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.     

pH Effect on Ozonation of Ampicillin: Kinetic Study and Toxicity Assessment

Ampicillin (AP) is a penicillin-type antibiotic and one of the most widely used bacteriostatic antibiotics in human and veterinary medicine. A kinetic study was performed under different pH conditions (5, 7.2, and 9) to determine the degradation efficiency of AP by ozonation. The second-order rate constants for the direct reaction of AP with ozone were measured to be 2.2 ?5.4×10⁵ M^?1s^?1 under the pH conditions tested. The rate constants were greater at higher pH. The potential toxicity of the AP intermediates formed after ozonation under the various pH conditions were examined using a bioluminescence assay on Vibrio fischeri species. The biodegradability of the AP degraded products was also determined by measuring the BOD₅/COD of the ozonated samples under the different pH conditions. A lower biodegradability and acute toxicity was observed at the lowest pH (pH 5). These results suggest that higher pH conditions are needed for the removal of AP by ozonation in order to mitigate the residual toxicity that can remain even after complete removal of the parent compound by ozonation.     

Biodegradability and Toxicity of Cellobiosides and Melibiosides

In 2014, almost 16 million tons of surfactants were used globally for cleaning and industrial applications. As a result, massive quantities disperse into environmental compartments every day. There is great market interest in developing highly biodegradable, less-toxic, and renewable alternatives to currently used petroleum-based surfactants. Glycolipid surfactants, composed of a sugar headgroup and lipid tail, are effective surfactants and emulsifiers with a high tolerance to electrolytes and are easily tailored to address specific needs. The green synthesis and surfactant characteristics of a suite of cellobiosides and melibiosides were recently described. The biodegradability and toxicity of 1°-alkyl-O-cellobiosides, 2°-alkyl-O-cellobiosides, and 1°-alkyl-O-melibiosides with straight-chain alkyl tails of 8, 10, and 12 are reported in this study. Biodegradability was assessed by quantifying mineralization (CO₂ evolution). All of the glycosides were inherently biodegradable and most were readily biodegradable according to OECD and US environmental protection agency (EPA) definitions. The Microtox acute toxicity assay showed both chain length and headgroup had significant effects on toxicity, but most of the molecules were practically nontoxic according to EPA definitions with EC₅₀ values >100 mg L⁻¹. Cytotoxicity to human lung (H1299) and keratinocyte cell lines (HaCaT) was measured by xCELLigence and MTS assays. Cytotoxicity values were comparable to similar glycosides previously reported. IC₅₀ values were determined but in general, exceeded surfactant concentrations that are found in the environment. These data demonstrate the promising nature of these molecules as green alternatives to petrochemical surfactants.     

Ozonation Impact on Degradation and Toxicity of Non-Ionic Surfactants

Aqueous solutions of five selected non-ionic surfactants: Triton (i-octylphenolethoxylates), Tergitol (2,6,8-trimethyl-4-nonanoloxethylates), Symperonic (n-nonylphenol-oxethylates) and Brij (fatty alcohol ethoxylates) were investigated in this study. Using the bioluminescent bacteria Vibrio fischeri the toxicity of the surfactants solutions were determined. An attempt was made to relate rather low biodegradability of nonionic surfactant solutions measured by the BOD₅/COD ratio (ranging from 1 to 17%) to their toxicity. The ozonation process was carried out in a 1.5 dm³ stirred cell reactor equipped with two ozone detectors. The following parameters were analyzed: pH, COD, BOD₅, DOC, TOC, polarography as well as UV spectrum. The positive effect of ozonation, represented by decay of UV absorption, was visible in almost complete destruction of the surfactants, with exception of Triton X-705 (only 65% degradation after absorption of 2000 mgO₃/dm³). The most striking results were obtained in toxicity tests for ozonated solutions of the non-ionic surfactants – an increase of the bacterial growth inhibition (1.5 to 4 times increase in toxicity due to ozonation). The obtained results were discussed taking into account the literature and our own experimental data on mechanisms of ozonation and biodegradation of non-ionic surfactants of the Triton-type and similar chemical structures.     

