Iranian Journal of

Background and Objective: Electrochemical methods as one of the advanced oxidation processes (AOPs), have been applied effectively to degrade recalcitrant organics in aqueous solutions. In the present work, the performance of electro-Fenton (EF) method using iron electrodes on the degradation of phenol was studied. Materials and Methods: In this study, a lab-scale EF batch reactor equipped with four electrodes and a DC power supply was used for removing phenol. The effect of operating parameters such as pH, voltage, H₂O₂ and initial phenol concentration and operating time were evaluated. We added H₂O₂ manually to the reactor while iron anode electrode was applied as a ferrous ion source. Results: It was found that initial pH of the solution, initial H₂O₂ concentration, applied voltages were highly effective on the phenol removal efficiency in this process, so that 87% of phenol after 15 min of reaction at pH=3.0, voltage 26 V and H₂O₂ 100 mg/L was removed. Phenol removal efficiency decreased with increasing pH, so that at pH 10, after 15 min, efficiency was 11%. To remove 99.99% phenol at pH 3, 100 mg/L concentration of H₂O₂ and voltage 26 V for 60 min was required. Conclusion: Electro-Fenton process using iron electrodes for phenol degradation and remediation of wastewater could be a promising process.

Background and Objectives: Bakery’s yeast industry wastewater contains various pollutants and is generally characterized with high chemical oxygen demand (COD), dark color, high-nitrogen and sulfate and non-biodegradable organic pollutants. Having persistent soluble colored compounds (called melanoidins), effluent from yeast industry is a major source of water and soil pollution. The aim of this study was to evaluate advanced oxidation efficiency using Fenton process for COD and color removal from bakery’s yeast wastewater. Materials and Methods: This was an experimental- laboratory scale study. In this study, the effect of time and Fenton concentrations were tested for COD and color removal from bakery’s yeast wastewater. The sample used for this study was yeast effluent from Separator 2 with initial concentrations of COD and color of 5300 mg/L and 6950 pt-co respectively. In order to obtain the optimum operating conditions of the process, Taguchi analysis method was used. Experiments were carried out in five stages of the time in the range of 15, 30, 45, 60 and 75 min with various concentrations of hydrogen peroxide (e.g., 0.02, 0.04, 0.06, 0.08, and 0.1 molar) and concentrations of Fe²⁺ (e.g., 0.01, 0.02, 0.03, 0.04, and 0.05 molar) at pH = 3. Jar test method was used to determine the best operating conditions including: reaction time, dosages of hydrogen peroxide and Fe²⁺. Results: According to Taguchi method and SN-ratio analysis, the best H₂O₂/Fe²⁺ dosages were 0.08/0.04 molar at pH 3 and in reaction time of 30 min for removal of COD and color. For these conditions, the maximum COD and color removal efficiencies were 63 and 69 percent respectively. Based on the results, with increasing reaction time, there was no perceptible change in the removal efficiency. Conclusion: It can be concluded that Fenton’s oxidation method can be used successfully, as an alternative option to the design and choice of color and COD removal from strength industrial wastewaters e.g., bakery’s yeast industry.

Background and Objective: The presence of natural organic materials (NOM) in water resources affects its quality (i.e. color, odor, and taste). In addition, it leads to the fouling of filters and membranes and reduces water treatment efficiency during flocculation/ coagulation. Moreover, NOM reacts with disinfectants and produces byproducts (DBPs), which are harmful to human health. Magnetic nanoparticles have been reported as effective adsorbents for the removal of pollutants from the aqueous media. In this study, we applied SiO₂coating on these nanoparticles in order to enhance their stability and dispersion in aqueous media and investigated their capability in NOM adsorption from water. Materials and Methods: Iron oxide magnetic nanoparticles were prepared by co-precipitation. Then, we added Tetraethoxysilane (TEOS) to the solution in order to coat it with SiO₂ . The adsorbent characteristics were determined by SEM and XRD. Then, we carried out the adsorption experiments under different pH(3-12) and contact time (5-240 min)performance conditions. The adsorption kinetic was determined with respect to different Humic acid adsorption times. Later, we determined the effect of different concentrations of adsorbent on different concentrations of Humic acid, and Langmuir and Freundlich coefficients based on the optimum conditions. Results: The morphology investigation of adsorbent showed the average size of Fe₃O₄/SiO₂nanoparticles was 30-130 nm. The pH value of 10.5 and the contact time of 90 min at room temperature were determined as optimum conditions for removal of humic acid using Fe₃O₄/SiO₂ nanoparticles. The maximum adsorption capacity of Fe₃O₄/SiO₂ was192.30. The adsorption isotherm was fitted well by Langmuir model (R²>0.90) and the pseudo-second order model (R²>0.98) could better explain humic acid adsorption. Conclusion: Having high number of active surface sites, magnetic properties, easily separation using magnetic field, and its cost-effectiveness, the Fe3O4/SiO2 nanoparticles could be used as an efficient adsorbent in removal of humic acid from water.

