Biomedical Engineering Reference
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MFC system, the maximum removal rates of COD, NH
4
+
-N, and TN reached 98.8,
97.4, and 97.3% respectively, accompanied by a power output of 14 W/m
3
in the
oxic-biocathode MFC and 7.2 W/m
3
in the other MFC.
3.1.3 Practical Wastewater Treatment
Inspired by the hope of simultaneous pollutant removal and energy recovery in
practical systems, MFC setups have also been incorporated into various conven-
tional anaerobic/aerobic processes for practical wastewater treatment. The effec-
tiveness of MFCs for treating beer brewery wastewater was first demonstrated by
Feng et al. [
95
] using an air-cathode MFC, which achieved a power density of up
to 528 mW/m
2
(normalized to anode surface) and COD removal of 87-98%
depending on the influent COD concentration. The suitability of brewery waste-
water as the substrate for MFC was also recently shown in a continuous-operation
MFC [
96
], with a maximum power density of 24.1 W/m
3
obtained. Huang et al.
[
97
] investigated the performance of an MFC for treatment of paper recycling
plant wastewater, which contained both soluble organics and refractory particulate
matter such as cellulose. The SCOD and TCOD removal reached 73% and 76%
respectively, and the cellulose was almost completely degraded. The researchers
recently developed another efficient MFC system by integrating an MFC with the
electro-oxidation process for coking wastewater treatment [
98
]. Driven by the
electro-oxidation reactions, the removal rates of TCOD and TN reached 82% and
68% respectively, which present an approximately 30% improvement in both
indexes over a pure MFC system. Zhang et al. [
99
] used an upflow air-cathode
MFC to treat landfill leachates, which had a complex composition of dissolved
organic matter, inorganic macro-components, heavy metals, and xenobiotic
compounds. Despite the highly recalcitrant property of such wastewater, a
considerable removal of COD and NH
4
+
-N and a maximum power density of
12.8 W/m
3
were obtained in this system, suggesting a good capability of MFCs for
pollutant removal.
Another commonly-cited advantage of MFCs for wastewater treatment is their
capability to offset, at least partially, the energy consumption of conventional
activated sludge processes. This has been experimentally shown by several studies
[
5
,
100
]. In an attempt to reduce operating cost, Liu et al. [
5
] managed to integrate
an MFC into a sequencing batch reactor (SBR) system for enhanced COD removal
and power generation. In this SBR-MFC system, the MFC accounted for 12% of
the reactor volume but contributed to 18.7% of the total COD removal, while a
maximum power density of 2.34 W/m
3
was achieved, suggesting a good possi-
bility for enhancing the performance and economics of existing activated sludge
processes.
In addition to direct organic degradation, MFCs could also be employed as a
post-treatment step for anaerobic digestion. On the one hand, these effluents often
contain volatile fatty acids (VFAs) that require further treatment to meet the
discharge standard. On the other, MFCs have good capability to utilize VFAs for
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