Anaerobic digestion of food waste to methane at various organic loading rates (OLRs) and hydraulic retention times (HRTs)

Gopalakrishnan Kumar,Periyasamy Sivagurunathan,Jong Hun Park,Sang Hyoun Kim 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.1

Generation of food waste is a serious issue that needs to be addressed worldwide. Developing suitable treatment methods while generating energy (methane) is a common practice for sustainable treatment of waste. In this study, methane generation by food waste was investigated in mesophilic and thermophilic regimes at various hydraulic retention times (HRTs) and organic loading rates (OLR). In temperature regimes, influent concentrations and HRTs ranged from 30 to 110 g COD/L and 18 to 30 days, respectively, which corresponding to an OLR of 1.0 to 6.1 kg COD/㎥-d. Better methane production and organic removal was observed under thermophilic conditions because of the enhanced hydrolysis of complex polymers and microbial activity at higher temperature. The peak methane productivities attained in thermophilic and mesophilic regimes were 1.30 and 0.99 ㎥/㎥-d, respectively. The maximum methane yields were achieved at 50 g COD/L and HRT of 24 d in both cases, and the values were 264 and 221 ㎥/ton COD, respectively. The results of this study will facilitate the development of sustainable methane production technologies using food waste as a feedstock.

Anaerobic Digestion of Food Waste: Meshophilic vs Thermophilic Regime

( Gopalakrishnan Kumar ),( Hyun Jun Ju ),( Sang-hyuon Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.1

Food waste generation around the globe is a serious issue that needs to be concerned. Developing suitable treatment methods along with the generation of energy (methane) is a common practice to make the world sustainable. In this study, methane generation of food waste has been reported in mesophilic and thermophilic regimes at various hydraulic retention times (HRT) and organic loading rates (OLR). Different reactor configurations were used for mesophilic and thermophilic operations. The influent concentrations were ranged from 30 to 110 g COD/L corresponding to the OLR of 1.0 to 5.5 Kg COD/m³*d, respectively. Three different HRTs evaluated were 30, 24 and 20 days in both regimes. The production performances showed that an increase in biogas and methane production while increasing the substrate concentration in both temperatures. However, better results were obtained from thermophilic temperature due to the hydrolysis of the complex polymers at higher temperatures. Peak methane productivities attained at mesophilic and thermophilic regimes were 1.30 and 0.95 m³/m³*d, respectively. However, the maximal yield achieved were at 50 g CODL and at HRT of 24 d in both the cases and the values were 264 and 221 m3/ton COD, respectively. The COD removal rate was ranged from 54-86% in case of thermophilic and 61-87% in case of mesophilic, respectively. The results of this study could aid in the development of sustainable methane production technologies using food waste as carbon source.

Cultivation of microalgal biomass using swine manure for biohydrogen production: Impact of dilution ratio and pretreatment

Kumar, Gopalakrishnan,Nguyen, Dinh Duc,Sivagurunathan, Periyasamy,Kobayashi, Takuro,Xu, Kaiqin,Chang, Soon Woong Elsevier 2018 Bioresource technology Vol.260 No.-

<P><B>Abstract</B></P> <P>This study assessed the impact of swine manure (SM) dilution ratio on the microalgal biomass cultivation and further tested for biohydrogen production efficiency from the mixed microalgal biomass. At first, various solid/liquid (S/L) ratio of the SM ranged from 2.5 to 10 g/L was prepared as a nutrient medium for the algal biomass cultivation without addition of the external nutrient sources over a period of 18 d. The peak biomass concentration of 2.57 ± 0.03 g/L was obtained under the initial S/L loading rates of 5 g/L. Further, the cultivated biomass was subjected to two-step (ultrasonication + enzymatic) pretreatment and evaluated for biohydrogen production potential. Results showed that the variable amount of hydrogen production was observed with different S/L ratio of the SM. The peak hydrogen yield of 116 ± 6 mL/g TS<SUB>added</SUB> was observed at the 5 g/L grown SM mixed algal biomass.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dilution ratio of swine manure concentration affects the microalgae growth. </LI> <LI> Peak microalgae biomass production was obtained as 2.57 g/L. </LI> <LI> Ultrasonication + enzyme pretreatment can be a viable approach for H<SUB>2</SUB> fermentation. </LI> <LI> Peak hydrogen yield of 116 mL/g microalgae biomass was achieved. </LI> </UL> </P>

