Macromolecular Organic Matter Research Articles

Raman spectroscopy of Ryugu particles and their extracted residues: Fluorescence background characteristics and similarities to CI chondrites

AbstractWe present here an investigation of Ryugu particles recovered by the Hayabusa2 space mission and their extracted carbonaceous acid residues using Raman spectroscopy. Raman parameters of Ryugu intact grains and their acid residues are characterized by broad D (defect induced) and G (graphite) band widths, indicating the presence of polyaromatic carbonaceous matter with low thermal maturity. Raman spectra of Ryugu particles and CI (type 1) chondrites exhibit stronger laser‐induced fluorescence backgrounds compared to Type 2 and Type 3 carbonaceous chondrites. The high fluorescence signatures and wide bandwidths of the D and G bands of Ryugu intact grains are similar to the Raman spectra observed in CI chondrites, reflecting the low structural order of their aromatic carbonaceous matter, and strengthening the link between Ryugu particles and CI chondrites. The high fluorescence background intensity of the Ryugu particles is due to multiple causes, but it is likely that the relative abundance of geometry‐bearing macromolecular organic matter in total organic carbon contents makes a large contribution to the fluorescence intensities. Locally observed high fluorescence in the acid‐extracted residues of Ryugu is due to nitrogen‐bearing outlier phase. The high fluorescence signature is one consequence of the low degree of thermal maturity of the organic matter and supports evidence that the Ryugu particles have escaped significant parent body thermal metamorphism.

High performance of carbon nanotube-encapsulated CuFe2O4 for peroxonosulfate activation: A process of degradation of sulfamethoxazole in complex matrix water via a singlet oxygen-dominated pathway

The common advanced oxidation process has problems such as short free radical life, low utilization rate, and weak catalyst stability. In this study, CuFe2O4 spinel was encapsulated in carbon nanotubes (CNT) to activate peroxymonosulfate (PMS), and a catalyst CuFe2O4-in-CNT with a closed structure was synthesized. The catalyst exhibits exceptional catalytic performance in the degradation of sulfamethoxazole, effectively degrading 96.10% of sulfamethoxazole (SMX) within a mere 10 min. At the same time, carbon nanotubes provide a relatively ideal nano-enclosed space for the filling of CuFe2O4 nanoparticles. The confinement effect in CuFe2O4-in-CNT/PMS system is reflected in the following three aspects: (i) The catalyst with a closed structure can effectively alleviate the influence of macromolecular organic matter on the catalytic system; (ii) The reactive species (O2•-, SO4•-, HO•) accelerated recombination in a confined reaction space and rapidly converted to 1O2 as the major active substance; (iii) Strengthen the way of electron transfer. The interaction of catalysts, oxidants and pollutants is enhanced in a nano-enclosed environment by CuFe2O4-in-CNT/PMS process. In addition, CuFe2O4 nanoparticles were filled in the CNT cavity, which further affected the catalytic performance and stability. The removal rate of SMX by CuFe2O4-in-CNT was 90% after five cycles.

Enhanced dewaterability and triclosan removal of waste activated sludge with iron-rich mineral-activated peroxymonosulfate

