advanced oxidation processes

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5- triazine) is one of the most common herbicides found in groundwater and surface water [31,32]. Figure 5 sum- marized the current literature reports on the atrzine de- gradation mechanism in advanced oxidation processes. As shown in dash circles in Figure 5, the structure of atrazine contains three main functional groups attached to the triazine ring: isopropylamino group (a), chloro group (b), and ethylamino group (c). Hydroxyl radical attacks the three functional groups and the unsaturated ring structure to degrade the compound. In the figure, R1, R2, and R3 denote the molecular structure of atrazine after removing the fuctional group a, b, and c respective- ly. In the advanced oxidation processes, the oxidation of these groups follows the pathway I, II and III as depicted in Figure 5.

Now days the presence of pharmaceuticals and their metabolites in urban wastewater, mainly as a consequence of the uptake of medicines, is largely known [1-5]. Because of the presence of active biochemical principles in their molecules, pharmaceuticals, once released to water environments, present potential hazardous effects on humans and aquatic ecosystems [6,7]. Removal of these contaminants should be achieved in conventional wastewater treatment plants, mainly through biological oxidation, but these systems are not specifically designed for this role. In fact, as rule of thumb, emerging contaminants pass unaffected in a great extent through the classical unit operations of wastewater treatment plants [8-11]. However, because of their persistent and potentially hazardous character, these compounds may negatively affect living organisms in the aquatic environment and, consequently, more advanced treatments are needed to complete their removal from wastewater. In this sense, several researches have shown that ozonation and advanced oxidation processes (AOPs) have been successfully used to oxidize these contaminants from water [12-14]. Thus, literature has already reported many works where laboratory prepared aqueous solutions or biologically treated urban wastewater spiked with emerging contaminants (ECs) are successfully treated with AOPs. However, results on the combined effect of biological and advanced oxidation processes are required in order to check the real improvement in removal rates when these contaminants are initially present in the wastewater. Thus, in this work, an urban wastewater doped with nine ECs has been biologically and chemically treated in two sequential steps with activated sludge and different AOPs, respectively. Activated sludge was collected from a secondary biological treatment of an urban wastewater treatment plant and ozone, UVA light and iron type catalysts (Fe(III) and Fe 3 O 4 ) were the constituents agents of AOPs applied. The ECs added to

Persistent organic pollutants in industrial wastewater cause serious pollution problems in the aquatic environ- ment [1]. Some persistent organic pollutants are very toxic and are hazardous to the health of humans and other biota. Persistent organic pollutants are poorly biodegradable, meaning that natural processes cause very little decomposition of these compounds to occur, so these compounds can pollute the environment for a long time. Water is currently widely treated using activated sludge or activated carbon or using solid-liquid separation me- thods, but it is difficult to completely decompose persistent organic pollutants using these methods [2]-[6]. At- tention has recently been paid to the use of advanced oxidation processes (AOPs) to remove persistent organic pollutants from water.

Abstract: Advanced Oxidation Processes (AOPs) are a group of oxidation processes carried out to remove harmful persistent organic pollutants (POP) from water, which are otherwise very hard to remove. The last century saw a glut of chemical industries rising up to meet the needs of modern day commodity chemicals like detergents, dyes, pesticides and so on. Treatment of effluents of such industries has always been tenacious and cumbersome. Advanced oxidation process has now become the inevitable technology for the future to tackle the inexorable problems of pollution.

Textile and dye industries are considered as the second largest water consuming industries among all industries. The high amount of water was consumed during the processing, finishing and cleaning operations in textile industry[1, 2]. In textile industries, the massive amounts of wastewater are generated during production and application of dye. Generated wastewater has high initial chemical oxygen demand (COD) and is a major threat to ecology and aquatic life[3, 4]. From an environmental point of view, the discharge of textile wastewaters into the aqueous environments can obstruct light penetration, preventing the photosynthesis phenomenon. In general, wastewaters generated by the textile industries are characterized with the presence of low biodegradable organic dyes, which are not suitable for conventional biological wastewater treatment technologies. Conventional biological methods have limitations to treat the high level of COD [5-7]. Advanced oxidation processes (AOP) were found to be more efficient for the treatment of elevated levels of COD[7-8].Advanced oxidation processes (AOP) such as Acoustic cavitation, Fenton and Photo Fenton process are useful for the treatment of high initial concentration of COD [9]. The sonochemical effect is cavitational phenomena based on ultrasound interaction with aqueous liquid medium, when ultrasound passed through the liquid medium cycles of compression and rarefaction are developed. These cycles induced the cavitational bubble which expands and compresses before the collapse at million locations in the reactor. The higher temperature (4000–5000 K) and pressure (1000–50,000 bars) conditions reach inside the bubble cavity before collapsing. These conditions are highly useful for enhancing the rate of chemical processing. During cavitation cycle, reactions are occurring at the three zones: (a) inside the cavity of the bubble, (b) at the interface of gas– liquid, and (c) radicals generated after the collapse of the cavity [10-13].The application of ultrasound alone is not efficient for the degradation of the target organic pollutant because of the fact that the ultrasound alone requires more time and high amount of energy for an acceptable degradation [14-15].

