Removal Characteristics of Organic Pollutants in Sewage Treatment by a Pre-Coagulation,Ozonation and Ozone/Hydrogen Peroxide Process

The applicability of a sequential process of ozonation and ozone/hydrogen peroxide process for the removal of soluble organic compounds from a pre-coagulated municipal sewage was examined. 6–25% of initial T-COD_Cr was removed at the early stage of ozonation before the ratio of consumed ozone to removed T-COD_Cr dramatically increased. Until dissolved ozone was detected, 0.3 mgO₃/mgTOC₀ (Initial TOC) of ozone was consumed. When an ozone/hydrogen peroxide process was applied, additional COD_Cr was removed. And we elucidated that two following findings are important for the better performance of ozone/hydrogen peroxide process; those are to remove readily reactive organic compounds with ozone before the application of ozone/hydrogen peroxide process and to avoid the excess addition of hydrogen peroxide. Based on these two findings, we proposed a sequential process of ozonation and multi-stage ozone/hydrogen peroxide process and the appropriate addition of hydrogen peroxide. T-COD_Cr, TOC and ATU-BOD₅ were reduced to less than 7 mg/L, 6 mgC/L and 5 mg/L, respectively after total treatment time of 79 min. Furthermore, we discussed the transformation of organic compounds and the removal of organic compounds. The removal amount of COD_Cr and UV₂₅₄ had good linear relationship until the removal amounts of COD_Cr and UV₂₅₄ were 30 mg/L and 0.11 cm^?1, respectively. Therefore UV₂₅₄ would be useful for an indicator for COD_Cr removal at the beginning of the treatment. The accumulation of carboxylic acids (formic acid, acetic acid and oxalic acid) was observed. The ratio of carbon concentration of carboxylic acids to TOC remaining was getting higher and reached around 0.5 finally. Removal of TOC was observed with the accumulation of carboxylic acids. When unknown organic compounds (organic compounds except for carboxylic acids) were oxidized, 70% was apparently removed as carbon dioxide and 30% was accumulated as carboxylic acids. A portion of biodegradable organic compounds to whole organic compounds was enhanced as shown by the increase ratio of BOD/COD_Cr.     

Toxicity and Biodegradability Behavior of Xenobiotic Chemicals Before and After Ozonation: A Case Study with Commercial Textile Tannins

Ozonation of a natural tannin (NT; COD_o?=?1195 mg/L; TOC_o?=?342 mg/L; BOD_5,o?=?86 mg/L) and a synthetic tannin ST; COD_o?=?465 mg/L; TOC_o?=?55 mg/L; BOD_5,o?=?6 mg/L) being frequently applied in the polyamide dyeing process was investigated. Synthetic wastewater samples containing these tannins individually were prepared and subjected to ozonation at varying ozone doses (625– 1250 mgO₃/L wastewater), at pH?=?3.5 (the application pH of tannins) and pH?=?7.0 at an ozone dose of 1125 mgO₃/L wastewater. The collective environmental parameters COD, TOC, BOD₅, UV₂₅₄ and UV₂₈₀ (UV absorbance at 254 nm and 280 nm, representing aromatic and unsaturated moieties, respectively) were followed during ozonation. Changes in the biodegradability of the tannins were evaluated in terms of BOD₅ measurements conducted before and after ozonation. In addition, activated sludge inhibition tests employing heterotrophic biomass were run to elucidate the inhibitory effect of raw and ozonated textile tannins towards activated sludge biomass. Partial oxidation (45% COD removal at an ozone dose of 750 mg O₃/L wastewater and pH?=?3.5) of ST was sufficient to achieve elimination of its inhibitory effect towards heterotrophic biomass and acceptable biodegradability improvement, whereas the inhibitory effect and biodegradability of NT could not be reduced via ozonation under the same reaction conditions.     

Interaction of ozone and organic matter in coagulation with inorganic polymer flocculant-PACl: Role of organic components

