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16 Bioreactors for the Production of Industrial Chemicals and Bioenergy Recovery from Waste

has to be done to balance the oxidation–reduction state, consequently in a lower

yield of biohydrogen [13]:

C6H12O6 + NAD⁺ →2CH3COCOOH + 2NADH + 2H⁺

(16.1)

Two directions can be established to outline molecular hydrogen production in

the presence of appropriate co-enzymes, for example, either by the re-oxidation of

NADH path or by formic acid disintegration pathway which could be represented

by Eqs. (16.2) and (16.3):

NADH + H⁺ + 2Fd²⁺ →2H⁺ + NAD⁺ + 2Fd⁺

(16.2)

2Fd⁺ + 2H⁺ →2Fd²⁺ + H2

(16.3)

16.3

Overview of Anaerobic Membrane Bioreactors

AnMBR technology is an excellent technology to control pollution because of its

lesser carbon foot print, while generating higher effluent (permeate) qualities

than conventional treatment practices. It is a combined method where membrane

element is attached with an anaerobic bioreactor [13, 17]. Membranes can remove

liquid from biomass and can preserve biomass efficiently in the bioreactor, thus

allowing the long SRT necessary for effective treatment, while permitting action at

the short HRT required for cost-effectiveness. It also gives possible benefits for the

bioprocesses where product formation and separation are required concurrently in

a compressed method [17]. Despite the applications, AnMBR configurations can be

characterized as submerged/immersed and exterior/side stream (Figure 16.3a,b). In

the previous case, membranes are immersed in the liquid state of biological reactor

or sometime submerged in a different reactor. In side stream structure, liquid

filtration membrane is connected to the bioreactor externally in a different unit

requiring a transitional pump step. Every design has positive and negative features

and, the attainable value of tetra-methyl pyrazine (TMP) is unlike and route of flow

is reverted. Higher TMP in side stream plan directed to diminish the substitute

area required for a particular filter through flux and enhance the claim of operation

energy. On the contrary, the maintenance and changing of membranes is effortless

in this configuration. Even though, submerged AnMBRs are less energy-intensive,

but well-established membrane surface area is requisite to deal with high permeate

fluxes [13, 16].

16.3.1

Challenges and Opportunities

16.3.1.1

Membrane Fouling and Energy Demands

Due to deposition of foulant materials, membrane fouling arise on the outside of

membrane and/or inside pore matrix which is a challenge within AnMBRs because

it worsens membrane permeability, thus demanding chemical cleaning which can

curtail membrane life time [17, 18]. A range of diverse foulants like particulates,

organics, colloids, microbes, and microbial byproducts, inorganics, and amalgama-

tion with thereof will cause fouling. Fouling naturally influences the economy of