h. ganjidoust
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در پژوهش حاضر، پارامترهای وابسته به الکترود و موثر در عملکرد سیستم انعقاد و شناورسازی الکتریکی، شامل: سطح الکترود، فاصله ی الکترود، نوع الکترود و شکل آن بررسی و تاثیر هر یک در بازده حذف رنگزای اسید قرمز 14 از فاضلاب سنتزی، مصرف انرژی، انحلال آند و نیز T S S لجن، تعیین و مقادیر هر یک بهینه شد. سطح الکترود برابر $20.5\،c m^{2}$، فاصله ی بین الکترود $0.5\،c m$، نوع الکترود فولادی زنگ نزن و شکل الکترود مشبک)مش بندی شده(به عنوان بهینه انتخاب شدند. تحت شرایط بهینه و در مدت زمان حدود 20 دقیقه، بازده حذف کامل رنگزا با میزان مصرف انرژی مخصوص $\r m{6.2\،k W h/k g _{d y e\،r e m o v e d}}$، آند مصرفی k g $\r m{4.4\،F e/k g_{d y e\،r e m o v e d}}$ و T S S لجن m g/L17000 حاصل شد. با توجه به مزایای روش هم زمان انعقاد و شناورسازی الکتریکی، از قبیل: امکان بهره برداری کاملا خودکار و کنترل آسان پارامترهای دخیل در فرایند و با توجه به اهمیت کاهش هزینه ها با استفاده از سیستم های با مصرف مواد و انرژی و میزان T S S کمتر، استفاده از روش مذکور برای تصفیه ی فاضلاب های صنعتی حاوی مواد رنگزا پیشنهاد می شود.
کلید واژگان: انعقاد و شناورسازی الکتریکی، حذف رنگزا، مصرف انرژی، انحلال آند، سطح الکترود، فاصله ی الکترودDue to the potential contamination of groundwater and surface water in the vicinity of the consumer dye industry, removal of this dyestuff waste is an environmental priority. Water clarity and solubility of gases in the presence of even a small amount of dye is reduced. If there are colored substances toxic to lower layers light penetration in the water is low. In addition, photosynthesis of aquatic plants and the amount of dissolved oxygen is so low that aquatic animals are destroyed. Dyes are stable compounds that are not easily biodegradable, and azo dyes are considered especially carcinogenic. Dye removal via various methods of physical, chemical, biological or a combination of them is possible that can be noted on physical methods such as adsorption, membrane filtration and ultrasonic waves, chemical methods, such as ion exchange, electrolysis, coagulation and flocculation, canonical and advanced oxidation, and biological methods, using algae, fungi and bacteria.Chemical coagulation is a common method of wastewater containing dye. High levels of dissolved solids and sludge in purified effluent are the disadvantages of chemical coagulation. In recent years, because of the versatility and compatibility with the environment, the electrochemical method as an effective method for treating wastewater of containing dye industries is taken into consideration. In the electric coagulation, production happens in the place of coagulant materials that are the result of dissolution metal anode (steel) by passing an electric current.If we put sewage between the positive anode and negative cathode that are plugged to electricity, an electric field is established because of the electrical conductivity of the solution. By electrolysis of water, tiny bubbles of oxygen and hydrogen are produced and they move upwards and form a blanket on the surface. Bubbles bring suspended particles to the surface and form a sludge layer that is mechanically collected.Expected use of electric flotation process simultaneously with electric coagulation eliminates the requirement of gravity sedimentation unit for the separation of the clots, resulting in the separation of both emissions and reducing the cost of the filtration.Studies in the field of electrochemical dye degradation based on electric coagulation and flotation property of the produced bubble are rarely used. In this study, reactors designed in a manner intended to electric coagulation properties and electric flotation can be used simultaneously. In addition, this study is a used innovation, such as the use of grille stainless steel electrodes with horizontal arrangement.In this research, the electrode-related parameters affecting the performance of the electric coagulation and flotation system, including the surface, distance, type, and shape of electrodes, were investigated. In addition, the influences of each of these parameters on the removal efficiency of Acid Red 14 from synthetic wastewater, energy and the anode consumption were determined and their values were optimized.The surface of electrode equal to 20.5 cm2, the distance between the electrodes equal to 0.5 cm, and stainless steel as type of electrode and a grid shape electrode (mesh generator) were chosen as optimized.Under optimal conditions in about 20 minutes, 100% dye removal efficiency with special energy consumption equal to 6.2 kWh/kg was obtained. Dye removal with the anode consumption equal to 4.4 kg Fe/kg and sludge TSS 17000 mg/L was also obtained.According to electric coagulation and flotation benefits such as the ability to fully automatic exploit, easy control of parameters involved in the process, safe operation conditions and very high tolerance to organic, hydro and toxins shocks and considering the importance of reducing the cost using systems with less material and energy and TSS consumption, use of this method for filtrating or pre- filtrating is suggested prior to supplementary filtration of industrial wastewater containing dye. The advantages of this method compared to other methods of dye removal are as follows: simple equipment, high speed and short retention time to remove pollutants, easy navigation, and low amount of chemicals, and low produced sludge which has high sedimentation or floating rate with low amount of water.