Gallbladder perforation

Gopalakrishnan Gunasekaran,Debasis Naik,Ashwani Gupta,Vimal Bhandari,Manigandan Kuppusamy,Gaind Kumar,Niuto S Chishi 한국간담췌외과학회 2015 한국간담췌외과학회지 Vol.19 No.1

Backgrounds/Aims: Gallbladder perforation is a rare but potentially fatal disease. We herein present our clinical experience in diagnosis and management of 32 cases of gallbladder perforation. Methods: This retrospective study was conducted with inclusion of all cases of gallbladder perforation that presented to our hospital from January 2012 to November 2014. Cases of traumatic gallbladder perforation and patients younger than 12 years of age were excluded from this study. Results: This study included 32 patients (13 males and 19 females). The mean age of patients was 55.9 years. Gallbladder perforation was most common in the 5th and 6th decade of life. The mean age of patients with type I, II, and III gallbladder perforation was 57.0 years, 57.6 years, and 49.8 years, respectively. The most common site of perforation was the fundus, followed by the body and Hartmann’s pouch (24 : 5 : 2). Most of the type I gallbladder perforations were diagnosed intraoperatively, type II gallbladder perforations were diagnosed by enhanced abdominal computed tomography, and type III gallbladder perforations were diagnosed during laparoscopic cholecystectomy converted to open cholecystectomy for cholelithiasis. Mortality was highest in patients with type I gallbladder perforation. The mean hospital stay was 10.1 days, 6.4 days, and 9.2 days in patients with type I, II, and III gallbladder perforation, respectively. The histopathologic analysis in 28 patients who were operated on showed acute cholecystitis in 19 cases, acute-on-chronic cholecystitis in 4 cases, chronic cholecystitis in 4 cases, and mucinous adenocarcinoma of the gallbladder in a single case. Conclusions: Gallbladder perforation represents a special diagnostic and surgical challenge. Appropriate classification and management are essential.

Structural damage detection through longitudinal wave propagation using spectral finite element method

Kumar, K. Varun,Saravanan, T. Jothi,Sreekala, R.,Gopalakrishnan, N.,Mini, K.M. Techno-Press 2017 Geomechanics & engineering Vol.12 No.1

This paper investigates the damage identification of the concrete pile element through axial wave propagation technique using computational and experimental studies. Now-a-days, concrete pile foundations are often common in all engineering structures and their safety is significant for preventing the failure. Damage detection and estimation in a sub-structure is challenging as the visual picture of the sub-structure and its condition is not well known and the state of the structure or foundation can be inferred only through its static and dynamic response. The concept of wave propagation involves dynamic impedance and whenever a wave encounters a changing impedance (due to loss of stiffness), a reflecting wave is generated with the total strain energy forked as reflected as well as refracted portions. Among many frequency domain methods, the Spectral Finite Element method (SFEM) has been found suitable for analysis of wave propagation in real engineering structures as the formulation is based on dynamic equilibrium under harmonic steady state excitation. The feasibility of the axial wave propagation technique is studied through numerical simulations using Elementary rod theory and higher order Love rod theory under SFEM and ABAQUS dynamic explicit analysis with experimental validation exercise. Towards simulating the damage scenario in a pile element, dis-continuity (impedance mismatch) is induced by varying its cross-sectional area along its length. Both experimental and computational investigations are performed under pulse-echo and pitch-catch configuration methods. Analytical and experimental results are in good agreement.

