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Myriophyllum aquaticum (M. aquaticum), as a Cd-highly enriched and tolerant species, has greater application in phytoremediation of Cd-polluted waters. Mechanisms of Cd uptake and transport of M. aquaticum were comprehensively investigated in this work. Transport direction of Cd was observed both from the roots to the aboveground and vice versa. The aboveground can be harvested during vigorous growth and flowering periods, further improving the efficient phytoremediation of Cd-polluted wastewater. Moreover, analysis of transpiration inhibition, low-temperature treatment and metabolic inhibition indicated that the uptake and transport of Cd by M. aquaticum can be achieved via the coexistence of the free diffusion-dominated apoplast pathway dominated by transpiration and the ''cellular pathway'' dominated by active absorption, with the active energy-demanding cellular pathway playing a dominant role. The obtained results have important implications in the in-depth exploration of uptake, transport and distribution mechanisms of heavy metals during phytoremediation of aquatic plants.

In recent years, the phenomenon of black–odorous water has occurred frequently, and constructed wetlands have been widely used as an effective means of treating black–odorous water. In order to achieve the goal of low-carbon and high-efficiency long-term clean-up of black–odorous water, the modular constructed wetland system was optimized in this study. The optimized modular constructed wetland consisted of aeration, denitrification, and phosphorus removal, of which the denitrification module was a sulfur–iron autotrophic denitrification unit and the phosphorus removal module was a polyaluminum chloride composite filler phosphorus-removal unit. Experimental findings indicated that modular systems with layout ratios of 1:3:1 (A) and 1:2:2 (B) exhibit outstanding performance in remediating contaminants from black–odorous water. Notably, system B demonstrated superior treatment efficiency. Under conditions of high pollution loading, system B consistently achieved stable removal rates for COD (95.79%), TN (91.74%), NH4+-N (95.17%), and TP (82.21%). The combination of along-track changes and high-throughput sequencing results showed that the synergies among the units did not produce negative effects during the purification process, and each unit realized its predefined function. Changes in the substrate and internal environment of the wetland units caused changes in the microbial populations, and the unique microbial community structure of the units ensured that they were effective in removing different pollutants.

The chemical modification of natural palm fibers with an alkali treatment and the silane coupling agent KH570 were studied to determine the superior mechanical performance and solid engineering application properties of natural fiber/polymer/cement composites. These kinds of natural plant fibers can be easily obtained in China. The characterization of the fibers and composites were performed by Fourier transform infrared spectroscopy, thermogravimetric analysis, mechanical property testing, water absorption testing, and scanning electron microscopy. The results showed that chemical modifications can remove part of the cellulose, hemicellulose, and impurities in the fibers. In addition, the functional groups were confirmed to be grafted onto the fibers, which may cause the fibers to be more compatible with the matrix. Among the fibers studied, the 2 + 5/3% sample (treated first with 2% alkali, then with the 5% silane coupling agent, and subsequently mixed into the system of 3% cement and polymer emulsion) showed a tensile strength of 2.12 MPa, a tensile elongation of 155.114%, and water absorption of 19.65%.

Dewatering of sludge is a key problem that must be solved in the sewage sludge disposal industry. In this study, a series of process optimization tests were conducted to learn how to improve sludge treatment. The optimum process of sludge leaching treatment was studied in a specially designed 100-L reactor system. Four factors were investigated and nine batches of bioleaching tests were run at three levels of these factors. Orthogonal experiments showed that the effect of sludge return ratio and aeration rate on the sludge moisture content was significant and hydraulic retention time (HRT) had a clear effect, but nutrient types had a reduced effect on the moisture content of sludge. The primary and secondary order of each factor is reflux ratio > aeration rate > HRT > nutrient type. Under the optimal process, three batches of sludge were processed and the moisture content of the filter press cake was reduced to less than 60%, the organic matter content reduced to below 5%, and the concentration of heavy metals (Cu, Zn, Pb, and Cr) was much lower than the agricultural standard limit, which is suitable for landscaping, composting, and incineration power generation and other resource applications.