Keywords: Electro-Coagulation-Otation, Dyeremoval, Energy Consumption, Anode Dissolution, Electrode Surface, Electrode Distance -
در پژوهش حاضر، تصفیه ی خاک آلوده به نفت خام)آلودگی اولیه ی m g/K g 6000(با استفاده از روش الکتروکینتیک بهبودیافته با سورفکتنت های S D S و S a p o n i n در مقیاس آزمایشگاهی بررسی شده است. آزمایش ها در سلول الکتروکینتیک از جنس پلکسی گلاس به ابعاد c m $30\t i m e s6\t i m e s5$ در مدت 7 روز انجام شده اند. در پژوهش حاضر، اثر غلظت سورفکتنت)غلظت S D S برابر با 0٫1، 0٫2 و 0٫3 و غلظت S a p o n i n برابر با 0٫05، 0٫1 و 0٫2 درصد وزنی(و ولتاژ)1 و 2 ولت بر سانتی متر(در میزان حذف نفت از خاک ارزیابی شده است. طبق نتایج حاصل، با کاربرد S a p o n i n در ولتاژ V/c m 1، بیشترین میزان حذف در غلظت بحرانی)0٫1\٪(برابر با 18٫35\٪ به دست آمده است؛ درحالی که S D S توانسته است 26٫14\٪ از نفت خام را در بیشترین غلظت سورفکتنت)0٫3\٪(حذف کند. از طرفی با افزایش ولتاژ به V/c m 2 در آزمایش های با غلظت بحرانی سورفکتنت ها، راندمان حذف حدود 4-6 درصد بهبود یافته است.
کلید واژگان: تصفیه ی خاک، آلودگی نفتی، الکتروکینتیک، سورفکتنت ها، S D S، S A P O N I NUncontrolled emission of different contaminants in environment, such as soil and groundwater, leads to increasing the contamination and causing risks for the ecosystem and human health. Over the last century, the oil has been one of the energy sources and the raw material for many industries. It must be mentioned that about 0.1% of its production enters the seas and oceans due to various events and pollutes the water and soil. Among the different methods of soil treatment, Electrokinetic is one of the most widely used methods, especially in the case of fine-grained soils. Due to low solubility of organic contaminants in water, such as oil, application of surfactants is necessary to improve the Electrokinetic method. Surfactants can increase the solubilization of organic compounds by reducing the surface tension and interfacial tension. So, the electroosmosis flow is the most important mechanism of pollutant transport. In this study, treatment of contaminated soils with crude oil, using enhanced Electrokinetic method by surfactants in pilot scale has been investigated. For this purpose, SDS and Saponin were used to remove the oil crude (6000 mg/Kg) from soil. Each test was conducted in cells made of Plexiglas with dimensions of 30*6*5 cm during 7 days. The effect of surfactant concentration (0.1, 0.2, and 0.3 wt % for SDS and 0.05, 0.1, and 0.2 wt % for Saponin) and applied voltage gradient (1 and 2 V/cm) to the oil removal from soil were investigated in the experiments. According to results, in the tests conducted with Saponin in 1 V/cm, the maximum removal rate of 18.35% was obtained in critical concentration (0.1 %), while using the SDS leads to a removal percentage equaling to 26.14 % in the highest concentration of SDS (0.3%). In addition, increasing the applied voltage gradient to 2 V/cm in the tests with critical concentration of surfactants raised the removal efficiency
Keywords: S?O?I?L T?R?E?A?T?M?E?N?T, O?I?L C?O?N?T?A?M?I?N?A?T?I?O?N, E?L?E?C?T?R?O?K?I?N?E?T?I?C M?E?T?H?O?D, S?U?R?F?A?C?T?A?N?T?S, S?D?S, S?A?P?O?N?I?N -
