造纸中段废水的混凝-臭氧氧化深度处理研究

就混凝-臭氧氧化组合工艺对造纸中段废水生物处理出水的净化效果进行了研究.结果表明,Ca(OH)2对废水色度、TOC、COD和254 nm的紫外吸收值(UV254)的去除效果均优于聚合氯化铝/聚丙烯酰胺(PAC/PAM);Ca(OH)2-O3组合工艺的处理效果也优于PAC/PAM-O3工艺.当Ca(OH)2投加量为1 g/L、臭氧投加量为50 mg/L时,废水色度降低至10倍以下,COD小于150 mg/L.经Ca(OH)2混凝处理后,相对分子量在0.5～1.0 ku和10.0 ku以上的有机物显著减少;进一步臭氧氧化处理后,除0.5 ～1.0 ku范围的有机物大幅度增加外,其余分子量有机物显著减少.由于对色度贡献很大的大分子量物质的去除,废水的色度显著下降直至无色.     

SMX degradation by ozonation and UV radiation: a kinetic study

The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV₂₅₄ radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV₂₅₄ radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8) × 10⁻³ and (1.7-18.9) × 10⁻³ s⁻¹, respectively. The second-order rate constants of SMX with ozone (k_O3), under varying operational parameters, were also determined and varied in the range of (0.60-3.38) ± 0.13 × 10⁵ M⁻¹ s⁻¹. In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.     

Studies on degradation of glyphosate by several oxidative chemical processes: Ozonation,photolysis and heterogeneous photocatalysis

Several different Advanced Oxidation Processes (AOPs) including ozonation at pH 6.5 and 10, photolysis and heterogeneous photocatalysis using TiO₂ as semiconductor and dissolved oxygen as electron acceptor were applied to study the degradation of glyphosate (N-phosphonomethyl glycine) in water. The degree of glyphosate degradation, the reactions kinetic and the formation of the major metabolite, aminomethyl phosphonic acid (AMPA), were evaluated. Ozonation at pH 10 resulted in the maximum mineralization of glyphosate. It was observed that under the experimental conditions used in this study the degradation of glyphosate followed the first-order kinetics. The half-life obtained for glyphosate degradation in the O₃/pH 10 process was 1.8 minutes.     

Transformation products and reaction kinetics of fragrances in advanced wastewater treatment with ozone

The reaction of the fragrance compounds 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta[g]isochromene (HHCB), 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone (AHTN), 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (musk xylene/MX), 1-(4-tert-butyl-2,6-dimethyl-3,5-dinitrophenyl)ethanone (musk ketone/MK), and 1-(2,3,8,8-tetramethyl-1,3,4,5,6,7-hexahydronaphthalen-2-yl)ethanone (OTNE) with ozone in tap water as well as waste water treatment plant (WWTP) effluents is described. Several transformation products are characterized by means of gas chromatography coupled to mass spectrometry. One transformation product (HHCB-Lactone) was confirmed by means of a true standard. Musk xylene and musk ketone do not react with ozone under the conditions used in this study. AHTN and HHCB reacted slowly to a multitude of transformation products, while OTNE reacted quickly to several stable transformation products. The reaction constants and half lives are used to predict removal efficiencies for full scale reactors.     

Removal of dissolved organic matter in municipal effluent with ozonation, slow sand filtration and nanofiltration as high quality pre-treatment option for artificial groundwater recharge

In the paper the combination process of ozonation, slow sand filtration (SSF) and nanofiltration (NF) was investigated with respect to dissolved organic matter (DOM) removal as high quality pre-treatment option for artificial groundwater recharge. With the help of ozonation leading to breakdown of the large organic molecules, SSF preferentially removes soluble microbial by-product-like substances and DOM with molecular weight (MW) less than 1.0 kDa. NF, however, removes aromatic, humic acid-like and fulvic acid-like substances efficiently and specially removes DOM with MW above 1.0 kDa. The residual DOM of the membrane permeate is dominated by small organics with MW 500 Da, which can be further reduced by the aquifer treatment, despite of the very low concentration. Consequently, the O₃/SSF/NF system offers a complementary process in DOM removal. Dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP) can be reduced from 6.5 ± 1.1 to 0.7 ± 0.3 mg L⁻¹ and from 267 ± 24 to 52 ± 6 μg L⁻¹, respectively. The very low DOC concentration of 0.6 ± 0.2 mg L⁻¹ and THMFP of 44 ± 4 μg L⁻¹ can be reached after the aquifer treatment.     

