Overview of Anaerobic Biotechnology

Khanal, Samir Kumar

doi:10.1002/9780813804545.ch1

Cited by 23 publications

(18 citation statements)

References 25 publications

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“…Waste containing simple compounds such as sugar is readily degradable, requiring low HRT, whereas complex wastes, for example, chlorinated organic compounds, are slowly degradable and need longer HRT for their metabolism. SRT, on the other hand, controls the microbial mass in the reactor to achieve a given degree of waste stabilization (Khanal 2008). Thus, high retention times for complex wastes are due to the rate limiting hydrolysis step.…”

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

“…Anaerobic process may be classified as either anaerobic fermentation or anaerobic respiration depending on the type of electron acceptors (Khanal 2008). In an anaerobic fermentation process, organic matter is catabolized in the absence of an external electron acceptor by strict or facultative anaerobes through internally balanced oxidationreduction reactions under dark conditions (Chandra and Venkata Mohan 2011).…”

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

“…From both the waste treatment and resource recovery perspectives, it is important to examine some of the important factors that govern the anaerobic bioconversion process. These include organic loading rate, biomass yield, substrate utilization rate, hydraulic retention time (HRT) and solids retention time (SRT), start-up time, microbiology, environmental factors, and reactor configuration (Khanal 2008;Kim et al 2006;Demirel and Yenigun 2004;Fang and Yu 2000;Sanchez et al 2000;El-Mashad et al 2004;Bouallagui et al 2004;Sanchez et al 2005;Torkian et al 2003;Raposo et al 2006). Anaerobic processes are characterized by high volumetric organic loading rates (VOLRs) and high-rate anaerobic reactors such as the upflow anaerobic sludge blanket (UASB), anaerobic filter, and fluidized bed reactors are capable of treating wastewater at VOLR of 10-45 kg COD m -3 day -1…”

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

“…Biomass yield is a quantitative measure of cell growth in a system for a given substrate, and the biomass yield per mole of ATP totals 10.5 g volatile suspended solids (VSS) for both aerobic and anaerobic processes (Khanal 2008). However, when considering the metabolic processes of microorganisms, the total aerobic ATP generation is 38 mol, while the anaerobic ATP generation is only 4 mol ATP mol -1 glucose (Khanal 2008). These result in a significantly lower biomass yield for the anaerobic treatment process compared to the aerobic process.…”

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

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Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Mudhoo

Kumar

2013

Int. J. Environ. Sci. Technol.

217

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Heavy metals affect the biochemical reactions that take place during anaerobic digestion processes of organic matter. In this review, the different effects observed in anaerobic digestion processes and during the production of biomethane and biohydrogen from several substrates contaminated with and/or inheriting heavy metals from the substrates themselves were discussed. It has been found that heavy metals exert important roles in biochemical reactions. Heavy metals like copper, nickel, zinc, cadmium, chromium and lead have been overwhelmingly reported to be inhibitory and under certain conditions toxic in biochemical reactions depending on their concentrations. Heavy metals like iron may also exhibit stimulatory effects, but these effects have been scantily observed. This review also concludes that the severity of heavy metal inhibition depends upon factors like metal concentration in a soluble, ionic form in the solution, type of metal species, and amount and distribution of biomass in the digester or chain of biochemical reactions which constitute the anaerobic digestion process. A majority of studies have demonstrated that the toxic effect of heavy metals like chromium, cadmium and nickel is attributable to a disruption of enzyme function and structure by binding of the metal ions with thiol and other groups on protein molecules or by replacing naturally occurring metals in enzyme prosthetic groups. This review has not found published data on the effects of heavy metals on the hydrolysis stage of anaerobic digestion process chemistry, and hence further studies are required to depict any changes.

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Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

Section: Process Considerations In Anaerobic Biotechnologymentioning

confidence: 99%

See 2 more Smart Citations

Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Mudhoo

Kumar

2013

Int. J. Environ. Sci. Technol.

217

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“…Indeed, given 40 the low organic matter content of municipal wastewater (indicated by a chemical oxygen 41 demand (COD) of usually less than 500 mg/L), the thermal energy and physical footprint 42 required for anaerobic treatment can be excessive. Importantly, anaerobic treatment requires 43 a feed solution in excess of 1,000 mg COD/L to ensure system stability and process 44 efficiency (Khanal, 2009). An innovative approach to overcome the challenges associated 45 with the anaerobic treatment of municipal wastewater involves the initial pre-concentration of 46 organic matter prior to feeding the digester.…”

Section: Introduction 32mentioning

confidence: 99%

Factors governing the pre-concentration of wastewater using forward osmosis for subsequent resource recovery

Ansari

Hai

Guo

et al. 2016

Science of The Total Environment

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This study demonstrated a technique using forward osmosis (FO) to pre-concentrate the organic matter in raw wastewater, thereby transforming low strength wastewater into an anaerobically digestible solution. The chemical oxygen demand (COD) of raw wastewater was concentrated up to approximately eightfold at a water recovery of 90%. Thus, even low strength wastewater could be pre-concentrated by FO to the range suitable for biogas production via anaerobic treatment. Excessive salinity accumulation in pre-concentrated wastewater was successfully mitigated by adopting ionic organic draw solutes, namely, sodium acetate, and EDTA-2Na. These two draw solutes are also expected to benefit the digestibility of the pre-concentrated wastewater compared to the commonly used draw solute sodium chloride. Significant membrane fouling was observed when operating at 90% water recovery using raw wastewater. Nevertheless, membrane fouling was reversible and was effectively controlled by optimising the hydrodynamic conditions of the cross-flow FO system. Thus, even low strength wastewater could be pre-concentrated using FO to the range suitable 21 for biogas production via anaerobic treatment. Excessive salinity accumulation in pre-22 concentrated wastewater was successfully mitigated by adopting ionic organic draw solutes, 23 namely, sodium acetate and EDTA-2Na. These two draw solutes are also expected to benefit 24 the digestibility of the pre-concentrated wastewater compared to sodium chloride. Significant 25 membrane fouling was observed when operating at 90% water recovery using raw 26 wastewater. Nevertheless, membrane fouling was reversible and was effectively controlled by 27 optimising the hydrodynamic conditions of the cross-flow FO system. 28Keywords: forward osmosis (FO); wastewater; pre-concentration; ionic organic draw 29 solution; anaerobic digestion; membrane fouling. 30 31 3

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Elements of Sustainability and Bioremediation

Mudhoo

Mohee

2012

Bioremediation and Sustainability

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Overview of Anaerobic Biotechnology

Cited by 23 publications

References 25 publications

Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Factors governing the pre-concentration of wastewater using forward osmosis for subsequent resource recovery

Elements of Sustainability and Bioremediation

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