Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-Ozonation and Subsequent Biological Treatment Using Test-Scale Plant

The effects of pre-ozonation and subsequent biological treatment process on the decrease in dissolved organic carbon (DOC) and color were investigated in a test-scale plant of 5 m³/d capacity using actual raw wastewater (RW) from a dye works. Ozone dosage rate and contacting time were around 70 mg/L on average and 30 min, respectively. The DOC concentration was gradually decreased from 36.1 to 19.3 mg/L on average through the process and the DOC removal rates were 24.4% after ozonation and 46.5% after subsequent biological treatment. The average color value was rapidly decreased from 1.75 to 0.20 after ozonation, and the color removal rate was 88.6%. The values of adsorbable organic halide formation potential (AOXFP) and trihalomethane formation potential (THMFP) were gradually decreased by each treatment process, indicating the increased safety of the treated water. Slight morphological differences due to decomposition of the predominant bacteria by residual ozone were observed. The DOC removal rate brought about by pre-ozonation was slightly higher than that by the process consisted of biological treatment and post-ozonation, although no obvious difference in the color removal was observed between them.     

Application of Ozonation to Dyeing Wastewater Treatment—Case Study in Nishiwaki Treatment Plant

Three treatment methods, raw wastewater (RW)?→?coagulation?→?biological treatment (RCB), RW→?pre-ozonation?→?biological treatment (ROB) and RW?→?biological treatment?→?post-ozonation (RBO), were investigated to clarify their effectiveness in treating dyeing wastewater from a treatment plant. The decrease in dissolved organic carbon (DOC) was in the following order: RCB?≥?RBO?>?ROB. DOC removal of 200 mg/L by biological treatment of RW was clearly higher than that of 12 mg/L by ozonation. On the other hand, only DOC removal of 108 mg/L was observed by biological treatment in RW after ozonation. The decrease in biological oxygen demand (BOD₅) was in the following order: ROB?≥?RCB?>?RBO. Because of the enhancement of biodegradability brought about by ozonation, BOD₅ after ozonation in RBO was higher than that of RW after biological treatment. Color was effectively removed by ozonation for both RW and RW after biological treatment, and the decrease in color was in the following order: RBO?>?ROB?≥?RCB. Adsorbable organic halide formation potential (AOXFP) and toxicity unit (TU15, exposure time is 15 min) were more effectively decreased by biological treatment than by coagulation or ozonation, although the differences among RCB, ROB and RBO were very small.     

Treatment of Industrial Landfill Leachates By Chemical And Biological Methods: Ozonation,Ozonation + Hydrogen Peroxide,Hydrogen Peroxide And Biological Post-Treatment For Ozonated Water

The objective of this study was to determine a suitable treatment method for variable waters from a forest industry landfill site. The main target was to find out the impact of different chemical treatments on the composition and biodegradability of those waters. Earlier studies have shown that biological treatment alone is not a suitable treatment method for these waters. That is why ozonation, ozonation+hydrogen peroxide and hydrogen peroxide treatment were studied in a laboratory scale. The ozonated waters were also biologically post-treated.

All the methods studied were able to degrade a part of the organic compounds and convert them into a more biodegradable form. Also the BOD/COD -ratio increased significantly. The removal of organic compounds by ozonation was 30 - 50 %. Hydrogen peroxide addition did not improve the degradation. The combination of pre-ozonation and biological post-treatment gave a total TOC removal between 50 - 95 %.     

Removal of Pesticides by a Combined Ozonation/Attached Biomass Process Sequence

Different combinations of ozonation and biological treatments were tested on an industrial effluent containing high pesticide concentrations. Ozonation was performed in 450 L columns at 1.5 h HRT each. Biological treatment was carried out in a submerged filter (BIOFOR). Ozone was effective in removing herbicides but dosages up to 1000 mg L^?1 were needed. The improved biodegradability of the organic compounds after pre-ozonation was demonstrated by Oxygen Uptake Rates (OUR) tests and by the efficiency of biological treatment towards COD, and pesticides. The Italian discharge limit of 50 ppb total pesticides was achieved by combining pre-ozonation, biological treatment, and post- ozonation.     