The extensive use of sulfonamides seriously threatens the safety and stability of the ecological environment. Developing green inexpensive and effective adsorbents is critically needed for the elimination of sulfonamides from wastewater. The non-modified biochar exhibited limited adsorption capacity for sulfonamides. In this study, the attapulgite-doped biochar adsorbent (ATP/BC) was produced from attapulgite and rice straw by calcination. Compared with non-modified biochar, the specific surface area of ATP/BC increased by 73.53–131.26%, and the average pore width of ATP/BC decreased 1.77–3.60 nm. The removal rates of sulfadiazine and sulfamethazine by ATP/BC were 98.63% and 98.24%, respectively, at the mass ratio of ATP to rice straw = 1:10, time = 4 h, dosage = 2 g∙L−1, pH = 5, initial concentration = 1 mg∙L−1, and temperature = 20 °C. A pseudo-second-order kinetic model (R2 = 0.99) and the Freundlich isothermal model (R2 = 0.99) well described the process of sulfonamide adsorption on ATP/BC. Thermodynamic calculations showed that the adsorption behavior of sulfonamides on the ATP/BC was an endothermic (ΔH > 0), random (ΔS > 0), spontaneous reaction (ΔG < 0) that was dominated by chemisorption (−20 kJ∙mol−1 > ΔG). The potential adsorption mechanisms include electrostatic interaction, hydrogen bonding, π–π interaction, and Lewis acid–base interactions. This study provides an optional material to treat sulfonamides in wastewater and groundwater.

A composite material of sodium dodecyl benzene sulfonate- (SDBS-) modified maifanite and anhydride-modified Fe@SiO2@PEI (PEI) was used as an adsorbent for the removal of hexavalent chromium (Cr(VI)) and bivalent cadmium (Cd(II)) from groundwater by using column experiments and simulated PRB test. In this study, the optimum proportion of SDBS-modified maifanite and anhydride-modified Fe@SiO2@PEI was 5 : 1. In the column experiments, it was found that the penetration time increased with the increase of the initial concentrations (30, 60, and 90 mg/L) and the decrease of the flow rates (5.45, 10.9, and 16.35 mL/min) at an influent pH of 6.5±0.3. It was also obtained that the removal rates of Cr(VI) and Cd(ІІ) reached 99.93% and 99.79% at an initial Cr(VI) and Cd(ІІ) concentration of 30 mg/L with the flow rate of 10.9 mL/min, respectively, at 6 h. Furthermore, excellent removal effectiveness of Cr(VI) and Cd(ІІ) (85.94% and 83.45%, respectively) was still achieved in simulated PRB test at a flow rate of 5.45 mL/min with the heavy metal solution concentration of 5.0±0.5 mg/L (Cr(VI) and Cd(II) concentration were, respectively, 5.0±0.5 mg/L); and the adsorbent had not completely failed by the end of the trial. Yoon-Nelson model was successfully applied to predict the breakthrough curves for the assessment of composite material heavy metal removal performance and was in good agreement with the experimental data of the heavy metal removal efficiency. The strong removal ability of the adsorbent could be attributed to the fact that maifanite with a large diameter can provide support and increase the permeability coefficient and porosity and that zero-valent iron (ZVI) can convert Cr(VI) to Cr(III) and improve the adsorption capacity of maifanite. The obtained results suggested that the novel PRB fillers have great significance for preventing and controlling Cr(VI)/Cd(ІІ)-contaminated groundwater.

In this study, a novel lab-scale biofortification-combination system (BCS) of Oenanthe javanica and Bacillus series was developed to improve the treatment ability of vertical subsurface flow constructed wetlands (VSFCW) at low temperatures (0–10 °C). The results showed that BCS-VSFCW overcame the adverse effects of low temperature and achieved the deep removal of nutrients. In addition, the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) by BCS-VSFCW were 38.65%, 28.20%, 18.82%, and 14.57% higher than those of blank control, respectively. During the experiment, Oenanthe javanica and low temperature tolerant Bacillus complemented each other in terms of microbial activity and plant uptake. Therefore, VSFCW combined with Oenanthe javanica and low temperature tolerant Bacillus has a promising future in low temperature (

