Wastewater treatment plants on Oahu earn recognition for excellence in safeguarding Hawaii’s precious resources
The weather on Oahu today is probably in the 80s with sunshine — because that’s nearly always the way it is. It will probably rain somewhere, although areas of the island are quite dry despite being part of the most tropical state in the U.S.
Treating wastewater on Oahu is the job of the 300 employees who work for the City and County of Honolulu under the direction of Tim Steinberger, director of the Department of Environmental Services.
ENV, as it is called, is the municipal utility for the city and county, which encompass the entire 600-square-mile island of Oahu, 2,500 miles off the U.S. mainland and home to nearly a million people. The department is also responsible for collecting and managing solid waste on the island.
ENV collects 105 mgd of wastewater with 2,100 miles of pipeline and 70 pump stations and processes it all at nine wastewater treatment plants. Four of the plants use deep ocean outfalls, while others use underground injection wells.
Operators face the challenge of producing high-quality effluent and, increasingly, reclaimed water to support irrigation and reduce stress on groundwater resources. Technology in the form of an island-wide SCADA system helps the staff of 90 operators keep tabs on the entire system.
ENV has a history of award-winning plants. “We have a lot of Gold and Silver awards from the National Association of Clean Water Agencies, and the Waianae plant has received Platinum awards for several years running,” says Steinberger.
The NACWA Peak Performance awards are based on permit compliance. Silver awards are for five or fewer permit violations in a given year, Gold indicates 100 percent compliance for a year, and Platinum goes to plants that have received Gold awards for five years in a row.
In 2009, the Waianae plant received its eighth consecutive Platinum award, to go with eight Gold awards and six silvers since 1994. The Honouliuli and Kailua facilities received Gold awards in 2009, Sand Island received a Silver, and Kahuku has received a variety of national and state EPA awards in the past.
Keeping the plants running so well comes down to good operators. “Operators who are dedicated to their work and who take ownership of their facility — that’s really the bottom line,” says Steinberger. “We partner with the state Department of Health and the University of Hawaii to make sure our operators receive their training and keep up with their continuing education credits.”
ENV meets most of its staffing needs from within the state, though the pool of employees is somewhat limited. “New operators work as assistants for the first year or two and make their way through the certification process and on-the-job training until they achieve an Operator 2 license and progress to an Operator 4,” Steinberger says.
With a relatively small population to draw from, it’s important for ENV to develop its employees, though it does go to the mainland to recruit for some higher level management positions.
Keep it running
“Like all municipalities, we face an aging workforce,” says Steinberger. “We have so much experience out there, people who have been working here 35 or 40 years. When you have that kind of wisdom that is about to retire, you kind of cringe; even though others have been working 20 or 25 years and are very capable, you like to have those seasoned veterans out there.”
Good operators, while key, are not enough to operate an effective wastewater plant. Good maintenance is essential. “As long as you keep the facilities well maintained and give operators the tools they need, there is no reason why your plants should not be able to stay in compliance consistently,” Steinberger says.
ENV has a central shop at its Sand Island plant, and all plants use a common database for reporting maintenance issues. “The database creates work orders for the maintenance crews,” says Steinberger. “Some of the work can be done by the assistant operators on site, and some jobs may require that we send out a mechanic or electrician.”
Preventive maintenance uses a three-tiered program of high, medium and low priorities. The idea is to keep the high-priority items to a minimum. That means focusing on the medium and low priorities so they never rise to the high-priority level.
The ocean environment works to the department’s advantage. “Hawaii is a volcanic island, so it rises off the ocean floor very rapidly,” says Steinberger. “We can discharge our effluent out a mile and a half and we’re already 200 or 300 feet down. We do extensive monitoring, as well. Over the years, we’ve never shown any type of occurrence of contaminants coming to the shore.”
There is no shortage of freshwater in Hawaii, but on a series of islands in the middle of a vast ocean, groundwater becomes a critical resource. “Fortunately, it rains quite a bit, and given the volcanic nature of the island, we’re able to retain a lot of that water in the ground,” says Steinberger.
But virtually all of Oahu’s drinking water comes from groundwater, and demand continues to grow. “We are a thriving city, about the twelfth largest in the United States,” says Steinberger. With growth comes increased attention to protecting groundwater, both to maintain the resource and to prevent drawing it down so much that saltwater can intrude and spoil the entire supply.
Water reclamation helps limit pressure on groundwater supplies. About 12 mgd of secondary effluent from the Honouliuli plant goes on to the neighboring Honouliuli Water Recycling Facility, a tertiary plant that treats the water to R-1 quality, the highest level of treatment in Hawaii.
“That is distributed mostly to golf courses and parks,” says Steinberger. “The area southwest of Pearl Harbor is very hot and dry. They only get about 15 inches of rain a year. So they’re able to use that water to assist in irrigation, and there are a lot of golf courses on that side of the island.”
Lots of farming
The Wahiawa plant’s discharge is also recycled. It is the oldest plant on the island and the only ENV facility that discharges to freshwater — the Wahiawa Reservoir. The reservoir was created in 1906 to provide irrigation to Oahu’s sugar cane industry. While sugar cane production in the state is down to about the same levels as it was in 1900, the area now contains diversified agriculture.
Rainfall varies greatly on Oahu because of its two mountain ranges. The eastern Koolau range can get 280 inches of rain a year. The smaller Waianae range gets 30 to 60 inches. The southern part of the island and the western coastal regions are semi-arid (like the dryer parts of Texas and New Mexico) and average less than 20 inches per year.
“There is a high demand on our aquifer, so any offset we can do by recycling water certainly is a help,” says Steinberger. “Long term, I think we’ll look at every plant to see if there is an opportunity for water reclamation and reuse. The Sand Island plant is right in the urban center of Honolulu, so finding areas for large-scale use of 70 to 80 mgd of reclaimed water is a bit of a challenge.” ENV’s other facilities are more likely candidates, since they are in the more rural areas.
To run the facilities, plant operators get an assist from an island-wide SCADA system installed in the mid-1980s to monitor and control wastewater equipment from a central location at the Sand Island plant. Staffed around the clock, it monitors all pump stations and treatment plants, two stormwater pump stations, and four preliminary wastewater treatment plants.
The department also has a biosolids facility near Sand Island operated by Synagro. It can process up to 10,000 dry tons annually from Sand Island into a Class A organic fertilizer through in-vessel bioconversion. Synagro markets most of the resulting pellets to golf courses, farms, and landscapers. The city and county use about two tons per month to fertilize public properties, such as parks.
The biosolids from Honouliuli used to go to Naval property for composting, but the Navy closed that site in 2009. A new agreement with Hawaiian Earth Recycling will result in the composting of biosolids from most of the ENV plants except the Laie Reclamation Facility and Sand Island, beginning in 2012.
Another public-private partnership with Pacific Biodiesel converts 40,000 gallons of FOG into boiler fuel every month for use at businesses in the Campbell Industrial Park on the far southwest part of the island.
Hawaii is known for its warm and pristine waters. Keeping it that way takes a lot more work than most residents and the 8 million annual visitors will ever realize.