Environmental Technology最新文献

Nitrate pollution in groundwater has steadily increased globally, posing a potential threat to human health. Introduction of exogenous electron donors can significantly enhance nitrogen removal from nitrate-contaminated groundwater. Yet, conventional individual autotrophic or heterotrophic denitrification approaches have the disadvantage of low efficiency or high cost. This study investigated the performance of a laboratory-scale solid-phase denitrification (SPD) permeable reactive barrier (PRB) using a polyhydroxybutyrate-co-valerate (PHBV)/pyrite mixture as an electron donor for groundwater denitrification. Two different mass ratios (1:1 and 1:2) were established for the experimental setup. The results showed that under influent levels between 20 and 37 mg·L-1, the PHBV/pyrite system at a ratio of 1:1 achieved a maximum nitrate removal efficiency of 97.03%, with a nitrate removal rate of 99.13 mg ${\mathrm{NO}}_3^{-}\text{-}N$ ${\mathrm{NO}}_3^{-}\text{-}N$·L^-1·d^-1. Moreover, the PHBV/pyrite system at 1:2 reached 97.65% and 111.04 mg ${\mathrm{NO}}_3^{-}\text{-}N$·L^-1·d^-1 in terms of the optimum nitrate removal efficiency and rate. Dissolved organic carbon was undetectable in the effluent in both systems. The nitrate removal performance of the PHBV/pyrite system at 1:2 was superior to the one at 1:1, implying appropriate addition of pyrite in mixtrophic systems could enhance denitrification in groundwater. Additionally, the dominant genera identified were respectively Cloacibacterium and Acinetobacter in two systems, indicating that varying PHBV/pyrite ratios can modulate the succession of dominant nitrogenremoving microorganisms. Specifically, the system at 1:2 favoured aerobic microbial growth, thereby enhancing the efficiency of biological nitrogen removal. The findings have provided a valuable alternative for mixtrophic denitrification in in-situ remediation of nitrate-polluted groundwater.

Disgusting fishy odor could break out inside oligotrophic drinking waterbody in winter with low temperature. In preceding study, six species of fishy odor-producing microalgae and totally twenty fishy odorants were identified in drinking water source of Tongyu River, however, contributions of odorants and microalgae to whole fishy odor were unclear. In this study, odor contribution of microalgae and corresponding odorant to whole fishy odor was evaluated comprehensively. The results indicated that 2,4-decadienal, 2,6-nonadienal and 2,4-heptadienal were key fishy odorants based on OAV evaluation. Even though OAV of some odorants were below one, 80.6-90.79% of fishy intensities were explained for source water by reconstitution test. Approximately, 83.93%, 88.89%, 82.69%, 90.38%, 83.02%, 88.46% of fishy intensities were explained for Dinobryon sp., Cryptomonas ovate, Cyclotella, Ochromonas sp., Synedra, Melosira based on reconstituted samples, suggested that there existed synergistic effect for fishy odor among odorants. By assessing gross production of odorants, gross OAV of odorants, odorant production for single cell, gross odorant ratio and gross OAV ratio, contribution rank of isolated microalgae to whole fishy odor from maximum to minimum should be Ochromonas sp., which accounted for 21.2% of gross odorant's OAV, Melosira (accounted for 19.68%), Cryptomonas ovate (accounted for 19.63%), Dinobryon sp. (accounted for 18.27%), Synedra (accounted for 14.54%), Cyclotella (accounted for 6.68%). Contributions of multiple odorants and microalgae to fishy odor were first studied, which will provide more scientific basis for managing fishy odor in drinking water.

Agarase enzymes are critical in industries like food, cosmetics, and medicine where they play a critical role in DNA recovery, food gelling, cosmetic formulations, and waste treatment. However, current agarase sources often face limitations related to low yields, inconsistent activity, and high production costs. Therefore, there is a need to identify and optimize more efficient microbial sources for industrial-scale agarose production. This study is an exhaustive investigation into the optimized production of extracellular agarase from a microbial source. Through qualitative-quantitative analysis, the study optimizes the growth conditions of Microbulbifer sp. for enhanced agarase production. Response surface methodology is used to investigate the interactive effects of key parameters to get the optimized conditions as 0.3% agar, pH 7, 25°C temperature, and 36-hour incubation time, confirmed by a verification experiment yielding 317.97 μmol min^-1 agarase activity (F-value of 44.75 and an R-squared of 0.9827). The study also explores various machine learning algorithms where radial basis function neural network performed best with R-squared values of 0.989 and low mean squared error of 0.44, indicating the reliability and robustness of predicting agarase activity with high accuracy and generalization. The optimized production conditions and machine learning predictions offer significant improvements in the scalability and efficiency of agarase production with incubation time and temperature having the most dominating effect on agarase production. These findings would help in scaling up production and real-time adjustments during bioreactor operations in an industrial setup.