High water and pharmaceutical and care products (PPCPs) bounded in sludge flocs limit its utilization and disposal. The advanced oxidation process of perxymonosulfate (PMS) catalyzed by iron salts has been widely used in sludge conditioning. In this study, two iron-rich minerals pyrite and siderite were proposed to enhance sludge dewatering performance and remove the target contaminant of triclosan (TCS). The permanent release of Fe2+ in the activation of PMS made siderite more effective in enhancing sludge dewater with capillary suction time (CST) diminishing by 60.5 %, specific resistance to filtration (SRF) decreasing by 79.2 %, and bound water content (BWC) dropping from 37.1 % to 2.6 % at siderite/PMS dosages of 0.36/0.20 mmol/g-TSS after 20 min of pretreatment. Pyrite/PMS performed slightly inferior under the same conditions and the corresponding CST and SRF decreased by 51.5 % and 71.8 % while the BWC only declined to 17.8 %. Rheological characterization was employed to elucidate the changes in sludge dewatering performance, with siderite/PMS treated sludge showing a 48.3 % reduction in thixotropy, higher than 28.4 % of pyrite/PMS. Oscillation and creep tests further demonstrated the significantly weakened viscoelastic behavior of the sludge by siderite/PMS pretreatment. For TCS mineralization removal, siderite/PMS achieved a high removal efficiency of 43.9 %, in comparison with 39.9 % for pyrite/PMS. The reduction in the sludge solids phase contributed the most to the TCS removal. Free radical quenching assays and EPR spectroscopy showed that both siderite/PMS and pyrite/PMS produced SO4-· and ·OH, with the latter acting as the major radicals. Besides, the dosage of free radicals generated from siderite/PMS exhibited a lower time-dependence, which also allowed it to outperform in destroying EPS matrix, neutralizing the negative Zeta potential of sludge flocs, and mineralizing macromolecular organic matter.

The simultaneous removal of methylene blue (MB) and Ca2+ by recyclable adsorbents based the scales derived from coal gasification system.

The transformation of solid wastes from industrial production into effective adsorbents could significantly contribute to wastewater treatment. In this study, after acidizing and burning soft scale (SS) from coal gasification system, two magnetic adsorbents (mag-ASS and mag-BASS) were prepared via the combination of magnetite with ultrasonic, respectively. The treatment effects of mag-ASS and mag-BASS were then investigated for simulated wastewater containing macromolecular organic matter [i.e., methylene blue (MB)] and Ca2+. The results indicated that the pseudosecondorder kinetic, Elovich, Freundlich,Langmuir and Temkin model could well describe the adsorption behavior of MB and Ca2+ onto mag-ASS and mag-BASS. The maximum adsorption capacities of mag-ASS for MB and mag-BASS for Ca2+ were 600.53mg/g and 102.54mg/g, respectively. Surprisingly, the adsorption abilities of mag-ASS for MB and mag-BASS for Ca2+ showsignificantly higher than the others. The adsorption mechanisms of MB mainly included electrostatic interaction, π-π conjugate interaction and cation exchange, while those of Ca2+ were mainly electrostatic interaction and cation exchange. The diffusion of MB and Ca2+ onto the magnetic adsorbents might be controlled by the combined effects of intraparticle and liquid film diffusion. There was no significant reduction in adsorption capacity after 8 cycles of adsorptionand desorption, indicating that SS-based magnetic adsorbents had good recyclability and stability. Moreover, the removal efficiency of mag-BASS for total hardness and total organic carbon in real coal gasification gray water (CGGW) was 82.60 and 64.10%, respectively. The treatment of CGGW and theresource of wastes would significantly promote the reasonable disposal of coal gasification scales.

Presence of iron oxide particles can reduce the cake fouling in UF systems

Ultrafiltration (UF) has been widely used in drinking water treatment. However, the deposition of iron oxide particles on the membrane surface facilitates the formation of cake layers, which limits the application of UF in iron-bearing water treatment. To understand the impact of iron oxides on the membrane fouling of UF, the effects of iron oxide particles on the bio-regulated cake layer and conventional cake layer formed at the flux of 5 and 20 L·m−2·h−1 were investigated, and compared with SiO2 particles. Unlike the SiO2 paticles which tends to increase the cake fouling resistance, iron oxide paticles could significantly reduce the cake fouling resistance. The iron oxide-UF could reduce specific resistance by 65 %～75 % in bio-regulated cake layer and 40%～50% in conventional cake layer. OCT observations revealed that in the presence of iron oxide, the thickness of the conventional cake layer increased significantly, while the thickness of the bio-regulated cake layer remains unchanged. Therefore, the increased resistance was primarily attributed to the formation of a porous cake layer, which could be evidenced by SEM images. Besides, in the presence of iron oxide, the content of polysaccharides and proteins in the cake layer decreased. Particularly, for the bio-regulated cake layer, the content of polysaccharides and proteins decreased by 80.0% and 59.9%, respectively. This may be attributed to the capability of iron oxide to mitigate microbial-induced fouling and selectively adsorb macromolecular organic matters. Consequently, iron oxide exhibits distinct properties compared to traditional particles in mitigating cake fouling. Retaining some iron oxide before UF could facilitate the mitigation of membrane fouling in iron-bearing water treatment

