Leachate Systems

Aeration Lagoons

 An aerated lagoon is a treatment pond that is provided with mechanical aeration that introduces oxygen into the pond in order to promote the biological oxidation of the leachate. Operators utilise oxygen and microbial action in lagoons to treat the pollutants in the leachate. Oxygenation can be provided by mechanical surface aerators of submerged pipework systems. Lagoon depths can typically range from 3m to 5m. Ponds have historically been used to provide long retention times (greater than 150 days) for different types of wastewater to be stabilised through natural processes. In many cases of leachate treatment, such holding times are not possible because of the limited availability of land. Leachate would be treated by the action of bacteria (both aerobic and anaerobic), algae, other micro and macro organisms, and by the physical process of gravity settling. When properly designed, ponds are capable of providing secondary treatment for both BOD and suspended solids. Pond depths range from 1m to 2m. Anaerobic ponds wold typically be more than 3m deep, have no dissolved oxygen, and use anaerobic bacteria to treat organic material. They provide low cost treatment of high strength organic wastes. They are typically used by industries to pre-treat wastewater, and are followed by aerobic treatment. They can also be fitted with a floating cover to contain odours, collect methane gas and retain heat. In any leachate treatment pond, treatment is accomplished by a complex community of organisms. They work in an interaction with each other which is mutually beneficial. Algae, like all green growing matter, use nutrients and carbon dioxide in the presence of sunlight to produce oxygen in a process called photosynthesis. The oxygen produced is used by bacteria to break down organic matter into simpler materials, releasing carbon dioxide to be used by the algae. Breaking down organic material reduces BOD.


  • Low construction cost
  • Low operational cost
  • Low energy usage
  • Can accept surge loadings
  • Low chemical usage
  • Fewer mechanical problems
  • Easy operation
  • No continuous sludge handling


  • Significant land requirements
  • Possible groundwater contamination from leakage
  • Climatic conditions affect treatment
  • Possible suspended solids problem (algae)
  • Possible spring odour problems (after ice-melt)
  • Animal problems (rats, birds, etc.)
  • Vegetation problems (rooted weeds, duckweed, algae)
  • Periodic, labour intensive and costly sludge removal