Photoautotrophic cultivation of mixed microalgae consortia using various organic waste streams towards remediation and resource recovery

Huy, Menghour,Kumar, Gopalakrishnan,Kim, Hyun-Woo,Kim, Sang-Hyoun Elsevier Applied Science 2018 Bioresource technology Vol.247 No.-

<P><B>Abstract</B></P> <P>In this study, mixed microalgae consortia was cultivated using digestate (D), animal manure (AM) and textile wastewater (TW) as growth medium providing mainly N (nitrogen) and P (phosphorous) sources without any extra nutrient addition. The corresponding total nitrogen (TN) and total phosphorous (TP, PO3-P) concentrations were noted as 323 and 21 for AM, 481 and 31 for TW and 747 and 55mg/L for D, respectively. After a cultivation period of 13days, P were completely removed (100%), however, N was still remain and attained the removal rate of 70.1, 72.3 and 16.7% for TW, AM and D, respectively. The peak growth rate and biomass production of 0.419d<SUP>−1</SUP> and 0.4g/L (in terms of volatile solids, VS) was achieved using TW as growth medium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three various growth medium have been evaluated for microalgae cultivation. </LI> <LI> Textile waste water showed the best potential for enhanced microalgae growth. </LI> <LI> Peak growth rate and biomass production of 0.419d<SUP>−1</SUP> and 0.4g/L were attained. </LI> </UL> </P>

Dynamic stiffness based computation of response for framed machine foundations

Lakshmanan, N.,Gopalakrishnan, N.,Rama Rao, G.V.,Sathish kumar, K. Techno-Press 2009 Geomechanics & engineering Vol.1 No.2

The paper deals with the applications of spectral finite element method to the dynamic analysis of framed foundations supporting high speed machines. Comparative performance of approximate dynamic stiffness methods formulated using static stiffness and lumped or consistent or average mass matrices with the exact spectral finite element for a three dimensional Euler-Bernoulli beam element is presented. The convergence of response computed using mode superposition method with the appropriate dynamic stiffness method as the number of modes increase is illustrated. Frequency proportional discretisation level required for mode superposition and approximate dynamic stiffness methods is outlined. It is reiterated that the results of exact dynamic stiffness method are invariant with reference to the discretisation level. The Eigen-frequencies of the system are evaluated using William-Wittrick algorithm and Sturm number generation in the $LDL^T$ decomposition of the real part of the dynamic stiffness matrix, as they cannot be explicitly evaluated. Major's method for dynamic analysis of machine supporting structures is modified and the plane frames are replaced with springs of exact dynamic stiffness and dynamically flexible longitudinal frames. Results of the analysis are compared with exact values. The possible simplifications that could be introduced for a typical machine induced excitation on a framed structure are illustrated and the developed program is modified to account for dynamic constraint equations with a master slave degree of freedom (DOF) option.

Feasibility of enriched mixed cultures obtained by repeated batch transfer in continuous hydrogen fermentation

Sivagurunathan, Periyasamy,Kumar, Gopalakrishnan,Park, Jeong-Hoon,Park, Jong-Hun,Park, Hee-Deung,Yoon, Jeong-Jun,Kim, Sang-Hyoun Pergamon Press 2016 International journal of hydrogen energy Vol.41 No.7

<P><B>Abstract</B></P> <P>This research investigated the suitability of enriched mixed cultures (EMC) for anaerobic hydrogen fermentation in continuous operation. EMC was prepared after four successive transfers in PYG (peptone, yeast extract and galactose) medium in batch cultivation. The peak hydrogen production rate (HPR) and hydrogen yield (HY) of 770 ± 10 mL H<SUB>2</SUB>/L-d and 1.05 ± 0.06 mol H<SUB>2</SUB>/mol galactose<SUB>added</SUB>, were attained respectively. There forward a continuously stirred tank reactor (CSTR) has been operated with the substrate concentration of 15 g/L at a hydraulic retention time (HRT) of 12 h for more than 15 days by using EMC. The performance showed that HPR and HY were fluctuated significantly during the operation and the average values were 1710 ± 250 mL H<SUB>2</SUB>/L-d and 0.82 ± 0.12 mol H<SUB>2</SUB>/mol galactose<SUB>added</SUB>, respectively. The soluble metabolic products analysis revealed that butyrate, lactate and acetate were the dominant metabolic products with less quantity of propionic and formic acids. The microbial community structure has been determined by next generation DNA sequencing technique and revealed <I>Clostridium</I> sp. was the dominant microbial consortium during repeated batch transfer, whereas <I>Sporolactobacillus</I> sp. was the major population in continuous operation. This study demonstrates that operational mode (batch and continuous) significantly influence the microbial diversity and hydrogen production, and EMC obtained by repeated process may not be suitable for continuous hydrogen fermentation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Repeated batch transfer provided H<SUB>2</SUB> producing enriched mixed cultures (EMC). </LI> <LI> <I>Clostridium</I> sp. was the dominant microbial population in EMC. </LI> <LI> <I>Sporolactobacillus</I> sp. was the major population during continuous H<SUB>2</SUB> production. </LI> </UL> </P>

