The main function of a sewage treatment is to minimize the harmful effects that the sewage water
will give to the natural water environment in which it is discharged. The most energy-consuming
process in a sewage treatment is the stabilization of the wastewater sludge. Despite high energy
consumption, sewage sludge has the potential to become a renewable energy source at the same
time. Biogas produced as a result of the anaerobic digestion process in which the sludge is stabilized
in sewage treatment facilities can be used to meet the auxiliary heat and power needs of the facility
in a great extent. Thus, the sewage treatment facilities which are in a position where energy can not
only be consumed but can also be produced at the same time, have enormous potential due to
balancing of energy expenditure and structures compatible with the concept of sustainability.
In this study, an actual municipal sewage treatment facility is assessed in terms of auxiliary heat and
power production potentials. The facility consists of six subsytems for treatment purposes: Primary
treatment, secondary treatment, flotation and thickening system, anaerobic digestion system,
biogas engine driven cogeneration system and sludge dewatering system. The total electricity
consumption of these subsytems except cogeneration is found to be 2083.73 kWh. The cogeneration
system generates 1600 kWh electricity by two dual-fuel gas engines using biogas obtained from
anaerobic sludge digestion process. For further power production to meet the auxiliary power needs
of the treatment facility, a scenario is developed based on the combustion of stabilized sludge in an
incineration plant. A gas turbine is installed at the exhaust of the incineration plant to produce 1000
kWh electricity, which makes the total production 2600 kWh and meets the all power needs of the
auxiliary processes in the facility.