饮用水供水过程中藻类及其代谢产物的去除与再生长控制

饮用水源富营养化导致的藻类大量繁殖及藻类代谢物分泌对饮用水质安全造成严重影响,本文以水质安全多级屏障控制与保障的角度,系统总结了饮用水处理、输配与二次供水过程去除与控制藻细胞及其代谢产物的工艺方法。其中,藻细胞灭活、凝聚与絮凝、固液分离（沉淀或气浮）及过滤分离等工艺过程是去除饮用水中藻细胞的主要单元;吸附、氧化等是控制藻细胞代谢产物（藻毒素、geosmin与2-MIB等致嗅微量有机物等）的关键工艺;对于输配与二次供水过程中,对供水系统进行优化设计并提高科学管理水平,这是最为可行的避免藻类生长的途径。在饮用水处理与输配过程以及建筑给水工程中应尽可能去除藻及其代谢产物,并控制由此产生的水质安全风险,从根本上保障饮用水质安全。     

结合孔隙结构分析注水对煤体瓦斯解吸的影响

 为了研究煤体瓦斯的解吸特性受高压注水影响的机制,结合压汞试验测定的煤的沟通孔隙率和孔径分布规律以及煤样注水后水残留在煤样中的质量,对不同煤种一定吸附瓦斯压力在注入不同压力水的条件下,煤体瓦斯解吸规律的差异进行分析。结果表明：(1) 不同煤种在同等吸附瓦斯压力条件下,沟通孔隙率越大,煤体瓦斯解吸能力越强;(2) 相同煤种煤体瓦斯的解吸能力与吸附瓦斯压力大小有关,吸附压力越大,解吸能力越强;(3) 根据煤的孔径分布规律和注水后煤中水的含量,计算出不同注水压力下水进入到煤体的临界孔隙尺度,该值直接影响煤体瓦斯的解吸能力,即临界孔隙尺度越小,解吸率越低;(4) 通过数据拟合得出煤体瓦斯的解吸率与水进入到煤体的临界孔隙尺度符合Langmuir型规律的函数关系式。     

沈北新区溪泉湖湿地三氮吸附特征研究

针对沈阳市沈北新区溪泉湖湿地水污染问题,开展了该湿地三氮(氨氮、硝态氮和亚硝态氮)的吸附降解试验,考察了三氮的吸附降解规律.通过测定植物生长期和非生长期土壤及植物对三氮的去除率,分析了湿地土壤和植物对三氮的吸附降解规律,利用一级反应速率方程计算两个生长期的平均吸附降解系数.结果表明,土壤和植物对三氮具有一定的吸附容量,吸附达到饱和后,吸附与解吸达到动态平衡,可为充分发挥湿地的生态功能以及保障溪泉湖地下水储备水源地的安全性提供参考.     

控制饮用水原水中藻类、藻毒素的水厂处理工艺

介绍了国内外对原水中藻类、藻毒素的去除方法,其中对藻类及其胞内藻毒素的去除主要有预过滤、强化混凝、气浮等技术,对细胞外溶解性藻毒素的去除主要有生物预处理、活性炭吸附、膜过滤、臭氧及紫外线等高级氧化工艺。通过分析这些工艺的优缺点及研究进展,提出了一些可行性优化组合方案并展望了可能的发展方向。     

阳澄湖水源地藻类的季节性分布特征

对2017年1月—11月阳澄湖水体中的藻类进行监测,分析了藻类总数以及优势种群、种属的季节性分布特征。结果表明,阳澄湖四季的优势藻类主要为硅藻、蓝藻、绿藻。绿藻是阳澄湖冬季(1月—2月)的优势藻种,占藻类总数的40. 3%,其优势种属是新月藻属和丝藻属。硅藻是阳澄湖春季(3月—5月)的优势藻种,占藻类总数的53. 9%,优势种属是小环藻属、直链藻属、针杆藻属,但每个月份的优势种属有所差异。夏、秋季,暴发蓝藻水华,蓝藻成为阳澄湖的优势藻类,7月份其占到藻类总数的83. 3%; 11月份时蓝藻数量已大量减少,硅藻、绿藻、蓝藻数量相当,藻类总数降至305×10~4个/L。秋、冬季藻类形态分布范围广,各种藻数量相差不大。水温是影响藻类种群季节性变化的重要因素之一。     

