Sewage conversion plant planned
By James Gonser
Advertiser Urban Honolulu Writer
The city wants to build a sewage facility at Sand Island that will transform dry sludge into fertilizer pellets and has filed a draft environmental assessment with the state to build the $33.8 million project.
The In-Vessel Bioconversion Facility is part of the city's planned $300 million overhaul of its sewage system mandated by the federal government to meet current regulations and would be on a vacant portion at the Sand Island Wastewater Treatment Plant.
Frank Doyle, acting director of the city Department of Environmental Services, said 8,468 tons of dewatered sludge are taken to the city landfill annually. That equals 56 truckloads per week carrying 162 tons.
The facility will use anaerobic digestion to convert that sludge into a pasteurized product suitable as a soil conditioner in pellet form. The pellets will be used in city golf courses and parks and sold for agricultural use, making good use of a waste product, Doyle said.
"I think this fits in with our sustainability measures," Doyle said. "This will provide compost and really help to move forward with the whole issue of recycling and sustainability. It is a good way to handle the solids."
To comment on the city's Sand Island Wastewater Treatment Plant New In-Vessel Bioconversion Facility, write to Synagro-WWT Inc., 1110 Benfield Blvd., Suite B, Millersville, MD 21108. Include copies for the city Department of Environmental Service, the consultant Analytical Planning Consultants Inc., and the state Office of Environmental Quality Control. The deadline for public comment is March 10.
Doyle said building the facility is more expensive than simply taking the sludge to a landfill, but with limited landfill space, this becomes a preferred option.
To comment
A Mainland company called Synagro has been awarded the contract to design, construct and run the facility for 15 years, Doyle said. There are at least 25 of these types of units across the country and about 100 operating worldwide, he said.
The In-Vessel Bioconversion Facility will replace the current sludge stabilization operation and include a 115-foot-high, 2.3 million gallon capacity digester, a 530,000-gallon sludge storage tank, a biogas storage tank and a hydrogen sulfide scrubber.
The sludge will be put in a centrifuge to separate out the water, then moved to a dryer and shaped into pellets, Doyle said. The whole process will be done inside enclosed equipment to contain odors.
Pending approval of necessary permits, construction is expected to begin in July and take about a year, with an expected startup in August 2004.
Jeff Mikulina, director of Sierra Club Hawai'i Chapter, said the environmental group has discussed the plan with the city and supports the project as long as the city does continuous testing of the sludge to look for contaminants and does not use the pellets for school grounds or park areas where children frequently play. "We support using it on golf courses and agricultural applications but not necessarily parks and schools," Mikulina said. "Kids are closer to the dirt and their bodies are more susceptible."
Mikulina said Hawai'i is fortunate not to have much heavy industry that would put heavy metals in the sewage sludge and make it more difficult to purify. But, he said, with just one aquifer on O'ahu we need to be extra careful about protecting our water source and not let it become contaminated.
Federal regulations governing the reuse of sewage sludge cover only nine heavy metals and two pathogenic organisms, Mikulina said. He would like to see Hawai'i go beyond federal guidelines in eliminating hazardous substances from sludge.
"Just abiding by the federal regulations we don't think will suffice in protecting public health," Mikulina said. "The big picture is going up the waste stream and making sure we separate out green waste and other things that can be recycled before they get mixed in."
