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化工专题（ScienceDirect数据库） 第6期 （总15期） 2017年10月15日

《Bioresource Technology》 Volumes 247

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Effect of agitation time on nutrient distribution in full-scale CSTR biogas digesters

o Pages 1-6

o Philipp Kress, Hans-Joachim Nägele, Hans Oechsner, Stephan Ruile

Abstract

The aim of this work was to study the impact of reduced mixing time in a full-scale CSTR biogas reactor from 10 to 5 and to 2 min in half an hour on the distribution of DM, acetic acid and FOS/TAC as a measure to cut electricity consumption. The parameters in the digestate were unevenly distributed with the highest concentration measured at the point of feeding. By reducing mixing time, the FOS/TAC value increases by 16.6%. A reduced mixing time of 2 min lead to an accumulation of 15% biogas in the digestate.

Influence of operating pressure on the biological hydrogen methanation in trickle-bed reactors

o Pages 7-13

o Timo Ullrich, Jonas Lindner, Katharina Bär, Friedemann Mörs, Frank Graf, Andreas Lemmer

Abstract

In order to investigate the influence of pressures up to 9 bar absolute on the productivity of trickle-bed reactors for biological methanation of hydrogen and carbon dioxide, experiments were carried out in a continuously operated experimental plant with three identical reactors. The pressure increase promises a longer residence time and improved mass transfer of H2 due to higher gas partial pressures. The study covers effects of different pressures on important parameters like gas hourly space velocity, methane formation rate, conversion rates and product gas quality. The methane content of 64.13 ± 3.81 vol-% at 1.5 bar could be increased up to 86.51 ± 0.49 vol-% by raising the pressure to 9 bar. Methane formation rates of up to 4.28 ± 0.26 m3 m−3 d−1 were achieved. Thus, pressure increase could significantly improve reactor performance.

Prediction model of biocrude yield and nitrogen heterocyclic compounds analysis by hydrothermal liquefaction of microalgae with model compounds

o Pages 14-20

o Lili Sheng, Xin Wang, Xiaoyi Yang

Abstract

The model of biocrude yield and the nitrogen heterocyclic compounds in biocrude of microalgae hydrothermal liquefaction are two of the most concerned issues in this field at present. This study explored a hydrothermal liquefaction biocrude yield model involved in the interaction among biochemical compounds in microalgae and analysed nitrogen heterocyclic compounds in biocrude. The model compound (castor oil, soya protein and glucose) and Nanochloropsis were liquefied at 280 °C for 1 h. The products were analyzed by GC–MS, element analysis and FTIR. The results suggested that interactions among different components in microalgae enhanced biocrude yield. The biocrude yield prediction model involved cross-interactions performed more accurate than previous models.When the ratio of protein and carbohydrate around 3, the cross-interaction and nitrogen heterocyclic compounds in biocrude would both reach the highest extent.

Kinetics evaluation and thermal decomposition characteristics of co-pyrolysis of municipal sewage sludge and hazelnut shell

o Pages 21-29

o Bing Zhao, Xinyang Xu, Haibo Li, Xi Chen, Fanqiang Zeng

Abstract

Hazelnut shell, as novel biomass, has lower ash content and abundant hydrocarbon, which can be utilized resourcefully with municipal sewage sludge (MSS) by co-pyrolyisis to decrease total content of pollution. The co-pyrolysis of MSS and hazelnut shell blend was analyzed by a method of multi-heating rates and different blend ratios with TG-DTG-MS under N2 atmosphere. The apparent activation energy of co-pyrolysis was calculated by three iso-conversional methods. Satava–Sestak method was used to determine mechanism function G(α) of co-pyrolysis, and Lorentzian function was used to simulate multi-peaks curves. The results showed there were four thermal decomposition stages, and the biomass were cracked and evolved at different temperature ranges. The apparent activation energy increased from 123.99 to 608.15 kJ/mol. The reaction mechanism of co-pyrolysis is random nucleation and nuclei growth. The apparent activation energy and mechanism function afford a theoretical groundwork for co-pyrolysis technology.

Dipotassium phosphate improves the molecular weight stability of polysialic acid in Escherichia coli K235 culture broth

o Pages 30-35

o Jianrong Wu, Xudong Fu, Yun Jiang, Xu Ma, Hongtao Zhang, Xiaobei Zhan

Abstract

This work elucidated the intrinsic mechanism underlying the influence of K2HPO4 on PSA production and molecular weight (MW) stability. Among the different potassium salts mixed with K2HPO4 in the initial medium, those with buffering capacity were favorable for PSA production. In the bioreactor culture with pH control, adding an appropriate concentration of K2HPO4 could enhance PSA production. A dual-phase pH control strategy with ammonia water and KOH could also increase the yield and maintain the MW stability of PSA. Zeta potential test, UV/circular dichroism spectra, and transmission electric microscopy were utilized to explore the configuration of K2HPO4–PSA complex. The results from this study can serve a good basis for the industrial-scale production of PSA with stable MW.

Role of granular activated carbon in the microalgal cultivation from bacteria contamination

o Pages 36-43

o Zhi-Yi Ni, Jing-Ya Li, Zhao-Zhao Xiong, Li-Hua Cheng, Xin-Hua Xu

Abstract

Microalgal wastewater treatment has been considered as one of the most promising measures to treat nitrogen and phosphorus in the municipal wastewater. While the municipal wastewater provides sufficient nitrogen and phosphorus for microalgal growth, the microalgae still faces serious biological contamination caused by bacteria in wastewater. In this study, the commercial granular activated carbon (GAC) was added into the simulated municipal wastewater to avoid the influence of bacteria on the growth of microalgae. The extracellular organic matter (EOM) in microalgal broth was then characterized to enlighten the role of GAC in reducing the bioavailability of EOM. The results showed that the GAC addition could increase the dry weight of microalgae from 0.06 mg L−1 to 0.46 mg L−1 under the condition of bacterial inoculation. The GAC could mitigate bacterial contamination mainly due to its adsorption of both bacteria and EOM that might contain algicidal extracellular substances. Moreover, compared to the control group, the GAC addition could mitigate the microalgal lysis caused by bacteria and thus greatly reduce the bioavailability of EOM from 2.80 mg L−1 to 0.61 mg L−1, which was beneficial for the improvement of biostability and reuse of effluent after the microalgal harvesting.

The interactions of algae-bacteria symbiotic system and its effects on nutrients removal from synthetic wastewater

o Pages 44-50

o Xiyan Ji, Mengqi Jiang, Jibiao Zhang, Xuyao Jiang, Zheng Zheng

Abstract

The ability of Chlorella vulgaris-Bacillus licheniformis and Microcystis aeruginosa-Bacillus licheniformis consortiums to eliminate total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and soluble chemical oxygen demand (sCOD) from synthetic wastewater was studied. The highest values of dry cell weight, chlorophyll-a, and chlorophyll metabolism related genes/bacterial rRNA gene copies were obtained in the Chlorella vulgaris-Bacillus licheniformis system at Chlorella vulgaris and Bacillus licheniformis ratio of 1:3. On the 10th day, the Chlorella vulgaris-Bacillus licheniformis system at this ratio removed 86.55%, 80.28% and 88.95% of sCOD, TDP and TDN, respectively. But, the Microcystis aeruginosa-Bacillus licheniformis system at this ratio only removed 65.62%, 70.82%, and 21.56% of sCOD, TDP and TDN, respectively. Chlorella vulgaris and Bacillus licheniformis could coexist as an algae-bacteria consortia and quorum sensing substances (autoinducing peptides and bis (3′-5′) diguanylic acid) concentrations were measured. Finally, the interactions and communication patterns between Chlorella vulgaris and Bacillus licheniformis were depicted.

Optimization and kinetic study of ultrasonic assisted esterification process from rubber seed oil

o Pages 51-57

o Huong Trinh, Suzana Yusup, Yoshimitsu Uemura

Abstract

Recently, rubber seed oil (RSO) has been considered as a promising potential oil source for biodiesel production. However, RSO is a non-edible feedstock with a significant high free fatty acid (FFA) content which has an adverse impact on the process of biodiesel production. In this study, ultrasonic-assisted esterification process was conducted as a pre-treatment step to reduce the high FFA content of RSO from 40.14% to 0.75%. Response surface methodology (RSM) using central composite design (CCD) was applied to the design of experiments (DOE) and the optimization of esterification process. The result showed that methanol to oil molar ratio was the most influential factor for FFA reduction whereas the effect of amount of catalyst and the reaction were both insignificant. The kinetic study revealed that the activation energy and the frequency factor of the process are 52.577 kJ/mol and 3.53 × 108 min−1, respectively.

