Enhanced bioremediation of oil-contaminated soil in a slurry bioreactor by H2O2-stimulation of oil-degrading/biosurfactant-generating bacteria: performance optimization and bacterial metagenomics.

Oil-contaminated soil is the main challenge for oil-rich countries, and this study aimed to investigate the performance of the H2O2-stimulated slurry bioreactor for the bioremediation of real oil-contaminated soil. The effect of biomass concentration, soil to water (S/W) ratio, slurry temperature, pH, and H2O2 concentration were optimized for the removal of total petroleum hydrocarbons (TPH) from oil-contaminated soil. TPH removal efficiency, biosurfactants production, and peroxidase and dehydrogenase activities were measured. The optimum conditions for the complete biodegradation of 32 [Formula: see text] in the slurry bioreactor during 6 days were biomass of 2250 mg/L, S/W ratio of 20%, the temperature of 30 °C, pH of 7, and an H2O2 concentration of 120 mg/L. The highest peroxidase, dehydrogenase, surfactin, and rhamnolipid formation were also obtained under optimum conditions. The results pointed out that complete biodegradation of 32 g/kg of TPH in oil-contaminated soil at a short reaction time of 6 days is achievable in the developed process operated under optimum conditions. The GC/FID analysis of solid and liquid phases showed that the bioprocess completely biodegraded the different TPH fractions. H2O2 efficiently stimulated the biosurfactant-generating bacteria to produce peroxidase and thereby accelerating the bioremediation rate. Accordingly, an H2O2-mediated slurry bioreactor inoculated with biosurfactant/peroxidase-generating bacteria is a promising technique for cleaning up oil-contaminated soils.

Enhanced treatment of the oil-contaminated soil using biosurfactant-assisted washing operation combined with H2O2-stimulated biotreatment of the effluent.

A real crude oil-contaminated soil was treated using a two-step method: biosurfactant-assisted soil washing and the biostimulated biotreating of the effluent. The mixture of surfactin and rhamnolipid could enhance the TPH removal from an oil-contaminated soil (32 g/kg) in the soil washing operation. 86% of TPH was removed from the oil-contaminated soil in the soil washing operation under the mixed biosurfactant (surfactin + rhamnolipid) of 0.6 g/L, the soil/water ratio of 20 w/v%, the temperature of 30 °C, and the washing time of 24 h, leaving an effluent containing 5028 mg/L TPH. The effluent was efficiently biotreated in the bioprocess with 5 g/L acclimate biomass daily stimulated with 0.1 mM H2O2, and the concentrtion of TPH decreased to 26 mg/L within 17 d corresponding a TPH biodegradation over 99%. The biostimulation with H2O2 caused the production of a high amount of peroxidase that could accelerate the biodegradation of TPH. Accordingly, the findings suggest that the biosurfactant-assisted washing operation combined with the H2O2-stimulated biodegradation process could be an enhanced green method for efficient treatment of the heavy oil-contaminated soils.

A modeling concept on removal of VOCs in wire-tube non-thermal plasma, considering electrical and structural factors.

In this study, benzene was selected as an indicator of VOCs, and a modeling procedure was carried out on benzene removal (outflow concentration of benzene, C/inflow concentration of benzene, C0), in DC and AC non-thermal plasma systems. Different diameters (18, 23, and 36 mm) of wire-tube plasma reactors were prepared, and models were raised based on the results of experiments with influencing factors of the used voltage, gap size inside the reactor, current density, and specific energy. The results showed correlation between the factors and benzene removal in both DC and AC discharge non-thermal plasma. The applied voltage as an electrical factor had negative correlation with C/C0, and the correlation was stronger than for gap size which was positively correlated with C/C0. Current density and specific energy were affected by the voltage and gap size of the reactor; the lowest C/C0 values were obtained in the highest values of specific energy and current density. Regarding the raised models, multi-factor exponential model was the most reliable one with the results.