Iron-carbon substrates have attracted extensive attention in water treatment due to their excellent processing ability. The traditional iron-carbon substrate suffers from poor removal effects, separation of the cathode and anode, hardening, secondary pollution, etc. In this study, a new type of iron-carbon-loaded substrate (NICLS) was developed to solve the problems of traditional micro-electrolytic substrates. Through experimental research, a preparation method for the NICLS with Fe and C as the core, zeolite as the skeleton, and water-based polyurethane as the binder was proposed. The performance of the NICLS in phosphorus-containing wastewater was analyzed. The results are as follows: The optimal synthesis conditions of the NICLS are 1 g hydroxycellulose, wood activated carbon as the cathode, an activated carbon particle size of 200-60 mesh, and an Fe/C ratio of 1:1. Acidic conditions can promote the degradation of phosphorus by the NICLS. Through the characterization of the NICLS (scanning electron microscope (SEM), X-ray diffractometer (XRD), and energy-dispersive spectrometer (EDS), etc.), it is concluded that the mechanism of the NICLS phosphorus removal is a chemical reaction produced by micro-electrolysis. Using the NICLS to treat phosphorus-containing wastewater has the advantages of high efficiency and durability. Therefore, it can be considered that the NICLS is a promising material to remove phosphorus.

Bioleaching is a successful and cost-effective strategy with which to remove heavy metals from contaminated sludge. Most of the current studies on bioleaching are concentrated on municipal sludge, and bioleaching of tannery sludge has not been studied extensively. The present study investigated the bioleaching of chromium (Cr) from tannery sludge using the mixture of iron-oxidizing bacteria (Acidithiobacillus ferrooxidans) and sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) in batch flasks. Changes in the pH, ORP, Fe2+ and SO4 2- concentrations and the efficiency of bioleaching of Cr from tannery sludge were analyzed. The results showed that the bioleaching efficiency of co-inoculation of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans was better than any of them. The co-inoculation with a mixture of iron-oxidizing and sulfur-oxidizing bacteria together with the addition of Fe2+ and elemental sulfur accelerated acid production and an increase in the oxidation-reduction potential originating from the bio-oxidation of Fe2+ and elemental sulfur. The bioleaching efficiency of co-inoculation of Cr increased as the pH of sludge decreased, reaching a maximum removal of 97.1%. The residual Cr concentration which is 531 mg/kg in bioleached sludge is below the thresholds for agriculture, according to China National Standard GB4284-2018 (<1000 mg/kg dry weight) for pollutants in sludges from agricultural use. The bioleaching efficiency was distinctly correlated with pH or ORP. The data presented showed that the bioleaching efficiency was negatively correlated (R² = 0.9864) with pH and positively (R² = 0.9821) with ORP, which implied the existence of a substantial indirect leaching mechanism responsible for Cr solubilization. [ABSTRACT FROM AUTHOR]

In this study, an artificial wetland filler matrix capable of effectively fixing phosphorus was prepared using a non-combustion process to save energy. To evaluate the adsorption performance of this filler, adsorption experiments were performed and the phosphorus adsorption mechanism characterization was studied. An alkaline environment was found to be conducive to the increase of adsorption capacity, but excessive alkalinity was not conducive to adsorption. Static adsorption experiments showed that the phosphorus removal rate could reach 95% in the simulated phosphorus-containing wastewater after adsorption completion. The adsorption process is closely simulated by the pseudo-second-kinetic adsorption model. The isothermal adsorption experiment data were consistent with the Langmuir and the Freundlich adsorption isotherms. The characterization results showed a large number of micropores and adsorption binding sites inside and on the surface of the filler. Speciation analysis on the adsorbed phosphorus revealed that chemisorption by calcium in this filler was the dominant adsorption mechanism. The research results of this study provide the basis and reference for the development of high-efficiency phosphorus removal filler in constructed wetlands. [ABSTRACT FROM AUTHOR]