Background & objective: Synthetic dyes are extensively used in various industries such as textile, leather tanning, plastic, pulp and paper. Since dyes are toxic and even carcinogenic, discharging dye-containing wastewater into the environment poses serious environmental and health problems. Therefore, the purpose of this paper was to evaluate the removal of Reactive Red 120 from aqueous solutions using surface modified natural zeolite. Materials &Methods: The Semnan zeolite was sieved using standard sieves in size of 0.2 - 0.3 mm and then was modified by cationic surfactant. Batch adsorption studies carried out to study various parameters included contact time, initial concentration of Reactive Red 120, pH, and adsorbent dosage. The concentration of dye was measured using a UV-vis Spectrophotometer at the wavelength of 537 nm. Freundlich and Langmuir isotherms and Pseudo-first order and pseudo-second order kinetics were used to analyze the isotherm and kinetic data respectively. Results: The adsorption studies indicated that increasing of the contact time, initial concentration of Reactive Red 120, decreasing pH and adsorbent dosage leads to increasing dye adsorption. Equilibration of Reactive Red 120 adsorption was reached at lapse of 90 min. Moreover, it was found that Langmuir isotherm (R2=0.9814) and pseudo second-order kinetic (R2=0.9814) are well fitted with our data. Conclusion: The results of the study show that Iranian modified zeolite can be used effectively for removal of Reactive Red 120 in comparison with other parts of the world. Considering the cost, availability and ease of modification, it can be used to remove dye in industrial wastewater.

Background & Objectives: Disposal of pharmaceutical compounds to environment as an emerging pollutants cause concerns significantly and it is necessary to use new methods of sewage treatment for removal of these compounds. The aim of this study was to investigate the inhibition effects of metronidazole before and after using UV254/H₂O₂ process on specific methanogenic activity of.anaerobic biomass. Materials & Methods: Fourteen anaerobic digestion tests were carried out at batch scale before and after using UV254/H₂O₂ process in 500 ml reactors with 30% anaerobic biomass and 70% substrate. The liquid displacement method was used. Duration of each test was in the range of 10-17 days. Results: Cumulative Biomethane production in concentrations of 1, 5, 10, 25, 50, and 100 mg/l metronidazole was 34.04, 95.12, 100.86, 3.28, 27.88, and 6.97 ml respectively. This production was 800.73, 243.54, and 10.66 ml in concentrations of 25, 50, and 80 mg/l respectively using UV254/H₂O₂ process as pretreatment at 60 min retention time. Biomethane production in concentrations of 80,120, and 150 mg/l was 377.2, 380.48, and 63.14 ml respectively at 90 min retention time. Conclusion: Different concentrations of metronidazole had an inhibition effect on anaerobic digestions and therefore the efficient pretreatment method is needed to reduce this inhibition effect. The UV254/H₂O₂ process is an effective method for degradation and conversion of metronidazole to more biodegradable compounds for anaerobic bacteria consumption and, in turn, to increase biogasproduction in anaerobic digestions.

