Treatment Of Synthetic Wastewater Research Articles

Enhancing the anaerobic sludge characteristics and inorganic impurities removal from synthesis wastewater through integration of electrocoagulation process with up-flow anaerobic sludge blanket reactor.

The present study investigated effects of coupling electrocoagulation (EC) process with an anaerobic digestion bioreactor, namely up-flow anaerobic sludge blanket (UASB), for the synthetic wastewater treatment. The EC-UASB mode of operation consisted of one anode and two cathodes subjected to an intermittent electrical current (10 min ON/30 min OFF) with current density of 1.5 mA/cm2. In light of this integration, the concentration ofmixed liquor suspended solids and mixed liquor volatile suspended solids within anaerobic granular sludge (AGS) increased by 20.0 ± 1.4% and 12.8 ± 0.8%, respectively. The results of sludge volume index, loosely and tightly bound extracellular polymeric substances and their constituents (protein and carbohydrate) revealed that through this integration the quality of AGS has been improved. Furthermore, results of scanning electron microscopy and Fourier-transform infrared spectroscopy showed alteration in the morphology and functional groups of AGS, respectively. Additionally, this combination has demonstrated promising results in terms of performance improvement by increasing the removal efficiency of total dissolved solids by 12.1 ± 0.3% and reducing the ionic pollution in treated wastewater. However, the integration of the EC system within the UASB resulted in energy consumption and operating cost of 1.33 kWh/m3 and 0.099 USD/m3, respectively.

Activation of Persulfate by temperature and iron filings for the treatment of synthetic olive mill wastewater: Optimization of conditions with a box–Behnken design

The Persulfate (PS, S2O82-) activation by temperature and iron filings (IF) was analysed following the degradation of a five phenolic acids mixture: 3,4- Dihydroxybenzoic (3,4-DHB), 4-Hydroxybenzoic (4-HB), 3,4-Dimethoxybenzoic (3,4-DMB), 3,4,5 Trimethoxybenzoic (3,4,5-TMB) and Trans-cinnamic acid (TCA). Due to the high number of variables ruling this process, the Box-Behnken design (BBD) was used to examine the effect of each experimental variable (initial pH, dosage of PS, and operating temperature) keeping the IF load constant (1 g/L). The model obtained predicted as optimal conditions an initial pH 3, a PS dosage of 1000 mg/L, and an operating temperature of 49 °C. The optimal conditions allowed the removal of about 98.87 %, 12.58 %, 13.95 %, 25.69 %, and 81.34 % for 3,4-DHB, 4-HB, 3,4-DMB, 3,4,5-TMB and TCA, respectively. Thus, this process proved to be efficient in the degradation of 3,4- DHB and less suitable for the degradation of 4-HB. A removal of 35.09 % was measured for chemical oxygen demand (COD) for the optimal conditions after 3 h.. IF reuse studies were also addressed and it was verified that this heterogeneous catalyst maintains its efficiency for at least for three reuse cycles.

Hydroxyl and sulfate radicals-based electrochemical advanced oxidation process for treating dye-bearing wastewater – A review

ABSTRACT Dye-bearing wastewater presents a substantial ecological risk. Consequently, there is a critical requirement for efficient treatment strategies. Electrochemical advanced oxidation processes (EAOPs) utilizing hydroxyl and sulfate radicals emerge as viable alternatives to degrade dye pollutants effectively. This review article emphasizes the implementation of EAOPs in the treatment of both synthetic and actual dye-bearing wastewater. The fundamentals, chemistry, and recent developments concerning hydroxyl radicals-based EAOP, including anodic oxidation, electro-Fenton, and sulfate radicals-based EAOP, have been thoroughly reviewed. Furthermore, the article explores the comparative effectiveness of the individual hydroxyl and sulfate radical systems as well as the integrated hydroxyl and sulfate radical systems within a singular electrochemical cell. It has been established that sulfate radicals demonstrate a higher oxidation potential, greater pH adaptability, and a longer half-life in comparison to hydroxyl radicals, making them efficient for dye degradation when assessed against anodic oxidation and electro-Fenton processes. Thus, EAOPs represent a promising technological approach for the remediation of dye-bearing wastewater.

