Passive Treatment Systems


Earth Systems Water’s specialist expertise in water chemistry and understanding of passive treatment systems means we can design, scale and implement appropriate low-cost passive water treatment systems for long term applications.

Passive Water Treatment Systems are engineered treatment systems that do not require the ongoing addition of chemical reagents to conduct treatment. As a result these systems;

  • Have low running and maintenance costs,
  • Are long term treatment options, and
  • Require minimal supervision.

These systems rely on installed chemical and biological process for treatment and their use and effectiveness is therefore restricted. As a consequence they should not be considered a walk away solution. However if used appropriately they can have a positive effect on water quality for a minimal cost.

They are ideally suited to the treatment of water with low acid, pollutant and suspended particle loads. An understanding of the inflow water chemistry is required to correctly design and scale the system to achieve the desired final water quality. Incorrectly scaled systems can result in poor effluent water quality or very limited treatment system life expectancy due to precipitates and armouring of installed reactive materials (eg. limestone).

Passive Treatment Systems include:

  • Oxic Limestone Drains (OLD)
  • Anoxic Limestone Drains (ALD)
  • Limestone Diversion Wells (LDW)
  • Reducing and Alkalinity Producing Systems (RAPS)
  • Successive Alaklinity Producing Systems (SAPS)
  • Alkalinity Ponds
  • Pyrolusite Limestone Beds (PLB)
  • Caustic Magnesia – Semi Passive Systems
  • Aerobic / Anaerobic Wetlands
  • Inert Atmosphere Systems
  • Vertical Flow Wetlands (VFW)
  • Permeable Reactive Barriers (PRB)
  • Slag Leach Beds (SLB)
  • Microbial Reactor Systems (MRS)
  • Alkalinity Producing Covers
  • In-situ Limestone Slurry Injection
Open Limestone Drain
Vertical Flow Wetland 3

Passive Treatment Systems can be used for:

  • Storm water runoff,
  • Long term treatment of low acid, pollutant and sediment load run-off,
  • Landfill leachate treatment,
  • As a final polishing step for effluent from a fixed plant (active) treatment system,
  • Turbidity reduction,
  • Phosphate, Nitrate and Ammonia reduction and control,
  • Treatment of some types of acid drainage seepage,
  • Sulfate removal.
Constructing Passive System
Vertical Flow 1

Contact Earth Systems for more information on the suitability of Passive Water Treatment Systems for your particular application.