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[Display omitted] • Calcium peroxide mediated disperser disintegration is a novel approach. • Acidic-calcium peroxide mediated disperser method solubilizes organics efficiently. • Bacillus aryabhattai amasses 85% polyhydroxybutyrate using pretreated sample. • Pretreated settled sludge yields 167 mL/g chemical oxygen demand of biogas. The proposed research envisioned to improve the accessibility of organics and hydrolysis of paper mill waste activated sludge for polyhydroxybutyrate production and anaerobic digestion. In order to fill this research gap an exploration has been made by adding lower dosage of calcium peroxide at acidic pH for the removal of exopolymeric substances thereby improving the disintegration efficacy. The results indicate that the calcium peroxide dosage of 0.06 g/g SS at pH 5 was optimum for floc fragmentation. The influence of floc fragmented sludge on disintegration by disperser shows the solubilization and solid decrement of 18.8% and 12.4% at the specific energy input of 4729.24 kJ/kg total solid. The impact of pretreated supernatant on polyhydroxybutyrate accumulation shows the maximum polyhydroxybutyrate content of 85.03 % while utilizing 60% (v/v) of pretreated sludge supernatant as a carbon source at 42 h. Subsequently, the settled sludge was directed towards an anaerobic biodegradability assay and found about 167 mL/g of chemical oxygen demand of biogas generation, which is higher than the crude sample (52 mL/g of chemical oxygen demand). The higher solubilization in pretreated sample reveals the easier accessibility of substrate by the microorganisms, thereby enhances bioenergy and valued product generation. [ABSTRACT FROM AUTHOR]

In this study, an attempt was made to disintegrate waste activated sludge (WAS) in a cost-effective way. During the first phase of this study, effective break down of extracellular polymeric substance (EPS) was performed by deflocculating WAS with 0.1 g/g SS of MgSO 4 . Deflocculation rate was 92% with discharge rate of extractable EPS at 185 mg/L. In the second phase, effective bacterial cell disintegration was obtained at 36 h post treatment. Maximum solubilization of deflocculated sludge was approximately 21%, which was higher than that of flocculated sludge (14.2%) or the control (4.5%). Biodegradability studies were assessed through kinetic analysis by non-linear regression modeling. Results revealed that the deflocculated sludge had higher methane generation (at about 235.8 mL/gVs) compared to flocculated sludge (at 146.1 mL/gVs) or the control (at 34.8 mL/gVs). Cost assessment of the present work revealed that the net yield for each ton of the deflocculated sludge was about 32.99 USD. [ABSTRACT FROM AUTHOR]

In this study, the influence of disperser induced microwave pretreatment was investigated to analyze the proficiency of floc disruption on subsequent disintegration and biodegradability process. Initially, the flocs in the sludge was disrupted through disperser at a specific energy input of 25.3 kJ/kg TS. The upshot of the microwave disintegration presents that the solids reduction and solubilization of floc disrupted (disperser induced microwave pretreated) sludge was found to be 17.33% and 22% relatively greater than that achieved in microwave pretreated (9.3% and 16%) sludge alone. The biodegradability analysis, affords an evaluation of parameter confidence and correlation determination. The eventual biodegradability of microwave pretreated, and floc disrupted sludges were computed to be 0.15 (g COD/g COD) and 0.28 (g COD/g COD), respectively. An economic assessment of this study offers a positive net profit of about 104.8 USD/ton of sludge in floc disrupted sample. [ABSTRACT FROM AUTHOR]

The solar photo-Fenton process, which is one of the advanced oxidation processes, offers a promising technology for minimization of excess sludge. This study assessed the effect of solar photo-Fenton treatment of waste activated sludge (WAS). The operating parameters, viz. pH, ferrous iron concentration and hydrogen per oxide were optimized as 3, 40 mg/L and 4 g/L. SCOD and TCOD were 380 mg/L and 1,700 mg/L at 4-h contact time. The effects of the three critical factors, viz. pH, ferrous iron concentration and hydrogen peroxide for pretreatment of WAS were simulated and evaluated using response surface methodology. This methodology has shown to be a valuable tool to model complex process such as the light-enhanced photo-Fenton reaction and to achieve optimum experimental parameters at minimal cost. Solar photo-Fenton process achieved 4.62% COD solubilization at 4-h contact time. [ABSTRACT FROM AUTHOR]

