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Sewer Maintenance
909 East Sprague Avenue 99202
Phone:(509) 625-7900
Fax:(509) 625-7940
Riverside Park Water Reclamation Facility
4401 N. A.L. White Parkway 99205
Phone:(509) 625-4600
Fax:(509) 625-4605
Treatment Plant

NEXT LEVEL OF TREATMENT PILOT

Riverside Park Water Reclamation Facility
City of Spokane

Six technologies are being tested to determine which one(s) are best suited for Spokane’s Next Level of Treatment. They are adapted for use in treating municipal wastewater from their origins as drinking water treatment (e.g. river water) or other waste treatment processes (e.g. mining).

Two stages of treatment are being tested to remove phosphorus down to below 50 parts per billion. The S, K and C units provide first stage “sedimentation” treatment. The F, B and Z units provide second stage “filtration” treatment. In general, a coagulant (metal salt) is added to bind with dissolved phosphorus to form “floc” particles big enough to settle out in the first stage or be filtered out in the second stage. Polymer is used in most processes to enhance performance. Effluent from the Pilot is blended with plant effluent for disinfection and discharged to the river. Next Level of Treatment will meet Washington’s Class A Reclaimed Water standards, suitable for irrigation or industrial uses and approved for human contact, but not for use as drinking water.

1st Stage Units – Sedimentation (these are not filters; the particles settle out)
  • “S” – conventional Sedimentation, provided by CORIX of British Columbia. The particles are very light and settle slowly, so it requires large tanks.
  • “K” – ballasted sedimentation, provided by Kruger of North Carolina. The particles form around grains of sand, which causes them to settle faster, allowing smaller tanks. After settling, the phosphorus is stripped off and the sand mostly recycled.
  • "C” – variation on ballasted sedimentation, provided by Cambridge Water Technologies of Massachusetts. The particles form around grains of magnetite, which is heavier than sand, causing even faster settling. Magnetite is magnetic, so magnets are used to help remove the particles from of the water. The magnetite is mostly recycled.

2nd Stage Units – Filtration (these units physically strain out particles too small to settle)
  • “F” – conventional dual media granular Filter, also provided by Corix. The particles are filtered out as the water slowly sinks through beds of anthracite (coal) and fine sand. Slow settling requires large tanks. Occasional backflushing is required, so redundant tanks are needed for everyday operation.
  • “B” – continuous upwash sand filter, provided by Bluewater of Idaho. Water continuously flows upward through chemical-coated sand to capture phosphorus, avoiding the need for regular backflushing. The phosphorus is stripped off the sand and the sand is mostly recycled.
  • “Z” – membrane filter, provided by Zenon of Quebec. Particles larger than the membrane’s pores are strained out as the water passes through the membrane. The membranes require chemical cleaning and occasional replacement, so redundant units are needed.
Pictures of the Pilots

L. Hendron, P.E.
Wastewater Mgmt
May, 2010