**6. MFC in dairy wastewater treatment**

The organic contents in wastewater make it a convenient substrate for MFC applications [32]. Various studies have shown that wastewaters from the dairy industry generate significantly less power as compared to the other wastewaters in MFC [33, 34]. Carbohydrates and proteins are among the main components of dairy wastewater. Their influence on the generation of power in MFC along with COD removal by using dairy wastewater as a substrate was mentioned by [35], and was reported that reduction in proteins and carbohydrates does not have a virtuous relation with power generation. The presence and elimination of antibiotics found in dairy wastewaters is a major problem. New technologies need to be employed to solve this problem. Researchers working with dairy wastewaters have concentrated on developing the MFC design that will boost the power generation (**Table 2**). Various surface modifications of the electrode material have improved MFC efficiency by increasing the power output [36].

MFCs are distinctive biofuel cells among the various bio-electrochemical systems that generate electricity by employing microorganisms [41]. For electricity production, hydrogen fuel and oxygen are utilized by the microbial fuel cell. Using bacteria as biocatalyst, MFC converts organic matter into electrical energy [42, 43]. An ideal MFC contains two chambers (cathode and anode), both separated

**105**

**Table 2.**

*Treatment of Dairy Wastewaters: Evaluating Microbial Fuel Cell Tools and Mechanism*

via a proton transfer membrane. The anode chamber consists of the electroactive microorganism, thereby making the chamber biotic whereas the cathode chamber remains abiotic. The available microorganisms in the anode chamber act as the biocatalysts, thereby leading to the degradation of organic matter in order to generate electrons that are transferred to the cathodic chamber via an electric circuit. The free electrons present on the cathode leads to the reduction of oxygen for processing

4H 4e O 2H O 2 2

4H 4e 2O 2H O 2 22

Considering glycerol as an electron donor and oxygen as a terminal electron

Anode : C H O 3H O 3CO 14H 14e 383 2 <sup>2</sup>

Cathode : 3O ½ O 14e 14H 7H O 2 2 <sup>2</sup>

In biological fuel cells, the catalyst is either an enzyme or the microorganisms as simple as Baker's yeast. Microbial fuel cells convert the chemical energy

**Anode Cathode**

Graphite coated SS anode

SS mesh anode with graphite coating

Plain graphite plates

> Graphitesprayed SS mesh

3D laminated composites

Carbon fiber brush

*Performance of different types of MFC using dairy wastewater as substrate (authors created).*

Overall : C H O 3O ½ O 3CO 4H O Biomass Electricity 383 2 2 2 2 ++ → + + + (5)

**System configuration %COD** 

Plain graphite plates

> Graphitesprayed SS mesh

3D laminated composites

> Platinum/ carbon

acceptor, the following reactions occurring in MFCs, shown in Eqs. (3-5).

+ − + +→ (1)

+ − ++ → (2)

+ − +→++ (3)

− + + ++ → (4)

**removal**

Carbon cloth 91% 20.2 W/m3 [36]

Carbon cloth 80% 27 W/m3 [37]

**Maximum surface/volume power density**

91% 3.2 W/m3 [8]

91% 5.15 W/m3 [38]

81% 122 W/m3 [39]

NA 1056 mw/m2 [40]

**Refs.**

*DOI: http://dx.doi.org/10.5772/intechopen.93911*

of water as shown in Eqs. (1) and (2).

Or

**S. no. Types of** 

1. Single

2. Single

3. Dual-

4. Dual-

5. Dual-

6. Dual-

**MFC**

chamber MFC

chamber MFC

chamber MFCs

chamber MFCs

chamber MFCs

chamber MFCs

*Treatment of Dairy Wastewaters: Evaluating Microbial Fuel Cell Tools and Mechanism DOI: http://dx.doi.org/10.5772/intechopen.93911*

via a proton transfer membrane. The anode chamber consists of the electroactive microorganism, thereby making the chamber biotic whereas the cathode chamber remains abiotic. The available microorganisms in the anode chamber act as the biocatalysts, thereby leading to the degradation of organic matter in order to generate electrons that are transferred to the cathodic chamber via an electric circuit. The free electrons present on the cathode leads to the reduction of oxygen for processing of water as shown in Eqs. (1) and (2).

$$\text{4H}^+ + \text{4e}^- + \text{O}\_2 \rightarrow \text{2H}\_2\text{O} \tag{1}$$

Or

*Environmental Issues and Sustainable Development*

**5.1 Physio-chemical process**

*5.1.1 Electrocoagulation (EC)*

*5.1.2 Adsorption*

*5.1.3 Membrane treatment*

can be used directly [31].