Aeration pre-treatment role in improving the performance of bio-conditioning dewatering of food waste anaerobic digestate

Bio-conditioning dewatering followed by activated sludge process (BDAS) is a promising technology for purifying food waste anaerobic digestate (FWAD). However, the bio-conditioning dewatering efficiency is often affected by FWAD properties and ambient temperature. Here, we firstly reported that aeration pre-treatment of FWAD played an important role in improving the bio-conditioning dewatering performance of FWAD. The study found that the accumulated carbonate (CO32–) in FWAD severely affected the flocculation of Fe-containing flocculant formed in microbial fermentation liquor due to the competitive consumption of the flocculant by CO32–. The capillary suction time (CST) and specific resistance to filtration (SRF) of the bio-conditioned FWAD increased from initial 77.8 s and 2.0 × 1012 m/kg to 122.7 s and 3.4 × 1012 m/kg, respectively, within 1 day of aeration. Prolonged aeration pre-treatment of FWAD could reduce its CO32– concentration and total alkalinity. Additionally, the aeration pre-treatment simultaneously decreased the proportion of macromolecular organic matter that hindered dewatering and the content of total solids (TS) and hydrophilic protein-like substances in FWAD. After 20 days of aeration followed by bio-conditioning, the CST and SRF reduced to final 36.5 s and 2.3 × 1011 m/kg, respectively, indicating a substantial improvement in dewatering performance. Successive forced aeration combined with the addition of CaCl2 to eliminate adverse factors mainly CO32– was a feasible and cost-effective strategy to realize bio-conditioning dewatering of FWAD in less than 2 days and a lower reagents dose of bio-conditioning, which was helpful in the engineering application of the novel BDAS process for FWAD purification.

Research progress and perspectives of biogas production from municipal organic solid waste

Abstract Anaerobic digestion is a prevailing technology for the treatment and utilization of municipal organic solid waste (MOSW). In this technology, the macromolecular organic matter in waste degrades into small molecular substances through the anaerobic decomposition of microorganisms, producing biogas that can provide enormous energy. This paper focuses on the research progress of anaerobic digestion of various organic wastes for biogas production. The principle and process of anaerobic digestion for biogas production are introduced, along with the key factors affecting anaerobic digestion efficiency, such as temperature, pH, and sealing conditions. At the same time, the current cycle treatment technology and comprehensive treatment system of MOSW are also summarized. Furthermore, the paper explores biogas purification technologies, including desulfurization, deoxidation, drying, and decarbonization. Finally, the state-of-the-art of the utilization of MOSW for biogas production in the world and the problems faced by the utilization of MOSW for biogas production in China are reviewed. By summarizing the anaerobic digestion technology of MOSW, this review hopes to provide some reasonable solutions for the high-value utilization of MOSW.

Characterization of Sulfur-Rich Microbial Organic Matter in Jurassic Carbonates Using Laser-Assisted Mass Spectrometry.