The roles of starch and lipid in Chlorella sp. during cell recovery from nitrogen starvation

o Pages 58-65

o Shunni Zhu, Pingzhong Feng, Jia Feng, Jin Xu, Zhongming Wang, Jingliang Xu, Zhenhong Yuan

Abstract

The influence of N-replenishment on cell growth, chlorophyll content, nitrogen uptake, and accumulation of starch and lipid was studied in Chlorella sp. N-starved algal cells were fully recovered within 2 days after N-replenishment. Stored starch in N-deficient culture was degraded immediately during recovery process. However, lipid response had a period of delay when suffered from long starvation. During the recovery process, neutral lipid was reduced accompanied by an increase in membrane lipid. It was speculated that starch served as a source of carbon and energy catabolized to support quick recovery of the culture, while lipid preferred to play a structural role that specific fatty acid species were released from storage lipid and as building blocks for quick synthesis of membrane lipid. In light of rapid growth recovery and no net degradation in total fatty acids, a semi-continuous cultivation process might be a potential way to enhance lipid productivity.

Simultaneous pyrolysis of microalgae C. vulgaris, wood and polymer: The effect of third component addition

o Pages 66-72

o Kolsoom Azizi, Mostafa Keshavarz Moraveji, Hamed Abedini Najafabadi

Abstract

Due to the depletion of fossil fuels and their environmental issues, it is necessary to find energy resources which are renewable. Biomass becomes promising feedstock for bio-fuel production. The aim of this study is to investigate thermal decomposition behavior and the effect of third component on the binary mixture pyrolysis using thermogravimetric analysis (TGA). Experiments were carried out at heating rates of 10, 20 and 40 °C/min from ambient temperature to 600 °C. Two divided groups of peaks were observed in DTG curve of tertiary mixture which the first one was corresponded to microalgae and wood and the second one was belonged to polymer. It is stated that microalgae and wood can improve the degradation process while polymer can delay the decomposition process of mixture. Mentioned positive effect of microalgae and wood could be related to main decomposition temperature and component of microalgae and wood. On the other hand, polymer reduces weight loss of binary mixture and has negative effect of it. The kinetics analysis showed that activation energy (E) and pre-exponential factor (A) of tertiary mixture was slightly lower than that of microalgae-polymer mixture which had the lowest E and A.

Biotransformation of sweet lime pulp waste into high-quality nanocellulose with an excellent productivity using Komagataeibacter europaeus SGP37 under static intermittent fed-batch cultivation

o Pages 73-80

o Swati Dubey, Jyoti Singh, R.P. Singh

Abstract

Herein, sweet lime pulp waste (SLPW) was utilized as a low- or no-cost feedstock for the production of bacterial nanocellulose (BNC) alone and in amalgamation with other nutritional supplements by the isolate K. europaeus SGP37 under static batch and static intermittent fed-batch cultivation. The highest yield (26.2 ± 1.50 g L−1) was obtained in the hot water extract of SLPW supplemented with the components of HS medium, which got further boosted to 38 ± 0.85 g L−1 as the cultivation strategy was shifted from static batch to static intermittent fed-batch. BNC obtained from various SLPW medium was similar or even superior to that obtained with standard HS medium in terms of its physicochemical properties. The production yields of BNC thus obtained are significantly higher and fit well in terms of industrial scale production.

High-yield secretory production of stable, active trypsin through engineering of the N-terminal peptide and self-degradation sites inPichia pastoris

o Pages 81-87

o Yunfeng Zhang, Hao Huang, Xinhui Yao, Guocheng Du, Jian Chen, Zhen Kang

Abstract

Streptomyces griseus trypsin (SGT) possesses enzymatic properties similar to mammalian trypsins and has great potential applications in the leather processing, bioethanol, detergent and pharmaceutical industry. Here, a new strategy was reported for improving its stable, active secretory production through engineering of its propeptide and self-degradation sites. By rationally introducing hydrophobic mutations into the N-terminus of SGT Exmt (R145I), replacing the propeptide with FPVDDDDK and engineering the α-factor signal peptide, trypsin production (amidase activity) was improved to 177.85 ± 2.83 U·mL−1 in a 3-L fermenter (a 3.75-fold increase). Subsequently, all of the residues involved in autolysis that were identified by mass spectrometry were mutated and the resulting proteins were evaluated. In particular, the variant tbcf (K101A) demonstrated high stability and production (227.65 ± 6.51 U·mL−1 and 185.71 ± 5.68 mg·L−1, respectively). The recombinant strain constructed here has great potential for large-scale production of active trypsin.

Solid state bioconversion of lignocellulosic residues by Inonotus obliquus for production of cellulolytic enzymes and saccharification

o Pages 88-95

o Xiangqun Xu, Mengmeng Lin, Qiang Zang, Song Shi

Abstract

White rot fungi have been usually considered for lignin degradation and ligninolytic enzyme production. To understand whether the white rot fungus Inonotus obliquus was able to produce highly efficient cellulase system, the production of cellulolytic enzyme cocktails was optimized under solid state fermentation. The activities of CMCase, FPase, and β-glucosidase reached their maximum of 27.15 IU/g, 3.16 IU/g and 2.53 IU/g using wheat bran at 40% (v/w) inoculum level, initial pH of 6.0 and substrate-moisture ratio of 1:2.5, respectively. The enzyme cocktail exhibited promising properties in terms of high catalytic activity at 40–60 °C and at pH 3.0–4.5, indicating that the cellulolytic enzymes represent thermophilic and acidophilic characteristics. Saccharification of raw wheat straw and rice straw by the cellulolytic enzyme cocktail sampled on Day 12 resulted in the release of reducing sugar of 130.24 mg/g and 125.36 mg/g of substrate after 48 h of hydrolysis, respectively.

Effects of target pH-value on organic acids and methane production in two-stage anaerobic digestion of vegetable waste

o Pages 96-102

o Padma Priya Ravi, Jonas Lindner, Hans Oechsner, Andreas Lemmer

Abstract

Vegetable waste is one of the major organic residues available for sustainable bioenergy production. The aim of this work is to study the influence of pH-value on process stability, hydrolysis, degradation degree and methane production in two-stage anaerobic system. A mixture of vegetable wastes with carrot mousse, carrots, celery, cabbage and potatoes was treated in two-stage system at target pH-values 5.5 and 6 in acidification reactor (AR). At pH 6, high concentrations of organic acids were recorded whereas high amount of hydrolysate was produced at pH 5.5. The chemical oxygen demand (COD) concentration in the hydrolysate produced in AR was 21.85% higher at pH 6 compared to pH 5.5, whereas the overall specific methane yield was slightly higher at pH 5.5 (354.35 ± 31.95 and 326.79 ± 41.42 L kg−1 oDMadded, respectively). It could be shown, that the described two-stage system is well suited for manure-free digestion of vegetable waste.

Semi-continuous anaerobic digestion of extruded OFMSW: Process performance and energetics evaluation

o Pages 103-115

o Lan Mu, Lei Zhang, Kongyun Zhu, Jiao Ma, Aimin Li

Abstract

Recently, extrusion press treatment shows some promising advantages for effectively separating of organic fraction of municipal solid waste (OFMSW) from the mixed MSW, which is critical for their following high-efficiency treatment. In this study, an extruded OFMSW obtained from a demonstrated MSW treatment plant was characterized, and submitted to a series of semi-continuous anaerobic experiments to examine its biodegradability and process stability. The results indicated that the extruded OFMSW was a desirable substrate with a high biochemical methane potential (BMP), balanced nutrients and reliable stability. For increasing organic loading rates (OLRs), feeding higher volatile solid (VS) contents in feedstock was much better than shortening the hydraulic retention times (HRTs), while excessively high contents caused a low biodegradability due to the mass transfer limitation. For energetics evaluation, a high electricity output of 129.19–156.37 kWh/ton raw MSW was obtained, which was further improved by co-digestion with food waste.

Impact and significance of alkaline-oxidant pretreatment on the enzymatic digestibility of Sphenoclea zeylanica for bioethanol production

o Pages 125-130

o Phuong Thi Vu, Yuwalee Unpaprom, Rameshprabu Ramaraj

Abstract

Gooseweed (Sphenoclea zeylanica Gaertn.) is a pest on the rice field that has a potential to be a promising substrate for bioethanol production. Dry powdered gooseweed was firstly pretreated with 1% NaOH, following 1% H2O2 at variety conditions. The hydrolysis process was set at 50 °C for 24–72 h with enzyme cellulase (β-glucosidase) while the fermentation process was carried using Saccharomyces cerevisiae TISTR 5020 at 33 °C for nine days. The ethanol concentration was recorded for three, five, seven, and nine days using an ebulliometer. The results showed that the treatment with only 1% NaOH for 24 h has the highest sugar performance. In regard with hydrolysis, the optimum retention time was at 24 h. Lastly, the highest ethanol concentration was achieved at 11.84 g/L after five days and a rapid decreasing after seven to nine days was also observed.

