Application of response surface methodology to optimize the removal of nitrate from aqueous solutions using electrocoagulation

زمینه و هدف: نیترات یکی از مهم ترین آلاینده های موجود در طبیعت است که تهدیدی جدی برای بهداشت و سلامت انسان و کیفیت منابع آبی محسوب می شود. یکی از کارآمدترین روش های حذف این آلاینده، الکتروکواگولاسیون می باشد. روش بررسی: این مطالعه تجربی، در مقیاس پایلوت انجام گردید. نمونه ها به صورت سنتتیک و در غلظت های 300-100 میلی گرم بر لیتر نیترات تهیه گردید. متغیرهای مستقل شامل زمان واکنش، اختلاف پتانسیل الکتریکی و pH بودند. عملکرد فرایند بر اساس درصد حذف نیترات ارزیابی شد. تعیین تعداد آزمایشات، آنالیز آماری داده های آزمایشگاهی و بهینه سازی کارآیی حذف نیترات با به کارگیری روش پاسخ سطح و طرح مرکب مرکزی انجام شد. یافته ها: نتایج نشان داد که غلظت نیترات، زمان واکنش، اختلاف پتانسیل الکتریکی و pH، مربع غلظت نیترات و اثرات متقابل غلظت نیترات- اختلاف پتانسیل الکتریکی، غلظت نیترات- زمان واکنش، غلظت نیترات– pH و اختلاف پتانسیل الکتریکی- زمان واکنش، مهم ترین پارامترهای تأثیرگذار بر روی حذف نیترات به روش الکتروکواگولاسیون بودند. کارایی حذف نیترات در شرایط بهینه (زمان واکنش 68 دقیقه، اختلاف پتانسیل الکتریکی 17 ولت و pH برابر با 10، 88 بود. درجه مطلوبیت مدل در این شرایط 98 بود. نتیجه گیری: الکتروگواگولاسیون فرایندی موثر در کاهش نیترات است؛ همچنین روش پاسخ سطح با استفاده از طرح مرکب مرکزی برای بهینه سازی متغیرهای موثر در فرایند حذف نیترات به روش الکتروکواگولاسیون مناسب است

Comparative study of municipal solid waste generation and composition in Shiraz city (2014)

Background: Exponential growths of population and urbanization, and the development of social economy have resulted in an increase in the amount of MSW generation throughout the world. Objective: The present study aimed to survey qualitative and quantitative analysis of solid waste in Shiraz city and comparative these results with the world scenario of solid wastes generation for improving the sustainable management of solid waste. Methods: This cross-sectional study was conducted in 2014 in nine municipality regions Shiraz with a total population of approximately 1,549,354 people. Basic data was gathered through Shiraz waste management organization. Then generation (per capita) and constituent percent of the solid waste were evaluated based on the sampling and field analyzing from reliable guidelines. Data were analyzed with Stata-13 and Excel statistical software. Kolmogorov-Smirnov test used for the normality of variables. Means were compared by Student T test and Mann-Whitney test. Findings: The rate of solid waste generated in the Shiraz city was 222.65 kg per person per year in 2014. Statistical analysis showed that the variables of organic materials, paper and cardboard, glass and metal between developed and developing countries were a significant difference (P<0.05) while plastics and textiles and were not significantly different (P>0.05). Conclusion: Solid waste per capita in Shiraz city (about 600g/day) was near to the average amount of solid waste generation in Iran and other developing countries. Due to the high content of organic material in municipal solid waste of Shiraz, minimization of these material and separation of dry and wet solid wastes must be noted from the people and municipalities

Study of efficacy of date kernel ash on removal of nitrate from aqueous solutions (isothermic and kinetic study)

زمینه و هدف: در چند دهه گذشته، حضور غلظت بالای نیترات در آب آشامیدنی به یک نگرانی جدی تبدیل شده که باعث بروز اختلالاتی در سلامتی انسان به خصوص اطفال می شود؛ که با استفاده از روش های فیزیکی- شیمیایی و بیولوژیکی می توان آنرا حذف نمود. در این تحقیق میزان حذف نیترات از محلول های آبی با استفاده از خاکستر هسته خرما، مورد بررسی قرار گرفت. روش بررسی: در این مطالعه تجربی که در مقیاس آزمایشگاهی انجام شد، اثر غلظت اولیه نیترات (50، 100 و 150 میلی گرم بر لیتر) با PH (3، 5، 7 و 9)، زمان ماند (15، 30، 60، 120 و 180 دقیقه) و وزن جاذب (4/0، 6/0 و 8/0 گرم) مورد بررسی قرار گرفت. غلظت نیترات با استفاده از دستگاه اسپکتروفتومتر در دو طول موج 220 و 275 نانومتر اندازه گیری شد. کلیه آزمایشات و آنالیز نمونه به روش کتاب روش های استاندارد آب و فاضلاب انجام شد. یافته ها: افزایش دوز جاذب از 4/0 گرم به 8/0 گرم در 100 میلی لیتر از محلول نیترات با غلظت 50 و 100 میلی گرم در لیتر به ترتیب منجر به افزایش راندمان جذب از 75 به 91 و از 53 به 65 گردید. افزایش PH اولیه محلول از 3 به 9 منجر به کاهش راندمان جذب از 52 به 8 شد. داده های به دست آمده در این تحقیق، از ایزوترم فروندلیچ (98/0R2=) و جذب نیترات از مدل سینتیکی شبه درجه دوم تبعیت می کند (999/0R2=). نتیجه گیری: نتایج مطالعه حاضر نشان داد که خاکستر هسته خرما جاذب طبیعی و ارزان قیمتی است که می توان از آن برای حذف آلاینده های زیست محیطی استفاده کرد

