Subjects -> WATER RESOURCES (Total: 160 journals)
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 Journal of Water Chemistry and TechnologyNumber of Followers: 8      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1934-936X - ISSN (Online) 1063-455X Published by Springer-Verlag  [2469 journals]
• Analyzing the Process of “Hungry” Regeneration in Two-Flow
Countercurrent Filters

Abstract: Although the use of countercurrent filters can significantly reduce the consumption of reagents in traditional water treatment technologies, it has a number of shortcomings. Among them are clogging with small particles of a cation-exchange resin in the upper drainage system, blocking water supply during the process of regeneration, partial engagement into ion exchange for the cation-exchange resin located above the drainage system, and others. Considering that the exchange capacity of the cation-exchange resin in both the upper and lower sections depends on the composition of initial water, the specific flow rate of a reagent for regeneration, the height of the overall, upper, and lower cation-exchange resin sections, the concentration and flow rate of a regeneration solution, the water flow rate through the cation-exchange resin layers, and other numerous factors, it is possible to conclude that estimating the height, at which the middle drainage system should be installed, is an important problem requiring a particular extensive study. Laboratory studies have demonstrated that, when the middle drainage system is installed at a height of 70% of the overall cation-exchange resin heigh counted from the bottom, the alkaline front of initial water enters the lower section without creation of “sliding” due to the neutralization of H+ ions in the upper section. The objective of this study is to investigate the problem of preparing the water of required quality for heating networks during the regeneration of two-flow countercurrent filters in the regime of “hungry” regeneration with a stoichiometric amount of acid instead of estimating the heigh of installing the middle drainage system. It can be seen from the obtained results that the exchange capacity of the sulfonated coal cation-exchange resin generally depends on the specific flow rate of sulfuric acid. In the process of study, the specific flow rate of sulfuric acid used as a regenerating solution is increased from 10 to 25 m/s to compare the results. Hence, in the process of regeneration, it can be seen that the exchange capacity slightly decreases with an increase in the solution flow velocity, and the working exchange capacity essentially grows when the flow rate of sulfuric acid is increased from 18 to 30 kg/m3.
PubDate: 2022-08-01

• Influence of Hydraulic Retention Time on Organic Pollutants Elimination
from Wastewater

Abstract: Presence of organic compounds from cosmetics, detergents or pharmaceuticals found in wastewater is mainly a consequence of human activity. In wastewater treatment plants (WWTPs) removal of these pollutants takes place as secondary treatment in the aeration tank. An important parameter in this treatment is hydraulic retention time, which represents the treatment period in the aeration tank, recommended for most systems of 4 to 8 h. Also, several mathematical models were developed to determine the fate and removal efficiency of organic compounds in WWTPs. One of the most used is the SimpleTreat model (“9-box” model) which was created by the National Institute of Public Health and Environment in Netherlands (RIVM). The model considers 9 compartments or boxes in which the primary settler, aeration tank and secondary clarifier of a WWTP are contained separately. Each basin has a liquid (water) and a solid phase (suspended solids) in which the pollutant may be dissolved and/or adsorbed, respectively. Estimations of the organic compound concentration values may be determined in each WWTP basin and also discharged via effluent. All values are expressed in percentage from compound nominal concentration in influent representing the removal efficiency. This study presents estimations with the SimpleTreat model of the removal efficiency of six organic compounds found in products as: cosmetics—Tonalide (AHTN), decamethylcyclopentasiloxane (D5) and edetic acid (EDTA); detergents—benzalkonium chloride (BAC) and pharmaceuticals—Permethrin (PMT) and Atenolol (A). Depending on their chemical properties, these compounds may be found in influent mostly dissolved in the liquid phase or mostly adsorbed on the surface of the suspended solids. The removal efficiency is evaluated after 2, 5, and 10 h of retention in the aeration tank.
PubDate: 2022-08-01

