Swimming Pools
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Swimming Pools

Recycling of swimming pool backwash wastewater

Swimming pools are popular places to go to with the family or to meet with friends and to do something for your health and fitness at the same time. The compliance with demanded water quality resp. water quality regulated by Health Care Compliance needs expertise as well as a certain diligence.

Regular backwashing of widespread sand or multi-layer filters in accordance with the manufacturer's specification is essential for proper cleaning, maintenance and operation of pool filters. Swimming pool backwash wastewater consists of all of the pollutants that are filtered from a pool. Most pollutants are introduced into the pool from bathers. Backwash water may be heavily polluted with a wide range of pathogenic micro-organisms and chemicals. Usually the wastewater generated from backwashing is discharged to the sewerage system in accordance with the local sewerage authority.


Recycling swimming pool backwash water involves treatment to a suitable standard to allow recycling into the pool. As pool water will be accidentally swallowed, the quality of recycled backwash water should meet Drinking Water Guidelines and controls need to be in place to protect against system failures.

Reverse osmosis is presently the best available technology for the treatment of backwash water for recycling. Worldwide used reverse osmosis applications has been shown to remove the majority of dissolved contaminants (more than 98,5 % dissolved salt and up to 97 % of most dissolved organics), and 99,99 % of micro-organisms. Pre-treatment using ultrafiltration and granular activated carbon is in general necessary to prolong the life of the reverse osmosis membrane.

Usually the swimming pool backwash wastewater is stored in a buffer. By gravity or a pump this water is routed to the CD-system. The CD-system is equipped with reverse osmosis membranes. Possible residuals of chlorine are de-activated by the dosage of sodium bisulfite. Before entering the reverse osmosis stage suspended solids are removed by a small pre-filtering system. After reverse osmosis process the swimming pool backwash wastewater is separated in two fractions:

  • Permeate (ultrapure water, germ-free, adsorbable organic halogen compounds free, removal of dissolved salt up to 98 %)
  • Concentrate (contains the complete load of pollutants)

After chlorination the permeate (75 to 80 % of swimming pool backwash wastewater) is used as fill-up water for the pool and the concentrate (20 to 25 % of swimming pool backwash wastewater) is discharged to the sewer system.


  • Reduction of costs for freshwater supply and wastewater disposal (75 - 80 %)
  • Reduction of heating costs for recycled backwash wastewater
  • Reduction of chemicals for pH-value-correction
  • Pre-treatment by ultrafiltration is not necessary for CD-Systems
  • Germ-free and solid-free effluent
  • Partial desalination of bathing water cycle
  • Space saving due to compact design
  • Fully automated operation
  • Flexible localization due to modular design

INNOCHEM provides a method for the recycling of swimming pool backwash wastewater that is both efficient and highly economical. Payback time is often less than 3 years. The method can be implemented in new constructed plants or to retrofit existing plants.