Recently, wastewater treatments have been marked by the application of Advanced Oxidation Processes (AOPs), which offer promising opportu- nities to degrade or even mineralize pollutants us- ing mild temperature and pressure conditions. Among these AOPs, those involving hydrogen peroxide such as H 2 O 2 /UV, the Fenton process and

Increasing urbanization and industrialization have thus resulted in a dramatic increase in the volume of wastewater. The major industries contributing to water pollution are – textile mills, electroplating industry, metal processing industry, pulp and paper mill and tannery industry. Major pollution in textile effluent is due to high suspended solids, chemical oxygen demand, heat, color, acidity and other non-biodegradable substances. In order to tackle this menace of pollution problem, it is desirable to degrade the dye into non toxic form before its discharge into the main stream. Advanced Oxidation Processes are the one that offers a highly reactive, non- specific oxidant namely hydroxyl radicals (HO • ), capable of destroying wide range of organic pollutants in water and wastewater. Fenton’s reagent oxidation is a homogeneous catalytic oxidation process using a mixture of hydrogen peroxide and ferrous ions. The main advantage of the Fenton’s reagent is its simplicity in usage.

The aim of the study was to describe the characteristics of a natural antioxidant derived from the group of the hydroxycinnamic acids (sinapic and ferulic acid). Electrochemical methods and other spectrophotometric assays were studied for the analysis to determine the mechanism of action in the advanced oxidation processes. ABTS and DPPH methods has been allowed to access the potential of natural compounds to scavenge free radicals, but the methods of FRAP and CUPRAC possible to determine the potential for reduction of copper and iron ions. The curve of the differential pulsed and cyclic voltammograms found that ferulic acid is oxidized in one step electrode, and sinapic acid in two stages electrode. Sinapic acid oxidizes easily with superior abilities of antioxioxidant. Based on the survey, it was found that both tested hydroxycinnamic acids have high potential of antioxidants.

dilution is proving to be no longer a cheap, viable solution. The occurrence of micropollutants, therefore, poses problems for two major water management aspects, protection of source water, and reuse potential of a vast majority of municipal and industrial wastewater effluents. The traditional treatment methods such as secondary biodegradation cannot appreciably remove many of these contaminants of emerging concern. While advanced treatment technologies such as activated carbon and reverse osmosis can produce high quality water, they only transfer and concentrate the pollutants from one phase to another, requiring further processing to render the compounds inert. Advanced oxidation processes (AOPs), which produce reactive species like hydroxyl radicals in-situ, are identified as one of the potential technologies for the removal of trace concentrations of organics from various water streams (Abdelmelek et al., 2011).

Abstract: There are several studies in this same sense aiming to develop new processes and new technologies to minimize the volume and toxicity of effluents generated by chemical industries. Currently, technology advances in effluent and residues treatment is based on environmental sustainability (residual reuse) and in the degradation of pollutant substances with easier natural degradation. Technology has improved, Advanced Oxidation Processes (AOPs) for instance, being based on the generation of hydroxyl radicals as oxidant agent, seems to have great efficiency in the treatment of industrial detriments promoting the reduction of coloration in effluents and environmental decontamination. This project represents the efforts in making the effluent treatment of dairy industries using AOPs (Fenton Reagent, UV), produced by YAKULT, unit of Lorena, State of Sao Paulo viable. There have been evaluated, in the bench level, in batch process, different parameters such as time of exposition to UV radiation, pH range, temperature and different Fenton Reagent concentration. Due to these procedures, the reduction of COD was the main control variable in the results provided by the experiments, with 94.17% of organic matter degradation in the effluent.

