Combination of ozonation, activated carbon, and biological aerated filter for advanced treatment of dyeing wastewater for reuse

Treatment of Distillery Industrial Wastewater Using Ozone Assisted Fenton’s Process: Color and Chemical Oxygen Demand Removal with Electrical Energy per Order Evaluation

Ozonation is one of the most effective and efficient advanced oxidation processes (AOPs) and has shown great potential in the treatment of industrial effluent and wastewater. In the present work, the ozone-Fenton process for % COD and color removal together with electrical energy per order (EE/O) determination for distillery industrial wastewater (DIW) was established. The process was developed by combining the ozone (O3) with the Fenton (Fe2+/H2O2) process. The ozone-Fenton (O3/Fe2+/H2O2) was compared with other treatment processes such as O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 for EE/O together with % COD and color removal efficiency for DIW. The removal of color at 100% and chemical oxygen demand (COD) of 96.875% were achieved with a minimum of EE/O of 0.5315 kWh/m3 using the O3/Fe2+/H2O2 process by operating at optimum conditions. The % COD and color values obtained using O3/Fe2+/H2O2 were significantly higher than those obtained using O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 processes. The % color, % COD removal, and its associated EE/O were evaluated by varying Fe2+, H2O2, O3 inlet and COD concentration, and initial wastewater pH using the O3/Fe2+/H2O2 process. The synergy effect of the O3 and Fe2+/H2O2 processes was evaluated and reported. Our experimental findings suggest that combining O3 with the Fe2+/H2O2 process could effectively treat industrial effluent and wastewater.

Constructed wetlands for textile wastewater remediation: A review on concept, pollutant removal mechanisms, and integrated technologies for efficiency enhancement

Textile industries are among the ecologically unsustainable industries that release voluminous wastewater threatening ecosystem health. The constructed wetlands (CWs) are low-cost eco-technological interventions for the management of industrial wastewaters. The CWs are self-sustaining remediation systems that do not require an external source of energy and encompass simple operational mechanisms including biological (bioremediation and phytoremediation), chemical, and physical processes for pollutant removal. This review idiosyncratically scrutinizes the recent advances and developments in CWs, and their types employed for textile wastewater treatment. The major focus is on mechanisms involved during the removal of contaminants from textile wastewater in CWs and factors affecting the performance of the system. The article also discusses the State-of-the-Art integrated technologies e.g., CW-MFCs/algal ponds/sponge iron coupled systems, for the performance and sustainability enhancement of CWs. All the important aspects together with the technology amalgamation are critically synthesized for establishing suitable strategies for CW-based textile wastewater treatment systems.

Advanced treatment of effluent extended aeration process using biological aerated filter (BAF) with natural media: modification in media, design and backwashing process

Biological aerated filters (BAFs) have high filtration efficiency due to their tolerance of hydraulic and organic shocks are suitable for the treatment of complex and sanitary wastewater. In this study, for the first time, natural media of date kernel from Bam city was used as the BAF reactor media, with a meshing sand filter separated by a standard metal grid from the natural filter section used at the end of the reactor. This can be considered an innovation in the media and filtration. Aeration in the related reactor with 160 cm height was performed bilaterally as up-flow and continuously by nozzles throughout the reactor media. In this work, the actual effluent of the hospital wastewater treatment plant was employed as the inflow wastewater to the reactor, and its organic and inorganic parameters were measured before and after the treatment by the BAF reactor. The backwashing process was also studied in three ways: bottom backwashing (TB), top backwashing (BB), and top and bottom backwashing (TBBS), to determine the amount of water consumed and to achieve the desired result. According to the results obtained in this study, the removal efficiencies of inorganic and microbial contaminants, amoxicillin and azithromycin were obtained as follows: BOD₅: 98.48%, COD: 92.42%, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{NO}}_{3}^{ - }$$\end{document}NO3-: 99.4%, P: 93.3%, Coliforms: 97%, Color: 42.8%, Turbidity: 95%, Sulphate: 30%, TSS: 98.9%, Amoxicillin: 20% and azithromycin: 13%. In the backwashing process, the amount of water consumed in these three TB, BB, and TBBS methods were obtained 300, 164, and 118 L, respectively, So, TBBS method was selected as the optimal method. Based on the results obtained in this study, it is concluded that the BAF process with natural date kernel has a high efficiency in removing organic and inorganic contaminants from hospital wastewater, also the concentration of most of the effluent parameters was less or in accordance with EPA standard.