The inner eggshell membrane (ESM) sanctions the unfettered conveyance of air across the membrane, ensuring the air provision for embryonic development. As such, the electrostatic spinning technique was availed to fabricate large-scale and flat-sheet 'artificial' eggshell membranes by extracting keratin from waste egg membranes. Keratin within eggshell membranes was initially extracted via the chemical reduction method. Subsequently, diverse electrospinning conditions encompassing the type and concentration of additives as well as the electrospinning voltage were utilised to explore their impact on membrane morphology, wetting, and mechanical attributes. Experimental outcomes demonstrated that the ESM-based nanofiber membrane with salubrious morphology, anti-wetting, and mechanical properties could be procured by adding 12 wt% PVA into the keratin solution at 10.5 kV. Eventually, DCMD experiments for the ESM-based nanofiber membrane evinced that a stable water flux (10 LMH) and salt rejection rate could be discerned throughout the 150-min operational tenure, yet its efficacy lags behind other reported membranes. In light of the lofty porosity (>70%) and meager thermal conductivity of ESM (0.04 W/m·K), ESM nanofiber was coalesced with commercial PTFE membrane to fashion a dual-layer porous composite MD membrane utilised in VMD. Experimental findings divulged that the ESM-PTFE hybrid membrane possesses a relatively elevated water flux (30.21 LMH), being commensurate with the reported PTFE-based MD membranes. Accordingly, this research can provide the theoretical underpinning for the fabrication of ESM-based nanofiber membranes by means of the electrostatic spinning approach, and is conducive to the highly efficient and highly valuable exploitation of waste eggshells.

The complexity of ecological remediation technology restricts its long-term application in engineering practice. In this study, a simple top-down mussels-bacteria (TDMB) integrated system used for river water quality improvement was constructed, and the long-term operation performances accompanied by the corresponding mechanisms were investigated. The results showed that during 161 days of operation, the average removal efficiency achieved was 75.45% for COD, 79.41% for ammonia nitrogen and 70% for total nitrogen (TN), while the contribution proportions of mussels and immobilized microorganisms in the TN removal were 28.07% and 69.77%, respectively. High-throughput sequencing revealed that the dominant microorganisms for immobilization were norank_SC-I-84 (10.52%), norank_PHOS-HE36 (9.58%), norank_Anaerolineaceae (3.04%), Nitrospira (2.64%), norank_Gemmatimonadaceae (2.36%) and norank_Pirellulaceae (2.113%), all of which were involved in nitrogen removal. This study provided a promising strategy and gained insight into the corresponding mechanisms for the remediation of polluted rivers.

Due to the high concentrations of chemical oxygen demand (COD) and total volatile acids (TVA) in the range of 18,000-20,000 mg/L and 4,900-5,600 mg/L, respectively, the treatment of citric acid production wastewater is a challenge. An anaerobic hybrid reactor (AHR) was used to treat this wastewater. The AHR operated at the maximum organic loading rate (OLR) of 7.6 kg COD/m³/d and a hydraulic retention time (HRT) of 2.5 days without any inhibition. The COD removal efficiency, methane yield, and methane content were 90%, 0.25 Nm³ CH₄/kg COD removed, and 65%, respectively. Moreover, the activities of acetoclastic and hydrogenotrophic methanogens were approximately 108% and 63% higher than those of the initial inoculum, respectively. After increasing OLR to 8.3 kg COD/m³/d, TVA was accumulated at 5,200 mg/L, leading to failure. The main organic acids were acetic acid (AA) and propionic acid (PA) with concentrations of 2,800 and 1,300 mg/L, respectively. Syntrophic methanogenic consortia (SMC) were augmented into the AHR to recover the system. After 4 days of bioaugmentation, the TVA concentration decreased to less than 500 mg/L. Bioaugmentation also increased the ratio of the methanogens and acetogens to total microorganisms at the end of the recovery period to 32% and 23%, respectively. The AHR can be recovered to operate at OLR of 7.6 kg COD/m³/d within 18 days with good performance and microbial balance.

