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.     

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.     

Decomposition of organochlorine compounds in flue gas from municipal solid waste incinerators using natural and activated acid clays

High-temperature particle control (HTPC) using a ceramic filter is a dust collection method without inefficient cooling and reheating of flue gas treatment; thus, its use is expected to improve the energy recovery efficiency of municipal solid waste incinerators (MSWIs). However, there are concerns regarding de novo synthesis and a decrease in the adsorptive removal efficiency of dioxins (DXNs) at approximately 300°C. In this study, the effect of natural and activated acid clays on the decomposition of monochlorobenzene (MCB), one of the organochlorine compounds in MSW flue gas, was investigated. From the results of MCB removal tests at 30–300°C, the clays were classified as adsorption, decomposition, and low removal types. More than half of the clays (four kinds of natural acid clays and two kinds of activated acid clays) were of the decomposition type. In addition, the presence of Cl atoms detached from MCB was confirmed by washing the clay used in the MCB removal test at 300°C. Activated acid clay was expected to have high dechlorination performance because of its proton-rich-composition, but only two clays were classed as decomposition type. Conversely, all the natural acid clays used in this work were of the decomposition type, which contained relatively higher di- and trivalent metal oxides such as Al₂O₃, Fe₂O₃, MgO, and CaO. These metal oxides might contribute to the catalytic dechlorination of MCB at 300°C. Therefore, natural and activated acid clays can be used as alternatives for activated carbon at 300°C to remove organochloride compounds such as DXNs. Their utilization is expected to mitigate the latent risks related to the adoption of HTPC, and also to contribute to the improvement of energy recovery efficiency of MSWI.

ImplicationsThe effect of natural and activated acid clays on MCB decomposition was investigated to evaluate their suitability as materials for the removal of organochlorine compounds, such as DXNs, from MSWI flue gas at approximately 300°C. More than half of the clays used in this study showed the decomposition characteristics of MCB. The presence of Cl atoms in the clay used in the MCB removal test at 300°C proved the occurrence of MCB decomposition. The results of this study suggest a novel flue gas treatment method to establish high-energy efficient MSWI systems.     

有机负荷对膜-生物反应器硝化性能的影响

采用厌氧动态膜-生物反应器(AnDMBR)组合自养膜-生物反应器(MBR)工艺,研究冬季低温条件下系统的硝化效果以及TP的去除效果,并与单级MBR工艺进行对比。结果表明:(1)AnDMBR对COD的去除率基本保持在50%～60%,AnDMBR组合自养MBR工艺对COD的去除率为80%～85%;单级MBR工艺对COD的去除率为80%左右。(2)总体上,AnDMBR组合自养MBR工艺对NH4+-N的去除率大于95%;单级MBR对NH4+-N的去除效果比AnDMBR组合自养MBR工艺差。(3)AnDMBR组合自养MBR工艺中,出水NO2--N与NO3--N均有积累;单级MBR工艺中,出水NO2--N积累不明显。(4)相对于亚硝酸盐氧化菌(NOB),氨氧化菌(AOB)对有机负荷更敏感,当有机负荷高时,AOB更易受到异养菌活动的抑制;当有机负荷降低、异养菌活性减弱时,AOB活性明显增强,系统的硝化效果得到明显改善。(5)AnDMBR组合自养MBR工艺对TP的去除率高于80%,单级MBR工艺稳定后对TP的去除率仅为20%～30%。(6)从呼吸速率和硝化速率可知,自养MBR的硝化效果优于单级MBR。     

Modelling the adsorption of mercury onto natural and aluminium pillared clays

Introduction

The removal of heavy metals by natural adsorbent has become one of the most attractive solutions for environmental remediation. Natural clay collected from the Late Cretaceous Aleg formation, Tunisia was used as a natural adsorbent for the removal of Hg(II) in aqueous system.

