Environmental Engineering Reference
In-Depth Information
presence of organic matter that may not be easily degraded by the microbial con-
sortia used in the studies. Typically, the studies have used consortia enriched using
model substrates such as glucose or acetate. These consortia may not contain organ-
isms capable of degrading complex organic matter at sufficient levels. The study by
Lu et al. [39] demonstrated that the use of microorganisms in the wastewater itself,
which are potentially pre-enriched in degrading the complex organic matter leads
to high COD removal (96-98%). Control of oxygen leakage into the system, and
methanogenesis can lead to CEs of 50% or higher for food processing wastewaters.
The relative importance of oxygen leakage vs. methanogenesis is not very well stud-
ied for food industry wastewaters, and further work is needed in understanding these
effects.
5.3.5.2 Potential for Enabling Higher Power Densities
and Practical Applications
The range of power densities obtained in MFCs processing industrial wastewaters
relevant to the food industry are shown in Table 5.2. Assessment of the commercial
feasibility of MFCs has revealed that the power densities need to be in the range
of 400-1000 W/m
3
for application consideration [21, 22]. MFCs with power den-
sities approaching this range have been reported, but mostly with model soluble
substrates [12, 23, 48-50]. The power densities for MFCs fed with insoluble sub-
strates are lower compared to those with soluble substrates. Thus, accessibility to
the solid substrate is an issue and requires novel designs to improve their conver-
sion. Since food industry wastewaters contain a significant amount of soluble sugars
and organic acids, the potential for application of MFCs for deriving energy from
Table 5.2
Power densities reported in MFCs processing wastewaters
Power density
mW/m
2
W/m
3
Type of wastewater
Primary substrate
MFC description
Reference
Starch processing
Starch
Carbon paper
electrodes with
Nafion 117
membrane
239
14
[39]
Synthetic wastewater Starch, peptone, and
fish extract
Stackable
cartridge-type
MFC
899
129
[42]
Cereal-processing
Complex organic
matter
Two-chamber MFC
81
8.8
[25]
Cereal-processing
Fermented
wastewater
One-chambered
MFC
371
13.4
[25]
Paper processing
Cellulose
Two-chamber MFC
100
0.6
[59]
Dairy processing
Soluble components
from wastewater
1.27 cm thick carbon
felt anode with
air-cathode
690
54
This study
