•A concept of AnMBR-PN/A process was proposed for mainstream treatment.•In-situ FA/FNA exposure eliminated Nitrospira while retained Nitosonomas community.••DO limitation prevented switch of the NOB ...community in the mainstream conditions.•The effluent TN of the mainstream PN/A system was lower than 10 mg-N/L.•Enhanced hydrodynamic shear force resulted in sludge settleability deterioration.
In this pilot-scale study, an innovative mainstream treatment process that couples the anaerobic membrane reactor (AnMBR) with a one-stage PN/A system was proposed for advancing the concept of carbon neutrality in the municipal wastewater treatment plant. This work demonstrates the start-up procedure of a pilot-scale one-stage PN/A system for mainstream treatment. The 255-day start-up of the one-stage PN/A system involved the cultivation of ammonium-oxidizing bacteria (AOB) from the activated sludge, suppression of nitrite-oxidizing bacteria (NOB), investigation of in-situ growth kinetics of anammox bacteria (AnAOB), and the 50-day operation of the pilot-scale AnMBR-PN/A process for natural mainstream treatment. It is verified in the pilot-scale system for the first time that the in-situ free ammonia (FA) and free nitrous acid (FNA) exposure could effectively eliminate the Nitrospira (the NOB genus) while retaining the Nitosonomas (the AOB genus) community in the suspended sludge. NOB community rebounding was not detected even at the mainstream conditions with low nitrogen concentrations (Influent ammonium concentration=38±6 mg-NH4+-N/L) by intermittent aeration to control the system dissolved oxygen (DO) below 0.5 mg/L. The results of the mainstream treatment showed that the average effluent total nitrogen (TN) in the coupled process was generally lower than 10 mg-N/L, which meets the discharge limits of most prefectures in Japan. The investigated results of the in-situ anammox bacteria (AnAOB) growth kinetics suggested that the promoted start-up strategy of taking advantage of the warm months with higher mainstream temperature to achieve the rapid in-situ growth of the AnAOB is applicable in the investigated regions. From the perspective of the removal performance of the TN and organic substance, the AnMBR-PN/A process has great potential as the layouts of the carbon-neutral mainstream wastewater treatment plants.
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2D transition metal dichalcogenides materials are explored as potential surface‐enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T ...(1T′) rhenium disulfide (ReS2) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al2O3 dielectric layer unambiguously reveal that Raman enhancement on ReS2 materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS2 nanosheets. On monolayer ReS2 film, a strong resonance‐enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10−9m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer‐number‐dependent feature and excitation‐energy‐related resonance effect, ReS2 is a promising Raman enhancement platform for sensing applications.
Here the Raman enhancement mechanism on distorted 1T ReS2 nanosheets is demonstrated, where combined Raman and photoluminescence studies with the introduction of an Al2O3 dielectric layer unambiguously reveal that Raman enhancement on ReS2 materials is from a charge transfer process rather than from an energy transfer process.
Mixed‐dimensional (0D, 1D, and 3D) heterostructures based on 2D layered materials have been proven as a promising candidate for future nanoelectronics and optoelectronics applications. In this work, ...it is demonstrated that 1D atomic chain based Se nanoplates (NPs) can be epitaxially grown on monolayer ReS2 by a chemical transport reaction, thereby creating an interesting mixed‐dimensional Se/ReS2 heterostructure. A unique epitaxial relationship is observed with the (110) planes of the Se NPs parallel to the corresponding ReS2 (010) planes. Experimental and theoretical studies reveal that the Se NPs could conjugate with underlying monolayer ReS2 via strong chemical hybridization at heterointerface, which is expected to originate from the intrinsic defects of ReS2. Remarkably, photodetectors based on Se/ReS2 heterostructures exhibit ultrahigh detectivity of up to 8 × 1012 Jones, and also show a fast response time of less than 10 ms. These results illustrate the great advantage of directly integrated 1D Se based nanostructure on planar semiconducting ReS2 films for optoelectronic applications. It opens up a feasible way to obtain mixed‐dimensional heterostructures with atomic interfacial contact by epitaxial growth.
1D atomic chain based Se nanoplates (NPs) are epitaxially grown on monolayer ReS2 to form an interesting mixed‐dimensional Se/ReS2 heterostructure. Experimental and theoretical studies reveal that the Se NPs are chemically hybridized with underlying monolayer ReS2 through intrinsic defects in ReS2. Photodetectors based on Se/ReS2 heterostructures exhibit ultrahigh detectivity and fast response time.