Ozonation of Dyestuffs and Intermediates and Further Decrease in Dissolved Organic Carbon by Post-Biodegradation

Four each of water-soluble dyestuffs, intermediates and reference compounds were examined to determine the effect of the combined use of ozonation and post-biodegradation on the decrease in the amount of dissolved organic carbon (DOC) and the synergistic effect induced by ozonation. The amount of DOC removed by ozonation was increased initially with increasing ozonation time, and showed a plateau thereafter. The amount of ozone required to remove 1 mg of DOC (ΔO₃/ΔDOC) ranged from 5.2 to 18.6 mgO₃/mgC for the dyestuffs and the intermediates. The DOC concentrations of all the ozonized solutions were decreased with incubation time. In the case of the dyestuffs and the intermediates, the total amounts of DOC removed were increased with increasing ozonation time and showed a plateau thereafter. The synergistic effect (the ozonation-induced increase in the amount of DOC removed by the biological process) was dependent on the initial biodegradability, and was observed in all the dyestuffs and the intermediates in the range of 0.2 to 42.7 mgDOC. On the other hand, no synergistic effect was observed in the reference compounds of high biodegradability.     

Control of residual organic matter to reduce bacterial regrowth potential for wastewater reuse

Several problems have been reported about accumulated microorganisms in reclaimed water distribution systems. This paper presents the results of residual organic matter (OM) removal and apparent bacterial regrowth potential of treated wastewater obtained from laboratory-scale experiments using advanced biological treatments: two immobilization processes in series and a membrane bioreactor (MBR) process. Furthermore, a nanofiltration (NF) membrane process was applied to effluents of both advanced biological treatments. The immobilization process removed large molecular weight (MW) fractions >5,000 since immobilized microorganisms had sufficiently acclimated. The NF membrane was more effective in rejecting large MW fractions in the effluents of the immobilization and the MBR treatments. But it was difficult to reject small MW fractions <1,000 by NF. Neutral hydrophilic fraction of DOC was reduced by both advanced biological processes, and it can be thought that the microorganisms in the advanced processes could decompose and grow on some part of the neutral hydrophilic fraction. Quantity of attached microorganisms in the second immobilization reactor was significantly reduced compared to that in the first immobilization reactor. This suggests that apparent bacterial regrowth potential is controlled by the accumulation of effective microorganisms in the first reactor.     

膨润土改性产品在废水处理中的应用及进展

本文介绍了膨润土基本的矿物学性质,阐述了膨润土及其改性产品在废水处理中的有效作用及应用前景。膨润土经改性后可用于处理多种工业废水,其中对染料废水、重金属离子废水和有机废水,其去除率比原土高。同时,对膨润土的发展应用问题进行了展望。     

Adsorption Equilibrium of DOC by Activated Carbon and the Influence of Preozonation

A linear isotherm model, modified to account for a non-adsorbable fraction, was found to fit adequately the adsorption equilibrium of organic matter from a tertiary treated wastewater. The isotherm slope varied significantly among sample days, but the range of variability did not exceed a factor of two. A moderate ozone dose (0.5 g O₃/g DOC) enhanced adsorbability in both laboratory and full-scale systems, whereas higher doses appeared to decrease adsorption. Preozonation had little effect on the nonadsorbable portion of DOC.     

Combined Physicochemical Treatment of Textile and Mixed Industrial Wastewater

Wastewaters derived from a textile factory and an industrial park were subjected to treatment with ferric chloride coagulation; ozonation; ferric chloride pre-coagulation/Fenton-based process/lime post-coagulation; Fenton-based process/lime post-coagulation; and ferric chloride pre-coagulation/ozonation. Schemes with the Fenton-based process proved the most efficient for treatment of both wastewater samples. The characteristics of wastewater samples treated by a Fenton-based process at H₂O₂/COD weight ratio 0.5:1 complied with the discharge limits stated by regulations for wastewater directed to local sewerage. The Fenton-based process/lime post-coagulation scheme proved more efficient than ferric chloride pre-coagulation/Fenton-based process/lime post-coagulation system. The increase of H₂O₂/COD weight ratio to 2:1 resulted in 5 and 10% of residual COD and DOC, respectively. All studied processes and combined physicochemical treatment schemes, except single ozonation, resulted in toxicity reduction and biodegradability improvement in both wastewater samples. The operational costs of applied treatment schemes were calculated and indicated the Fenton-based process schemes as the most feasible and cost-effective.     

高级氧化技术处理石化废水的研究进展

石化废水是石化企业用石油或石油副产物生产烯烃等化工原料和合成各种有机化学产品所排出的废水。目前主要采用生物法进行处理。但是因为石化废水的量大,有机物含量高,传统的生物处理法中的微生物活性会受到抑制,导致某些石化废水处理不经济,有些排出废水水质不能满足要求。综合了近几年国际国内对于石化废水处理的研究状况,介绍了几种高级氧化法的优缺点,并指出未来对于石化废水处理的研究重点和方向。     

TREATMENT OF KRAFT PULP AND PAPER WASTEWATERS BY MEANS OF FOAM SEPARATION

The pulp and paper industry is the third largest industrial consumer of fresh water in the United States. The current use rate of over two trillion gallons annually is expected to increase as the demand for paper products continues to rise