The catalytic destruction of antibiotic tetracycline by sulfur-doped manganese oxide (S-MgO) nanoparticles.

The present study evaluates the efficacy of S-doped MgO (S-MgO) as compared with the plain MgO as a catalyst for destructive removal of tetracycline (TTC) in aqueous solutions. The S-MgO had around 6% S in its structure. Doping MgO with S caused increase in surface oxygen vacancy defects. Adding S-MgO (12 g/L) to a TTC aqueous solution (50 mg/L) caused removal of around 99% TTC at the neutral pH (ca. 5.1) and a short reaction time of 10 min. In comparison, plain MgO could remove only around 15% of TTC under similar experimental conditions. Diffusing O2 into the TTC solution under the reaction with S-MgO resulted in a considerable improvement of TTC removal as compared to diffusing N2. Complete removal of TTC and 86.4% removal of its TOC could be obtained using 2 g/L S-MgO nanoparticles. The removal of TTC increased with the increase in solution temperature. The presence of nitrate, sulfate and chloride did not considerably affect the removal of TTC using S-MgO while TTC removal significantly decreased at the presence of bicarbonate and phosphate. The S-MgO was a stable and reusable catalyst exhibiting much higher catalytic activity than plain MgO for the TTC destruction. Accordingly, S-MgO is an emerging and efficient catalyst for catalytic decomposition and mineralization of such pharmaceutical compounds as TTC under atmospheric temperature and pressure.

Homogenous VUV advanced oxidation process for enhanced degradation and mineralization of antibiotics in contaminated water.

This study was aimed to evaluate the degradation and mineralization of amoxicillin(AMX), using VUV advanced process. The effect of pH, AMX initial concentration, presence of water ingredients, the effect of HRT, and mineralization level by VUV process were taken into consideration. In order to make a direct comparison, the test was also performed by UVC radiation. The results show that the degradation of AMX was following the first-order kinetic. It was found that direct photolysis by UVC was able to degrade 50mg/L of AMX in 50min,while it was 3min for VUV process. It was also found that the removal efficiency by VUV process was directly influenced by pH of the solution, and higher removal rates were achieved at high pH values.The results show that 10mg/L of AMX was completely degraded and mineralized within 50s and 100s, respectively, indicating that the AMX was completely destructed into non-hazardous materials. Operating the photoreactor in contentious-flow mode revealed that 10mg/L AMX was completely degraded and mineralized at HRT values of 120s and 300s. it was concluded that the VUV advanced process was an efficient and viable technique for degradation and mineralization of contaminated water by antibiotics.

Anoxic biodegradation of petroleum hydrocarbons in saline media using denitrifier biogranules.

The total petroleum hydrocarbons (TPH) biodegradation was examined using biogranules at different initial TPH concentration and contact time under anoxic condition in saline media. The circular compact biogranules having the average diameter between 2 and 3mm were composed of a dense population of Bacillus spp. capable of biodegrading TPH under anoxic condition in saline media were formed in first step of the study. The biogranules could biodegrade over 99% of the TPH at initial concentration up to 2g/L at the contact time of 22h under anoxic condition in saline media. The maximum TPH biodegradation rate of 2.6 gTPH/gbiomass.d could be obtained at initial TPH concentration of 10g/L. Accordingly, the anoxic biogranulation is a possible and promising technique for high-rate biodegradation of petroleum hydrocarbons in saline media.

Investigation of furfural biodegradation in a continuous inflow cyclic biological reactor.

The performance of a continuous inflow cyclic biological reactor (CBR) containing moving media was investigated for the degradation of high concentrations of furfural. The effects of hydraulic retention time (HRT) and furfural initial concentrations (loading rate), as main operating parameters, on the bioreactor performance were studied. The results indicated that the CBR could remove over 98% of furfural and 71% of its chemical oxygen demand (COD) at inlet furfural concentrations up to 1,200 mg L(-1) (2.38 g L(-1) d(-1)), a 6-h cycle time and HRT of 12.1 h. The removal efficiency decreased slightly from 98 to 94% when HRT decreased from 12.1 to 10.5 h. The average removal efficiency of furfural and COD during the 345-day operational period under steady-state conditions were 97.7% and 82.1%, respectively. The efficiency also increased approximately 17.2% after addition of synthetic polyurethane cubes as moving media at a filling ratio of 10%.