Methods

Physicochemical characterization of the adsorbent was carried out with the aid of various techniques, including chemical analysis, X-ray diffraction, Fourier transform infrared and scanning electron micrograph. Batch sorption technique was selected as an appropriate technique in the current study. Method parameters, including pH, temperature, initial metal concentration and contact time, were varied in order to quantitatively evaluate their effects on Hg(II) adsorption onto the original and pillared clay samples. Adsorption kinetic was studied by fitting the experimental results to the pseudo-first-order and pseudo-second-order kinetic models. The adsorption data were also simulated with Langmuir, Freundlich and Temkin isotherms.

Results

Results showed that the natural clay samples are mainly composed of silica, alumina, iron, calcium and magnesium oxides. The sorbents are mainly mesoporous materials with specific surface area of <250 m² g^?1. From the adsorption of Hg(II) studies, experimental data demonstrated a high degree of fitness to the pseudo-second-order kinetics with an equilibration time of 240 min. The equilibrium data showed the best model fit to Langmuir model with the maximum adsorption capacities of 9.70 and 49.75 mg g^?1 for the original and aluminium pillared clays, respectively. The maximum adsorption of Hg(II) on the aluminium pillared clay was observed to occur at pH 3.2. The calculated thermodynamic parameters (?G°, ?H° and ?S°) showed an exothermic adsorption process. The entropy values varied between 60.77 and 117.59 J?mol^?1 K^?1, and those of enthalpy ranged from 16.31 to 30.77 kJ mol^?1. The equilibrium parameter (R _L) indicated that the adsorption of Hg(II) on Tunisian smectitic clays was favourable under the experimental conditions of this study.

Conclusion

The clay of the Aleg formation, Tunisia was found to be an efficient adsorbent for Hg(II) removal in aqueous systems.     

Removal of nitric oxide in a biotrickling filter under thermophilic condition using Chelatococcus daeguensis

The development of a thermophilic biotrickling ?lter (BTF) system to inoculate a newly isolated strain of Chelatococcus daeguensis TAD1 for the effective treatment of nitric oxide (NO) is described. A bench-scale BTF was run under high concentrations of NO and 8% O₂ in thermophilic aerobic environment. A novel aerobic denitrifier Chelatococcus daeguensis TAD1 was isolated from the biofilm of an on-site biotrickling filter and it showed a denitrifying capability of 96.1% nitrate removal rate in a 24 h period in aerobic environment at 50 °C, with no nitrite accumulation. The inlet NO concentration fluctuated between approximately 133.9 and 669.6 mg m-3 and kept on a steady NOx removal rate above 80% in an oxygen stream of 8%. The BTF system was able to consistently remove 80–93.7% NO when the inlet NO was 535.7 mg m-3 in an oxygen stream of 2–20%. The biological removal efficiency of NO at 50 °C is higher than that at 25 °C, suggesting that the aerobic denitri?er TAD1 display well denitrification performance under thermophilic condition. Starvation for 2, 4 and 8 days resulted in the re-acclimation times of Chelatococcus daeguensis TAD1 ranging between 4 and 16 hours. A longer recovery time than that for weekend shutdown will be required when a longer starvation occurs. The results presented here demonstrate the feasibility of biotrickling ?lter for the thermophilic removal of NOx from gas streams.

Implications A novel denitrifier Chelatococcus daeguensis TAD1 was isolated from an on-site biotrickling filter in aerobic environment at 50 °C. To date, C. daeguensis has not been previously reported to be an aerobic denitrifier. In this study, a thermophilic biotrickling ?lter system inoculated with Chelatococcus daeguensis TAD1 for treatment of nitric oxide is developed. In coal-fired power plants, influent flue gas stream for nitrogen oxides (NO_x) removal typically exhibit temperatures between 50 and 60 °C. Traditionally, cooling gases to below 40 °C prior to biological treatment is inevitable, which is costly. Therefore, the application of thermophilic microorganisms for the removal of nitric oxide (NO) at this temperature range would offer great savings and would greatly extend the applicability of biofilters and biotrickling filters. Until now there has not been any study published about thermophilic biological treatment of NO under aerobic condition.     

Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil

A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg?kg^?1, the available Cd in the soil after the application of 1–10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg?kg^?1, the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg?kg^?1 fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg?kg^?1), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.     