In this study, fluidized bed solar photo Fenton process was adopted for the treatment of hospital wastewater with an objective of improving the biodegradability and reducing the chemical oxygen demand (COD) of wastewater. The optimal conditions were observed at pH 3, Fe2+dosage of 5 mM, H2O2dosage of 50 mM and silica carrier amount of 40 g/L. Under such conditions, the maximum COD removal was 98% at a hydraulic retention time of 90 min. The enhancement of biodegradability, evaluated in terms of BOD5/COD ratio increased from 0.16 to 0.7. It was also observed that in fluidized bed solar photo Fenton process, the COD efficiency was 92% whereas in solar photo Fenton process the COD removal efficiency was 67% at 60 min. The effluent COD and total suspended solid concentrations were found to be 30 mg/L, which met the requirements of the discharge standard. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Potassium peroxymonosulphate effectively disrupts the sludge exopolymeric matrix. • A COD solubilization of 35.67% was achieved by phase separated pretreatment. • Phase separated pretreatment has significantly reduced the specific energy input. • Phase separated pretreatment produces higher biohydrogen of 79.76 mL/g VS. Disintegration of sludge by microwave irradiation is considered an energy-intensive pretreatment as it demands more significant energy input to achieve the desirable solubilization. Extracellular polymeric substance (EPS) present in the floc matrix of sludge limits the extent of sludge solubilization. Hence, this study attempted to disrupt the EPS with potassium peroxymonosulphate (PPMS) before microwave (MW) pretreatment to attain maximal solubilization in an energy-efficient way. A maximal EPS disruption was achieved at 0.009 g/g TS of PPMS dosage and treatment time of 36 min. The outcome of the phase-separated pretreatment shows that PPMS induced MW pretreatment (PPMS-MW) obtained a maximum chemical oxygen demand (COD) solubilization of 35.67 % at a specific energy input of 8795 kJ/kg TS. In contrast, the MW pretreatment achieved only 22.41 % at a specific energy input of 21973 kJ/kg TS. When comparing both PPMS-MW and MW pretreatments, an ample amount of energy was saved by PPMS-MW than MW. The biohydrogen production potential assay showed that PPMS-MW obtained an increased biohydrogen production of 79.76 mL/g VS compared to MW (50.10 mL/g VS). Thus, this phase-separated PPMS-MW pretreatment was considered efficient compared to MW pretreatment. [ABSTRACT FROM AUTHOR]

A fed batch membraneless microbial electrolysis cell (MEC) was investigated for treating combined leachate and dairy wastewater at an applied voltage 0.8 V and hydraulic retention time (HRT) of 48 h. The COD (chemical oxygen demand) removal and energy recovery was tested by running several cycles of MEC with increasing ratios of leachate to dairy wastewater. With an increase in percentage of simulated leachate, MEC performance in terms of current generation, COD removal efficiency and hydrogen production showed a gradual decrease. A sudden drop in reactor performance was noticed when the concentration of leachate was increased from 14 to 16% corresponding to an increase in Organic Load Rate (OLR) from 23.89gCOD/m3/d to 24gCOD/m3/d. A continued operation of MEC at an OLR of 24gCOD/m3/d for ten continuous cycles resulted in COD removal efficiency of 73% and hydrogen production of 15 mL/L/d with current density of 10 A/m2 and a power density of 80 mW/cm2. • Single chambered membraneless MEC treated leachate at low voltage 0.8 V and HRT 48 h • The MEC was operated with different organic loading rate (i.e) 18.57 to 24 gCOD/L/d. • A maximum COD removal efficiency of 73% and power density of 80 mW/cm2 was recorded. • Operation at OLR 24 gCOD/L/d for ten consecutive cycles showed improved performance. [ABSTRACT FROM AUTHOR]