Background & Objectives: Excessive discharge of hazardous materials such as nitrogenous and organic compounds into the environment has negative impacts on the health of the aquatic environment. The main objective of this research was focused on evaluating the feasibility of using modified SBR reactor for the removal of nitrogenous compounds and chemical oxygen demand (COD). Materials & Methods: The experiments were performed using an up-flow continuous reactor with intermittent effluent. At first, four different cycles including aeration, settling, and decant (3, 4, 6, and 8 h) were designed for the performance of the reactor. Then, the efficiency of each cycle was determined for different concentrations of COD (250-1500 mg/L) and ammonia (40-100 mg/L). Results: Data demonstrated that all cycles had very good performances for the removal of COD. The average COD removal efficiencies of phases 1 through 4 were 91.7, 91.5, 92, and 92.7% respectively. The average NH^₄₊ removal efficiencies of phase 3 and 4 were 92.7 and 95.8% respectively. Conclusion: The performance of phase 4 (with the cycle of 8 h) for the removal of nitrogen compound and COD was particularly high. The combination of anoxic and aerobic cycles in the reactor and providing nitrate as an electron receptor had the best performance for the removal of nitrogen from wastewater. Therefore, the continuous up-flow reactor was a good alternative to batch reactor in removing nitrogen compound and COD simultaneously.

Background and Objectives: Reduction of released extracellular polymeric substances (EPS) during sludge dewatering is one of the main challenges in sludge treatment process. The aim of this study was to investigate the EPS quantity changes within sludge dewatering by continues ultrasonic – electrocoagulation (US – EC) reactor under different conditions and to determine the most efficient case for reducing these substances. Materials and Methods: In this study, the EPS quantity changes in supernatant were compared after undergoing different conditions of ultrasonic (frequency of 35 and 130 KHz, detention time of 3,5,10, and 30 min) and electrocoagulation (voltage of 20, 30, and 40 V, detention time of 10, 20, and 30 min) processes were compared. Results: The research found that the maximum efficiency of the US-EC reactor was achieved at a frequency of 35 KHz and detention time of 5 min for ultrasonic with voltage of 40 V and at detention time of 30 min for electrocoagulation process as under these conditions total EPS concentration reduced by 69%. Conclusion: According to the results achieved, US – EC reactor significantly reduced the released EPS in supernatant in addition to dewatering sludge.

Background and Objective: Phenol and phenol derivatives in industrial wastewater are among the pollutants with priorities. The high cost and low efficiency of some routine treatment processes of industrial wastewater has limited their use. One of the new methods under consideration is, nowadays, adsorption using carbon nanotubes. This study was conducted in order to evaluate the application of alumina-coated multiwall carbon nanotubes in eliminating phenol from synthetic wastewater. Materials and Methods: This study was performed in laboratory at batch scale. Multi-wall carbon nanotubes were coated with Alumina. The concentration of phenol was determined by spectrophotometer through photometry. The effect of pH changes, dosage of adsorbent, contact time, the initial concentration of phenol, temperature, and the concentrations of different salts on the efficiency of absorption was evaluated. Then, the absorption results were described using the Langmuir and Freundlich isotherms and the synthetics of absorption. Results: It was found that absorption efficiency increased significantly by decreasing the initial concentration of phenol and pH and by increasing the carbon nanotube dosage, temperature, and contact time. On the other hand, the maximum elimination of phenol from the solution (98.86%) occurred at 4 mg/l phenol concentration, under acidic conditions (pH=3), at adsorbent dosage of 0.05 g/l, at temperature of 45°C, and contact time of 10 min. Evaluation of the regressions isotherms showed that the process follows the Langmuir model and second-degree synthetic absorption. Conclusion: The high efficacy (98%) of the adsorption process in this study showed that alumina-coated multiwall carbon nanotubes have a good capability in eliminating phenol and can be used as an appropriate and new method for eliminating phenol and its derivatives from wastewater.

Background and Objectives: Rapid growing of Triton X-100 application in industries results in its appearance in effluents  and threaten the aqueous ecosystems. Triton X-100 is not biodegradable and can accumulate in food chain.

