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

by the catalytic activity of the hydrogen making enzyme. Earlier report exhibited

that biohydrogen production increased 1.59 times when FeSO4 concentration was

increased from 2.7 to 10.9 mg/l. Another study considered the effect of trace ele-

ments and the results confirmed that Na, Zn, Mg, and Fe were essential increment

to control the hydrogen production.

16.4.2

Hydraulic Retention Time (HRT) and Solid Retention Time (SRT)

Traditionally, several studies have utilized CSTRs in which HRT controls the micro-

bial growth rate and operational behavior of the structure. Therefore, HRT must be

larger than the highest growth rate of the microorganisms or else biomass washout

would be a possible risk by the dilution produced via uninterrupted volumetric flow.

However, membranes in AnMBR, compared to CSTR, offer solid–liquid segrega-

tion and can maintain the biomass in the system and thus approve decoupling of

HRT as well as SRT. Earlier studies reported that hydrogen-manufacturing rate was

enhanced in AnMBR as methanogenesis was prevented or ended by decreasing HRT.

Nevertheless, the specific biohydrogen production rate stayed unchanged. Currently,

it was reviewed that efficient biohydrogen generation from liquid waste streams

(wastewater) would be performed by means of the best possible HRT ranges from

0.5 to 12 hours [24].

16.4.3

Design of Biohydrogen-Producing Reactor

Design of reactor and its development is a key parameter in biohydrogen man-

ufacturing because it can change the microenvironment of the arrangement,

hydrodynamic performance, ascertaining microbial population, and their contact

with the substrate. The majority of studies used CSTRs as they supply perfect

mass transfer and get in touch with the microorganisms and the substrate. Many

researchers reported that on the whole biohydrogen manufacturing in AnMBR

under steady-state procedure slightly surpass that of CSTR [25].

16.4.4

Substrate Concentration

Saleem et al. investigated the influence of concentration of substrate on biohydro-

gen manufacturing in side–stream anaerobic dynamic membrane bioreactor. The

results confirmed that high influent chemical oxygen demand (COD) (above 30 g/l)

related to high organic loading rate (OLR) favored the build up of VFAs connected

to the prevention of biohydrogen generation. The steady hydrogen generation was

accomplished by functioning the system at low influent concentration of COD oper-

ating in the range of 10–30 g/l and at HRT of approximately one day. An additional

study was reported that steady increase in OLR from 4 to 22 g COD/l⋅day supported

the hydrogen manufacturing after that it decreased (20%). The results disclosed that

there is no widespread favorable OLR and it may vary with the exacting inoculum,

substrate, and nature of the system [16].