Split Addition of Nitrogen-Rich Substrate at Thermophilic and Mesophilic Stages of Composting: Effect on Green House Gases Emission and Quality of Compost

Composting as a solution to the increasing generation of municipal solid waste (MSW), also contribute to GHGs emission when not controlled and could lack some basic nutrients, especially nitrogen. This study assessed the split-additions of nitrogen-rich substrate to composting materials and their effect on GHGs emissions as well as the quality of the composts. Nitrogen-rich substrates formulated from pig and goat manure were co-composted with MSW for a 12-weeks period by split adding at mesophilic (˚C) and thermophilic (>50˚C) stages in five different treatments. Representative samples from the compost were taken from each treatment for physicochemical, heavy metals and bacteriological analysis. In-situ CH4, CO2, N2O gas emissions were also analyzed weekly during composting. It was observed that all the treatments showed significant organic matter decomposition, reaching thermophilic temperatures in the first week of composting. The absence affects the suitable agronomic properties. All nitrogen-rich substrate applied at thermophilic stage (Treatment two) recorded the highest N, P and K concentrations of 1.34%, 0.97% and 2.45%, respectively with highest nitrogen retention. In terms of GHG emissions, CO2 was highest at the thermophilic stage when N-rich substrate was added in all treatment, while CH4 was highest in the mesophilic stage with N-rich substrate addition. N2O showed no specific trend in the treatments. Split addition of the N-rich substrate for co-composting of MSW produced compost which is stable, has less nutrient loss and low GHG emissions. Split addition of a nitrogen-rich substrate could be an option for increasing the fertilizer value of MSW compost.

Characterization of apparent sulfur oxidation activity of thermophilic archaea in bioleaching of chalcopyrite

The apparent sulfur oxidation activities of four pure thermophilic archaea, Acidianus brierleyi （JCM 8954）, Metallosphaera sedula （YN 23）, Acidianus manzaensis （YN 25） and Sulfolobus metallicus （YN 24） and their mixture in bioleaching chalcopyrite were compared, which were characterized indirectly by the evolution of the cells concentration, pH value and sulfate ions concentration in solution. The results show that the mixed culture contributed significantly to the raising of leaching rate, which suggests that the mixed culture had a higher sulfur oxidation activity than the pure culture. Meanwhile, the results also indicate that the changes of parameters characterizing the sulfur oxidation activity of thermophilic archaea are often influenced by many factors, so it is hard to reflect accurately the specific sulfur oxidation activities among the different sulfur-oxidizing microbes when bioleaching chalcopyrite at different conditions. Accordingly, an efficient method to characterize microbial sulfur oxidation activity appears to be desirable.

Surface species of chalcopyrite during bioleaching by moderately thermophilic bacteria

X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses were carried out to investigate the surface species and interfacial reactions during bioleaching of chalcopyrite by different strains of moderately thermophilic bacteria （45 °C）. Results show that monosulfide （CuS）, disulfide （S22？）, polysulfide （Sn2？）, elemental sulfur （S0） and sulfate （SO42？） are the main intermediate species on the surface of chalcopyrite during bioleaching byA. caldus,S. thermosulfidooxidans andL. ferriphilum. The low kinetics of dissolution of chalcopyrite inA. caldus can be mainly attributed to the incomplete dissolution of chalcopyrite and the passivation layer of polysulfide. Polysulfide and jarosite should be mainly responsible for the passivation of chalcopyrite in bioleaching byL. ferriphilumorS. thermosulfidooxidans. However, elemental sulfur should not be the main composition of passivation layer of chalcopyrite during bioleaching.

Effect of moderately thermophilic bacteria on metal extraction and electrochemical characteristics for zinc smelting slag in bioleaching system

The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm-1 and 1193 cm-1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.

CHARACTERISTICS OF THERMOPHILIC ANAEROBIC ACIDOGENESIS OF STARCH WASTEWATER

Acidogenic dissimilation of synthetic starch wastewater (1 000～10 000 mg COD·L -1 ) was studied in a thermophilic (55 ℃) upflow anaerobic sludge blanket (UASB) reactor.The production of volatile fatty acids (VFA) was proportional to the chemical oxygen demand (COD) loading rate.The yield of VFA was around 0.28 g VFA/g COD over the COD loading rate from 1.25 to 30 g COD·L -1 ·d -1 and the hydraulic retention time from 8.8 h to 24 h.Distribution of organic acids,the contents of propionic and butyric acids in the effluent in particular were also dependent on the COD loading rate.The thermophilic UASB reactor showed a stable performance on hydrolysis and acidogenesis of starch as well as suspended solid removal at short hydraulic retention times and high influent pH(10～11),during the operation of 110 d.

