Total Organic Carbon Removal Efficiency Research Articles

Do mycorrhizal symbiosis affect wastewater purification in constructed wetlands with different substrates?

Arbuscular mycorrhizal fungi (AMF) can play important roles in pollutant removal in the terrestrial system. However, the functional role of AMF in wetland systems is still unclear. This study evaluated the effects of AMF on the purification of the pharmaceuticals and personal care products (PPCPs) containing wastewater in constructed wetlands (CWs) filled with different substrate types (sand, perlite, vermiculite or biochar). Results indicated that the removal efficiencies of total organic carbon (TOC), phosphate (PO43−-P), and total nitrogen (TN) in CWs with different substrates were in the following order: biochar > vermiculite > perlite > sand. Compared with sand systems, the removal efficiencies of TOC, PO43−-P, ammonium (NH4+-N), and TN in CWs filled with adsorptive substrates (biochar, vermiculite, or perlite) were enhanced by 3.8–11.4 %, 11.6–30.6 %, 16.5–31.2 %, and 6.2–34.6 %, respectively. AM symbiosis increased TOC, TN, and PO43−-P removal in CWs but the adsorptive substrates showed more significant influences on wastewater purification than AMF symbiosis. Besides, plant (Glyceria maxima) presence also improved the performance of CWs on wastewater purification. Overall, all the findings indicated that the interaction effects of AM symbiosis and adsorptive substrates (e.g., biochar, vermiculite, or perlite) could enhance the removal performance of pollutants from wastewater in planted CWs.

Effects of influent organic load on TMAH (tetramethylammonium hydroxide) wastewater treatment by anaerobic process

Tetramethylammonium hydroxide (TMAH) is a corrosive alkaline and neuronal toxic compound, which is widely used in the thin-film transistor liquid crystal display industry. In this study the performance of the anaerobic sequencing batch reactors (SBR) for treating synthetic TMAH wastewater under different organic influent loads was evaluated thoroughly over a 208 day period. The results indicated that when the influent organic load was below 376.4 mg TOC/(L·day), total organic carbon (TOC) removal was enhanced with influent organic load increasing. And the maximum TOC removal efficiency and CH4 production reached 92.5% and 589 mL/L reactor of one cycle, respectively. Further raising the load suppressed the TMAH degradation and microbiological activity. Only 6.0% organic nitrogen converted to ammonium and TOC removal efficiency declined to 13.5% at the influent organic load of 1130.5 mg TOC/ (L·day), with anaerobic sludge settling performance decline. And the biogas production of one cycle dropped to 60 mL/L reactor. It was also found that reducing influent organic load could not restore the system. Microbial diversity and richness also varied in response to the influent organic load. Illumina MiSeq sequencing analysis indicated Caldisericum, norank_f_KD1–131, norank_f_Bacteroidetes_vadinHA17, and Treponema were enriched at the influent load of 376.4 mg TOC/(L·day). RT-qPCR results confirmed that high influent organic load suppressed the expression of the ureC gene and mcrA gene, and then inhibited ammonification and methanogenesis.

Exploiting refractory organic matter for advanced nitrogen removal from mature landfill leachate via anammox in an expanded granular sludge bed reactor

Anammox is an efficient low-carbon nitrogen removal technology for mature landfill leachate (MLL). However, it produces 11 % nitrate theoretically, which needs further removal. In this study, the mechanisms of exploiting refractory organic matter (ROM) from an MLL as an inner carbon source for advanced nitrogen removal via anammox were systematically analyzed, and the effects of hydraulic retention time on nitrogen and ROM removal/utilization were investigated. Without any external carbon source, a total nitrogen and organic carbon removal efficiency of 94.50 % and 27.12 %, respectively, were achieved, with a nitrogen loading rate of 2.4 kg N/(m3·d). The abundances of norank_f_norank_o_SBR1031, OLB13, and norank_f_A4b, which had the capacity to degrade ROM, increased from 21.63 % to 49.21 %. This study reveals that the ROM in an MLL can be exploited for synchronous advanced nitrogen and organic matter removal.