Synthetic dyes are widely used in dyeing, painting, leather making, printing, paper mak- ing, cosmetics, photography, and coating [1] [2]. Wastewater especially from dye- ing/textile industries contains about 15% of the total dye that is discharged into the near- by water bodies without adequate treatment resulting in water pollution [3]. Water pollu- tion is common in developing countries. One example is Bangladesh. Dyes in wastewaters are non-biodegradable. Phase transfer of pollutants from aqueous system into sludge takes place when attempts are made to remove them by coagulation/flocculation, mem- brane separation (ultrafiltration, reverse osmosis) or adsorption on activated carbon [4]. To overcome such a problem, advanced oxidation processes (AOPs) were devel- oped to mineralize the organic pollutants. The mineralized components are mainly CO 2 , H 2 O and inorganic ions and/or biodegradable compounds [5]. AOPs are consi-

The degradation of IC by advanced oxidation processes presents some similarities and strong differences depending on the type of process. In general, from our current re- sults, standalone AOP process or the combination of these led to similar refractory in- termediates regardless the level of conversion. These compounds showed some toxic effect on life organism. The chemical nature of the reaction product was evidenced by means of FTIR spectra that showed the same fingerprint for all cases of AOP’s but dif- ferent from IC spectrum. The FTIR signals for sulfur, nitrogen and oxygen containing groups were observed as well as phenyl groups, which indicated the presence of carbox- ylates such as formates, acetates or propionates, as well as sulfates and amine or amide functional groups (isatine, for instances). The ozonation was the best process either being used as standalone or in combination with photocatalytic and sonolysis process. The presence of ozone enhanced formation of those oxidant species such as hydroxyl and peroxydril radical (•OH, HO 2 •, and O 2 − •). When ozone was used under ultrasound

reducing the transmitted fluence rate, and consequently, changing the effectiveness of hydroxyl radical production throughout the UV reactor. Other factors, such as reflection, refraction, shadowing, and lamp effects, also influence the spatial distribution of light within a UV reactor. Several models have been developed to characterize the spatial distribution of the UV fluence rate. These models include the Multiple Point Source Summation (MPSS) model (Jacob and Dranoff, 1970; Bolton, 2000); the Line Source Integration (LSI) model (Blatchley, 1997); the Multi-Segment Source Summation (MSSS) model (Liu et al., 2004); the modified LSI model (RAD-LSI) (Liu et al., 2004); and Discrete Ordinate (DO) methods (Fiveland, 1984; Stamnes et al., 1988; Liou and Wu, 1996). Liu et al. (2004) directly evaluated the performance of these models with experimental measurements of the fluence rate at different points within a UV reactor, the results being a compilation of the strengths and weaknesses of the each model’s ability to predict the fluence rate. Ducoste and coworkers further showed that the microbial log inactivation and the shape of the fluence distribution were sensitive to the fluence rate model selection (Ducoste et al., 2005; Liu et al., 2006). Their results suggest the need to evaluate the influence of the fluence rate model selection on any photoreactive process such as UV-initiated advanced oxidation processes.

The main advantage of the process is deg- radation organic as well as inorganic pollutants that will leading to high mineralization levels [Sanz et al. 2003, Canizares et al. 2009, Sta- sinakis 2008, de Sena et al. 2009, Martins et al. 2011]. Among the advanced oxidation processes, the easy-to-handle Fenton’s reaction has proven to be more effective in terms of removal rate as well as operating expenses for the treatment of toxic and/or refractory food industrial waste- water (Table 3) such as baker’s yeast industry effluents [Altinbas 2003], juice wastewater [Amora et al. 2012], meat industry wastewater [de Sena et al. 2009], coffee effluent [Tokumura et al. 2008], winery and distillery wastewater [Oller et al. 2011], olive mill wastewater [Zor- pas & Costa 2010] etc.

a catalyst in the presence of US and H 2 O 2 /US for dye re- moval and the high corresponding threshold of ZnO (425 nm), the process of (ZnO/H 2 O 2 /US) for dye removal is an environmentally-friendly method (6). The main advan- tage of this process is its inherent destructive importance. Moreover, the ZnO nano-photo-catalyst is non-toxic and has a high relative chemical stability. Among the other ad- vantages of using this reactor in the treatment of waters contaminated with dye compounds is its high capacity for absorption of the solar spectrum, low cost, and high ef- ficiency in removing organic molecules from both acidic and basic environments (7). Thus far, this process has been used to remove different contaminants from such environments. In 2008, Wang et al and in 2004, Yu et al used this process to remove acid red B, rhodamine B, and rhodamine dyes (8,9). Many different physical and chemi- cal methods such as activated carbon adsorption processes (10,11), absorbing resins (12), and the hydrogen peroxide oxidation process have been used to remove dyes; these processes, however, have some inherent limitations such as high costs, inefficacy, complexity, the formation of dan- gerous residual products, and high energy requirements. Therefore, it is necessary to find an effective method for the treatment of dye. Among the new oxidation methods known as AOPs, chemical oxidation using ultrasound in the presence of hydrogen peroxide is considered a promis- ing technique. Ultrasound is described as the generator of very active OH o , HOO o , and H o radicals (13). These radi-