Materials and Methods: In this study, sorption capacity of six synthesized zeolites with different regular porous structure was studied for triton X-100 (TX-100) surfactant and the results were compared with Clinoptilolite natural zeolite of Damavand region.

Results: Within all zeolite studied, Beta(200) showed the highest sorption capacity (about 575 mg/g), which is due to its regular pore structure with large pore diameter, channel intersections, high SiO₂/Al₂O₃ ratio and high surface area. Langmuir monolayer isotherm and pseudo-second-order kinetic equation could provide well-fitted to the experimental data in simulating adsorption behavior of TX-100 over Beta(200) zeolite.

Conclusion: The adsorption feature was internal sorption and the intraparticle diffusion might be a rate-limiting control for Beta(200) zeolite. Results of experiments demonstrated that the hydrophobic zeolites with large pore diameter such as Beta(200) could be effective sorbents for industrial wastewater treatment features.

Background and Objectives: Phenol is one of the industrial pollutants in wastewaters, which due to its toxicity for biological systems various pretreatment processes have been used for its detoxification. In this study, the combination of catalytic ozonation process (COP) and sequencing batch reactor (SBR) were used for detoxification of these types of wastewaters.

Materials and Methodology: In this study, the effect of COP on phenol degradation, COD removal, and detoxification of wastewater was investigated. To determine the acute toxicity of effluents and identification of intermediate compounds produced in COP, bioassay using Daphnia Magna and GC / MS were used, respectively. Then, phenol and COD removal of pretreated wastewater was investigated in SBR.

Results: It was found that under optimal conditions in COP (time = 60 min), the concentrations of phenol and COD reduced from 500 and 1162 to 7.5 and 351 mg/L respectively and pretreated effluent toxicity (TU = 36), after rising in the initial stage of reaction, effectively reduced at the end of process (TU=2.3). the integration of this process with SBR could decreased the COD and phenol concentration less than the detectable range by HPLC. 

Conclusion: Results showed that COP has a high effect on biodegradability, detoxification, and mineralization of phenol and combination of COP with SBR process can effectively treat wastewaters containing phenol.

Background and Objectives: Furfural is one of the toxic chemical compounds used in many industries such as petrochemical, food, paper products, pharmaceutical, etc., due to having some characteristics. Therefore, furfural could be found at different concentrations in the effluent from these industries and can enter the environment. Hence, the aim of this study was the assessment the efficiency of a low cost bentonite modified with cationic surfactant in the removal of furfural from aqueous solution.

Material and Methods: In this experimental study, bentonite was purchased from one of the Mines of Zanjan Province, Iran and then the efficiency of bentonite modified with the cationic surfactant CTAB (CTAB-Bent) was assessed in the adsorption of furfural from aqueous solution. Activated carbon (AC) was also purchased as commercial grade.

Results: Under optimum conditions, the removal efficiency of AC and CTAB-Bent was about 52 and 66%, respectively. For both adsorbents used in this study, the increase of contact time and sorbent dosage resulted in increasing the removal efficiency, but the removal efficiency was decreased with the increase of furfural initial concentrations. Regarding pH, the removal efficiency was the highest in relative acidic and neutral environment, (60 and 69% for AC and CTAB-Bent respectively). The kinetics studies revealed that the highest correlation coefficients were obtained for the pseudo-second order rate kinetic model. Adsorption data from both adsorbents was also fitted with Langmuir isotherm.  

Conclusion: It was found that modified bentonite with CTAB as a natural adsorbent could have better efficiencies compared with activated carbon in the furfural removal, although more contact times is needed.

Background and Objectives: In this work, biosorption of hexavalent chromium from aqueous solution with excess municipal sludge was studied. Moreover, the performance of neural networks to predict the biosorption rate was investigated.

Materials and Methods: The effect of operational parameters including initial metal concentration, initial pH, agitation speed, adsorbent dosage, and agitation time on the biosorption of chromium was assessed in a batch system. A part of the experimental results was modeled using Feed-Forward Back propagation Neural Network (FFBP-ANN). Another part of the test results was simulated to assess the model accuracy. Transfer function in the hidden layers and output layers and the number of neurons in the hidden layers were optimized.

