Showing 9 results for Nox
M Ahmadi, H Ganjidoust, B Ayati,
Volume 1, Issue 2 (3-2009)
Abstract
Background and Objectives: Upflow Sludge Blanket Filtration (USBF) system is a modification of the conventional activated sludge process that incorporates an anoxic zone with an upflow sludge blanket filtration clarifier in one bioreactor. It has no inherent capacity limits and is used in a wide range of applications in municipal, industrial and agricultural wastewater treatment. The main objective of this study was to evaluate the performance of a continuous USBF reactor for the treatment of sugar industrial wastewater.
Materials and Methods: Sixty liter laboratory pilot scale plant was made of plexiglass consists of 14 liter anoxic zone, 38 liter aerobic zone and 8 liter clarifier. Used molasses for raw wastewater was obtained from Varamin Sugar Company. During the study, the wastewater has been initially fed to anoxic zone of the bioreactor. It mixed with recycled activated sludge returned from the clarifier and the mixed liquor entered into aerobic zone of the bioreactor. From aeration zone, the mixed liquor passed through the sludge zone at the bottom of the clarifier which was then separated by upflow sludge blanket filtration and then the clear water discharged from the system. To complete the internal circulation loop, collected activated sludge at the bottom of the clarifier was recycled to the anoxic zone.
Results: Experimental studies indicated that average removal efficiency of COD with HRTs from 21 to 26 hours in the aerobic zone and from 8 to 10 hours in the anoxic zone were from 77 to 97 percent depended on input feed (1000 to 30000 mg/L).
Conclusion: USBF as an advanced biological process had a proper COD removal efficiency for the biological treatment of sugar industries wastewater compared to other researchers methods.
M Aghanejad, A.r Mesdaginia, F Vaezi,
Volume 2, Issue 1 (7-2009)
Abstract
Backgrounds and Objectives: Now a days modified activated sludge ways are used for standard removing nutrient substances from waste water that is named Enhanced biological phosphorus removal One of the most suitable ways is Anoxic-Oxic(A/O) process. The goal of this research is investigation and solving existing problems of Khoy power plant(P.P) waste water treatment plant(WWTP)and optimizing of phosphorus removal in it.
Materials and Methods: This research is done full scale in this treatment plant. The treatment plant was operating with extended aeration process, and some problems had, so in the first stage with in investigation of total efficiency, problems and their reasons determined. In the second stage after operational modifications existing problems was solved and real efficiency of treatment plant particularly for phosphorus(P) removal determined. In the third stage changes, system converted to A/O process and new system was tested with Changing parameters like food/microorganism(F/M), return sludge ratio(RAS)and sludge retention time(SRT)
Risults: In the first stage the most important problems were over concentration of BOD,TSS, and P in effluent of treatment plant and overgrows of alga observed in parts of treatment plant and effluent receiving conduit. The main reason of high concentration of P was considered releasing of sludge. In the second stage operating condition modification efficiency of P removal increased from 50to 62 percent. In the end of third stage value of P removal reached to %82 and the most suitable of anoxic contact time was determined 3to4 hours, SRT terry day and F/M ratio o.12,that the most effective change has been the decrease of SRT to three days.
Conclusion: Adjusting of operating factors like SRT,RAS, sludge processing way in WWTP can increase P removal in them with in total efficiency remaining, such as in this case it was %12. In waste water treatment particularly for P removal the A/O process is suitable so in this project its effect on P removal efficiency has been %20.
Mohammad Esmaeilzadeh, Edris Bazrafshan, Mahnaz Nasrabadi,
Volume 6, Issue 1 (5-2013)
Abstract
Background and Objectives: Tous gas power plant as an emission source of gas pollutants is located in the northwest of Mashhad City. This power plant is located in the neighborhood of various (linear, point and area) sources of pollution including Tous thermal power plant, Tous industrial town and motor vehicles hence, it is not possible to determine precisely and accurately the share of these gases emission contribution at this power plant using conventional instruments. Therefore, we used modeling in order to estimate the dispersion of the pollutants emitted from this power plant.
Materials and Methods: we used Screen 3 software using data of exhaust fume concentration, mass emission, chimney features of each unit, meteorology data, and fuel types consumed in order to model dispersion of NOx and SO2 emitted from Tous gas power plant having V94.2 turbine equipped with DLN torches.
Results: Maximum concentration of NOx and SO2 at the distance about 30 km from the power plant was 1.08 and 3.69 µg/L respectively. The results of dispersion modeling of pollutants indicated that in most cases emission of air pollutants towards southeast. Conclusion: The NOx and SO2 concentration measured revealed that the concentration of these pollutants is lower than the standards of Clean Air Act.
