Utilization of water chestnut for reclamation of water environment and control of cyanobacterial blooms

Overgrowth of water chestnut (Trapa spp.) is a regional problem throughout Asia and North America because of waterway blockage and water fouling upon decomposition. In the present study, we investigated the potential of water chestnut to control cyanobacterial blooms, via a high content of phenolic compounds. In addition, we assessed the impact of biomass harvesting and crude extract application on nutrient balance. We showed that the floating parts of water chestnut contained high concentrations of total phenolics (89.2 mg g^?1 dry weight) and exhibited strong antioxidant activity (1.31 mmol g^?1 dry weight). Methanol-extracted phenolics inhibited growth of Microcystis aeruginosa; the half maximal effective concentration (EC₅₀) of the extracted phenolics was 5.8 mg L^?1, which was obtained from only 103 mg L^?1 of dry biomass (the floating and submerged parts). However, the crude extracts also added important quantities of nitrogen, phosphorus, and potassium (1.49, 1.05, and 16.3 mg g^?1, respectively; extracted dry biomass weight basis); therefore, in practice, nutrient removal before and/or after the extraction is essential. On the other hand, biomass harvesting enables recovery of nitrogen, phosphorus, and potassium from the water environment (23.1, 2.9, and 18.7 mg g^?1, respectively; dry biomass weight basis). Our findings indicate that water chestnut contains high concentrations of phenolics and exhibits strong antioxidant activity. Utilization of these resources, including nutrients, will contribute to reclamation of the water environment, and also to disposal of wet biomass.     

Influence of alum on cyanobacterial blooms and water quality of earthen fish ponds

Eruption of blue-green algal blooms occurs frequently in eutrophic lakes and fish ponds, with associated unpleasant odor and horrid scums. In the present study, we conducted a pre-test experiment in 3 m³ outdoor concrete ponds to determine the optimum concentration of aluminum sulfate (alum) required for reduction of the cyanobacterial blooms without negative effect on fish growth. As a consequence, 10 mg L^?1 alum was named as the optimum concentration that was applied in 1000 m³ earthen fish ponds. Obtained results showed that Secchi disc values significantly increased from 10 to 24 cm after 14 days of alum application. Alum-treated ponds showed a reduction in total phytoplankton counts by 94 and 96 % compared to the corresponding controls after 10 and 14 days, respectively. Abundance of blue-green algae in the treated ponds was decreased by 98 % compared to the corresponding control after 14 days of alum application. Consequently, dissolved oxygen, pH, total phosphorus, orthophosphate, and chlorophyll “a” content declined significantly. Our study revealed that using 10 mg L^?1 of alum is an effective way to control cyanobacterial blooms in eutrophic waters, especially in fish ponds, without negative effect in water quality.     

Removal of cyanobacterial blooms in Taihu Lake using local soils. II. Effective removal of Microcystis aeruginosa using local soils and sediments modified by chitosan

After sepiolite was modified with Fe3+ to increase its surface charge, the initial algal removal rate increased significantly, but its Q8h was not improved substantially at clay loadings below 0.1 g/L. Modification on netting and bridging properties of clays by either chitosan or polyacrylamide (PAM) dramatically increased flocculation (Q8h) of MA cells in freshwaters. Algal removal efficiencies of different solids, including Type III clays, local soils and sediments, were all improved to a similar level of >90% at a total loading of 0.011 g/L (contained 0.001 g/L chitosan) after they were modified with chitosan, making the idea of clearing up algal blooms using local soils/sediments possible. The mechanism of netting and bridging was confirmed to be the most important factor in improving the removal efficiency of cells, whereas clays also played important roles in the sedimentation of the floc.     

Hepatic nodular alterations in wild fish from a hyper-eutrophic freshwater system with cyanobacterial blooms: a species and seasonal comparison

Environmental Science and Pollution Research - This paper reports on the seasonal and species comparison of hepatic nodular alterations in two indicator fish species from the hyper-eutrophic...     