در این مطالعه، برای بررسی تاثیر و بهینه سازی 6 متغیر: نسبت وزنی خاکستر بادی ($X_1$)، رس اسیدی ($X_2$)، میکروسیلیس ($X_3$) به سیمان، نسبت آب به مواد جامد ($X_4$)، ولتاژ اعمالی ($X_5$)، و دوره ی تعویض قطبیت میدان الکتریکی ($X_6$) در الکتروسینتیک چرخشی در تثبیت و جامدسازی پسماند مصنوعی حاوی سرب، روی و آرسنیک از روش سطح پاسخ و طرح مرکب مرکزی استفاده شده است. بر روی 86 نمونه ی آزمایشگاهی ساخته شده، آزمایش مقاومت فشاری و تعیین p H و بر روی نمونه های با بیشینه و کمینه یمقاومت فشاری، آزمایش T C L P و عکس برداری الکترونی)S E M(انجام شده است. نتایج نشان داده است که به علت حضور گسترده ی C$_2$A H$_8$، C A H$_{10}$، کلسیم سیلیکات هیدراته، محصورشدن آرسنیک در H$_2$O7٫5N a C a A s O$_4$،، و روی و سرب در کریستال های پرتلنیت، کاهش ذرات سیمان غیرهیدراته و اترینگایت در شرایط بهینه، میزان مقاومت فشاری، p H نمونه، غلظت سرب، روی و آرسنیک در شیرابه ی T C L P، به ترتیب برابر M p a 57٫56، 9٫82، m g/L 0٫4، m g/L 0٫393 و m g/L 0٫146 بوده است.
کلید واژگان: تثبیت و جامدسازی، الکتروسینتیک چرخشی، فلزات سنگین، پسماند صنایع، T C L PIn this study, the effects of fly ash $(X_1)$, kaolinitic clay $(X_2)$, micro-silica $(X_3)$ content and water-to-solid ratio $(X_4)$, electrical potential gradient $(X_5)$ and polarity reversal period $(X_6)$ on the solidification and stabilization of Synthetic waste containing lead, zinc and arsenic were investigated. The data were analyzed using the central composite design which is the most commonly used response surface methodology RSM design (using a mixture design of a constrained triangular surface) and ANOVA. Optimum formulations were simulated using a desirability function. pH and compressive strength tests were performed on 86 specimens. The specimens with the highest and lowest compressive strengths were selected for Toxicity characteristics leaching procedure (TCLP) and scanning electron microscopy (SEM) to evaluate the leaching behavior of lead, zinc and arsenic and monitoring hydration progress, respectively. The experiments were arranged according to a full factorial design, which also allowed deriving predictive models for unconfined compressive strength and pH as affected by Synthetic waste content as well as variables type and dosage. Among the variables tested, polarity reversal period (less than 32.5min) and micro-silica (more than 7.5 % wt.) were found to affect mechanical strength far more positively compared to the other species used, at the same time ensuring low metal release from the material. On the other hand, the use of polarity reversal period more than 32.5 min and micro-silica less than 7.5% wt. were observed to cause a significant increase in metal leaching. The result indicates that the extensive accumulations of calcium aluminate hydrates (CAH) which are the main products of tri-calcium aluminate (C3A) and calcium silicate hydrate (CSH) were identified as the main hydration products. The formation of $NaCaAsO_4$.$7.5H_2O$ and portlandite were the main phase controlling $As^{5}$ and heavy metal solubility in cement-treated Synthetic wastes. The optimal conditions obtained from the compromise of the two desirable responses, pH and compressive strength of specimens, were lead, zinc and arsenic concentration in TCLP leachate 0.4 mg/L, 0.393 mg/L and 0.146 mg/L, respectively. pH and compressive strength of specimens in the optimal condition were 57.56 Mpa and 9.82, respectively.