• Removal of Formaldehyde from Aqueous Solution by Hydrogen Peroxide

Abstract: Formaldehyde (HCHO) is a common chemical raw material and one of the major constituents in wastewaters from the production of chemical products. HCHO in wastewater is mainly removed by adsorption, biodegradation, and advanced oxidation. The objective of this study is to investigate transition metal oxides (Fe2O3, Co2O3, Ni2O3, CuO, ZnO) without pretreatment for enhancing the oxidation of HCHO. The oxidation of HCHO in wastewater by hydrogen peroxide using transition metal oxides as catalysts is studied. The concentration of HCHO in waste water was measured by indirect method. HCHO reacts with 2,4-dinitrophenylhydrazine in the presence of acetic acid to produce 2,4-dinitrophenylhydrazone. 2,4-Dinitrophenylhydrazone increases in proportion to the concentration of HCHO. The HCHO removal rate is determined by quantitative analyses of 2,4-dinitrophenylhydrazone using high-performance liquid chromatography (HPLC). The catalytic oxidation experiments are performed in test tubes at 25°C. The results indicate that the catalytic activity of the transition metal oxides towards HCHO oxidation is very different. The removal rate of HCHO was attributed to the number of hydroxyl radicals formed in the system. CuO shows higher catalytic activity in the oxidation of HCHO. The effect of the temperature, the mole ratios of hydrogen peroxide to HCHO, and the amount of CuO on the removal rate of HCHO were studied. Results of experiments show that the HCHO is almost wholly oxidized (>98%) at the best conditions (molar ratio of hydrogen peroxide to HCHO is 2.5, CuO is 0.06 g, 25°C for 15 min). CuO also offers the advantages of simple recovery from the treated solution and repeated use. It is hypothesized that CuO can transform hydrogen peroxide into active oxygen that has higher oxidation activity. But, the rate of formation and removal of free radicals HO· is very fast in the presence of transition metal oxides (Fe2O3, Co2O3, Ni2O3, ZnO).
PubDate: 2022-08-01

• Performance of Modified Cellulose Acetate Polyethylene Glycol Composite
Membrane with Fe3+ Saturated Montmorillonite in Water Treatment

Abstract: A novel membrane was prepared by modifying cellulose acetate polyethylene glycol (CA/PEG) membrane with Fe3+ saturated montmorillonite (Fe3+ MMT) by phase inversion process for enhancement of bacterial removal and antibacterial efficiency in water treatment. The pristine and modified membranes were characterized by Fourier Transform Infrared (FTIR) spectroscopy which revealed the characteristic functional groups present in them. SEM image of the modified membrane showed the surface morphological characteristics. The effect of incorporation of Fe3+ MMT (1, 2, 3, 4, and 5 (wt %)) in the performance of CA/PEG membranes was evaluated by pure water flux (PWF), bacterial removal efficiency and antibacterial activity. The results show that modified membranes have higher bacterial removal efficiency, antibacterial activity and PWF as compared to pristine membrane. An increase by 46% in bacterial removal and antibacterial activity and 300% in PWF were obtained by modified CA/PEG membrane with 5% addition of Fe3+ MMT when compared with pristine membrane. SEM image of the Fe3+ MMT modified CA/PEG membrane after treatment showed the presence of trapped distorted bacteria, confirming antibacterial activity. The enhanced antibacterial efficiency reduces biofouling in Fe3+ MMT modified CA/PEG membrane thus increasing its effective time of usage in water treatment. The Fe3+ MMT CA/PEG membrane therefore provides an economic and effective treatment alternative for water purification. Since 100% efficiency for bacterial removal was not attained in this study, further investigations could be carried out with Fe3+ MMT CA/PEG membrane under lower flux rates by controlling the pressure during filtration.
PubDate: 2022-08-01

• The “Plus” of the Outer Surface of a Magnetic Layered Double Hydroxide
for Arsenic Removal from Water: Synthesis and Adsorption Aspects

PubDate: 2022-08-01

• Assessment of the Ability of Processed Squeezed Nigella sativa Seeds to
Effectively Remove Cadmium and Nickel Ions Form the Aqueous Solutions

