A New Approach to Determine the Practical Ozone Dose for Color Removal from Textile Wastewater

In this study, the effect of applied ozone dose and pH on color removal from textile wastewater was studied. A lab-scale ozonation system was used in the experiments. When the applied ozone dose increased, the color removal efficiency and the rate constants increased, whereas ozone utilization ratio decreased. On the other hand, increasing the pH increased color removal efficiency and ozone consumption but decreased specific ozone dose. By using the experimental results, a new model has been developed to determine the required ozone dose for the removal of color. By means of this method, it was possible to determine the required ozone dose for reducing the amount of color up to desired levels. Experimental results and the model predictions were in good agreement not only for textile wastewater but also for different industrial effluents. Some parameters affecting ozone utilization such as pH, could also be incorporated into the model.     

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.     

Degradation of Recalcitrant Surfactants in Wastewater by Ozonation and Advanced Oxidation Processes: A Review

Surfactants are used in varieties of industrial cleansing processes as well as in consumer products. Spent surfactants normally enter domestic or industrial wastewater and are treated biologically. However, some of them are resistant to biodegradation and are released into the environment. Thus, the toxicity and environmental persistence of these surfactants are emerging concerns. Based on extensive review of the literature, ozonation and advanced oxidation using various combinations of ozone, hydrogen peroxide, ultraviolet light irradiation, and iron salts were found effective in degrading recalcitrant surfactants, including linear alkylbenzene sulfonates, alkylphenol ethoxylates, and quaternary ammonium surfactants. Biodegradability of these surfactants was improved after the treatment to some extent in the aqueous solution as well as in real wastewaters.     

Impact of chemical oxidation on biological treatment of a primary municipal wastewater. 2. Effects of ozonation on kinetics of biological oxidation

Activated sludge biological oxidation of municipal wastewaters has been applied under different experimental conditions to observe the effect of preozonation on COD and process kinetics. In all cases, previous application of ozone allows significant improvement of COD level reduction during subsequent biological oxidation. Biomass concentration also exerts a positive influence on COD level reduction. Thus, 54 and 82% COD level reductions are achieved after biological oxidation without and with 30 minutes of preozonation. During the ozonation period, increase of pH from 2 to 9 leads to 15 to 24% COD level reductions, but biological oxidation should be followed at neutral pH since extreme conditions (pH 2 and 9) reduce considerably the biomass concentration and hence the yield of biodegradation. At the conditions investigated herein, there is an optimum ozone dose, 150 mg per liter of wastewater treated, that leads to the maximum COD level reduction in the combined process (chemical plus biological oxidation). Both single biological oxidation and combined with preozonation follows a Monod kinetic model assuming COD as the substrate of biomass. From kinetic results it is confirmed that a combination of chemical and biological oxidation leads to the highest maximum specific rates of COD consumption.     

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.     

Advanced treatment of textile dyeing wastewater through the combination of moving bed biofilm reactors and ozonation

A four-stage lab-scale treatment system [anaerobic moving bed biofilm reactor (MBBR)-aerobic MBBR-ozonation-aerobic MBBR in series] was investigated to treat textile dyeing wastewater. The MBBRs were operated in a continuous horizontal flow mode. To determine the optimum operating conditions, the effect of hydraulic retention time (HRT) and ozonation time on pollutant removal were analysed by continuous and batch experiments. The optimum operating conditions were found to be 14 h HRT for both anaerobic and no. 1 aerobic MBBRs, 14 min ozonation time and 10 h HRT for no. 2 aerobic MBBR. The average influent concentrations of chemical oxygen demand (COD), suspended solids (SS), ammonia and colour were 824 mg/L, 691 mg/L, 40 mg/L and 165°, respectively. Under these conditions, the average effluent concentrations of COD, SS, ammonia and colour were 47 mg/L, 15.2 mg/L, 5.9 mg/L and 6.1°, respectively, corresponding to total removal efficiencies of 94.3%, 97.8%, 85.3% and 96.3%, respectively. The final effluent could meet the reuse requirements of textile industry. The anaerobic MBBR process improved the biodegradability of the raw wastewater, while the two aerobic MBBRs played an important role in removing COD and ammonia. The ozonation process enhanced the biodegradability of no. 1 aerobic MBBR effluent, and finally, deep treatment was completed in no. 2 aerobic MBBR. The combined process showed a promising potential for treatment of high-strength dyeing wastewater.     