Performance of vertical flow wetland in the treatment of medium organic strength synthetic wastewater

Treatment wetlands have been used for decades to treat wastewaters with low organic strength, but little information is available on the treatment of wastewaters with high organic strength. The objective of this study was to evaluate the efficiency of a vertical flow wetland in the primary treatment of synthetic wastewater with medium organic strength (1976 mg COD/L). Alternatives in the reuse of the resulting treated wastewater were also considered. The wetland consisted of several layers of sand and gravel of different granulometry and was planted with the helophyte Eryngium horridum, a species rarely used in treatment wetlands. The wetland was fed with synthetic wastewater by a single feed pulse, with a hydraulic retention time of 24 h. The treatment removed 81% of TSS and 70% of COD. The concentrations of ammonium nitrogen and soluble reactive phosphorus increased due to partial mineralization of organic matter. Total phosphorus and total nitrogen removal were 28% and 5%, respectively. Wastewater suitability for reuse in irrigation increased after treatment. However, a later stage is recommended to further reduce COD and nutrient concentration and disinfect the water.

Studies on Kinetics, Isothermal Modelling and Optimization of Cow Dung Adsorbent for Synthetic Dairy Wastewater Treatment

<p style="line-height:200%;text-align:justify;"><span style="line-height:200%;">The dairy industry is a major food industry that processes raw milk into a variety of products. The milk processing factory produces DWE with soluble organic components, suspended particles, and trace elements. These components degrade, causing cloudiness and odour. Adsorbing total solids (TS) and controlling odour levels in dairy wastewater help to minimize odour. This study investigates the process of producing activated carbon from cow dung (ACDC) and its use in cleaning synthetic dairy wastewater (SDW) by batch adsorption and column adsorption studies. Cow dung powder is chemically activated by soaking it in 1N ZnCl<sub>2</sub> and 1N KOH solutions in a 2:1 ratio. The optimal adsorbent concentration for both ACDC was 2.5 g/50 ml. The effectiveness of ACDC treatment was evaluated by its ability to reduce turbidity, TDS, and COD. The study found that activated carbon with ZnCl<sub>2</sub> was slightly more effective than activated carbon with KOH. While the KOH ACDC was more effective at a pH of 8, achieving a removal rate of 92.88%, the ZnCl<sub>2</sub> ACDC achieved a turbidity removal of 93.3% at a pH of 4. The present work highlights the potential for activated carbon derived from cow dung to effectively and sustainably treat dairy effluent.</span></p>

Advanced electro-oxidation-adsorption process for chlorate removal from synthetic and municipal wastewater treatment effluents

This study evaluates a hybrid electro-oxidation-adsorption process for chlorate removal in wastewater treatment. Using a specialized reactor, we investigated the influence of operational parameters including current density, reaction time, granular activated carbon (GAC) dosage, electrode spacing, and pH. Optimal removal efficiency of 82.40 % was achieved under the following conditions: 75 A/m² current density, 5 min reaction time, 20 g/L GAC dosage, 2 cm electrode spacing, and a pH of 2. This method outperforms traditional adsorption and electrochemical oxidation, offering a promising solution for reducing chlorate-related environmental impacts.

