Sewage of the future?
June 12, 2008 · Updated 10:19 AM
"The future of sewage treatment is coming to Port Orchard.City of Port Orchard and Kitsap County Sewer District 5 personnel are revamping the Wastewater Treatment Facility to provide the latest technology for treating a growing amount of human waste.The expansion project is intended to increase the capacity of the Olney Road plant without significantly increasing its physical size or the amount of treated water it deposits into Sinclair Inlet. The project also includes an odor abatement effort.Once the expansion, scheduled to begin in 2003, is completed, the treatment facility's maximum capacity should be more than 4.5 million gallons per day, up from the current capacity of roughly 2.8 million gallons a day. Odor mitigationThe most immediate change to the plant will be the installation of a new centrifuge used to spin the liquids out of solid waste. The centrifuge arrived at the facility yesterday, but won't be installed until later this summer.The city will go out to bid during the middle of this month for a contractor to install the giant centrifuge in a round building known as the digester room, where solid waste is sent to be separated from liquids. The Port Orchard City Council is expected to review bids March 26.The current technology used at the plant for treating solids - a machine with two big screens that squeeze together called a belt filter press - is about 14 years old. The wastewater treatment facility has to have parts specially made to maintain the piece of equipment.In addition, because the belt filter press allows solid waste to come into contact with the atmosphere, it's the source of some pretty bad smells.The large centrifuge and a smaller one currently being used at the plant are expected to mitigate that smell. Because solids will be pumped directly into the centrifuge chambers, the smell should be noticeably reduced, said City Engineer Larry Curles.The new centrifuge is also expected to increase the amount of liquid extracted from solids at the wastewater treatment facility, reducing the bulk of the solid waste that has to be stored and contained.Once liquids are extracted from solids in the centrifuge, the remaining solids are contained at the facility. A trucking company hauls the container to Fire Mountain Farms to reclaim for use in growing crops and trees.In addition to getting rid of the belt filter press, the Port Orchard City Council last month approved an ordinance annexing a two-and-a-half-acre portion of wooded land behind the facility to further assist with odor control.When the expansion portion of the project gets going, work crews will lay dirt and wood chips on the site. Air generated at the plant will be pumped through the wood chips and soil, the natural filtering properties of which will absorb the foul smell of the sewage plant.Before construction can begin on the expansion, the city will have to get the appropriate permits and secure sources of funding. We already know what the growth will be. We agreed on the technology. Now, we're working on final documents, said Port Orchard City Councilman John Clauson, chair of the city's Water, Sewer, Solid Waste and Health committee. We're looking at various ways to increase capacity without increasing the physical size, he said.When the facility was built in 1962, the plant probably served fewer than 3,000 people. According to the 1960 census, there were 2,778 people living in Port Orchard. In 1984, when the plant was expanded, about 4,840 people lived in Port Orchard.Today, the plant, which employs nine people, treats about 1.3 million gallons of sewage a day, providing service throughout the city of Port Orchard, east Port Orchard, McCormick Woods and other areas of south Kitsap County. The city estimates the average household creates about 180 gallons of wastewater a day. As the number of subscribers grew over the years, the city created a late-comers' fee to off-set the cost of providing service and to save for an expansion city planners knew the facility would eventually need.During the past several years, Curles, working for the city, and Paul Gilligan, the consultant working for the sewer district, have analyzed projected growth to guide city and facility staff over how much more sewage the city will need to be able to treat in the future.The city adopted its sewer comprehensive plan last year. We saw it coming and have been preparing for it, Curles said.At the plantMiles of city and Kitsap County Sewer District 5 sewer pipes converge at the wastewater treatment facility, emptying into an enclosed, shed-like building referred to as the headworks.Raw sewage collects in a huge vat in the headworks, where it runs through a series of bar screens that raise out of the water. The screens are designed to catch and lift debris, like rocks and rags, out of the sewage.The next stop is the grit chamber, where the sewage spends some time to allow sand and grit to settle out.As part of the expansion project, the headworks will be re-designed to create a vortex in the grit chamber. The whirlpool won't require any extra energy - gravity, which pulls the water to each new chamber, will pull it around the curves in the vortex - but it will more efficiently pull sand and grit from