Abstract: Present work used squeezed processed Nigella sativa seeds (PSNS) for water remediation for the first time. (PSNS) has no recorded use in literature. Present work used Nigella sativa seeds after extracting oil which have several medical uses. PSNS shows high performance for water remediation according to present study, in addition it is safe edible material. Processed squeezed Nigella sativa seeds (PSNS) were used for the removal of cadmium and nickel ions form the aqueous solutions. PSNS was characterized by energy-dispersive X-ray spectroscopy (EDS) which indicate that major elements present in PSNS surface are carbon, nitrogen and oxygen elements with other minor elements such as potassium, calcium and magnesium, and Fourier-transform infrared (FTIR) before and after metal ion removal to indicate functional groups responsible for the adsorption. Scanning electron microscopy (SEM) images and Brunauer–Emmett–Teller (BET) indicate the low porosity of PSNS and small surface area. Batch experiments were conducted to study metal ions removal indicated that Cd and Ni ions required 30 and 60 min to reach equilibrium respectively. Studies on metal ion solution pH indicated that pH 5 and 4 have the highest metal ion removal for Cd and Ni respectively. As PSNS Particle size decrease the amount of the metal ions removed increases. isothermal studies indicated that adsorption of Cd fit to Langmuir isotherm and Ni to Freundlich isotherm. Kinetic studies showed that adsorption of Cd and Ni fit to pseudo second order kinetic model which means that adsorption on PSNS is chemisorption with adsorption capacity of 9.78 and 4.53 mg g–1 for Cd and Ni ions respectively. According to the enthalpy data of thermodynamic study, adsorption of Cd is exothermic process, but it is endothermic for Ni ion.
PubDate: 2022-08-01

• Carbon-Magnetic Layered Double Hydroxide as a New Nanosorbent for
Efficient Removal of Tartrazine and Indigo Carmine Dyes from Water
Solutions; Multivariate Optimization and Adsorption Characterization

Abstract: A simple co-precipitation method was employed in the synthesis of carbon-magnetic cobalt aluminum layered double hydroxide (Fe3O4/Co–Al LDH) and the obtained nano-structured material was further applied as an innovative adsorbent for the removal of two anionic dyes, namely Tartrazine (TA) and Indigo Carmine (IC). The synthesized nanosorbent was identified by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). In addition, Fe3O4/C/Co–Al LDH was magnetic and easily recovered by a small bar magnet after the sorption operation. The batch adsorption experiments were carried out to optimize different essential parameters such as contact time, initial dye concentration, solution pH, and adsorbent mass. Response surface methodology (RSM) involving central composite design (CCD) was also employed to obtain a suitable regression model for adsorption system and subsequently investigate the most influential parameters. Based on ANOVA results, all of the main parameters were significant. In particular, the initial dye concentrations and sorbent mass let to the largest variances on response values. The results showed the removal percentage of the dye increased by increase in the amount of the nanosorbent. In the contrary, the adsorption value of the nanosorbent for dye decreased by increasing the sorbent amounts. Moreover, the removal percentage and the adsorption value of the adsorbent decreased for each dye in the presence of another dye due to the competition between dyes for the available adsorbent surface area. Furthermore, the pseudo second-order model was used to describe the adsorption kinetics. The Langmuir isotherm model was the most suitable to fit the experimental data. The sorption capacities for TA and IC were obtained to be 52.3 and 61.7 mg/g, respectively.
PubDate: 2022-08-01

• Effect of the Electroconductivity of an Electrofilter Load on the
Mechanism, Efficiency, and Energy Consumption of Water Purification from
Dispersed Impurities