Laser desorption-ionization mass spectrometry (MS) shows great potential for in situ molecular analysis of planetary surfaces and microanalysis of space-returned samples or (micro)fossils. Coupled with pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) in ESA's ExoMars project, this technique could help assess further the origin of sulfur-bearing organic matter (OM) recently detected on Mars. To unravel this potential, we analyzed sulfurized microbial OM from ca. 150 million year-old carbonates with laser desorption-ionization mass spectrometry (single- and two-step: LDI-MS and L2MS), in comparison with time-of-flight secondary-ion mass spectrometry (ToF-SIMS), gas chromatography-mass spectrometry (GC-MS), and Py-GC-MS. We show that LDI-MS and L2MS readily detect sulfur-bearing moieties such as (alkyl)thiophenes and (alkyl)benzothiophenes. The mineral matrix, however, made the identification of sulfur-bearing molecules challenging in our L2MS experiment. The dominance of small aromatic hydrocarbons (≤14 carbons) in the LDI-MS and L2MS of the extracted soluble and insoluble OM and of the bulk rock is consistent with the low thermal maturity of the sediment and contrasts with the predominance of larger polycyclic aromatic structures commonly observed in meteorites with these techniques. We detected inorganic ions, in particular VO+, in demineralized OM that likely originate from geoporphyrins, which derive from chlorophylls during sediment diagenesis. Finally, insoluble OM yielded distinct compositions compared with extracted soluble OM, with a greater abundance of ions of mass-to-charge ratio (m/z) over 175 and additional N-moieties. This highlights the potential of laser-assisted MS to decipher the composition of macromolecular OM, in particular to investigate the preservation of biomacromolecules in microfossils. Studies comparing diverse biogenic and abiogenic OM are needed to further assess the use of this technique to search for biosignatures.

Enhanced biological phosphorus removal from wastewater and dynamics of microbial population in dual PAOs symbiosis system

Low level of volatile fatty acids (VFAs) is a key factor limiting the performance of enhanced biological phosphorus removal (EBPR) by traditional polyphosphate accumulating organisms (PAOs). A newly discovered PAOs capable of fermenting macromolecular organic matter into short-chain VFAs could solve the problem. However, the roles of traditional and fermented PAOs in wastewater treatment processes and the collaboration between functional microorganisms remain unknown. In this study, a sequencing batch reactor (SBR) was operated with alternating anaerobic oxic (An/O) mode to investigate the effect of mixed carbon source ratios, namely, acetate (NaAc):casein hydrolysate (Cas aa) = 4:0, 3:1, 1:1, 1:3 and 0:4, on EBPR performance and microbial community structure. The results showed that the phosphorus removal efficiency remained stable as NaAc was the sole carbon source. When NaAc:Cas aa varied from 3:1 to 1:3, the recovery of system performance took less time compared to the last Run, implying an adaptation of PAOs to Cas aa. Moreover, the anaerobic phosphorus release time was found to increase with the increasing amount of VFAs from Cas aa degradation, indicating the enrichment of fermented bacteria and the utilization of VFAs by traditional PAOs. Increasing the dose of Cas aa also generated more NH4+-N, owing to the reaction of the groups in the amino acids with water, causing a drastic decrease of ammonium removal efficiency from 88.9 % to 15.2 %. The ideal process performance implied that EBPR by dual PAOs synergistic symbiosis occurred in the system with NaAc:Cas aa = 1:1. Meanwhile, the results of 16S ribosomal RNA (16S rRNA) genes-Illumina MiSeq high-throughput sequencing showed that the abundance of traditional PAOs decreased from 22.4 % (4:0) to 11.6 % (1:1) and to 4.9 % (0:4), but fermented PAOs increased from 9.9 % to 19.5 %, then decreased to 17.3 %. Dual PAOs synergistic symbiosis could be of great potential for EBPR in treating low VFAs wastewater.

Treatment of landfill leachate nanofiltration concentrate by a three-dimensional electrochemical technology with waste aluminum scraps as particle electrodes: Efficacy, mechanisms, and enhancement effect of subsequent electrocoagulation