Determination of Schulze equation for chemical oxygen demand reduction using stabilized landfill refuse media

Three columns each with 770 cm2 of surface area and 60-105 cm effective depth were set up for this study. These columns were filled with compacted, stabilized refuse. High-strength brewery wastewaters were uniformly trickled down the medium. Overall, 16 runs with various organic loadings were tested and the results demonstrated that the stabilized refuse had excellent capability in removing chemical oxygen demand (COD). The COD removal efficiency reached 95% at a depth of 60 cm at Q = 8 L/day for the initial COD of approximately 6000 mg/L and the efficiency increased to >99% at a depth of 90 cm (organic loading of 0.69 kg/m3/day). As would be expected, the filter performance is a function of flow rate, influent COD concentration, and bed depth. The Schulze equation is able to predict the COD removal performance well. The variations of pH, oxidation reduction potential, and volatile fatty acids indicated that the acidogenesis reaction occurred in the upper layers.     

Bioremoval of diethylketone by the synergistic combination of microorganisms and clays: uptake, removal and kinetic studies

The performance of two bacteria, Arthrobacter viscosus and Streptococcus equisimilis, and the effect of the interaction of these bacteria with four different clays on the retention of diethylketone were investigated in batch experiments. The uptake, the removal percentages and the kinetics of the processes were determined. S. equisimilis, by itself, had the best performance in terms of removal percentage, for all the initial diethylketone concentrations tested: 200, 350 and 700 mg/L. The uptake values are similar for both bacteria. A possible mechanism to explain the removal of diethylketone includes its degradation by bacteria, followed by the adsorption of the intermediates/sub-products by the functional groups present on the cells' surfaces. The assays performed with bacteria and clays indicated that the uptake values are similar despite of the clay used, for the same microorganism and mass of clay, but in general, higher values are reached when S. equisimilis is used, compared to A. viscosus. Kinetic data were described by pseudo-first- and pseudo-second-order models.     

Improved treatment approach for the removal of aromatic compounds using polymeric beads in Fenton pretreatment and biological oxidation

An improved approach based on the use of iron-doped polymeric beads (IPB) as Fenton catalyst in the pretreatment and biomass-doped polymeric bead (BPB) in the biological oxidation has been reported for the removal of different aromatic mixtures present as pollutants in the aqueous solutions. Degradation has been investigated at fixed loading of IPB as 2.5 % weight basis and varying loading of hydrogen peroxide so as to understand the effect of oxidant loading on the extent of degradation. It has been observed that the maximum removal efficiency as 75.5, 81.4, and 59.1 % was obtained for the benzene-toluene-naphthalene-xylene (BTNX), benzene-toluene-ethylbenzene-xylene (BTEX), and benzene-toluene-naphthalene-p-nitrophenol (BTNp-NP) mixtures, respectively, at a 40-min pretreatment and optimum pH of 3.5. The biodegradability index was also observed in the favorable range of 0.4 to 0.5 after the pretreatment at optimum H₂O₂ loading of 1.5 g L⁻¹. Maximum COD removal efficiency of 99.2, 99.3, and 99.6 % was obtained using the biological oxidation treatment for 40 h for the case of BTNX, BTEX, and BTNp-NP mixtures, respectively. Analysis of kinetic models revealed that degradation followed three distinct stages based on fitting of the three-stage model and BPB was found to be more efficient as compared to the primary activated sludge (PAS) and modified activated sludge (MAS). Reusability studies confirmed that both IPB and BPB were effective over many cycles giving stable performance during degradation without leaching of Fe³⁺ ions into the solution.