the sewage.From the headworks, the sewage follows a channel to outdoor tanks known as primary clarifiers, three square tanks with grated channels between them. As the water level increases from flow coming from the headworks, clarified water spills over the top of each tank into the next one. Solids sink to the bottom.From 1962 until 1984, this was the end of the road for sewage treatment on Olney Road - which, at the time, was only used by the sewer district. The city operated its treatment facility off Bay Street. During that time, sewage left the headworks, settled in the primary clarifiers, was chemically treated and went into the bay - and was considered sufficiently treated by the Federal Environmental Protection Agency and the Department of Ecology.Prior to 1962, there was no treatment at all. Sewer pipes converged into one main that emptied straight into Sinclair Inlet.After 1984, the city and sewer district destroyed the district's old facility on Olney Road, re-building a bigger, better headworks and adding a couple more steps to the treatment process.Once the sewage works its way to the end of the set of primary clarifiers, it flows into vats 20 feet deep with aerators installed on the bottom.These vat, called aeration basins, are where microorganisms are introduced to munch on the sewage. The microorganisms are mostly protozoa - microscopic creatures with a blobby head on one end and a thread-like tail on the other. That tail is the sucker, sort of like a mosquito's proboscis, that the protozoa sticks into the sludge to dine.The aerators keep the vats surging and bubbling - a film of foam develops on top - to keep the microorganisms alive. A chute from secondary clarifiers farther up pumps brown, microorganism-rich liquid into the vat to replenish the supply of life in the aeration basin.Now treated with protozoa, the sewage flows into the secondary clarifiers - giant, cylindrical tanks with an arm that slowly moves around the circumference of the tank. The bottom of the secondary clarifier tank is sloped and the arm has a spatula-like scraper on the bottom to push the solids that settle out into a hole that leads to a hopper.As the microorganisms get full, they slow down and sort of sink into the water in the secondary clarifiers. From the secondary clarifiers, the chute pumps the protozoa, which eventually will get hungry again, back to the aeration basin, where they will find ample food to consume.The outer rim of the secondary clarifiers is somewhat low, allowing water clarified to spill over the top. A circular chamber containing chlorine surrounds the secondary clarifiers, and it's there the treated water comes into contact with a chemical agent to kill any life forms that might be left in the water.The treated water then follows a channel into a pipe that deposits the water 1,600 feet out into Sinclair Inlet.Lab technicians check water throughout the day as it comes into the headwaters and as it leaves after being treated. The future of sewage treatmentBecause the Clean Water Act restricts the deposit of chlorine into the water, facility planners are looking at some new technologies to increase capacities and efficiencies while reducing the amount of chemicals.The technology that will be installed could be likened to spaghetti.A multitude of thin strands of a membranous material are loaded and enclosed in a cartridge, hanging from the top and connected at the bottom and looking a lot like noodles. The strands of membrane are about one micron thick. As part of the expansion project, the wastewater treatment facility will install a divided tank about 87 feet long and about 48 feet wide adjacent to the primary clarifiers near the headworks. The cartridges will be lowered by crane into the new tank. Half the flow coming from the headworks will be diverted to the tank outfitted with the cartridges of membranous tubes. The sewage will be forced through the filters with pumps. The other half of the flow coming from the headworks will continue on the standard path to the primary clarifiers.The pores in the membranes are so thin, they'll filter out bacteria and anything larger, meaning essentially everything but viruses will be filtered out of the sewage passing through the tank.Ultra-violet lights, which will be submerged into the water, should take care of killing any viruses, essentially eliminating the need for chlorine. Water from the secondary clarifiers will be added to the water treated through the membrane and UV light process before going out to the bay.Theoretically, the treated sewage leaving the membranes and ultraviolet light process will be clean enough to use as recycled water for things like watering golf courses.While the ultraviolet lights will be expensive to purchase and run, city engineer Curles said they'll still save the city in the long run. The Clean Water Act requires any water treated with chlorine has to be dechlorinated before it's deposited into the waterways.So far, studies and demonstrations of the technology look promising. We're very pleased, councilman Clauson said. It seems to be the way of the future. It will allow us to (treat) a considerably larger volume without increasing the footprint. And the quality of effluent is better than what we're getting today. "