Application of flow airlift fluidized bed (CAFB) - Aerobic denitrification bioreactor using polycaprolactone (PADR) as organic carbon source and biofilm carrier for synthetic marine aquaculture wastewater treatment

Aerobic denitrification, a novel method for complete nitrate removal process, relies on a constant carbon supply, and carbon availability can be a limiting factor for the process. Three biodegradable polymers - polybutylene succinate (PBS), polycaprolactone (PCL), and polylactic acid (PLA) were used as carbon source of aerobic denitrifying bacteria, Halomonas venusta for treating recirculating aquaculture wastewater in batch tests, respectively. The group utilizing PCL displayed the greatest efficiency in nitrate removal. Afterwards, a continuous flow airlift fluidized bed (CAFB) - aerobic denitrification bioreactor using PCL(PADR) as bio-carriers and carbon source was started up. The effect of shifting temperature on the nitrate removal and microbial community of CAFB-PADR was investigated under different hydraulic retention times (HRT). The results showed that no significant difference was detected in denitrification activity at 25 and 30 °C condition, where the denitrification rate was 1.1–1.8 times higher than that at 15 °C. However, the nitrogen removal efficiency was above 50 % and there was barely accumulation of nitrite at 15 °C, indicating the good nitrate removal performance in CAFB-PADR at all three temperature conditions. Microbial composition analyses revealed that as the temperature decreased, the relative abundance of Gammaproteobacteria increased, while those of Alphaproteobacteria and Bacteroidia diminished decreased. The existence of denitrifying function genera (Marinobacter, Pseudomonas, Halomonas and Hydrogenophaga) ensured the rapid removal of nitrogen in the biofilter. When the temperature dropped to 15 °C, Pseudomonas progressively took the position of Marinobacter, both of which had denitrification and degradation activities. The relative abundance of the denitrifying bacteria Halomonas that we inoculated has been less than 1 % since phase II. Overall, the PCL-supported CAFB-PADR demonstrated in this study shows potential for removing high concentrations of nitrate from recirculating marine aquaculture wastewater.

Effect of powder activated carbon (PAC) addition on the performance of anaerobic dynamic membrane bioreactor (AnDMBR): Stratification analysis of dynamic membrane characteristics

Powdered activated carbon (PAC), proved to be an effective performance enhancer in membrane bioreactor studies, has yet been applied in anaerobic dynamic membrane bioreactors (AnDMBRs). A better understanding of dynamic membrane (DM) characteristics is important for optimizing AnDMBR performance. In this study, three AnDMBRs were operated for synthetic municipal wastewater treatment with PAC dosages of 0, 1, and 3 g/L. Particular efforts were devoted to understanding the DM characteristics in layers. It was found that PAC addition increased COD removal efficiency (10 %) and decreased DM filtration resistance (60 %). The extent of performance enhancement, particularly the decrease of DM filtration resistance, appears to be much more substantial in AnDMBR than aerobic DMBR. PAC addition significantly reduced the fouling potential of suspended sludge and consequently the filtration resistance of DM. Compared with inner DM layer, the outer DM layer exhibited relatively higher fouling characteristics, such as less porous structure, higher EPS content (mainly proteins), hydrophobicity, and relative abundance of biofouling-related bacteria. The positive effect of PAC addition on reducing DM fouling characteristics turned out to be more significant for outer DM layer, mainly because of its higher PAC content associated with the higher amount of small particles.

Artificial intelligence-driven control for enhancing carbon dioxide-based wastewater pH regulation in tubular reactor

Alkaline wastewater treatment using carbon dioxide can reduce chemical costs and provide a safer alternative to traditional methods. However, complex gas-liquid reactions and narrow operating pH ranges present challenges. This research develops an artificial intelligence-driven control system for treating alkaline wastewater using carbon dioxide in a bench-scale tubular reactor. The proposed control system employs an inverse neural network to regulate the carbon dioxide gas based on the desired setpoint, along with a Smith predictor and a linear controller to compensate for natural delays, model mismatches, and pH disturbances. The inverse neural controller was trained using experimental data from a bench-scale reactor pH treatment of synthetic alkaline wastewater and verified on real influent from an electroplating wastewater treatment plant. The results show that the proposed method efficiently enforces the desired reactor outlet pH setpoint with up to 51.36% faster settling time than a proportional-integral controller while improving pH-adjusting efficiency by 72.24%.