Red mud enhances methanogenesis with the simultaneous improvement of hydrolysis-acidification and electrical conductivity

o Pages 131-137

o Jie Ye, Andong Hu, Guoping Ren, Ting Zhou, Guangming Zhang, Shungui Zhou

Abstract

The role of red mud in the improvement of methanogenesis during sludge anaerobic digestion was innovatively investigated in this study. The results demonstrated that the addition of 20 g/L red mud resulted in a 35.5% increase in methane accumulation. Red mud effectively promoted the hydrolysis-acidification of organic compounds in the sludge, which resulted in the increase of protein, polysaccharide, and VFAs by 5.1–94.5%. The activities of key enzymes were improved by 41.4–257.3%. Electrochemical measurements presented direct evidence that the electrical conductivity was significantly improved with red mud. More conductive magnetite was formed during the secondary mineralization after Fe(III) reduction by Fe (III)-reducing genes such as Clostridiaceae and Ruminococcaceae. The higher conductivity enhanced the electron transfer between the syntrophic bacteria (Geobacteraceae) and methanogens (Methanosaeta and Methanosarcina), and then improved the methanogenesis. This research provides a novel perspective on the synergism between sludge and red mud for methane production.

Beneficial effect of mixture of additives amendment on enzymatic activities, organic matter degradation and humification during biosolids co-composting

o Pages 138-146

o Mukesh Kumar Awasthi, Quan Wang, Hongyu Chen, Sanjeev Kumar Awasthi, Meijing Wang, Xiuna Ren, Junchao Zhao, Zengqiang Zhang

Abstract

The objective of this study was to identify the effect of mixture of additives to improve the enzymatic activities, organic matter humification and diminished the bioavailability of heavy metals (HMs) during biosolids co-composting. In this study, zeolite (Z) (10%, 15% and 30%) with 1%lime (L) (dry weight basis of biosolids) was blended into the mixture of biosolids and wheat straw, respectively. The without any amendment and 1%lime applied treatments were run for comparison (Control). The Z + L addition resulted rapid organic matter degradation and humification with maximum enzymatic activities. In addition, higher dosage of Z + 1%L amendment reduced the bioavailability of HMs (Cu and Zn) and improved the end product quality as compared to control and 1%L applied treatments. However, the 30%Z + 1%L applied treatment showed maximum humification and low bioavailability of HMs but considering the economic feasibility and compost quality results, the treatment with 10%Z + 1%L is recommended for biosolids co-composting.

Comparison of various pretreatments for ethanol production enhancement from solid residue after rumen fluid digestion of rice straw

o Pages 147-156

o Haibo Zhang, Panyue Zhang, Jie Ye, Yan Wu, Jianbo Liu, Wei Fang, Dong Xu, Bei Wang, Li Yan, Guangming Zeng

Abstract

The rumen digested residue of rice straw contains high residual carbohydrates, which makes it a potential cellulosic ethanol feedstock. This study evaluated the feasibility and effectiveness of applying microwave assisted alkali (MAP), ultrasound assisted alkali (UAP), and ball milling pretreatment (BMP) to enhance ethanol production from two digested residues (2.5%-DR and 10%-DR) after rumen fluid digestion of rice straw at 2.5% and 10.0% solid content. Results revealed that 2.5%-DR and 10%-DR had a cellulose content of 36.4% and 41.7%, respectively. MAP and UAP improved enzymatic hydrolysis of digested residue by removing the lignin and hemicellulose, while BMP by decreasing the particle size and crystallinity. BMP was concluded as the suitable pretreatment, resulting in an ethanol yield of 116.65 and 147.42 mg g−1 for 2.5%-DR and 10%-DR, respectively. The integrated system including BMP for digested residue at 2.5% solid content achieved a maximum energy output of 7010 kJ kg−1.

Enhanced nitrogen removal from electroplating tail wastewater through two-staged anoxic-oxic (A/O) process

o Pages 157-164

o Xinmei Yan, Chunyan Zhu, Bin Huang, Qun Yan, Guangsheng Zhang

Abstract

Consisted of anaerobic (ANA), anoxic-1 (AN1), aerobic-1 (AE1), anoxic-2 (AN2), aerobic-2 (AE2) reactors and sediment tank, the two-staged A/O process was applied for depth treatment of electroplating tail wastewater with high electrical conductivity and large amounts of ammonia nitrogen. It was found that the NH4+-N and COD removal efficiencies reached 97.11% and 83.00%, respectively. Besides, the short-term salinity shock of the control, AE1 and AE2 indicated that AE1 and AE2 have better resistance to high salinity when the concentration of NaCl ranged from 1 to 10 g/L. Meanwhile, it was found through high-throughput sequencing that bacteria genus Nitrosomonas, Nitrospira and Thauera, which are capable of nitrogen removal, were enriched in the two-staged A/O process. Moreover, both salt-tolerant bacteria and halophili bacteria were also found in the combined process. Therefore, microbial community within the two-staged A/O process could be acclimated to high electrical conductivity, and adapted for electroplating tail wastewater treatment.

A novel method for bioethanol production using immobilized yeast cells in calcium-alginate films and hybrid composite pervaporation membrane

o Pages 165-173

o Eduardo Leal Isla Santos, Magdalena Rostro-Alanís, Roberto Parra-Saldívar, Alejandro J. Alvarez

Abstract

Fermentation of sugar for production of ethanol was carried out using Saccharomyces cerevisiae cells immobilized in calcium alginate films. Thin films of calcium alginate casted on a microchannel surface were used instead of the typical spherical bead configuration. Yeast immobilized on alginate films produced a higher ethanol yield than free yeast cells under the same fermentation conditions. Also, a silicalite-1/poly dimethyl siloxane composite pervaporation membrane was synthesized for ethanol separation, and characterized with flux and separation factor. The composite membrane synthesized with a 3–1 ratio of silicalite-1 to poly dimethyl siloxane showed promising results, with a flux of 140.6 g/m2 h ± 19.3 and a separation factor of 37.52 ± 3.55. Thus, the performance of both the alginate film with immobilized cells and the customized hybrid membrane suggests they could have an interesting potential application in an integrated reaction-separation device for the production and purification of bioethanol.

Potassium ferrate addition as an alternative pre-treatment to enhance short-chain fatty acids production from waste activated sludge

o Pages 174-181

o Zhang-Wei He, Wen-Zong Liu, Qin Gao, Cong-Cong Tang, Ling Wang, Ze-Chong Guo, Ai-Juan Zhou, Ai-Jie Wang

Abstract

A potentially practical technology based on ferrate (VI), i.e. potassium ferrate (PF), pretreatment integrated into waste activated sludge (WAS) anaerobic fermentation has been presented to greatly enhance short-chain fatty acids (SCFAs) production with a shortened fermentation time. The maximum production of SCFAs, 343 mg chemical oxygen demand/g volatile suspended solid with acetic acid proportion of 48.2%, was obtained with PF dosage of 56 mg Fe(VI)/g total suspended solid within 5 days, which was increased to 5.72 times compared to that of control. The mechanism study showed that PF accelerated the release rate of both intracellular and extracellular constituents. And the activities of key hydrolytic enzymes were much improved with PF addition. Moreover, PF positively enriched the abundance of microorganisms responsible for WAS hydrolysis and SCFAs production, especially acetic acid-forming characteristic genera such as Petrimonas, Fusibacter and Acetoanaerobium. Besides, the incubation time of acidogenesis and methanogenesis were separated by PF.

Influence of temperature on nitrogen fate during hydrothermal carbonization of food waste

o Pages 182-189

o Tengfei Wang, Yunbo Zhai, Yun Zhu, Chuan Peng, Bibo Xu, Tao Wang, Caiting Li, Guangming Zeng

Abstract

The influence of temperature (180–260 °C) on the fate of nitrogen during hydrothermal carbonization (HTC) of food waste (FW) was assessed. The distribution and evolution of nitrogen in aqueous products and bio-oil, as well as hydrochar, were conducted. Results suggested that elevated temperature enhanced the deamination and the highest ammonium concentration (929.75 mg/L) was acquired at 260 °C. At temperatures above 220 °C, the total N in the hydrochar became stable, whereas the mass percentage of N increased. Amines and heterocyclic-N compounds from protein cracking and Maillard reactions were identified as the main nitrogen-containing compounds in the bio-oil. As to the hydrochar, increasing temperature resulted in condensed nitrogen-containing aromatic heterocycles (e.g. pyridine-N and quaternary-N). In particular, remarkable Maillard reactions at 180 °C and the highest temperature at 260 °C enhanced nitrogen incorporation (i.e. quaternary-N) into hydrochar.

Effect of organic acids production and bacterial community on the possible mechanism of phosphorus solubilization during composting with enriched phosphate-solubilizing bacteria inoculation

o Pages 190-199

o Yuquan Wei, Yue Zhao, Mingzi Shi, Zhenyu Cao, Qian Lu, Tianxue Yang, Yuying Fan, Zimin Wei

Abstract

Enriched phosphate-solubilizing bacteria (PSB) agent were acquired by domesticated cultivation, and inoculated into kitchen waste composting in different stages. The effect of different treatments on organic acids production, tricalcium phosphate (TCP) solubilization and their relationship with bacterial community were investigated during composting. Our results pointed out that inoculation affected pH, total acidity and the production of oxalic, lactic, citric, succinic, acetic and formic acids. We also found a strong advantage in the solubilization of TCP and phosphorus (P) availability for PSB inoculation especially in the cooling stage. Redundancy analysis and structural equation models demonstrated inoculation by different methods changed the correlation of the bacterial community composition with P fractions as well as organic acids, and strengthened the cooperative function related to P transformation among species during composting. Finally, we proposed a possible mechanism of P solubilization with enriched PSB inoculation, which was induced by bacterial community and organic acids production.