景观水体附植藻类群落变化及与环境因子的关系

为了解秋冬季节景观水体附植藻类与环境因子的关系，以重庆市典型人工景观水体为研究对象，对秋冬季（2019年9月—2020年1月）该景观水体沉水植物上附植藻类生物量、物种组成及其环境因子进行分析。结果表明，10月中旬为景观水体附植藻类秋季暴发高峰，1月为冬季暴发高峰且生物量为秋季峰值的1.9倍。景观水体4个采样点在采样期间共鉴定出附植藻类4门21属，其中硅藻门9属、绿藻门7属、蓝藻门4属、裸藻门1属。秋季采集到附植藻类3门14属，冬季采集到附植藻类4门16属。秋季常见的附植藻类有4属，分别为颤藻（Oscillatoria sp.）、针杆藻（Synedra sp.）、曲壳藻（Achnanthes sp.）、异极藻（Gomphonema sp.）；冬季常见的附植藻类有2属，为颤藻（Oscillatoria sp.）、曲壳藻（Achnanthes sp.）。多元回归分析结果表明，对于重庆典型景观水体，影响秋冬两季附植藻类生物量的主要环境因子为pH和总氮。秋季影响附植藻类生物量的主要环境因子为水温和氨氮，冬季为照度、总氮和水温。秋冬季节影响附植藻类的环境因子具有差异。上述结果表明，秋冬季节景观水体...     

次氯酸钠对微囊藻毒素释放及降解特性的研究

选用铜绿微囊藻为处理对象,研究了NaClO在藻类处理过程中藻毒素释放和降解的特性。结果表明：NaClO作用于藻细胞后会破坏其完整性,导致藻毒素释放,同时次氯酸钠投加量及藻浓度对藻毒素释放及降解量有较大影响。应避免在藻类大量暴发时（藻浓度〉6．96×10^6个／mL）预氧化中使用次氯酸钠,而在一般藻细胞浓度较低的水厂采用该种预氧化方法除藻,不会造成藻毒素的释放扩散。     

CO_2在页岩中的吸附解吸性能评价

利用自主设计的页岩中气体吸附解吸实验装置,在不同温度和压力条件下研究CO2在不同页岩中的吸附解吸性能。结果表明:CO2在页岩上的等温吸附曲线属于典型的Ⅰ型等温曲线,可采用Langmuir模型对吸附及解吸数据进行拟合;相同温度下,CO2在页岩中的吸附量随着压力的升高而增大;相同压力下,CO2在页岩中的吸附量随着温度的升高而减小;相同温度压力条件下,CO2解吸过程中存在解吸滞后现象,且解吸附曲线表征的最大吸附能力低于吸附曲线表征的最大吸附能力;CO2在页岩上最大吸附量随有机碳含量增加而增大,随石英含量增加而减小。     

常规水处理工艺应对高藻原水去除效果研究

针对滦河水藻类高发问题,研究了常规水处理工艺对滦河原水不同藻细胞密度的处理能力。结果表明,在保证出厂水水质情况下,常规水处理工艺对引滦原水藻类的处理极限为6 000×10~4个/L,最后提出了提高水厂常规水处理工艺除藻效果的建议。     

活性污泥中提取的藻酸作为铜吸附剂的研究

采用实验室培养的活性污泥提取藻酸并制备藻酸钙吸附剂,用于去除污水中的Cu2+,考察了其吸附和解吸性能及影响因素,并采用城市污水处理厂的剩余污泥进行验证.结果表明:pH值和藻酸钙投量对其吸附Cu2+有明显影响,当pH值为4、Cu2+初始浓度为100 mg/L、藻酸钙投量为0.7 g/L时,对Cu2+的平衡吸附量为41.96 mg/g;藻酸钙对Cu2+的吸附过程符合Langmuir模型;以盐酸为解吸剂,藻酸钙的解吸率可达到90%.实际剩余污泥可制备(203±11)mg/g的藻酸钙,对Cu2+的吸附量可达51.44 mg/g,而解吸率可达到94%.采用剩余污泥制备藻酸钙吸附剂,操作简单、成本低、对Cu2+的吸附高效、易于再生,具有工业应用前景.     

Chamber testing of adsorption of volatile organic compounds (VOCs) on material surfaces

A simple test chamber method to quantify adsorption and desorption of organic compounds on material surfaces is described. Important environmental parameters such as temperature, relative humidity and air velocity were varied and controlled independently around typical indoor values. Experiments were performed with alpha-pinene and toluene in concentrations of 160-300 micrograms/m3. The measurements show adsorption on and desorption from wool carpet, nylon carpet, polyvinyl chloride (PVC) floor coverings, cotton curtain material and the empty chamber. The ranking of the materials, with respect to their sorption capacity, is as mentioned above. The adsorption of alpha-pinene was higher than the adsorption of toluene for all the materials. Air velocity was not found to influence the sorption of alpha-pinene and toluene on wool carpet, tested with air velocities at 0, 10 and 20 cm/s. The experiments were carried out during both the adsorption and the desorption phase. The uncertainty of the experiments was lowest during the desorption phase. Based on the results obtained, it can be recommended that sorption experiments should be performed as desorption phase experiments. A one-sink model, based on the Langmuir adsorption isotherm, appears adequate to describe the results.     

