Removal of a cationic dye from aqueous solutions by adsorption onto bentonite clay

The ability of bentonite to remove malachite green from aqueous solutions has been studied for different adsorbate concentrations by varying the amount of adsorbent, temperature, pH and shaking time. Maximum adsorption of the dye, i.e. >90% has been achieved in aqueous solutions using 0.05 g of bentonite at a pH of 9. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were calculated from the slope and intercept of the linear plots of ln K_D against 1/T. Analysis of adsorption results obtained at 298, 308, 318 and 328 K showed that the adsorption pattern on bentonite seems to follow the Langmuir, Freundlih and D–R isotherms. The temperature increase reduces adsorption capacity by bentonite, due to the enhancement of the desorption step in the mechanism. The numerical values of sorption free energy (E_a) of 1.00–1.12 kJ mol⁻¹ indicated physical adsorption. The kinetic data indicated an intraparticle diffusion process with sorption being first order. The rate constant k was 0.526 min⁻¹. The concentration of malachite green oxalate was measured before and after adsorption by using UV–Vis spectrophotometer.     

Occurrences of pharmaceutical and personal care products as micropollutants in rivers from Romania

The occurrence of pharmaceutical and personal care products (PPCPs) was investigated in the Somes River. The aim of this study was to obtain a first overview about the contamination of Somes River (Transylvania) with PPCPs. The samples were preconcentrated by Solid Phase Extraction (SPE) procedures and analysed by GC/MS. A number of 15 compounds including pharmaceutics, metabolites, intermediates and musk fragrances were detected in concentration ranging from 30 ng/l to 10 μg/l. The detected pharmaceuticals are included in following therapeutic groups: analgesics, antiepileptics, psychiatric, stimulants, anticoagulants, antineoplastic and disinfectants.     

南淝河沉积物可转化态氮赋存形态及其对上覆水水质的影响

为了探讨黑臭河道沉积物可转化态氮（TF-N）的赋存对上覆水的影响,以典型黑臭水体——南淝河为研究对象,采用连续提取的方法将沉积物中可转化态氮分为离子交换态氮（IEF-N）、弱酸浸提态氮（WAEF-N）、强碱浸提态氮（SAEF-N）和强氧化剂浸提态氮（SOEF-N）,研究南淝河沉积物中可转化态氮形态受排口类型和沉积物理化性质的影响规律,及其与上覆水氮素含量之间的关系。结果表明：南淝河沉积物可转化态氮以TF-NO3--N为主,占TF-N的88.57%±6.13%,而TF-NH4+-N仅占TF-N的11.43%±6.13%;从赋存形态的角度看,南淝河沉积物中SOEF-N相对含量最高（57.48%±3.67%）,WAEF-N次之（26.16%±3.10%）,SAEF-N和IEF-N较少,其相对含量分别为10.30%±4.85%和6.05%±1.73%;沉积物中TF-NH4+-N含量受排口类型的影响较为敏感,且4种赋存形态氮含量受排口类型影响的规律各不相同。另外,pH值和有机质含量对IEF-N影响较大,而CEC影响着WAEF-N含量。上覆水中溶解有机氮（dissolved organic nitrogen,DON）含量与沉积物IEF-N含量之间的显著相关（P4+-N赋存含量越多,释放到上覆水体的可能性越大。研究结果表明黑臭水体是一个复杂的生态系统,调控沉积物可转化态氮形态给黑臭水体内源污染控制提供新思路。     

陶粒生物滤池低温处理黄河水研究

进行了利用陶粒生物滤池工艺低温生物预处理黄河微污染水的研究,结果表明,温度的降低对陶粒生物滤池去除CODMn、UV254和氨氮的影响不明显,其平均去除率分别为11%、22.2%和61.2%。水温低于5℃时出水中亚硝酸氮浓度升高。此外,低水温条件下陶粒上生物膜脱氢酶活性仍然较高。     

Anaerobic degradation of diethyl phthalate, di-n-butyl phthalate, and di-(2-ethylhexyl) phthalate from river sediment in Taiwan

We investigated anaerobic degradation rates for three phthalate esters (PAEs), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), and di-(2-ethylhexyl) phthalate (DEHP), from river sediment in Taiwan. The respective anaerobic degradation rate constants for DEP, DBP, and DEHP were observed as 0.045, 0.074, and 0.027 1/day, with respective half-lives of 15.4, 9.4, and 25.7 days under optimal conditions of 30 °C and pH 7.0. Anaerobic degradation rates were enhanced by the addition of the surfactants brij 35 and triton N101 at a concentration of 1 critical micelle concentration (CMC), and by the addition of yeast extract. Degradation rates were inhibited by the addition of acetate, pyruvate, lactate, FeCl₃, MnO₂, NaCl, heavy metals, and nonylphenol. Our results indicate that methanogen, sulfate-reducing bacteria, and eubacteria are involved in the degradation of PAEs.     