Nontarget analysis: A new tool for the evaluation of wastewater processes

Strategies to determine the removal efficiency of micropollutants in wastewater treatment plants (WWTPs) are widely discussed. Especially the evaluation of the potential benefit of further advanced treatment steps such as an additional tertiary treatment based on ozonation or activated carbon have come into focus. Such evaluation strategies are often based on the removal behavior of known micropollutants via target or suspected analysis. The utilization of nontarget analysis is considered to lead to a more comprehensive picture as also unknown or not expected micropollutants are analyzed. Here, the results of an evaluation via target and nontarget analysis were compared for biological treatment (BT) processes of eleven full-scale WWTPs and three different post-treatments (PTs): one sand filter (SF) and two granular activated carbon (GAC) filters. The similarity of the determined removals from target and nontarget analysis of the BTs increased significantly by excluding easily degradable "features" from the nontarget evaluation. A similar ranking of the removal trends for the BTs could also be achieved by comparing this new subset of nontarget features with a set of nine readily to moderately biodegradable micropollutants. This observation suggests that a performance ranking of BTs based either on target or nontarget analysis is plausible. In contrast to the BTs, the evaluation of the three PTs revealed that the difference of feature removal between SF and the two GACs was small, but large for the target analytes with substantially higher removal effciencies for the GACs compared to the SF. In addition to the removal behavior, the nontarget analysis provided further information about the number and quantity of transformation products (TPs) in the effluent from the BTs. For all BTs more than half (55-67%) of the features detected in the effluent were not found in the influent. A comparable proportion of TPs was also detected after GAC and sand filtration due to their microbial activities.

Advanced treatment of petrochemical wastewater by combined ozonation and biological aerated filter

The secondary effluent from a petrochemical wastewater treatment plant was treated by biological aerated filter (BAF) before and after ozonation, namely BAF1 and BAF2, respectively. The results showed that BAF2 fed with the ozonized secondary effluent exhibited a high efficiency in degrading organic pollutants. The removal efficiency of COD and NH₄-N was 6.0 ± 3.2 and 48.2~18.6% for BAF1 and 12.5 ± 5.8 and 62.1~40.9% for BAF2, respectively, during the whole operation. The integration system of ozonation and BAF could tolerate a higher organic loading rate. When HRT decreased from 4 to 1 h, COD removal efficiency decreased from 12 to 4% for the BAF1 system, but it kept almost unchanged at high levels of 27-32% for the ozonation-BAF2 system, with around 20% removal by ozonation. The biomass in BAF2 exhibited a higher activity of protease, DHA, and SOUR than that in BAF1. The organic pollutants in influent and effluent of BAF were mainly ester compounds, which were difficult to biodegrade by BAF. The predominant genera in BAF1 were Gemmatimonadaceae uncultured, Thauera, and Thiobacillus, while the dominant genera in BAF2 were Nitrospira, Gemmatimonadaceae uncultured, and Flexibacter, respectively. Overall, BAF2 performed better than BAF1 in organic pollutant removal and microbial activity. The ozonation process was vital for BAF to treat petrochemical secondary effluent.

The recent development of advanced wastewater treatment by ozone and biological aerated filter

The combination of ozone and biological aerated filter (O₃/BAF) has been widely studied and applied in polishing different biological secondary effluents. O₃/BAF has the advantages of high pollutants removal rate, low operating cost, and flexible combination types. The principle and combination, effect of ozone dosage and influent suspended solids (SS) on O₃/BAF, applications, current research focuses, and development are discussed. The ozone can break refractory macromolecules into small and biodegradable fragments, increasing the biodegradation. It benefits the operation of BAF. The coupling of ozonation and BAF is efficient in the removal of refractory organic pollutants from different wastewaters. Ozonation can also be used as the post-treatment option after BAF to guarantee the effluent qualities. Normally, the ozone dosage varied from 5 to 125 mg/L with the contact time of 4 to 60 min, while the hydraulic retention time (HRT) of BAF is usually between 2 to 5 h when treating different biological effluents. The effluent COD is normally lower than 50 mg/L. Most of the organic micropollutants (OMPs) in the biological effluent, such as antibiotics, pharmaceuticals, personal care products, steroid hormones, and industrial chemicals, can be efficiently removed by O₃/BAF. More importantly, the O₃/BAF can obviously reduce the toxicity of the wastewater. The residual ozone of about 0.2 mg/L in the ozonation effluent benefits the performance of BAF. The future trends of O₃/BAF are also discussed in the paper.

