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Wastewater Treatment

Aerial view of the plant looking towards the Payette River.
Aerial view of the plant looking towards the Payette River.

Is your home safe from a possible sewer back up?

Many homes naturally prevent sewage backups due to their plumbing design or location. One key to prevent sewage backups from entering your home is to know your location in relation to the sanitary sewer system that serves your home. Homes with drains located below the elevation of manholes on nearby streets may be in danger from sewage backups. In this situation, a backwater valve can offer tremendous benefits. A backwater valve is a plumbing component used to prevent sewage from backing up into a home. A backwater valve contains an automated gate that senses a reverse flow in the pipe and completely closes the line.

 

The Idaho Pluming Code currently requires that when a fixture is installed on a floor level that is lower than the next upstream manhole cover of the sewer collection line, that fixture must be protected from backflow of sewage by installing a backwater valve. For more information on sewer line "blow backs", click here.

 

Overview of the WWTP

City of Payette

     Do you ever wonder what happens to the water after it goes down the drain?  Or are you like most of us and never give it another thought?  Out of sight - out of mind.

     In short, all the "waste" water works its way thru the collection system, a series of pipes all over town, until it reaches the plant.  At the plant it runs through a complicated process which cleans it up so well it is allowed to be placed back into the river.  Pretty cool, huh?

      Following is a very complicated explanation of our wastewater facility and how it all works.  The City of Payette is very fortunate to have four trained and capable professionals taking care of this process for us.  We are very grateful they understand how all this works together and that they have the health and safety of our community foremost in their minds.

Read on......

The Payette wastewater treatment plant is an activated sludge plant. It is designed to handle a maximum flow of 2.88 m.g.d. Average daily flow is 1.5 m.g.d. serving a population of 7,454. Our pre-treatment consists of one Hueber Step Screen, fine screen and wash press. After screenings are removed and emptied into a dumpster, the flow is directed to a Westech Vortex grit separator, Westech grit classifier, then to a JDV Equipment shaftless screw conveyor from which the grit is then dropped into a dumpster for disposal.

The wastewater then flows into two 48" diameter lift screw pumps with a 5 m.g.d. each capacity. It is pumped 30 feet and then gravity fed into two oxidation ditches holding 1.4 m.g.d. in each ditch. The ditches are supplied with three Lakeside rotors per ditch. When the flow leaves the ditches, it flows into two 60' diameter secondary Westech Clarifiers, average depth of 10', which incorporates the C.O.P. (Clarifier Optimization Package) system.

The RAS / WAS is then directed into a vault, located below the RAS/WAS building, where the RAS is returned (using one

Aerial Photo looking from the Payette towards River Street
Aerial Photo looking from the Payette towards River Street
of three Vaughn Chopper pumps, with a capacity of 1,000 g.p.m. each) into the ditches just before the number one rotors. The WAS is pumped (using V.C.P. w/150 g.p.m. capacity) into an 80,000 gallon aerated holding tank.

The effluent from the clarifiers is disinfected with CL2 through a chlorine loop. The CL2 is administered thru a two inch pipe pumping the chlorine between the scum baffle and weirs. The process begins as the effluent passes under the scum baffle where it is injected with the CL2 within the loop and then passes over the weirs to rest in the two-unit contact chamber allowing adequate contact time for the disease causing bacteria to be destroyed. As it flows out of the CL2 contact chamber, it is injected with sodium bisulfite to reduce the CL2 concentration. The sodium bisulfite is held in a dechlorination building consisting of two Wallace and Tiernan analyzers and two Watson Marlow dechlor pumps. The treated effluent then flows into the Payette River with BOD removal and TSS at 98%.

Our sludge handling consists of a dewatering building with a Somat vertical screw press unit. The sludge is pumped from our 80,000 gallon aerated holding tank at approximate 1.5% solids into a floculation tank and mixed with polymer from a polyblend unit. After mixing, it is run through a vertical screw press and dumped into a dump truck at 10% solids. It is then hauled to the Payette County Landfill for land application. We also have 25,000 square feet of sludge drying beds available on-site when needed. In addition we have a self-contained 1-acre asphalt pad as backup for sludge storage. We haul approximately 350 metric ton of sludge annually to the landfill.

We are fortunate to have a computerized monitoring system (SCADA) which gives us the capability to monitor levels and alarms at the plant as well as four lift stations. Our plant is monitored 24-hours a day, seven days a week.

For emergency backup power, the plant has a 365 kw generator powered by a Cummins engine which will more than take care of the plant in case of a power loss.

Our wastewater treatment facility is staffed by four capable and dependable employees. They maintain 60 miles of collection lines and mains and four lift stations. Our City is home to a major food processing plant which contributes on the average of 325,000 g.p.d. 

Recently Achieved Goals...

Plant Modification - New pretreatment building and equipment; new lift pumps; new RAS and WAS building and pumps; pipe and valving

Dechlorination equipment - modification of contact chamber; dechlor building; equipment and pumps

Purchase of 5 acres for future plant expansion

Replacement of scum baffles and weirs with fiberglass units in secondary clarifiers

Looking to the Future...

New permit -- 

          Phosphorus removal

Upgrading dewatering equipment, adding dryer

Possible expansion