Characterization and toxicity evaluation of chitosan/ZnO nanocompoite as promising nano-biopolymer for treatment of synthetic wastewater

Nanotechnology advances wastewater treatment through the application of Nano entities that optimize contaminant removal and enhance water purification efficacy. In this study, ZnO nanoparticles (ZnO NPs) were synthesized using Klebsiella pneumoniae, subsequently, a chitosan/ZnO nanocomposite (CS/ZnO NC) was prepared for removing reactive black 5 (RB-5) dye from synthetic wastewater. The biosynthesized nanomaterials were characterized using UV–VIS, FTIR, XRD, SEM and TEM techniques. The UV–Vis absorbance peaks at 370 nm and 350 nm corresponded to the characteristic surface plasmon resonance of ZnO NPs and the CS/ZnO NC, respectively. Additionally, FTIR analysis identified the various functional groups associated with ZnO NPs and the CS/ZnO NC. XRD analysis revealed their crystallinity to be approximately 22.44 and 25.76, respectively. The SEM images of ZnO NPs and the CS/ZnO NC show hexagonal plate-like particles with sizes of 33.66 nm and 38.64 nm, respectively. Four concentrations of ZnO NPs and CS/ZnO NC (0.25, 0.5, 1, and 2 mg/mL) were evaluated for RB-5 degradation at three different levels (25, 50, and 100 mg/L). Statistical analysis showed that chitosan/ZnO NC achieved 95 % dye degradation, compared to 81 % degradation with the same amount of ZnO nanoparticles. Furthermore, a pot experiment was carried out to evaluate the phytotoxicity effects of treated wastewater on wheat (Triticum aestivum L.). Both ZnO NPs and CS/ZnO NC did not significantly affect the viability of epithelial retinal cell lines at concentrations up to 100 µg/mL, suggesting a safe cytotoxic profile within this dosage range. Overall, CS/ZnO NC proved effective for treating industrial wastewater, making it suitable for recycling in agricultural applications

A comparative study on UASB MF-OMBR and AnMF-OMBR treating slaughterhouse wastewater: Process performance, struvite precipitation, and economic evaluation

Up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactor (UASB MF-OMBR) is a cutting-edge technology derived from the anaerobic osmotic membrane bioreactor (AnOMBR). This study investigated long-term performance of an UASB MF-OMBR and an anaerobic microfiltration osmotic membrane bioreactor (AnMF-OMBR) comparatively focusing on process performance, membrane fouling, microbial community shift, struvite precipitation, and economic evaluation for the treatment of synthetic and real slaughterhouse wastewater (SSW and RSW). The UASB MF-OMBR achieved higher process performance regarding chemical oxygen demand (COD) removal (70 ± 1 %), methane yield (0.24 ± 0.03 L CH4 g−1 CODremoved) and NH4+-N rejection (85 ± 3 %). On the other hand, high COD and PO43−-P rejections were observed in both systems (>92 % and ∼98 %, respectively). The impact of the salinity build-up in the UASB MF-OMBR was the lower due to the bioreactor configuration. In addition, compared to the AnMF-OMBR, the better water fluxes were obtained in the UASB MF-OMBR, which can be attributed to the less membrane fouling. The results of precipitation modelling and Mg2+ measurement in the sludge of both bioreactors demonstrated that the struvite precipitation occurred during the forward osmosis (FO) operation was more often and in higher amounts in the AnMF-OMBR. The economic evaluation indicated that the specific produced permeate cost (SPC) with revenue was slightly lower for the UASB MF-OMBR than that of the AnMF-OMBR.

