Impact of gradually-achieved high phenol loads on the nitrification and COD removal performance of an MBBR fed with synthetic wastewater.

Phenol is a noteworthy pollutant, found in effluents of many industrial processes, like oil refining and drugs production, which can impair the treatment efficiency of bioreactors. This study evaluated the performance of phenol, COD, and nitrogen removal of an aerobic bench-scale Moving Bed Biofilm Reactor (MBBR) exposed to gradually increasing phenol content over 233 days. The reactor had Hydraulic Retention Time (HRT) set at 3 h and 40% filling degree (K1 media), and was fed with synthetic wastewater containing phenol (10, 20, 50, 100, 250 and 400 mg/L), glucose (400 mgCOD/L), and 40 mgN-NH3/L. Phenol, COD, and ammoniacal nitrogen removal averages were high - above 88%, 81%, and 82%, respectively -, even when the MBBR was exposed to the greatest phenol loads, indicating that the biofilm was able to acclimate and resist high phenol concentrations. However, the intense EPS production revealed the impact caused by phenol to the biofilm from the concentration of 250 mg/L onwards. Even though, at this concentration, the average removals of COD and phenol were 87.2% and 89.7%. The removal of ammoniacal nitrogen by nitrification was compromised, being 91.6% of the ammoniacal nitrogen removed by assimilation and only 0.35% removed by nitrification. At 400 mg phenol/L, the reactor provided COD and phenol average removals equal 88.6% and 80.9%, respectively. On the last day of operation, the removal of COD dropped to 55.4% and phenol removal was equal 49.0%. Novel microscopical evaluation of the MBBR's biofilm revealed some negative effects of the phenol on the microbiota composition.

Ultrafiltration ceramic membrane as oxidant-catalyst/water contactor to promote sulfate radical AOPs: a case study on 17ß-estradiol and 17α-ethinylestradiol removal.

This work highlights the performance of an ultrafiltration ceramic membrane as photocatalyst support and oxidant-catalyst/water contactor to promote sulfate radical advanced oxidation processes (SR-AOPs). Peroxydisulfate (PDS) activation mechanisms include photolysis (UVC irradiation) and chemical electron transfer (TiO2-P25 photocatalysis). The photoreactor is composed of an outer quartz tube (the "window"-radiation entrance to the reactor) and an inner tubular ceramic ultrafiltration membrane, where the catalyst particles (TiO2-P25) are immobilized on the membrane shell-side. PDS stock solution is fed by the lumen side of the membrane, delivering the oxidant to the catalyst particles and to the annular reaction zone (ARZ), being the catalyst and PDS activated by UV light. The design facilitates controlled radial slip of PDS into the catalyst surface and to concurrent water to be treated, flowing with a helix trajectory in the ARZ. Under continuous mode operation, with an UV fluence of 45 mJ cm-2 (residence time of 4.6 s), the UVC/PDS/TiO2 system showed the best removal efficiency for two specific endocrine disrupting chemicals, 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2), spiked (100 µg L-1 each) in demineralized water and urban wastewater after secondary treatment.

A tubular ceramic membrane coated with TiO2-P25 for radial addition of H2O2 towards AMX removal from synthetic solutions and secondary urban wastewater.

This work aims to integrate several hydrogen peroxide (H2O2) activation mechanisms, photolysis (UVC irradiation), chemical electron transfer (TiO2-P25 photocatalysis), and reaction with TiO2-P25 in dark conditions, for reactive oxygen species (ROS) generation towards the removal of contaminants of emerging concern (CECs), in a single unit operated in continuous-flow mode. An H2O2 stock solution is fed by the lumen side of a tubular ceramic membrane, delivering the oxidant to the (i) catalyst immobilized in the membrane shell-side and (ii) annular reaction zone (ARZ, space between membrane shell-side and outer quartz tube) where CECs contaminated water flows with a helix trajectory, being activated by UV light provided by four lamps placed symmetrically around the reactor. First, the effect of several parameters in the removal of a CEC target molecule, amoxicillin (AMX), was evaluated using a synthetic solution ([AMX]inlet = 2.0 mg L-1): (i) light source (UVA or UVC radiation), (ii) H2O2 dose, (iii) H2O2 injection method (radial permeation vs. upstream injection), and (iv) number of TiO2-P25 layers deposited on the membrane. The UVC/H2O2/TiO2 system with radial addition of H2O2 (20 mg L-1) and 9-TiO2-P25 layers provided the highest AMX removal efficiency (72.2 ± 0.5%) with a UV fluence of 45 mJ cm-2 (residence time of 4.6 s), due to the synergic effect of four mechanisms: (i) AMX photolysis, (ii) H2O2 photocleavage, (iii) TiO2-P25 photoactivation, and (iv) chemical reactions between H2O2 and TiO2-P25. The urban wastewater matrix showed a negative effect on AMX removal (~44%) due to the presence of ROS scavengers and light-filtering species.