Abstract: The electrical retention of charged dispersed contaminants on an electrofilter loaded with electrically conductive and non-conductive dispersed particles (ion-exchange resin KU-2-8 and clinoptilolite) was experimentally studied. The used model dispersed contaminant was an anion-exchange resin, whose surface charge sign was opposite to the load charge. The studies were performed in the potentiostatic regime at an interelectrode voltage ranged from 5 to 90 V. At the same time, the current–time dependence was measured at different loads and electrolyte concentrations. The character of dependence between the water purification degree and the electrical field intensity, the water or electrolyte flow rate through the electrofilter, and the concentration of used electrolyte solutions was analyzed. Clinoptilolite was shown to provide the same degree of water purification from dispersed contaminants as for the cation-exchange resin, but at a slightly lower current and a voltage higher by several times. Hence, the purification of water from dispersed impurities on an electrofilter loaded with ion-exchange resin particles was more profitable from the viewpoint of energy consumption as compared to clinoptilolite. The dependence of the electrical field distribution in the electrofilter on the electrical conductivity of a load and its effect on the electrophoresis and dipolophoresis of load particles at different charge values was theoretically analyzed. The replacement of the electrically conductive load by the non-conductive one was shown to have an effect on the conditions for the transport of contaminant particles to the load surface and the location of a sediment with respect to the hydrodynamic flow and, thereby, on the character and efficiency of their electrical retention on the electrofilter. Taking into account these factors, the load of electrically conductive particles was concluded to have a higher efficiency in good agreement with experimental data.
PubDate: 2022-08-01

• Comparison of Conventional and Ultrasonic-Assisted Adsorption Processes by
Using H3PO4 Activated Cypress Tree Cone for Methylene Blue Removal

PubDate: 2022-08-01

• N/O-Rich Porous Carbon Adsorbent from Coffee-Residue toward Ni(II) Removal
from Surface Water

PubDate: 2022-08-01

• Photometric Analysis of Pentachlorophenol in Water by Extraction with
Astrafloxin

Abstract: Pentachlorophenol (PCP) and astrafloxin FF (AF), a polymethine dye, were shown to form an ionic associate (IA), which could be rather perfectly extracted by different aromatic hydrocarbons. A maximum extraction of the ionic associate was attained at pH 8–12, being in quite a good agreement with the data obtained by calculating the distribution diagrams of corresponding dye and PCP forms. The distribution diagrams of these forms were calculated and constructed by using the MarvinScetch software. The effect of the dye concentration on the absorbance of the toluene extracts of PCP–AF ionic associates was studied. The PCP recovery attained a maximum at a dye concentration of (1.6–2.8) × 10–4 M. Extraction equilibrium was established for 50–60 s. The stoichiometry of the PCP–AF ionic associate was studied by the spectrophotometric methods of isomolar series and equilibrium shift, and the ratio of components was 1 : 1. The scheme of the formation and extraction of this ionic associate was proposed. The conventional molar absorption coefficient of the ionic associate was 1.2 × 105. The calibration curve of the extract absorbance as a function of the PCP concentration could be described by the linear equation А = 0.0121 + 0.0622c within a PCP concentration range of 1.2–60.3 μg/cm3. The PCP detection limit calculated by the 3s-criterion (n = 5, Р = 0.95) was 1.08 μg/cm3. The intralaboratory disperancy of the calibrating plot for PCP analysis with astrafloxin was estimated by the Cochran test G. The calculated Cochran test (n = 5, P = 0.95) was smaller than its tabular value: Gcalcd = 0.27 < Gtab = 0.64 to argue for variance homogeneity. A method for the extraction photometric analysis of pentachlorophenol in water and bottom sediments was developed.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030079

• Treatability and Kinetic Study of Dairy Effluent Using Microalgae
Spirulina platensis in a Laboratory Scale Batch Reactor