This study evaluated the suitability of wastewater treatment from tanneries located in the city of Arequipa, Peru. The growth of the microalgae-bacteria consortium enriched from wastewater ponds located in high altitude (2300 m above sea level) and areas with high ultraviolet radiation, was characterized under different wastewater dilutions, nutrient-corrected wastewater and various light periods in a laboratory-scale air-lift system over a 9-day cultivation period . The results indicate a higher COD removal at low dilutions (50%) in both 16L:8D and 24L:0D photoperiods, achieving 43.63% and 42.93%, respectively, however, a higher daily consumption rate was observed in treatments with 75% and 100% tannery wastewater, with the highest COD consumption recorded in the 100% treatment under the 16L:8D photoperiod, with at 85.50 mg L⁻¹ d⁻¹. Regarding nitrogen removal and consumption, significant results were obtained in the 100% treatment with 16L:8D photoperiod with values of 55.46% and 3.81 mg L^-1 d^-1 respectively, while for phosphorus all treatments had high removals (>95%). On the other hand, the highest productivity occurred in the 100% treatment for both the 16L:8D and 24;0 photoperiod with a value of 52.85 and 64.28 mg L^-1 d ^-1 respectively. Finally, by phosphorous supplementation in the medium, the productivity in all treatments improved, obtaining the maximum biomass productivity in the 75% 24L:0D treatment with 95,714 mg L^-1 d^-1. The maximum accumulation of lipids was 18.7% of the effluent with 100%, 16L:8D photoperiod. These results confirm that microalgae technology is an ecofriendly alternative to treat tannery beam house wastewaters.

Algae are known for their rich nutrients, which can enhance productivity of agricultural crops, making them valuable biostimulants. However, the use of microalgae for this purpose is still in its early stages, and there have been no studies conducted on lupine crops in Brazil so far. This study aimed to investigate the impact of microalgae extracts on the growth and productivity of white lupine. The experiment included four different microalgae extracts (Limnospira platensis, Nannochloropsis oculata, Tetradesmus obliquus, and Chaetoceros muelleri), applied either once or twice, along with a control group. The results showed that there was no interaction between the number of applications and the type of microalgae extract applied via foliar application in white lupine crops. The microalgae extracts did not have a significant impact on the 100-grain weight and yield of white lupine crops. The average height of white lupine plants at harvest was 117.04 cm, regardless of the treatment. However, there was a significant increase (13.12%) in the number of seeds per pod of white lupine with a single application of microalgae extract, regardless of the specific extract used. The height of the white lupine plants was not affected by the treatments during both the vegetative and reproductive phases. Further research is needed to optimise the bioactive extraction process, identify metabolites with biostimulant potential in the extracts, and determine the most effective application method (soil, seed, or foliar), as well as the optimal timing and frequency of foliar applications based on the crop's phenological stages.HighlightsFirst report of microalgae extracts used in Lupinus albus cultures in Brazil.Extracts of microalgae have no effect on the grain mass and productivity of white lupine.A single application of any microalgae extract enhanced the seed yield per white lupine pod.

Microcystins (MCs), a toxin produced by some species of the photosynthetic autotrophic cyanobacteria, are the most studied and monitored cyanotoxin in water. Water treatment plant (WTP) residuals are the byproduct of water treatment consisting of solids removed from WTP processes and have been shown to contain cyanobacterial cells. However, the presence of MCs in WTP residuals has not been systematically demonstrated. Samples from four different WTPs across the United States were used to quantify MCs in residuals while assessing extraction and quantification methods adapted from water samples for solid matrices. MCs were present in 100% of samples. MC-LA was the most prevalent variant in these samples (70.05% of MCs quantified by UPLC-PDA). Natural degradation observed in a WTP storage lagoon was also investigated to determine the impact of physical, chemical, and biological processes on MC concentrations in high-biomass residuals. This study demonstrates that residuals of various characteristics across the United States contain MCs, and no one method was found to maximize results consistently across all samples. Cyanotoxins accumulating in WTP residuals are a growing concern. Implications of this work can help regulations and future studies of potential reuse applications and understanding of potential ecological significance of MCs accumulating in WTP residuals.

Development of high-performance mixed matrix membranes (MMMs) is of great significance for CO₂ separation membrane technology, in order to improve the commercial competitiveness and practical applications. Montmorillonite (MMT) was developed as a dopant to fabricate Polyether block amide (Pebax1074)-based MMMs for strengthening the CO₂/N₂ separation. The morphology, chemical groups, microstructure, and thermal properties of MMMs were characterised by scanning electron microscope, FTIR spectroscopy, X-ray diffraction and thermal analysis, respectively. The effects of MMT contents, permeation pressure and permeation temperature on the gas separation performance of the Pebax/MMT MMMs were investigated. The results show that the uniformly dispersed dopants MMT in the membrane matrix significantly influence the thermal stability and the structural compactness of MMMs. Moreover, the CO₂ permeability monotonously increases in spite of the CO₂/N₂ selectivity first increasing and then decreasing with the MMT content elevating from 0% to 10% in MMMs. The highest CO₂/N₂ selectivity could reach to 120.3, along with the CO₂ permeability of 130.6 Barrer for the MMMs made by MMT content of 6%.