Biodegradation of natural and synthetic endocrine-disrupting chemicals by aerobic granular sludge reactor: Evaluating estrogenic activity and estrogens fate.

In this study, the biodegradation of endocrine-disrupting chemicals (EDCs) (namely the natural and synthetic estrogens 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2), respectively) was assessed in an aerobic granular sludge (AGS) sequencing batch reactor (SBR) treating simulated domestic sewage. To better understand the fate of these compounds, their concentrations were determined in both liquid and solid (biomass) samples. Throughout the operation of the reactor, subjected to alternating anaerobic and aerated conditions, the removal of the hormones, both present in the influent at a concentration of 20 µg L-1, amounted to 99% (for E2) and 93% (for EE2), with the latter showing higher resistance to biodegradation. Through yeast estrogen screen assays, an average moderate residual estrogenic activity (0.09 µg L-1 EQ-E2) was found in the samples analysed. E2 and EE2 profiles over the SBR cycle suggest a rapid initial adsorption of these compounds on the granular biomass occurring anaerobically, followed by biodegradation under aeration. A possible sequence of steps for the removal of the micropollutants, including the key microbial players, was proposed. Besides the good capability of the AGS on EDCs removal, the results revealed high removal efficiencies (>90%) of COD, ammonium and phosphate. Most of the incoming organics (>80%) were consumed under anaerobic conditions, when phosphate was released (75.2 mgP L-1). Nitrification and phosphate uptake took place along the aeration phase, with effluent ammonium and phosphate levels around 2 mg L-1. Although nitrite accumulation took place over the cycle, nitrate consisted of the main oxidized nitrogen form in the effluent. The specific ammonium and phosphate uptake rates attained in the SBR were found to be 3.3 mgNH4+-N gVSS-1.h-1 and 6.7 mgPO43--P gVSS-1 h-1, respectively, while the specific denitrification rate corresponded to 1.0 mgNOx--N gVSS-1 h-1.

Electrochemical degradation of psychotropic pharmaceutical compounds from municipal wastewater and neurotoxicity evaluations.

Contaminants of emerging concern (CECs) are released daily into surface water, and their recalcitrant properties often require tertiary treatment. Electrochemical oxidation (EO) is often used as an alternative way to eliminate these compounds from water, although the literature barely addresses the neurotoxic effects of residual by-products. Therefore, this study investigated the performance of EO in the removal of five CECs (alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine) and performed neurotoxicity evaluations of residual EO by-products in Wistar rat brain hippocampal slices. Platinum-coated titanium (Ti/Pt) and boron-doped diamond (BDD) electrodes were studied as anodes. Different current densities (13-75 A m-2), pH values (3-10), electrolyte dosages (NaCl), and matrix effects were assessed using municipal wastewater (MWW). The drugs were successfully degraded after 5 min of reaction for both the Ti/Pt and BDD electrodes when a current density of 75 A m-2 was applied. For Ti/Pt and BDD, neutral and acidic pH demonstrated better CEC removal performance, respectively. Compound degradation using MWW achieved 40% removal after 120 min for Ti/Pt and ranged between 33 and 52% for the BDD anode. For Ti/Pt, neurotoxicity studies using MWW indicated a decrease in reactive oxygen species (ROS) signals. However, when an artificial cerebrospinal fluid (ACSF) medium was reapplied, the signal recovered and increased to a value above the baseline, indicating that cells recovered part of their normal activity but remained in a different condition. For the BDD anode, the treated MWW did not cause significant ROS production variations, suggesting that he EO was effective in eliminating the toxicity of the treated solution.

