R. Yukesh Kannah

Combined thermo-chemo-sonic disintegration of waste activated sludge for biogas production

In the present study, there was an investigation about the impact of a new combined thermo-chemo-sonic disintegration of waste activated sludge (WAS) on biodegradability. The outcome of sludge disintegration reveals that maximum Suspended Solids (SS) reduction and Chemical Oxygen Demand (COD) solubilization effectuated at a specific energy input of 5290.5kJ/kgTS, and was found to be 20%, 16.4%, 15% and 27%, 22%, and 20%, respectively for the three alkalis (NaOH, KOH, and Ca(OH)2). The conversion coefficient of the Volatile Suspended Solids (VSS) to product Soluble COD (SCOD), calculated by nonlinear regression modeling, was found to be 0.5530gSCOD/gVSS, 0.4587gSCOD/gVSS, and 0.4195gSCOD/gVSS for NaOH, KOH, and Ca(OH)2, respectively. In the biodegradability studies, the parameter evaluation provides an estimate of parameter uncertainty and correlation, and elucidates that there is no significant difference in biodegradability (0.413gCOD/gCOD, 0.367gCOD/gCOD, and 0.342gCOD/gCOD) for three alkalis (NaOH, KOH, and Ca(OH)2).

Synergetic effect of combined pretreatment for energy efficient biogas generation

Physiochemical disintegration of waste activated biosolids (WAB) through thermochemical (TC) pretreatment requires high energy and cost for efficient energy generation. Therefore in the present study, an attempt has been made to enhance the biodegrdability and to minimize the operational cost of TC pretreatment by combining it with ozonation. A higher solubilization of about 30.4% was achieved at lesser energy input of about 141.02kJ/kgTS and a ozone dosage of about 0.0012mgO3/mgSS through this combined thermo chemo ozone (TCO3) pretreatment. The methane production potential (0.32gCOD/gCOD) of TCO3 pretreatment was comparatively higher than the (0.19gCOD/gCOD) TC pretreatment. The energetic analysis and economic assessment of the proposed method of pretreatment can possibly reduces the energy requirement of TC pretreatment with a positive net profit of about 35.49

Dispersion induced ozone pretreatment of waste activated biosolids: Arriving biomethanation modelling parameters, energetic and cost assessment

/ton of biosolids.

Marsilea spp.—A novel source of lignocellulosic biomass: Effect of solubilized lignin on anaerobic biodegradability and cost of energy products

In this study, the phase separated effect of dispersion induced ozone pretreatment (DOP) was investigated. Solid reduction, biomass lysis and biomethane production were used as essential parameters to assess the potential of DOP over ozone pretreatment (OP). A higher suspended solid reduction of about 25.2% was achieved in DOP than OP 18%. The ozone dosage of 0.014gO3/g SS supported a maximal biomass lysis of about 32.8% when the biosolids were subjected to prior dispersion at 30s and 3000rpm. However, the same ozone dosage without phase separation achieved 9.6% biomass lysis. The second exponential model results of the biomethane assay showed that DOP enhanced the accessibility of disintegrated biosolids for methane production and induced about 1150mL/g VS of methane production. The energy analysis reveals that DOP provides significant amount of positive net energy (152.65kWh/ton) when compared to OP (-12.42kWh/ton).

Biological disintegration of microalgae for biomethane recovery-prediction of biodegradability and computation of energy balance

The present study concerns the liquefying potential of an unusual source of lignocellulosic biomass (Marsilea spp., water clover, an aquatic fern) during combinative pretreatment. The focus was on how the pretreatment affects the biodegradability, methane production, and profitability of thermochemical dispersion disintegration (TCDD) based on liquefaction and soluble lignin. The TCDD process was effective at 12,000 rpm and 11 min under the optimized thermochemical conditions (80 °C and pH 11). The results from biodegradability tests imply that 30% liquefaction was sufficient to achieve enhanced biodegradability of about 0.280 g-COD/g-COD. When biodegradability was >30% inhibition was observed (0.267 and 0.264 g-COD/g-COD at 35-40% liquefaction) due to higher soluble lignin release (4.53-4.95 g/L). Scalable studies revealed that achievement of 30% liquefaction was beneficial in terms of the energy and cost benefit ratios (0.956 and 1.02), when compared to other choices.