Degradation of phenol,Asulam and lignin in aqueous solution by Ozonation

Phenol, the herbicide asulam (methylsulfanilyl carbamate) and lignin were degraded by ozonation. The addition of Fe³⁺ did not affect the disappearance rates of phenol and asulam appreciably, whereas UV illumination accelerated the disappearance rate. Fe³⁺ under UV illumination showed only a slight effect on the disappearance rate, but a fairly large effect on TOC elimination. The degradation of the intermediate compounds of asulam including aromatic compounds and organic acids, under UV illumination was accelerated by the addition of Fe³⁺. A possible degradation process of asulam by ozonation was proposed on the basis of intermediate and final products identified.     

Oxidation and detoxification of pentachlorophenol in aqueous phase by ozonation

The degradation and detoxification performance of ozonation in treating pentachlorophenol (PCP) contaminated wastewater was determined. All experiments were conducted in a bench scale glass column equipped with ceramic diffuser and a lab-scale ozone generator under ambient temperature and pH 7. The decomposition rate of PCP in this study was primarily controlled by the ozone mass transfer rate from gas to liquid phases. Principal intermediates found were 2,3,4,6- and 2,3,5,6-tetrachlorophenols (TeCP) and phenol. PCP seems to be more vulnerable to ozone than its intermediates. A bioluminescence technique was used to evaluate the toxicity of PCP with Vibrio fisheri NRRL B-11177 as the test bacterium, and the EC(50) of PCP was found to be 1.0 mg l(-1). Detoxification occurred as the PCP and TeCP reacted with ozone and decomposed to less chlorinated congeners and phenol.     

The impact of preozonation on the coagulation of cellular organic matter produced by Microcystis aeruginosa and its toxin degradation

Ozonation pretreatment is typically implemented to improve algal cell coagulation. However, knowledge on the effect of ozonation on the characteristics and coagulation of associated algal organic matter, particularly cellular organic matter (COM), which is extensively released during algal bloom decay, is limited. Hence, this study aimed to elucidate the impact of ozonation applied before the coagulation of dissolved COM from the cyanobacteria Microcystis aeruginosa. Additionally, the degradation of microcystins (MCs) naturally present in the COM matrix was investigated. A range of ozone doses (0.1–1.0 mg O₃/mg of dissolved organic carbon – DOC) and ozonation pH values (pH 5, 7 and 9) were tested, while aluminium and ferric sulphate coagulants were used for subsequent coagulation. Despite negligible COM removal, ozonation itself eliminated MCs, and a lower ozone dose was required when performing ozonation at acidic or neutral pH (0.4 mg O₃/mg DOC at pH 5 and 7 compared to 0.8 mg O₃/mg DOC at pH 9). Enhanced MC degradation and a similar pattern of pH dependence were observed after preozonation-coagulation, whereas coagulation alone did not sufficiently remove MCs. In contrast to the benefits of MC depletion, preozonation using ≥ 0.4 mg O₃/mg DOC decreased the coagulation efficiency (from 42%/48% to 28%–38%/41%–44% using Al/Fe-based coagulants), which was more severe with increasing ozone dosage. Coagulation was also influenced by the preozonation pH, where pH 9 caused the lowest reduction in COM removal. The results indicate that ozonation efficiently removes MCs, but its employment before COM coagulation is disputable due to the deterioration of coagulation.