Landfill leachate nanofiltration concentrate is a kind of wastewater containing high concentrations of color and refractory organics. Herein, we proposed a novel three-dimensional electrochemical technology (3DET) with waste aluminum scraps as particle electrodes for its treatment. The planar and particle electrodes were first optimized. Ti/RuO2 and graphite were used as anodes in the two-dimensional electrochemical technology (2DET). In the light of contaminant removal (color, UV254, COD, and TOC), chlorine reduction, and energy consumption, graphite was selected as planar anodes and cathodes. Moreover, 3DET with Al particle electrodes (Al 3DET) outperformed that with conventional granular activated carbon electrodes, 2DET, and Al particles. At 120 min, the removal efficiencies of color, UV254, COD, and TOC using Al 3DET were 98.94 %, 84.72 %, 51.93 %, and 67.46 %, respectively. UV–vis and EEM spectroscopy, and GC–MS analyses indicate that macromolecular organic matter such as humic-like substances could be effectively degraded and simultaneously removed. Reactive species identification tests including free radical quenching and EPR spectra were conducted. The results indicate that in addition to anodic direct oxidation, indirect oxidation by oxidative species (H2O2, •OH, and RCS) and flocculation by Al species also played a vital role in contaminant removal. Continuous-flow experiments show that Fe EC as a post-treatment step of Al 3DET could effectively provide a neutralization effect for the 3DET effluent and enhance the removal efficiency of contaminants. The total operating cost of combined process was 1.307 USD/m3. This study shows that the Al 3DET-Fe EC process is a promising technology for the treatment of nanofiltration concentrate.

Abundant extraterrestrial purine nucleobases in the Murchison meteorite: Implications for a unified mechanism for purine synthesis in carbonaceous chondrite parent bodies

Extraterrestrial nucleobases are of key interest owing to their implications for the chemical evolution of primordial molecules in the solar system and their potential contributions to prebiotic chemistry on the early Earth. Recent advances in analytical techniques capable of detecting femto-mole-order nucleobases have allowed us to identify all five exogenous nucleobases—uracil, cytosine, thymine, adenine, and guanine—in carbonaceous chondrites and to quantify uracil obtained from the carbonaceous asteroid (162173) Ryugu. In this study, we optimized the analytical method using hot-water extraction followed by 6 M hydrochloric acid (HCl) extraction from a sample of the CM2 Murchison meteorite to reassess the abundances and distributions of extraterrestrial nucleobases. The target analyses performed using high-performance liquid chromatography paired with electrospray-ionization, high-resolution mass spectrometry revealed that purine nucleobases were substantially more enriched in the subsequent 6 M HCl extract (951 ± 104 parts per billion, ppb) than in the hot-water extract (199 ± 3 ppb). The most abundant nucleobase was guanine (649 ± 103 ppb in total). The 6 M HCl extract not only contained canonical nucleobases but also included rare nucleobase analogs from the purine family, such as 8-substituted purines. Unlike purines, we preferentially detected pyrimidine nucleobases in the hot-water extract and the acid hydrolysate (185 ± 17 ppb and 297 ± 5 ppb, respectively) rather than in the 6 M HCl extract (51 ± 4 ppb). The disparate distributions of purine and pyrimidine bases in the Murchison meteorite suggests that purines are more robustly incorporated than pyrimidines into meteoritic matrices and/or insoluble macromolecular organic matter. We propose a unified formation mechanism for purine nucleobases—which involves the synthesis of 5-aminoimidazole derivatives from hydrogen cyanide and its related molecules—that can account for the molecular distributions of the extraterrestrial purine nucleobases found in the Murchison meteorite.

Simultaneous removal of phosphorus and organic matter in municipal tail water enhanced by Fe2+/S2O82- system: Parameter optimization, efficiency, mechanism

The simultaneous removal of phosphorus (TP) and organic matter is a very ingenious process and has attracted much attention. A Fe2+/S2O82- system was constructed to advanced treat TP and organic matter in sewage. The influencing factors and degradation mechanism were investigated. The results showed that the parameters of Fe2+/P and S2O82-/Fe2+ were optimized to be 5 and 4, respectively. The molar ratio of S2O82-/Fe2+ was 4, the removal performance of TP and target oriented curriculum (TOC) was the best, and the increase of temperature was beneficial to the removal of TP and TOC. The precipitate in the secondary effluent was mainly ferric phosphate. The TP removal mechanism lied in the removal by the formation of Fe4(PO4)3(OH)3 precipitation. And protein macromolecular organic matter is degraded into small molecular organic matter such as methane (CH4) for subsequent use as a high-quality carbon source.