Bioleaching has been demonstrated to be an effective technology for the removal of heavy metals and sludge dewaterability. Since bacteria gain nutrients by diffusion of soluble compounds, the insolubility of elemental sulfur may slow the growth of bacteria. Thus, it is very important to find an energy substance quickly become available to Acidithiobacillus thiooxidans. This paper studies the improvement of sludge dewaterability and heavy metal removal with sodium thiosulfate as the source of energy for Acidithiobacillus thiooxidans. Through orthogonal experiments with specific resistance to filtration (SRF) as the target index, four factors (FeSO4 dosage, Na2S2O3 dosage, sludge reflux ratio and sludge moisture content) were identified to be the important influencing parameters. The optimal conditions were: FeSO4 dosage, 8 g/L; Na2S2O3 dosage, 1.5 g/L; sludge reflux ratio, 30%; sludge moisture content, 97%. Results indicated that the SRF of the sludge decreased from 9.89 x 1012 to 1.03 x 1011 m/kg. The removal efficiencies of heavy metals Cu, Zn, Pb and Cr could reach 83%, 78%, 31% and 38% within 3 days, respectively. These results confirm the potential of sodium thiosulfate as an alternative energy substance in bioleaching to improve sludge dewaterability as well as removal of metals. [ABSTRACT FROM AUTHOR]

A novel process for sewage sludge bioleaching by mixed Thiobacilli (Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans) using a 12-stage, 180 L working volume continuous plug-flow bioreactor, is presented. The objective of the present study was to assess the impact of some parameters on the sludge dewaterability and to improve the sludge dewaterability by optimization of these parameters. The parameters examined were sludge moisture content, nutrients dosage, aeration rate, and the number of reactors. The order of the influence of these factors on sludge dewaterability was found to be sludge moisture content>nutrients dosage> aeration rate> number of reactors. The optimized conditions were: sludge moisture content, 98.0%, nutrients dosage, 9 g/L, aeration rate, 8 m³/h, and 10 reactors. Confirmation experiments conducted under optimum conditions demonstrate the sludge dewaterability to be remarkably improved. After 2 days of bioleaching, the moisture of bioleached sludge cake was reduced to below 60%. [ABSTRACT FROM AUTHOR]

Bioleaching is a promising technology for removal of metals from sludge and improvement of its dewaterability. Most of the previous studies of bioleaching were focused on removal of metals; bioleaching in cold environments has not been studied extensively. In this study, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were acclimated at 15 °C and co-inoculated to explore the optimal conditions for improvement of sludge dewaterability and removal of metals by the sequencing batch reactors. The data show after 6 days of bioleaching at 15 °C, 89.6% of Zn, 72.8% of Cu and 39.4% of Pb were removed and the specific resistance to filtration (SRF) was reduced to ~12%. In addition, the best conditions for bioleaching are an initial pH of 6, a 15% (v/v) inoculum concentration, and A. thiooxidans and A. ferrooxidans mixed in a ratio of 4:1. We found that bioleaching of heavy metals is closely related to final pH, while the sludge SRF is dominated by other factors. Bioleaching can be completed in 6 days, and the sludge dewaterability and removal of metals at 15 °C meet the requirements of most sewage treatment plants. [ABSTRACT FROM AUTHOR]

The increasingly serious ecological security issues of lake systems have aroused increasing political and academic attention. Based on research regarding ecological security domestically and abroad, this study brings forth the concept of lake ecological security. A new selection-systemweight- standardization-standards-calculation framework for ecological security at the watershed scale was proposed, and it integrates several existing methods, including the ''driverpressure- state-impact-response'' framework, the analytic hierarchy process and the fuzzy assessment model, to systematize the lake ecology security assessment process and meet the needs of watershed management. This systematic framework was applied to comprehensively assess the ecological security of an interior lake basin in China from2005 to 2013, using the year 2000 as a comparative reference. The results illustrated that the ecological security index (ESI) values in 2000 and 2013were 0.58 at the ''common'' level and 0.61 at the ''good'' level, respectively, in the study area. From 2005 to 2012, the ESI values were stable, mostly between 0.4 and 0.6 at the ''common'' level with the exception of 2007 at the ''poor'' level. Then, with the result of the individual assessment in 2000 was used as the reference level, we found that the response was better than the reference level, the state was nearly equal to the reference level, and the driving force was close to the reference level; however, the pressure and impact were relatively not ideal. These results can be used as the basis for lake eco-environmental management. [ABSTRACT FROM AUTHOR]