Comparative Photocatalytic Activity and Total Organic Carbon Removal Efficiency of TiO2 And ZnO for Reactive Black 5 Photodegradation

AbstractThe photocatalytic performance of TiO2 and ZnO was comparatively studied for photocatalytic degradation of reactive black 5 (RB5) under artificial UVC irradiation. The effect of initial solution pH, catalyst concentration, initial RB5 concentration, purging oxygen rate, stirring rate, and process temperature on the degradation process by TiO2 and ZnO was investigated. In addition, total organic carbon (TOC) analysis has been employed for each parameter to detect the presence of organic intermediates and the photodegradation performance of catalysts simultaneously with the photocatalytic degradation process. The RB5 photodegradation was more rapid in the aqueous medium by TiO2 under UVC irradiation compared to the catalysis by ZnO. On the other hand, the slower photocatalysis by ZnO resulted in generating more organic intermediates. The structural and morphological analyses of photocatalysts TiO2 and ZnO were performed using XRD and FE‐SEM techniques. The UV‐vis spectroscopy measurements supported that the TiO2 demonstrated evidently better photocatalytic activity than ZnO for RB5 degradation.

Soil decontamination by natural minerals: a comparison study of chalcopyrite and pyrite

Environmental context With the rapid pace of industrialisation and urbanisation, soil contamination by organic pollutants has become a global focus of concern due to its serious threat to ecosystems and human health. Although a myriad of synthetic catalysts have been developed, natural minerals have the potential to be developed into cost-effective, environmentally benign and efficient catalysts to decontaminate soil. The efficient performance of natural minerals demonstrated in this study indicates a potential for their utilisation in the removal of refractory organic pollutants in soil. Rationale Organic pollution of soil has raised worldwide concern owing to the potential effects on ecosystems and human health. Natural metal minerals rich in transition metal elements have the potential to be developed into environmentally benign activators of peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) for soil decontamination. Methodology A comparison study employing natural chalcopyrite (NCP) and natural pyrite (NP) as activators in the combined Fenton-like systems of PMS and H2O2 to degrade organic pollutants in soil has been carried out. Tetracycline hydrochloride (TCH) and phenanthrene (PHE) were selected as representatives of widely existing contaminants, antibiotics and polycyclic aromatic hydrocarbons, in the study. Key parameters including initial pH, catalyst and oxidants dosage were also optimised. Results A total organic carbon (TOC) removal efficiency of 68.66% was achieved for TCH (500 mg kg–1) with the addition of 0.75 g L–1 NCP, 1.23 mM PMS and 1.23 mM H2O2 within 4 h, whereas a slightly lower mineralisation efficiency of 64.78% was obtained by the NP heterogeneous system. For PHE (50 mg kg–1), 93.04% of TOC was removed using a NCP/PMS/H2O2 process, which was much higher than that of NP (45.76%) after 24 h. The quenching experiments indicated that ˙OH prevailed over SO4˙−EN22116_IE1.gif, and ˙O2−EN22116_IE2.gif also played a vital role in the PMS/H2O2 coupling process. Discussion The more superior performance of NCP has been elucidated via X-ray photoelectron spectroscoy analysis and comparison of catalytic mechanisms. The existence of Cu+ played an important role in the transformation of Fe3+ to Fe2+ and facilitated the continuous generation of active radicals. A possible degradation pathway was proposed based on the intermediates identified by GC-MS analysis. We anticipate this study would provide implications for the utilisation of natural minerals in the removal of refractory organic pollutants in soil.

Dual functional WO3/BiVO4 heterostructures for efficient photoelectrochemical water splitting and glycerol degradation.

Dual functional heterojunctions of tungsten oxide and bismuth vanadate (WO3/BiVO4) photoanodes are developed and their applications in photoelectrochemical (PEC) water splitting and mineralization of glycerol are demonstrated. The thin-film WO3/BiVO4 photoelectrode was fabricated by a facile hydrothermal method. The morphology, chemical composition, crystalline structure, chemical state, and optical absorption properties of the WO3/BiVO4 photoelectrodes were characterized systematically. The WO3/BiVO4 photoelectrode exhibits a good distribution of elements and a well-crystalline monoclinic WO3 and monoclinic scheelite BiVO4. The light-absorption spectrum of the WO3/BiVO4 photoelectrodes reveals a broad absorption band in the visible light region with a maximum absorption of around 520 nm. The dual functional WO3/BiVO4 photoelectrodes achieved a high photocurrent density of 6.85 mA cm-2, which is 2.8 times higher than that of the pristine WO3 photoelectrode in the presence of a mixture of 0.5 M Na2SO4 and 0.5 M glycerol electrolyte under AM 1.5 G (100 mW cm-2) illumination. The superior PEC performance of the WO3/BiVO4 photoelectrode was attributed to the synergistic effects of the superior crystal structure, light absorption, and efficient charge separation. Simultaneously, glycerol plays an essential role in increasing the efficiency of hydrogen production by suppressing charge recombination in the water redox reaction. Moreover, the WO3/BiVO4 photoelectrode shows the total organic carbon (TOC) removal efficiency of glycerol at about 82% at 120 min. Notably, the WO3/BiVO4 photoelectrode can be a promising photoelectrode for simultaneous hydrogen production and mineralization of glycerol with a simple, economical, and environmentally friendly approach.