Results: The maximum removal of chromium obtained from batch studies was more than 96% in 90 mg/L initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/L. Maximum biosorption capacity was 41.69 mg/g. Biosorption data of Cr(VI) are described well by Freundlich isotherm model and adsorption kinetic followed pseudo-second order model.  Tangent sigmoid function determined was the most appropriate transfer function in the hidden and output layer. The optimal number of neurons in hidden layers was 13. Predictions of model showed excellent correlation (R=0.984) with the target vector. Simulations performed by the developed neural network model showed good agreement with experimental results.

Conclusion: Overall, it can be concluded that excess municipal sludge performs well for the removal of Cr ions from aqueous solution as a biological and low cost biosorbent. FFBP-ANN is an appropriate technique for modeling, estimating, and prediction of biosorption process If the Levenberg-Marquardt training function, tangent sigmoid transfer function in the hidden and output layers and the number of neurons is between 1.6 to 1.8 times the input data, proper predication results could be achieved.

Background and Objectives: Phenol is a toxic and persistent substance in the environment. The aim of this study was to evaluate the performance of silica aerogel synthesized using sodium silicate in the adsorption of phenol from aqueous solutions.

Material and Method: Silica aerogel was prepared by Sol-Gel process. The influence of effective variables such contact time, initial pH of the solution, adsorbent dose, and initial phenol concentration on the adsorption efficiency was investigated. The characterization of prepared silica aerogel and confirmation of phenol adsorption was determined through SEM, XRD analysis and NMR, FTIR spectra respectively. The adsorption data was evaluated via Langmuir and Freundlich isotherms and pseudo-first and pseudo-second-order kinetics.

Results: This research found that the phenol adsorption efficiency increased by increasing pH from 3 to 11, so that after 60 min, the absorption efficiency at the 100 mg/L initial phenol concentration and 0.5 g adsorbent obtained 84 and 96.4 % at pH 3 and 11, respectively. The SEM image and XRD patternof synthesized silica aerogel confirmed the creation of porous and amorphous structure. After the phenol absorption, the NMR and FTIR spectra of silica aerogel, confirmed the creation of new bands because of phenol molecule at the adsorbent structure. The absorption of phenol was compatible with Freundlich isotherm and pseudo-second-order kinetic. The maximum absorption capacity (q_m) obtained was 47.39 mg/g.

Conclusion: Silica aerogel as an adsorbent, due to special characteristics in the structure and usage, can be a promising treatment process for adsorption of toxic and persistent substances.

Background and Objectives: In order to optimize wastewater nitrogen removal and to reduce the problems of entering nutrients in final receptors, for example, a lake, partial nitrification, as a novel nitrogen removal method, was studied.

Materials and Methods: The efficiency of simultaneous nitrification and denitrification (SND) in partial nitrification through nitrification/denitrification in fixed-film reactor was surveyed. In this process, ammonium was converted to nitrite by ammonium oxidizing bacteria (AOB) but the activity of nitrite oxidizing bacteria (NOB) was limited at low dissolved oxygen (DO) level. The inflection points of oxidation-reduction potential (ORP) profile were used as the indicators of process optimization.

Results: This research showed that in period 2 at fixed DO level of 0.5 mg/L, nitrite accumulation rate (NAR) was higher than period 1 in which DO was declined from 1 to 0.5 mg/L. In contrast to period 1, SND efficiency was reduced in period 2. In period 3, by increment of the carbon to nitrogen ratio (C/N) to 12.5, NAR increased to 71.4 % and SND efficiency increased to 96.7%. In the long term analysis of proposed method, SND efficiency was, at least, 90%.   

Conclusion: Proper C/N ratio and minimum DO level resulted in higher nitrogen removal efficiencies than the operation in which DO was decreased during aerobic phase. By using a fixed-film reactor and without considering an anoxic step, at DO level of 0.5 mg/L, maximum SND efficiency and maximum NAR would be achieved. 

Background and Objectives: Qualitative evaluation of sewage sludge before any kind of application is essential. The present study was aimed to investigate Total coliform, Fecal coliform and Salmonella in sewage sludge produced at wastewater treatment plants in Azerbaijan Province, Iran.

