Weak Magnetic Field Accelerates Chromate Removal by Zero-Valent Iron

Weak magnetic field (WMF) was employed to improve the removal of Cr(VI) by zero-valent iron (ZVI) for the first time. The removal rate of Cr(VI) was elevated by a factor of 1.12-5.89 due to the application of a WMF, and the WMF-induced improvement was more remarkable at higher Cr(VI) concentration and higher pH. Fe2+ was not detected until Cr(VI) was exhausted, and there was a positive correlation between the WMF-induced promotion factor of Cr(VI) removal rate and that of Fe2+ release rate in the absence of Cr(VI) at pH 4.0-5.5. These phenomena imply that ZVI corrosion with Fe2+ release was the limiting step in the process of Cr(VI) removal. The superimposed WMF had negligible influence on the apparent activation energy of Cr(VI) removal by ZVI, indicating that WMF accelerated Cr(VI) removal by ZVI but did not change the mechanism. The passive layer formed with WMF was much more porous than without WMF, thereby facilitating mass transport. Therefore, WMF could accelerate ZVI corrosion and alleviate the detrimental effects of the passive layer, resulting in more rapid removal of Cr(VI) by ZVI. Exploiting the magnetic memory of ZVI, a two-stage process consisting of a small reactor with WMF for ZVI magnetization and a large reactor for removing contaminants by magnetized ZVI can be employed as a new method of ZVI-mediated remediation

Immediate and Long-Term Impacts of Potassium Permanganate on Photosynthetic Activity, Survival and Microcystin-LR Release Risk of Microcystis Aeruginosa

The immediate and long-term impacts of potassium permanganate (KMnO 4 ) as pre-oxidant on Microcystis aeruginosa and microcystin-LR (MC-LR) release risk were investigated. The cell density and the integrity of M. aeruginosa were determined by a flow cytometry, and typical photosynthetic parameters were measured by a pulse amplitude modulated fluorometer. The photosynthetic parameters were reduced to different degrees, accompanied with slight cytoclasis and complete degradation of extracellular MC-LR immediately after various dosages KMnO 4 oxidation (2-20mgL -1 ). In a 6-d cultivation following 5mgL -1 KMnO 4 oxidation, the cell density decreased from 3.9×10 6 to 0.6×10 6 cellsmL -1 , and then increased to 0.9×10 6 cellsmL -1 , while the extracellular MC-LR increased from 0 to 51.2μgL -1 . In the cultivation after 10mgL -1 KMnO 4 treatment, the intracellular MC-LR and cell activity significantly declined, while significant cytoclasis (cell density from 3.8×10 6 to 0cellsmL -1 ) and MC-LR release (increase from 0 to 15.2μgL -1 ) were observed. The photosynthetic parameters were found to be useful tools to predict the recovery tendency of M. aeruginosa cells, and the MC-LR release risk should be considered during KMnO 4 pre-oxidation in water-treatment plants

Synergistic Effects of Nano-Sized Titanium Dioxide and Zinc on the Photosynthetic Capacity and Survival of Anabaena sp.

Anabaena sp. was used to examine the toxicity of exposure to a nano-TiO2 suspension, Zn2+ solution, and mixtures of nano-TiO2 and Zn2+ suspensions. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Nano-TiO2 particles exhibited no significant toxicity at concentrations lower than 10.0 mg/L. The 96 h concentration for the 50% maximal effect (EC50) of Zn2+ alone to Anabaena sp. was 0.38 ± 0.004 mg/L. The presence of nano-TiO2 at low concentrations (<1.0 mg/L) significantly enhanced the toxicity of Zn2+ and consequently reduced the EC50 value to 0.29 ± 0.003 mg/L. However, the toxicity of the Zn2+/TiO2 system decreased with increasing nano-TiO2 concentration because of the substantial adsorption of Zn2+ by nano-TiO2. The toxicity curve of the Zn2+/TiO2 system as a function of incremental nano-TiO2 concentrations was parabolic. The toxicity significantly increased at the initial stage, reached its maximum, and then decreased with increasing nano-TiO2 concentration. Hydrodynamic sizes, concentration of nano-TiO2 and Zn2+ loaded nano-TiO2 were the main parameters for synergistic toxicity