Keywords: S?O?L?I?D?I?F?I?C?A?T?I?O?N- S?T?A?B?I?L?I?Z?A?T?I?O?N, N?O?N-U?N?I?F?O?R?M E?L?E?C?T?R?O-K?I?N?E?T?I?C, H?E?A?V?Y M?E?T?A?L?S, I?N?D?U?S?T?R?I?A?L W?A?S?T?E, T?C?L?P -
پساب پالایشگاه های نفتی شامل طیف وسیعی از آلاینده های سخت تجزیه پذیر هستند، که فرایند جذب سطحی با جاذب های ارزان و در دسترس، روشی مناسب برای تصفیه ی آنها به حساب می آید. در این پژوهش از کربن فعال تهیه شده از پوست های بادام و گردو استفاده شده و اثر عوامل p H، زمان تماس و غلظت جاذب در راندمان حذف مجموع هیدروکربن های نفتی بررسی شده است. بیشترین راندمان در 8 = p H، با غلظت کربن فعال g r/L 5 و پس از گذشت 2 ساعت از زمان تماس برابر 85\٪ به دست آمده است. داده های تعادلی جذب با مدل های ایزوترم لانگ مویر، فرندلیچ، تمکین و دوبینین رادوشکویچ مقایسه شده و بیشترین مقدار ضریب همبستگی برای مدل فرندلیچ به دست آمده است، که حاکی از ناهمگنی سطح جاذب بوده است. براساس مدل لانگ مویر، بیشینه ی ظرفیت جذب سطحی تک لایه ی کربن فعال پوست بادام و گردو به ترتیب m g/g r 83 و m g/g r 59 برآورد شده است. سینتیک جذب نیز از مدل سینتیکی شبه مرتبه ی دوم تبعیت کرده است.
کلید واژگان: T P H، لانگ مویر، فرندلیچ، تمکین، دوبینین، رادوشکویچEach year, more than 2000 million tons of wastewater is generated by oil refineries in the Middle East and European Union countries only. Oil refinery wastewater contains a wide range of toxic and non-biodegradable pollutants. Its discharge into the environment has created a major ecological problem throughout the world. An adsorption process for sewage refinery treatment would be an attractive method, if the adsorbent were inexpensive and available. In this study, activated carbon, prepared from almond shell and nut shells, are used as natural adsorbents for the treatment of petroleum refinery wastewater. The effect of pH, contact time and adsorbent concentration on TPH removal efficiency was studied. The results have shown that the effects of pH on the adsorption of petroleum hydrocarbons onto prepared activated carbon are small. It has also shown that about 90\% of adsorption occurs in the first 30 minutes of the process and is completed in 60 minutes of contact time when the adsorption reaches equilibrium condition. The experiments demonstrated that an increase in adsorbent concentration leads to adsorbent particles attaching to each other. This reduces surface area and adsorption sites, therefore, decreasing adsorption efficiency per mass unit of adsorbent. The highest TPH removal efficiency obtained was 85\% at pH=8, with a concentration of activated carbon=5 gr/L and contact time= 2 hours. Equilibrium sorption data were compared with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. The highest $R^2$ value was obtained for the Freundlich model, which indicated the heterogeneity of the adsorbent surface.Based on the Langmuir model, the maximum monolayer adsorption capacities of almond shell and nut shell activated carbon were estimated to be 83 mg/gr and 59 mg/gr, respectively. The heat of the sorption process for almond shell and nut shell activated carbon was estimated from the Temkin model to be 26.15 J/mol and 15.47 J/mole, respectively, which vividly proves that the adsorption experiment followed a physical process. Adsorption of petroleum hydrocarbons onto activated carbons was followed by pseudo-second-order reactions.
Keywords: TPH, Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Almond Shell, Nut Shell -
در این پژوهش از ازن زنی برای حذف رنگ فاضلاب حاوی اسید اورانژ 7 و از فرایند فتوکاتالیستی چسبیده معلق نانو ذرات T i O$_2$ برای تصفیه ی نهایی استفاده شده است. طبق نتایج حاصل، راندمان حذف C O D با کاهش نرخ ازن تزریقی، افزایش غلظت اولیه، افزایش p H، کاهش تعداد آکنه ها و کاهش توان منبع نوری کاهش یافت. سطوح بهینه، از روش طراحی آزمایش تاگوچی با تابع هدف کمینه ی میزان انرژی مصرفی به ازاء حذف هر واحد C O D برای متغیرهای غلظت اولیه)m g/L 50(، p H)3(، میزان ازن تزریقی)g/h r 1٫2(، غلظت نانوماده)m g/L 128(و توان منبع نور)W 120(به دست آمد. در حالت بهینه ی عملی، m g/L 50 آلاینده در p H برابر با 3 و با ازن تزریقی g/h r 1٫2 پس از 135 دقیقه بی رنگ شد. در ادامه، با استفاده از 30 آکنه)m g/L 128 نانو مواد T i O$_2$(در معرض لامپ 120 وات در مدت 4 روز، 89٪ از C O D فاضلاب حذف شد.