Roohollah Noori, Gholamali Hoshyaripour, Khosro Ashrafi, Omran Rasti,
Volume 6, Issue 1 (5-2013)
Abstract
Backgrounds and Objectives: Precise air pollutants prediction, as the first step in facing air pollution problem, could provide helpful information for authorities in order to have appropriate actions toward this challenge. Regarding the importance of carbon monoxide (CO) in Tehran atmosphere, this study aims to introduce a suitable model for predicting this pollutant.
Materials and Method: We used the air pollutants and meteorological data of Gholhak station located in the north of Tehran these data provided 12 variables as inputs for predicting the average CO concentration of the next day. First, support vector machine (SVM) model was used for forecasting CO daily average concentration. Then, we reduced the SVM inputs to seven variables using forward selection (FS) method. Finally, the hybrid model, FS-SVM, was developed for CO daily average concentration forecasting.
Result: In the research, we used correlation coefficient to evaluate the accuracy of both SVM and FS-SVM models. Findings indicated that correlation coefficient for both models in testing step was equal (R~0.88). It means that both models have proper accuracy for predicting CO concentration. However, it is noteworthy that FS-SVM model charged fewer amounts of computational and economical costs due to fewer inputs than SVM model.
Conclusion: Results showed that although both models have relatively equal accuracy in predicting CO concentration, FS-SVM model is the superior model due to its less number of inputs and therefore, less computational burden.
Kh Ashrafi, M Shafie Pour Motlagh, M.s Mousavi, M.h Niksokhan, H.r Vosoughifar,
Volume 8, Issue 4 (3-2016)
Abstract
Background and Objectives: In this study, contribution of exhaust emission and CO distribution was estimated in enclosed residential complex parking.
Materials and Methods: This was a descriptive - analytical study consisted of two stages. In the first stage, the emission contribution of vehicles was determined. In order to determine the contribution of exhaust gas emissions, through gas species, only four species CO, O2, CO2, and N2 were measured. Concentration of CO, O2, and CO2 was estimated using data obtained from the vehicle emissions monitoring system. The amount of N2 was estimated from sum ratio of all species, which equals to 1. Then, using computational methods, the amount of the emission contribution from vehicles. In the second phase, to measure the distribution of CO pollutant, gas sampling and collecting was performed using sampling bags made of inert materials with a volume of 10 l at six points. Sampling was conducted in accordance with the requirements of OSHA ID 210. The Obtained data were analyzed using SPSS Ver.16 software and Pearson statistical test (P > 0.05 means there was no significant difference).
Results: Maximum contribution was estimated for Pride with amount of 44.4 g/s and minimum contribution was estimated for Tiba with amount of 0.3 g/s. The minimum and maximum distribution value of CO concentration was achieved 3.6 and 69.48 ppm respectively. It was found that no significant relationship was observed between the values of exhaust emissions and CO distribution. However, the distribution of concentration was associated with locations and the number of openings, the number and type of vehicle, time of operation of the vehicle, the vehicle performance, and environmental factors.
Conclusion: Measuring vehicles CO emission indicated that the concentration was beyond the permissible level recommended by the World Health Organization at some. Moreover, it was indicated that natural air conditioning is an effective alternative for improving the air quality in built environments and suitable quality in built environments is achievable through reasonable architectural design, without need to spend too much expense.
M Kalhor, S Ghaleh Askari, M Bozorgi,
Volume 11, Issue 3 (12-2018)
Abstract
Background and Objective: Concentration prediction with Gaussian dispersion models is highly sensitive to meteorological data. The lack of sounding data station in developing countries may lead to large error and uncertainty in air pollution modeling results. In this paper, the effects of estimated upper air data on the model output concentration values were investigated.
Materials and Methods: AERMOD model was executed once with real upper air data and also with estimated upper air data separately. T-Student and LEVENE tests were used to evaluate the significant differences between concentrations in two modes of using actual and estimated upper air data.
Results: The results showed that large differences in concentration between the two methods. In long term modeling, there was up to 33% differences between real and estimated upper meteorological data and up to 63% differences for short term modeling. A large difference was also observed between boundary layer parameterization values in each case. The statistical analysis showed a meaningful difference (p=0.00) between the cases. The differences between ZICNV, DT/DZ, W* were 7.1%, 48%, and 19%, respectively.
Conclusion: The use of estimated upper meteorological data in comparison with measured data may lead to a large error. The AERMOD modeling results with estimated meteorological data must be expressed with appropriate uncertainties and confidence interval.
A Ahmadi Orkomi, A Kamkar, Z Aghajani,
Volume 12, Issue 2 (9-2019)
Abstract
Background and Objective: Since mobile resources are the most important sources of air pollution in the metropolis of Rasht and due to the importance of air pollution in wet weather condition in Rasht, this research was carried out in a specific area to determine the pattern governing the change in the monthly emissions of pollutants on a small scale, using the results obtained from that area.