In this study, two model waters were used to evaluate the ozone effect on aquatic organic matter (AOM) removal by coagulation with inorganic polymer flocculant (IPF)-polyaluminum chloride (PACl). Flocs formation during coagulation processes were detected by using PDA (Photometric Dispersion Analyzer). Apparent molecular weight distribution (AMWD) and resin fractionation (RF) were also performed to characterize the change of AOM as a result of pre-ozonation. The experimental results show that the dosage of O₃, characteristics and composition of AOM are the most important factors on the behavior of coagulation. Great differences have been found between the two model waters. Coagulation in model water 1 (MW1) (composed of humic acids) is impaired markedly by pre-ozonation, as more DOC (Dissolved Organic Carbon) is produced with increasing O₃ dosage. Floc formation, as exhibited from decreasing of the slopes of FI (Flocculation Index), is retarded gradually during coagulation process. Although residual turbidity is reduced with 1.15 mg/L O₃, removals of DOC and UV₂₅₄ all decreased. As for model water 2 (MW2) (composed of salicylic acid), FI is retarded also, but turbidity and DOC removals of coagulation after pre-ozonation are improved to a certain extent. Coagulation performance judged from removal of DOC is improved distinctly by pre-ozonation. Fractionation results show that molecular weight of organic matter (OM) of MW1 is converted from higher to lower; and OM becomes from more hydrophobic to more hydrophilic, which might be one of the mechanisms involved in the impairment of ozonation on coagulation effect. OM in MW2 is oxidized and mineralized to a greater extent, thus its impairment on coagulation is released. Finally, according to water properties, some proposed applications were provided for application of ozone in water treatment process.     

Removal of Residual Dissolved Ozone with Manganese Dioxide for Process Control with UV254

Ozonation is one of the most promising options to remove organic micropollutants (OMP) from wastewater treatment plant effluents. For an economic operation and in order to avoid formation of bromate, the ozone dose has to be adjusted in real-time due to the strongly varying effluent quality. The reduction of UV absorption at 254 nm (?UV₂₅₄) is a useful surrogate parameter for OMP removals. Unfortunately dissolved ozone also absorbs UV at 254 nm and therefore might disturb a ?UV₂₅₄-based process control. A fixed bed of manganese dioxide granules was found to efficiently remove residual ozone.     

Ozonation of Two Commercially Important Biocidal Finishing Agents

Ozonation of 2 commercially important textile biocidal finishing agents (called BI and BII herein) in aqueous solution was studied in a semi-batch bubble column reactor at different ozone feed rates (500, 750, and 900 mg/h) and pH (pH=7 and 12). Ozonation efficiency and kinetics were assessed in terms of COD, TOC and UV absorbance at 280 nm (UV₂₈₀) and 254 nm (UV₂₅₄), representing the aromaticity and unsaturated moieties of the studied textile biocides, respectively. Due to its chlorinated aromatic content, the fate of Adsorbable Organic Halogens (AOX) of BI was also followed during the ozonation experiments. At alkaline pH, appreciably higher COD and TOC removals were achieved, speaking for a free radical (^?OH) dominated degradation pathway for both tested biocides. AOX, UV₂₈₀ and TOC abatement rates obtained for BI ozonation at optimized reaction conditions indicated that the degradation of BI followed a sequential path of dechlorination, dearomatization, oxidation and mineralization, respectively.     

Degradation and Transformation of Organic Compounds in Songhua River Water by Catalytic Ozonation in the Presence of TiO2/Zeolite

This paper presents experimental results of the catalytic ozonation of Songhua River water in the presence of nano-TiO₂ supported on Zeolite. The removal efficiency of TOC and UV₂₅₄, the variation of AOC and molecular weight distribution of organics was studied. Results showed that TOC and UV₂₅₄ removal efficiency by ozone was improved in the presence of TiO₂/Zeolite, and increased by 20% and 25%, respectively. The part of organic compounds less than 1000 Da increased in ozonation, but decreased in catalytic ozonation. The AOC of water increased in catalytic ozonation, and the increase of AOC was particularly obvious when ozone dose increased from 28.8 mg·L^?1 to 46.6 mg·L^?1. The degradation and transformation of organic compounds was analyzed by means of GC-MS. The total number of organic compounds was reduced from 50 in the untreated water to 36 and 20, respectively, in ozonation and catalytic ozonation. The removal efficiency of the total organic compounds peak area in ozonation and catalytic ozonation were 23.5% and 62.5%, respectively. Most of the hydrocarbons could be removed easily in ozonation and catalytic ozonation. The organic compounds having hydroxyl, carboxyl or carbonyl groups were hard to be removed in ozonation, but could be removed efficiently in the presence of TiO₂/Zeolite.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Evaluation of Process Control Alternatives for the Inactivation of Escherichia coli,MS2 Bacteriophage,and Bacillus subtilis Spores during Wastewater Ozonation