Effects of impregnation of softwood with sulfuric acid and sulfur dioxide on chemical and physical characteristics, enzymatic digestibility, and fermentability

o Pages 200-208

o Zhao Wang, Guochao Wu, Leif J. Jönsson

Abstract

Hydrothermal pretreatment improves bioconversion of lignocellulose, but the effects of different acid catalysts are poorly understood. The effects of sulfuric acid (SA) and sulfur dioxide (SD) in continuous steam pretreatment of wood of Norway spruce were compared in the temperature range 195 °C–215 °C. The inhibitory effects of the pretreatment liquid on cellulolytic enzymes and Saccharomyces cerevisiae yeast were higher for SD- than for SA-pretreated material, and the inhibitory effects increased with increasing pretreatment temperature. However, the susceptibility to cellulolytic enzymes of wood pretreated with SD was 2.0–2.9 times higher than that of wood pretreated with SA at the same temperature. Data conclusively show that the superior convertibility of SD-pretreated material was not due to inhibition phenomena but rather to the greater capability of the SD pretreatment to reduce the particle size through partial delignification and cellulose degradation. Particle size was shown to be correlated with enzymatic digestibility (R2 0.97–0.98).

Effect of sludge features and extraction-esterification technology on the synthesis of biodiesel from secondary wastewater treatment sludges

o Pages 209-216

o Yolanda Patiño, Laura G. Mantecón, Sara Polo, Laura Faba, Eva Díaz, Salvador Ordóñez

Abstract

Secondary sludge from municipal wastewater treatment plant is proposed as a promising alternative lipid feedstock for biodiesel production. A deep study combining different type of raw materials (sludge coming from the oxic, anoxic and anaerobic steps of the biological treatment) with different technologies (liquid–liquid and solid–liquid extractions followed by acid catalysed transesterification and in situ extraction-transesterification procedure) allows a complete comparison of available technologies. Different parameters – contact time, catalyst concentration, pretreatments – were considered, obtaining more than 17% FAMEs yield after 50 min of sonication with the in situ procedure and 5% of H2SO4. This result corresponds to an increment of more than 65% respect to the best results reported at typical conditions. Experimental data were used to propose a mathematical model for this process, demonstrating that the mass transfer of lipids from the sludge to the liquid is the limiting step.

Influence of catalysts on co-combustion of sewage sludge and water hyacinth blends as determined by TG-MS analysis

o Pages 217-225

o Limao Huang, Candie Xie, Jingyong Liu, Xiaochun Zhang, KenLin Chang, Jiahong Kuo, Jian Sun, Wuming Xie, Li Zheng, Shuiyu Sun, Musa Buyukada, Fatih Evrendilek

Abstract

Effects of the three metal carbonates (K2CO3, Na2CO3, and MgCO3) were quantified on catalytic co-combustion of the sewage sludge and water hyacinth (SW) blend using a thermogravimetric-mass spectrometric (TG-MS) analysis and kinetics modeling. The main dominating steps of the catalysts were the organic volatile matter release and combustion stage. Weighted mean values of activation energy (Em) were estimated at 181.18 KJ·mol−1, 199.76 KJ·mol−1, 138.76 KJ·mol−1, and 177.88 KJ·mol−1 for SW, SW + 5% K2CO3, SW + 5% Na2CO3, and SW + 5% MgCO3, respectively. The lowest Em occurred with SW + 5% Na2CO3. Overall, catalyst effect on co-combustion appeared to be negligible as indicated by Gibbs free energy [pic]. The normalized intensities of SW + MgCO3 were strongest. The addition of Na2CO3 and MgCO3 to SW increased flue gases emissions (CO2, NO2, SO2, HCN, and NH3) of SW, whereas the addition of K2CO3 to SW reduced flue gases emissions from the entire combustion process.

Bioelectrochemical enhancement of methane production from highly concentrated food waste in a combined anaerobic digester and microbial electrolysis cell

o Pages 226-233

o Jungyu Park, Beom Lee, Donjie Tian, Hangbae Jun

Abstract

A microbial electrolysis cell (MEC) is a promising technology for enhancing biogas production from an anaerobic digestion (AD) reactor. In this study, the effects of the MEC on the rate of methane production from food waste were examined by comparing an AD reactor with an AD reactor combined with a MEC (AD + MEC). The use of the MEC accelerated methane production and stabilization via rapid organic oxidation and rapid methanogenesis. Over the total experimental period, the methane production rate and stabilization time of the AD + MEC reactor were approximately 1.7 and 4.0 times faster than those of the AD reactor. Interestingly however, at the final steady state, the methane yields of both the reactors were similar to the theoretical maximum methane yield. Based on these results, the MEC did not increase the methane yield over the theoretical value, but accelerated methane production and stabilization by bioelectrochemical reactions.

Hydrothermal pretreatment of bamboo sawdust using microwave irradiation

o Pages 234-241

o Leilei Dai, Chao He, Yunpu Wang, Yuhuan Liu, Roger Ruan, Zhenting Yu, Yue Zhou, Dengle Duan, Liangliang Fan, Yunfeng Zhao

Abstract

In the present study, the effect of temperature and residence time during microwave hydrothermal pretreatment (MHT) on hydrochar properties and pyrolysis behaviors was investigated. Experimental results indicated that higher heating value (HHV) and fixed carbon content gradually increased with increased pretreatment severity. Obvious reduction of oxygen content was found under MHT at 230 °C-15 min and 210 °C-35 min. Although lower mass yield was observed under severe conditions, corresponding energy yield was relatively higher. Crystallinity indexes of hydrochar demonstrated an upward trend with increased residence time. Unlike hydroxyl group, dissociation of acetyls was more favorable under prolonged residence time rather than increased temperature. Peaks in thermogravimetric and derivative thermogravimetric curves shifted to higher temperature region under severe conditions, indicating better thermal stability. Py-GC/MS analysis suggested that acids content was decreased but sugars increased with increased MHT severity. Moreover, compared to temperature, residence time was mainly responsible for acetic acid formation.

Ethanol production from bamboo using mild alkaline pre-extraction followed by alkaline hydrogen peroxide pretreatment

o Pages 242-249

o Zhaoyang Yuan, Yangbing Wen, Nuwan Sella Kapu

Abstract

A sequential two-stage pretreatment process comprising alkaline pre-extraction and alkaline hydrogen peroxide pretreatment (AHP) was investigated to convert bamboo carbohydrates into bioethanol. The results showed that mild alkaline pre-extraction using 8% (w/w) sodium hydroxide (NaOH) at 100 °C for 180 min followed by AHP pretreatment with 4% (w/w) hydrogen peroxide (H2O2) was sufficient to generate a substrate that could be efficiently digested with low enzyme loadings. Moreover, alkali pre-extraction enabled the use of lower H2O2 charges in AHP treatment. Two-stage pretreatment followed by enzymatic hydrolysis with only 9 FPU/g cellulose led to the recovery of 87% of the original sugars in the raw feedstock. The use of the pentose-hexose fermenting Saccharomyces cerevisiae SR8u strain enabled the utilization of 95.7% sugars in the hydrolysate to reach 4.6% w/v ethanol titer. The overall process also enabled the recovery of 62.9% lignin and 93.8% silica at high levels of purity.

Anaerobic digestion of organic fraction from hydrothermal liquefied algae wastewater byproduct

o Pages 250-258

o Sebastian Fernandez, Keerthi Srinivas, Andrew J. Schmidt, Marie S. Swita, Birgitte K. Ahring

Abstract

The wastewater stream from hydrothermal liquefaction (HTL) process used in biofuel production, contains a large amounts of organic compounds where several can be regarded as environmentally hazardous and requires significant treatment before disposal. In this study, semi-continuous anaerobic digestion is used to degrade the organic fraction of wastewater streams from HTL of the algae Tetraselmis (AgTet) and Chlorella (AgChlr). Results indicated high methane yields at 20–30% (v/v) HTL wastewater together with clarified manure, producing 327.2 mL/gVSin (or volatile solids in feed) for AgTet and 263.4 mL/gVSin for AgChlr. There was a significant reduction in methane production at concentrations higher than 40% (v/v) HTL wastewater in the feed, possibly due to the accumulation of chloride salts or inhibitory compounds such as pyridines, piperidines and pyrrolidines. This was further confirmed by comparing COD, salt and the ammonia concentrations of the effluents after anaerobic digestion at different concentrations of wastewater in manure.