کلید واژگان: ازن، T I O$، 2$، فتوکاتالیست، اسید اورانژ 7، تاگوچی، رنگ بری، C O DMost dye substances are used in production processes and cause serious environmental pollution when discharged into the environment. Acid orange 7 is one of them, which has been studied in this research. Acid orange 7 containing wastewater is resistant to aerobic degradation and, under anaerobic conditions, can be reduced to potentially carcinogenic aromatic amines. Physical processes have difficulty in complete destruction of dye pollutants. Applications of both the slurry process and immobilized nano technology systems have recently been studied. Nano material agglomeration, light penetration in wastewater and the separation of nano materials from effluent are the most important disadvantages of the slurry process. The purpose of this study is to propose a new suitable treatment method. This method consists of pretreatment of dye wastewater with ozonation, undertaking the immobilized-suspended photocatalytic process as the final treatment. In the immobilized-suspended photocatalytic process, nano TiO2 were coated on submerged media. The coated media was characterized by Scanning Electron Microscopy (SEM) and Energy- Dispersive X-ray microanalysis (EDX) techniques. The result has shown that COD removal efficiency decreased with a decrease in ozone injection rate, an increase in initial concentration, an increase in pH,a decrease in the number of media (nano TiO2 concentration) and a decrease in power of the light source. An experimental design, based on the Taguchi method, was applied to assess the effects of several operating parameters, including dye concentration, TiO2 concentration, pH, light source power, and ozone injection rate, on the energy consumption of the treatment. Based on experimental design data, optimum conditions were achieved at 50 mg/L of initial dye concentration, pH of 3, ozone injection rate at 1.2 gram per hour, 128 mg/L of nano $TiO_2$ (media number equal to 30) and 120 Watt UV-A light source. Under these conditions, dye removal was completed after 135 minutes. Then, in the photocatalytic process, 89% of COD was removed over 4 days using 30 media (128 mg/L), with 120 Watt light source.
Keywords: Ozone, $Tio, 2$, Photocatalyst, Acid Orange 7, Taguchi, Dye Removal, COD -
تصفیه ی فاضلاب محتوای اکسی تتراسایکلین (O TC) به دلیل مشکلات جدی در محیط زیست اهمیت خاصی دارد. در این پژوهش، حذف کامل m g/L)155) توسط m g/L)1000) نانو ذرات آهن در p H برابر 3 با توان تابشی 200 وات در ناحیه ی U V-A در مدت 14 ساعت انجام و با بررسی تغییرات پارامترهای O R P، p H و D O در مدت 6٫5 ساعت، زمان شروع واکنش فتوکاتالیستی هیدروکسید اکسید آهن پس از 3 ساعت به دست آمد. محصولات عمده ی ناشی از شکست مولکول O T C تعیین و ثابت های سینتیکی آنها به ترتیب 0٫0099، 0٫0021، 0٫0049 و (m i n$^{-1}$)0٫0074 محاسبه شدند. اثر حضور یون های کلسیم، منیزیم، کلر، نیترات، سولفات و بی کربنات با غلظت های 10، 50، 100 و p p m)200 در فرایند بررسی شدند. با افزایش غلظت یون ها به ترتیب r m{N O_3^->C a^{2+}a p p r o x M g^{2+}>C l^-}}$ اثر منفی در حذف داشتند و یون های سولفات و بی کربنات بی اثر بودند. همچنین مدل سینتیکی و ثابت های سرعت حذف O T C در حضور یون های رقیب محاسبه شدند.
