Collection tank that allows solids to settle and be decomposed by anaerobic bacteria.

Treatment Level:  Primary
Relative Cost:
Amount of Maintenance Interaction:  low
Beneficial Byproduct:  little (compostable sludge)



Operation & Maintenance

Blackwater vs Graywater?

Secondary Treatment Options

  • Liquid (effluent): Drain fields(typical), soak pits, peat filters, treatment wetlands, aquaculture
  • Solids (sludge): Drying bed, windrow, off-site disposal

Additional Notes:

  • Need to locate in an area with easy access for inspection & maintenance
  • Holding tank is typically concrete, fiberglass, or plastic & is water tight
  • Best to have multiple chambers for cleaner effluent
  • Typically pump to secondary practice
  • Watch what you flush!  Minimize bleaches & chlorine, don’t use caustic products or drain cleaners as these things can kill the beneficial bacteria in the tank

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