Research on the Nature of Thermophilic Anaerobic Ethanol Producer Thermo anaerobacter sp DF3 in Petroleum Reservoirs

[Objective] The aim was to study the physiological and biochemical char- acteristics of Thermoanaerobacter sp DF3 in petroleum reservoirs and optimize the culture plan of producing ethanol from xylose. [Method] DF3, an anaerobic bacillus producing ethanol, was isolated from produced liquid from oil layer of Dagang oil field with anaerobic isolation technique. The phylogenetic position was analyzed by physiological and biochemical identification and phylogeny of 16S rDNA sequence. The metabolites were analyzed by gas chromatograph. [Result] The strain DF3 was a strict anaerobic thermophilic bacterium, which was straight in rod shape,and gram negative. Besides, it was 0.42 μmx（1.60-5.20） iJm in length. The strains can be soli- tary,in pairs or string and apical spore usually produced. Its growth temperature was 45-78 and 65 ℃ was the optimum. Many substances could be used as carbon sources, including glucose, xylose, fructose, ribose, mannose, arabinose, sucrose, galactose, lactose, cellobiose, melizitose, raffinose-, and starch. The similarity between strain DF3 and T. pseudoethanolicus achieved 99.7%. The main product of glucose and xylose fermentation was ethanol. After the culture plan was optimized,the final concentration of ethanol was 2.0 g/L. [Conclusion] It was proved through experiments that the strain DF3 was one of the strains with higher activity to produce ethanol at present and it could produce 2.0 g/L ethanol from xylose metabolization at 65 ℃. It has been demonstrated that DF3 is one of the known strains with high-production to produce ethanol,for example, 2.0 g/L ethano at 65℃. Presently, all the high-yield ethanol can be produced from metabolic xylose strains of metabolic xylose were isolat- ed by foreign countries, therefore, isolation of strain DF3 has provided an excellent original strain for studying ethanol production from lignocellulose in China.

A culture-dependent survey of thermophilic bacteria from hot springs in Xiamen area in China

Microbes are believed to play important roles in ecosystem function in many environments.The hot springs of Xiamen Island are close to the Xiamen Sea,and may have some characteristics different from those of inland hot springs.Microbes living in the hot springs of Xiamen may have new characteristics.However,little is known about microbial communities of hot springs close to the Xiamen Sea.A culture-dependent survey of microbial population in the Xiamen hot springs was performed by using an approach combining total cellular protein profile identification and 16S rRNA gene sequencing.A total of 328 isolates of bacteria were obtained from liquid and sediment samples from the Xiamen hot springs,including neutrophilic thermophilic bacteria and moderately thermophilic acidophiles.Neutrophilic thermophilic bacteria,which grow at a temperature range of 55-90℃ including Rhodothermus marinus（Strain 1）,Thermus thermophilus（Strain 2）,Thermus thiopara（Strain 3）,Geobacillus stearothermophilus（Strain 4）,Geobacillus thermoleovorans（Strain 5）,and Pseudomonas pseudoalcaligenes（Strain 6）,were recovered by 2216E plates.Moderately thermophilic acidophiles,which can grow at temperatures above 50℃ and a pH range of 1.8-3.5 such as Alicyclobacillus acidoterrestris（Strain 8）,Sulfobacillus acidophilus（Strain 9）,and Sulfobacillus thermosulfidooxidans（Strain 10）,were isolated on selective solid medium containing sulfur and Fe2＋.Among these strains,Rhodothermus marinus,Thermus thermophilus and Geobacillus stearothermophilus are not only thermophiles,but also halophiles.One bacterium strain（Strain 6） shared 99% nucleotide sequence homology with Pseudomonas pseudoalcaligenes on the 16S rRNA gene sequence,but was quite different from Pseudomonas pseudoalcaligenes in biological characteristics,suggesting that it may represent a novel thermophilic species.Results indicated that various species of neutrophilic thermophiles and moderately thermophilic acidophiles were widely distributed in the Xiamen hot springs and that Rhodothermus marinus and Thermus thermophilus dominated the cultivable microbial community.