Dissolved ozone concentration integrated over time (CT) is a reliable indicator of disinfection efficacy in drinking water treatment. However, ozone CT may not be measurable in some wastewater ozone applications. In this study, alternative process control parameters, specifically ozone to total organic carbon (O₃:TOC) ratio, differential UV₂₅₄ absorbance (ΔUV₂₅₄), and differential total fluorescence (ΔTF), were correlated with the inactivation of Escherichia coli, the bacteriophage MS2, and Bacillus subtilis spores in five secondary wastewater effluents. CT values greater than 9 mg-min/L were generally required for measurable inactivation of B. subtilis spores, and CT values of 1 and 2 mg-min/L consistently achieved greater than 6- and 5-log inactivation of MS2 and E. coli, respectively. The O₃:TOC, ΔUV_254, and ΔTF correlations for MS2 and B. subtilis were useful for predicting inactivation, while those of E. coli were characterized by greater variability. [Supplementary materials are available for this article. Go to the publisher's online edition of Ozone: Science & Engineering for the following free supplemental resources: additional figures and data tables.]     

Huangpu River water treatment by microfiltration with ozone pretreatment

With the promulgation of more stringent regulations to guarantee the quality of drinking water, low pressure membrane processes are nowadays considered for surface water treatment. But these membranes are sensitive to fouling. In this study ozone is introduced to pretreatment for membrane filtration to get a high quality permeate and improve membrane performance. The organic matter characteristics, such as AMWD of organic matter, hydrophilic/hydrophobic fractions were studied with ozone oxidation. Results show that for Huangpu River water, ozone oxidation offers high percentage of UV absorbance removal than DOC removal. Highest removal of DOC and UV₂₅₄ of 10% and 71% respectively were observed. The dominant organic matter oxidized by ozone was 2-7.0 kDa in terms of molecule distribution investigation. Ozone oxidizes more hydrophobic fraction to hydrophilic one. Changes of organic matter composition improved membrane flux. There is the optimal dosage with ozone of 1.5 mgO₃/L made membrane flux maximum during 0.5-3.0 mgO₃/L ozone dosage. Ozone oxidization provided degradation of macromolecule organic matter, which is responsible to membrane fouling, to small molecule organic substance. Study about the chemical cleaning of the fouled membrane also supports the point that membrane fouling is produced by the organic substance with high molecule weight.     

Effective Ozonation of Secondary Effluents with Initial Ozone Demand

It is clarified that the ozone consumption during the initial stage of ozonation before dissolved ozone appears is the same value as that during the initial 20 seconds in batch mode experiment. This initial ozone consumption was defined as initial ozone demand (IOD) in this study. IOD of secondary effluent was shown to be 0.3–0.5 mgO₃/mgC₀. More than 90% of 17β-estradiol (E2) was reduced, and formation of ozonation by-products was controlled within this ozone demand. This state can be also characterized by reduction of the values of UV₂₅₄, fluorescence intensity at 345 nm (Excitation)/435 nm (Emission) and that at 240 nm/435 nm to 0.06 /cm, 35 and 15, respectively.     

A Comparative Approach to the Application of a Physico‐Chemical and Advanced Oxidation Combined System to Natural Water Samples

Abstract

Natural organic matter removal (NOM) efficiencies of samples from three major drinking water sources (Elmali, Omerli, and Buyukcekmece) of Istanbul were compared using different treatment systems. Enhanced coagulation as a physico‐chemical method was applied using ferric chloride and aluminum sulphate as the coagulating agents. Moreover, the application of enhanced coagulation in combination with photocatalytic oxidation using TiO₂ was investigated. The efficiency of NOM removal relevant to each treatment step was assessed through DOC removal, UV₂₅₄ removal, and fluorescence measurements.

Irrespective of the treatment applied as enhanced coagulation, photocatalytic oxidation or their combinations, the highest removal efficiency was determined for Elmali followed by Omerli and Buyukcekmece samples both in terms of DOC and UV₂₅₄. Enhanced alum coagulation leads to significant variation in DOC removals as 44%, 28% and 26% for Elmali, Omerli, and Buyukcekmece water samples, respectively. Upon application of ferric chloride as the coagulant, the DOC removals achieved were found to be slightly higher as compared to alum. Moreover, the combined treatment incorporating photocatalytic oxidation subsequent to alum coagulation leads to 36%, 37%, and 50% of DOC removal for Omerli, Buyukcekmece, and Elmali respectively. The improvement of removal efficiencies in combined treatment systems were scrutinized with an emphasis on induced water properties as supported by the specific fluorescence intensities of the samples.     