Phase behavior and GOR evolution using a natural maturity series of lacustrine oil-prone shale: Implications from compositional modelling

For the exploration of shale oil, there is still an urgent need to relate hydrocarbon generation reactions and changing phase behavior to exact levels of thermal maturity. Six organic-rich shale samples from the Cretaceous Qingshankou Formation, Songliao Basin spanning the maturity range with vitrinite reflectance (Ro) 0.58%–1.16% were studied for petroleum generation characteristics using the PhaseKinetics, PhaseSnapshot, and GORFit approaches. All samples show very good petroleum potential and contain Type I kerogen with total organic carbon contents ranging between 1.5% and 5%. A full spectrum of light to heavy hydrocarbons, consistent with live oils, occurs in thermal extracts of all samples. Gas chromatography fingerprints of samples with Ro > 0.7% closely resemble waxy oils derived from lacustrine organic matter (OM); fingerprints of lower maturity samples are not yet as wax rich. The inferred petroleum type organofacies of all samples is paraffinic high wax with low organic sulfur levels. Hydrocarbon generation from the least mature sample is characterized by one dominant activation energy at 55 kcal/mol, accounting for 87% of the total bulk reaction. Assuming a simplified geological scenario, i.e., a 3 K/My linear heating rate, primary petroleum is generated (transformation ratio, i.e., TR: 10%–90%) over a narrow temperature interval of only 23 °C. Onset (10% TR), maximum (Tpeak), and completion (90% TR) temperatures and Ro values are 141 °C at Ro 0.85%, 155 °C at Ro 1.08%, and 164 °C at Ro 1.2%, respectively. Primary gas generation (148–172 °C) occurs 10 °C later (300 m deeper) than the generation of C6+ compounds (138–161 °C). Secondary gas formation from oil cracking begins at 182 °C, maximizes at 197 °C, and is completed well before 225 °C (beginning of late gas generation from the secondary cracking of thermally matured, macromolecular organic matter) at 206 °C. Thus, primary and secondary oil cracking processes do not overlap under geological conditions. In line with a paraffinic high-wax oil petroleum type organofacies, cumulative fluids generated from the least mature sample fall within the black oil class over most of the primary kerogen conversion range up to 90% TR as indicated by low saturation pressures (Psat) and gas-oil-ratios generally below 160 Sm3/Sm3. Maturation results in relatively heavy fluids with Psat values in the range 40–70 bar when the free hydrocarbons, i.e., already present prior to pyrolysis, are included, and in lighter fluids with Psat values in the range 70–90 bar, when the free, mostly waxy hydrocarbons, are excluded. Systematics of physical properties and fluid compositions evolution reproduce the general behavior of naturally occurring petroleum sourced from lacustrine OM very well and fit physical properties and compositions of produced shale oils in the Songliao Basin at comparable maturity levels.

Investigating the performance of different applied voltages on lignite biomethanation in microbial electrolytic cell coupled anaerobic digestion

The performance of different applied voltages on the biomethanation of lignite is investigated in microbial electrolytic cells coupled with anaerobic digestion (MEC-AD). The cumulative methane production is only 35.1 mL/g lignite in the control reactor. However, the cumulative methane production is increased to 44.3 mL/g lignite in the MEC-AD reactor at the applied voltage of 1 V, and followed by 62.6 mL/g lignite (2 V), 102.8 mL/g lignite (4 V), and 123.8 mL/g lignite (8 V). The 3D fluorescence spectra further clarified that the applied voltage favored the hydrolysis of macromolecular organic matter such as humic acid in lignite. The microbial community abundance in the bulk solution shows that some specific microorganisms such as electroactive bacteria (Chloroflexi) and hydrogenotrophic methanogenic archaea (Methanobacterium) were well enriched in the MEC-AD reactors. These results indicate that MEC-AD facilitates direct interspecies electron transfer (DIET) between electroactive bacteria and archaea, and significantly increases methane production. However, the economic analysis concludes that the methane production at the applied voltage of 8 V could not compensate for the cost incurred by electricity. The MEC-AD reactor with an applied voltage of 4 V showed excellent biomethanation characteristics of lignite, which provides a basis for the resource utilization of lignite.