Eco-restoration: Simultaneous nutrient removal from soil and water in a complex residential-cropland area

An eco-restoration system to remove excess nutrients and restore the agricultural ecosystem balance was proposed and applied from August 2006 to August 2008 in a residential-cropland complex area (1.4 × 10⁵ m²) in Kunming, western China, where the self-purifying capacity of the agricultural ecosystem had been lost. The proposed eco-restoration system examined includes three main foci: farming management, bioremediation, and wastewater treatment. The results showed that the removal efficiencies of total phosphorus (TP) and total nitrogen (TN) from the complex wastewater were 83% and 88%, respectively. The Simpson’s diversity indices of macrophytes and zoobenthos indicated that the system had increased macrophyte and zoobenthic diversity as well as improved growth conditions of the plankton habitats. The results demonstrated that the proposed eco-restoration system is a promising approach for decreasing the output of nutrients from soil, improving agricultural ecosystem health, and minimizing the downstream eutrophication risk for surface waters.     

Simultaneous sampling of gas- and aerosol-phase TDI with a triple filter system

A new triple filter system sampler/model is proposed for the precise and accurate simultaneous sampling and determination of gas- and aerosol-phase 2,4-toluene diisocyanate (TDI). The system consists of two front Teflon filters for sampling aerosol-phase TDI and a final coated glass fiber filter to collect gas-phase TDI. The aerosol-phase TDI is collected on the first Teflon filter, while the second Teflon filter is used to estimate gaseous TDI adsorbed by the first. According to the gas adsorption test of two Teflon filters in series, the TDI gas adsorption fraction of the two filters is almost the same. Results of the evaporation test using pure TDI aerosols collected on the Teflon filter show that significant evaporation of the compound does not occur during sampling. These two findings allow the use of a model to estimate accurate gas- and aerosol-phase TDI concentrations. The comparison test with an annular denuder shows that the triple filter system can minimize the TDI sampling bias between the dual filter and the annular denuder systems.     

Removal of cyanobacterial blooms in Taihu Lake using local soils. I. Equilibrium and kinetic screening on the flocculation of Microcystis aeruginosa using commercially available clays and minerals

Algal removal abilities of 26 clays/minerals were classified into three categories according to the 8-h equilibrium removal efficiency (Q8h) and removal rate at a clay loading of 0.7 g/L. Type I clays (sepiolite, talc, ferric oxide, and kaolinite) had a Q8h > 90%, a t50 (time needed to remove 50% of the algae) < 15 min, and a t80 < 2.5 h. Type II clays (6 clays) had a Q8h 50-90%, a t50 < 2.5 h, and a t80 > 2.5 h. Type III clays (14 clays) with Q8h < 50%, t50 > 8 h and t80 > 14 h had no practical value in removal of algal blooms. When the clay loading was reduced to 0.2 g/L, Q8h for all the 25 materials decreased to below 60%, except for sepiolite whose Q8h remained about 97%. The high efficiency for sepiolite to flocculate M. aeruginosa cells in freshwaters was due to the mechanism of netting and bridging effect.     

活化粉煤灰改性壳聚糖絮凝除藻的研究

将活化后的粉煤灰滤液对壳聚糖进行改性,研究其絮凝除藻性能.实验表明,改性后的壳聚糖除藻性能优良,较少的用量(0.5 mL)可去除接近90%的藻.而分泌可溶性的胞外有机物(EOM)会优先争夺絮凝剂--壳聚糖,导致其投加量增加.适当增加改性壳聚糖投加量可以使藻絮体密实,增强抗水流冲击能力,由此展开改性壳聚糖投加量与絮凝除藻的动力学研究.最后,测定了絮凝上清液的藻光合活性,发现投加改性壳聚糖后有效降低了藻光合活性,防止水华二次爆发.     

Simultaneous removal of organic compounds and heavy metals from soils by electrokinetic remediation with a modified cyclodextrin