Synergism of ozonation and electrochemical filtration during advanced organic oxidation.

Here, we investigated the synergistic effect towards phenol degradation and mineralization between ozonation (O3) and electrochemical filtration (ECF) using perforated titanium as cathode and porous carbon nanotube (CNT) networks as anode. A flow rate of 1.6 mL min-1, 10 mM of sodium sulfate electrolyte, 1.0 mM of phenol (model aromatic compound), and an ozone dose of 12 mgO3 L-1 were used. Insight into the synergistic mechanism was achieved via carbon anode morphology characterization and phenol degradation kinetics analysis. Improved kinetic performance was observed for the combined process (O3-ECF) as compared to the sum of the individual processes, not only towards phenol degradation (3.2-fold increase), but also towards phenol mineralization (2.2-fold increase). Scanning electron microscopy revealed a significant decrease of polymer formation and deposition on CNT after the hybrid O3-ECF process as compared to the ECF alone. Voltage-dependent (0-2.5 V) ozone CNT functionalization was investigated at pH 7-11 to assist in elucidation of the synergistic mechanism. X-Ray photoelectron spectroscopy indicated increases up to 26-fold in CNT oxygen content post-ozonation at pH 7 comparing to fresh CNT. Various potential O3-ECF synergistic reaction mechanisms for organic aromatic oxidation and mineralization are discussed.

Removal of bromate from drinking water using a heterogeneous photocatalytic mili-reactor: impact of the reactor material and water matrix.

The main goal of this study was to evaluate the removal of bromate from drinking water using a heterogeneous photocatalytic mili-photoreactor, based on NETmix technology. The NETmix mili-reactor consists of a network of channels and chambers imprinted in a back slab made of acrylic (AS) or stainless steel (SSS) sealed, through mechanical compression and o-rings, with an UVA-transparent front borosilicate glass slab (BGS). A plate of UVA-LEDs was placed above the BGS window. TiO2-P25 thin films were immobilized on the BGS (back-side illumination, BSI) or SSS (front-side illumination, FSI) by using a spray deposition method. The photoreduction rate of a 200 µg L-1 (1.56 µM) BrO3- solution was assessed taking into account the following: (i) catalyst film thickness, (ii) catalyst coated surface and illumination mechanism (BSI or FSI), (iii) solution pH, (iv) type and dose of sacrificial agent (SA), (v) reactor material, and (vi) water matrix. In acidic conditions (pH 3.0) and in the absence of light/catalyst/SA, 28% and 36% of BrO3- was reduced into Br- only by contacting with AS and SSS during 2-h, respectively. This effect prevailed during BSI experiments, but not for FSI ones since back SSS was coated with the photocatalyst. The results obtained have demonstrated that (i) the molar rate of disappearance of bromates was similar to the molar rate of formation of bromides; (ii) higher BrO3- reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid ([BrO3-]:[CH2O2] molar ratio of 1:3) presented higher performance than humic acids (HA = 1 mg C L-1) as SA; (iv) high amounts of HA impaired the BrO3- photoreduction reaction; (v) SSS coated catalyst surface revealed to be stable for at least 4 consecutive cycles, keeping its photonic efficiency. Under the best operating conditions (FSI, 18 mL of 2% wt. TiO2-P25 suspension, pH 3.0), the use of freshwater matrices led to (i) equal or higher reaction rates, when compared with a synthetic water in the absence of SA, and (ii) lower reaction rates, when compared with a synthetic water containing formic acid with a [BrO3-]:[CH2O2] molar ratio of 1:3. Notwithstanding, heterogeneous TiO2 photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO3- into Br-, attaining concentrations below 10 µg L-1 (guideline value) after 2-h reaction. Graphical Abstract .

Development of an integrated treatment strategy for a leather tannery landfill leachate.

