Anaerobic wastewater treatment is the biological treatment of wastewater without the use of air or elemental oxygen. In anaerobic treatment organic pollutants are converted by anaerobic microorganisms to a gaseous product that has the potential for reuse.

Effectively in Anaerobic treatment, the COD in wastewater is mostly converted to methane gas and unlike aerobic processes, very little energy is required and very little sludge is produced.
 
Anaerobic processes are most value in high organic loadings. In pulp and paper industry anaerobic processes is mostly found for treating the effluent OCC mills. An anaerobic process is usually followed by aerobic treatment to reduce the dissolved organics to very low levels.
 
The most basic anaerobic process is a lagoon with either a natural or synthetic cover. Such systems have been in use for decades are operating quite effectively when plenty of space is available. At sites where space is an issue high rate anaerobic treatment systems are favored.
 
In a high rate anaerobic treatment system the anaerobic bacteria are maintained in a comparatively small vessels and in high concentrations thus increasing the effective sludge retention time and allowing sludge to be more effectively retained.
 
EWT has extensive experience in anaerobic processes for most industrial wastewaters.