Materials and Methods: In this study, the amount of air pollutants was estimated on a small scale by continuous monitoring of traffic throughout the year (four days per month and six hours per day) and using MOVES software.
Results: The maximum annual average emissions of CO and NOx in the study area were 15.76 (between Gas and Razi squares) and 2 (between Imam Hossein Square and Nirou Daryaee square) g/(m.hr), respectively. In addition, the results showed that the average monthly emission of NOX throughout the year in each of the sections was constant and the average monthly emission of CO in the first half and the second half of the year was constant, and its value in the first half was higher than that in the second half.
Conclusion: Hourly distribution of CO emission in different months was affected by events and, in general, the pattern of people's life styles. But the hourly distribution for NOX was roughly constant throughout the year. Also, according to the results, with a single measurement (for CO) and twice measurement (for NOX) of traffic instead of monthly measurements, the pollutant emission estimation in other parts of the city was possible with an acceptable accuracy. Because the generalization of the method used in this study to estimate the emission of pollutants in all roads of the city is not reasonable and cost-effective.
R Dehghan, S Abdolahi, M Rahimi, F Nejad Koorki, M Amini,
Volume 12, Issue 3 (12-2019)
Abstract
Background and Objective: Due to the increasing growth of urbanization, vehicles are one of the most important environmental causes of air pollution in today's world.. With the increasing problems of air pollution and its environmental consequences due to lack of compliance with standards in manufacturing cars and their fuel consumption, awareness of the exhaust of cars and its comparison with environmental protection standards and technical examination is essential for controlling and reducing air pollution. Therefore, the present study was carried out with the aim of studying and comparing the amount of CO, CO2 and HC emissions from light vehicle exhausts in the period of 1383-1389 based on technical and environmental inspection standards in Shiraz. Also, the relationship between the year of construction of the car and the amount of output of these pollutants was discussed.
Materials and Methods: In this research, the amount of exhaust emissions (carbon monoxide, carbon dioxide and uncured hydrocarbons) from the exhaust of 858 vehicles included models Peugeot 206, GLX and Pars that were referred to the technical examination center during 5 months in Shiraz between the years 1383-1389 was investigated. Also, the relationship between the year of production and the amount of output of these pollutants was studied. Data analysis was done using SPSS software and Microsoft Excel software was used for drawing graphs.
Results: The results showed that there was a significant and negative correlation between the year of manufacture of the vehicle and the reduction of CO and HC. As the year of construction increases, the amount of pollutants is decreasing. Also, this relationship was positive and significant between the year of manufacture and CO2. Also, the exhaust pollutants (CO and CO2) from the Peugeot GLX exhaust system were lower than Peugeot Pars and 206, and the lowest amount of HC was observed in Peugeot 206.
Conclusion: In general, the exhaust emissions of all three cars were at the standard Euro 2 and technical examination.
Alireza Hajighasemkhan, Lobat Taghavi, Elham Moniri, Amir Hessam Hassani, Homayon Ahmad Panahi,
Volume 13, Issue 1 (4-2020)
Abstract
Background and Objective: Increased use of pesticides and chemical fertilizers in agriculture in order to increase the productivity of fertile lands has led to pollution of water resources with a variety of pollutants, including herbicides. In this study, a new polymer magnetic nanoadsorbent named PV/S-g-3D-GO/N was synthesized and used to remove 2,4-D and MCPA herbicides from aquatic environment.
Materials and Methods: To investigate the synthesized nanoadsorbent structure FTIR, FESEM, TEM, XRD, VSM and TGA techniques were used and the effect of parameters affecting the optimal removal of herbicides by the adsorbent, including pH, temperature, contact time, adsorption dose and initial herbicide concentration was investigated. The kinetic, isotherm and thermodynamic studies of adsorption were also investigated.
Results: The results showed that in the optimal adsorption conditions including pH 3 for both herbicides, contact time of 180 min for 2.4-D herbicide and 300 min for MCPA herbicide, absorption dose 5 g/L and temperature 50°C for both herbicides, the maximum absorption capacity (qmax) was 5.62 mg/g for 2.4-D and 4.94 mg/g for MCPA. The synthesized nanoparticles that were used to remove 2,4-D and MCPA herbicides from real samples were totally successful (100% removal efficiency). For both herbicides studied, the isothermal data followed the Longmuir model (2,4-D: R2 = 0.995; MCPA: R2 = 0.998), and the kinetics of the adsorption process was a pseudo-second-order model (2,4-D: R2 = 0.991; MCPA: R2 = 0.999).
Conclusion: The results of the present study indicate that the synthesized nano-adsorbent can be used to remove phenoxic herbicides from agricultural runoff as well as water sources contaminated with the studied herbicides.