Oxidation Process (AOP) has been introduced as a new method for purifying the effluents containing antibiotics (9). The oxidation process is one of the common methods in removing the pollutants because of simplicity, low costs, and high efficiency (8). The advanced oxidation process is also based on producing the strongest oxidants, such as hydroxyl radical in solution (8, 9). Using ultrasonic in AOP among the methods that produce hydroxyl radical is novel (10).

In SCO process, pseudo-first-order degradation rate constant was found, and this process provided the highest degradation rate constants. The degradation rate constant of the SCO process was calculated as 0.0187 min -1 . Also, the experiments were carried out by determining appropriate conditions for HCHO removal with SCO process. Optimum pH, ultrasonic power, ozone dosage, NZVI dosage and HCHO concentration for efficient removal of HCHO were 5, 100 W, 200 mg h -1 , 200 mg L -1 and 15 mg L -1 , respectively. It was found that the oxidation by hydroxyl radicals was the dominant removal mechanism. From this data, it can be concluded that the catalytic AOP of SCO is recommended for the treatment of effluents containing low concentrations of HCHO.

environment of dope dissolution has a lasting effect on the properties of the PVDF membrane as have been advanced in the preceding discussion, high intensity radiations such as ultrasonication may impact unique properties to the membrane [10]. Consequently, a fourth membrane was produced from dope dissolved by the novel application of ultrasonication. Although sonication has been employed routinely for the dispersion of particles in polymer solution for making membranes [11-14], it is rarely reported as a tool for polymer dissolution without the aid of mechanical stirring nor has its unique impact recognised beyond particle dispersion. This fourth method of polymer dissolution takes advantage of the highly energised environment of localised high temperature and pressure for chemical and physical changes produced as a result of the collapse of cavitation bubbles as well as other physicochemical effects arising from ultrasonication [10, 15]. All membranes were produced by the NIPS method under identical conditions except the conditions of polymer dissolution. Since every parameter and procedure were the same in the fabrication of the four membranes except the energy of the dissolution environment, it seems logical that any observed difference in the properties of the membranes could systematically be related to the effects of the different dissolution environments. To explore the effect of the dissolution conditions on the membrane properties relevant to low pressure water filtration, the membranes produced were characterised by scanning electron microscopy (SEM) for morphology, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) for crystallinity, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal stability and water contact angle (CA) analysis for wettability. Furthermore, mechanical strength stability and filtration performance using clean water and oil emulsion were also evaluated.

This complete color removal for the catalytic process was observed within 7 min of reaction time. The calculated initial rate of reaction of photocatalysis treatment was 8 times faster than that of ozonolysis. However, the remaining organic load of photocatalysis was almost 88% from its origi- nal while the final sulphur content was 27.3%. This contrasting behavior of the performance of the type of oxidation process stressed importance of physicochemical phenomena and intermediates molecules present during dye degradation. An insightful and mechanistic aspect of the dye oxida- tion was developed by performing quantumchemical calculations.

Fenton’s oxidation for the synthetic wastewater containing SDBS treatment was studied using central composite design and response surface methodology. The optimum conditions for this treatment was achieved by setting the experiment with hydrogen peroxide concentration at 2.5mM (high level) while the other two regressor variables, i.e., SDBS concentration and pH level were at 1.5mM and 3, respectively. Initial concentration of hydrogen peroxide was found to be more important for COD removal. Degradation capacity of the Fenton's reagent was less pronounced in the range studied. Nonselective oxidizing role of the hydroxyl radicals toward aromatics during initial stages of the aromatic ring sulfonated removal may change as the reaction proceeds and other oxidants appear. It was possible therefore, to obtain the empirical models to describe and predict removal of the major pollutants. Adjustment of the quadratic model with the experimental data was satisfactory. Analysis of variance showed a high coefficient of determination value 0.99. It was possible therefore, to develop the empirical equations describing and predicting the removal of the pollutants.