改性沸石耦合活性炭强化混凝处理微污染源水

采用静态吸附和六联搅拌烧杯实验进行组合改性沸石粉(MZ)耦合粉末活性炭(PAC)强化混凝去除微污染源水氨氮(NH3-N)、耗氧量(CODMn)、UV254和浊度等效能研究。结果表明,组合改性后沸石粉的比表面积和平均吸附孔径增加,对NH3-N交换去除能力增强。MZ和PAC联用吸附对去除NH3-N具有协同作用,对去除CODMn略有拮抗作用。而MZ耦合PAC强化混凝则显著提高了NH3-N,CODMn,UV254和浊度的去除效果,出水NH3-N<0.5 mg/L,CODMn<3.0 mg/L,浊度<1 NTU。MZ和PAC不同投加方式显著影响强化混凝处理效果,其中最佳投加方式为絮凝初期投加PAC和MZ,避免絮体包裹MZ,加强PAC对有机物的去除,进一步提高MZ对NH3-N的去除效果。耦合强化混凝使Zeta电位的绝对值降低,胶体间斥力减少,絮体粒径增大,粘黏现象明显,抗冲击能力更强。

Degradation and detoxification of microcystin-LR in drinking water by sequential use of UV and ozone

Microcystins (MCs) produced by cyanobacteria are strong hepatotoxins and classified as possible carcinogens.MCs pose a considerable threat to human health through tainted drinking and surface waters.Herein filtrated water from a waterworks in Harbin,China,was spiked with microcystin-LR (MC-LR) extracted from a toxic scum of microcystis aeruginosa,and the spiked sample waters were treated using UV irradiation with consequent ozonation process (UV/O3),compared with ozonation at a dose range commonly applied in water treatment plants,UV irradiation at 254 nm and UV irradiation combined with ozonation (UV+O3),respectively.The remaining of toxins were analyzed using high-performance liquid chromatography and also determined using a protein phosphatase type 2A inhibition assay,which was utilized to evaluate the reduction in toxicity.Results indicated that in comparison to other three processes (O3,UV,and UV+O3),UV/O 3 process could effectively decrease both the concentration and toxicity of MC-LR at 100 μg/L level after 5 min UV irradiation with consequent 5 min ozonation at 0.2 mg/L (below 1 μg/L),while 0.5 mg/L ozone dose was required for the level below 0.1 μg/L.The addition of an UV treatment step to the existing treatment train may induce significant transformation of micropollutants and breaks down the natural organic matters into moieties unfavorable for ozone decomposition,stabilizing the ozone residual.These findings suggested that sequential use of UV and ozone may be a suitable method for the removal of these potentially hazardous microcystins from drinking water.

Enhanced ozonation of dichloroacetic acid in aqueous solution using nanometer ZnO powders

Nanometer zinc oxide(ZnO) powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid(DCAA) in aqueous solution.The batch experiments were carried out to investigate the eflects of key factors such as catalyst dosage,ozone dosage,solution pH and tert-butyl alcohol(t-BuOH) on the degradation eflciency of DCAA.Density functional theory(DFT) was adopted to explore the mechanism of generating hydroxyl radical(.OH) on the ZnO surface.The results showed that adsorption and ozonation processes were not eflective for DCAA removal,and the addition of ZnO catalyst improved the degradation eflciency of DCAA during ozonation,which caused an increase of 22.8%for DCAA decomposition compared to the case of ozonation alone after 25 min.Under the same experimental conditions,the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L.The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93,6.88,and 10.With increasing the concentration of t-BuOH from 10 to 200 mg/L,the degradation of DCAA was significantly inhibited in the process of catalytic ozonation,indicating that ZnO catalytic ozonation followed.OH reaction mechanism.Based on the experimental results and DFT analysis,it is deduced that the generation of.OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface.It is also concluded that ZnO may be an eflective catalyst for DCAA removal,which could promote the formation of.OH derived from the catalytic decomposition of ozone.

Effect of nitrogen/phosphorus concentration on algal organic matter generation of the diatom Nitzschia palea:Total indicators and spectroscopic characterization

Critical algal blooms in great lakes increase the level of algal organic matters(AOMs),significantly altering the composition of natural organic matters(NOMs) in freshwater of lake.This study examined the AOM's characteristics of Nitzschia palea(N.palea),one kind of the predominant diatom and an important biomarker of water quality in the great lakes of China,to investigate the effect of AOMs on the variation of NOMs in lakes and the process of algal energy.Excitation–emission matrix fluorescence(EEM) spectroscopy,synchronous fluorescence(SF) spectroscopy and deconvolution UV–vis(D-UV) spectroscopy were utilized to characterize AOMs to study the effects of nutrient loading on the composition change of AOMs.From results,it was revealed that the phosphorus is the limiting factor for N.palea's growth and the generation of both total organic carbon and amino acids but the nitrogen is more important for the generation of carbohydrates and proteins.EEM spectra revealed differences in the composition of extracellular organic matter and intracellular organic matter.Regardless of the nitrogen and phosphorus concentrations,aromatic proteins and soluble microbial products were the main components,but the nitrogen concentration had a significant impact on their composition.The SF spectra were used to study the AOMs for the first time and identified that the protein-like substances were the major component of AOMs,creating as a result of aromatic group condensation.The D-UV spectra showed carboxylic acid and esters were the main functional groups in the EOMs,with –OCH_3,–SO_2NH_2,–CN,–NH_2,–O– and –COCH_3functional groups substituting into benzene rings.

Factors influencing the photodegradation of Nnitrosodimethylamine in drinking water

In order to provide basic data for practical application,photodegradation experiment of Nnitrosodimethylamine(NDMA)in aqueous solution was carried out with a low-pressure Hg lamp.Effects of the initial concentration of NDMA,solution pH,dissolved oxygen,and the presence of humic acid on NDMA photodegradation were investigated.NDMA at various initial concentrations selected in this study was almost completely photodegraded by UV irradiation within 20 min,except that at 1.07 mmol/L,NDMA could be photodegraded almost completely in the acidic and neutral solutions,while the removal efficiency decreased remarkably in the alkaline solution.Dissolved oxygen enhanced the NDMA photodegradation,and the presence of humic acid inhibited the degradation of NDMA.Depending on the initial concentration of NDMA,NDMA photodegradation by UV obeyed the pseudo-first-order kinetics.Dimethylamine,nitrite,and nitrate were detected as the photodegradation products of NDMA.^(1)O_(2) was found to be the reactive oxygen species present in the NDMA photodegradation process by UV,based on the inhibiting experiments using tert-butanol and sodium azide.