Cobalt and nitrogen co-doped monolithic carbon foam for ultrafast degradation of emerging organic pollutants via peroxymonosulfate activation

Cobalt-based catalysts are expected as one of the most promising peroxymonosulfate (PMS) activators for the removal of organic pollutants from industrial wastewater. However, the easy agglomeration, difficult separation, and secondary pollution of cobalt ions limit their practical application. In this study, a novel, highly efficient, reusable cobalt and nitrogen co-doped monolithic carbon foam (Co-N-CMF) was utilized to activate PMS for ultrafast pollutant degradation. Co-N-CMF (0.2 g/L) showed ultrafast catalytic kinetics and higher total organic carbon (TOC) removal efficiency. Bisphenol A, ciprofloxacin, 2,4-dichlorophenoxyacetic acid, and 2,4-dichlorophenol could be completely degraded after 2, 4, 5, and 5 min, and the TOC removal efficiencies were 77.4 %, 68.9 %, 72.8 %, and 79.8 %, respectively, corresponding to the above pollution. The sulfate radical (SO4•-) was the main reactive oxygen species in Co-N-CMF/PMS based on electron paramagnetic resonance. The ecological structure-activity relationship program analysis via the quantitative structure activity relationship analysis and phytotoxicity assessment revealed that the Co-N-CMF/PMS system demonstrates good ecological safety and ecological compatibility. The Co-N-CMF catalyst has good catalytic activity and facile recycling, which provides a fine method with excellent PMS activation capacity for 2,4-dichlorophenol elimination from simulated industrial wastewater. This study provides new insights into the development of monolithic catalysts for ultrafast wastewater treatment via PMS activation.

Performance of electrochemical treatment of refractory organic matter in printing and dyeing reverse osmosis concentrate

The printing and dyeing wastewater treatment process produces a reverse osmosis concentrate (ROC) that contains high organic matter content and requires proper treatment before discharge. Electrochemical oxidation was applied in this study to treat organic pollutants in the ROC. In addition, the concentration variation of phthalate esters (PAEs) in ROC was investigated. The results demonstrated that the electrochemical oxidation process could effectively reduce the organic content in ROC; the total organic carbon (TOC) removal efficiency reached 83.38% at pH 2.4 and a current density of 40 mA/cm2. Increasing the current density can markedly enhance the oxidation of the bulk organic matter (i.e., TOC, chemical oxygen demand (COD), UV254, and fluorescence). The effect of pH on the decomposition of organic materials was slightly less as than that of current density. The molecular weight (MW) distribution in the ROC indicated that the percentage of components larger than 5 kDa was approximately 10%, but decreased to 2.16% with persistent electrolysis. Further, 3D fluorescence spectroscopy suggests that the organic matter in ROC was mainly aromatic proteins (APⅡ) and soluble microbial products (SMP), which account for 25.78% and 51.39% of the total fluorescence, respectively. Notably, acidic conditions are more favorable for the breakdown of fluorescence, which is attributed to the higher oxidative capacity of·OH. The decomposition of PAEs was enhanced by lowering the pH, and degradation efficiency increased by 36.45% when the pH was lowered from 9.8 to 2.4. Qualitative analysis by gas chromatography-mass spectrometry (GC-MS) showed that the abundance of organic matter in the treated ROC was significantly decreased.

Hydrothermal Synthesis of Siderite and Application as Catalyst in the Electro-Fenton Oxidation of p-Benzoquinone.