کلید واژگان: O R P، D O، P H، یون های مزاحم، سینتیک، مکانیسمA large amount of antibiotics consumed ends up in wastewater, in which they may exert selective pressure on or maintain resistance against microorganisms. Antibiotic resistant bacteria and genes encoding antibiotic resistance are commonly detected in wastewater, often at higher rates and concentrations compared to surface water. Wastewater can also provide favorable conditions for the growth of a diverse bacterial community, which constitutes a basis for the selection and spread of antibiotic resistance, including genetic resistance to humans, livestock and poultry. Their elimination is very difficult by traditional biological treatment methods because they are hard biodegradable. Oxy-tetracycline (OTC) is one of the famous tetracyclines that have environmental risk. Nano zero valent Iron (NZVI) particles can be a new suggestion for OTC remediation. In this study, 155 ppm of OTC by 1000 ppm nano-scale zero valent iron with 200 W, UV-A radiation at pH of 3, were completely removed after 14 hours. The final products were carbon dioxide and water that were measured by a $CO_2$ analyzer. The iron compound on the surface of the nano zero valent Iron particles was Fe(OOH), which was determined by XRD analysis. Variations of parameter, including ORP, pH, and DO, during the removal process, were investigated for 6.5 hours. After 3 hours, the photocatalytic reaction by Fe(OOH) was started. The mechanism of OTC degradation was proposed by HPLC / ESI-MS and four by-products were obtained. The kinetic models for by-products were first order, and the rate constants, by the first order kinetic model, were found to be equal to 0.0099, 0.0021, 0.0049 and 0.0074 min-1, respectively. The effect of competitive ions, including calcium $(Ca^2+)$, magnesium $(Mg^2+)$, chloride $(Cl^-)$, nitrate $(NO_3)$, sulfate $(SO_4^2-)$ and bicarbonate $(HCO_3^-)$, with 10, 50, 100 and 200 ppm concentration, on OTC removal, were investigated. The results showed the negative effect of OTC removal by increasing the concentration of competitive ions, $NO_3^-$ $>$ $Ca^2+$ $approx$ $Mg^2+$ $>$ $Cl^-$. But $SO_4^2-$ and $HCO_3^-$ had no considerable effect. The kinetic model for OTC removal in the presence of all competitive ion concentrations was first order, but, for 10 ppm of $NO_3^-$, $Ca^2+$ and $Mg^2+$, were pseudo first order.
Keywords: Kinetic, Mechanism, ORP, Ph, DO, Competitive Ions -
در این تحقیق، پس ازانجام نیتریفیکاسیون مختصر در یک راکتور جریان جانبی ناپیوسته ی متوالی تحت شرایط مناسب از جمله دمای 30درجه ی سلسیوس، از لجن مازاد آن برای بررسی انجام نیتریفیکاسیون در راکتوری دیگر که تحت شرایط مختلف بهره برداری می شد،استفاده و نرخ ویژه ی نیتریفیکاسیون مورد بررسی قرار گرفت. نتایج حاصل پس از تجزیه و تحلیل آماری نشان داد که با استفاده از روش تاگوچی می توان تاثیر سایر عوامل به جز عامل موردنظر)مثلا دما(را بر نرخ واکنش حذف کرد. بر این مبنا مشخص شد که شوک کاهش دمایی باعث کاهش قابل ملاحظه ی نرخ واکنش تا 25، 55 و 78 درصد به ترتیب برای کاهش دما از 30 به 25، 20 و 15 درجه ی سلسیوس می شود و بر این اساس ضریب تصحیح دمایی برای اکسایندگان آمونیوم معادل 1٫0965به دست آمد.