Abstract: Purpose of this research work is to evaluate the bio kinetic coefficients of a pretreated Dairy wastewater in a suspended growth batch reactor with the treatment of microalgae Spirulina platensis. The study was performed in a laboratory scale batch setup. Samples of dairy plant was collected and it was pretreated with a consortium of carbon oxidation and nitrification process with bacterial culture that was made as the feed of this purification process. Bacterial pretreatment was done in order to reduce its organic carbon and ammonium nitrogen content. Nitrate nitrogen which was formed during bacterial treatment process and most of the phosphate still remaining in the water was treated in this process with micro algal species to remove these nutrients in wastewater and consequently to meet with discharge standards of regulatory authorities like Central Pollution Control Board (CPCB) of India and World Health Organization (WHO). A simulated synthetic wastewater sample was prepared according to the concentration measured in the original pretreated-wastewater where average nitrate nitrogen concentration was found 54 mg/L and phosphate concentration was 16 mg/L. The maximum 99.00 and 90.38% of nitrate nitrogen ( $${\text{NO}}_{3}^{ - }$$ -N) and phosphorus ( $${\text{PO}}_{4}^{{3 - }}$$ -P) removal were achieved corresponding to initial nitrate nitrogen and phosphorus concentration of 54 and 16 mg/L respectively, with an initial inoculum concentration of microalgae Spirulina platensis of 0.8% v/v after 8 days of detention period in batch reactor. Kinetics study was also carried out to obtain bio-kinetic coefficient for nitrate nitrogen and phosphorus removal using microalgae Spirulina platensis in order to obtain kinetic constants (Y, Ks and k). The values of k, Ks and YN were found to be 21.74 per day, 1.61 mg/L and 0.011 g of biomass/mg of $${\text{NO}}_{3}^{ - }$$ -N as N for nitrate nitrogen removal. Values of k, Ks and YP were found to be 14.49 per day, 16.63 mg/L and 0.052 g of biomass/mg of $${\text{PO}}_{4}^{{3 - }}$$ -P as P for $${\text{PO}}_{4}^{{3 - }}$$ -P removal. Corresponding kinetic coefficients were compared to studies done by other researchers which corroborate the findings of this present investigation.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030031

• A Model-Based Approach to Study the Effect of Temperature in Plant-Wide
Biological Wastewater Treatment Plants

Abstract: The effect of temperature on phosphorous, nitrogen, organic matter removal, overall effluent quality, methane, and hydrogen production in an activated sludge system (ASS) is assessed in this research. For the plant-wide model of the ASS, benchmark simulation model (BSM2-P) with an ASS (ASM2d) is used and the temperature is selected between 10 to 35°C covering different seasons. A steady-state simulation is carried out to evaluate the effluent compositions by changing kinetic parameters. A total of fourteen kinetic expressions for the maximum growth rate of heterotrophic biomass, autotrophic, phosphate accumulating organisms and their decay rates, oxygen saturation, hydrolysis, fermentation and oxygen mass transfer coefficients are also considered. Improved removal efficiency of NH, TN, TP, COD, and BOD5 is obtained at 17, 20, 10, 20, and 28°C temperatures respectively. The average percentage of removal is obtained as 22.2, 9.7, 28, 1.7, and 86.4% respectively for NH, TN, TP, COD, and BOD5 which is higher when compared to the removal rate at 15°C. Further, the anaerobic digestion model (ADM1) is also used with changing physico-chemical parameters which are functions of temperature. The corresponding physico-chemical parameters are analysed in the range of 25 to 55°C. A total of seven physico-chemical kinetic expressions for the acid-base equilibrium gases are considered which includes Henry’s law coefficient for carbon dioxide, methane, hydrogen, and partial pressure of water. At higher temperature (55°C) the ADM1 showed improved production efficiency rates for carbon dioxide and hydrogen but at lower level (25°C) it showed lower production efficiency rates. The average production rates of methane, hydrogen, and CO2 at 55°C different by –0.01, 54.1, and 7.8% respectively when compared at temperature of 28°C. This knowledge of varying temperature leads to the operator to handle biological treatment for wastewater in a quality manner with an optimal operational cost.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030110

• Isolation and Identification of Benzoate Degrading Bacteria from Food
Industry Effluent