Immediate and Long-Term Impacts of UV-C Irradiation on Photosynthetic Capacity, Survival and Microcystin-LR Release Risk of Microcystis Aeruginosa

In this study, the immediate and long-term impacts of shortwave ultraviolet (UV-C) irradiation on photosynthetic capacity, survival, and recovery of Microcystis aeruginosa were investigated. The risk of microcystin-LR (MC-LR) release during irradiation was also estimated. The cell density was determined by a flow cytometry, and typical chlorophyll fluorescence parameters, including the effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse amplitude modulated (PAM) fluorometer. Under various UV-C dosages (140-4200mJ cm -2 ), photosynthetic capacities were reduced, to different degrees, accompanied by slight cytoclasis and complete degradation of extracellular MC-LR immediately after irradiation. In a 6-d cultivation following UV-C irradiation, cell density and extracellular MC-LR in the samples treated by 140mJcm -2 UV-C irradiation increased from 4.0×10 6 cellsmL -1 and 8μgL -1 to 5.1×10 6 cellsmL -1 and 20μgL -1 , respectively. Significant M. aeruginosa cytoclasis (cell density from 4.0×10 6 to 1.0×10 6 cellsmL -1 ) and MC-LR release (2-25μgL -1 ) occurred when the UV-C dosage reached 350mJcm -2 . Cell cytoclasis and MC-LR release were enhanced in the cultivated samples under higher UV-C dosages. Results revealed that photosynthetic parameters were useful tools to predict the recovery profiles of M. aeruginosa cells, and the MC-LR release risk should be considered after UV-C inactivation

Effects of Different Algaecides on the Photosynthetic Capacity, Cell Integrity and Microcystin-LR Release of Microcystis Aeruginosa

Bench scale tests were conducted to study the effects of four common algaecides, including copper sulfate, hydrogen peroxide, diuron and ethyl 2-methylacetoacetate (EMA) on the photosynthetic capacity, cell integrity and microcystin-LR (MC-LR) release of Microcystis aeruginosa. The release of potassium (K + ) from cell membrane during algaecide exposure was also analyzed. The three typical photosynthetic parameters, including the effective quantum yield (F e ), photosynthetic efficiency (α) and maximal electron transport rate (rETR max ), were measured by a pulse amplitude modulated (PAM) fluorometry. Results showed that the photosynthetic capacity was all inhibited by the four algaecides, to different degrees, by limiting the energy capture in photosynthesis, and blocking the electron transfer chain in primary reaction. For example, at high diuron concentration (7.5mgL -1 ), F e , α and rETR max decreased from 0.46 to 0.19 (p\u3c0.01), from 0.20 to 0.01 (p\u3c0.01) μmol electrons m -2 s -1 /μmol photons m -2 s -1 , and from 160.7 to 0.1 (p\u3c0.001) μmolm -2 s -1 compared with the control group after 96h of exposure, respectively. Furthermore, the increase of algaecide dose could lead to the cell lysis, as well as release of intracellular MC-LR that enhanced the accumulation of extracellular MC-LR. The order of MC-LR release potential for the four algaecides was CuSO 4 \u3eH 2 O 2 \u3ediuron\u3eEMA

Effects of different algaecides on the photosynthetic capacity, cell integrity and microcystin-LR release of Microcystis aeruginosa