Generation of bioenergy from microalgal biomass has been a focus of interest in recent years. The recalcitrant nature of microalgal biomass owing to its high cellulose content limits methane generation. Thus, the present study investigates the effect of bacterial-based biological pretreatment on liquefaction of the microalga Chlorella vulgaris prior to anaerobic biodegradation to gain insights into energy efficient biomethanation. Liquefaction of microalgae resulted in a higher biomass stress index of about 18% in the experimental (pretreated with cellulose-secreting bacteria) vs. 11.8% in the control (non-pretreated) group. Mathematical modelling of the biomethanation studies implied that bacterial pretreatment had a greater influence on sustainable methane recovery, with a methane yield of about 0.08 (g Chemical Oxygen Demand/g Chemical Oxygen Demand), than did control pretreatment, with a yield of 0.04 (g Chemical Oxygen Demand/g Chemical Oxygen Demand). Energetic analysis of the proposed method of pretreatment showed a positive energy ratio of 1.04. [ABSTRACT FROM AUTHOR]

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 141.02 kJ/kg TS and a ozone dosage of about 0.0012 mg O 3 /mg SS through this combined thermo chemo ozone (TCO 3 ) pretreatment. The methane production potential (0.32 g COD/g COD) of TCO 3 pretreatment was comparatively higher than the (0.19 g COD/g COD) 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 $/ton of biosolids. [ABSTRACT FROM AUTHOR]

• H 2 O 2 induced microwave treatment in acidic condition (AHMW) enhance disintegration. • Higher organic release was attained at 0.024 g/g TS H 2 O 2 and at pH 5. • A liquefaction of 38.5% was obtained at the specific energy of 10800 kJ/kg TS. • Biohydrogen production of 92.5 mL H 2 /g COD was achieved in AHMW pretreatment. The objective of the present study is to improve the biohydrogen production from marine macroalgae (Ulva reticulate) by acidic - hydrogen peroxide (H 2 O 2) induced microwave (AHMW) pretreatment. Higher soluble chemical oxygen demand (SCOD) release of 1450 mg/L and its liquefaction rate of 30.2% was achieved in microwave (MW) pretreatment with treatment time period of 15 mins. Varying concentration of H 2 O 2 from 0.003 to 0.03 g/g TS were used in the optimal microwave power (40%) to enhance the organic release in H 2 O 2 induced microwave pretreatment (HMW). Maximum liquefaction of 33.9% was obtained at the H 2 O 2 concentration of 0.024 g /g TS. The combined HMW pretreatment under acidic (pH 4–6.5) show synergistic effect on organic release. At optimal pH 5, AHMW pretreatment shows the SCOD release of 1850 mg/L with its liquefaction of 38.5% at time of 10 min. Therefore, AHMW pretreatment significantly reduce the treatment time and increase liquefaction when compared to MW and HMW. The maximum biohydrogen production was observed as 92.5 mL H 2 /g COD in AHMW pretreatment. [ABSTRACT FROM AUTHOR]

• Upflow MFC efficiently treats chocolaterie wastewater and enhances power production. • A higher organic removal of 70% was achieved by upflow microbial fuel cell. • At 15 h hydraulic retention time, a maximal power density of 98 mW/m2 was obtained. • At OLR of 1.6 gCOD/L d, the achieved voltage output was found to be 540 mV. The real wastewater generated from chocolateries is complex in nature and has high organic content. Microbial fuel cell (MFC) is the sustainable technology for the treatment of wastewater and simultaneous power generation. In this study an attempt has been made to utilize the chocolaterie wastewater as substrate in upflow anaerobic microbial fuel cell (UAMFC) for simultaneous waste treatment and power generation. The main aim of this study is to evaluate the effect of hydraulic retention time (HRT) and organic loading rate (OLR) on organic removal and power generation. Four bacterial species (Achromobacter insuavis strain BT1 (MF346036.1), Achromobacter insuavis strain B3 (MF346037.1), Bacillus encimensis strain B4 (MF346038.1) and Kocuria flava strain B5 (MF346039.1) were the predominant bacterial strains obtained from anode during biofilm analysis. They play a major role in substrate degradation and power generation. A maximum power density and chemical oxygen demand (COD) removal of 98 mW/m2 and 70% was obtained at a HRT of 15 h. A mathematical modelling, Monod kinetics was done to predict the substrate dependency with that of power production. The model implied that the maximal achievable power density (V max) was calculated to be 104.9 mW/m2 at higher substrate concentration of 0.8 g/L. [ABSTRACT FROM AUTHOR]