Comparative Study on Removal of Acid Violet 90 dye by using Catalytic Ozonation Processes with n.CeO2, n.ZnO and n.CeO2/n.ZnO Nanocatalysts and Kinetic Examination

The textile industry uses high amounts of water and dyestuffs, and accordingly, wastewater containing significant amounts of dyestuffs is produced, which have to be treated before being discharged to the environment. The aim of this study is the treatment of synthetic wastewater containing 50 mg/L Acid Violet 90 dyestuff with catalytic ozonation process have been investigated by using n.CeO2, n.ZnO and n.CeO2/n.ZnO (1:1, m:m) nanocatalysts. The process optimization has been performed with the pH, ozone dose, catalyst dose and reaction time parameters. While the optimum conditions have been determined as pH 3, 600 mg/L ozone dose, 10 min reaction time, for all three catalysts, catalyst doses have differed as 50 mg/L for n. CeO2, 30 mg/L for n.ZnO and n.CeO2/n.ZnO. The removal efficiencies of AV 90 have been achieved as 97.04, 96.2 and 95.7% for n.CeO2, n.ZnO and n.CeO2/n.ZnO catalysts, respectively. Kinetic analyses showed that color removal of AV 90 dyestuff followed First order kinetics with R2 values of 0.9987 (n.CeO2), 0.9912 (n.ZnO) and 0.9923 (n.CeO2/n.ZnO) and reaction rate constant values have been calculated as 0,3435 (n.CeO2), 0,3551(n.ZnO) and 0,3226 (n.CeO2/n.ZnO) min−1.

Simultaneous organic wastewater treatment and bioelectricity production in a dual chamber microbial fuel cell with Scenedesmus obliquus biocathode

Algal biocathode MFCs (ABMs) are recently being heavily studied due to their advantage over abiotic cathode MFCs (ACMs) as dissolved oxygen (DO) generated by algal growth in the cathodic chamber is directly utilized in cathodic oxidant reduction. In this work growth of pure algae species Scenedesmus obliquus used in the cathode chamber has been studied under a photoperiod of 24 h illumination to supplement oxygen for continual MFC operation without any external supply of air or carbon dioxide and treatment of synthetic wastewater having chemical oxygen demand (COD) equivalent to medium strength domestic wastewater (5.35 g/L COD). Results of ABM showed the highest continuous current density generation of 23.93 mA/m2 and the highest continuous volumetric power density generation of 13.24 mW/m3 were around 120 h with COD removal efficiency of 92.52 % and coulombic efficiency (CE) of 41.88 %. Initial ohmic (Roh) and charge transfer (Rct) resistance values of ABM were found to be 8.3 Ω and Rct of 22.5 Ω which after 216 h of algal growth got reduced to 1 Ω and 15.1 Ω respectively. 16S microbiome profiling of the mixed microbial sludge inoculum used in the anodic chamber showed dominance of Xanthomonadaceae stenotrophomonas (9.7 %), Chitinophaga flexibacter (8.65 %), Sphingomonadaceae sphingomonas (6.82 %), Sphingobacterium multivorum (6.55 %), Dyadobacter fermentans (6.05 %), and Alcaligenaceae achromobacter (5.51 %). Elemental investigation of the bioanode’s and biocathode’s surface carried out using EDS analysis also shows that oxygen was generated in the cathodic chamber by pure Scenedesmus obliquus species.

Treatability of BPA Containing Wastewater by Catalytic and Photocatalytic Ozone Processes Using n.TiO2

In this study, the treatment of synthetic wastewater containing 10 mg/L Bisphenol A (BPA) has been investigated by the catalytic and photocatalytic ozonation process. n.TiO2 nanocatalysts have been used in catalytic (COP) and photocatalytic (PCOP) ozonation processes. Optimum parameters have been determined as pH 6.32, 1200 mg/L ozone dose, 50 mg/L n.TiO2 catalyst dose and 12.5 min reaction time for COP. Optimum parameters have been found as pH 6.32, 1200 mg/L ozone dose, 50 mg/L n.TiO2 catalyst dose, 18 Watt UV light intensity, and 10 min reaction time for PCOP. The removal efficiencies of BPA have been obtained as 95.51% and 98.09% for COP and PCOP, respectively. Kinetic analyses showed that BPA removal has been carried out Pseudo second order kinetics with R2 values of 99.1 for both processes.

