Introduction: of the sludge, the organic matter


Municipal Waste Water Treatment Plant is one of the prominent events in
the world in order to preserve the environment. Nevertheless, the activated
sludge processes make this as a highly expansive activity to treat the waste
water with current regulations and requirements. Although, the technologies
such as Development of bioreactor, Aerobic granular sludge systems are arrived,
there is no any significant changes. But, it is believed that the anaerobic
technology can be a significant solution for this major issue. The anaerobic
technology has been used for the treatment of industrial waste water and sludge
treatment also. The anaerobic condition produces microorganisms and biogas,
which can be utilised for the treatment of sludge and energy requirement of
plant respectively. The digested sludge by anaerobic microorganisms can be used
for the land applications. Although, this sludge production can improve the
economy rate, the organic matter in the sewage sludge is very less as large
quantity of organic matters are accumulated in the water. Hence, in order to
enhance the strength of the sludge, the organic matter has to be extracted from
water to the sludge as per side stream technology or the Mainline treatment
(Direct treatment of low strength water anaerobically) should be followed.
Despite, the Side stream sludge treatment is used since many years, some of the
advanced technologies are required to enhance the organic matter in the sludge
and efficiency of the sludge separation process. Also, the mainline treatment
requires plenty of microorganisms. Municipal waste water’s higher temperature,
lower organic strength etc. are not giving a suitable condition for the growth
of methanogens. Hence, the ordinary anaerobic bioreactors such as Up-flow
Anaerobic Sludge Blanket (UASB), Expanded Granular Sludge Bed (EGSB) are not
providing higher amount of biomass and washing out them. Therefore, this paper
emphasising the following energy producing Anaerobic technologies and their
challenges for Municipal Waste Water Treatment such as Enhanced side stream
anaerobic sludge digestion, Anaerobic Membrane Bioreactor and Microbial
electrochemical system.

side-stream anaerobic sludge digestion:

This is very economical method and almost similar to the regular
treatment plants but based on the more anaerobic technology instead of aerobic system
for the degradation of organic matter. There are two main tasks in this
process. Firstly, to enhance the concentration of organic matter in the sludge
with very less consumption of energy. Secondly, large amount of anaerobic
digestion of the carbon imposed sludge in order to produce biogas with high
energy. Basically, it is believed that when the anaerobic digestion od sludge
is biomass is consisting massive carbon content, the bio concentration of
organic matter can be achieved automatically. These processes have been done
successfully by many treatment plants such as Strass WWTP in Austria. However, in
this process, the energy consumption is quite higher due to lethargic
solubilisation of the organic matter. Hence, few pre-treatments are required
for this process such as hydrothermal, microwave irradiation, chemical and
biological treatments etc. in order to make the microorganisms feasible to
utilize the sludge. But, all the methods are consuming higher energy.
Nevertheless, the thermal hydrolysis method can utilize very less energy which
is produced by the plant’s heat pumps. The minimal in situ energy by this
process along with the separated sludge will require very less or even zero heat
energy for the whole process compared to massive sludge amount in the
conventional methods. However, the predetermined process will be depending on
the sludge properties, bio concentration level etc. This progress is achieved
exactly by the Blue plains WWTP in the United States. In this plant, they
follow the same Strass WWTP’s anaerobic side stream technology but along with
the Cambi Thermal Hydrolysis process for lifting the solubility of the biomass.
This idea enhances the production of methane twice while compared to the
ordinary sludge digestion processes.

Another problem faced by the plants are less organic contents and uneven
sludge, which reduces the production of methane. Provision of organic rich food
waste along with the obtained sludge can provide a solution for this issue.
This method raises the carbon content availability along with the higher yield
of biogas. Furthermore, this method can reduce the bioreactor investment and
the maintenance cost. This idea has been provided in Strass plant over 8 years.


the side stream anaerobic biotechnology is implemented in treatment plants, it
has few technological and economical defects in it. Firstly, the bio
concentration process consumes small amount of oxygen anyway, and few organic
matters are wasted. Secondly, the sludge less holding process may decrease the
stability of the sludge. Hence, in order to avoid the washing out of sludge,
the sludge thickening by coagulation process is required. Otherwise, membrane
should be installed for avoiding the washout. Finally, the anaerobic digester
and pre-treatment devices lead to higher cost and highly corrosive.