•A single-stage and two two-stage anaerobic systems were synchronously operated.•Similar methane production 0.44L/g VSadded from oily food waste was achieved.•The first stage of the two-stage process ...became inefficient due to serious pH drop.•Recycle favored the hythan production in the two-stage digestion.•The conversion of unsaturated fatty acids was enhanced by recycle introduction.
Anaerobic digestion is an effective technology to recover energy from oily food waste. A single-stage system and temperature-phased two-stage systems with and without recycle for anaerobic digestion of oily food waste were constructed to compare the operation performances. The synchronous operation indicated the similar ability to produce methane in the three systems, with a methane yield of 0.44L/g VSadded. The pH drop to less than 4.0 in the first stage of two-stage system without recycle resulted in poor hydrolysis, and methane or hydrogen was not produced in this stage. Alkalinity supplement from the second stage of two-stage system with recycle improved pH in the first stage to 5.4. Consequently, 35.3% of the particulate COD in the influent was reduced in the first stage of two-stage system with recycle according to a COD mass balance, and hydrogen was produced with a percentage of 31.7%, accordingly. Similar solids and organic matter were removed in the single-stage system and two-stage system without recycle. More lipid degradation and the conversion of long-chain fatty acids were achieved in the single-stage system. Recycling was proved to be effective in promoting the conversion of unsaturated long-chain fatty acids into saturated fatty acids in the two-stage system.
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•Two UASB processes were investigated by continuously feeding with starch wastewater.•The predominant methanogenic pathways in the two processes were different.•Different surface ...attachments were observed on the granules in the two processes.•The microbial function of the one-stage UASB shifted to hydrogen fermentation.
Poor processing stability has been cited as the fatal shortcoming of the up-flow anaerobic sludge blanket (UASB) reactor treating starch wastewater (SW). In this study, the SW treatment performance in a one-stage UASB reactor and a pre-acidification equipped UASB process were evaluated together with the microbial dynamics. The results revealed that the pre-acidification provided improvements in terms of the substrate utilization diversity and the stability of the microbial community structure on the UASB reactor. Anaerolineaceae/Methanosaeta was the core functional microbiota in the pre-acidification equipped UASB reactor, indicated the superior abilities on the acetogenic methanogenesis of granules. The genus of Methanobacterium, a hydrogenotrophic methanogen was dominant in the archaeal community in the one-stage UASB reactor. The granules performed very strong hydrogen affinity in methane production, a small amount of propionate was detected in the effluent. These were abnormal, which suggested the high hydrogen turn-over rate in the one-stage UASB reactor.
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•Biochar packed reactor improved the CH4 yield and stability of tar degradation.•Biochar alleviated the inhibition of tar solution to anaerobic digestion.•Biochar prolonged the ...retention time of most organic matters in tar solution.•Packed biochar promoted the syntrophic growth of different microbes.
Tar generated as a by-product during biomass gasification contains a high concentration of refractory organic matters. In this study, a hybrid upflow anaerobic sludge-biochar bed reactor was established for tar treatment, and the methane yield was 120–154 NmL-CH4/g-CODinf, 20–30% higher than the control reactor. COD removal and methane production significantly decreased in both reactors when the influent tar concentration was doubled from 4954 mg-COD/L to 9964 mg-COD/L. When the influent concentration was reduced, the biochar packed reactor showed a faster recovery. Batch tests confirmed that higher tar concentration inhibited methane production and induced longer lagphase. Biochar addition effectively relieved the inhibition and prolonged the retention of organic matters. SEM observation and 16S rRNA analysis suggested that biochar also acted as the microbe’s carrier, and promoted the growth of some microbes. The results of this study provide new ideas for tar treatment.
In this study, a newly established bench-scale thermophilic continuously stirred fluidized bed reactor (CSFBR) was applied for anaerobic co-digestion of food waste (FW) with grease trap waste (GTW). ...The performance of CSFBR regarding stability and treatment efficiency was inspected through a laboratory contrast experiment with two traditional continuous stirred tank reactors (CSTRs). In the OLR range of 3.19–7.41 g COD/L/d, the methane production rate of the thermophilic CSFBR was about as high as that of the thermophilic CSTR. Nevertheless, the thermophilic CSFBR had much lower VFAs (<1000 mg/L) and LCFA concentrations (<100 mg/L) as compared with the thermophilic CSTR. Unlike the mesophilic CSTR, there was no foaming that occurred in the CSFBR during the whole experimental period. The results all suggested that CSFBR simultaneously provided high treatment capacity and process stability in anaerobic digestion with high-lipid loading.