Effect of Ozone on Removal of Dissolved Organic Matter and its Biodegradability and Adsorbability in Biotreated Textile Effluents

A study was conducted on the efficacy of ozonation in removing dissolved organic matter (DOM) in biotreated textile effluents and effects on its biodegradability and adsorbability. Results showed the efficient removal of color and fluorescence compounds were achieved through ozonation, due to increasing hydrophilicity and lowering molecular weight of DOM. A significant biodegradability improvement was also observed, and DOM adsorbability on activated carbon was highly dependent on ozone dosage. As the key parameter, consumed 3.8 g O₃/?g TOC₀ was the optimal dosage in the hybrid process combining ozonation with biological activated carbon (BAC) for wastewater reclamation.     

Different fouling modes of submerged hollow-fiber and flat-sheet membranes induced by high strength wastewater with concurrent biofouling

Exploration of two major commercialized flat-sheet and hollow-fiber membranes in a submerged membrane fungi reactor fed with a synthetic textile wastewater revealed striking differences in the extent and mechanism of fouling between the two types, indicating a case-specific scope of choice between the two for industrial wastewater treatment. The hollow-fiber membrane exhibited fouling with a cake layer composed of fungi and starch, intensity being proportional to the operating flux (0.05–0.3 m/d). Conversely, the flat-sheet membrane suffered from immediate internal pore blocking beyond a critical flux of 0.2 m/d. During the experiment with major constituents of the synthetic wastewater separately, while media containing only starch and only dye induced negligible fouling, flux-dependent pore blocking was evident for both the hollow-fiber (0.288 m/d) and flat-sheet membranes (1.3 m/d) for the mixture of starch and dye. Despite a remarkable 99% color and 97% TOC removal achieved by both membranes, fouling with different modes and intensity for the two types under similar conditions and for the same type of membrane under different exposure conditions warrants development of suitable modules for such recalcitrant wastewater.     

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.     

Ozonation of Animal Wastes Containing Oxytetracycline

The efficiency of ozonation on the degradation of oxytetracycline, a veterinary antibiotic, has been investigated in both cow manure and synthetic animal feeding operation wastewater at varying experimental conditions. With a rapid degradation of antibiotic in synthetic wastewater, ozonation improved its biodegradability and eliminated bacterial toxicity caused by oxytetracycline. The degradation rate of oxytetracycline depended on pH and applied ozone dose, but not initial antibiotic concentration in wastewater. In the case of manure treatment, ozonation efficiency in terms of oxytetracycline degradation was negatively affected by moisture and antibiotic content of manure. The degradation rate of oxytetracycline in manure slowed down upon the extension of treatment time since ozone could not react with strongly adsorbed antibiotic on manure. Increase in humic and fulvic acid carbon and mineral nitrogen content was an indicator for the improvement of fertilizing value of manure by ozonation.     

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.     

A Review on the Applications of Ozonation for the Treatment of Real Agro-Industrial Wastewaters

Regarding agro-wastewaters, the strong loads in bio-refractory substances and seasonality reduce the efficiency of biological treatments and ozonation can play an important role, so that this article reviews its application for such streams. Indeed, biodegradability and toxicity removal was assessed for a wide range of agro-effluents such as olive mill, wineries and distilleries, pulp and paper, cork and cheese production. Solid catalysts reveal promising potential, even though literature is still scarce reporting their use to actual streams. Thus, forthcoming research must embrace catalytic ozonation and continuous pilot-scale reactors behavior on the depuration of real agro-wastewaters to ensure future industrial application.     

Two-Step Wastewater Treatment: Sequential Ozonation - Aerobic Biodegradation

Ozonation of wastewater from olive related industries has been carried out after dilution with synthetic urban wastewater. The advantages of the application of different acidic and basic cycles during the ozonation process have been shown. Biodegradability of the final effluent measured as the biological oxygen demand to chemical oxygen demand ratio has significantly been increased (100–144% for table olive wastewater and 24–60% for olive oil wastewater). Aerobic biological experiments conducted by using non-acclimated microorganisms confirmed the suitability of the biodegradation after the chemical oxidation pre-treatment. A kinetic model based on a free radical mechanism has been used to simulate experimental results. Both chemical oxygen demand and dissolved ozone concentration profiles are well fitted by the model. The aerobic biodegradation process has been modeled by utilizing the Monod equation.     