Thousands of sites are contaminated with both heavy metals and organic compounds and these sites pose a major threat to public health and the environment. Previous studies have shown that electrokinetic remediation has potential to remove heavy metals and organic compounds when they exist individually in low permeability soils. This paper presents the feasibility of using cyclodextrins in electrokinetic remediation for the simultaneous removal of heavy metals and polycyclic aromatic hydrocarbons (PAHs) from low permeability soils. Kaolin was selected as a model low permeability soil and it was spiked with phenanthrene as well as nickel at concentrations of 500 mg kg-1 each to simulate typical mixed field contamination. Bench-scale electrokinetic experiments were conducted using hydroxypropyl beta-cyclodextrin (HPCD) at low (1%) and high (10%) concentrations and using deionized water in control test. A periodic voltage gradient of 2VDC cm-1 (with 5 d on and 2 d off) was applied to all the tests, and 0.01 M NaOH was added during the experiments to maintain neutral pH conditions at anode. In all tests, nickel migrated as Ni2+ ions towards the cathode and most of it was precipitated as Ni(OH)2 within the soil close to the cathode due to high pH condition generated by electrolysis reaction. The solubility of phenanthrene in the flushing solution and the amount of electroosmotic flow controlled the migration and removal of phenanthrene in all the tests. Even though high flow was generated in tests using deionized water and 1% HPCD, migration and removal of phenanthrene was low due to low solubility of phenanthrene in these solutions. The test with 10% HPCD solution showed higher solubility of phenanthrene which caused it migrate towards the cathode, but further migration and removal was retarded due to reduced electric current and electroosmotic flow. Approximately one pore volume of flushing resulted in approximately 50% removal of phenanthrene from the soil near the anode. Sustained higher electroosmotic flow with higher concentration cyclodextrin and maintaining low soil pH near cathode should be investigated to increase removal efficiency of both phenanthrene and nickel.     

微生物絮凝剂去除废水中Cd（Ⅱ）的CCD优化及絮凝机制

应用CCD（中心复合设计）法研究了微生物絮凝剂去除废水中Cd（Ⅱ）的最佳条件组合,并根据傅里叶变换红外光谱与环境扫描电镜分析讨论了絮凝机制。CCD设计以Cd（Ⅱ）去除率为响应值,优化Cd（Ⅱ）初始浓度、MBFGA1投加量、溶液初始pH和反应时间4种因素。方差分析显示,模型F值为11.71,P〈0.0001,相关系数R=0.9154,拟合模型极显著,Cd（Ⅱ）初始浓度、pH和反应时间为显著性因素。在最优化条件下：Cd（Ⅱ）初始浓度23.60 mg/L,MBFGA1投加量27.74 mg/L,pH为9.5,反应时间15.97 min,检测实验Cd（Ⅱ）去除率高于99.5%。傅里叶变换红外光谱图表明,絮凝剂分子上羧基、羟基、磷酸基等官能团参与了絮凝过程,并形成了氢键。结合环境扫描电镜图分析得出,MBFGA1的絮凝机制包括化学反应、吸附架桥、氢键和范德华力结合等作用。     

Modification of exopolysaccharide composition and production by three cyanobacterial isolates under salt stress

Background, aim, and scope  

Polysaccharides are renewable resources representing an important class of polymeric materials of biotechnological interest, offering a wide variety of potentially useful products to mankind. Exopolysaccharides (EPSs) of microbial origin with a novel functionality, reproducible physico-chemical properties, stable cost and supply, became a better alternative to polysaccharides of algal origin. EPSs are believed to protect bacterial cells from desiccation, heavy metals or other environmental stresses, including hostimmune responses, and to produce biofilms, thus enhancing the cells chances of colonising special ecological niches. One of the most important stress factor is salt stress for microorganisms. The present investigation is aimed to determine correlation between salt resistance and EPS production by three cyanobacterial isolates (Synechocystis sp. BASO444, Synechocystis sp. BASO507 and Synechocystis sp. BASO511). It is also aimed to investigate the effect of salt concentrations on EPS production by cyanobacteria and effect of salt on monosaccharide composition of EPS.     

Simultaneous removal of phenanthrene and cadmium from contaminated soils by saponin, a plant-derived biosurfactant

Batch experiments were conducted to evaluate the performance of saponin, a plant-derived biosurfactant, for simultaneously removing phenanthrene and cadmium from the combined contaminated soils. Results showed that phenanthrene was desorbed from the contaminated soils by saponin with the partition of phenanthrene into surfactant micelle, meanwhile cadmium was effectively removed from the contaminated soils by the complexation of cadmium with the external carboxyl groups of saponin micelle. The efficiencies of saponin for the removal of phenanthrene and cadmium from the contaminated soils were greater than that of Triton X100 and citric acid, respectively. At concentration of 3750 mg/L, saponin has a removal rate of 87.7% and 76.2% of cadmium and phenanthrene, respectively, from the combined contaminated soil. The removals of cadmium and phenanthrene from the soils were not obviously constrained each other. Thus, saponin has the potential for the removal of heavy metal and PAHs from the combined contaminated soils.     