Gracilaria salicornia (macroalgae) can be used for the production of biofuels such as biomethane. Because of the complex cell wall structure in macroalgae, disintegration is crucial for anaerobic fermentation. The main goal of this study is to implement the combination of oxalic acid and ultrasonic pretreatment (SP) techniques over macroalgae Gracilaria salicornia in order to generate energy-efficient biomethane. A combination of ultrasonic pretreatment and oxalic acid (OSP) improves macromolecule availability in anaerobic fermentation, leading to enhanced biomethane production. Ultrasonic pretreatment was initially performed at 20–180 W for 5–60 min. A maximum solubilization of 9.19% was obtained, with a SCOD of 496 mg/L, at optimal conditions (140 W intensity, 30 min). Oxalic acid was added in various dosages from 0.01 to 0.1 N to optimize OSP conditions, enhance disintegration efficiency, and maximize biomethane production. With a SCOD of 914 mg/L and 16.93% SCOD solubilization, the best result was observed with 0.06 N oxalic acid dosage. A maximum biomethane production was achieved in the OSP sample (0.252 L/g COD) compared with the control (0.22 L/g COD) and SD (0.139 L/g COD) samples. As compared to SP, OSP was proved to be more energy-efficient. It was concluded that OSP was an efficient energy source for field applications. Combined OSP was a successful strategy for the production of energy-efficient biomethane. [Display omitted] • Oxalic acid coupled sonication pre-treatment of Gracilaria salicornia was studied. • Optimal conditions were shown at 140W SP with 0.06 N oxalic acid for 30 min. • 0.252 L/g COD of biomethane was obtained from the coupled pre-treatment. • COD solubilization increased by up to 17% with the combined pre-treatment. [ABSTRACT FROM AUTHOR]

• The optimized conditions were shown at 12,000 rpm with 30 min under pH 5. • The combined pretreatments yielded 60 mL/gCOD of biohydrogen. • The combined pretreatment increased COD solubilization up to 55%. • Biohydrogen production increased by about 83% at the optimized parameters. Macroalgae is becoming more popular as a viable and promising resource for the production of biofuels belonging to the third generation (i.e biofuels that are made from algae). The high ratio of carbohydrates and lipids, as well as the lack of lignin, make macroalgae a desirable feedstock for biofuel production. However, algal biomass must be pretreated before fermentation to make the carbohydrates trapped within the cell wall more accessible. An effective pretreatment method favors the hydrolysis of biomass and makes the substrates available for hydrogen production. In this study, Ulva reticulata was combinedly pretreated with a disperser and acid to effectively generate fermentative biohydrogen production. The disperser's rotational speed of about 12,000 rotation per minute and input of specific energy of about 2500 Kilojoule/Kilogram of Total Solids with the dispersion duration of thirty minutes and maintaining the biomass at pH 5 with diluted sulphuric acid were optimized as the experimental parameters for the effective solubilization of the macroalgae. The experimental results displayed that the biohydrogen production increased by about 83 % at the optimized parameters compared to the untreated algal biomass. The combined pretreatment can efficiently disrupt the macroalgal structure leading to a rise in the concentration of organic matters such as SCOD (soluble chemical oxygen demand), proteins, and carbohydrates thereby enhancing the production of biohydrogen. The combined pretreatments yielded 60 mL/g COD of biohydrogen, whereas the biomass pretreated with a disperser alone and untreated macroalgae produced only 30 mL/g COD and 5 mL/g COD of biohydrogen, respectively. Thus, it is inferred that the sample pretreated with the homogenizer (disperser) and acid produced the most biohydrogen. In general, it can be concluded that a combination of disperser along with the addition of acid could be used as an efficient method for disrupting the structure of macroalgal biomass thereby enhancing the fermentative hydrogen production. [ABSTRACT FROM AUTHOR]