The adsorption kinetics of metal ions onto different microalgae and siliceous earth

In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.21 h-1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g-1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.     

Effects of copper, zinc and cadmium on Selanastrum Capricornutum

The algicidal and algistatic effects of copper, zinc and cadmium on Selanastrum capricornutum, a unicellular green algae were analyzed by using a modification of the Algal Assay Procedures Bottle Test.Algicidal concentrations of copper, zinc and cadmium were 0.30, 0.70, and 0.65 mg 1⁻¹. Treatment of Selanastrum with various concentrations of the metals resulted in similar growth rates characterized by extended lag growth phases.Combinations of copper, zinc and cadmium were similar in toxicity to equal concentrations of zinc. Combinations of copper and cadmium resulted in a greater growth rate than equal concentrations of copper suggesting that cadmium inhibits copper toxicity.Selanastrum was able to exist in waters from the upper South Fork and North Fork of the Coeur d'Alene River where zinc and other metals were in low concentration. However, the algae was not able to tolerate zinc concentrations greater than 0·5 mg 1⁻¹ from waters of other parts of the drainage. These observations were consistent with laboratory findings where 0.7 mg 1⁻¹ zinc was algicidal and 0.1 mg 1⁻¹ inhibited the growth of Selanastrum.     

Sensitivity of marine microalgae to copper: the effect of biotic factors on copper adsorption and toxicity

Microalgae are sensitive indicators of environmental change and, as the basis of most freshwater and marine ecosystems, are widely used in the assessment of risk and development of environmental regulations for metals. However, interspecies differences in sensitivity to metals are not well understood. The relationship between metal-algal cell binding and copper sensitivity of marine microalgae was investigated using a series of 72-h growth-rate inhibition bioassays and short-term (1-h) uptake studies. A range of marine algae from different taxonomic groups were screened to determine whether copper adsorption to the cell membrane was influenced by biotic factors, such as the ultrastructure of cell walls and cell size. Minutocellus polymorphus was the most sensitive species to copper and Dunaliella tertiolecta the least sensitive, with 72-h IC50 values (concentration to inhibit growth-rate by 50%) of 0.6 and 530 microg Cu/L, respectively. Copper solution-cell partition coefficients at equilibrium (K(d)) were calculated for six species of algae on a per cell and surface area basis. The largest and smallest cells had the lowest and highest K(d) values, respectively (on a surface area basis), with a general (non-linear) trend of decreasing K(d) with increasing cell surface area (p=0.026), however, no relationship was found between K(d) and copper sensitivity, nor cell size and copper sensitivity. Interspecies differences in copper sensitivity were not related to cell size, cell wall type, taxonomic group or K(d) values. The differences in sensitivity may be due to differences in uptake rates across the plasma membrane, in internal binding mechanisms and/or detoxification mechanisms between the different microalgal species.     

Algae as a chemical speciation monitor—I A comparison of algal growth and computer calculated speciation

An alga, Selenastrum capricornutum, was used to monitor the relationship between metal speciation and toxicity. The principal effect of copper on the algae was a decrease in growth rate constant as the total concentration of copper increased. A 24-h growth experiment was used to monitor the effect of metal on the algae. Chlorophyll measurements at 17 and 23 h were used to estimate the growth rate constant. A plot of growth rate constant versus the speciation variable (total copper, pCu, pCuL, etc.) was used to determine the toxic species and the algicidal concentrations. Solutions containing EDTA, TRIEN, NTA, HIMDA and bicine became algicidal at pCu of 8.0 whereas solutions containing ethylenediamine and citric acid became algicidal at pCu 8.65 and 9.5, respectively. A comparison of growth and calculated speciation suggests that Cu en⁺² and Cu CIT OH⁻² were toxic species.     

Adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel sulfate and zinc nitrate by river surface sediments

An investigation into the adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel nitrate and zinc nitrate by river sediments was carried out using either a flow-through system or a semi-static system. The material balance in the sediment compartment could be explained by the equation, dCs/dT= K1Cw-K2Cs. The adsorption rate constants (K1), desorption rate constants (K2) and concentration factors (K1/K2) were calculated. For hydrophobic chemicals, the K1's were independent of water solubility, but the K2's were relatively related to water solubility. For both hydrophobic chemicals and heavy metals, the concentration factors per fraction organic carbon were similar to the soil sorption coefficients (Koc), expressed on a organic carbon basis.     