Degradation and COD removal of catechol in wastewater using the catalytic ozonation process combined with the cyclic rotating-bed biological reactor.

The effect of ozonation catalyzed with MgO/granular activated carbon (MgO/GAC) composite as a pretreatment process on the performance of cyclic rotating-bed biological reactor (CRBR) for the catechol removal from wastewater has been investigated. CRBR with acclimated biomasses could efficiently remove catechol and its related COD from wastewater at organic loading rate (OLR) of 7.82 kg COD/m(3).d (HRT of 9 h). Then, OLR increased to 15.64 kg COD/m(3).d (HRT of 4.5 h) and CRBR failed. Catalytic ozonation process (COP) used as a pre-treatment and could improve the performance of the failed CRBR. The overall removal efficiency of the combined process attained respective steady states of 91% and 79% for degradation and COD removal of catechol. Therefore, the combined process is more effective in degradation and COD removal of catechol; it is also a viable alternative for upgrading industrial wastewater treatment plant.

Simultaneous removal of microplastics and benzalkonium chloride using electrocoagulation process: statistical modeling and techno-economic optimization.

Microplastics and benzyldimethyldodecylammonioum chloride (DDBAC) enter the environment more frequently during the COVID-19 pandemic and their co-occurrence will be a potential threat to the environment in the post-pandemic era. This study investigates the performance of an electrochemical system for the simultaneous removal of microplastics and DDBAC. During experimental studies, effects of applied voltage (3-15 V), pH (4-10), time (0-80 min), electrolyte concentration (0.01-0.0.09 M), electrode configuration, and perforated anode were investigated to identify their influence on DDBAC and microplastics removal efficiency. Eventually, the techno-economic optimization yielded to evaluate the commercial feasibility of this process. The central composite design (CCD) and analysis of variance (ANOVA) are employed for evaluation and optimization of the variables and response, DDBAC-microplastics removal, and for determining the adequacy and significance of mathematical models proposed by response surface methodology (RSM). Experimental results indicate that optimum conditions are pH = 7.4, time = 80 min, electrolyte concentration = 0.05 M, and applied voltage = 12.59, in which the removal of microplastics, DDBAC, and TOC reached the maximum level, which was 82.50%, 90.35%, and 83.60% respectively. The results confirm that the valid model is adequately significant for the target response. Overall, financial and energy consumption analyses confirmed that this process is a promising technology as a commercial method for the removal of DDBAC-microplastics complexes in water and wastewater treatment.

Microplastics and mesoplastics as emerging contaminants in Tehran landfill soils: The distribution and induced-ecological risk.

Environmental pollution with microplastics (MPs) and mesoplastics (MEPs) and their potential risks to human health and ecosystem quality have aroused the concern of communities. Therefore, the pioneering study was conducted on Tehran landfill soil contamination with MPs and MEPs. 56 shallow and deep soil samples were collected from different landfill areas in the wet and dry seasons. The physical and chemical characteristics of MPs and MEPs were measured using a stereomicroscope and FTIR-ATR spectroscopy, respectively. The results showed that the average MP abundance in shallow and deep soil was 863 ± 681 and 225 ± 138 particles/kg soil, and for MEPs, it was 29.8 ± 6.4 and 18.1 ± 8.3 particles/kgsoil. The low-density plastic particles were separated completely by flotation with H2O, NaCl, and ZnCl2 solutions, but PVC was only separated by 90%. Over 90% of MPs and MEPs were LDPE, PP, and PS polymers, explained by their widespread applications in single-use products and their consumption in Iran. Films, white and black, and 0.1-0.5 mm were the dominant shapes, colors, and sizes of MPs, respectively. The prevailing MEPs were film-shaped and in white and yellow colors, with a size of 0.5-1.0 cm. Canonical correlation analysis indicated that total organic matter and moisture were highly correlated with MP shapes. The calculated polymer hazard index values have a wide range at different sampling points, and this index yielded hazard levels III-IV and II-IV for MPs and MEPs, respectively, while according to the pollution load index category, the hazard level of MPs and MEPs was I-II and I. The potential ecological risk index from combined polymers has been estimated to be of minor to extreme danger for MPs and of minor risk for MEPs. Our findings provided baseline data on MPs contamination in Tehran landfill soil and its associated ecological risk, which aids policymakers in implementing risk-reduction measures.