Start-up performances of dry anaerobic mesophilic and thermophilic digestions of organic solid wastes

Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide （BAA）-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.

Autoheated thermophilic aerobic sludge digestion and metal bioleaching in a two-stage reactor system

A two-stage process has been developed for stabilization of sludge and removal of heavy metals from the secondary activated sludge with high rate of energy and time conservation. The first stage of the process involves autoheated thermophilic aerobic digestion at 55-60℃ inoculated with less-acidophilic thermophilic sulfur-oxidizing microorganisms （ATAD）. The results show that it is possible to maintain the autoheated conditions （55-60℃） in the ATAD reactor up to 24 hr, leading to reduction of 21% total solids （TS）, 27% volatile solids （VS）, 27% suspended solids （SS） and 33% volatile suspended solids （VSS） from the sludge. The sludge pH also decreased from 7 to 4.6 due to the activity of less-acidophilic thermophilic microorganisms. In the second stage operation, the digested sludge （pH 4.6, TS 31.6 g/L） from stage one was subjected to bioleaching in a continuous stirred tank reactor, operated at mean hydraulic retention times （HRTs） of 12, 24 and 36 hr at 30℃. An HRT of 24 hr was found to be sufficient for removal of 70% Cu, 70% Mn, 75% Ni, and 80% Zn from the sludge. In all, 39% VSS, 76% Cu, 78.2% Mn, 79.5% Ni and 84.2% Zn were removed from the sludge in both the stages.

Bioleaching of chalcopyrite by mixed culture of moderately thermophilic microorganisms

A mixed culture of moderately thermophilic microorganisms was enriched from acid mine drainages(AMDs)samples collected from several sulphide mines in China,and the bioleaching of chalcopyrite was conducted both in shake flask and bioreactor.The results show that in the shake flask,the mixture can tolerate 50 g/L chalcopyrite after being acclimated to gradually increased concentrations of chalcopyrite.The copper extraction increases obviously in bioleaching of chalcopyrite with moderately thermophilic microorganisms supplemented with 0.4 g/L yeast extract at 180 r/min,74% copper can be extracted in the pulp of 50 g/L chalcopyrite after 20 d.Compared with copper extractions of mesophilic culture,unacclimated culture and acclimated culture without addition of yeast extract,that of accliniated culture with addition of yeast extract is increased by 53%,44% and 16%,respectively.In a completely stirred tank reactor,the mass fraction of copper and total iron extraction reach up to 81% and 56%,respectively.The results also indicate that it is necessary to add a large amount of acid to the pulp to extract copper from chalcopyrite effectively.

Relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture at 65°C

The relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleachingby mixed thermophilic Archaea culture(Acidianus brierleyi,Metallosphaera sedula,Acidianus manzaensis and Sulfolobusmetallicus)at65°C was studied.Leaching experiments showed that the addition of activated carbon could significantly promote thedissolution of chalcopyrite for both bioleaching and chemical leaching.The results of synchrotron-based X-ray diffraction,ironL-edge and sulfur K-edge X-ray absorption near edge structure spectroscopy indicated that activated carbon could change thetransition path of electrons through galvanic interactions to form more readily dissolved secondary mineral chalcocite at a low redoxpotential(?400mV)and then enhanced the copper dissolution.Jarosite accumulated immediately in the initial stage of bioleachingwith activated carbon but copper dissolution was not hindered.However,much jarosite precipitated on the surface of chalcopyrite inthe late stage of bioleaching,which might account for the decrease of copper dissolution rate.More elemental sulfur(S0)was alsodetected with additional activated carbon but the mixed thermophilic Archaea culture had a great sulfur oxidation activity,thus S0waseliminated and seemed to have no significant influence on the dissolution of chalcopyrite.

Comparison of leaching of bornite from different regions mediated by mixed moderately thermophilic bacteria

Bioleaching experiments combined with X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and scanning electron microscopy(SEM)were conducted to investigate three kinds of bornites from different regions leached by moderately thermophilic mixed bacteria of Leptospirillum ferriphilum YSK,Acidithiobacillus caldus D1 and Sulfobacillus thermosulfidooxidans ST.The results of bioleaching experiments showed that the leaching efficiency and the redox potential were significantly increased.The copper extraction efficiencies of three kinds of bornite maintained rapid growth until around the 12th day and no longer increased after the 18th,reaching 83.7%,96.5%and 86.6%,respectively.The XRD results of the leaching residue indicated that three kinds of bornites all produced jarosite in the late stage of leaching,and the leaching residues from of Daye Museum and Yunnan Geological Museum contained a mass of elemental sulfur.XPS analysis and scanning electron microscopy experiments showed that the surface of mineral particles was jarosite and the copper in the leaching residue was almost dissolved.