     

复合改性海泡石同步处理废水中的氮磷

采用盐热和稀土掺杂制备复合改性海泡石,研究了复合改性海泡石对废水中N、P的吸附特征和去除效果。结果表明,与海泡石原矿粉比较,复合改性海泡石的脱氮除磷能力分别提高49.71%和90.14%;复合改性海泡石对N、P的吸附可以用Langmuir吸附模型描述,获得的最大吸附量分别为1.165和1.121 mg/g;修正的Elovich模型能较好地描述复合改性海泡石吸附N、P的动力学过程;用NaOH溶液可以再生吸附材料,获得较好的脱氮除磷效果,再生次数以2次为宜;用复合改性海泡石处理污水处理站的二级生化出水,最终出水的pH、N和P含量均达到《城镇污水处理厂污染物排放标准》的要求。     

海泡石在废水处理中的应用研究

海泡石是一种纤维状含水的镁硅酸盐矿石 ,具有良好的吸附性能。纺织印染废水的组分异常复杂 ,是较难处理的废水之一。利用江西乐平产的海泡石对纺织印染废水进行了试验研究 ,实验结果表明 ,脱色率 >90 % ,CODCr去除率为70 %— 80 % ,其吸附容量为 30 7%。     

Municipal wastewater treatment using novel constructed soil filter system

The study gives a new approach for contaminant removal from municipal wastewater using constructed soil filter (CSF) and presents performance of two CSF units located in Mumbai, India. In this system, natural weathered rock is formulated which combines sedimentation, infiltration and biochemical processes to remove suspended solids and oxidisable organics and inorganics of the wastewater. Results show elevated dissolved oxygen (DO) levels, removal of COD (136-205 to 38-40 mg l(-1)) and BOD (80-125 to less than 12 mg l(-1)) suspended solids from 135-203 to 13-18 mg l(-1) and turbidity from 84-124 to 8-11 NTU, bacterial removal of 2.4-3.1 log order for Total coliform and Fecal coliform from site I which is almost 8 years old facility, and site II which is 3 years old. Estimated hydraulic retention time of 0.5-1.0 h, hydraulic loading of 0.036-0.047 m(3)m(-2)h(-1), no pretreatment, high DO levels in the effluent, no bio-sludge production, no mechanical aeration, low energy requirement (0.04 kW h m(-3)) and green aesthetic ambience are its unique features.     

好氧颗粒污泥自生动态膜生物反应器处理碱减量印染废水

自生动态膜生物反应器(SFDMBR)接种颗粒污泥启动,研究溶解氧浓度和水力停留时间对该反应器处理碱减量印染废水的影响。自生动态膜生物反应器形成稳定的动态膜后,出水浊度小于10 NTU,系统对浊度的去除率在90%以上,溶解氧和水力停留时间对反应器出水浊度基本无影响。系统对废水色度的去除率随着溶解氧浓度的提高和水力停留时间的延长而增加,但是系统对色度的去除效率一般不超过40%。溶解氧浓度由0.3 mg/L逐渐增大至2.4 mg/L,COD的去除率由40%提升至80%,而当溶解氧浓度大于1.0 mg/L后,UV254的去除率达到95%。水力停留时间在8~48 h时,COD去除效率由65%逐渐上升至85%左右;水力停留时间在8~32 h,UV254去除效率为68%~93%,超过32 h后水力停留时间对UV254去除效率的影响已不明显。     

负载IB族金属海泡石吸附NO性能的研究

采用浸渍法制备了负载IB族元素的系列金属基海泡石,用气相色谱等手段对制得的金属基海泡石对NO的吸附性能进行研究,并且对灼烧温度、金属负载量、分散度和压力等影响因素进行了讨论。实验结果表明,经过酸改性、负载金属后的海泡石对NO的吸附能力比原矿有很大的提高;选择出Cu/海泡石的最佳灼烧温度为300℃,最佳Cu负载量为5％;并证明在实验条件下Cu/海泡石上的NO吸附符合经验吸附等温式。     

Phytoremediation of 2,4-dichlorophenol using wild type and transgenic tobacco plants

Introduction

Transgenic plant strategies based on peroxidase expression or overexpression would be useful for phenolic compound removal since these enzymes play an important role in phenolic polymerizing reactions.

Material and methods

Thus, double transgenic (DT) plants for basic peroxidases were obtained and characterized in order to compare the tolerance and efficiency for 2,4-dichlorophenol (2,4-DCP) removal with WT and simple transgenic plants expressing TPX1 or TPX2 gene. Several DT plants showed the expression of both transgenes and proteins, as well as increased peroxidase activity.