Removal of petroleum hydrocarbons from contaminated groundwater by the combined technique of adsorption onto perlite followed by the O3/H2O2 process.

Groundwater contaminated with petroleum hydrocarbons was treated using a combined system of adsorption onto powdered expanded perlite (PEP) followed by the O3/H2O2 process. The pretreatment investigations indicated a high capacity for PEP to remove petroleum hydrocarbons from the contaminated water. An experimental total petroleum hydrocarbon (TPH) adsorption capacity of 275 mg/g PEP was obtained at the natural pH of water. The experimental data fit best with the Freundlich isotherm model and pseudo-second-order adsorption model. The second phase of the experiment evaluated the performance of the O3/H2O2 process in the removal of residual TPH from pretreated water and compared the results with that of raw water. The O3/H202 process attained a maximum TPH removal rate for the pretreated water after 70 min, when 93% of the residual TPH in the effluent of the adsorption system was removed. Overall, the combination of adsorption onto PEP for 100 min and the subsequent treatment with the O3/H2O2 process for 70min eliminated over 99% of the TPH of highly petroleum-contaminated groundwater, with initial values of 162 mg/L. Therefore, we can conclude that the developed treatment system is an appropriate method of remediation for petroleum-contaminated waters.

Vacuum UV pre-treatment coupled with self-generated peroxide stimulation of biomass: An innovative hybrid system for detoxification and mineralization of toxic compounds.

The degradation of p-nitrophenol (pNP) was investigated in the chemical-less UVC/VUV process (Advanced Oxidation/Reduction Process, AORP), the packed bed bioreactor (PBR), and the hybrid of AORP/PBR system. The control UVC/VUV process degraded and mineralized pNP with rate constants of 0.098 and 0.032 min-1, respectively, at neutral initial pH. Operating the UVC/VUV process in a fluidized bed reactor improved the rate of pNP degradation by 21 % at a packing ratio of 0.5 %. The fluidized bed AORP was operated under continuous-flow mode, where 79 % degradation and 28 % mineralization of pNP were obtained along a significant improvement in the biodegradability (41 %) at a hydraulic retention time of 20 min. The oxidation with HO and reduction with eaq- simultaneously contributed to the degradation of pNP in the UVC/VUV process. In comparison, degradation and mineralization of pNP in a single PBR process (without pretreatment) was found to be 84.7 % and 47.2 %, respectively, during 30 h biotreatment. Coupling the fluidized bed UVC/VUV with the PBR attained complete biodegradation of the residual pNP within 1 h and over 89 % of TOC reduction during 3 h post treatment in the PBR. Accordingly, the hybrid, fluidized bed UVC/VUV reactor coupled with the PBR is an efficient and promising technology for treating toxic environmental contaminants.

Biodegradation of the petroleum hydrocarbons using an anoxic packed-bed biofilm reactor with in-situ biosurfactant-producing bacteria.