Microbial dynamics of biofilm and suspended flocs in anammox membrane bioreactor: The effect of non-woven fabric membrane

o Pages 259-266

o Long-Fei Ren, Lu Lv, Qi Kang, Baoyu Gao, Shou-Qing Ni, Yi-Han Chen, Shiping Xu

Abstract

Membrane bioreactor with non-woven fabric membranes (NWMBR) is developing into a suitable method for anaerobic ammonium oxidation (anammox). As a carrier, non-woven fabric membrane divided total biomass into biofilm and suspended flocs gradually. Total nitrogen removal efficiency was maintained around 82.6% under nitrogen loading rate of 567.4 mg N/L/d after 260 days operation. Second-order substrate removal and Stover-Kincannon models were successfully used to simulate the nitrogen removal performance in NWMBR. High-throughput sequence was employed to elucidate the underlying microbial community dynamics. Candidatus Brocadia, Kuenenia, Jettenia were detected to affirm the dominant status of anammox microorganisms and 98.2% of anammox microorganisms distributed in biofilm. In addition, abundances of functional genes (hzs, nirK) in biofilm and suspended flocs were assessed by quantitative PCR to further investigate the coexistence of anammox and other microorganisms. Potential nitrogen removal pathways were established according to relevant nitrogen removal performance and microbial community.

Extraction of intracellular protein from Chlorella pyrenoidosa using a combination of ethanol soaking, enzyme digest, ultrasonication and homogenization techniques

o Pages 267-272

o Ruilin Zhang, Jian Chen, Xuewu Zhang

Abstract

Due to the rigid cell wall of Chlorella species, it is still challenging to effectively extract significant amounts of protein. Mass methods were used for the extraction of intracellular protein from microalgae with biological, mechanical and chemical approaches. In this study, based on comparison of different extraction methods, a new protocol was established to maximize extract amounts of protein, which was involved in ethanol soaking, enzyme digest, ultrasonication and homogenization techniques. Under the optimized conditions, 72.4% of protein was extracted from the microalgae Chlorella pyrenoidosa, which should contribute to the research and development of Chlorella protein in functional food and medicine.

Pyrolysis of Arundo donax L. to produce pyrolytic vinegar and its effect on the growth of dinoflagellate Karenia brevis

o Pages 273-281

o Hao Zheng, Cuizhu Sun, Xiaodong Hou, Miao Wu, Yuan Yao, Fengmin Li

Abstract

Harmful algal blooms (HABs) have become global environmental issues, and the demand for alternative algaecides is urgent. Pyrolytic vinegars (PVs) were pyrolyzed from giant reed at 300–600 °C to investigate the underlying mechanisms of their inhibitory effect on the red tide dinoflagellate Karenia brevis by sub-chronic toxicity experiments. The major components of PVs were acetic acid, phenols, aldehyde, ketone, and esters. The 96 h median effective concentration (96 h-EC50) values of PVs were 0.65–1.08 mL L−1, and PV300 showed the strongest inhibitory effect. The increased contents of reactive oxygen species (ROS) and malondialdehyde, antioxidant enzymes activities indicated that K. brevis cells were suffering from oxidative stress, leading to lipid oxidation and cell structure damage. The sites of ROS accumulation in the treated cells were chloroplasts and mitochondria. These results suggest the suitability of PVs as potential algaecides for HAB control, and also provide a new direction for biomass valorization.

Effect of hydrothermal carbonization on migration and environmental risk of heavy metals in sewage sludge during pyrolysis

o Pages 282-290

o Tingting Liu, Zhengang Liu, Qingfu Zheng, Qianqian Lang, Yu Xia, Nana Peng, Chao Gai

Abstract

The heavy metals distribution during hydrothermal carbonization (HTC) of sewage sludge, and pyrolysis of the resultant hydrochar was investigated and compared with raw sludge pyrolysis. The results showed that HTC reduced exchangeable/acid-soluble and reducible fraction of heavy metals and lowered the potential risk of heavy metals in sewage sludge. The pyrolysis favored the transformation of extracted/mobile fraction of heavy metals to residual form especially at high temperature, immobilizing heavy metals in the chars. Compared to the chars from raw sludge pyrolysis, the chars derived from hydrochar pyrolysis was more alkaline and had lower risk and less leachable heavy metals, indicating that pyrolysis imposed more positive effect on immobilization of heavy metals for the hydrochar than for sewage sludge. The present study demonstrated that HTC is a promising pretreatment prior to pyrolysis from the perspective of immobilization of heavy metals in sewage sludge.

Enhanced ethanol production by Clostridium ragsdalei from syngas by incorporating biochar in the fermentation medium

o Pages 291-301

o Xiao Sun, Hasan K. Atiyeh, Ajay Kumar, Hailin Zhang

Abstract

Biochar contains minerals and metals that can serve as nutrients for acetogens to produce ethanol via syngas fermentation. In this study, four fermentation media containing biochar from switchgrass (SGBC), forage sorghum (FSBC), red cedar (RCBC) and poultry litter (PLBC) were compared with standard yeast extract (YE) medium for syngas fermentation using Clostridium ragsdalei. Fermentations were performed in 250 mL bottle reactors at 150 rpm and 37 °C with syngas containing CO:H2:CO2 (40:30:30) by volume. Results showed that media containing RCBC and PLBC improved ethanol production by 16.3% and 58.9%, respectively, compared to YE medium. C. ragsdalei consumed 69% more H2 and 40% more CO in PLBC medium compared to YE medium. However, no enhancement of ethanol production was observed in SGBC and FSBC media. The highest release of Na, K, Ca, Mg, S and P was from PLBC, which was considered to contribute in enhancement of ethanol production.

Characteristics of co-hydrothermal carbonization on polyvinyl chloride wastes with bamboo

o Pages 302-309

o Zhongliang Yao, Xiaoqian Ma

Abstract

The PVC waste and bamboo were treated by co-hydrothermal carbonization (co-HTC) at three different temperatures. The inorganic-Cl could be removed from the carbon rich solid products (hydrochar) in the form of HCl via hydrolysis, elimination, substitution and aromatization. Due to the high carbon content, the hydrochar could be applied as premium fuel. Bamboo had a synergistic effect on dechlorination with PVC in the HTC process. The bamboo could accelerate the HTC dechlorination of PVC at 200 °C because it strengthened the substitution of [pic]Cl with [pic]OH. While at 230 and 260 °C, the existence of bamboo hindered the dechlorination of PVC in HTC. Thermogravimetric analysis showed the combustion performance of hydrochar was better than the raw samples at 200 °C. Owing to the low chlorine content, low ignition temperature and the superior combustion performance, the M-260 can be adopted as alternative fuels for coal.

Hydrothermal carbonization of Opuntia ficus-indica cladodes: Role of process parameters on hydrochar properties

o Pages 310-318

o Maurizio Volpe, Jillian L. Goldfarb, Luca Fiori

Abstract

Opuntia ficus-indica cladodes are a potential source of solid biofuel from marginal, dry land. Experiments assessed the effects of temperature (180–250 °C), reaction time (0.5–3 h) and biomass to water ratio (B/W; 0.07–0.30) on chars produced via hydrothermal carbonization. Multivariate linear regression demonstrated that the three process parameters are critically important to hydrochar solid yield, while B/W drives energy yield. Heating value increased together with temperature and reaction time and was maximized at intermediate B/W (0.14–0.20). Microscopy shows evidence of secondary char formed at higher temperatures and B/W ratios. X-ray diffraction, thermogravimetric data, microscopy and inductively coupled plasma mass spectrometry suggest that calcium oxalate in the raw biomass remains in the hydrochar; at higher temperatures, the mineral decomposes into CO2 and may catalyze char/tar decomposition.

Towards physicochemical and biological effects on detachment and activity recovery of aging biofilm by enzyme and surfactant treatments

o Pages 319-326

o Hui Huang, Qisheng Yu, Hongqiang Ren, Jinju Geng, Ke Xu, Yan Zhang, Lili Ding

Abstract

In order to explore physicochemical and biological effects on detachment and activity recovery of aging biofilm by enzyme and surfactant treatments, two kinds of biofilm processes, i.e. biological aeration filter (BAF) and moving bed biofilm reactor (MBBR), and multiple indicators including water quality, biofilm morphology, activity and microbial community structure, were employed. Results showed that detachment of aging biofilm was mainly attributed by extracellular polymeric substance (EPS) solubilization and dispersion, and activity recovery of aging biofilm mainly depended on biological effects of dominant bacteria. Phosphorus metabolism related bacteria, such as Microbacterium and Micropruina, were responsible for BAF biofilm regeneration. More abundant microbial community structure of MBBR regenerated biofilm was found, and biofilm activity was not only related to phosphorus metabolism related bacteria, but also to denitrifying bacteria. Rhamnolipid performed best on aging biofilm detachment and regeneration, giving a clue for effective activation of aging biofilm in wastewater treatment systems.