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.     

Comparison between Ozonation and Photo-Fenton Processes for Pesticide Methomyl Removal in Advanced Greenhouses

So-called “Advanced Greenhouses” are a new approach to the concept of protected agriculture. Among other technological and structural improvements, these facilities give the possibility of recycling the irrigation surplus water, rich in lixiviates, salts, pesticides and its metabolites. After many cycles, the current is so concentrated on those substances that it becomes necessary for the presence of a membrane separation stage which brine, highly concentrated on those named pollutants, has to be treated before being sent to the public sewage system. Advanced Oxidation Processes, among other chemical treatments, can be considered an alternative to process this current effluent. In this work, concentrated aqueous solutions of methomyl as model pesticide (200 mg·L^?1) have been subjected to two of those processes: ozonation and photo-Fenton reaction. Analysis of the elimination of the pesticide itself and the grade of mineralization achieved have shown how, while the ozonation is the most effective process decomposing the pesticide (eliminating the total concentration in 60 minutes), the photo-Fenton reaction mineralizes successfully the 40% of the total organic load (the ozonation only can cope with 20%) but only decompose a 40% of the pesticide. Evolution of biodegradability and toxicity of the effluent along both processes was also analyzed. Intermediates generated both by ozonation and photo-Fenton did not increase the biodegradability of the treated effluents. Nevertheless, while acute toxicity just after 15 minutes of treatment with ozone is notably higher than for raw solution, and it is maintained till the end of the experiment (120 min), though, toxicity along photo-Fenton reaction has two growing and decreasing regions, always shows lower values than the provoked during ozonation. None of the two assayed processes has been proved to increase biocompatibility of highly concentrated methomyl solutions.     

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.     

Combination of Ozonation and the Fenton Processes for Landfill Leachate Treatment: Evaluation of Treatment Efficiency

Single processes such as ozonation, ozone/hydrogen peroxide, Fenton and several combined treatment schemes were applied for leachate collected from a waste disposal site. The implementation of combined Fenton and ozonation processes resulted in the highest chemical oxygen demand removal (77% from initial value) among all the treatment methods applied, while biodegradability improvement was observed during the Fenton pre-treatment only. Some decrease of chemical oxygen demand was obtained during the single ozonation or combined schemes including ozone resulting in slight if any biodegradability improvement. The addition of hydrogen peroxide to ozonation did not enhance chemical oxygen demand, dissolved organic carbon or biochemical oxygen demand removal compared to ozone alone. Ferric chloride coagulation used as a pre-treatment stage did not improve subsequent chemical oxygen demand removal by ozonation or the Fenton processes. Taking into account the effective chemical oxygen demand, dissolved organic carbon removal and biodegradability improvement the single Fenton process seems to be a preferable treatment method for the leachate treatment. Some reduction in toxicity to Daphnia magna was observed after the application of the studied treatment methods.     

Ozone-Induced Biodegradability Enhancement and Color Reduction of a Complex Pharmaceutical Effluent

The treatment of a complex pharmaceutical effluent using a combination of ozonation and biological treatment is reported with the use of ozonation as a pre- and posttreatment. Pretreatment facilitated biodegradability index (BI = BOD/COD) enhancement of up to 0.44 along with COD and color reduction of up to 42% and 33%, respectively. Subsequent anaerobic biodegradation of effluent indicated negligible biogas generation; however, aerobic biodegradation of pretreated effluent resulted in COD reduction (73%) and color reduction (62%), which was also indicated by the biokinetic parameters. Further, ozonation as a posttreatment led to higher overall COD (87%) and color (93%) removal.     