•Grease trap waste (GTW) addition was employed to co-digest with food waste (FW).•The lipid loading lower than 1.61 g/(L·d) did not result in digester failure.•GTW addition could increase methane ...yield up to 68% compared to mono-digestion.•Palmitic acid dominated the residual long chain fatty acids, accounting for 73.7%.•The acetoclastic methanogenic activity was promoted by increased GTW addition.
In order to boost the economics of biogas utilization in those small facilities for food waste (FW) digestion, proximate grease trap waste (GTW) was employed to co-digest with FW. A bench-scale continuous stirred tank reactor was set up and operated at mesophilic temperature to investigate the co-digestion limit and lipid/long chain fatty acid (LCFA) conversion by increasing lipid loading stepwise. Mixing FW and GTW at lipid/total solids (TS) 55%, where the lipid loading was 1.61 g/(L·d), was proved to be appropriate, and the maximum methane yield reached 68% higher than the mono-digestion of FW, with a similar lipid reduction at approximately 90%. In addition, since acetic acid accumulation above 100 mg HAc/L had been observed under the optimal loading, the threshold value for anaerobic co-digestion of FW and GTW was confined to the lipid loading around 1.61 g/(L·d). The rapid recovery strategy of mixing the inhibited sludge with fresh inoculum at 1:4 (V/V) took effect after process failure resulted from further increasing lipid/TS to 70%. Lipid/LCFA concentrations in the effluent rose with the increased lipid loading, while palmitic acid accounted for the most percentage among the residual LCFAs, as high as 73.7% at lipid/TS 55%. Acetoclastic methanogens played an important role in accelerating process conversion, due to the fact that raising GTW addition led to the increased methanogenic activity, with a value of 26.9 mL-CH4/(g-VS·d) at the optimal loading.
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•Anaerobic biofilm formation was evaluated using a crystal sensor.•Ca addition (8–16 mM) accelerated biomass adhesion on the sensor surface.•The presence of Na can offset the positive ...effect of Ca in biofilm formation.•The negative effect appeared at lower Na levels than those were previously observed.•Cationic polymer can successfully accelerate biofilm formation at high salinity.
This study investigated early stages of biofilm formation from sieved fine particles of anaerobic granules in the presence of various cationic substances using a quartz crystal sensor to improve biofilm formation in the anaerobic treatment of saline wastewater. The biomass attached on the sensor was greatly increased with Ca within the low range (8–16 mM), which was not affected by 50 mM of Na. However, the positive effect of 16 mM of Ca was strongly reduced in the co-presence of Ca and Na when Na concentrations were in the range from 25 to 150 mM because Ca may compete with Na for the limited binding sites in biofilm. The addition of cationic polymer at 150 mM of Na increased biomass adhesion by several folds at only 10–80 mg/L compared to the addition of 16 mM of Ca. Moreover, no methanogenic inhibition was presented below the polymer content of 20 mg/L.
Significant variations in leaf colours, pigment contents, and main taste compounds in young shoots from albino tea plants (Camellia sinensis) influence tea flavour. However, the seasonal metabolic ...pattern and molecular regulatory mechanism of these metabolites remain largely elusive. Herein, we conducted morphological, biochemical, metabolomic and transcriptomic analyses between an albino tea cultivar ‘Zhonghuang 3’ (‘ZH3’) and a green strain ‘Tai cha 15’ (‘TC15’) at four‐time points (April 12, May 31, July 14, and August 17) to elucidate dynamic changes in these compounds and predict the relationships among transcription factors (TFs), target genes (TGs), and metabolite abundance. Generally, leaf colours and pigment contents were significantly lighter and lower, respectively, in ‘ZH3’ than in ‘TC15’ from spring to summer, but were subsequently similar. Compared to ‘TC15’, ‘ZH3’ had a lower and broader phenol/ammonia ratio as well as stable caffeine content and showed more significantly different metabolites and differentially expressed genes. The relationship between pigments, main taste compounds, and their biosynthetic genes, as well as TFs and their TGs, had genetic specificity. These results suggested that the biosynthesis of these compounds was probably both season‐ and variety‐dependent. In total, 12 models of the TF‐TG‐metabolite regulatory network were proposed to uncover the biosynthetic and regulatory mechanisms of these metabolites in tea plants. A high correlation was observed between some structural genes and TFs with the accumulation of these metabolites. These findings provide novel insights into the regulatory mechanisms underlying accumulation of pigments and main taste compounds in tea plants.