The effect of toxic carbon source on the reaction of activated sludge in the batch reactor

The toxic carbon source can cause higher residual effluent dissolved organic carbon than easily biodegraded carbon source in activated sludge process. In this study, an integrated activated sludge model is developed as the tool to understand the mechanism of toxic carbon source (phenol) on the reaction, regarding the carbon flows during the aeration period in the batch reactor. To estimate the toxic function of phenol, the microbial cells death rate (k_death) is introduced into the model. The integrated model was calibrated and validated by the experimental data and it was found the model simulations matched the all experimental measurements. In the steady state, the toxicity of phenol can result in higher microbial cells death rate (0.1637 h^-1 vs 0.0028 h^-1) and decay rate coefficient of biomass (0.0115 h^-1 vs 0.0107 h^-1) than acetate. In addition, the utilization-associated products (UAP) and extracellular polymeric substances (EPS) formation coefficients of phenol are higher than that of acetate, indicating that more carbon flows into the extracellular components, such as soluble microbial products (SMP), when degrading toxic organics. In the non-steady state of feeding phenol, the yield coefficient for growth and maximum specific growth rate are very low in the first few days (1-10 d), while the decay rate coefficient of biomass and microbial cells death rate are relatively high. The model provides insights into the difference of the dynamic reaction with different carbon sources in the batch reactor.

Towards physicochemical and biological effects on detachment and activity recovery of aging biofilm by enzyme and surfactant treatments

In order to explore physicochemical and biological effects on detachment and activity recovery of aging biofilm by enzyme and surfactant treatments, two kinds of biofilm processes, i.e. biological aeration filter (BAF) and moving bed biofilm reactor (MBBR), and multiple indicators including water quality, biofilm morphology, activity and microbial community structure, were employed. Results showed that detachment of aging biofilm was mainly attributed by extracellular polymeric substance (EPS) solubilization and dispersion, and activity recovery of aging biofilm mainly depended on biological effects of dominant bacteria. Phosphorus metabolism related bacteria, such as Microbacterium and Micropruina, were responsible for BAF biofilm regeneration. More abundant microbial community structure of MBBR regenerated biofilm was found, and biofilm activity was not only related to phosphorus metabolism related bacteria, but also to denitrifying bacteria. Rhamnolipid performed best on aging biofilm detachment and regeneration, giving a clue for effective activation of aging biofilm in wastewater treatment systems.

Advanced treatment of sodium dithionite wastewater using the combination of coagulation, catalytic ozonation, and SBR

A combined process of coagulation-catalytic ozonation-anaerobic sequencing batch reactor (ASBR)-SBR was developed at lab scale for treating a real sodium dithionite wastewater with an initial chemical oxygen demand (COD) of 21,760-22,450 mg/L. Catalytic ozonation with the prepared cerium oxide (CeO₂)/granular activated carbon catalyst significantly enhances wastewater biodegradability and reduces wastewater microtoxicity. The results show that, under the optimum conditions, the removal efficiencies of COD and suspended solids are averagely 99.3% and 95.6%, respectively, and the quality of final effluent can meet the national discharge standard of China. The coagulation and ASBR processes remove a considerable proportion of organic matter, while the SBR plays an important role in post-polish of final effluent. The ecotoxicity of the wastewater is greatly reduced after undergoing the hybrid treatment. This work demonstrates that the hybrid system has the potential to be applied for the advanced treatment of high-strength industrial wastewater.

Photocatalytic efficiency of Fe2O3/TiO2 for the degradation of typical dyes in textile industries: Effects of calcination temperature and UV-assisted thermal synthesis

The inadequate management practices in industrial textile effluents have a considerable negative impact on the environment and human health due to the indiscriminate release of dyes. Photocatalysis is one of the diverse advance oxidation processes (AOPs) and titanium dioxide (TiO₂) is recognized for its high oxidation and reduction power. A composite photocatalyst of Fe₂O₃/TiO₂ is synthesized using different mass ratios of Fe:TiO₂ to improve its photoactivity. The composite photocatalyst is calcined at 300-900 °C. Their photocatalytic activity for the degradation of Congo red (CR) and methyl orange (MO) is investigated by total organic carbon (TOC) analysis. The formation and characterization of the as-prepared composite are studied by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The effect of calcination temperature on the composite Fe₂O₃/TiO₂ photocatalyst is investigated using Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity and the phase conversion are studied by X-ray diffraction (XRD). The specific surface area of photocatalysts at different calcination temperatures is investigated based on Brunauer-Emmett-Teller (BET) surface area analysis. Results show that at an optimum calcination temperature of 300 °C for the photocatalyst preparation, the specific surface area is maximum and the photocatalyst has the highest photoactivity. Thus, the degradation of organic materials reaches 62.0% for MO and 46.8% for CR in the presence of Fe₂O₃/TiO₂ (0.01 w:w Fe:TiO₂) calcined at 300 °C with the highest specific surface area (98.73 m²/g). The transformation of TiO₂ from anatase to rutile is facilitated by high temperature and high concentration of iron while high crystallization and particle size increase occur. An optimum calcination temperature of 300 °C is found at which the degradation of typical dyes in textile industries is maximum.