Combined effects of arsenate and benzene on Microcystis aeruginosa growth and arsenic metabolism

To comprehensively understand the ecological risks of the coexistence of organic pollutants benzene and inorganic arsenate (As(V)) in the aquatic environment, Microcystis aeruginosa, one of the dominant algal species in eutrophic waters, was taken as the experimental alga to explore their growth response, arsenic (As) metabolism and the dissolved organic matter (DOM) changes in water under individual and combined pollution for benzene and As, respectively. The results showed that the algal cells of M. aeruginosa could proliferate normally. No significant differences were found among treatments after 96 h exposure to benzene and As(V) individual or combined. Intracellular As(V) accumulation was the main metabolism path for this alga and was significantly correlated to As(V) concentration but not benzene in the environment under different treatments. Benzene could promote As accumulation in algae and the total As metabolism amount in an individual algal cell at low As(V) levels. Meanwhile, only low benzene concentration showed As accumulation promotion at high As(V) levels. Microcystins (MCs) release in media affected by As(V) was different with benzene concentrations. There were no significant differences of UV254 in media among different treatments which represented macromolecular organic matters and aromatic compounds containing CC and CO bonds. Total organic carbon (TOC) was relatively higher in benzene media than in other treatments. The infrared spectrum characteristics of dissolved organic matter (DOM) confirmed that benzene was degraded and converted obviously at high levels in media by algal cells. Meanwhile, the three-dimensional fluorescence spectrum analysis showed that benzene in media could restrict proteins released in DOM caused by algae cells. The results are of great significance to the application of microalgae in water bioremediation and the comprehensive understanding of the ecological effects and risks in aquatic ecosystems.

Performance Analysis of Anaerobic Digestion Coupled with Simultaneous Nitrification and Denitrification Process for Treating Alcohol Precipitation Wastewater of Chinese Patent Medicine

The alcohol precipitation wastewater discharged from the production of Chinese patent medicine (CPM) has an extremely high chemical oxygen demand (COD) and poor biodegradability. In this study, the biological treatment method of anaerobic digestion coupled with simultaneous nitrification and denitrification (SND) was adopted to investigate its efficiency and to explore the mechanism of pollutant degradation in this process. The results showed that after 220 days of debugging, the coupled process operated stably. The influent COD, total nitrogen (TN), ammonium (NH4+-N), and lignin concentrations were 21,000 mg/L, 400 mg/L, 200 mg/L, and 1800 mg/L, respectively. The removal efficiencies of COD, TN, NH4+-N, and lignin were 97%, 85%, 96%, and 75%, respectively. Spectral detection technology analysis revealed that the wastewater contained alkanes, olefins, phenols, alcohols, unsaturated organics, aromatic compounds, and humic acids. After the treatment by each unit of the process, the three-dimensional fluorescence intensity decreased by 86%; the standard volume of fluorescence area integration declined by 78%; the stretching vibration band of aromatic compounds showed peak splitting; and the molecular weight parameter value in the ultraviolet region increased. These findings demonstrated that the humic acid substances in the wastewater were degraded, and the effect of removal of the macromolecular organic matter was remarkable.

BOD/COD ratio as a probing index in the O/H/O process for coking wastewater treatment