In the present paper, the study focuses on the effects of sodium dodecyl sulfate (SDS) surfactant on the release of extracellular polymeric substance (EPS) followed by pretreatment with a thermophilic protease-secreting bacterial strain on WAS (waste activated sludge). This in turn enhanced the subsequent anaerobic biodegradability. The extracellular polymeric substances were released using SDS (0.03 g/g SS of dosage) to stimulate the bacterial pretreatment. The thermophilic bacterial pretreatment results indicated that deflocculated (EPS released with SDS and pretreated with bacteria) sludge showed higher Suspended Solids (SS) reduction of about 27% and Chemical Oxygen Demand (COD) solubilization of about 24%, whereas flocculated (pretreated with bacteria alone) showed SS reduction of about 18% and COD solubilization of about 16%. The biogas production potential of deflocculated, flocculated, and raw (untreated) samples was found to be 2.5211 L/(gVS), 1.7677 L/(gVS), and 0.6140 L/(gVS), respectively. As a result, the EPS release followed by disintegration of sludge by bacteria enhanced the biogas production. [ABSTRACT FROM AUTHOR]

In this study, ultrasonication was used for sludge deflocculation, followed by cell disintegration using ozone. The effect of this phase separated sono-ozone pretreatment is evaluated based on extra polymeric substances release, deoxyribonucleic acid (DNA) in the medium, solubilization of intra cellular components and suspended solids (SS) reduction. Ultrasonically induced deflocculation was optimized at an energy dosage of 76.4 (log 1.88) kJ/kg TS. During cell disintegration (ozone dosage 0.0011 mg O 3 /mg SS), chemical oxygen demand solubilization (COD) and SS reduction of sonic mediated ozone pretreated sludge were 25.4% and 17.8% comparatively higher than ozone pretreated sludge, respectively. Further, biogas production potential of control (raw), flocculated (ozone pretreated), and deflocculated (sonic mediated ozone pretreated) sludges were observed to be 0.202, 0.535 and 0.637 L/(g VS), respectively. Thus, the phase separated pretreatment at lower ultrasonic specific energy and low dose ozone proved to enhance the anaerobic biodegradability efficiently. [ABSTRACT FROM AUTHOR]

The present study investigates the impacts of phase separated disintegration through CaCl 2 (calcium chloride) mediated biosurfactant producing bacterial pretreatment. In the initial phase of the study, the flocs were disintegrated (deflocculation) with 0.06 g/g SS of CaCl 2 . In the subsequent phase, the sludge biomass was disintegrated (cell disintegration) through potent biosurfactant producing new novel bacteria, Planococcus jake 01. The pretreatment showed that suspended solids reduction and chemical oxygen demand solubilization for deflocculated – bacterially pretreated sludge was found to be 17.14% and 14.14% which were comparatively higher than flocculated sludge (treated with bacteria alone). The biogas yield potential of deflocculated – bacterially pretreated, flocculated, and control sludges were observed to be 0.322 (L/g VS), 0.225 (L/g VS) and 0.145 (L/g VS) respectively. To our knowledge, this is the first study to present the thorough knowledge of biogas production potential through a novel phase separated biosurfactant bacterial pretreatment. [ABSTRACT FROM AUTHOR]

In this investigation, an effort was made to pretreat surplus waste activated sludge (WAS) inexpensively by a novel combined process involving thermo chemical disperser pretreatment. This pretreatment was found to be efficient at a specific energy (SE) consumption of 3360.94 kJ/kg TS, with the chemical oxygen demand (COD) solubilization of 20%. This was comparatively higher than thermo chemically treated sludge where the solubilization was found to be 15.5% at a specific energy consumption of 10,330 kJ/kg TS respectively. Higher production of volatile fatty acids (VFA) (675 mg/L) in anaerobic fermentation of pretreated WAS indicates better hydrolysis performance. The biogas production potential of sludge pretreated through this combined technique was found to be 0.455 (L/g VS) and comparatively higher than thermo chemically pretreated sludge. Economic investigation provides 90% net energy savings in this combined pretreatment. Therefore, this combined process was considered to be potentially effective and economical in sludge disintegration. [ABSTRACT FROM AUTHOR]