This study aimed at developing an efficient multistage treatment strategy for a complex industrial landfill leachate: a leather tannery landfill leachate. Based on the leachate physicochemical characteristics, the following treatment train was delineated and tested: (i) initial biological process for removal of biodegradable organics, ammonium and alkalinity, (ii) coagulation/flocculation process for total removal of chromium and partial removal of recalcitrant organics and suspended solids, (iii) advanced oxidation process (AOP) or electrochemical AOP (EAOP) for degradation of recalcitrant organics and biodegradability enhancement, and (iv) final biological polishing step. Two initial biological treatment configurations were applied: one comprising nitrification and the other nitrification-denitrification. Coagulation/flocculation was optimized in terms of pH, coagulant dosage (iron(III) chloride) and flocculant nature and dosage. The following AOPs/EAOPs were tested: Fenton, photo-Fenton with UVA or UVC radiation (PF-UVA or PF-UVC), anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton with UVA radiation (PEF-UVA). The biological nitrification-denitrification was beneficial not only because it avoided the need for alkalinity addition during nitrification and decreased the amount of substrate added during denitrification, as expected. Over and above that, it reduced the acid consumption in the coagulation/flocculation, avoided the application of an additional stage comprising nitrites oxidation to nitrates prior to the AOP/EAOP, and improved the efficiency of Fenton's reaction based processes. Following nitrification-denitrification, the coagulation/flocculation was maximized at pH 3.0 and 400 mg Fe L-1 with no flocculant addition. The PEF-UVA process was the best AOP/EAOP. The final leachate fulfilled the discharge limits into waterbodies.

Insights into estrogenic activity removal using carbon nanotube electrochemical filter.

This study reports the performance of a carbon nanotube (CNT) electrochemical filter applied to 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2) degradation and their estrogenic activity removal (calculated in terms of E2 equivalent, EQ-E2). The performance of CNT electrochemical filter was assessed at different applied voltages (0-2.5 V) and aqueous matrices (ultrapure water and urban wastewater), using 37 µM of E2 and EE2, a flow rate of 1.5 mL min-1 and 10 mM of Na2SO4, used as supporting electrolyte. Surface characterization of CNT anodic filters was completed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) was used to investigate electron transfer mechanisms. The CNT electrochemical filter was successfully applied to E2 and EE2 degradation and removals higher than 95.3% (oxidative fluxes >2.94 ±â€¯0.05 mmol h-1 m-2) were achieved when 2.5 V was applied for both ultrapure water and urban wastewater. CV results indicate that the oxidation in the CNT electrochemical filter is an irreversible process. SEM and XPS results showed evidence of the polymer formation on the CNT surface after 300 min of reaction, which probably reduced the efficiency of the process under low applied voltages. Estrogenic activity was considerably reduced and minimal EQ-E2 levels were observed when 2.5 V was applied. A residual EQ-E2 was observed, likely due to the presence of estrogens, which suggests the non-formation of estrogenic intermediates. At 2.5 V total cell potential, the energy required to remove estrogenic activity was 0.014 ±â€¯0.001 kWh m-3 for ultrapure water and 0.021 ±â€¯0.001 kWh m-3 for post-secondary wastewater. These results suggest a CNT electrochemical filter may have potential to effectively and efficiently remove estrogenic activity and may be a feasible process for wastewater polishing treatment.

Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes.

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A, using sunlight and artificial irradiation. While using TiO2 in suspension, best results were found at [TiO2] = 0.1 g L-1. H2O2/UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO2/UV-A and H2O2/UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H2O2/UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO2-photocatalysis.

Tratamento de lixiviado por processos combinados: coagulação/floculação, air stripping, ozonização e lodo ativado / Leachate treatment by combined processes: coagulation/flocculation, air stripping, ozonation and activated sludge