Co-digestion of untreated macro and microalgal biomass for biohydrogen production: Impact of inoculum augmentation and microbial insights

Sivagurunathan, Periyasamy,Kumar, Gopalakrishnan,Kobayashi, Takuro,Xu, Kaiqin,Kim, Sang-Hyoun,Nguyen, Dinh Duc,Chang, Soon Woong Elsevier 2018 International journal of hydrogen energy Vol.43 No.25

<P><B>Abstract</B></P> <P>This study assessed the co-digestion of macro and microalgal biomass towards the improvement of hydrogen production. The red macroalgal biomass (<I>Gelidium amansii</I>) and green mixed microalgal biomass was mixed in a ratio of 8:2, with an initial substrate concentration of 10 g/L, and various amount of inoculum addition range from 3 to 15% (v/v) was evaluated to assess the feasible substrate to inoculum ratio for the effective co-digestion of the algal biomass. The results showed that the co-digestion with 6% inoculum addition provided the peak hydrogen yield of 45 mL/g dry biomass added with a high hydrogen content of 24% in the gas phase. The other tested conditions showed moderate hydrogen content in the range of 17–22%, respectively. These results suggest that anaerobic co-digestion of macro and microalgal biomass, with appropriate initial biomass loading (6%) is essential for enhanced hydrogen production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Inoculum augmentation improves the co-digestion performances. </LI> <LI> Maximum hydrogen yield of 45 mL H<SUB>2</SUB>/g TS was achieved. </LI> <LI> Peak COD removal efficiency of 28.5% achieved at 6% inoculum loading rate. </LI> <LI> <I>Eubacteria</I> and <I>Clostridium</I> were the dominant microflora. </LI> </UL> </P>

A review of the innovative gas separation membrane bioreactor with mechanisms for integrated production and purification of biohydrogen

Bakonyi, Pé,ter,Kumar, Gopalakrishnan,Bé,lafi-Bakó,, Katalin,Kim, Sang-Hyoun,Koter, Stanislaw,Kujawski, Wojciech,Nemestó,thy, Ná,ndor,Peter, Jakub,Pientka, Zbynek Elsevier 2018 Bioresource technology Vol.270 No.-

<P><B>Abstract</B></P> <P>This review article focuses on an assessment of the innovative Gas Separation Membrane Bioreactor (GS-MBR), which is an emerging technology because of its potential for in-situ biohydrogen production and separation. The GS-MBR, as a special membrane bioreactor, enriches CO<SUB>2</SUB> directly from the headspace of the anaerobic H<SUB>2</SUB> fermentation process. CO<SUB>2</SUB> can be fed as a substrate to auxiliary photo-bioreactors to grow microalgae as a promising raw material for biocatalyzed, dark fermentative H<SUB>2</SUB>-evolution. Overall, these features make the GS-MBR worthy of study. To the best of the authors’ knowledge, the GS-MBR has not been studied in detail to date; hence, a comprehensive review of this topic will be useful to the scientific community.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel integrative system has been proposed for biohydrogen technology. </LI> <LI> Innovative Gas Separation Membrane Bioreactors are evaluated. </LI> <LI> Simultaneous biohydrogen production and separation is outlined. </LI> <LI> Gas separation membrane technology for CO<SUB>2</SUB> removal is suggested. </LI> <LI> Algae cultivation using the CO<SUB>2</SUB> removed and biohydrogen effluent is assessed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>