The significance of citric acid, a cation binding agent, was investigated for the exclusion of extracellular polymeric substance (EPS) from waste activated sludge (WAS) and anaerobic biodegradability following enzymatic bacterial pretreatment. EPS was removed with 0.05 g/g SS of citric acid. The results of pretreatment found that the suspended solids reduction and chemical oxygen demand solubilisation were 21.4% and 16.2% for deflocculated-bacterially pretreated sludge, 14.28% and 10.0% for flocculated sludge (without EPS removal and bacterially pretreated) and 8.5% and 6.5% for control sludge (raw sludge), respectively. Further assessing anaerobic biodegradability, the biogas yield potential of deflocculated and bacterially pretreated, flocculated, and control sludges were found to be 0.455 L/(g VS), 0.343 L/(g VS), and 0.209 L/(g VS), respectively. Thus, phase-separated disintegration enhanced anaerobic biodegradability efficiently. [ABSTRACT FROM AUTHOR]

Highlights: [•] In this study, the optimal conditions were, SE of 4172kJ/kg TS for NaOH – pH 10. [•] COD solubilization and SS reduction was 59% and 46% higher than control. [•] 2-step disintegration process was carried out for understanding of WAS hydrolysis. [•] Pretreatment with anaerobic digestion led to 58% and 62% of SS and VS reduction. [•] Improvement of 83% in biogas production was observed. [Copyright &y& Elsevier]

[Display omitted] • Combined treatment of microwave – surfactant enhance the macroalgal solubilisation. • Maximum of 34.2 % algal biomass solubilisation achieved in SIMD. • SIMD obtained a maximum hydrogen production of 54.9 mL H 2 /g COD. • Energy ratio of 1.04 achieved at SIMD pretreatment. This research work aimed about the enhanced bio-hydrogen production from marine macro algal biomass (Ulva reticulate) through surfactant induced microwave disintegration (SIMD). Microwave disintegration (MD) was performed by varying the power from 90 to 630 W and time from 0 to 40 min. The maximum chemical oxygen demand (COD) solubilisation of 27.9% was achieved for MD at the optimal power (40%). A surfactant, ammonium dodecyl sulphate (ADS) is introduced in optimal power of MD which enhanced the solubilisation to 34.2% at 0.0035 g ADS/g TS dosage. The combined SIMD pretreatment significantly reduce the treatment time and increases the COD solubilisation when compared to MD. Maximum hydrogen yield of 54.9 mL H 2 /g COD was observed for SIMD than other samples. In energy analysis, it was identified that SIMD was energy efficient process compared to others since SIMD achieved energy ratio of 1.04 which is higher than MD (0.38). [ABSTRACT FROM AUTHOR]

An investigation into the influence of combined alkaline and disperser pretreatment on sludge disintegration was studied. The effects of four variables, alkalines (NaOH, KOH, Ca(OH) 2 ), treatment time (15–180 min), pH (8–11) and rpm (4000–24,000) were investigated. The effect of sludge pretreatment was evaluated by COD solubilization, suspended solids reduction and biogas production. The best performances, in terms of COD solubilization, SS reduction and biogas production, were the ones that occurred for specific energy input of 4544 kJ kg −1 TS for NaOH at pH10, were found to be 24%, 23.3% and 76%, higher than the control, respectively. Not only the increase in biogas production was investigated, excluding protein hydrolysis was also performed successfully by this combined pretreatment even at low specific energy input. Thus, this chemo-mechanical is an effective method for enhancement of biodegradability and it laid the basis to produce higher biogas quantities, to improve clean energy generation from WAS. [ABSTRACT FROM AUTHOR]

Abstract: An investigation into the influence of low temperature thermo-chemical pretreatment on sludge reduction in a semi-continuous anaerobic reactor was performed. Firstly, effect of sludge pretreatment was evaluated by COD solubilization, suspended solids reduction and biogas production. At optimized condition (60°C with pH 12), COD solubilization, suspended solids, reduction and biogas production was 23%, 22% and 51% higher than the control, respectively. Secondly, semi-continuous process performance was studied in a lab-scale semi-continuous anaerobic reactor (5L), with 4L working volume. With three operated SRTs, the SRT of 15days was found to be most appropriate for economic operation of the reactor. Combining pretreatment with anaerobic digestion led to 80.5%, 117% and 90.4% of TS, SS and VS reduction respectively, with an improvement of 103% in biogas production. Thus, low temperature thermo-chemical can play an important role in reducing sludge production. [Copyright &y& Elsevier]