RESUMO Os lixiviados de áreas de disposição de resíduos municipais apresentam, em geral, alta complexidade, variabilidade, toxicidade, recalcitrância e alta concentração de nitrogênio amoniacal. Neste estudo, aplicaram-se técnicas combinadas para o tratamento de um lixiviado, a saber: coagulação/floculação (C/F), air stripping e ozonização, combinados com o tratamento por lodo ativado com/sem inserção de carvão ativado. O processo de C/F levou a uma redução na demanda química de oxigênio (DQO) de 58,1% e na cor, de 85,6%. O air stripping foi realizado em pH>12 e obteve-se diminuição dos níveis de nitrogênio amoniacal para abaixo de 60 mg.L-1. O processo de ozonização, com consumo de ozônio de 397 mgO3.L-1 e 2.376 mgO3.L-1, apresentou bons resultados, com aumento de 59,4% na relação DBO5/DQO e uma redução de toxicidade superior a 85%. Obteve-se melhor eficiência para o lodo ativado sem carvão ativado, com lixiviado pré-tratado por C/F + air stripping + ozonização (400 mgO3.L-1). Tal combinação resultou em uma redução de 90,6% na DQO do lixiviado e mais de 99% nos níveis de nitrogênio amoniacal.

ABSTRACT Leachate from waste disposal areas generally presents high complexity, variability, toxicity, recalcitrance and high concentration of ammonia nitrogen. In this work, combined techniques for the treatment of leachate were applied, namely: coagulation/flocculation, air stripping and ozonation combined with activated sludge treatment with/without activated carbon. The coagulation/flocculation process led to a COD reduction of 58.1% and color removal of 85.6%. The air stripping was performed at pH>12 and reduced ammonia levels below of 60 mg.L-1. The ozonation process (ozone consumption of 397 mgO3.L-1 and 2376 mgO3.L-1) presented good results. It was observed a BOD5/COD increase of 59.4% and a toxicity reduction of more than 85%. The best efficiency was observed with sludge activated without activated carbon for the pre-treated leachate by coagulation/flocculation + air stripping + ozonation (400 mgO3.L-1). This combination resulted in a COD reduction of 90.6% and more than 99% of ammonia nitrogen removal.

Fluorene oxidation by solar-driven photo-Fenton process: toward mild pH conditions.

Polycyclic aromatic hydrocarbons (PAHs) are on the list of priority pollutants to be eliminated from the environment due to their carcinogenic and mutagenic action, chemical stability, and resistance to biodegradation. The aim of this study was to evaluate the degradation of fluorene, a well-known PAH, in aqueous solutions (0.03 and 0.08 mg L-1), by means of a solar-driven conventional (PF) and modified photo-Fenton mediated by ferrioxalate complexes (PFF). Photolysis was also employed for comparison purposes. PF reaction was evaluated at different pH values (2.8, 3.5, and 4.0) and iron concentrations (2, 5, 10, and 20 mg L-1). On the other hand, PFF studies were conducted at mild pH conditions (4.0, 5.0, and 6.0) and iron content of 2 mg L-1, keeping initial iron/oxalate molar ratio at 1:3. In both PF and PFF, the initial hydrogen peroxide/iron molar ratio was maintained at 5. In the presence of methanol as cosolvent for fluorene dissolution, the PF reaction was hampered and no consumption of H2O2 was observed during the reaction carried out at constant pH (2.8). This led to low degradation rates, similar to those achieved by photolysis. Under the same pH but using acetonitrile as cosolvent for fluorene dissolution, fluorene degradation was found to be proportional to the iron content used in the PF experiments. On the other hand, at an invariable iron concentration of 5 mg Fe2+ L-1, the increase in pH was accompanied by a decrease in the molar fraction of the most photoactive iron complex (FeOH2+) and ferric hydroxides precipitation, leading to a reduction in the fluorene degradation rate. With regard to the PFF tests, similar fluorene degradation performance was achieved at pH 4 and 5, while at pH 6 iron precipitation became relevant and the degradation rate was slightly slower. PFF has shown to be more efficient than the PF under the same pH (4) and iron concentration (2 mg L-1). Moreover, even at near neutral pH (6), fluorine degradation was shown to be feasible by using ferrioxalate complexes.

A facile method to prepare translucent anatase thin films in monolithic structures for gas stream purification.