A weak aspect of the electro-Fenton (EF) oxidation of contaminants is the dependence of the Fenton reaction on acidic pH values. Therefore, the rationale of this work was to develop a novel catalyst capable of promoting the EF oxidation process at near-neutral and basic pH values. In this framework, rhombohedral FeCO3 was synthesized hydrothermally and used as a catalyst in the EF oxidation of p-benzoquinone (BQ). The catalyst was characterized using various surface and spectroscopic methods. Moreover, the effects of applied current (100-500 mA), time (1-9 h), catalyst dosage (0.25-1.00 g L-1), and initial concentration of BQ (0.50-1.00 mM) on the total organic carbon removal efficiency were determined. The results indicated that a 400 mA current was sufficient for a 95% total organic carbon removal and that the increase in catalyst dosage had a positive effect on the mineralization of BQ. It was determined that at pH 3, FeCO3 behaved like a homogeneous catalyst by releasing Fe3+ ions; whereas, at the pH range of 5-7, it shifted to a homogeneous/heterogeneous catalyst. At pH 9, it worked solely as a heterogeneous catalyst due to the decrease of Fe ions passing into the solution. Finally, the spent catalyst did not undergo structural deformations after the EF treatment at higher pH values and could be regenerated and used several times.

Degradation of Safranin O in Water by UV/TiO2/IO4− Process: Effect of Operating Conditions and Mineralization

Hybrid advanced oxidation processes employed to degrade recalcitrant organic pollutants in water have been widely examined in recent years. In the present work, the potential of TiO2-mediated photocatalysis in the presence of the periodate anion (IO4−) toward Safranin O (SO) removal from aqueous solutions was investigated. The findings revealed a high efficiency of the UV/TiO2/IO4− system due to the production of more reactive radicals (•OH, IO3• and IO4•) and non-radical species (O3, IO3− and IO4−). Additionally, the presence of IO4− as an effective electron acceptor avoids electron-hole recombination, which induces more oxidative reactions at the hole level, increasing the degradation rate of SO. Kinetically, the involvement of IO4− anions in the UV/TiO2 system enhanced substantially the initial rate of degradation; from 0.295 to 12.07 mg L−1 min−1. The performance of both systems, i.e., UV/TiO2 and UV/TiO2/IO4−, was examined under different conditions such as initial dye concentration, photocatalyst loading, periodate dosage, initial solution pH, temperature and dissolved gases. The SO degradation was found to be maximized at low concentration of pollutant at the optimum loading of catalyst (0.4 g L−1). The continuous increasing in periodate concentration over the range of 0.01–3 mM improved the system reactivity with no overdose effect. Both systems seemed to be insensitive to minor variations in temperature in the range of 15–45 °C, and showed a strong dependence on initial solution pH where the degradation rates increased proportionally with pH values up to pH 10 and decreased afterwards. A slight negative effect on the photocatalytic removal yield was noted under either aeration, nitrogen or argon atmospheres in the presence of periodate (UV/TiO2/IO4−), with minor enhancement under aeration for the classical system (UV/TiO2). The mineralization of the organic substrate was also monitored. The depletion of organic matter with time was measured using total organic carbon (TOC) analysis. Despite the rapid decolorization of the dye solution in the UV/TiO2/IO4− system, a TOC removal efficiency of ~62% was obtained with both systems after 180 min of treatment.

Green and Sustainable Treatment of Urine Wastewater with a Membrane-Aerated Biofilm Reactor for Space Applications

Sustainability has been a concern of survival for future long-term manned space missions. Therefore, the wastewater generated by the crew members, containing urine and hygiene wastewater, should be treated with appropriate biological processes to promote recycling efficiency. In this study, we developed a membrane-aerated biofilm reactor (MABR) that could achieve up to 96% total organic carbon (TOC) removal efficiency and up to 82% denitrification efficiency for an influent with 370–390 mg/L TOC and 500–600 mg/L total nitrogen (TN) without additional carbon source or sludge discharge. The nitrogen removal rate was about 100 mg N L−1 d−1. Metagenomic analysis indicated the presence of a variety of nitrifying, denitrifying, and anammox bacteria in the microbial community and existence of functional genes in nitrification, denitrification, and anammox pathways.