[Display omitted] • Effect of cow dung biochar (BC) on water hyacinth anaerobic digestion was investigated. • Pretreatment caused a significant an increase in sCOD (4.91-folds) contents. • Maximum biogas yield improved by 42.5 % in 1 % BC. • Biomethane content improved by 19.8 % in 1% BC setup. The effect of dilute acid-thermal pretreatment and cattle dung biochar (BC) addition on anaerobic co-digestion (AcoD) of water hyacinth (WH) with waste activated sludge (WAS) was investigated in this study under mesophilic condition. The dilute acid-thermal pretreatment (2% H 2 SO 4 w/v followed by 121 °C, 60 min) hydrolyzed 38.1% (lignin), 56.8% (cellulose) and 86.7% (hemicellulose) of lignocellulosic fraction and increased the soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFA) concentration by 4.91-folds and 2.20-folds, respectively. The cumulative biogas production in pretreated and biochar amended digesters was 73.4–98.7% higher than the control digester. Methane content in biogas improved by 9.33 – 19.8% in BC supplemented assays over control. The highest methane yield of 235 mL and VS removal (77.4%) were observed for pretreated, and biochar (1% dose) amended digester. The morphological and structural transformations in non-pretreated and dilute acid-thermal pretreated WH biomass were studied by Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis. SEM results shows the porous and rougher structure with flake-like structures owing to harsh pre-treatment conditions. FTIR analysis revealed significant changes in polymer composition and strong lignification of WH biomass. Thus, the dilute acid-low thermal pretreatment of lignocellulosic feedstock and cattle dung biochar amendments in digester are promising methods for effective biomethanation. [ABSTRACT FROM AUTHOR]

• A maximum COD solubilisation of 34% was achieved in MHA. • MHA reduced pre-treatment energy from 32,400 to 17280 kJ/kg TS. • MHA achieved a maximum H 2 yield of 87.5 mL H 2 /g COD. • Energy ratio of 1.12 achieved at MHA pretreatment. This study aims to enhance the hydrogen (H 2) production from marine macro algae (Ulva Reticulate) by microwave combined with hydrogen peroxide (H 2 O 2) under alkaline condition. Microwave (domestic type) (M) pretreatment of algal biomass at its optimal power (40%) resulted in 27.9% COD solubilization at 15 min time interval. When this optimal microwave power was combined with H 2 O 2 (MH) an increment in COD solubilization was achieved at 24 mg H 2 O 2 /g macroalgae dosage. Under alkaline condition (pH 7–12), microwave and H 2 O 2 combination (MHA) yielded better result than MH. At optimal alkaline condition (pH 10), MHA pretreatment shows a COD solubilization of 34%. Microwave in alkaline condition induces decomposition of H 2 O 2 and more OH radical synthesis. This synergistically promotes solubilization. The MHA process considerably diminish time and specific energy required for biomass disintegration. Among the samples, highest H 2 yield of 87.5 mL H 2 /g COD was observed for MHA. [ABSTRACT FROM AUTHOR]

• Phase separated biological pretreatment is a new microalgal disintegration process. • A higher biomass solubilization of 36% was achieved in the present study. • Mechanisms involved in cell wall weakening and disintegration was clearly focused. • Richard model adequately fits the experimental methane values with R2 (0.98–0.99). • Phase separated pretreatment of microalgal biomass was a profitable process. This study involves the application of new phase separated biological pretreatment (PSBP) strategy on microalgal biomass using the nickel nanoparticle induced cellulase secreting bacterial disintegration. Particularly, interest was focussed on cell wall weakening (CWW) of microalgae biomass besides the cell disintegration (CD) and release of organics. During CWW, protein, carbohydrate, cellulose, hemicellulose and DNA were used as evaluation indexes. Similarly, during CD, soluble chemical oxygen demand was used as evaluation index to assess the disintegration effect. A higher CWW was achieved at nickel nanoparticle (Np) dosage of 0.004 g/g SS. During CD, a clear demarcation in biomass solubilisation was achieved by PSBP (36%) than the sole biological pretreatment –BP (24%). The biomethanogenesis test results showed that enhanced methane production of 411 mL/g COD was achieved by PSBP than BP. Energy analysis showed that a higher net energy production of 6.467 GJ/d was achieved by PSBP. [ABSTRACT FROM AUTHOR]