Removal of harmful cyanobacterial blooms in Taihu Lake using local soils. III. Factors affecting the removal efficiency and an in situ field experiment using chitosan-modified local soils

Effects of ionic strength, pH, organic content, cell concentration, and growth phase on the removal of MA cells using chitosan-modified sepiolite were studied in the laboratory. The MA removal efficiency increased with the increase of salinity for normal clay flocculation. In contrast, for chitosan-modified clays/soils, MA removal efficiency increased with the decrease of salinity. The removal efficiency of chitosan-modified sepiolite was not significantly affected by pH (6-9), but dropped dramatically beyond pH 10. Humic acid had a small negative effect on the removal of MA cells. Cells were removed more effectively by clays around the early senescence growth phase than other growth stages. The removal efficiency increased as the cell concentration increased. In a field enclosure of Taihu Lake, a loading of 0.025 g/L chitosan-modified local soils removed 99% algal cells and no increase of chlorophyll-a was observed during the following one month's monitoring process.     

Simultaneous selective removal of cesium and cobalt from water using calcium alginate-zinc ferrocyanide-Cyanex 272 composite beads

Environmental Science and Pollution Research - Composite beads consisting of Ca alginate mixed with zinc ferrocyanide (ZnFC) and Cyanex 272 were synthesized in order to selectively adsorb Cs+ and...     

Efficient removal and mechanisms of water soluble aromatic contaminants by a reduced-charge bentonite modified with benzyltrimethylammonium cation

A novel strategy utilizing the phenyls interaction and the hydrophobic affinity of available siloxane surface in the interlayer of bentonite was proposed to improve the sorption capabilities of organobentonites for water soluble aromatic contaminants. A unique organobentonite (65BTMA) was synthesized by intercalating benzyltrimethylammonium cation (BTMA⁺) into the interlayer of a reduced-charge bentonite with cation exchange capacity (CEC) of 65 cmol kg⁻¹. Phenol, aniline and toluene were used as model compounds of water soluble aromatic contaminants. Their respective removal efficiencies by 65BTMA were achieved at 83.3%, 89.2% and 97.3% at the initial concentration of 20 mg l⁻¹. To reveal the sorption mechanism, sorption characteristics of aromatic contaminants to 65BTMA were compared with that of aliphatic contaminants in similar molecular size. And various organobentonites were prepared by combining TMA⁺ (tetramethylammonium), BTMA⁺, HTMA⁺ (heptyltrimethylammonium) and CTMA⁺ (cetyltrimethylammonium) with two bentonites (CEC = 108 and 65 cmol kg⁻¹). To 65BTMA, sorption magnitudes of aromatic contaminants were much greater than that of aliphatic compounds with similar size; and dramatically higher than those to other organobentonites at low pollutant concentrations. These observations revealed that the strong phenyls interactions contributed significantly to sorb the aqueous soluble aromatic contaminants to 65BTMA (>90%), and which favored to design uniquely powerful sorbents.     

Study on particulates and volatile organic compounds removal with TiO2 nonwoven filter prepared by electrospinning

In this study, polyvinyl alcohol (PVA) and titania (TiO₂) Degussa P-25 were mixed to generate TiO₂ nonwoven filters using electrospinning. The wires of titanium dioxide and the nonwoven binding titania nanofibers were formed using 14 kV voltage and a distance of 15 cm. A single-factor experimental method was used to investigate the effects of parameters such as initial concentration, retention time, and light source on acetone removal by nonwoven binding titania nanofibers. Furthermore, the effects of parameters such as gas pressure, particle size, initial concentration, and retention time on the removal of particulates were also assessed. The results showed that the degradation efficiency increased with decreasing initial concentrations and increasing retention time. The best operational conditions during this study for the removal of acetone using the TiO₂ nonwoven filters were a retention time of 100 sec, initial acetone concentration of 250 ppm, and ultraviolet (UV) light source of 254 nm. Under those conditions, 99% acetone removal efficiency was obtained. In addition, 90% particulate matter removal efficiency was reached when the particulate size was greater than 200 nm and the reaction time was longer than 5 minutes. The prepared TiO₂/nanofiber has good performance for volatile organic compounds (VOCs) and particulate removal at the same time.