Removal of the UV Filter Benzophenone-2 in Aqueous Solution by Ozonation: Kinetics,Intermediates, Pathways and Toxicity

Benzophenone-2 (BP-2) is an important type of UV filter that has been widely used and detected in the aquatic environment with greater estrogenic toxicity. In our work, the removal of BP-2 with the initial concentration of 25 mg L^?1 was first carried out by ozone at different pH (ranging from pH 3.0 to 11.0), and we found a positive correlation between the pH values and the degradation efficiency of BP-2, among which the more rapid removal of BP-2 in alkaline condition was observed than acidic and neutral conditions. For the influence of aqueous humic acid (HA, the concentration ranged from 0 ppm to 100 ppm), the degradation rate of BP-2 by ozonation was first increased with the growth of humic acid concentration (from 0 ppm to 5 ppm), reaching to maximum at 5 ppm of HA and subsequently decreased with the growth of HA concentration (from 5 ppm to 100 ppm). Fourteen intermediate products in the ozonation process were distinguished by an electrospray time-of-flight mass spectrometer and then two degradation pathways were proposed. Through the theoretical calculation, we found the carbanyl group of BP-2 has the most reactivity to be easily attacked by ozone, providing us guides and theoretical basis on the supposed intermediate products. Furthermore, the P. phosphoreum acute toxicity test was conducted to evaluate the potential toxicity during the ozonation process.     

Aqueous meta-Chloronitrobenzene Degradation by Ozonation and Its Kinetics

The kinetics and degradation process of meta-Chloronitrobenzene by ozonation in aqueous solution were investigated. Compared to para-chlorobenzoic acid, the rate constant of meta-Chloronitrobenzene with O₃ was 0.59 L/(mol·s), while that of the reaction with ^?OH was 2.07 × 10⁹ L/(mol·s). The main intermediate products were chloronitrophenols and some carboxylic acids. Neither chlorophenols nor nitrophenols was detected. The five-day biochemical oxygen demand and chemical oxygen demand were determined. The ratio of the former to the latter was above 0.3 at 20 min. It was feasible to perform a continuous biotreatment step after 20 min of ozonation.     

Effect of Ozonation on Activated Sludge Solubilization and Mineralization

New strategies for sludge stabilization and mineralization need to be developed since the use of sludge in agriculture is debatable and sludge incineration cannot be a systematic solution. Minimization of sludge production should be preferred. In this work, the effect of ozone on activated sludge solubilization and mineralization during batch experiments is assessed by establishing carbon and ozone mass balances. After extended ozonation of the sludge, more than 90% of the particulate carbon is modified. Depending on the experimental conditions, from 15 to 50% is found in a soluble form and from 35% to 95% was mineralized. The VSS/SS ratio decreases from 86% to less than 50% illustrating the sludge mineralization. The initial rate of ozone consumption by the sludge is very high (estimated value: 30 mgO₃/g VSS.min) and corresponds to high rates of carbon solubilization and mineralization. More than 50% of the carbon obtained after ozonation is found to be readily biodegradable using a short-term BOD procedure.     

COD and AOX Removal and Biodegradability Assessment for Fenton and O3/UV Oxidation Processes: A Case Study from a Graphical Industry Wastewater

Due to process stability and excellent effluent quality, the use of membrane processes is rapidly expanding. However, a drawback is the production of concentrates and their proper disposal. In this study, reverse osmosis concentrate was treated by Fenton and O₃/UV oxidation processes. The concentrate contains halogenated compounds, recalcitrant COD and low biodegradability. The removal of halogenated compounds and the enhancement of biodegradability were examined. Comparing the investigated processes, Fenton oxidation resulted in a better mineralization of organic matter; however, O₃/UV oxidation achieved a better enhancement of the biodegradability. Furthermore, similar degradation of halogenated compounds were observed for both oxidation processes.     

Transformation of the Β-Triketone Pesticides Tembotrione and Sulcotrione by Reactions with Ozone: Kinetic Study,Transformation Products,Toxicity and Biodegradability

Rate constants between ozone and triketone herbicides, tembotrione and sulcotrione, were determined between pH 2 and 12. Both compounds are completely transformed within seconds by ozone under real water treatment conditions. A reaction pathway was proposed based on the identification of transformation products. Toxicity evaluation using Vibrio fischeri test showed that a residual toxicity remained even after degradation of the major by-products, but biodegradation significantly increased from 50% to 70% for molar ozone to pesticide ratios from 0 to 2. Thus, ozonation coupled with biological treatment would drastically reduce the risk associated to the presence of triketone herbicides.     