Removal of copper from molybdenite concentrate by mesophilic and extreme thermophilic microorganisms

Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate.Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor.The shake flask tests were performed with different inoculum size,solids density,pH.and temperature in order to identify optimum conditions.The highest amount of copper elimination,75%was obtained with extreme thermophilic microorganisms(at 12%inoculation,10%solids,65℃and a pH of 1.5).The highest copper elimination by mesophilic microorganisms was 55%(at 12%inoculation,5%solids,30℃at pH 2).The optimum conditions in shake flask tests were applied to 7 days batch tests in a50-L bioreactor.Extreme thermophilic experiment gave the best copper elimination of 60%(at 12%inoculation,10%solids,65℃and pH 1.5).Mesophilic test removed 50%of the copper(at 12%inoculation,10%solids,35℃at pH 2).

Adsorption and leaching behaviors of chalcopyrite by two extreme thermophilic archaea

The adsorption and leaching of chalcopyrite by two extreme thermophilic archaea(A.brierleyi and S.metallicus)and their mixture were studied.The results revealed that the chalcopyrite leaching rate of S.metallicus was slightly higher than that of A.brierleyi;the mixed system showed the highest rate.Community structure analysis during the leaching process showed that S.metallicus was maintained in a predominant state.However,the proportion of A.brierleyi in the community increased during leaching.Copper concentrations,which increased faster in the mixed system than in the single-organism systems during later stages,was related to the change of A.brierleyi in the community.Langmuir parameter analysis revealed no competitive adsorption between these two thermophilic archaea.Furthermore,qPCR(quantitative polymerase chain reaction)confirmed that adsorption was promoted between A.brierleyi and S.metallicus during mixed leaching.These findings can improve our understanding of the adsorption behaviors of mixed extreme microbial populations on mineral surfaces.

Isolation and Characterization of a Thermophilic Oil-Degrading Bacterial Consortium

In this study, a thermophilic oil-degrading bacterial consortium KO8-2 growing within the temperature range of 45--65℃ （with 55℃ being the optimum temperature） was isolated from oil-contaminated soil of Karamay in Xinjiang, China. Denaturing gradient gel electrophoresis （DGGE） showed that there were nine strains included in KO8-2, which originated from the genera of Bacillus, Geobacillus and Clostridium. They all belonged to thermophilic bacteria, and had been previously proved as degraders of at least one petroleum fraction. The crude oil degraded by KO8-2 was analyzed by infrared spectrophotometry, hydrocarbon group type analysis and gas chromatography. The results indicated that the bacterial consortium KO8-2 was able to utilize 64.33% of saturates, 27.06% of aromatics, 13.24% of resins and the oil removal efficiency reached up to 58.73% at 55 ~C when the oil concentration was 10 g/L. Detailed analysis showed that KO8-2 was able to utilize the hydrocarbon components before C19, and the n-alkanes ranging from C20--C33 were signifi- cantly degraded. The ratios of nC17/Pr and nC18/Ph were 3.12 and 3.87, respectively, before degradation, whereas after degradation the ratios reduced to 0.21 and 0.38, respectively. Compared with the control sample, the oil removal efficiency in KO8-2 composting reactor reached 50.12% after a degradation duration of 60 days.

Preservation of moderately thermophilic culture by freeze drying and frozen preservation way and effect on subsequent bioleaching of chalcopyrite

Freeze drying and frozen preservation way was used to preserve a moderately thermophilic culture for bioleaching of chalcopyrite concentrate.After preservation of 15 months,the cell viability rate decreases to 22% with a cell density of 7×107 mL-1.When the growth time was extended from 8 days to 14 days,cell density would increase in a large scale to about 3×108 mL-1.In the bioleaching experiments,unpreserved and preserved cultures were compared for dissolving chalcopyrite concentrate.Before 44 days,the unpreserved culture can reach a high copper extraction of about 17.4 g/L.While the preserved culture shows a rather low copper extraction,which is only 9.7 g/L.When the bioleaching time was extended to 80 days,copper extraction by preserved culture increases remarkably,and the concentration of copper finally achieves up to 18.3 g/L.On the other hand,copper extraction by the unpreserved culture does not show remarkable increase from 44th to the 80th day,and finally the total copper extraction is 19.8 g/L.As a result,total copper extraction in 80 days by preserved culture approaches that by unpreserved culture and freeze drying and frozen preservation even after 15 months does not bring much decrease of bioleaching ability.