Effect of Operating Parameters on Photocatalytic Treatment of Synthetic Wastewater Using CaTiO3

Photocatalysis is thought to be a long-term, environmentally friendly, economically feasible, and promising technique for treating wastewater. The development of semiconductor nanoparticles has generated a great deal of interest in the treatment of wastewater. To break down complex contaminants found in wastewater into simpler compounds, including H2O and CO2, several UV/visible light excitable nanomaterials have been explored as photocatalysts. Their effectiveness can be managed by adjusting several reaction-related parameters like the intensity of light, irradiance time, pH, catalyst dose, temperature, doping, etc. The performance of the photocatalyst in the photodegradation of contaminants is greatly affected by these parameters. The main goal of this study is to find the best operational parameters and their impact on the photocatalytic treatment of synthetic waste-water using calcium titanate (CaTiO3) nanoparticles. For this purpose, sol-gel synthesized CaTiO3 with a band gap of 3.57 eV was used. The size of the synthesized nanoparticles is smaller than 47.62 nm. The results of photocatalytic treatment of synthetic wastewater demonstrate that CaTiO3 exhibits its best photocatalytic performance at 33 W UV light, pH 6.0, and 3.33 g L-1 CaTiO3 dose with 8 hours of irradiation time. With chemical oxygen demand (COD) concentrations varying from 700 to 40000 mg L-1 at the initial stages, the percentage of COD removal under these conditions was 100% to 77%.

Economic evaluation of submerged anaerobic hybrid membrane bioreactor operating at mesophilic temperature.

A laboratory-scale mesophilic submerged anaerobic hybrid membrane bioreactor (An-HMBR) was operated for 270days for the treatment of high-strength synthetic wastewater at different hydraulic retention times (HRTs) (3days, 2days, 1day, and 0.5days). Chemical oxygen demand (COD) removal efficiency of 92% was obtained with methane yield rate of 0.18 LCH4/g CODremoval at 1-day HRT. The results of lab scale reactor at 1-day HRT were utilized for upscaling and cost analysis. Cost analysis revealed that the total capital cost comprised tank system (48%), membrane cost (32%), screen and PUF sponge (5% each), PLCs (4%), liquid pumps (3%), and others (2%). The operational cost comprised chemical cost (46%), pumping energy (42%), and sludge disposal (12%). The results revealed that the tank and heating costs accounted for the largest fraction of the total life cycle cost for full-scale An-HMBR. The heating cost can be compensated by gas recovery. Sensitivity analysis revealed that the interest rates, influent flow, and membrane flux were the most crucial parameters which affected the total cost of An-HMBR.

Simultaneous biological nutrients removal from wastewater with high ammonium and phosphorus loading using aerobic granular sludge

In this study, two SBRs were inoculated with biomass from a flocculant biological nutrient removal facility and operated for the biological treatment of synthetic wastewater to explore the impact of low influent COD/TN/TP ratio on the start-up, performance, and development of stable, matured AGS. AGS maturation and simultaneous nutrient removals were investigated for 422 days under applying limited DO (1.5–2.0 mg L−1); after that, an optimization period was performed till day 558 to study the influence of applying high DO levels (5.0–8.5 mg L−1). Initial observations at day 118 indicated high settling velocities for granules with a size ≥1.5 mm, with 90 % COD removal achieved since day 35, while exhibiting moderate levels of ammonium (68–71 %) and phosphorus removal (42–44 %). By day 422, the maturation of granules continued, reaching sizes exceeding 3 mm, with a 70 % increase in biomass growth (14.3 g L−1). P-release and P-uptake rates of 52 and 12 mg-P/g-MLVSS·h, respectively, resulted in reduced effluent PO4−3-P (1.5 ± 0.2 mg-P L−1). TN removal performance reached 82 % (NH4-N removal of 88 %), and SND of 99 % was achieved by matured granules maintaining effluent nitrite/nitrate concentrations ≤0.5 ± 0.3 mg-N L−1 (days 330–422). The optimization period was conducted by enhancing biomass mixing conditions and increasing DO, resulting in improved nitrification, with oxidation rate reaching 19.2 mg-NH4/g-MLVSS·h at DO 6 mg L−1. However, DO > 6.5 mg L−1 adversely affected EPS secretion, and granules exhibited poor settleability.