Food Waste Valorization by Microalgae

The present study investigates the synergistic effect of combined bacterial disintegration on mixed microalgal biomass for energy efficient biomethane generation. The rate of microalgal biomass lysis, enhanced biodegradability, and methane generation were used as indices to assess efficiency of the disintegration. A maximal dissolvable organics release and algal biomass lysis rate of about 1100, 950 and 800mg/L and 26, 23 and 18% was achieved in PA+C (protease, amylase+cellulase secreting bacteria), C (cellulase alone) and PA (protease, amylase) microalgal disintegration. During anaerobic fermentation, a greater production of volatile fatty acids (1000mg/L) was noted in PA+C bacterial disintegration of microalgal biomass. PA+C bacterial disintegration improve the amenability of microalgal biomass to biomethanation process with higher biodegradability of about 0.27gCOD/gCOD, respectively. The energy balance analysis of this combined bacterial disintegration of microalgal biomass provides surplus positive net energy (1.14GJ/d) by compensating the input energy requirements.

Recent advances on biogranules formation in dark hydrogen fermentation system: Mechanism of formation and microbial characteristics

In early twenty-first century, both developed and developing countries aim to avoid burning of fossil fuel in an effort to reduce the greenhouse gas emissions and impacts on global warming. Microalgae are potential key players for tackling greenhouse gas emissions and for providing feedstock for renewable energy production. Microalgae utilize freely available solar radiation as an energy source to extract protons and electrons from water to ultimately convert atmospheric carbon dioxide into organic carbon manifested in the growth rates and biomass concentrations. The microalgal biomass consists of biopolymers (protein and carbohydrate), lipid and pigments, which provides a platform for producing value-added products or for utilization as renewable energy resources. However, carbon and nutrient requirements for their cultivation are major bottlenecks adding to the overall production costs. Alternatively, food waste could be used for cultivation of microalgae after suitable pretreatment to solubilize organic carbon polymers. In an integrated bio-refinery approach, harvested microalgal biomass, value-added products are extracted sequentially, with the leftover components (those that do not have a significant market value) to be used in energy generation through anaerobic digestion/fermentation processes. This chapter will provide an overview on food waste valorisation by and most suitable species of microalgae, a brief discussion on adopting various pretreatment techniques for solubilization of carbon from food waste for easy valorisation by microalgae.

Sodium thiosulphate induced immobilized bacterial disintegration of sludge: an energy efficient and cost effective platform for sludge management and biomethanation

Hydrogen producing granules (HPGs) are most promising biological methods used to treat organic rich wastes and generate clean hydrogen energy. This review provides information regarding types of immobilization, supporting materials and microbiome involved on HPG formation and its performances. In this review, importance has been given to three kinds of immobilization techniques such as adsorption, encapsulation, and entrapment. The HPG, characteristics and types of organic and inorganic supporting materials followed for enhancing hydrogen yield were also discussed. This review also considers the applications of HPG for sustainable and high rate hydrogen production. A detailed discussion on insight of key mechanism for HPGs formation and its performances for stable operation of high rate hydrogen production system are also provided.

Novel insights into scalability of biosurfactant combined microwave disintegration of sludge at alkali pH for achieving profitable bioenergy recovery and net profit

The present study aimed to gain better insights into profitable biomethanation through sodium thiosulphate induced immobilized protease secreting bacterial disintegration (STS-IPBD) of sludge. STS disperse the flocs at 0.08 g/g SS of dosage and assists the subsequent bacterial disintegration. Immobilization of bacteria increases the hydrolytic activity of cells towards effective liquefaction of sludge. A higher liquefaction of 22% was accomplished for STS-IPBD when compared to immobilized protease secreting bacterial disintegration (IPBD alone). The kinetic parameters of Line Weaver Burk plot analysis revealed a maximal specific growth rate (µmax) of 0.320 h-1 for immobilized cells when compared to suspended free cells showing the benefit of immobilization. Floc dispersion and immobilization of bacteria imparts a major role in biomethanation as the methane generation (0.32 gCOD/g COD) was higher in STS-IPBD sample. The cost analysis showed that STS - IPBD was a feasible process with net profit of 2.6 USD/Ton of sludge.

Activated Sludge Process and Energy

In the present study, a novel alkali rhamnolipid combined microwave disintegration (ARMD) was employed to achieve net energy production, increased liquefaction and to increase the amenability of sludge towards biomethanation. Additionally, biosurfactant rhamnolipid under alkali conditions enhances the liquefaction at alkali pH of 10 with a maximal liquefaction of 55% with reduced energy consumption (1620 kJ/kg TS) than RMD (45.7% and 3240 kJ/kg TS specific energy) and MD (33.7% and 6480 kJ/kg TS specific energy). A higher biomethane production of 379 mL/g COD was achieved for ARMD when compared to RMD (329 mL/g COD) and MD (239 mL/g COD). The scalable studies imply that the ARMD demands input energy of -282.27 kWh. A net yield of (0.39 USD/ton) was probably achieved via novel ARMD technique indicating its suitability at large scale execution when compared to RMD (net cost -31.34 USD/ton) and MD (-84.23 net cost USD/ton), respectively.