Implications: In this study, polyvinyl alcohol (PVA) and titania (TiO₂) Degussa P-25 were mixed to generate TiO₂ nonwoven filters using electrospinning. The results showed that the optimum operating conditions for the removal of acetone using the TiO₂ nonwoven filters were a retention time of 100 sec, initial acetone concentration of 250 ppm, and UV light source of 254 nm. Under those conditions, 99% acetone removal efficiency was obtained.     

Simultaneous removal of nitrate and pentachlorophenol from simulated groundwater using a biodenitrification reactor packed with corncob

Both nitrate and pentachlorophenol (PCP) are familiar pollutants in aqueous environment. This research is focused on the simultaneous removal of nitrate and PCP from simulated contaminated groundwater using a laboratory-scale denitrification reactor packed with corncob as both carbon source and biofilm support. The reactor could be started up readily, and the removal efficiencies of nitrate and PCP reached up to approximately 98 % and 40–45 % when their initial concentrations were 50 mg N/L and 5 mg/L, respectively, after 15-day continuous operation at 10 h of hydraulic retention time (HRT) and 25 °C. Approximately 91 % of PCP removal efficiency was achieved, with 2.47 mg/L of chloride ion release at 24 h of HRT. Eighty-two percent of chlorine in PCP removed was ionized. The productions of 3-chlorophenol and phenol and chloride ion release indicate that the reductive dechlorination reaction is a major degradation pathway of PCP under the experimental conditions.     

Simultaneous removal of NO and SO2 by high-temperature fluidized zero-valent iron processes

A new approach to simultaneously remove nitrogen monoxide (NO) and sulfur dioxide (SO2) by zero valent iron (ZVI) was investigated. Three different parameters, temperature, flux, and ZVI dosage, were tested in fluidized ZVI column studies containing 500 ppmv of NO and SO2, respectively. Under the ZVI dosage of 0.5 g at flux of 0.6 L/cm2 x min for temperature 573 K, there is neither NO nor SO2 reduction. For 623 K and 673 K, complete removal for NO and > 90% removal for SO2 were achieved. For temperatures of 723 K and 773 K, 100% removal was achieved for both NO and SO2. The amounts of NO or SO2 reduction (as milligrams of NO or SO2 per gram ZVI) increased as temperature increased, and linearities were observed with both correlation coefficients > 0.97. Compared with NO, SO2 had earlier breakthrough because of a slower diffusion rate and less reactivity but higher mass reduction because of a higher molecular weight for SO2 (64 g/mol for SO2 and 30 g/mol for NO). At same temperature, both NO and SO2 reductions (as milligrams of NO or SO2 per gram of ZVI) were constant regardless of either flux or ZVI dosage variation, but breakthrough time was affected by both flux and ZVI dosage. A parameter weight of ZVI/flux (W/F) was developed to represent these two parameters at the same time to assess the breakthrough time of NO and SO2. Higher breakthrough time was achieved for higher W/F value. Moreover, interestingly, longer breakthrough time and more NO and SO2 mass reduction were achieved for combined NO and SO2 than individual NO or SO2 treated by ZVI, and both oxidation and reduction reactions occurred instead of a reduction reaction only. Chemical reactions among ZVI/NO, ZVI/ SO2, and ZVI/NO/SO2 were also proposed and verified by X-ray diffraction analyses.     

Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study

Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity.     

In situ studies on growth,oxidative stress responses,and gene expression of juvenile bighead carp (Hypophthalmichthys nobilis) to eutrophic lake water dominated by cyanobacterial blooms

Cyanobacterial blooms have received increasing attention as a public biohazard for human and animal health. To assess the effect of cyanobacteria-dominant lake water on juvenile fish, we measured the responses of specific growth rate, condition factor, body weight and body length, oxidative stress, and related gene expression of juvenile bighead carp Hypophthalmichthys nobilis exposed to in situ eutrophic lake (Chl a was around 7.0 μg L⁻¹). Results showed in situ cyanobacteria-dominant lake water had no effect on the growth performance, but significantly elevated the contents of malondialdehyde, the expression of heat shock protein 70, and the activity of superoxide dismutase, indicating that oxidative stress occurred. Meanwhile in situ lake water significantly decreased the expression of catalase and glutathione S-transferase genes. We conclude that in situ cyanobacteria-dominated lake water was harmful to juvenile bighead carp based on the oxidative stress and changes in the related gene expression levels.