Abstract: Sodium benzoate, the sodium salt of benzoic acid, is the first accepted and one of the widely used chemical preservatives in the food, cosmetic and, beverage industries. In recent past, soaring demand of packaged food resulted in increased industrialization and intensified use of chemical preservatives. The residual remains of these industries are discharged into their wastewater treatment plants (WWTP) and effluent treatment plants (ETP) thus concentrating the chemical preservatives in these treatment plants. This causes harmful effects on the growth of indigenous microbes in treatment plants and reduces the effectiveness of biological processes in secondary wastewater treatment. Therefore, it is necessary to degrade preservatives like sodium benzoate in the WWTP/ETP of industries. The ETP samples were collected from food processing industry for the isolation of sodium benzoate degrading aerobic bacteria. The microscopic analysis of the isolate with maximum ability to grow at a very high concentration of sodium benzoate (10 000 mg/L) showed it to be Gram-positive, endospore forming bacteria. The molecular characterization was done using 16S rDNA sequencing with universal primers and the isolate was identified as Bacillus subtilis DSSK1. The sequence was submitted to NCBI GenBank with accession number MT704505. The isolate was able to utilize sodium benzoate as the sole carbon and energy source. It was able to degrade 76% of sodium benzoate (10 000 mg/L) in 72 h. It was also able to produce hydrolytic and oxidative enzymes (cellulase, amylase, pectinase and laccase) which can help it to better survive in the food industry effluent rich in cellulose, starch, pectin, and lignin thus making it a promising candidate for industrial effluent treatment rich in benzoate.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030080

• Inhibition of Multi Drug Resistant Bacterial Species, Scandinavium
goeteborgense CCUG 66741 and Aeromonas veronii CRC6 Isolated from a Waste
Water Treatment Facility Using Nanocomposites

Abstract: Antibiotic resistance is currently one of the most serious challenges to global health and socio-economic development. New resistance mechanisms are arising and spreading throughout the world, posing a danger to our ability to treat common infectious diseases. Antibiotics are released into the environment mostly through wastewater treatment plants. Antibiotics’ presence may favour the selection of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). ARBs were isolated from a treated municipal wastewater sample. The resistant bacteria which were morphologically different and more in numbers were tested for multiple drug resistance. Two colonies were found to be resistant to the antibiotics, ampicillin, erythromycin, rifampicin, and chloramphenicol. These bacterial colonies were identified as Scandinavium goeteborgense CCUG 66741 and Aeromonas veronii CRC6 using 16S rRNA gene sequencing. These bacteria were also found to be sources of high-risk contamination with Multiple Antibiotic Resistance (MAR) Index of 0.6. They are not only multiple drug-resistant but human and animal pathogens. Further, they were evaluated for inhibition by nanocomposites (Ag0NP@GO and Ag0NP@rGO) at 500 mg/L using the agar well diffusion method. Both the bacteria were inhibited by the nanocomposites, showing a significant clearing zone with more inhibition caused by Ag0NP@rGO. Overall, the antibacterial action of the synthesized nanocomposite can be probably explained as the “Trap and Kill” mechanism. In particular, GO nanosheet with 2D structure and surface functional groups and charges help to bind the bacterial cells like a trapping agent whereas, silver nanoparticles embedded in GO sheet inactivate the bacterial cell. Growth curve analysis also showed a longer lag and a shorter log phase in the presence of nanocomposites, indicating effective antimicrobial activity.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030043

• Fabrication and Characterization of Low-Cost Tubular Ceramic Membrane for
Microfiltration of Oily Wastewater

Abstract: The presence of notable quantities of oil in water is one of the prime causes of water pollution worldwide. The increased water pollution is creating nuisance to human and animal lives. To put an end to this threat, the treatment of oily wastewater is attracting everyone’s attention. The high efficacy of membrane filtration in separation operations makes researchers consider this technology for use in oily wastewater treatment. Hence, keeping this perspective in mind, tubular configuration membranes were fabricated using kaolin (30 wt %), quartz (30 wt %), calcium carbonate (28 wt %), boric acid (4 wt %) and feldspar (8 wt %). Membrane fabricated with this composition is found to possess a porosity value of 59.27 ± 1.002% and mechanical strength of 14.708 ± 2.603 MPa along with an average pore size of 0.092 μm. The surface of the membrane is smooth and free of any defects as observed under field emission scanning electron microscope. The membrane, due to its satisfactory physical and mechanical properties, is further used for the treatment of oily wastewater with three various concentrations and complete rejection of oil is achieved for all the concentrations. The successful separation of oil from the oily wastewater signifies size exclusion to be the dominant phenomenon for the rejection performance of the membrane. The droplet size distribution of the oil-in-water emulsion using laser particle size analyzer also reveals the same, with an average droplet size of oil lying between 2.884–3.802 μm for all three concentrations. The size of the droplets is far bigger than the average pore diameter of the membrane, which ultimately helps the membrane in retaining the oil content of wastewater. Therefore, looking at the outstanding oil removal efficiency of the membrane, it can be concluded that the membrane can be used industrially for the treatment of oily wastewater.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X2203002X