Model-based development of cell voltage control system for modified bio-electro-Fenton process

A modified bio-electro-Fenton (M−BEF) process with a cell voltage control system that improves the efficiency of organic removal and energy savings is demonstrated. The M−BEF process can accomplish bioelectricity generation, H2O2 production, and the Fenton reaction in a continuous-flow reactor. During synthetic wastewater treatment containing biodegradable (glucose) and recalcitrant (biphenyl) organic matter, the effluent chemical oxygen demand (COD) concentration was maintained between 2 and 6 mg L-1. To investigate the impact of different operating schemes on energy usage, model-based design (MBD) modeling and simulations were performed, which showed that COD removal efficiency without an external voltage supply was unstable at < 70 %. The automatic cell voltage control system saved 90 % of the power compared to the continuous cell voltage supply system. Further testing on more environmental samples and pollutants will enable real-time optimization of supplied power and wastewater treatment using the cell voltage control system.

Performance and hydrodynamic study of a new multi‐stage solar photoreactor with immobilized ZnO for synthetic wastewater treatment

AbstractThis study aims to design a new multi‐stage photoreactor with immobilized ZnO and assess its performance in reducing textile wastewater toxicity using solar energy. The electric conductivity measurement is retained as a detection method to obtain the residence time distribution (RTD) function. The RTD is then used to characterize the hydrodynamic behavior of the photoreactor and to evaluate its deviation from the distribution curves of ideal reactors. Solar experiments are conducted to demonstrate the performance of this multistage reactor towards the degradation of a textile azo dye namely Solophenyl Red 3BL (SR 3BL). The influence of the flow rate and the SR 3BL initial concentration (CO) are considered. The variation of the flow rate slightly influences the SR 3BL photodegradation efficiency and it is inversely proportional to its concentration. The study of the reuse of the immobilized catalyst shows that the degradation efficiency of 98% is reached even after multiple photocatalytic cycles. The figure of merit collector area per order was in the range of 35 to 110 . This result provides useful information for scaling up and estimating energy efficiency of the reactor.

Optimal conditions and nitrogen removal performance of aerobic denitrifier Comamonas sp. pw-6 and its bioaugmented application in synthetic domestic wastewater treatment.

To assess the possibility of using aerobic denitrification (AD) bacteria with high NO2--N accumulation for nitrogen removal in wastewater treatment, conditional optimization, as well as sole and mixed nitrogen source tests involving AD bacterium, Comamonas sp. pw-6 was performed. The results showed that the optimal carbon source, pH, C/N ratio, rotational speed, and salinity for this strain were determined to be succinate, 7, 20, 160 rpm, and 0%, respectively. Further, this strain preferentially utilized NH4+-N, NO3--N, and NO2--N, and when NO3--N was its sole nitrogen source, 92.28% of the NO3--N (150 mg·L-1) was converted to NO2--N. However, when NH4+-N and NO3--N constituted the mixed nitrogen source, NO3--N utilization by this strain was significantly lower (p < 0.05). Therefore, a strategy was proposed to combine pw-6 bacteria with traditional autotrophic nitrification to achieve the application of pw-6 bacteria in NH4+-N-containing wastewater treatment. Bioaugmented application experiments showed significantly higher NH4+-N removal (5.96 ± 0.94 mg·L-1·h-1) and lower NO3--N accumulation (2.52 ± 0.18 mg·L-1·h-1) rates (p < 0.05) than those observed for the control test. Thus, AD bacteria with high NO2--N accumulation can also be used for practical applications, providing a basis for expanding the selection range of AD strains for wastewater treatment.