In the present work, a facile method to prepare translucent anatase thin films on cellulose acetate monolithic (CAM) structures was developed. A simple sol-gel method was applied to synthesize photoactive TiO2 anatase nanoparticles using tetra-n-butyl titanium as precursor. The immobilization of the photocatalyst on CAM structures was performed by a simple dip-coating method. The translucent anatase thin films allow the UV light penetration through the CAM internal walls. The photocatalytic activity was tested on the degradation of n-decane (model volatile organic compound-VOC) in gas phase, using a tubular lab-scale (irradiated by simulated solar light) and pilot-scale (irradiated by natural solar light or UVA light) reactors packed with TiO2-CAM structures, both equipped with compound parabolic collectors (CPCs). The efficiency of the photocatalytic oxidation (PCO) process in the degradation of n-decane molecules was studied at different operating conditions at lab-scale, such as catalytic bed size (40-160 cm), TiO2 film thickness (0.435-0.869 µm), feed flow rate (75-300 cm3 min-1), n-decane feed concentration (44-194 ppm), humidity (3 and 40%), oxygen concentration (0 and 21%), and incident UV irradiance (18.9, 29.1, and 38.4 WUV m-2). The decontamination of a bioaerosol stream was also evaluated by the PCO process, using Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) as model bacteria. A pilot-scale unit was operated day and night, using natural sunlight and artificial UV light, to show its performance in the mineralization of n-decane air streams under real outdoor conditions. Graphical abstract Normally graphics abstract are not presented with captions/legend. The diagram is a collection of images that resume the work.

Photo-Fenton oxidation of 3-amino-5-methylisoxazole: a by-product from biological breakdown of some pharmaceutical compounds.

The present study aims to assess the removal of 3-amino-5-methylisoxazole (AMI), a recalcitrant by-product resulting from the biological breakdown of some pharmaceuticals, applying a solar photo-Fenton process assisted by ferrioxalate complexes (SPFF) (Fe3+/H2O2/oxalic acid/UVA-Vis) and classical solar photo-Fenton process (SPF) (Fe2+/H2O2/UVA-Vis). The oxidation ability of SPFF was evaluated at different iron/oxalate molar ratios (1:3, 1:6, and 1:9, with [total iron] = 3.58 × 10-2 mM and [oxalic acid] = 1.07 × 10-1, 2.14 × 10-1 and 3.22 × 10-1 mM, respectively) and pH values (3.5-6.5), using low iron contents (2.0 mg Fe3+ L-1). Additionally, the use of other organic ligands such as citrate and ethylenediamine-N,N'-disuccinic acid (EDDS) was tested. The oxidation power of the classical SPF was assessed at different pH values (2.8-4.0) using 2.0 mg Fe2+ per liter. Furthermore, the effect of AMI concentration (2-20 mg L-1), presence of inorganic ions (Cl-, SO42-, NO3-, HCO3-, NH4+), and radical scavengers (sodium azide and D-mannitol) on the SPF method at pH 3.5 was also assessed. Experiments were done using a lab-scale photoreactor with a compound parabolic collector (CPC) under simulated solar radiation. A pilot-scale assay was conducted using the best operation conditions. While at near neutral pH, an iron/oxalate molar ratio of 1:9 led to the removal of 72 % of AMI after 90 min of SPFF, at pH 3.5, an iron/oxalate molar ratio of 1:3 was enough to achieve complete AMI degradation (below the detection limit) after 30 min of reaction. The SPF process at pH 3.5 underwent a slower AMI degradation, reaching total AMI degradation after 40 min of reaction. The scale up of SPF process showed a good reproducibility. Oxalic and oxamic acids were identified as the main low-molecular-weight carboxylic acids detected during the pilot-scale SPF reaction. Graphical abstract ᅟ.

Bacteria and fungi inactivation by photocatalysis under UVA irradiation: liquid and gas phase.

In the last decade, environmental risks associated with wastewater treatment plants (WWTPs) have become a concern in the scientific community due to the absence of specific legislation governing the occupational exposure limits (OEL) for microorganisms present in indoor air. Thus, it is necessary to develop techniques to effectively inactivate microorganisms present in the air of WWTPs facilities. In the present work, ultraviolet light A radiation was used as inactivation tool. The microbial population was not visibly reduced in the bioaerosol by ultraviolet light A (UVA) photolysis. The UVA photocatalytic process for the inactivation of microorganisms (bacteria and fungi, ATCC strains and isolates from indoor air samples of a WWTP) using titanium dioxide (TiO2 P25) and zinc oxide (ZnO) was tested in both liquid-phase and airborne conditions. In the slurry conditions at liquid phase, P25 showed a better performance in inactivation. For this reason, gas-phase assays were performed in a tubular photoreactor packed with cellulose acetate monolithic structures coated with P25. The survival rate of microorganisms under study decreased with the catalyst load and the UVA exposure time. Inactivation of fungi was slower than resistant bacteria, followed by Gram-positive bacteria and Gram-negative bacteria. Graphical abstract Inactivation of fungi and bacteria in gas phase by photocatalitic process performed in a tubular photoreactor packed with cellulose acetate monolith structures coated with TiO2.