Adsorptive removal of dye from real textile wastewater using graphene oxide produced via modifications of hummers method

Abstract

This work focused on producing different graphene oxide (GO) samples for further application in the adsorptive removal of dyes from real textile wastewater. Among all conditions tested, the sample produced using KMnO₄ and no sonication bath exhibited the best performance. Before the experiments using wastewater, kinetics and equilibrium of adsorption studies were performed with Methylene Blue (MB) dye. Experimental data showed the isotherm fitted the Freundlich model, and kinetic results fitted the pseudo-second order model. Theoretical q_max was 308.11?mg.g^?1 and over 90% removal of MB was reached in approximately 5?min. Although GO has been widely applied to remove cationic and anionic dyes from water, not many studies have presented GO as an adsorbent for real textile wastewater treatment. In 30?min, GO removed nearly 85% of turbidity and over 60% of color from a real sample, indicating that GO might be an excellent alternative to treat textile wastewater.     

Decomposition of Aqueous Naphthalene-1,5-Disulfonic Acid by Means of Oxidation Processes

Three different Advanced Oxidation Processes (ozonation at pH 7.5, electron beam irradiation and a combination ozonation/electron beam irradiation) have been applied to study decomposition of aqueous naphthalene-1,5-disulfonic acid (1,5-NDSA) with regard to mineralization and formation of biodegradable intermediates. Formation of biodegradable intermediates could not be indicated for any of the processes used; single electron beam irradiation treatment was the most efficient process for mineralization of organic carbon contained in aqueous 1,5-NDSA. Applied to a real wastewater effluent from a mixed municipal/industrial wastewater, electron beam irradiation with a radiation dose of 2 kGy was sufficient to reduce the concentrations of all naphthalene sulfonic acids and some of the alkylphenol ethoxylates also contained in that water by about 2 orders of magnitude.     

Treatment and recycling of textile wastewater —case study and development of a recycling concept

For a specific textile finishing company strategies forwater recycling and recovery of valuable chemicals have been developed. A comprehensive study of the company's resource consumption and emission profile was performed. On this basis selected end of the pipe and integrated recycling options were further examined in detail. When treating the mixed wastewater flow, a combination of a membrane bioreactor and subsequent nanofiltration has proved to meet all requirements for reuse. However, this approach is associated with considerable technological effort and potentially high costs. As an alternative, a relatively simple and straightforward process was tested to treat only the washing effluents by means ofultrafiltration. Based on results obtained from the ultrafiltration experiments, a process integrated recycling concept is proposed. By its implementation water consumption can be cut down by 87.5% within the washing process. Furthermore total COD emissions can be reduced by 80%, and as washing agents are partly recycled, consumption for the washing process can be lowered by 20%.     

Use Of Ozone For The Treatment Of A Combined Urban And Industrial Effluent: A Case History

This paper describes the treatment of highly colored urban wastewater containing a high percentage of industrial effluents and a significant concentration of detergents. The kinetics of detergent ozonation were established through a series of pilot tests including variation of the ozone concentrations in the carrier gas. The results obtained concerning the optimum conditions of ozonation - treatment dose and contact time - have been used for the design of an industrial ozonation plant.     

Effect of Ozonation on Biodegradability Characteristics of Surplus Activated Sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O₃/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.     

Manganese-Based Catalysts for the Catalytic Remediation of Phenolic Acids by Ozone

Manganese-based catalysts supported on Al₂O₃, TiO₂, ZrO₂ and CeO₂ were tested for the catalytic ozonation of a simulated wastewater involving phenolic acids. Comparing the Mn-Ce catalysts preparation method, wetness impregnation and co-precipitation, the last one showed to be more active. Moreover, the increase of Mn/Ce molar proportion from 22/78 to 70/30 increased the ozonation efficiency. The catalysts stability in terms of Mn leaching, carbon adsorption and effluent biodegradability was evaluated. Mn-Ce-O (70/30) CP shows to be the most suitable catalyst to improve phenolic wastewaters catalytic remediation by ozone.     

Impact of Operating Conditions on Decomposition of Antibiotics During Ozonation: A Review

Recent studies have identified antibiotics and other pharmaceuticals in wastewater and surface water in many countries. The presence of low level antibiotics in the environment has raised concerns regarding potential selection of resistant bacterial strains that would render ineffective the use of some antibiotics in clinical practice. Recent reviews indicate the potential of ozonation and advanced oxidation processes in degrading pharmaceuticals in various types of water. However, no focus has been put on the impact of the operating conditions on the ozonation of these pharmaceuticals. This paper reviews the recent progress of ozonation of aqueous antibiotics in order to identify the influence of the operating conditions such as pH, temperature, use of hydrogen peroxide, ozone dosage, reactor setup and wastewater characteristics on the degradation of antibiotics.