The Effects of Preozonation on the Biodegradability of Phenolic Solutions Using a New Gas-Inducing Reactor

To achieve effective COD removal, the combination of preozonation with biological treatment is necessary for phenolic wastewater treatments. Preozonation of 4-cresol, 2-chlorophenol and 4-nitrophenol solutions can be carried out with high ozone utilization rate using a new gas-inducing reactor. During the preozonation, the phenolic compounds can be completely decomposed with 100% ozone utilization rate. This new gas-inducing reactor is beneficial for the preozonation of phenolic solutions, comparing with a conventional gas-liquid reactor. The BOD₅ of preozonized phenolic solution is strongly related to both the degree of decomposition of phenolic compounds and the accumulation of intermediate products in aqueous solution. Based on the high ozone utilization rate, it is suggested that the optimal utilized ozone dose for 4-cresol, 2-chlorophenol and 4-nitrophenol can be chosen as 360, 350 and 400 mg/L, respectively. At those optimal utilized ozone doses, the ratio of BOD₅/COD of preozonized 4-cresol, 2-chlorophenol and 4-nitrophenol solutions increase to 0.33, 0.26 and 0.33, respectively.     

Aqueous Ozonation of Pesticides: A Review

The ozonation reactions of pesticides in aqueous solution have been reviewed. Degree of reaction and reaction product identity are included. Compounds are classified into five groups: chlorinated hydrocarbons, organophosphorus compounds, phenoxyalkyl acid derivatives, organonitrogen compounds, and phenolic compounds. Experimental conditions for each study are summarized. Much work has been carried out under conditions atypical of those encountered at drinking water treatment plants. Thus, the findings of the papers reviewed cannot be applied directly to potable water treatment.     

Biodegradability Improvement of Aqueous 2,4-Dichlorophenol And Nitrobenzene Solutions By Means of Single Ozonation

The possibility of the integration of ozonation and biological processes as an economical way to treat biorecalcitrant organic compounds such as nitrobenzene and 2,4-dichlorophenol was investigated. In the pre-treatment step, stoichiometric coefficients and pseudo first-order kinetic constants were obtained. Biodegradability was monitored throughout the ozonation step, in order to evaluate the optimum ozone doses. The low TOC reduction after these ozone doses allowed much of the organic carbon to be removed in the biological stage. In the case of 2,4-dichlorophenol, the biodegradability improvement was checked in an aerobic bioreactor. By means of the combined ozonation-biological oxidation, up to 80% of the initial organic content was removed. Results presented in this study show the feasibility of using the combination of ozone and conventional biological treatments to treat wastewaters containing these pollutants.     

Effect of Ozone Pretreatment on Biodegradability Enhancement and Biogas Generation Potential From Biomethanated Distillery Effluent

The study evaluates the effect of ozone pretreatment on biodegradability enhancement of biomethanated distillery effluent. Results revealed that ozone pretreatment led to biodegradability index (BI = BOD/COD) enhancement up to 0.58 along with COD, color and toxicity reduction of up to 33%, 25% and 40%, respectively. Anaerobic digestion of pretreated effluent resulted in favorable biogas generation with methane content, yield and COD reduction of up to 62%, 39 mL/g COD and 57%, respectively. Kinetics of biogas generation determined by modified Gompertz model indicated methane production potential and production rate of 48.08 mL/g COD and 8.085 mL/g COD.day respectively under optimal conditions.     

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.     

Cellular Toxicity and Mutagenicity Assays from On-Site Sampling of Drinking Water Treatment Plants Using Multistage Ozonation

Studies were carried out on-site in a potable water production plant utilizing ozonation treatment at three stages of the process. The quality of water in the treatment line was studied by chemical analysis, but also for toxicity to Hela cells after XAD resin concentration, and for mutagenesis to Salmonella Ames strains and mammalian cells V79 HGPRT system. With a sufficient dose of ozone and activated carbon adsorption, the initial cytotoxicity of the raw water and the mutagenic or promoter activity are destroyed.