Biodegradation of coking wastewater (CWW) containing high concentrations of toxic pollutants with nutritional imbalance is challenging. Biodegradability estimated as the ratio of 5-day biochemical oxygen demand (BOD5) to chemical oxygen demand (COD) was studied along with the influential operational factors in a full-scale oxic/hydrolytic & denitrification/oxic (O/H/O) plant for CWW treatment. The influential factors for the B/C ratio in each unit of the O/H/O provided by the experimental and theoretical BOD5 were elucidated. Batch experiment with various sludge inoculation settings showed that the B/C ratio of raw CWW increased from 0.38 ± 0.04 to 0.47 ± 0.05 after flocculation pretreatment due to the removal of sulfide and cyanide. In the O1 reactor, quickly depleted biodegradable pollutants resulted in a drastic decrease of the B/C ratio to 0.1 ± 0.02 together with a reduction in the CWW toxicity. In the H reactor, the B/C ratio increased to 0.28 ± 0.04 because of the hydrolysis of residual macromolecular organic matter and nitrite accumulation from the denitrification process. The B/C ratio in the O2 reactor dropped below 0.06 along with the complete nitrification. The relative abundance of organic pollutants, the structure and function of bacterial community were analyzed in each reactor to explain the changes in the B/C ratio. On the whole, the monitoring of the B/C ratio along different stages of the CWW treatment is an approach suitable to follow the efficacy of functional bacterial groups and their responses to the water characteristics. The B/C ratio thus becomes a marker of the extent of nitrogen transformations, CWW detoxification and mineralization of organic compounds. More broadly, the B/C ratio helps optimize the operation parameters of biological processes and indicate the functionality of each unit.

Macromolecular organic matter in samples of the asteroid (162173) Ryugu.

Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu's parent body.

Effect of freezing-air thawing pretreatment of cutting fluid wastewater on the organics' distribution, transfer and transformation

The cutting fluid wastewater was treated by freezing-air thawing method. After thawing, stable stratification occurred in the thawing wastewater, and the froth floated on the liquid surface, and the liquid from top to bottom was divided into the first layer, the second layer, the third layer and the fourth layer. The molecular weight (MW) distribution and organics characteristics of the froth layer and each layer wastewater were analyzed by ultrafiltration membrane filtration combined with mass balance, three-dimensional fluorescence excitation-emission matrix spectroscopy, ultraviolet absorption spectroscopy, flourier transform infrared spectroscopy and droplet size analysis. The results showed that the cutting fluid wastewater contained 66.74 % organics with MW > 100 kDa and 17.04 % organics with MW < 1 kDa, and the organics might contain aromatic and heterocyclic compounds. After three times of freezing-air thawing: 27.53 % of organic matter was volatilized into the air; the froth layer was mainly macromolecular organic matter with MW > 100 kDa, accounting for 94.59 %; from the froth layer to the fourth layer wastewater, the content of macromolecules with MW > 100 kDa gradually decreased, while the content of small molecules with MW < 1 kDa gradually increased. The results of molecular weight distribution analysis, spectroscopy analysis and droplet size analysis indicated that during the freezing-air thawing process, there was not only the demulsification maybe but also the destruction of molecular structure. The molecular weight distribution of the mixture of the froth layer and the fourth layer wastewater were close to that of the raw cutting fluid wastewater, so the mixture of the froth layer and the fourth layer wastewater could be reused in metal process. The wastewater in the first, second and third layers had better biodegradability, which could be treated by biological method.

Performance influence of polyacrylic acid dispersant on nuclear grade anion exchange resin

Secondary circuit water chemistry control is vital for the safe operation of nuclear power plants. Polyacrylic acid (PAA) is used in the secondary circuit water system to reduce the fouling of the steam generator (SG) because of its good dispersion effect. However, PAA as a macromolecular organic matter possibly causes organic fouling for anion exchange resin of the water purification system and affects its performance. Some research reported that the performance of resin changes after PAA application. But it is not clear whether this change is related to PAA. In this research, the anion resins were performed for five cycles, and each cycle included batch PAA adsorption, dynamic PAA desorption and resin rinse. Results showed that NaOH solution could realize the desorption of PAA on anion resin, but desorption solution and rinse water consumption slightly increased with the cycle number. Meanwhile, residual PAA linearly increased with the cycle number, but the rate was relatively slow. Furthermore, the performance influence of PAA on anion resin was investigated. The exchange capacity and kinetic performance for anion resin slightly decreased after PAA cycle. The effluent conductivity of anion resin bed increased after PAA cycle, but it could not cause the adverse influence of sodium leakage. The contrast experiment of H2SO4 cycle showed that resin aging was the primary reason for the change of resin performance, rather than residual PAA. Within the fewer cycles, PAA and anion resin had better compatibility.