Biodegradation Kinetics for Pre-treatment of Klebsiella pneumoniae Waste with Autothermal Thermophilic Aerobic Digestion

Biodegradation parameters and kinetic characteristics for pre-treating waste strains of Klebsiella pneu-moniae were studied in laboratory scale with an insulated reactor by an innovative technique,autothermal thermo-philic aerobic digestion(ATAD) . Based on an Arrhenius-type equation,an empirical model was developed to corre-late the removal of total suspended solid(TSS) with the initial TSS concentration,influent reaction temperature,aeration rate and stirring rate. The reaction temperatures of the ATAD system could be raised from the ambient temperatures of 25 °C to a maximum temperature of 65 °C. The exponentials for the initial TSS concentration,aeration rate and stirring rate were 1.579,-0.8175 and-0.6549,respectively,and the apparent activation energy was 6.8774 kJ·mol-1. The correlation coefficient for the pre-exponential factor was 0.9223. The TSS removal effi-ciency predicted by the model was validated with an actual test,showing a maximum relative deviation of 10.79%. The new model has a good practicability.

Effect of mixed moderately thermophilic adaptation on leachability and mechanism of high arsenic gold concentrate in an airlift bioreactor

A refractory gold concentrate with 19% arsenic was treated by a mixed moderately thermophiles in an airlift bioreactor through an adaptation protocol. The moderately thermophiles could respond well to 20%(w/v) pulp density with less than 10% loss of productivity, and resist arsenic up to 15 g/L. There were a lot of jarosite, arsenolite and sulfur, but not scorodite and ferric arsenate in the bioleached residue. Jarosite passivation and lower sulfur-oxidizing activity of the cells due to the toxicity of the high concentrations of soluble arsenic and iron ions at low p H value should mainly response for the incomplete extraction at high pulp density. The initial bacterial community did not change in nature except for new found P aeruginosa ANSC, but sulfur-oxidizing microorganisms have been dominant microorganisms after a long time of adaptation. Pseudomonas aeruginosa originating from the gold concentrate should be closely relative to the metabolism of the organic matters contained in the refractory gold concentrate.

Influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste

A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasing temperature suddenly from 55 ℃ to 20 ℃ suddenly, 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/（L·d） and 15 d respectively for MOSW load and retention time, following results were noted： （1） biogas production almost stopped and VFA （volatile fatty acid） accumulated rapidly, accompanied by pH decrease; （2） with low temperature （20 ℃） duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation, （3） the longer the low temperature interval lasted, the more the methanogenic bacteria would decay, hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation： （4） the thermophilic microorganisms were highly resilient to temperature fluctuation.

Comparison of ASBR and CSTR reactor for hydrogen production from palm oil mill effluent under thermophilic condition

Hydrogen production from palm oil mill effluent (POME) by Thermoanaerobacterium thermosaccharolyticum PSU-2 was investigated both in batch and continuous reactors using anaerobic sequencing batch reactor (ASBR) and continuous stirred tank reactor (CSTR). The hydrogen production determined from batch experiment of POME at an inoculum size of 0%, 10%, 20% and 30% (v/v) was 161, 201, 246 and 296 mL H2/g-COD with COD removal efficiency of 21%, 23%, 23% and 23%, respectively. Continuous hydrogen production was start-up with 30% (v/v) inoculum in both ASBR and CSTR reactors and more than 30% COD removal could be obtained at HRT of 4 days, corresponding to OLR of 11.3 g COD/ L·day. Similar hydrogen production rates of 2.05 and2.16 LH2/L. day were obtained from ASBR and CSTR, respectively. COD removal efficiency of ASBR was 37.7%, while it was 44.8% for CSTR. However, ASBR was stable in term of alkalinity, while the CSTR was stable in term of hydrogen production, soluble metabolites concentration and alkalinity. Therefore, the CSTR was found to be more stable in hydrogen production than ASBR under the same OLR.