کلید واژگان: شوک دمایی، اکسایندگان آمونیوم، ضریب تصحیح دما، تاگوچیB i o l o g i c a l p r o c e s s e s a r e k n o w n a s t e m p e r a t u r e-s e n s i t i v e i n w a s t e w a t e r t r e a t m e n t. N i t r i f i c a t i o n a n d, e s p e c i a l l y, p a r t i a l n i t r i f i c a t i o n (f i r s t s t e p o f n i t r i f i c a t i o n) a r e t h e m o s t t e m p e r a t u r e-s e n s i t i v e a m o n g b i o l o g i c a l p r o c e s s e s. F a c t o r s s u c h a s d i s s o l v e d o x y g e n, a m m o n i a c o n c e n t r a t i o n, M L V S S, a n d e t c, m a y i n f l u e n c e t w o s t e p s o f t h e n i t r i f i c a t i o n a n d o r g a n i s m g r o w t h r a t e, s o n i t r i f i c a t i o n s h o u l d b e d o n e b y c o n t r o l l i n g s o m e o f t h e s e f a c t o r s.I n t h i s s t u d y, b i o m a s s a c c l i m a t i o n i n a s i d e s t r e a m p a r t i a l n i t r i f i c a t i o n s e q u e n c i n g b a t c h r e a c t o r (S B R) u n d e r o p t i m u m c o n d i t i o n s f o r b i o l o g i c a l n i t r o g e n r e m o v a l (B N R) h a s b e e n e x a m i n e d. I n o r d e r t o s h o w t h e s u p e r i o r i t y o f a m m o n i a o x i d i z i n g b i o m a s s (A O B) o v e r n i t r i t e o x i d i z i n g b i o m a s s (N O B), e x c e s s s l u d g e f o r s o l i d r e t e n t i o n t i m e (S R T) r e g u l a t i o n w a s a d d e d t o a n o t h e r b a t c h r e a c t o r, w h i c h h a d b e e n p e r f o r m e d u n d e r d i f f e r e n t c o n d i t i o n s f o r s p e c i f i c a m m o n i u m o x i d a t i o n r a t e (s A O R) e v a l u a t i o n a n d c o l d s h o c k e f f e c t c o n s i d e r a t i o n. R e s u l t s o f t h e s i d e s t r e a m, p a r t i a l n i t r i f i c a t i o n, s e q u e n c i n g b a t c h r e a c t o r s h o w e d t h a t t h e s p e c i f i c a m m o n i u m o x i d a t i o n r a t e a t t h e e n d o f a n y c y c l e a n d a f t e r s t e a d y s t a t e c o n d i t i o n s w a s a b o u t 16.4 m g r V S S / h r. P r i m a r y r e s u l t s o f m a i n s t r e a m b a t c h t e s t s a f t e r a n a l y s i s b y t h e T a g u c h i m e t h o d d i s p l a y e d t h a t t h e p e r c e n t i n f l u e n c e o f c o n s i d e r a t i o n f a c t o r s i n c l u d e s t e m p e r a t u r e, i n i t i a l a m m o n i u m, M L V S S a n d t i m e, w h o s e s p e c i f i c a m m o n i u m o x i d a t i o n r a t e s w e r e a b o u t 98.5, 0.09, 0.06 a n d 1.3%, r e s p e c t i v e l y. S o, t e m p e r a t u r e i s a n i m p o r t a n t f a c t o r t h a t a f f e c t s t h e s p e c i f i c a m m o n i u m o x i d a t i o n r a t e. M o r e a n a l y s i s o n t h e r e s u l t s h a s s h o w n t h a t t h e e f f e c t s o f o t h e r f a c t o r s, e x c e p t t h e c o n s i d e r e d f a c t o r (e.g. t e m p e r a t u r e), o n s p e c i f i c a m m o n i u m o x i d a t i o n r a t e c a n b e e l i m i n a t e d u s i n g t h e T a g u c h i m e t h o d. B a s e d o n t h i s m e t h o d, i t w a s d e m o n s t r a t e d t h a t a b r u p t c o l d s h o c k c a u s e d a s i g n i f i c a n t r e d u c t i o n i n t h e p r o c e s s r a t e; u p t o 25, 55 a n d 78% f o r t e m p e r a t u r e r e d u c t i o n, f r o m 30 t o 25, 20 a n d 15$^o$C, r e s p e c t i v e l y. T h e r e f o r e, t h e t e m p e r a t u r e c o r r e c t i o n f a c t o r w a s c a l c u l a t e d a b o u t 1.0965 b y e l i m i n a t i o n o f o t h e r f a c t o r s e x c e p t t e m p e r a t u r e. T h e t e m p e r a t u r e c o r r e c t i o n f a c t o r w a s a l s o e s t i m a t e d t o b e a b o u t 1.106 u s i n g d i r e c t c o m p a r i s o n.