Exploring the metabolic capabilities of purple phototrophic bacteria during piggery wastewater treatment

Purple phototrophic bacteria (PPB) are receiving an increasing attention due to their extraordinary metabolic capabilities for nutrient and carbon recovery from wastewaters. Batch experiments were herein performed to assess the influence of the type of radiation (photosynthetic active radiation (PAR), near-infrared radiation (NIR) and PAR using an UV-VIS absorbing filter), temperature (13 °C and 30 °C), type of metabolism (photoheterotrophic and chemoheterotrophic), type of inoculum (mixed culture and pure strain Rhodopseudomonas palustris) and wastewater load (1:5 and 1:10 dilutions) during piggery wastewater (PWW) treatment by PPB. The use of UV-VIS filtered PAR supported both a high content of bacteriochlorophyll in PPB and the highest total organic carbon (TOC) and total nitrogen (TN) removal efficiency (RE) (74 % and 37 %, respectively), but at lower maximum removal rates. Interestingly, PPB exhibited similar TOC-REs and TN-REs (73 % and 37 %, respectively) at 13 °C than at 30 °C (71 % and 45 %, respectively), at similar removal rates. Mixed cultures of PPB achieved a higher nutrient assimilation rate than R. palustris, supporting a total assimilation of the volatile fatty acids present in 10 folds diluted PWW. In brief, mixed cultures of PPB were highly efficient during PWW treatment, regardless of the type of radiation and temperature under photoheterotrophic growth.

Electro‐oxidation of pistachio processing wastewater using Ti/Pt mesh‐type anodes in batch system

AbstractIn this study, the treatment of pistachio processing wastewater (PPW) by electro‐oxidation method was investigated. Ti/Pt‐plated electrodes were used for the anode material, and stainless steel electrodes were used for cathode material. Experimental studies were carried out in batch mode. Stirring speed, supporting electrolyte species and concentration, initial pH value, current density, temperature and dilution ratio were selected as experimental parameters effecting removal efficiency. In Ti/Pt electrode experimental studies on the optimum conditions, chemical oxygen demand (COD), total organic carbon (TOC) and total phenols (TP) removal efficiencies were obtained, respectively, as 99.98%, 70.74% and 100%, and energy consumption value was obtained as 297.5 kW‐h/m3 (12.39 kW‐h/kg COD, 51.29 kW‐h/kg TOC and 64.68 kW‐h/kg TP). As a result of the experimental studies, the PPW can be treated by electro‐oxidation. Given the results of removal efficiency and energy consumption values, it was concluded the electro‐oxidation using Ti/Pt anode very appropriate treatment of PPW.

Optimising zero-valent iron from industrial waste using a modified air-Fenton system to treat cutting oil wastewater using response surface methodology

This study investigates the treatment of cutting oil wastewater from the automotive parts manufacturing industry to promote sustainability via the use of ‘used shot blasts’, which are the by-products of auto parts production. Used shot blasts are rich iron sources of Fe 0 , which becomes an effective catalyst in the Fenton reaction. A modified air-Fenton (MAF) system was proposed to generate hydroxyl radicals that eliminated recalcitrant organics in cutting oil wastewater. First, the Taguchi method, comprising the L18 orthogonal array design, was used to identify significant operation factors, including the size and amount of used shot blasts, initial pH, reaction time, mixing speed, initial cutting oil concentration, and air flow rate. Then, a central composite rotatable design coupled with response surface methodology (RSM) was used to determine the optimal conditions and model the influencing variables. The results provided three crucial variables for the cutting oil wastewater treatment through use of the MAF system: initial pH, the amount of used shot blasts, and initial cutting oil concentration. RSM was applied to reveal the optimum operating conditions, achieving a maximum removal efficiency of 92.82% for chemical oxygen demand (COD), 80.18% for total organic carbon (TOC), and 99.55% for turbidity within 45 min of operating the MAF system. The model agreed well with the experimental data, with coefficient of determination values of 0.9819, 0.9654, and 0.9715 for COD, TOC, and turbidity removal efficiency, respectively. Pseudo-second-order reaction kinetics fitted well for COD removal, with a rate constant of 0.0218 min −1 and hydrogen peroxide generation of 0.0169 M. Overall, the proposed MAF system was efficient and had a low operating cost (0.67 USD/m 3 ).

Perfluorooctanoic acid (PFOA) removal from real landfill leachate wastewater and simulated soil leachate by electrochemical oxidation process