Survey on hydrogen sulfide and ammonia emissions in the air around of the stabilization ponds Mineral gases producing odors in wastewater treatment

Abstract: (344 Views) Background and aims: Odors are one of the problems of water and wastewater treatment, especially in the vicinity of residential areas. Hydrogen sulfide and ammonia, mineral compounds in waste water treatment plants are odorous. These gases have unfavoraitable effects on humans and the environment. Methods: This Cross-sectional study was conducted in the Faculty of Health, Qazvin University of Medical Sciences. After field visits around the plant, the number of 12 sampling stations was determined. Sampling stations are selected in four geographical directions with regard to permanent trade winds that are zero, two and four kilo meters from the plant to Residential settlements. Sampling was performed in the morning and evening during the four seasons and 192 samples were provided. Results: Results showed that the concentration of ammonia and hydrogen sulfide gas was more in warm seasons significantly and more odor caused (P=0.011, P=0.004) and the maximum emission is in the summertime. According to the results, the highest concentration of these gases was in the evening during the day. Conclusion: According to the results, the concentration of hydrogen sulfide and ammonia gases in all the seasons except winter is within the threshold. Concentration of hydrogen sulfide in the summer and ammonia concentrations in all the seasons were higher than US. EPA standards and World Health Organization guidelines

Positive environmental effects of the coronavirus 2020 episode: a review

The outbreak of COVID-19 has made a global catastrophic situation that caused 1,039,406 deaths out of 35,347,404 infections, and it will also cause significant socio-economic losses with poverty increasing from 17.1 to 25.9%. Although the spreading rate of COVID-19 is very high on October 6, 2020, the death rate is still less than 2.94%. Nonetheless, this review article shows that the lockdown has induced numerous positive impacts on the environment and on energy consumption. For instance, the lockdown has decreased the electricity demand by 30% in Italy, India, Germany, and the USA, and by 12-20% in France, Germany, Spain, India, and the UK. Additionally, the expenditure of the fuel supply has been decreased by 4% in 2020 as compared to the previous years (2012-2019). In particular, The global demand for coal fuel has been reduced by 8% in March and April 2020 as compared to the same time in 2019. In terms of harmful emissions, the lockdowns reduced the emissions of nitrous oxides by 20-30% in China, Italy, France, Spain, and by 77.3% in São Paulo, Brazil. Similarly, the particulate matter level has been reduced from 5-15% in Western Europe, to 200% in New Delhi, India, which in turn has enhanced the air quality in a never-seen manner in recent times. In some places, such as New York, USA, CO2 emission was also reduced by 5-10%. The water quality, in several polluted areas, has also been remarkably enhanced, for example, the dissolved oxygen content in the Ganga River, India, has increased by about 80%. Traffic congestion has also been reduced worldwide, and in some areas, it has been reduced by 50%, such as New York and Los Angeles, USA. Overall, while the COVID-19 pandemic has shrinked the global economy by 13-32%, the pandemic has also clearly benefited to other sectors, which must be considered as the spotlight for the permanent revival of the global ecosystem. Keywords: Air pollution; COVID-19 benefits; Environmental regeneration; Renewable energy; Surface water; Traffic congestion

Assessment of microbial contamination in drinking water supplies Qazvin city (2013-14)

Background: Providing safe drinking water and monitoring the quality are necessary in the human societies. Objective: The aim of study was to evaluate the microbial quality of groundwater of Qazvin city. Methods: This cross-sectional study was performed to evaluate the microbial quality of 45 drinking water resources Qazvin city in terms of total coliform and fecal. Sampling was done in the winter to spring during 2013-14. Sample analysis was performed using standard multiple tube fermentation (3 tubes) method for total coliform and fecal counting. Findings: Total coliform and fecal concentration were zero in all taken samples and all samples were free of microbial contamination of total and fecal coliform. Conclusion: Microbial quality of drinking water supplies of Qazvin city was favorable in terms of total and fecal coliforms and in accordance with the standards of the country in relation to microbial contamination, But in order to maintain the desirability, continuous monitoring of the water and wastewater company is very important on the quality of the supply sources of drinking water

Comparative study of municipal solid waste generation and composition in Shiraz city (2014)

Background: Exponential growths of population and urbanization, and the development of social economy have resulted in an increase in the amount of MSW generation throughout the world. Objective: The present study aimed to survey qualitative and quantitative analysis of solid waste in Shiraz city and comparative these results with the world scenario of solid wastes generation for improving the sustainable management of solid waste. Methods: This cross-sectional study was conducted in 2014 in nine municipality regions Shiraz with a total population of approximately 1,549,354 people. Basic data was gathered through Shiraz waste management organization. Then generation (per capita) and constituent percent of the solid waste were evaluated based on the sampling and field analyzing from reliable guidelines. Data were analyzed with Stata-13 and Excel statistical software. Kolmogorov-Smirnov test used for the normality of variables. Means were compared by Student T test and Mann-Whitney test. Findings: The rate of solid waste generated in the Shiraz city was 222.65 kg per person per year in 2014. Statistical analysis showed that the variables of organic materials, paper and cardboard, glass and metal between developed and developing countries were a significant difference (P<0.05) while plastics and textiles and were not significantly different (P>0.05). Conclusion: Solid waste per capita in Shiraz city (about 600g/day) was near to the average amount of solid waste generation in Iran and other developing countries. Due to the high content of organic material in municipal solid waste of Shiraz, minimization of these material and separation of dry and wet solid wastes must be noted from the people and municipalities