Ozone,Electron Beam and Ozone-Electron Beam Degradation of Phenol. A Comparative Study

The efficacy of electron beam (EB), ozone (O₃) and the combined EB/O₃ treatment on the removal of phenol, as a prototype for aromatic pollutants in water, is compared on the base of degradation, chemical oxygen demand (COD), total organic carbon (TOC) and toxicity. Complete decomposition of phenol (47?mg/L, 500?µM) was obtained with 14?kGy. Applying simultaneously 27?mg O₃/L a dose of 10.5?kGy was sufficient. By the same amount of only ozone a phenol concentration of 45% remained. A TOC reduction of more than 70% was attained with EB/O₃ (21?kGy/54?mg O₃/L), whereas the identical, separate conditions solely led to 24% (EB) and 14% (O₃). The EB/O₃ treatment showed also the best results in COD decrease (79%, 21?kGy/54?mg O₃/L) and detoxification (7?kGy/18?mg O₃/L).     

The Effect Of Preozonation,Ozone/Hydrogen Peroxide Treatment,And Nanofiltration On The Removal Of Organic Matter From Drinking Water

Pilot scale experiments were performed to evaluate the ability of ozonation, ozone/hydrogen peroxide treatment and nanofiltration to reduce levels of organic matter, mutagenicity, total adsorbable halogens, color and turbidity from purified and bank-filtered surface water rich with humic material.

Ozonation and ozone/hydrogen peroxide decreased the amount of organic material from drinking water by about 20 percent measured as TOC and COD_Mn. Color and turbidity level reductions were 49 and 11 percent, respectively. Ozonation reduced the AOX concentrations formed during postchlorination from 150 μgL^?1 to 75 μgL^?1. The addition of hydrogen peroxide further improved the removal to 37 and 26 μgL^?1 depending on the ratio of H₂O₂/O₃. The mutagenicity reduction followed the same pattern: without ozonation the chlorination-derived mutagenicity was 1,450 net revertant L^?1 after the ozonation 700 and after the H₂O₂/O₃ treatment from <100 to 400 net revertant L^?1 depending on the H₂O₂/O₃ ratio. Nanofiltration appeared to be the most effective way to remove organic material. The removal of TOC was 68%, COD_M 72%, color 90%, turbidity 68%, AOX 88%, and mutagenicity 85%.     

水厂深度处理工艺中臭氧投加量探讨

臭氧生物活性炭深度处理是降低水中微量有机物的关键净化工艺。为确定臭氧的合理投加量,利用小试装置开展了臭氧氧化对砂滤池出水的研究。结果表明:随着臭氧投加量的增加,CODMn、总有机碳(TOC)的去除率均有所增加,但幅度弱于UV254;当臭氧的投加量达到3.0 mg/L时,臭氧氧化后的生物可降解溶解性有机碳(BDOC)可增加30%以上,UV254与TOC的比值趋于稳定;砂滤出水的溴离子浓度为100~300μg/L的情况下,当臭氧的投加量达到3.5 mg/L时仍未检测到溴酸盐。综上所述黄浦江原水水厂深度处理工程运行时,臭氧的投加剂量控制在2.5~3.5 mg/L是安全合理的。     

Application of microfiltration systems coupled with powdered activated carbon to river water treatment

A bench scale submerged microfiltration system coupled with high concentration of PAC (powdered activated carbon) was applied in order to purify a river water containing secondary effluent. The system was operated with four different modes: Run-1, -2, -3 and -4. The PAC concentration was set at 0, 4 and 40 g/L with same filtration rate of 1.0 m/d (42 L/m²/h) which correspond to Run-1, -2 and -3. In Run-4, the filtration rate was set at 0.5 m/d (21 L/m²/h) with PAC concentration of 40 g/L. The effluent turbidity showed below 0.1 NTU for all runs, and the removal rates more than 90% were observed. As for TOC removal, almost no removal of TOC was observed in Run-1 while the higher removal rates were obtained with the higher dosage of powdered activated carbon. Run-3 and 4 with PAC dose of 40 g/L showed the removal of 85% regardless of the filtration rates. Removal of UV254 was similar to that of TOC: removal of 13% at Run-1 and 90% at Run-3 and -4. As for the filtration efficiency, an average filtration time for TMP to reach 60 kPa was checked for each runs. The filtration time of around 5 days was observed in Run-1 and Run-2, 2 days in Run-3 and 60 days in Run-4. According to the results, the effluent water quality got better with higher dose of PAC and the filtration efficiency was enhanced with higher dose of PAC and lower filtration time.     