The present study employed an anoxic packed bed biofilm reactor (AnPBR) inoculated with in-situ biosurfactant-producing bacteria for the biodegradation of petroleum wastewater. Highly acclimated biomass decreased the start-up phase period and with increasing the initial total petroleum hydrocarbon (TPH) concentration from 1.5 to 4 g/L was accompanied by TPH and chemical oxygen demand (COD) removal efficiencies of above 99% and 96%, respectively. Decreasing hydraulic retention time (HRT) from 24 to 6 h caused an increase in the specific hydrocarbon utilization rate value from 0.45 to 1.66 gTPH/gbiomass.d. Moreover, dehydrogenase activity, surfactin, and rhamnolipid reached 31.8 µgTF/gbiomass.d, 95.1, and 27.1 mg/L, respectively. The biodegradation kinetic coefficients such as K, Ks, Kd, Y and µmax were 0.784 (d-1), 0.005 (g/L), 0.138 (d-1), 0.569 (gVSS/gCOD), and 0.446 (d-1), respectively. Dropping of bioreactor performance, especially TPH removal efficiency from 99% to 37.6% in the absence of nitrate after 10 days, indicates anoxic metabolism has been the dominant biodegradation pathway. The effluent chromatogram of gas chromatography/flame ionization detector (GC/FID) showed aliphatic, cyclic aliphatic, and aromatic hydrocarbons efficiently degraded. According to the high degradation rate of AnPBR in different operational parameters, it can be recommended for the treatment of oil-contaminated wastewater.

The efficacy of the VUV/O3 process run in a continuous-flow fluidized bed reactor for simultaneous elimination of favipiravir and bacteria in aqueous matrices.

The efficacy of the Vacuum UV/Ozonation (VUV/O3) process was evaluated for the degradation of favipiravir (FAV). It was found that coupling O3 and VUV resulted in a considerable synergistic catalytic effect on FAV removal. The VUV/O3 process performed better in moderately alkaline conditions than in acidic ones; complete FAV degradation and 99.4% TOC removal were achieved within 10 and 60 min, respectively. HO• played the dominant role in FAV degradation, with a second-order reaction rate constant with HO• at 1.05 × 1010 M-1 s-1. The VUV/O3 process could effectively treat tap water spiked with FAV. Efficient FAV and TOC removal, as well as total bacterial inactivation, was attained when treating municipal secondary effluent by the VUV/O3 process. Finally, the VUV/O3 process was operated in a continuous-flow mode in a fluidized-bed (FBR) reactor for treating FAV-spiked tap water. Complete degradation and 75.1% mineralization of 10 mg/L FAV were obtained at a hydraulic retention time of 1 and 8 min, respectively. The findings clearly suggest that the VUV/O3 process operated in a continuous-flow FBR is a promising, efficient technology for the removal of novel and emerging contaminants, such as the antiviral FAV.

Health and ecological risk assessment and simulation of heavy metal-contaminated soil of Tehran landfill.

The toxic effects of heavy metals in landfill soils have become a significant concern for human health. The present study aimed to estimate the health and ecological risk associated with soil heavy metal in Tehran landfill. A total of 48 soil samples were taken from the landfill and residential area and were analyzed using inductively coupled plasma-optical emission spectroscopy. The results showed the following order for heavy metal levels in landfill soil: Al > Fe > Mn > Zn > Cr > Cu > Pb > Ni > Co > As > Cd. The investigated ecological indices showed moderate to high heavy metal pollution. The principal component analysis revealed that the concentration of Pb, Cu, Zn, Cr, and Ni in the investigated soil was mainly affected by anthropogenic activities. Although the hazard index (HI) value in children was 6.5 times greater than that of adults, this value for both landfill workers and residents of the target area was at a safe level (HI ≤ 1). In the residential area, the Incremental Lifetime Cancer Risk (ILCR) value of adults (1.4 × 10-4) was greater than children ILCR value (1.2 × 10-4). Monte Carlo simulation and sensitivity analysis showed input variables such as exposure duration, exposure frequency, Ni concentration, soil ingestion rate, and As concentration have a positive effect on ILCR of 41.3, 24.3, 9.4, 9.0, and 2.9% in children, respectively. These results indicate that the landfill soil and the adjacent residential area are affected by heavy metal contamination and that the current solid waste management policies need to be revised.

