Compost Filters and Filter Bags

Collection of wastewater in storage chambers or filter bags designed to drain liquids away so that solids can be aerobically composted.

Treatment Level:  Primary
Relative Cost:
  low – medium
Amount of Maintenance Interaction:  high
Beneficial Byproduct:  some – lots (compost)


  • No unpleasant odors or gases.
  • Produces nutrient rich compost for reuse or sale.
  • Excellent in combination with aquaculture.


  • Weekly interaction needed to add bulking agents.
  • May clog if overloaded, unmanaged, or if the wrong bags are used.
  • Maintenance person may see excrement when adding the bulking agent.

Operation & Maintenance

  • Add bulking agents such as straw, wood chips/sawdust, or dry leaves weekly – monthly depending on loading.
  • Switch feeder pipe between 2 chambers/bags based on volume of chamber (typ. 6 – 12 months)
  • Unfed chamber/bag is left to compost for 6 – 12 months, then added to secondary practice.

Blackwater vs Graywater?

  • Can treat both in combination, but filter bags are best suited to blackwater systems to decrease the risk of washing out solids.

Secondary Treatment Options

Additional Notes:

  • Need to locate in an area with easy access for maintenance and compost removal.

Compost Filter Bag (Rottebehalter)