Treatment of a simulated textile wastewater containing the Reactive Orange 16 azo dye by a combination of ozonation and moving-bed biofilm reactor: evaluating the performance, toxicity, and oxidation by-products.

In this study, an aqueous solution containing the azo dye Reactive Orange 16 (RO16) was subjected to two sequential treatment processes, namely: ozonation and biological treatment in a moving-bed biofilm reactor (MBBR). The most appropriate ozonation pretreatment conditions for the biological process and the toxicity of the by-products resulting from RO16 ozone oxidation were evaluated. The results showed that more than 97 % of color removal from the dye solutions with RO16 concentrations ranging from 25 to 100 mg/L was observed in 5 min of ozone exposure. However, the maximum total organic carbon removal achieved by ozonation was only 48 %, indicating partial mineralization of the dye. Eleven intermediate organic compounds resulting from ozone treatment of RO16 solution were identified by LC/MS analyses at different contact times. The toxicity of the dye-containing solution decreased after 2 min of ozonation, but increased at longer contact times. The results further demonstrated that the ozonolysis products did not affect the performance of the subsequent MBBR, which achieved an average chemical oxygen demand (COD) and ammonium removal of 93 ± 1 and 97 ± 2 %, respectively. A second MBBR system fed with non-ozonated dye-containing wastewater was run in parallel for comparison purposes. This reactor also showed an appreciable COD (90 ± 1 %) and ammonium removal (97 ± 2 %), but was not effective in removing color, which remained practically invariable over the system. The use of short ozonation times (5 min) and a compact MBBR has shown to be effective for the treatment of the simulated textile wastewater containing the RO16 azo dye.

Photocatalytic processes assisted by artificial solar light for soil washing effluent treatment.

Contaminated soil has become a growing issue in recent years. The most common technique used to remove contaminants (such as metals) from the soil is the soil washing process. However, this process produces a final effluent containing chelating agents (i.e., ethylenediaminedisuccinic acid, also known as EDDS) and extracted metals (i.e., Cu, Fe, and Zn) at concentrations higher than discharge limits allowed by the Italian and Brazilian environmental law. Therefore, it is necessary to develop further treatments before its proper disposal or reuse. In the present study, soil washing tests were carried out through two sequential paths. Moreover, different artificial sunlight-driven photocatalytic treatments were used to remove Cu, Zn, Fe, and EDDS from soil washing effluents. Metal concentrations after the additional treatment were within the Brazilian and Italian regulatory limits for discharging in public sewers. The combined TiO2-photocatalytic processes applied were enough to decontaminate the effluents, allowing their reuse in soil washing treatment. Ecotoxicological assessment using different living organisms was carried out to assess the impact of the proposed two-step photocatalytic process on the effluent ecotoxicity. Graphical Abstract ᅟ.

Removal of recalcitrant organic matter content in wastewater by means of AOPs aiming industrial water reuse.