Development of a VUV-UVC/peroxymonosulfate, continuous-flow Advanced Oxidation Process for surface water disinfection and Natural Organic Matter elimination: Application and mechanistic aspects.

Surface waters are often charged with high amounts of natural organic matter (NOM), organic contaminants and pathogens. In this work, a Vacuum UV/PMS process (VUV-UVC/PMS) was employed for treating river water, assessing the simultaneous NOM mineralization and bacterial disinfection. The VUV-UVC process (without PMS) decreased TOC concentration from 3.83 to 0.15 mg/L within 20 min, achieving complete disinfection. Adding 5 mg/L PMS increased the rate of TOC removal by 80%; complete removal of TOC was achieved in 15 min and disinfection was attained twice as fast. The mechanism of NOM mineralization was scrutinized; aeration played a considerable role due to oxygen supply, mixing, and inducing in-situ H2O2 production. HO• and SO4•- were the main radical species involved, alongside an important contribution of the matrix; sulfate enhanced TOC removal, due to the formation of additional radicals, underlining its importance. Furthermore, over 99% TOC reduction and complete disinfection was achieved in the VUV-UVC/PMS process operated under continuous-flow mode with a 2-min hydraulic retention time. Finally, the use of Atrazine (ATZ) as a probe compound and a series of scavenging tests led to an integrated proposal for the mineralization of NOM. Accordingly, the VUV-UVC/PMS process is evaluated as an efficient and promising technology for surface water treatment.

Enhanced vacuum UV-based process (VUV/H2O2/PMS) for the effective removal of ammonia from water: Engineering configuration and mechanistic considerations.

In this work, the VUV, VUV/H2O2, VUV/PMS, and VUV/H2O2/PMS processes were compared with the corresponding UVC-based AOPs under identical experimental conditions for the ammonia removal. Among the examined AOPs, the VUV/H2O2/PMS demonstrated the highest performance in converting NH4+ to N2. A 82.7 % removal of 100 mg/L NH4+, with N2 selectivity over 99 % was obtained in the VUV/H2O2/PMS process within 60 min, operated under near neutral pH. Under these operation conditions, [NO3-] was around 0.5 mg-N/L with [NO2-] remaining below detection. The VUV-mediated generation of SO4•-and HO• with NH4+ had a relative contribution of 37.9 and 62.1 %, respectively. The VUV/H2O2/PMS process operated under a flow-through mode achieved efficient removal of 100 mg/L NH4+ (80.5 %) in a hydraulic retention time (HRT) of 40 min. The continuous-flow VUV/H2O2/PMS process efficiently treated a real ammonia-laden groundwater and the concentration of NH4+ decreased from 30 mg/L to around 1 mg/L within 60 min HRT. In summary, the VUV/H2O2/PMS process was effective from the technical and energetical point of view, hence is a viable and promising technique for treating effluent containing high concentrations of ammonia.

Photocatalytic activation of peroxymonosulfate (PMS) by novel mesoporous Ag/ZnO@NiFe2O4 nanorods, inducing radical-mediated acetaminophen degradation under UVA irradiation.