Bench scale tests were conducted to study the effects of four common algaecides, including copper sulfate, hydrogen peroxide, diuron and ethyl 2-methylacetoacetate (EMA) on the photosynthetic capacity, cell integrity and microcystin-LR (MC-LR) release of Microcystis aeruginosa. The release of potassium (K + ) from cell membrane during algaecide exposure was also analyzed. The three typical photosynthetic parameters, including the effective quantum yield (F e ), photosynthetic efficiency (α) and maximal electron transport rate (rETR max ), were measured by a pulse amplitude modulated (PAM) fluorometry. Results showed that the photosynthetic capacity was all inhibited by the four algaecides, to different degrees, by limiting the energy capture in photosynthesis, and blocking the electron transfer chain in primary reaction. For example, at high diuron concentration (7.5mgL -1 ), F e , α and rETR max decreased from 0.46 to 0.19 (p\u3c0.01), from 0.20 to 0.01 (p\u3c0.01) μmol electrons m -2 s -1 /μmol photons m -2 s -1 , and from 160.7 to 0.1 (p\u3c0.001) μmolm -2 s -1 compared with the control group after 96h of exposure, respectively. Furthermore, the increase of algaecide dose could lead to the cell lysis, as well as release of intracellular MC-LR that enhanced the accumulation of extracellular MC-LR. The order of MC-LR release potential for the four algaecides was CuSO 4 \u3eH 2 O 2 \u3ediuron\u3eEMA

Mechanistic Studies of Microcystic Aeruginosa Inactivation and Degradation by UV-C Irradiation and Chlorination with Poly-Synchronous Analyses

Poly-synchronous techniques were performed to investigate the inactivation and degradation mechanisms of Microcystic aeruginosa under UV-C irradiation and chlorination. Extracellular dissolved organic matter (EDOM) and intracellular dissolved organic matter (IDOM) properties were analyzed using excitation emission matrix (EEM) fluorescence spectroscopy, while the concentration of biochemical parameters including protein, phycocyanin, chlorophyll-a, and microcystin-LR was determined. Transmission electron microscopy was also used to obtained ultrastructural images. EEM analysis revealed that protein-like matters were the major EDOM fluorescence component, while amino acid-like and protein-like matters constituted IDOM with little amount of humic-like substances. In addition, the monitor of biochemical parameters showed that they had different susceptibility under the inactivation reactions. Poly-synchronous techniques confirmed that UV-C irradiation was more appropriate than chlorination for M. aeruginosa inactivation and degradation. The primary mechanism of UV-C irradiation was direct photo-degradation and indirect oxidation by reactive oxygen species, which effectively degraded the fluorescence EDOM and IDOM and caused decomposition of cytoplasmic inclusions and intracellular bioorganic substances. Different from UV-C, the inactivation during chlorination was due to the formation of HOCl, which permeated into the cyanobacteria cells and caused intracellular damage, accompanied with incomplete degradation of IDOM and harmful MC-LR

Prediction of Life Cycle Carbon Emissions of Sponge City Projects: A Case Study in Shanghai, China

In recent years, China has been vigorously carrying out the planning and implementation of Sponge City. Since the implementation of Sponge City projects involves substantial materials and energy consumption, it is significant to account corresponding carbon emissions and sinks. The existed studies about carbon emission of stormwater management measures, however, are not able to take the whole life cycle and different facilities into consideration. Therefore, this study develops a comprehensive accounting model based on Intergovernmental Panel on Climate Change (IPCC) guidelines and life cycle assessment (LCA) method to predict carbon emissions and carbon sinks of Sponge City projects more comprehensively and accurately. The model is applied to an actual residential community in Shanghai as a case study. Results show that the total indirect carbon emission is estimated to be 774,277 kg CO2 eq during a 30-year lifespan, among which carbon emissions from operation and maintenance phases are 2570 kg CO2 eq/year and 7309 kg CO2 eq/year, respectively, both directly proportional to the service life of the facilities. Three kinds of achievable carbon sinks are carbon sequestration in green space (5450 kg CO2 eq/year), carbon sink from rainwater utilization (15,379 kg CO2 eq/year) and carbon sink from runoff pollutant removal (19,552 kg CO2 eq/year). Carbon neutrality is expected to be reached after approximately 19 years. The established carbon emission accounting model can contribute to better planning and construction of Sponge City in China and enhance further energy conservation and carbon emission reduction