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.
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