Contaminated sediments and bioassay responses of three macroinvertebrates, the midge larva Chironomus riparius, the water louse Asellus aquaticus and the mayfly nymph Ephoron virgo

Bioassays are widely used to estimate ecological risks of contaminated sediments. We compared the results of three whole sediment bioassays, using the midge larva Chironomus riparius, the water louse Asellus aquaticus, and the mayfly nymph Ephoron virgo. We used sediments from sixteen locations in the Dutch Rhine-Meuse Delta that differed in level of contamination. Previously developed protocols for each bioassay were followed, which differed in sediment pretreatment, replication, and food availability. The Chironomus bioassay was conducted in situ, whereas the other two were conducted in the laboratory. The measured endpoints, survival and growth, were related to contaminant levels in the sediment and to food quantity in water and sediment.

Only the response of A. aquaticus in the bioassay was correlated with sediment contamination. Food availability in overlying water was much more important for C. riparius and E. virgo, thereby masking potential sediment contaminant effects. We conclude that growth of A. aquaticus was depressed by sediment contamination, whereas growth of E. virgo and C. riparius was stimulated by seston food quantity. We discuss that the trophic state of the ecosystem largely affects the ecological risks of contaminated sediments.     

Seasonal Fluctuation in Heavy Metal Pollution in Iran´s Siahroud River - A Preliminary Study (7 pp)

Background The management of its available water resources has become a key issue for Iran. During the last few decades, the water quality of Siahroud River in the coastal plain of the Caspian Sea in Gilan Province in Northern Iran has significantly degraded. The scarcity of water has been compounded by rapid population growth and increasing pollution from fertilizers, pesticides, and municipal and industrial wastes. One of the sources of this degradation is the movement of heavy metals from the river's watershed into the various water systems supported by the river, including the water system for Rasht City. Methods To study the magnitude of heavy metal pollution in the Siahroud River, seven heavy metals including Zn, Cu, Pb, Cd, Mn, Fe, and Ni were measured in duplicate from replicated water samples collected over five consecutive seasons and analyzed by Atomic Absorption Spectrometry. In situ measurements of pH were taken with the samples and total organic carbon (TOC) was analyzed by IR gas measurement. Results The results demonstrated that four of the seven heavy metals including Pb, Fe, Cd, and Mn exceeded permissible safe levels as established by the United States Environmental Protection Agency. Multivariate factor analysis suggested that industrial land-use was the main contributing factor for the high levels of Fe and Mn in the Siahroud River, whereas, Cd was principly from agricultural activities in the watershed. The data also suggested that pH and TOC had an important role in the behaviour of Pb and Mn, and that the elevated levels of these two heavy metals in Siahroud River was the consequence of other anthropogenic sources. Only negligible levels of Zn, Cu and Ni were detected. Finally, all the sampling stations were subjected to cluster analysis. The results indicated that three different zones could be distinguished according to the levels of pollution. In addition, it was shown that the urban areas did not have a significant impact on the heavy metal pollution in the river. This observation stems from the fact that the data from the sampling stations before and after Rasht City were not significantly different. Recommendation . Preventive measures need to be undertaken in the land-use systems and watersheds of the Siahroud River to reduce the pollution levels of Pb, Cd, Mn and Fe.     

活性炭吸附室内空气中挥发性有机化合物

活性炭吸附室内空气中挥发性有机化合物的１０％穿透时间与气相浓度及挥发性有机化合物的种类有关,通过对苯、甲苯和丙酮的实验研究,得出了由高浓度估算室内低浓度时炭床１０％穿透时间的经验公式ｔｂ,１＝ｔｂ,ｈ（Ｃ０,１／Ｃ０,ｈ）＾ａ,其中ａ值是与炭床性能及挥发性有机化合物种类有关的参数,可通过实验确定。     

改性粉煤灰及其处理废水的机理

应用正交设计的基本理论,研究了PDMDAAC(聚二甲基二烯丙基氯化铵)改性粉煤灰的最佳条件,并将改性粉煤灰用于模拟印染废水的处理,探索了改性粉煤灰处理废水的机理。结果表明,在原PDMDAAC的pH下．控制PDMDAAC的浓度为40g／L,恒温30℃．反应1h为最佳改性工艺,改性粉煤灰处理废水的机理以吸附电中和为主。     

改善深圳河水质的补水方案及生态影响初步分析

深圳河旱季天然径流量小而污染负荷高,为了改善河流水质,在削减入河污染物的同时有必要采取补水措施。利用水质模型,计算了不同污水处理率下,分别以污水资源化再生水、珠江口海水和大鹏湾海水为补水水源时,深圳河达到基本不黑臭所需的补水量。讨论了补水方案对河流水质、盐度、水动力条件的改变及其对生态系统的影响。研究表明,引海水对河流生态系统的冲击不容忽视。而污水资源化是较优的补水方案。