13.2.2 Wastewater Treatment
There are three basic approaches toward reducing methane emissions from wastewater
treatment systems. If wastewater and sludge are stored and treated under aerobic
conditions, methane emissions can be virtually eliminated. Available technical
options include aerobic primary and secondary treatment, and land treatment.
However, it is to be noted that aerobic treatment of wastewater requires energy
input for aeration, which may result in off-site increases in greenhouse gas
emissions. Alternatively, wastewater can be treated under anaerobic conditions
and the generated methane can be captured and used as an energy source. Depending
on the amount of methane available, it can be used to heat the digestion tank,
as a fuel for other processes, or to generate electricity. Finally, in many
countries, attention is focused on reducing industrial waste generation, thereby
minimising the amount of wastewater requiring treatment.