Results

DT lines showed higher tolerance to 2,4-DCP at early stage of development since their germination index was higher than that of WT seedlings exposed to 25?mg/L of the pollutant. High 2,4-DCP removal efficiencies were found for WT tobacco plants. TPX1 transgenic plants and DT (line d) reached slightly higher removal efficiencies for 10?mg/L of 2,4-DCP than WT plants, while DT plants (line A) showed the highest removal efficiencies (98%). These plants showed an increase of 21% and 14% in 2,4-DCP removal efficiency for solutions containing 10 and 25?mg/L 2,4-DCP, respectively, compared with WT plants. In addition, an almost complete toxicity reduction of postremoval solutions using WT and DT plants was obtained through AMPHITOX test, which indicates that the 2,4-DCP degradation products would be similar for both plants.

Conclusion

These results are relevant in the field of phytoremediation application and, moreover, they highlight the safety of using DT tobacco plants because nontoxic products were formed after an efficient 2,4-DCP removal.     

Comparison of modified montmorillonite adsorbents. Part II: The effects of the type of raw clays and modification conditions on the adsorption performance

This paper builds on the preceding researches to study the effects of the type of clays (montmorillonites K10, KSF) and modifying conditions on the structure and adsorption behavior of resulting clay adsorbents. The raw clays were modified by polymeric Al/Fe species, hexadecyl-trimethylammonium (HDTMA) surfactant and a complex of polymeric Al/Fe-HDTMA. X-ray diffraction spectra was applied to analyze the structure of the raw and modified clays. After modification, the basal spacing of the clays varied, depending on the types of raw clay and modification conditions. Copper and phenol were selected as adsorbates for evaluating the adsorption performance of various clays, which was affected significantly by the types of raw clay and modification conditions. In general the inorganic contaminant (e.g., Cu) tend to be adsorbed by the polymeric Al/Fe modified clay and the organic impurities (e.g., phenol) will be preferably captured by the surfactant modified clay; both due to the specific surface properties resulting from introducing the modifiers. The complex modified clays possessed the ability of adsorbing both inorganic and organic contaminants. In addition, the d 0 0 1 spacing of modified KSF was greater than that of K10; the adsorption performance with modified KSF was thus greater than that with the modified K10. Finally, the ratio of modifiers to the clay (metal:surfactant:clay) has been observed to affect the adsorption performance; the optimal conditions have been defined.     

Kinetics of metribuzin release from bentonite-polymer composites in water

A series of bentonite polymer-composites (BPCs) loaded with metribuzin were studied for their controlled release in aqueous medium. The release of active ingredient from BPCs was significantly lower as compared to commercial metribuzin formulation. The results revealed that the cumulative metribuzin release was highest (81%) from the BPCs containing 8% clay (commercial bentonite) and 2% metribuzin which correspond to the lowest (14 days) half-life values i.e., time required for 50% release of active ingredient (t_1/2). The metribuzin release from the BPCs decreased with increased concentration of clays in polymer matrix and the release was further decreased with BPCs prepared with pure nano-bentonite. BPCs containing 12% clay and 2% metribuzin showed maximum t_1/2 values i.e., 25 and 51 days for commercial bentonite and pure nano-bentonite as clay sources, respectively. The differential behaviour in the metribuzin release rates from BPCs was ascribed due to variations in crosslinking of metribuzin in the composites. As metribuzin release was found to be slower in BPCs compared to commercial formulation, it could be used for control of weeds tailored to different crops.     

生物流化床及臭氧氧化处理中低浓度糖业废水

采用内循环好氧生物流化床对中低浓度糖业废水进行生物降解,当进水COD、NH3-N浓度分别为400～600mg/L和7～11 mg/L时,其相应去除率达到80%～90%和70%～80%,处理效果良好;COD容积负荷可达到5.1 kg COD/(m3·d),反应器具有较强的抗负荷冲击能力.采用臭氧氧化工艺对COD浓度为28...