Ozonation in water treatment: the generation, basic properties of ozone and its practical application

The widespread applications of ozone technologies are established on the basis of large-scale manufacture of ozone generator and chemical reactivity of ozone. It is hence necessary to summarize the principles of ozone generation and to analyze the physicochemical properties of ozone, which are of fundamental significance to indicate its technical developments and practical applications. This review presents a summary concerning ozone generation mechanisms, the physicochemical properties of ozone, as well as the applications of ozone in water treatment. Ozone can be produced by phosphorus contact, silent discharge, photochemical reactions, and electrochemical reactions, principally proceeding by the reaction of oxygen atom with oxygen molecule. There are side reactions to the generation of ozone, however, which are responsible for ozone depletion including thermal decomposition and quenching reactions by reactive species. The solubility of ozone in water is much higher than that of oxygen, suggesting that it may be reliably applied in water and wastewater treatment. Based on the resonance structures of ozone, one oxygen atom in ozone molecule is electron-deficient displaying electrophilic property, whereas one oxygen atom is electron-rich holding nucleophilic property. The superior chemical reactivity of ozone can also be indirectly revealed by radical-mediated reactions initiated from homogenous and heterogeneous catalytic decomposition of ozone. Owing to the reliable generation of ozone and its robust reactive properties, it is worthy to thoroughly elaborate the applications of ozone reaction in drinking water disinfection and pre- or post-treatment of industrial wastewater including cyanide wastewater, coking wastewater, dyeing wastewater, and municipal wastewater. The structural characteristics of ozone reactors and energy requirement of applied technologies are evaluated. In addition, future directions concerning the development of ozone generation, ozone reactivity, and industrial wastewater ozonation have been proposed.

Effective degradation of methylisothiazolone biocide using ozone: Kinetics, mechanisms, and decreases in toxicity

Methylisothiazolone (MIT) is a common biocide that is widely used in water-desalination reverse-osmosis processes. The transformation of MIT during water treatment processes is poorly understood. The kinetics and mechanisms involved in the degradation of MIT during ozonation were investigated in this study. Ozonation was found to be a useful way of degrading MIT in water, and the degradation rate constant was 0.11 (±0.1) × 10³ L/(mol·s). The degradation rate constant did not change when the pH was increased from 3 to 9. The pre-exponential factor A and the activation energy E_a for the ozonation process were 7.564 × 10¹³ L/(mol·s) and 66.74 kJ/mol, respectively. The decrease in the MIT concentration and the amount of ozone consumed were measured, and the stoichiometric factor α for the ozone consumption to MIT removal ratio was found to be 1.8. Several ozonation products were detected using time-of-flight mass spectrometry. Almost 32% of the organic sulfur in the MIT was oxidized to release sulfate ions, which caused a decrease in pH. Sulfur atoms were oxidized to sulfone species and then hydrolyzed to give sulfate during ozonation. Addition reactions involving carbon-carbon double bonds and the oxidation of α-carbon atoms also occurred. MIT was found to be lethal to Daphnia magna Straus (D. magna) with a median lethal concentration of 18.2 μmol/L. Even though the primary ozonation products of MIT still showed some toxicity to D. magna, ozone could minimize the toxic effect after a long reaction time.

Advanced treatment of oilfield production wastewater by an integration of coagulation/flotation, catalytic ozonation and biological processes

In this study, advanced treatment of heavily polluted oilfield production wastewater (OPW) was investigated employing the combination of coagulation/dissolved air flotation, heterogeneous catalytic ozonation and sequencing batch reactor (SBR) processes. Two SBR reactors were separately set up before and after the ozonation unit. The results show that microbubble flotation was more efficient than macrobubble flotation in pollutant removal. Catalytic ozonation with the prepared Fe/activated carbon catalyst significantly enhanced pollutant removal in the second SBR by improving wastewater biodegradability and reducing wastewater microtoxicity. The treatment technique decreased oil, chemical oxygen demand and NH3-N by about 97%, 88% and 91%, respectively, allowing the discharge limits to be met. Therefore, the integrated process with efficient, economical and sustainable advantages was suitable for advanced treatment of real OPW.

Souza SMA. Photochemical UVC/H2O2 oxidation system as an effective method for the decolourisation of bio-treated textile wastewaters: towards onsite water reuse

A photochemical UVC/H₂O₂ oxidation system was applied for the decolourisation of two real textile wastewaters collected after biological oxidation from two different textile wastewater treatment plants.