Keywords: Abrupt Cold Shock, Ammonia Oxidizing Bacteria, Temperature Correction Factor, Taguchi Method -
حذف رنگ از پساب های صنعتی، به خصوص کارخانجات نساجی و رنگرزی همواره از اقدامات مهم برای کنترل آلودگی های آنها است. وجود مقدار ناچیز رنگ در آب، شفافیت و غلظت اکسیژن محلول در آب را کاهش داده و در نتیجه حیات Astrazon Blue (F2RL) آبی محیط های پذیرنده را تهدید می کند. هدف این پژوهش ایجاد شرایط آزمایشگاهی برای حذف رنگ نساجی غلظت، pH، از محلول آبی به وسیله جذب آن با خاک اره و رس بنتونیت بوده است. جذب رنگ به داخل جاذب به ماهیت رنگ 100 برای mg/L 50 و، رنگ و زمان تماس وابسته است. بیشینه ی راندمان حذف رنگ از محلول های حاوی غلظت های اولیه رنگ 25 94 درصد به دست آمد. / 96 و 69 /78، 97/ 79 درصد و برای رس بنتونیت به ترتیب 32 / 91 و 26 /11، 96/ خاک اره به ترتیب 75 ایزوترم های تعادل به وسیله معادلات لانگمایر و فرندلیچ آنالیز شد. آنالیز نتایج آزمایشگاهی نشان داد که جذب رنگ خاک اره و رس بنتونیت با ایزوترم لانگمایر تطابق مطلوبی دارد. نتایج این پژوهش نشان داد که خاک اره و رس بنتونیت جاذب مناسبی برای حذف مواد رنگی نساجی از پساب های حاوی آن است.
کلید واژگان: رنگ زدایی، خاک اره، رس، لانگمایر، فرندلیچDyes and pigments are the major and important groups of chemical compounds with high amount of production and consumption amongst various environmental pollutants. For example, the annual imported amount of dye is over 7000 tons in Iran. Most of the dyes used in textile industries are considered either as inert or non-toxic, although some are not totally innocuous. The important fact is that most of them are made of carcinogenic chemicals that may be reformed as a result of metabolism. More than 50 percent of dyes consumed in different processes are discharged to wastewater, which in addition to changing the color of water, are preventing light penetration into the water and photosynthetic function that leads to destruction of aquatic ecosystem and some aquatic species. In recent years, increasing production and use of synthetic dyes, which have more complex structure and chemical stability as compared to natural dyes, more attention has been paid to their environmental pollution and importance of their treatment. Biological treatment is often the most economical alternative as compared to the physical and chemical treatment processes. But as most of dyes are hardly biodegradable, biological systems donot have capabilities in their removal. In expensive chemical processes, unexpected by- products and sludge are the main disadvantages. So, application of physical methods is preferred to control these kinds of pollutions. Different physical methods are also widely used, such as membrane–filtration processes and adsorption techniques. Adsorption is one of the most popular, flexible and effective methods that provides an attractive alternative for the treatment of colored water, especially if the sorbent is inexpensive and does not require an additional pre-treatment step before its application. It also does not result in the formation of harmful substances. Based on the aforementioned reasons, two adsorbents of sawdust and bentonite clay (absorbent aluminium phyllosilicate) were applied for the removal of cationic astrazon blue (F2RL) dye from wastewater regarding the two main factors of cost and availability in Iran, especially in the central provinces of the country. The parameters of pH, dye concentration and contact time were studied in this research. According to the study results, the optimum pH of 7 was found for the removal of dye for both sawdust and bentonite. Data analysis showed that increasing of the initial dye concentration resulted in the decreasing of removal efficiency. The maximum efficiency for the removal of dye from the solutions with the initial concentration of 25, 50 & 100 mg/L was 96.75, 91.11 & 79.26 percent for sawdust and 97.32, 96.78 & 94.62 percent for bentonite, respectively. The equilibrium time was 240 and 90 minutes for sawdust and bentonite, respectively. For the effect of adsorbent dosage on the removal of dye, experiments were carried out with two initial dye concentrations of 50 & 100 mg/L. By increasing of the adsorbent dosage, the maximum efficiency for the removal of dye from the solutions with the initial concentration of 50 and 100 mg/L increased from 53.46 to 97.06 percent and 49.76 to 96.83 percent, respectively, for sawdust, and from 90.78 to 99.64 and 86.44 to 99.46 percent, respectively, for bentonite clay. Analysis and calculation of separation factor (RL) of the result showed that adsorption of dye by sawdust and bentonite corresponds with Langmuir isotherm.
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