This paper comes out from the need to provide an improvement in the current oil refinery wastewater treatment plant (WWTP) aiming to generate water for reuse. The wastewater was pretreated and collected in the WWTP after the biological treatment unit (bio-disks) followed by sand filtration. Ozonation (ozone concentration from 3.0-60 mgO3 L-1), UV (power lamp from 15 to 95 W), H2O2 (carbon:H2O2 molar ratio of 1:1, 1:2, and 1:4), and two advanced oxidation processes (UV/O3 and UV/H2O2) were investigated aiming to reduce the wastewater organic matter and generate water with suitable characteristics for the reverse osmosis operation and subsequent industrial reuse. Even after the biological and filtration treatments, the oil refinery wastewater still presented an appreciable amount of recalcitrant organic matter (TOC of 12-19 mgC L-1) and silt density index (SDI) higher than 4, which is considered high for subsequent reverse osmosis due to membrane fouling risks. Experiments using non combined processes (O3, H2O2, and UV only) showed a low degree of mineralization after 60 min of reaction, although the pretreatment with ozone had promoted the oxidation of aromatic compounds originally found in the real matrix, which suggests the formation of recalcitrant compounds. When the combined processes were applied, a considerable increase in the TOC removal was observed (max of 95 % for UV/O3 process, 55 W, 60 mgO3 L-1), likely due the presence of higher amounts of reactive species, specially hydroxyl radicals, confirming the important role of these species on the photochemical degradation of the wastewater compounds. A zero-order kinetic model was fitted to the experimental data and the rate constant values (k, mgC L-1 h-1) ranged from 4.8 < k UV/O3 < 11 ([O3]0 = 30-60 mg L-1), and 8.6 < k UV/H2O2 < 11 (C:H2O2 from 1:1 to 1:4). The minimum and maximum electrical energy per order (E EO) required for 60 min of treatment were calculated as 5.4 and 81 Wh L-1, respectively, for UV/O3 (15 W, 60 mgO3 L-1) and UV/H2O2 (95 W, 1C:1H2O2). Good results in terms of water conditioning for reverse osmosis operation were obtained using UV/H2O2 process with initial molar ratio of 1 C:2 H2O2 (UV lamp 55 W) and 1 C:4 H2O2 (UV lamp 95 W), and total organic carbon (TOC) removals of 62 % (SDI15 = 1.8) and 74 % (SDI15 = 2.0) were achieved, respectively, after 60 min. The treated wastewater followed to the reverse osmosis system, which operated with an adequate flux of permeate, was very efficient to remove salt and generate a permeate water with the required quality for industrial reuse.

Treatment of an industrial stream containing vinylcyclohexene by the H2O2/UV process.

Petrochemical industries generate wastewaters containing pollutants that can severely impact the biological treatment systems. Some streams from specific production units may contain nonbiodegradable or toxic compounds that impair the performance of the wastewater treatment plant and should be segregated and treated by specific techniques. In this work, the utilization of chemical oxidation (H2O2/UV) was investigated for removing 4-vinylcyclohexene (VCH) from a liquid stream coming from the production of hydroxylated liquid polybutadiene (HLPB). Besides VCH, this stream also contains ethanol, hydrogen peroxide, and many other organic compounds. Experiments were carried out in a small-scale photochemical reactor (0.7 L) using a 25-W low-pressure mercury vapor lamp. The photochemical reactor was operated in batch, and the reaction times were comprised between 10 and 60 min. Assays were also performed with a synthetic medium containing VCH, H2O2, and ethanol to investigate the removal of these substances in a less complex aqueous matrix. By-products formed in the reaction were identified by gas chromatography and mass spectroscopy (GC-MS). VCH was significantly removed by the oxidation process, in most assays to undetectable levels. Ethanol removal varied from 16 to 23 % depending on the reaction conditions. Acetic acid, acetaldehyde, and diols were detected as by-products of the industrial wastewater stream oxidation. A drop on the toxicity of the industrial stream was also observed in assays using the organism Artemia salina.

Analysis of estrogenic activity in environmental waters in Rio de Janeiro state (Brazil) using the yeast estrogen screen.

The estrogenicity of waters collected from an important hydrological system in Brazil (Paraiba do Sul and Guandu Rivers) was assessed using the yeast estrogen screen (YES) assay. Sampling was performed in rivers and at the outlets of conventional water treatment plants (WTP). The removal of estrogenic activity by ozonation and chlorination after conventional water treatment (clarification and sand filtration) was investigated employing samples of the Guandu River spiked with estrogens and bisphenol A (BPA). The results revealed a preoccupying incidence of estrogenic activity at levels higher than 1ngL(-1) along some points of the rivers. Another matter of concern was the number of samples from WTPs presenting estrogenicity surpassing 1ngL(-1). The oxidation techniques (ozonation and chlorination) were effective for the removal of estrogenic activity and the combination of both techniques led to good results using less amounts of oxidants.