Materials and Methods: Nine wastewater treatment plants were chosen in East Azerbaijan Province, and their sludge from drying bed was studied. Total coliforms, thermo-tolerant coliforms, and Salmonella spp., were surveyed during winter time, 2015. Total and thermos-tolerant coliforms were enumerated by EPA method 1680 and salmonella was counted using EPA method 1682.  

Results: In the case of total coliform, sludge sample from Jolfa with 1.82×10⁶ MPN/g showed the highest contamination, while Sarab showed lowest fecal coliform count with 2.02×10³ MPN/g. As in the case for fecal coliform, the bacteria count for thermo-tolerant coliforms was higher in Jolfa than other cities; on the other hand, Ahar with no fecal coliform count or less than 2.2 showed the minimum contamination rate to fecal coliforms. In case of Salmonella spp., sludge samples from Ahar and Bostan Abad did not show any salmonella. While sludge sample from Tabriz wastewater treatment plant was determined as the most contaminant sludge with bacteria count equal to 84 per  g. Moreover, sludge sample from Sarab wastewater treatment plant showed the least contamination rate, and bacteria count was 6 per  g.

Conclusion: From the stand point of microbial quality, all sludge samples met class B standards set by USEPA, while none of them could provide class A standards. Thus, special precautions must be taken in case of soil amendments by the sludge produced from wastewater treatment plants. 

Background and Objectives: Conventional methods of leachate treatment are inefficient due to high pollution loads and characteristics of the leachate. In recent years, an integrated method has been developed considerably. The aim of this research was to evaluate the effect of powdered activated carbon on the treatment of landfill leachate of Kermanshah City by a columnar aerobic sequencing batch reactor.

Materials and Methods: This study was carried out in three reactors having a total volume of 2000 mL and each having an effective volume of 600 mL in the bench scale. To the reactors 2 and 3 that were similar from environmental conditions and operation point of view with reactor 1 (with no carbon powder), 5 and 10 g/L of PAC were added, respectively. The effects of different doses of PAC (0, 5, 10 g/L) and hydraulic detention times (HRT = 48, 96, 144 h) were investigated in order to remove the Chemical Oxygen Demand (COD) and ammonia nitrogen (NH₃-N) from the leachate. The efficiency was investigated using two -way ANOVA test in SPSS software (Ver. 16).

Results: The results of two-way ANOVA showed that there was a significant difference (P-value=0.001) between the removal efficiency of COD and NH₃–N at different HRTs with different doses of PAC. The highest removal efficiency achieved at HRT=144 h for COD and NH₃-N was in Reactor 1 were 50.11 ± 4.42 and 19.85 ± 1.49%; in reactor 2: 55.67 ± 1.6 and 25.7 ± 0.89%; and in reactor 3: 58.02 ± 3.99and 25.48 ± 1.7%, respectively.

Conclusion: It can be concluded that the combination of biological - activated carbon compared with the biological process, can remove COD and NH₃–N of strong sewages such as landfill leachate, although achieving standard treatments using this method is not possible.

Background and Objectives: Bioaugmentation is a superior technique in bioremediation of contaminated soils with petroleum hydrocarbons. The aim of this study was to evaluate the effect of isolated bacteria from activated sludge of Asalouyeh special zone municipal wastewater treatment for bioaugmentation of kerosene-contaminated soils and to study the growth of isolated bacteria in the presence of different concentrations of this product.

Materials and Methods: Sampling of activated sludge was carried out from two treatment plants in Asalouyeh zone. Isolation of degrading bacteria was performed by culturing the samples on basal mineral medium. Emulsification test and evaluating the kinetic growth of bacteria were carried out in different concentrations of kerosene. Isolated bacteria were inoculated to polluted soils with kerosene oil compound for bioaugmentation and measuring their bioremediation potentials and the rate of biodegradation were measured by InfraRed (IR) spectroscopy.