Flotation removal of the microalga Nannochloropsis sp. using Moringa protein–oil emulsion: A novel green approach

o Pages 327-331

o Ganesan Kandasamy, Sitti Raehanah Muhamad Shaleh

Abstract

A new approach to recover microalgae from aqueous medium using a bio-flotation method is reported. The method involves utilizing a Moringa protein extract – oil emulsion (MPOE) for flotation removal of Nannochloropsis sp. The effect of various factors has been assessed using this method, including operating parameters such as pH, MPOE dose, algae concentration and mixing time. A maximum flotation efficiency of 86.5% was achieved without changing the pH condition of algal medium. Moreover, zeta potential analysis showed a marked difference in the zeta potential values when increase the MPOE dose concentration. An optimum condition of MPOE dosage of 50 ml/L, pH 8, mixing time 4 min, and a flotation efficiency of greater than 86% was accomplished. The morphology of algal flocs produced by protein-oil emulsion flocculant were characterized by microscopy. This flotation method is not only simple, but also an efficient method for harvesting microalgae from culture medium.

Comparison of pre- and inter-stage aerobic treatment of wastewater sludge: Effects on biogas production and COD removal

o Pages 332-339

o Charlotte Rennuit, Jin Mi Triolo, Søren Eriksen, Julie Jimenez, Hélène Carrère, Sasha D. Hafner

Abstract

The aim of this study was to investigate thermophilic (55 °C) aerobic digestion (TAD) as pre- and inter-stage treatment of sludge anaerobic digestion and to analyse the change in organic matter accessibility and complexity. Pre-treatment decreased methane yield (up to −70%), due to oxidation losses whereas inter-stage treatment slightly improved overall methane yield (+2.6%) and total COD removal (+5%) compared to control. Anaerobic degradability and COD removal in the second anaerobic stage significantly increased, by 13–40%. Organic matter fractionation showed that TAD led to an increase in sludge organic matter accessibility in all cases. Organic matter complexity, measured by fluorimetry, increased after TAD pre-treatment whereas it remained constant after inter-stage treatment. TAD was shown to be more efficient if applied to a more recalcitrant substrate and should thus be used as inter-stage treatment to avoid decreasing methane production.

Effects of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor for municipal wastewater treatment

o Pages 340-346

o C. Chen, W.S. Guo, H.H. Ngo, S.W. Chang, D.D. Nguyen, J. Zhang, S. Liang, J.B. Guo, X.B. Zhang

Abstract

This study aimed to evaluate the impact of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor (SAAMB-AnGMBR) in municipal wastewater treatment. The results showed that organic removal efficiencies were above 94% at all C/N conditions. Nutrient removal was over 91% at C/N ratio of 100/5 but was negatively affected when decreasing C/N ratio to 100/10. At lower C/N ratio (100/10), more noticeable membrane fouling was caused by aggravated cake formation and pore clogging, and accumulation of extracellular polymeric substances (EPS) in the mixed liquor and sludge cake as a result of deteriorated granular quality. Foulant analysis suggested significant difference existed in the foulant organic compositions under different C/N ratios, and humic substances were dominant when the fastest fouling rate was observed. The performance of the hybrid system was found to recover when gradually increasing C/N ratio from 100/10 to 100/5.

Microbiome dynamics and adaptation of expression signatures during methane production failure and process recovery

o Pages 347-356

o Anja Grohmann, Steffen Fehrmann, Yevhen Vainshtein, Nicola L. Haag, Franziska Wiese, Philip Stevens, Hans-Joachim Naegele, Hans Oechsner, Thomas Hartsch, Kai Sohn, Christian Grumaz

Abstract

This study aimed to uncover microbial dynamics and transcriptional adaptations during mesophilic AD of maize silage and slurry. While one digester performed under optimal conditions, the investigations also evaluated the microbiome during a temperature drop mediated process failure accompanied by acidification and how it contributed to a process recovery. Composition and pathway activities were analyzed by whole genome shotgun (WGS) and metatranscriptome sequencing, respectively. A biodiversity of 112 species was observed with noticeable shifts over process time. Although four distinct groups of microbes could be identified with a correlating versatility according to substrate and to process disturbance, also tremendous effects on gene expression were monitored especially of the archaeal methane metabolism. Particularly, the expression of acetogenotrophic methanogenesis related genes was identified to be relevant for process regeneration.

Resolving bacterial contamination of fuel ethanol fermentations with beneficial bacteria – An alternative to antibiotic treatment

o Pages 357-362

o Joseph O. Rich, Kenneth M. Bischoff, Timothy D. Leathers, Amber M. Anderson, Siqing Liu, Christopher D. Skory

Abstract

Fuel ethanol fermentations are not performed under aseptic conditions and microbial contamination reduces yields and can lead to costly “stuck fermentations”. Antibiotics are commonly used to combat contaminants, but these may persist in the distillers grains co-product. Among contaminants, it is known that certain strains of lactic acid bacteria are capable of causing stuck fermentations, while other strains appear to be harmless. However, it was not previously known whether or how these strains interact one with another. In this study, more than 500 harmless strains of lactic acid bacteria were tested in a model system in combination with strains that cause stuck fermentations. Among these harmless strains, a group of beneficial strains was identified that restored ethanol production to near normal levels. Such beneficial strains may serve as an alternative approach to the use of antibiotics in fuel ethanol production.

Pyrolysis of Date palm waste in a fixed-bed reactor: Characterization of pyrolytic products

o Pages 363-369

o Gmar Bensidhom, Aïda Ben Hassen-Trabelsi, Koray Alper, Maher Sghairoun, Kaouther Zaafouri, Ismail Trabelsi

Abstract

The pyrolysis of several Tunisian Date Palm Wastes (DPW): Date Palm Rachis (DPR), Date Palm Leaflets (DPL), Empty Fruit Bunches (EFB) and Date Palm Glaich (DPG) was run using a fixed-bed reactor, from room temperature to 500 °C, with 15 °C/min as heating rate and −5 °C as condensation temperature, in order to produce bio-oil, biochar and syngas. In these conditions, the bio-oil yield ranges from 17.03 wt% for DPL to 25.99 wt% for EFB. For the biochar, the highest yield (36.66 wt%) was obtained for DPL and the lowest one (31.66 wt%) was obtained from DPG while the syngas production varies from 39.10 wt% for DPR to 46.31 wt% DPL. The raw material and pyrolysis products have been characterized using elemental analysis thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). The syngas composition has been characterized using gas analyzer.

Polyethylene imine modified hydrochar adsorption for chromium (VI) and nickel (II) removal from aqueous solution

o Pages 370-379

o Yuanji Shi, Tao Zhang, Hongqiang Ren, Andrea Kruse, Ruofan Cui

Abstract

An adsorbent hydrochar was synthesized from corn cobs and modified with polyethylene imine (PEI). The hydrochars before and after modification were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis. FTIR and XPS revealed that the PEI was grafted onto the hydrochar via ether and imine bonds formed with glutaraldehyde. The maximum adsorption capacities for Cr(VI) (33.663 mg/g) and Ni(II) (29.059 mg/g) on the modified hydrochars were 365% and 43.7% higher, respectively, than those on the unmodified hydrochar. A pseudo-second-order model described the adsorption of Ni(II) and Cr(VI) on all the adsorbents. The adsorption of Cr(VI) was endothermic, spontaneous, increased disorder, and obeyed the Langmuir model. By contrast, the adsorption of Ni(II) was exothermic, spontaneous, decreased disorder, and obeyed the Freundlich model. XPS confirmed that the adsorption sites and mechanisms for Ni(II) and Cr(VI) on the modified hydrochars were different.

Enhancement of extracellular lipid production by oleaginous yeast through preculture and sequencing batch culture strategy with acetic acid

o Pages 395-401

o Xiang-feng Huang, Yi Shen, Hui-juan Luo, Jia-nan Liu, Jia Liu

Abstract

Oleaginous yeast Cryptococcus curvatus MUCL 29819, an acid-tolerant lipid producer, was tested to spill lipids extracellularly using different concentrations of acetic acid as carbon source. Extracellular lipids were released when the yeast was cultured with acetic acid exceeding 20 g/L. The highest production of lipid (5.01 g/L) was obtained when the yeast was cultured with 40 g/L acetic acid. When the yeast was cultivated with moderate concentration (20 g/L) of acetic acid, lipid production was further increased by 49.6% through preculture with 40 g/L acetic acid as stimulant. When applying high concentration (40 g/L) of acetic acid as carbon source in sequencing batch cultivation, extracellular lipids accounted up to 50.5% in the last cycle and the extracellular lipids reached 5.43 g/L through the whole process. This study provides an effective strategy to enhance extracellular lipid production and facilitate the recovery of microbial lipids.