Poly and perfluoroalkyl compounds (PFASs) are a group of chemicals that are widely used and are difficult to purify. Within this group, perfluorooctanoic acid (PFOA), known for its highly polar and strong carbon–fluorine bonds, is a frequently encountered species in surface water, drinking water, and groundwater. In this study, we investigated the efficiency of electrooxidation (EO) in PFOA removal, optimization of EO parameters, and groundwater simulation in a realistic scenario. The EO optimization experiments were performed with a boron-doped diamond (BDD) anode for different values of pH, current density, and inlet concentration, and the effects of different anode materials were investigated for comparison. Under optimum conditions, total organic carbon (TOC) removal of up to 90% was achieved. In the groundwater simulation, we applied optimized EO parameters after obtaining leachates from the soil. A TOC removal of up to 86% was obtained in the EO of simulated groundwater contaminated with PFOA. In the case of realistic leachate simulation, four different leachate treatments were applied to PFOA-contaminated soil, and high TOC removal was achieved in all matrices. Additionally, the EO with BDD was applied to landfill leachate wastewater supplemented with PFOA to monitor the effectiveness of the process. A TOC removal of 85% was achieved, and it was observed that the number of free F-ions increased. The results showed that the BDD EO has a high potential for the treatment of PFOA-contaminated groundwater. • A realistic simulation was designed to obtain PFOA-contaminated groundwater. • Parameter optimization for BDD EO was performed. • The effects of different anodes (DSA) in the EO was investigated. • TOC removal efficiencies for water and wastewater were 90% and 78%, respectively. • TOC removal of 85% was achieved for PFOA contaminated groundwater.

An assessment of the UV/nFe0 /H2 O2 system for the removal of refractory organics in the effluent produced by the biological treatment of landfill leachate.

The removal efficiency and mechanism of the ultraviolet/nanoscale Fe0 /H2 O2 (UV/nFe0 /H2 O2 ) system for refractory organics in membrane bioreactor effluent were investigated. The most effective removal of organics was achieved at initial pH = 3.0, H2 O2 dosage = 50 mM, nFe0 dosage = 1.0 g/L, and UV power = 15 W, with a reaction time of 60 min. Under these conditions, the absorbance at 254 nm, chromaticity, and total organic carbon removal efficiencies were 65.13%, 79.67%, and 61.51%, respectively, and the aromaticity, humification, molecular weight, and polymerization of organics were all significantly reduced. The surface morphology and elemental valence analysis of nano zero-valent iron (nFe0 ) before and after the reaction revealed the formation of iron-based (hydrated) oxides, such as Fe2 O3 , Fe3 O4 , FeOOH, and Fe (OH)3 , on the surface of the nFe0 . Refractory organics were removed by Fenton-like reactions in the homogeneous and heterogeneous adsorption-precipitation of iron-based colloids. At the same time, UV radiation accelerated the formation of Fe2+ on the nFe0 surface and promoted the Fe3+ /Fe2+ redox cycle to a certain extent, enhancing the removal of refractory organics. The results provide a theoretical basis for the application of the UV/nFe0 /H2 O2 system to remove refractory organics in the effluent produced by the biological treatment of landfill leachate. PRACTITIONER POINTS: The UV/nFe0 /H2 O2 process is effective in refractory organics removal in leachate treatment. Humus in leachate was largely destroyed and mineralized by the UV/nFe0 /H2 O2 process. Active nFe0 material participated in the Fenton-like process and was promoted by UV. The effects of nFe0 material and UV introduction were investigated.

Onshore oilfield produced water treatment by hybrid microfiltration-biological process using kaolin based ceramic membrane and oleaginous Rhodococcus opacus

This study examined the treatment of onshore oilfield produced water by various strategies: microfiltration, biological treatment, microfiltration followed by biological treatment (MF-B), and biological treatment followed by microfiltration (B-MF). Microfiltration experiments were carried out at various applied pressures (69–345 kPa) using a tubular ceramic membrane prepared from inexpensive clays (kaolin and quartz). Maximum removal efficiency values of the parameters total suspended solids (TSS) (100 %), turbidity (100 %), total organic carbon (TOC) (84 %) and chemical oxygen demand (COD) (78 %) were obtained at a low pressure of 69 kPa. Complete removal of TSS and turbidity were observed at all the applied pressure values. However, the COD and TOC removal efficiency decreased with an increase in applied pressure from 69 to 345 kPa. In order to meet the discharge limits of the treated water parameters, other alternative techniques were investigated such as biological treatment, MF-B and B-MF. The oleaginous bacterium Rhodococcus opacus was used for the biological treatment of produced water. The results revealed that combined MF-B system was most effective, showing 99 % removal efficiency for TOC and COD compared to all other systems (microfiltration, biological treatment, and B-MF). Cleaning efficiency of membrane was investigated by using different chemical reagents and a mixture containing 0.10 wt% sodium dodecyl sulfate and 1 wt% NaOCl resulted in a maximum flux recovery of 92.60 %. Furthermore, toxicity assessment of the treated water obtained from MF-B system revealed maximum germination index of 74.30 % for Cicer arietinum and 71.10 % for Vigna mungo. Hence, it can be concluded that, hybrid MF-B system is highly efficient for complete removal of TOC, COD from produced water and reuse of the treated water.