• Estimation of Returned Sludge Using Artificial Neural Network and Fuzzy
Inference System (Case Study: Shahrake-Gharb Waste Water Treatment Plant,
Tehran)

Abstract: The amount of returned sludge is considered as one of the important and controllable parameters in the operation of wastewater treatment plants and play a vital role in process. There are different approaches to measure the rate of the returned sludge from secondary sedimentation to aeriation tank but all of them rely on the results of tests that are done after the process. Therefore, determining dynamic estimation methods is very important. In the present study, artificial neural network (ANN) models and adaptive fuzzy-neural inference system (ANFIS) were used to achieve this goal. First, different compositions according to the quality parameters of wastewater such as sewage inlet flow, BOD5, temperature, TDS, TS and returned sludge flow with time delay were considered as input, and the amount of returned sludge as network output. Then, by training the network and determining the desired structure based on the type, number of membership functions and related laws, and using MATLAB software, the most appropriate model were obtained based on statistical data, the mean squared error and the efficiency of the coefficient of determination model. As a result, the inputs were introduced as the most suitable model by combining a one-dimensional Sugeno inference system with relevant membership functions. The results of different methods were compared and finally, a Genfis2 model, which is moderation of ANFIS systems, with a training coefficient above 93% (MSE = 0.0081 and RMSE = 0.0898) and a validation coefficient above 91% (MSE = 0.0027 and RMSE = 0.0518) was selected and presented for accurate estimation of the amount of returned sludge up to the next 24 h. This study was done with comprehensiveness and practicality for the first time in Iran and could lead to prevention of polluting the receiving waters.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030092

• Comparing the Efficiency of Photocatalytic Humic Acid Destruction in Water
with Oxygen and Hydrogen Peroxide on (N,Fe)-Doped Titanium Dioxide Samples
in Different Irradiation Modes

Abstract: Titanium dioxide, one of the most important photocatalysts for the oxidation of compounds dissolved in water, is active only under ultraviolet irradiation and inactive in the visible spectral region due to its broad bandgap. A promising strategy for the creation of active TiO2 samples able to efficiently utilize visible sunlight and thereby to essentially decrease the cost of the photocatalytic treatment of natural and waste water is the introduction of several dopants. The efficiency of nitrogen doped and nitrogen and iron ion codoped titania samples synthesized by the sol-gel method with a bandgap narrowed to 2.59–2.99 eV in the photocatalytic destruction of humic acid (HA) in water (C = 55–60 mg/dm3) with atmospheric oxygen and hydrogen peroxide was studied depending on pH and a radiation source: an SVD-120 mercury quartz lamp (λ > 200 nm) or a GE CMG70 metal halide lamp (λ > 360 nm). The efficiency of doped TiO2 samples in the photocatalytic oxidation of aqueous HA solutions depended on the iron content (0–1% of Fe), the used oxidant, pH of the medium, and the irradiation mode. A much higher degree of HA destruction was attained in an acidic medium (pH0 2.4) as compared to a neutral medium (pH0 7) in both irradiation modes. The application of hydrogen peroxide increased the degree of photocatalytic HA mineralization in the presence of all the synthesized samples in both irradiation modes as compared to the oxidation with dissolved oxygen and essentially approached the efficiency of synthesized photocatalysts to standard Degussa P-25 TiO2. On the whole, N-TiO2 was most active among the synthesized photocatalysts. No clear dependence of the HA destruction degree on the Fe content in the samples (Fe,N-TiO2; 0.25–1.0%) were established at studied destruction parameters. In general, the codoped samples (Fe,N-TiO2) essentially inhibited HA destruction and, in a neutral medium, the inhibiting effect became stronger with increasing iron content in a sample in both irradiation modes. It seems probable that the recombination of photogenerated electron–hole charge carriers was intensified due to the selected method of N-TiO2 codoping with Fe3+ ions or the range of dopant concentrations.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030055