Ammonia and methane emissions during drying of dewatered biogas digestate in a two-belt conveyor dryer

o Pages 419-425

o S. Awiszus, K. Meissner, S. Reyer, J. Müller

Abstract

Aim of the present study was to identify type and amount of emissions during the drying of biogas digestate in a two-belt conveyor dryer at different temperature settings and to investigate the effect on its nutrient content. Furthermore, the possibility of recovering nitrogen from the exhaust air was investigated. Emissions of CH4, CO2 and NH3 were measured by Fourier transform infrared spectroscopy. Biogas is mainly composed of CH4 and CO2, hence gas release from the digestate during drying was expected to increase the concentration of these components. Although CO2concentration was elevated above the background concentration, CH4 did not exceed the background concentration. Maximum NH3 concentration of 183.3 mg·m−3 was detected during drying. A NH3 concentration of 10.8 mg·m−3 was measured in the exhaust air of the ammonia scrubber, which is equal to a NH3 reduction rate of 94%.

Growth kinetic and fuel quality parameters as selective criterion for screening biodiesel producing cyanobacterial strains

o Pages 453-462

o Manickam Gayathri, Sumathy Shunmugam, Arumugam Vanmathi Mugasundari, Pattanathu K.S.M. Rahman, Gangatharan Muralitharan

Abstract

The efficiency of cyanobacterial strains as biodiesel feedstock varies with the dwelling habitat. Fourteen indigenous heterocystous cyanobacterial strains from rice field ecosystem were screened based on growth kinetic and fuel parameters. The highest biomass productivity was obtained in Nostoc punctiforme MBDU 621 (19.22 mg/L/day) followed by Calothrix sp. MBDU 701 (13.43 mg/L/day). While lipid productivity and lipid content was highest in Nostoc spongiaeforme MBDU 704 (4.45 mg/L/day and 22.5% dwt) followed by Calothrix sp. MBDU 701 (1.54 mg/L/day and 10.75% dwt). Among the tested strains, Nostoc spongiaeforme MBDU 704 and Nostoc punctiforme MBDU 621 were selected as promising strains for good quality biodiesel production by Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) and Graphical Analysis for Interactive Assistance (GAIA) analysis.

Lead removal by a magnetic biochar derived from persulfate-ZVI treated sludge together with one-pot pyrolysis

o Pages 463-470

o Yi-di Chen, Shih-Hsin Ho, Dawei Wang, Zong-su Wei, Jo-Shu Chang, Nan-qi Ren

Abstract

In this study, a novel method to treat the persulfate-ZVI dewatered WAS by producing a magnetic biochar as an environmentally friendly biosorbent (nZVI-WSBC) to remove heavy metals (HMs) from wastewaters was proposed. The nZVI-WSBC exhibited good adsorption property of Pb2+ and the adsorption isotherm data were fitted well to Langmuir isotherm. Corresponding reaction kinetics fitted well with the pseudo second-order adsorption model. Notably, nZVI-WSBC was successfully used for efficient removal of HMs from real. This study comprehensively demonstrates the mechanisms between Pb2+ and nZVI-WSBC surfaces, providing a breakthrough in making a sustainable biosorbent from the dewatered iron-containing WAS.

Electricity generation and in situ phosphate recovery from enhanced biological phosphorus removal sludge by electrodialysis membrane bioreactor

o Pages 471-476

o Yi-Kun Geng, Yunkun Wang, Xin-Rong Pan, Guo-Ping Sheng

Abstract

In this study, a novel electrodialysis membrane bioreactor was used for EBPR sludge treatment for energy and phosphorus resource recovery simultaneously. After 30 days stable voltage outputting, the maximum power density reached 0.32 W/m3. Over 90% of phosphorus in EBPR sludge was released while about 50% of phosphorus was concentrated to 4 mmol/L as relatively pure phosphate solution. Nitrogen could be removed from EBPR sludge by desalination and denitrification processes. This study provides an optimized way treating sludge for energy production and in situ phosphorus recovery.

Remedying acidification and deterioration of aerobic post-treatment of digested effluent by using zero-valent iron

o Pages 477-485

o Shen Wang, Dan Zheng, Shuang Wang, Lan Wang, Yunhui Lei, Ze Xu, Liangwei Deng

Abstract

This study presents a novel strategy for remedying acidification and improving the removal efficiency of pollutants from digested effluent by using Zero-Valent Iron (iron scraps) in a sequencing batch reactor. Through this strategy, the pH increased from 5.7 (mixed liquid in the reactor without added ZVI) to 7.8 (reactors with added ZVI) because of Fe0 oxidation and NO3− reduction. The removal efficiencies of COD increased from 11.5% to 77.5% because of oxidation of ferric ion and [pic]OH produced in chemical reactions of ZVI with oxygen and because of flocculation of iron ions. The removal efficiencies of total nitrogen rose from 1.83% to 93.3% probably because of autotrophic denitrification using electron donors produced by the corrosion of iron, as well as the favorable conditions for anammox due to iron ions. Total phosphorus increased from −25.8% to 77.1% because of the increase in pH and the precipitation with iron ions.

Process performance and modelling of anaerobic digestion using source-sorted organic household waste

o Pages 486-495

o Benyamin Khoshnevisan, Panagiotis Tsapekos, Merlin Alvarado-Morales, Irini Angelidaki

Abstract

Three distinctive start-up strategies of biogas reactors fed with source-sorted organic fraction of municipal solid waste were investigated to reveal the most reliable procedure for rapid process stabilization. Moreover, the experimental results were compared with mathematical modeling outputs. The initial inoculations to start-up the reactors were 10, 50 and 100% of the final working volume. While a constant feeding rate of 7.8 gVS/d was considered for the control reactor, the organic loading rate for fed-batch reactors with 10 and 50% inoculation was progressively increased during a period of 60 and 13 days, respectively. The results clearly demonstrated that an exponentially feeding strategy, considering 50% inoculation relative to final volume, can significantly decrease the alternatively prolonged period to reach steady conditions, as observed by high biogas and methane production rates. The combination of both experimental and modelling/simulation succeeded in optimizing the start-up process for anaerobic digestion of biopulp under mesophilic conditions.

Application of commercial and non-commercial immobilized lipases for biocatalytic production of ethyl lactate in organic solvents

o Pages 496-503

o Michalis Koutinas, Chrystalleni Yiangou, Natália M. Osório, Katerina Ioannou, Albert Canet, Francisco Valero, Suzana Ferreira-Dias

Abstract

This study explores the potential for enhancing the production of ethyl lactate (EL), a green solvent, through enzymatic esterification. Different solvents were compared as organic media for conversion of lactate and ethanol into EL, catalyzed by Novozym 435. Chloroform and hexane were the most effective in low acid concentrations (0.01–0.1 M) exhibiting maximum EL yields of 88% and 75% respectively. The yield of EL improved as the solvent’s Log P increased up to a value of 2. Non-commercial immobilized biocatalysts consisting heterologous Rhizopous oryzae (rROL) and Candida rugosa (CRL) lipases immobilized on hydrophobic supports were compared to commercial biocatalysts clarifying that Novozym 435 and Lipozyme RM IM could be efficiently applied. Operational stability tests were conducted using Novozym 435, which retained higher activity in chloroform as compared to hexane. Although non-commercial biocatalysts were not competitive in esterification, they exhibited significant activity towards hydrolysis constituting a valuable alternative to higher-cost options.

Effects of hydrothermal treatment on the pyrolysis behavior of Chinese fan palm

o Pages 504-512

o Zhongliang Yao, Xiaoqian Ma

Abstract

The effect of hydrothermal treatment (HTT) on Chinese fan palm pyrolysis was investigated. It indicated that HTT could effectively remove a large portion of alkali/alkaline earth metals and disrupt the chemical structure to a certain extent. HTT delayed the initial decomposition temperature but accelerated the pyrolysis process completely. HTT also increased the relative contents of both sugars and hydrocarbons in pyrolysis. At 210 °C, HTT had the most significant promotion effect on the sugars formation with the relative content of 30.58%. While, The relative content of phenols, acids, furans, aldehydes, esters and CO2 decreased more or less after HTT. With increasing pyrolysis temperature, the relative content of most groups of chemicals except hydrocarbons decreased. Response contours were analyzed to find the optimal reaction conditions for generating acids, phenols, sugars and hydrocarbons, respectively. The results indicated both pyrolysis temperature and HTT temperature had distinct influence on relative contents of products.

Integrating microalgae tertiary treatment into activated sludge systems for energy and nutrients recovery from wastewater

o Pages 513-519

o Dulce Maria Arias, Maria Solé-Bundó, Marianna Garfí, Ivet Ferrer, Joan García, Enrica Uggetti

Abstract

In this study, microalgae digestate and secondary effluent were used to grow microalgae in a tertiary wastewater treatment, and then, the biomass was co-digested for biogas generation. A 30 L closed-photobioreactor was used for microalgae cultivation. The biomass, mainly composed by Scenedesmus sp., reached and maintained a concentration of 1.1 gTSS/L during 30 days. A complete removal of N-NH4+ and P-PO43− and high nitrates and organic matter removals were achieved (58% N-NO3− and 70% COD) with 8 d of HRT. The potential biogas production of the cultivated microalgae was determined in batch tests. To improve their biodegradability, a novel method combining their co-digestion with activated sludge after a simultaneous autohydrolysis co-pretreatment was evaluated. After the co-pretreatment, the methane yield increased by 130%. Thus, integrating microalgae tertiary treatment into activated sludge systems is a promising and feasible solution to recover energy and nutrients from waste, improving wastewater treatment plants sustainability.