Of the various methods of producing paper from wood, the Kraft process is the most widely used. Color, dissolved and suspended organic matter, and dissolved inorganic solids are major pollutants in Kraft processing wastewater. Current federal regulations limit the amount of solids and organic matter that a Kraft facility may dispose into public waters, so most plants have some form of wastewater treatment

In this study, the capacity of a continuous-flow, foam separation system to effect removals of color from a Kraft process wastewater was evaluated. The cationic surfactant, EHDABr, was used to precipitate color bodies in the wastewater and create a foam to carry the precipitates from the wastewater. The effect of pH adjustment was also considered. Color removals in the area of 90% were achieved

Removal of precipitated solids was enhanced by increasing the detention of wastewater in the treatment system.     

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.     

Treatment of tannery wastewater through the combination of a conventional activated sludge process and reverse osmosis with a plane membrane

Tannery wastewater contains high concentrations of organic matter (COD) with a significant percentage of refractory organic compounds, ammonium substances, salts (i.e. chloride and sulphate) as well as sulphur. Contaminants have to be removed in order to avoid significant environmental impacts. This paper presents the results obtained from a pilot scale study developed in the tannery district of Solofra in Southern Italy. It was aimed at evaluating the reuse of wastewater produced in the retanning process. The treatment process consisted of a biological treatment, as a pre-treatment, followed by a physico-chemical process (with a polymer as a coagulant) and reverse osmosis with a plane membrane. The biological pre-treatment was able to remove approx. 67% of COD, while the membrane system completed the purification process with the removal of the refractory organic compounds (chloride and sulphate). In the test carried out, the combination of a biological pre-treatment with a plane membrane system showed satisfactory results in terms of wastewater recovery and reuse in the tannery production cycle.     

Recovery and Removal of Phenolic Compounds from Olive Mill Wastewater

Food wastes are today considered as a cheap source of valuable components since the existent technologies allow the recovery of target compounds and their recycling inside the food chain as functional additives in different products. Olive mill wastewater (OMW) is generated from olive oil extraction systems. It has high added-value compounds namely phenolics, recalcitrants, pectin, and some important enzymes. It causes a certain amount of toxicity/phytotoxicity because of its phenolic compounds. OMW also has significant impacts when discharged directly into surface waters. Therefore, the treatment of olive mill wastewater is very much needed. Several types of techniques have been investigated for OMW treatment along with recovery and removal of its phenolic compounds. Among these techniques, physical ones are utilized for extraction purposes, while chemical and biological methods are applied in order to diminish organic load. In this review, current status and recent developments in the recovery and removal of phenolic compounds from OMW have been critically examined.     

Ozonation of C.I. Reactive Yellow 3 and Further Decrease in Dissolved Organic Carbon Concentration by Post-Biodegradation

Using C.I. Reactive Yellow 3 as the target compound, the effect of the combined use of ozonation and post-biodegradation on the decrease in dissolved organic carbon (DOC) concentration was investigated, and the synergistic effect (the difference in the amounts of DOC removed by the biological process between solutions with and without ozonation) was estimated. A decrease in DOC concentration was observed during ozonation and ΔO₃/ΔDOC was decreased from 16.0 to 5.2 with increasing ozonation time. Moreover, an enhancement of biodegradability was shown. A further decrease in DOC concentration was observed during the biodegradation after ozonation. The total amount of DOC removed by the combined method was increased from 73.6 mg at 30 min to 159.9 mg at 4 h. The synergistic effect was in the range of 22.7 to 39.2 mg. BOD₅ was a better indicator of the synergistic effect than BOD₅/DOC.     

Hydrothermal dewatering of brown coal and catalytic hydrothermal gasification of the organic compounds dissolving in the water using a novel Ni/carbon catalyst

Brown coals will continue to be important energy resources in the near future, but their high water contents, which sometimes exceed 50 wt%, and their low calorific values restrict their utilization. Development of an efficient treatment method for dewatering and upgrading is desired to utilize brown coals on a large scale. Hydrothermal treatment is believed to be a promising treatment method because it can not only remove water in liquid phase but also improve calorific value of brown coal. However, some organic compounds are inevitably leached out from the coal during the treatment to emit a huge amount of wastewater containing organic compounds in small concentration, which causes a loss of coal energy as well as a serious problem of wastewater treatment. In this paper, an Australian brown coal (Morwell) was hydrothermally treated for dewatering and upgrading at 250-300 °C. When treated at 300 °C, the water content decreased from 1.31 kg/kg on dry matter to 0.59 kg/kg on dry matter and the calorific value increased from 25.8 to 27.8 MJ/kg on dry matter, indicating that the hydrothermal treatment is really effective for dewatering and upgrading the brown coal. The reactivity to oxygen at low temperature was also reduced by the treatment, which will contribute to suppress the spontaneous combustion of the coal. On the other hand, the amount of organic compound dissolved in the recovered wastewater increased with increasing treatment temperature and it reached ca. 1.5% on carbon basis at 300 °C. The wastewater was treated using a novel Ni-supported carbon catalyst developed by the authors. The organic compounds in the wastewater were completely gasified at as low as 350 °C under 20 MPa at the liquid hourly space velocity of as large as 50, producing combustible gas rich in CH₄ and H₂. The proposed hydrothermal gasification process was found not only to be efficient for wastewater treatment but also to be effective for energy recovery from wastewater. The gasification process combined with the hydrothermal treatment process, which is operated under the conditions close to those of the gasification, will be a new and effective brown coal pretreatment process.     