Impact of pH on the adsorption and desorption kinetics of 2-nitrophenol on activated carbons

The adsorption and desorption kinetics of 2-nitrophenol (2NP) from aqueous solutions using F-400 and WV-B granular activated carbons (GAC) have been studied at pHs 1, 4.6 and 13, using batch tests. Adsorption and desorption kinetics of 2NP on to both carbons were adequately described by the homogeneous solid surface diffusion model (HSSD). The adsorption and desorption kinetics can be predicted at different pHs by using adsorption kinetics parameters of the pH 4.6 and the isotherm parameters for the corresponding pH. Thus, the differences in the rates of adsorption are primarily attributable to the differences in the equilibrium loadings at the various pHs.     

Treatment of naphthalene-2-sulfonic acid from tannery wastewater by a granular activated carbon fixed bed inoculated with bacterial isolates Arthrobacter globiformis and Comamonas testosteroni

The kinetics of naphthalene-2-sulfonic acid (2-NSA) adsorption by granular activated carbon (GAC) were measured and the relationships between adsorption, desorption, bioavailability and biodegradation assessed. The conventional Langmuir model fitted the experimental sorption isotherm data and introduced 2-NSA degrading bacteria, established on the surface of the GAC, did not interfere with adsorption. The potential value of GAC as a microbial support in the aerobic degradation of 2-NSA by Arthrobacter globiformis and Comamonas testosteroni was investigated. Using both virgin and microbially colonised GAC, adsorption removed 2-NSA from the liquid phase up to its saturation capacity of 140 mg/g GAC within 48 h. However, between 83.2% and 93.3% of the adsorbed 2-NSA was bioavailable to both bacterial species as a source of carbon for growth. In comparison to the non-inoculated GAC, the combination of rapid adsorption and biodegradation increased the amount (by 70-93%) of 2-NSA removal from the influent phase as well as the bed-life of the GAC (from 40 to >120 d). A microbially conditioned GAC fixed-bed reactor containing 15 g GAC removed 100% 2-NSA (100 mg/l) from tannery wastewater at an empty bed contact time of 22 min for a minimum of 120 d without the need for GAC reconditioning or replacement. This suggests that small volume GAC bioreactors could be used for tannery wastewater recycling.     

Derivation and application of a new model for heavy metal biosorption by algae

An equilibrium model for describing the relationships between important parameters for heavy metal sorption by algae was derived through a thermodynamics approach. In this model, both the removal efficiency of heavy metal and metal adsorption per unit algal biomass are considered to be simple functions of the ratio of algal biomass concentration to the initial metal concentration for selected conditions, i.e. as at constant pH and temperature. The model was found to fit the experimental results well (judged by the correlation-regression coefficient, R2), for the adsorption of cadmium, copper, lead and zinc by two algal species, Oocystis sp. (both living and non-living) and Chlorococcum sp. The applicability of the model was also supported by the reprocessed results of experimental data given in the literature, i.e. for the metal species, Cd, Pb, Cu and Ag, the algal species, Chlorella vulgaris, Scenedesmus quadricauda and Cladophora crispata, and both batch and continuous fixed-bed reactors. It was also demonstrated that the model could be applied over a broad range of pH for cadmium and copper adsorption by Oocystis sp. However, the model was not applicable at very low and high pH levels, due to negligible adsorption and precipitation, respectively.     

A study on arsenic adsorption on polymetallic sea nodule in aqueous medium

A detailed study on As(III) and As(V) adsorption on polymetallic sea nodule in aqueous medium has been reported. Elemental composition of sea nodule comprises primarily, iron, manganese and silicon with trace quantities of aluminium, copper, cobalt and nickel. As(V) adsorption on sea nodule is dependent on pH while As(III) is insensitive to it. Adsorption data broadly follow Langmuir isotherm. Kinetic data follow a pseudo-second-order model for both As(III) and As(V). Arsenic loading on sea nodule is dependent on initial arsenic concentration. Optimum As(III) loading is 0.74 mg/g at 0.34 mg/L and for As(V) it is 0.74 mg/g at 0.78mg/L. As(III) adsorption is broadly independent of ionic environment. Except for PO(4)(3-), As(III) adsorption is not influenced by anions but cations influence it significantly. As(V) adsorption, on the other hand, is influenced by anions and not by cations. Experimental evidence indicates an inner sphere complex for As(III) and partial inner and partial outer sphere complex for As(V). Both As(III) and As(V) adsorptions are marked with very little desorption in the pH range of 2-10. Sea nodule can speciate As(III) and As(V) in groundwater at or above pH 6. Sea nodule was successfully tested as an adsorbent for the removal of arsenic from six contaminated groundwater samples of West Bengal, India, containing arsenic in the range 0.04-0.18mg/L.