The degradation of an azo dye in a batch slurry photocatalytic reactor

The photocatalytic degradation of a commercial azo-reactive textile dye, Remazol Red F-3B, has been investigated in a batch slurry reactor using semiconductor catalysts like, ZnO and TiO₂, and two UV sources emitting mainly at 254 and 365 nm. Non-irradiated catalysts and non-catalyzed UV irradiation have negligible effect on the dye degradation. Initial pH, dye concentration, light power and catalyst loading as well as the catalyst type and UV wavelength are considered as process variables. The results showed that decolorization and TOC removal efficiencies of ZnO are higher under 365 nm UV. On the other hand, when two photocatalysts are compared, the decolorization performance of ZnO is higher than TiO₂ under 365 nm UV_, while TiO₂ performs better under 254 nm UV. Furthermore, from the TOC removal point, TiO₂ performs better than ZnO irrespective of the UV wavelength. TiO₂ irradiated under 254 nm UV degrades successfully both benzene and naphthalene derivatives.     

Effects of Ozonation on AOC Content of Humic Finnish Groundwater

The effects of ozonation on assimilable organic carbon (AOC) content of humic groundwater were investigated in batch experiments on three different groundwaters used as drinking water in Finland. All water samples had quite high concentrations of iron (range 2–10 mg/L) and manganese (range 0.1–0.2 mg/L) and therefore combined ozonation and filtration is a possible water purification method. The ozone dosage used varied from 0 to 16.6 mgO₃/L (ΔO₃/TOC?=?0–1.6). The ozone treatment increased the AOC concentration in the groundwater samples to different degrees. For example, an ozone dose of 3.9 mg/L increased the AOC concentration in different water as follows: from 49 μg/L to 55/L, from 7 μg/L to 119 μg/L and from 23 μg/L to 226 μg/L.     

Destruction of toxic organics in water by an injection‐type downflow UV/O3 oxidation reactor

An injection‐type downflow UV/O₃ oxidation reactor (IDUOR) was developed mainly with the combination of a configuration of two concentric cylinders with the UV lamp in the bottom axial position and a downflow mixing gas‐liquid injector. This configuration leads to atomizing of the solution resulting in higher levels of dissolved ozone which is then illuminated by UV light to generate hydroxyl radicals. Four different toxic wastewaters including 4‐chlorophenol, carbofuran, dye‐auxiliaries and pesticide wastewater with a COD range of 164 to 1602 mg/L and a microtoxicity (EC₅₀) range of 3.008% to 19.062% were used to investigate the performance of the device. It was found that the ozone utilization efficiency attained was more than 75% with very satisfying COD and TOC reduction for wastewater treated with IDUOR. The IDUOR when compared to a conventional stirred bubble UV/O₃ reactor exhibited increased efficiency for ozone utilization and COD, TOC, microtoxicity reduction. Also, the pseudo‐first rate constants on the basis of COD and TOC reduction indicated much higher oxidation rate of organics in IDUOR, providing additional evidence of the considerable treatment potency of IDUOR for destruction of toxic organics in water.     

饮用水预臭氧化与预氯化对比中试研究

通过常规处理预臭氧化和预氯化中试,对比研究了两种预氧化工艺对浊度、有机物、氨氮及消毒副产物前体物的去除效果。结果表明,预臭氧化后砂滤池出水中浊度平均值小于0.1 NTU,CODMn、UV254、TOC平均去除率分别为50.70%、84.60%、85.22%,去除效果明显优于预氯化。预臭氧化能有效去除消毒副产物前体物,氯消毒后CHCl3浓度为0.17μg/L,约为无预处理时的1/7,而预氯化会增加消毒副产物的生成量。     

Effects of O3, O3/H2O2 and Coagulation on Natural Organic Matter and Arsenic Removal from Typical Northern Serbia Source Water

The objectives of this study were to investigate the effects of ozone and the O₃/H₂O₂ process on FeCl₃ coagulation efficiency for the removal of the high content of natural organic matter (NOM) and arsenic (As) from groundwater (DOC = 9.27 ± 0.92 mg/L; 51.7 ± 16.4 µg As/L). Arsenic and NOM removal mechanisms during coagulation/flocculation are well investigated. However, data concerning arsenic removal in the presence of NOM, which is the subject of this article, are still insufficient. Laboratory and pilot plant test results have shown that the competition of NOM and As for adsorption sites on the coagulant surface have great influence on coagulation/flocculation efficiency for their removal. With both oxidation pre-treatments, arsenic content after the coagulation process was less than 2.0 µg/L in treated water. Application of ozone has a lower influence on coagulation efficacy in terms of DOC reduction, compared to the O₃/H₂O₂ process with the same ozone dose.