Results: In this study, three bacterias: Pseudomonas putida, Serratia marcescens, and Proteus mirabilis were isolated and identified as kerosene degrading bacterias from activated sludge. P. putida was recognized as the most powerful degrading bacterium of this oil product according to the emulsification tests, measuring the growth of bacteria in various concentrations of kerosene, the results of bioaugmentation of contaminated column of soil with kerosene, and reducing the level of Total Petroleum Hydrocarbons (TPHs). This bacterium with emulsification rate of 3.8 could reduce 71.03% of TPHs within 30 days.   

Conclusion: According to the adaption of Pseudomonas putida, Serratia marcescens, and Proteus mirabilis in activated sludge with variety of pollutants in sewage, they can be used as non-indigenous bacteria for bioaugmentation and cleaning up the soil contaminated petroleum hydrocarbons.

Background and Objective: Surfactants can be found in soaps, detergents, pharmaceutical products, personal care products, as well as in leather industries. In this study, adsorption of Sodium Dodecyl Sulfate (SDS) on magnetic multi-walled carbon nanotubes in the aqueous solutions was investigated.

Materials and methods: Surfactant concentration, adsorbent dosage, and pH values were considered as variables. Residual surfactant was measured using methylene blue method and adsorbent characteristic was determined by X-Ray diffraction and Fourier transform infrared spectroscopic analysis. Adsorption capacity, adsorption isotherm, and kinetic reaction were also investigated.

Results: Adsorption investigations demonstrated that the increase in initial SDS concentration or pH values, led to the decrease in SDS adsorption. Conversely, the same result was achieved by decreasing adsorbent dosage. After 120 min SDS adsorption became stable. By increasing in SDS concentration from 15 to 150 mg/L, adsorption capacity improved from 8 to 61 mg/g. Isotherm and kinetic data demonstrated that experimental data pursued Langmuir isotherm (R²=0.993) and pseudo-second order equation (R²=0.992).

Conclusion: Magnetic multiwall carbon nanotubes can be used as an effective and useful sorbent for SDS removal due to several advantages including: high adsorption capacity, relatively low equilibrium time, and easy separation of magnetic multiwall carbon nanotubes from aqueous solutions.

Background and Objective: Being low cost of building and operation, anaerobic baffled reactor is considered superior to aerobic methods of wastewater treatment, especially for small communities. However, it needs to be studded for upgrade and overcome of its limitations. The purpose of this study was to evaluate the performance of FABR and RABR reactors for the municipal wastewater treatment at laboratory scale and in field conditions to determine their optimum conditions in reaching effluent discharge standards.

Materials and Methods: This study was conducted in Khoy wastewater treatment plant. FABR was operated for 267 days with hydraulic retention time of 18-48 h and RABR was operated for 90 days with media bad rotation of 10-50 rpm. The reactors were fed in line from the wastewater canal. Using composite sampling, 224 samples were taken from the inflow and outflow of the reactors and each sample was analyzed for parameters of COD, BOD, TSS, VSS, TKN, and TP.

Results: The reactor startup took about 107 days. FABR removal efficiency was 93-80, 21-10, and 30-21% for COD, TKN, and PO₄ respectively at HRT of 48-18 h. FABR reached effluent disposal standard of TSS, COD, and BOD in all conditions and optimum HRT of 36 h. RABR reached to these standards at HRT 24 h and 50 rpm. However, none of them could meet the nutrient effluent standards.

Conclusion: FABR is an appropriate system for municipal wastewater treatment but for reaching N and P effluent standard, it should be combined with aerobic post-treatment. Moreover, in order to reuse the reactor's nutrient-rich effluent for irrigation; it can be reused as subsurface irrigation.

Improper and incorrect implementation of sewage collection networks can cause environmental and health problems. It also causes dissatisfaction in urban residents. The purpose of this study was to design a questionnaire for evaluating satisfaction level of urban residents from sewage collection network. Face validity index, content validity ratio and Cronbach-coefficient were used to evaluate validity and internal consistency. The evaluated indexes were assessed in acceptable levels. The designed tool that was included 25 variables can be used to assess satisfaction level by researchers and wastewater companies.