A new mesoporous Ag/ZnO@NiFe2O4 nanorod was prepared by a facile, low-cost, and environmentally friendly strategy from a bimetallic Fe2Ni-MIL-88 metal organic framework (MOF), as an effective catalyst and peroxymonosulfate (PMS) photo-activator. The structural, morphological, optical, and magnetic properties, as well as the material composition were investigated by XRD, FE-SEM, EDX, HR-TEM, XPS, DRS, PL, EIS, VSM, N2 adsorption-desorption and ICP-AES analysis. 1.0% w/w loading of Ag nanoparticles on ZnO0.04@NiFe2O4 led to the best catalytic activity for PMS activation under UVA in acetaminophen (ACT) degradation. The maximum degradation efficiency for ACT was 100% within 15 min (at pH = 7.0), with a first-order rate constant of 0.368 min-1. The calculated quantum yield (1.3 × 10-3 molecule/photon) of the optimum catalyst was 2.05, and 5.63 times higher than its simple constituents, ZnO0.04@NiFe2O4 and NiFe2O4, respectively. Among the various inorganic ions, Cl- and HCO3- showed significant inhibition effect in 1.0%w/w Ag/ZnO0.04@NiFe2O4/PMS/UVA system, due to radical quenching effects. Based on scavenger experiments, HO• and SO4•- were the dominant reactive species in photocatalytic process coupled with PMS. Due to presence of the Fe3+/Fe2+, and Ni2+/Ni3+ reaction cycles in the as-made catalyst, the reaction rate of PMS activation was greatly enhanced. Moreover, the formation of a hetero-junction structure with NiFe2O4 and ZnO promoted the charge separation of the photo-generated electron/hole pairs. Finally, the major intermediates produced during the reaction were detected by LC-MS analysis, and a plausible mechanism for the photocatalytic degradation of ACT was proposed and discussed in detail.

An innovative, highly stable Ag/ZIF-67@GO nanocomposite with exceptional peroxymonosulfate (PMS) activation efficacy, for the destruction of chemical and microbiological contaminants under visible light.

In this work, Ag nanoparticles were loaded on ZIF-67 covered by graphene oxide (Ag/ZIF-67@GO), and its catalytic performance was studied for the heterogeneous activation of peroxymonosulfate (PMS) under visible-light. The catalyst surface morphology and structure were analyzed by FT-IR, XRD, XPS, DRS, FE-SEM, EDX, TEM, BET, ICP-AES and TGA analysis. The efficacy of PMS activation by the Ag/ZIF-67@GO under visible light was assessed by phenol degradation and E. coli inactivation. Phenol was completely degraded within 30 min by HO•, SO4•- and O2•- generated through the photocatalytic PMS activation. In addition, total E. coli inactivation was attained in 15 min that confirmed the highly efficient catalytic activation of PMS by the as-made nanocomposite under visible light. The reaction mechanism was elucidated and the importance of the generated reactive species followed the order of: HO• > SO4•- > O2•- > h+, implying a radical-pathway dominated process.

Advanced biodegradation process of atrazine in the peroxidase-mediated sequencing batch reactor (SBR) and moving-bed SBR (MSBR): mineralization and detoxification.

The advanced biodegradation process of atrazine was stimulated with hydrogen peroxide (H2O2) in a sequencing batch reactor (SBR) under different operational conditions due to in situ generation of H2O2-peroxidase. The complete biodegradation and mineralization of 50 mg/L atrazine was achieved in the SBR with a biomass concentration of 328 mg/L stimulated with 10 mM of H2O2. The presence of H2O2 in the SBR induced the generation of H2O2-peroxidase resulted in acceleration of atrazine biodegradation. Adding moving media to the SBR system and converting it to the MSBR considerably improved the rate of atrazine biodegradation and mineralization under H2O2 mediation. The highest specific utilization rate of atrazine in the SBR operated at the biomass concentration of 55 mg/L was 19.4 mg/gbiomass.h, while it was 33.5 mg/gbiomass.h in the MSBR operated at the biomass concentration of 37 mg/L. The low ATZ removal along with no peroxidase activity in the bioreactor in absence of H2O2 clearly ideated that the biodegradation and mineralization of ATZ was considerably mediated by H2O2-peroxidase enzyme. The toxicity of atrazine solution decreased markedly when treated in the MSBR under optimum conditions. Accordingly, the MSBR stimulated with H2O2 is an efficient and thus promising process for biodegradation of recalcitrant compounds.