Microbial fuel cell powered by lipid extracted algae: A promising system for algal lipids and power generation

o Pages 520-527

o Amitap Khandelwal, Ankisha Vijay, Ambesh Dixit, Meenu Chhabra

Abstract

In this study, a promising microbial fuel cell (MFC) system has been developed, wherein algae is cultivated in the cathode chamber, algae biomass is harvested and lipids are extracted. The lipid extracted algal (LEA) biomass was then used as an electron donor substrate. The performance of MFCs fed with LEA biomass was compared with that of fruit waste fed MFCs (FP-MFCs), wherein LEA-fed MFC was superior in all aspects. Power density of 2.7 W m−3 was obtained by LEA-fed MFCs which is 145% and 260% higher than FP MFC and control MFC respectively. The volumetric algae productivity of 0.028 kg m−3 day−1 in cathode chamber was achieved. The system was able to generate 0.0136 kWh Kg−1 COD day−1 of electric energy and 0.0782 kWh m−3 day−1 of algal oil energy. The proposed system is a net energy producer which does not rely heavily on the external supply of electron donor substrates.

Biocatalytic degradation of pharmaceuticals, personal care products, industrial chemicals, steroid hormones and pesticides in a membrane distillation-enzymatic bioreactor

o Pages 528-536

o Muhammad B. Asif, Faisal I. Hai, Jinguo Kang, Jason P. van de Merwe, Frederic D.L. Leusch, William E. Price, Long D. Nghiem

Abstract

Laccase-catalyzed degradation of a broad spectrum of trace organic contaminants (TrOCs) by a membrane distillation (MD)-enzymatic membrane bioreactor (EMBR) was investigated. The MD component effectively retained TrOCs (94–99%) in the EMBR, facilitating their continuous biocatalytic degradation. Notably, the extent of TrOC degradation was strongly influenced by their molecular properties. A significant degradation (above 90%) of TrOCs containing strong electron donating functional groups (e.g., hydroxyl and amine groups) was achieved, while a moderate removal was observed for TrOCs containing electron withdrawing functional groups (e.g., amide and halogen groups). Separate addition of two redox-mediators, namely syringaldehyde and violuric acid, further improved TrOC degradation by laccase. However, a mixture of both showed a reduced performance for a few pharmaceuticals such as primidone, carbamazepine and ibuprofen. Mediator addition increased the toxicity of the media in the enzymatic bioreactor, but the membrane permeate (i.e., final effluent) was non-toxic, suggesting an added advantage of coupling MD with EMBR.

Effectiveness and mechanisms of phosphate adsorption on iron-modified biochars derived from waste activated sludge

o Pages 537-544

o Qi Yang, Xiaolin Wang, Wei Luo, Jian Sun, Qiuxiang Xu, Fei Chen, Jianwei Zhao, Shana Wang, Fubing Yao, Dongbo Wang, Xiaoming Li, Guangming Zeng

Abstract

Excessive discharge of phosphate (P) into the surface water is the key factor to cause the eutrophication, so its removal has aroused much attention in recent years. In this study, different iron modification (chemical co-precipitation of Fe3+/Fe2+ or FeCl3 impregnation) was used to improve the phosphate adsorption capacity of waste activated sludge (WAS)-based biochar. Comparative tests demonstrated that the FeCl3-impregnated WAS-based biochar exhibited much superior phosphate adsorption capacity (111.0 mg/g) in all as-prepared samples and performed well even under the interferences with pH and coexisting ions. X-ray diffraction (XRD) analyzes indicated that the iron in FeCl3-impregnated WAS-based biochar existed mainly in amorphous phase, as hematite and amorphous hydroxides forms, which was of great benefit to the phosphate adsorption. Besides, ligand exchange plays important role in the adsorption of phosphate. The WAS-based biochar kept over 60% phosphate removal efficiency after five recycles.

Parametric study and global sensitivity analysis for co-pyrolysis of rape straw and waste tire via variance-based decomposition

o Pages 545-552

o Li Xu, Yong Jiang, Rong Qiu

Abstract

In present study, co-pyrolysis behavior of rape straw, waste tire and their various blends were investigated. TG-FTIR indicated that co-pyrolysis was characterized by a four-step reaction, and H2O, C[pic]H, O[pic]H, CO2 and C[pic]O groups were the main products evolved during the process. Additionally, using BBD-based experimental results, best-fit multiple regression models with high R2-pred values (94.10% for mass loss and 95.37% for reaction heat), which correlated explanatory variables with the responses, were presented. The derived models were analyzed by ANOVA at 95% confidence interval, F-test, lack-of-fit test and residues normal probability plots implied the models described well the experimental data. Finally, the model uncertainties as well as the interactive effect of these parameters were studied, the total-, first- and second-order sensitivity indices of operating factors were proposed using Sobol’ variance decomposition. To the authors’ knowledge, this is the first time global parameter sensitivity analysis has been performed in (co-)pyrolysis literature.

Genome hunting of carbonyl reductases from Candida glabrata for efficient preparation of chiral secondary alcohols

o Pages 553-560

o Guochao Xu, Yaping Zhang, Yue Wang, Ye Ni

Abstract

In this work, genome hunting strategy was adopted in screening for reductases from Candida glabrata. A total of 37 putative reductases were successfully expressed in E. coli BL21(DE3). A substrate library containing 32 substrates was established for characterization of each reductase by average specific activity and Shannon-Wiener index. Among them, Cg26 was identified with the highest efficiency and wider substrate spectrum in the reduction of prochiral ketones, with average activity and Shannon-Wiener index of 8.95 U·mg−1 and 2.82. Cg26 is a member of ‘extended’ short chain dehydrogenase/reductase superfamily. Ni2+ could improve its activity. As much as 150 g·L−1 ethyl 2-oxo-4-phenylbutyrate could be completely converted by 10 g·L−1 Cg26. This study provides evidence for this newly identified Cg26 in the preparation of chiral secondary alcohols.

Enhanced growth and fatty acid accumulation of microalgae Scenedesmus sp. LX1 by two types of auxin

o Pages 561-567

o Guo-Hua Dao, Guang-Xue Wu, Xiao-Xiong Wang, Lin-Lan Zhuang, Tian-Yuan Zhang, Hong-Ying Hu

Abstract

Microalgae are potential candidates for the production of valuable products, such as renewable biodiesel, health products and pigments. However, low biomass productivity has restricted their large-scale applications. In this study, the effects of two auxins (one natural type of indole-3-acetic acid (IAA) and the other synthetic type of 2,4-dichlorophenoxyacetic acid (2,4-D)) on the growth and fatty acid methyl esters (FAMEs) production of a freshwater microalgae Scenedesmus sp. LX1 were investigated. Both auxins showed a “low dosage-promotion and high dosage-inhibition” effect on the growth and FAMEs accumulation. The optimum dosage of IAA and 2,4-D were 1 mg L−1 and 0.1 mg L−1, respectively. Moreover, the IAA could increase the monounsaturated fatty acid content. The auxins may promote the growth by enhancing the photosynthetic activity through increasing chlorophyll contents. Therefore, auxin significantly enhanced microalgal growth and FAMEs accumulation, and has a potential for application in developing efficient microalgal cultivation.

Conversion of levulinic acid into alkyl levulinates: Using lipase immobilized on meso-molding three-dimensional macroporous organosilica as catalyst

o Pages 568-575

o Liya Zhou, Ying He, Li Ma, Yanjun Jiang, Zhihong Huang, Luyan Yin, Jing Gao

Abstract

For conversion of biomass-derived levulinic acid into alkyl levulinates, a novel kind of lipase-based biocatalyst was prepared through immobilized lipase B from C. antarctica (CALB) on organosilica material with highly ordered 3D macroporous organosilica frameworks and a 2D hexagonal meso-structure (named 3DOM/m-OS) for the first time. The catalytic performance of the immobilized lipase (NER@3DOM/m-OS) was investigated. NER@3DOM/m-OS was used as biocatalyst to catalyze the esterification reaction between levulinic acid (LA) and n-butanol. Under optimized reaction conditions, 74.59% of ester yield was achieved after 12 h of reaction. NER@3DOM/m-OS was also used to production of other alkyl levulinates, the ester yields increased to 84.51% (octyl levulinate) and 91.14% (dodecyl levulinate), respectively. When NER@3DOM/m-OS was used repeatedly in batch reactions, the ester yields of n-butyl, octyl, and dodecyl levulinate could retain 46.18%, 82.33% and 81.25% after 9 reaction cycles, respectively, which was better than commercial lipase Novozym 435 under the same condition.

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