Environmental Engineering Reference
In-Depth Information
has been demonstrated, and quite often to levels approaching 90% or more [58], the
research to demonstrate the ability to clean the water sufficiently to enable reuse
has been very limited. A recent publication proposed use of the MFC technology to
enable recycle of water in a biorefinery via application of MFCs to remove byprod-
ucts and other contaminants accumulating in the process [58]. The potential for
water reuse in the food industry has been considered, although not via implementa-
tion of the MFC technology [58]. Typical processes investigated for water cleanup
to enable reuse have been a combination of filtration and disinfection. The water
streams considered for reuse are mostly low organic carbon containing streams
such as cooling water, condensate, chiller water and wash water. Removal of any
organic carbon present in the water has been via use of diatomaceous earth filters
(soluble as well as insoluble matter) and micro- or ultra-filtration (for particulate
matter). The potential for water recycle (i.e., use of cleaned wastewater in a different
operation but within the same industry), is greater than the potential for reuse. The
consideration of MFCs for wastewater clean-up can potentially open the door for
many other streams containing higher levels of organic carbon (
500-5000 mg/L).
Water reuse in the food industry requires careful consideration of the microbiolog-
ical safety aspects and related regulatory, technological and economic factors [35].
Any use of MFCs for this application has to be done using non-hazardous microor-
ganisms. One of the characteristics of exoelectrogenic anodic microorganisms used
in MFCs is their tendency to form biofilms, which can minimize but not eliminate
the presence of microorganisms in effluents from the MFCs. Recent changes in the
guidelines for water reuse in the food industry [36] may allow consideration of
emerging technologies such as MFCs for wastewater cleanup.
5.4 Conclusions
The food industry wastewaters contain significant amount of easily degradable
organic carbon which can be used for energy production. MFCs offer a potential
solution for treatment of low BOD wastewaters. MFCs can produce electricity in
the range of 2-260 kWh/ton of product from the wastewater used for processing
the food products, depending on the BOD and volume of water used in the process.
A total of 46 MW of power can potentially be produced from wastewaters from
milk dairy farms (low BOD wastewater) in the US. In comparison, up to 1960 MW
of electricity can be produced from high BOD wastewater from the dairy industry.
Hydrogen is an alternate form of energy that can be produced using bioelectrochem-
ical cells from the food industry wastewaters with potential for generation of 2-270
m 3 /ton of the food product. Application of MFCs for treatment of food processing
wastewaters requires further investigations into electrode design, materials, liquid
flow management, organic loading and scale-up to enable high power densities at
commercial scale.
Our experimental study investigating treatment of milk dairy wastewater demon-
strated electricity production of 54 W/m 3 from wastewater using an MFC system.
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