• A Feasibility Study on Synergistic Effect of Radical Sulfate Activated by
Ozone on Explosive Degradation by Performance of Taguchi Design Method

Abstract: Millions of tons of nitroaromatic explosives are produced worldwide for military purposes and other applications. These substances lead to the accidental release of energetic materials, resulting in soil and groundwater pollution. Nitroaromatics are easily reducible because of their polarized N–O bands. Therefore, they are not sorbed strongly in the environment due to the intermediate character between hydrophobic and hydrophilic properties. Advanced oxidation processes (AOPs) have recently been used to degrade emerging pollutants due to generating highly oxidizing agents, such as hydroxyl radical. The main objective of this study is to examine the possibility of the persulfate/ozone (as an activator) process in explosive degradation from an aqueous solution. Experiment designs and data analysis were evaluated using the Taguchi design method considering COD and TOC removal as responses. Next, 2,4,6-trinitrotoluene (TNT) residual concentration was detected using the HPLC instrument. Finally, the most significant parameters that affected response removal were determined by variance (ANOVA) analysis. A satisfactory agreement of the quadratic model with the experimental data was confirmed by the high R2 value (close to 1). The correlation coefficient of 0.9 indicates the high validity of the obtained models for removing COD and TOC. Hence, in removing COD and TOC, a very good agreement was found between the experimental values and the predicted values of the responses. Two-third of 2,4,6-trinitrotoluene was transferred to inorganic compounds corresponding to CO2 due to the generation of oxidative species. More than 72% COD and 65% TOC removal efficiency were obtained in 60 min employing pH neutral, PS 19 mM, and 40 mg/L TNT (kt = 0.0191 min–1, pseudo-first-order kinetic model). Overall, sulfate radicals activated by ozone could be considered a promising process for nitroaromatic degradation of industrial effluent.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030067

• An Oxidoreductase Biomimetic System Based on CeO2 Nanoparticles

Abstract: With the current environmental concern on water waste related issues, there is a need to make aware of disposal wastewater safely and beneficially. This effluent can be used for agricultural purpose and it could be an important step for consideration of disposal in a proper way, treated and planned. The local studies are essential and needed to determine the quality of effluent in order to keep no loss in crop yields, soil and ground level water deterioration. Peroxidases have a wide potential in bioremediation of wastewater polluted with phenol derivatives, industrial effluents, decolourization of synthetic and natural dyes, elimination of endocrine disruptive chemicals, degradation of herbicides and pesticides, chlorinated dioxins, chlorinated alkanes and alkenes, polychlorinated biphenyls and chlorinated insecticides. Nowadays, the interest is preoccupied on nanozymes having peroxidase mimicking activities owing to their encouraging and favorable wide applications in biosensing, bioimaging and biomedicine. Brassica oleracea (broccoli) is a rich peroxidase source having activity 1.35 U/mL. UV-visible analysis and cyclovoltametric studies indicated that CeO2 NPs can substitute peroxidase under optimized conditions. CeO2 NPs efficiently oxidized α-naphthol, β-naphthol, anthracene and naphthalene with less oxidation potential respectively compared to peroxidase. On treatment of water effluent with peroxidase the value of BOD, COD and turbidity comes out to be 36, 60 mg/L and 10.03 NTU respectively. On treatment of water effluent with CeO2 NPs the value of BOD, COD and turbidity where lower and found to be 18, 28 mg/L and 5.4 NTU respectively. The result indicates that nanozyme efficiently degrades the phenolic and other aromatic compounds present in the waste distillery water discharged.CeO2 NPs behave as a catalyst by boosting the peroxidase activity twice. This preliminary study demonstrated that nanoparticle treatment of wastewater is more effective than enzymatic treatment and its use will be a cost-effective substitute to conventional technologies in India.
PubDate: 2022-06-01
DOI: 10.3103/S1063455X22030109

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