast corner, taking up space where the public footpath bends around the plant.
Planners have begun working on facility implementation planning (phase 3) which includes:
• discussions with stakeholders, n a rate study assessing the range of impacts the project costs would cause,
• discussions with Ecology and a study to plan for the incremental developments of nutrient removal systems as the caps become known,
• developing a marketing strategy for fertilizer products and weighing whether a private or a public fertilizer establishment would be more appropriate,
• agreeing to standards with the natural gas company about gas quality requirements.
Design would likely start in 2021 or 2022 and construction would begin between 2023 and 2025, Giesbrecht said.
The last Post Point plant upgrades completed in 2014 were made to accommodate a growing city population up until the mid-2030s.
Because of the limited space at the site, he said he only expects the plant to be able to expand capacity up until 2050 or 2060. The need for a second plant, Giesbecht said, will depend on population growth which is expected to rise by 40,000 by mid-century and on how much nutrient removal will be required.
Brown and Caldwell plans for periods of 20 years. Johnson said planning out much further than that is difficult because of the unknowns: technological developments, regulations and population growth.
Planning a second wastewater treatment plant is a way off, but capacity at Post Point will run out before the end of the century, and the city will have to figure out where to expand to.
Giovanni A. Roverso is an Italian-American visual journalism major at Western Washington University. Portfolio and blog at www.giovanniroverso.com.