**6. MFC in dairy wastewater treatment**

ciency by increasing the power output [36].

removal of suspended colloidal particles.

and some inorganic contents. 6% of the organic load can be converted into biogas from the wastewater and the rest can be used for cell growth and maintenance. The process reactors are shielded to avoid air obstruction and the release of odors [30].

The electrocoagulation (EC) method could be the alternative treatment option for dairy wastes. Electrocoagulation is an electrolysis process that uses specific electrodes by transferring electrical current via the effluent to extract dissolved organic waste, turbidity, and coloring matter. The method assists in the substantial

Adsorption was found beneficial among the various physio-chemical treatment methods for removing organic compounds in wastewaters. Activated carbon is mainly used in treating wastewater, among other types of adsorbent materials. Although certain additional adsorbents can also be used to treat streams of wastewater and are

Microfiltration, nanofiltration, ultrafiltration, reverse osmosis, and electrodialysis are typical membrane separation processes. Highly feasible product recovery is possible using these methods and the effluent generated is of high quality which

The organic contents in wastewater make it a convenient substrate for MFC applications [32]. Various studies have shown that wastewaters from the dairy industry generate significantly less power as compared to the other wastewaters in MFC [33, 34]. Carbohydrates and proteins are among the main components of dairy wastewater. Their influence on the generation of power in MFC along with COD removal by using dairy wastewater as a substrate was mentioned by [35], and was reported that reduction in proteins and carbohydrates does not have a virtuous relation with power generation. The presence and elimination of antibiotics found in dairy wastewaters is a major problem. New technologies need to be employed to solve this problem. Researchers working with dairy wastewaters have concentrated on developing the MFC design that will boost the power generation (**Table 2**). Various surface modifications of the electrode material have improved MFC effi-

MFCs are distinctive biofuel cells among the various bio-electrochemical systems that generate electricity by employing microorganisms [41]. For electricity production, hydrogen fuel and oxygen are utilized by the microbial fuel cell. Using bacteria as biocatalyst, MFC converts organic matter into electrical energy [42, 43]. An ideal MFC contains two chambers (cathode and anode), both separated

cost-effective as well. For instance rice husk ash, coal fly ash, etc. [31].

**5. Advanced technologies for the treatment of dairy effluent**

**104**

$$\text{4H}^\* + \text{4e}^- + \text{2O}\_2 \rightarrow \text{2H}\_2\text{O}\_2 \tag{2}$$

Considering glycerol as an electron donor and oxygen as a terminal electron acceptor, the following reactions occurring in MFCs, shown in Eqs. (3-5).

$$\text{Anode}: \text{C}\_3\text{H}\_8\text{O}\_3 + \text{3H}\_2\text{O} \rightarrow \text{3CO}\_2 + \text{14H}^+ + \text{14e}^- \tag{3}$$

$$\text{Cathode:}\,\text{:}\,\text{SO}\_2 + \%\text{O}\_2 + \text{14e}^- + \text{14H}^+ \rightarrow \text{7H}\_2\text{O}\tag{4}$$

$$\text{Overall:}\,\mathrm{C}\_{3}\mathrm{H}\_{8}\mathrm{O}\_{3} + \mathrm{\mathcal{O}}\mathrm{O}\_{2} + \mathrm{\mathcal{H}}\mathrm{O}\_{2} \rightarrow \mathrm{\mathcal{G}}\mathrm{CO}\_{2} + 4\mathrm{H}\_{2}\mathrm{O} + \text{Biomass} + \text{Electricity} \quad \text{(5)}$$


In biological fuel cells, the catalyst is either an enzyme or the microorganisms as simple as Baker's yeast. Microbial fuel cells convert the chemical energy

**Table 2.**

*Performance of different types of MFC using dairy wastewater as substrate (authors created).*

of carbohydrates present in the substrate, such as alcohol and sugars directly into electrical energy. Currently, efforts have been made towards using MFCs for domestic wastewater treatment and at the same time point, electricity production considering the environmental issues and further reuse of waste [44]. Sewage sludge of anaerobic nature is used to inoculate MFCs, as it is conveniently used from a wastewater treatment plant and it has largely diverse bacterial communities containing electrogenic bacterial strains [45]. MFCs have functional and operational benefits compared with the presently used technologies for producing energy from organic content [46].