Combined performance of electrocoagulation and magnetic separation processes for treatment of dye wastewater

In this study, a combined system of electrocoagulation (EC) and magnetic separation (MS) has been applied to the treatment of dye wastewater, and its performance has been evaluated. The floes formed in the electrocoagulation using Fe anode are magnetized and thus they could be removed by magnetic separation. The removal of suspended solids, color and COD was improved with an increase in electric current up to about 15 A and with a decrease in liquid velocities in EC. While the remaining suspended solids in the treated water were reduced to a few ppm and the color was removed almost perfectly (Max. 96%), that of COD was relatively low and only 81%. A further powerful operation can be expected from the present system if it is combined with an additional process, such as electrolysis or oxidation, to reduce COD more efficiently.     

Removal of residual organic matter from secondary effluent by iron oxides adsorption

Residual organic matter (ROM) removal is an important issue in wastewater reclamation and reuse processes. Use of iron oxide particles (IOPs) as adsorbents for further treatment of the secondary effluent was investigated to mainly remove non-biodegradable residual organic matter under various operating conditions. ROM removal by IOP adsorption was evaluated in terms of the changes of UV absorbance, COD, and DOC concentrations in feed (secondary effluent) and treated water. The respective relationship of UV removal with COD and DOC removal efficiencies exhibited somewhat different profiles, possibly due to the influence of ROM properties on adsorptive removal mechanisms by IOP, such as hydrophobicity and coordinative capability. The types of IOPs such as ferrihydrite, geothite, and hematite were compared, and it was found that amorphous ferrihydrite was most effective in ROM removal. Maximum ROM removal was occuring at a solution pH of approximately 6.0, which might be ascribed to the ability of ligand exchange related to the association and dissociation of ROM molecules and IOPs at differing pH levels. Substantial reduction in the oxidation state (OS) of the treated water at high ROM removal indicated the coordination of highly oxidized groups in ROM at the IOP surface, such as carboxylic groups.     

Improvement of Biodegradability of Oil Field Drilling Wastewater Using Ozone

The possibility of improving the biodegradability of drilling wastewater using ozone was investigated following coagulation pretreatment. The biodegradability of wastewater was improved significantly following the start of ozonation, and the molecular weight of organic compounds decreased continuously with the progress of oxidation. It is interesting that minimum biochemical oxygen demand, total organic carbon (BOD/TOC) ratio (0.4 g/g) was observed when wastewater was treated with ozone continuously for 15 min. The combination of ozonation for 5 min (ozone consumption ratio of 2.6 g ozone/g TOC) followed by biological degradation produced a total TOC removal rate of 54.3%, which was comparable to direct ozonation for 30 min under the same conditions (TOC removal rate of 54.9%; ozone consumption ratio of 8.7 g ozone/g TOC). It is clear that biological treatment following short-term ozonation was very efficient in TOC removal. A process of successive coagulation-precipitation, ozone oxidation, and biodegradation seemed to be a good option for drilling wastewater treatment.     

The Study on the Ceramic Membrane Wastewater Reuse System with Pre-Ozonation and Coagulation

A new wastewater reuse system using ozonation, coagulation and MF ceramic membrane (0.1 μm) filtration was developed. The testing was performed using secondary effluent treated at the wastewater treatment plant (WWTP) in Tokyo, Japan. The volume of treated water by the pilot study equipment is about 90 m³/day. The combination of pre-ozonation and coagulation processes achieves continuous stable membrane filtration with flux of 4m³/m²/day (167 LMH). A stable membrane filtration could be maintained by controlling ozone dosing rate depending on secondary effluent (raw water) quality fluctuation. The COD (Mn) removal ratio in raw water was 50 to 60%, and the color removal ratio satisfied 80% or higher. The quality of the treated water that was obtained from our pilot study was better than the California's standards.