Performance of a solar photocatalysis reactor as pretreatment for wastewater via UV, UV/TiO2, and UV/H2O2 to control membrane fouling

The performance of a solar photocatalysis reactor as pretreatment for the removal of total organic carbon (TOC) and turbidity from municipal wastewater was achieved by implementing an integrated system as tertiary treatment. The process consisted of ultraviolet (UV) sunlight, UV sunlight/H2O2, and UV sunlight/TiO2 nanocatalysts as pretreatment steps to prevent ultrafiltration (UF) membrane fouling. The characterization of TiO2 was conducted with X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy , and Brunauer–Emmett–Teller surface area analysis. This study investigated the effect of time and solar radiation using UV, UV/H2O2, and UV/TiO2 to remove TOC and turbidity. The transmembrane pressure improvement was studied using a UF membrane system to pretreat wastewater with different UV doses of sunlight for 5 h and UV/H2O2 and UV/TiO2. The results showed that the highest removal efficiency of the turbidity and TOC reached 95% and 31%, respectively. The highest removal efficiency of the turbidity reached 40, 75, and 95% using UV, UV/H2O2, and UV/TiO2, respectively, while the optimal removal efficiency of TOC reached 20%, 30%, and 50%, respectively.

Treatment of refractory organics in biologically treated landfill leachate by a zero valent iron enhanced Peroxone process: Degradation efficiency and mechanism study.

A zero valent iron (ZVI) enhanced Peroxone process (ZVI/Peroxone) was used to treat biologically treated landfill leachate (BTL). The treatment efficiency of the ZVI/Peroxone process was compared to single (ZVI, O3 and H2O2) and dual (ZVI/H2O2, Fe0/O3 and Peroxone) processes. The results showed that ZVI can greatly enhance the treatment capability of the Peroxone process, and the color number (CN), absorbance at 254 nm (UV254), and total organic carbon (TOC) removal efficiencies were 98.82, 84.30 and 66.38%, respectively. In the ZVI/Peroxone process, higher O3 and ZVI dosages improved organics removal, and H2O2 could promote organics removal within a certain dosage range. However, too much H2O2 decreased treatment efficiency. The best treatment performance by the ZVI/Peroxone process was obtained under acidic conditions. The three-dimensional excitation and emission matrix analysis showed that BTL mainly contained two fluorescent substances, which were fulvic-like substances in the ultraviolet region (Ex/Em = 235-255 nm/410-450 nm) and fulvic-like substances in the visible light region (Ex/Em = 310-360 nm/370-450 nm). Fluorescent substances could be substantially degraded by the ZVI/Peroxone process during the early stages of the reaction. An analysis of ZVI morphology and element valency changes showed that the micro Fe0 particles used in this study remained highly reactive during the process. The ZVI enhanced the homogenous Fenton, heterogeneous Fenton, and coagulation-flocculation effects during the Peroxone process.

Ternary ZIF-67/MXene/CNF aerogels for enhanced photocatalytic TBBPA degradation via peroxymonosulfate activation

The novel photocatalytic advanced oxidation catalyst, ZIF-67@MXene-TA-CNF (ZIF-67@MTC) aerogels, was prepared via introducing tannic acid-coated cellulose nanofibril (TA-CNF), two-dimensional layered MXene, and ZIF-67 into a composite aerogel network. Specially, TA assisted the crosslinking of CNF through hydrogen bonds to construct the flexible aerogel skeleton, accompanied by assembly of MXene and ZIF-67. MXene not only provided sufficient attachment sites for the anchoring of ZIF-67, but also can be used as a repository for electron transfer to facilitate the separation of photogenerated electrons and holes. In the peroxymonosulfate (PMS)/aerogels/visible light system, the SO4-, OH and 1O2 were generated, and 1O2 was the main reactive species. As a result, 99.9 % of Tetrabromobisphenol A (TBBPA) can be degraded and the total organic carbon (TOC) removal efficiency reached 81.8 % within 40 min in this system. The results might provide a new concept for the design of biomass aerogels for applications in organic pollutant removal.