215
Anaerobic Digestion of Aqueous Waste for Methane and Hydrogen
rapeseed meal by the extraction process, the possible biogas production
from rapeseed cake decreased. Pretreatment (thermal and chemical) of
sunflower and rapeseed residues did not enhance the methane yield.
4. Washing water from biodiesel production is a good candidate for anaerobic
degradation due to its high content of biodegradable organic substances.
5. Specific inhibition effects resulting from the substrate composition should
be considered during anaerobic treatment of biodiesel byproducts. In the
case of anaerobic digestion of crude glycerol, high salinity of the substrates
may negatively affect the methanogenic microorganisms. The concentration of ammonium should also be monitored. Since nitrogen is an essential
nutrient for microorganisms, its low concentration in the crude glycerol
and washing water has to be compensated by the ammonium supplement.
However, nitrogen-rich substances have high concentration in rapeseed
cake, which may cause ammonium accumulation in the reactor, thereby
inhibiting the digestion process.
The use of byproducts of the biodiesel process as a potential source of energy producer
makes the process of biodiesel more economically attractive.
8.4.6 PAlm oil mill eFFluenT
Yusoff et al. [61] examined the effects of HRT and volatile fatty acids produced during fermentation on biohydrogen production from palm oil mill effluent. Both HRT
and volatile fatty acid concentration played a vital role in the biohydrogen concentration, rate, and yield. The results were obtained for HRT of two, three, and five days,
and two days gave the optimum operation with a maximum biohydrogen yield, rate,
and concentration of 30%. The VFA as soluble metabolites reduced the amount of
biohydrogen production by 8%–10%. The study concluded that HRT and VFA affect
the biohydrogen production and should be considered in biohydrogen fermentation.
8.4.7 lCFAS in WASTeWATer
As shown in Table 8.1 [5,92], the potential for biogas and methane production from lipids is much higher than that from proteins and carbohydrates. LCFAs commonly found
in wastewaters include lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic
acid, oleic acid, and linoleic acid among others [72]. An extensive number of studies for
the treatment of wastewater containing lipids and LCFAs in different types of anaerobic
reactors have been reported. These studies are evaluated by Alves et al. [72].
The high-rate anaerobic technology (HR-AnWT) for the wastewater treatment
requires the expansion of suitable substrates, in particular better treatment of the wastewater with high-lipid content. Waste lipids are good candidates for substrates needed
to improve biogas and methane production, compared to proteins and carbohydrates.
Alves et al. [72] presented a review of how LCFA degradation is accomplished by
syntrophic communities of anaerobic bacteria and methanogenic archaea. For optimal
performance, these syntrophic communities need to be clustered in compact aggregate, which is often difficult to achieve with wastewater that contains fats and lipids.
Anaerobic Digestion of Aqueous Waste for Methane and Hydrogen
rapeseed meal by the extraction process, the possible biogas production
from rapeseed cake decreased. Pretreatment (thermal and chemical) of
sunflower and rapeseed residues did not enhance the methane yield.
4. Washing water from biodiesel production is a good candidate for anaerobic
degradation due to its high content of biodegradable organic substances.
5. Specific inhibition effects resulting from the substrate composition should
be considered during anaerobic treatment of biodiesel byproducts. In the
case of anaerobic digestion of crude glycerol, high salinity of the substrates
may negatively affect the methanogenic microorganisms. The concentration of ammonium should also be monitored. Since nitrogen is an essential
nutrient for microorganisms, its low concentration in the crude glycerol
and washing water has to be compensated by the ammonium supplement.
However, nitrogen-rich substances have high concentration in rapeseed
cake, which may cause ammonium accumulation in the reactor, thereby
inhibiting the digestion process.
The use of byproducts of the biodiesel process as a potential source of energy producer
makes the process of biodiesel more economically attractive.
8.4.6 PAlm oil mill eFFluenT
Yusoff et al. [61] examined the effects of HRT and volatile fatty acids produced during fermentation on biohydrogen production from palm oil mill effluent. Both HRT
and volatile fatty acid concentration played a vital role in the biohydrogen concentration, rate, and yield. The results were obtained for HRT of two, three, and five days,
and two days gave the optimum operation with a maximum biohydrogen yield, rate,
and concentration of 30%. The VFA as soluble metabolites reduced the amount of
biohydrogen production by 8%–10%. The study concluded that HRT and VFA affect
the biohydrogen production and should be considered in biohydrogen fermentation.
8.4.7 lCFAS in WASTeWATer
As shown in Table 8.1 [5,92], the potential for biogas and methane production from lipids is much higher than that from proteins and carbohydrates. LCFAs commonly found
in wastewaters include lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic
acid, oleic acid, and linoleic acid among others [72]. An extensive number of studies for
the treatment of wastewater containing lipids and LCFAs in different types of anaerobic
reactors have been reported. These studies are evaluated by Alves et al. [72].
The high-rate anaerobic technology (HR-AnWT) for the wastewater treatment
requires the expansion of suitable substrates, in particular better treatment of the wastewater with high-lipid content. Waste lipids are good candidates for substrates needed
to improve biogas and methane production, compared to proteins and carbohydrates.
Alves et al. [72] presented a review of how LCFA degradation is accomplished by
syntrophic communities of anaerobic bacteria and methanogenic archaea. For optimal
performance, these syntrophic communities need to be clustered in compact aggregate, which is often difficult to achieve with wastewater that contains fats and lipids.