شوره‌سازی و شوره‌زدایی هم‌زمان در راکتور ناپیوسته متوالی هوازی با بستر متحرک تحت تأثیر COD/N

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، گروه آب و محیط زیست، دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران، تهران، ایران

2 استادیار، گروه آب و محیط زیست، دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران، تهران، ایران

10.22093/wwj.2019.191231.2892

چکیده

ترکیبات نیتروژنی نظیر آمونیوم و نیترات، از جمله متداول‌ترین آلاینده‌های موجود در فاضلاب‌ها و منابع آب هستند. حذف این ترکیبات از محیط‌های آبی، به‌منظور کاهش اثرات سوء محیط‌زیستی و بهداشتی آنها اهمیت به‌سزایی دارد. یکی از روش‌های بیولوژیکی حذف نیتروژن که به‌دلیل راهبری ساده و کم هزینه، امروزه مورد توجه قرار گرفته است، فرایند شوره‌سازی و شوره‌زدایی هم‌زمان (SND) است که به‌واسطه رشد چسبیده باکتریایی، امکان‌پذیر می‌شود. نسبت COD/N یکی از پارامترهای اثرگذار بر فرایند SND است که می‌تواند با اثرگذاری بر جرم بیوفیلم و جمعیت باکتریایی، عملکرد فرایند را تحت تأثیر قرار دهد. ازاین‌رو هدف از انجام پژوهش حاضر، بررسی تأثیر نسبت COD/N بر شوره‌سازی و شوره‌زدایی هم‌زمان در راکتور ناپیوسته متوالی هوازی با بستر متحرک (MBSBR) است. به این منظور یک راکتور MBSBR هوازی در دو فاز بهره‌برداری شد. نسبت COD/N در فازهای 1 و 2 به‌ترتیب برابر با 10 و 20 در نظر گرفته شد. طبق نتایج به‌دست‌آمده، افزایش دو برابری COD/N در خوراک ورودی به سیستم، موجب افزایش جرم بیوفیلم از 15 بهmg/media  25 و نیز افزایش قابل توجه COD خروجی از سیستم از 22 به 192 میلی‌گرم در لیتر، به‌ترتیب برای فازهای 1 و 2 شد، اما تأثیر قابل توجهی بر غلظت جامدات معلق نداشت. غلظت آمونیوم در جریان خروجی از سیستم در فاز 2 در حدود mg N/L 30 بود که به میزان 33 درصد نسبت به فاز 1 (mg N/L10) افزایش نشان داد. این مسئله نشان‌دهنده کاهش نرخ شوره‌سازی در فاز 2 بود که دلیل آن، افزایش جمعیت باکتری‌های هتروتروف و محدود شدن رشد اتوتروف‌ها در اثر وفور و افزایش قابل توجه غلظت ماده آلی در فاز 2 نسبت به فاز 1 تشخیص داده شد. همچنین در فاز 2، علی‌رغم افزایش جرم بیوفیلم و باقی ماندن بخشی از ماده آلی تا انتهای سیکل (عواملی که شرایط را برای شوره‌زدایی مطلوب‌تر می‌نماید)، شوره‌زدایی نیز با کاهش مواجه شد و از حدود 39 درصد در فاز 1 به 12 درصد در فاز 2 رسید. دلیل کاهش شوره‌زدایی در فاز 2، عدم انجام مناسب شوره‌سازی و کم بودن غلظت نیترات در این فاز بود. در نتیجه می‌توان گفت با افزایش COD/N، غلظت نیترات و یا به‌عبارت دیگر فرایند شوره‌سازی، به عامل کنترل‌کننده فرایند شوره‌زدایی تبدیل شده است. به‌طورکلی، در فاز 1 فرایند شوره‌سازی و شوره‌زدایی هم‌زمان به شکل مطلوب‌تری انجام شد و بازدهی حذف نیتروژن نسبت به فاز 2، بیش از سه برابر بود.

کلیدواژه‌ها


عنوان مقاله [English]

Simultaneous Nitrification and Denitrification in Aerobic Moving-Bed Sequencing Batch Reactor under the Effect of COD/N

نویسندگان [English]

  • Seyed Mohammad Javad Hoseiny Shams Abadi 1
  • Maryam Hasani Zonoozi 2
1 MSc Student, Water and Environment Group, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
2 Assist. Prof., Water and Environment Group, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
چکیده [English]

Nitrogen compounds such as ammonium and nitrate are among the most common pollutants in wastewater and water resources. Removal of these substances is essential for reducing their adverse environmental and health effects. One of the biological methods for eliminating nitrogen is the simultaneous nitrification and denitrification process (SND) which due to simplicity and cost effectiveness has attracted much interest. The SND can be performed by using bacterial attach growth. The COD/N ratio is one of the effective parameters on the SND process. It can influence the process performance by changing the biofilm mass and the bacterial population. For this reason, the purpose of this study was to investigate the effect of COD/N ratio on simultaneous nitrification and denitrification in aerobic moving-bed sequencing batch reactor (MBSBR). For this purpose, an aerobic MBSBR reactor was operated in two phases. The selected values for COD/N in phases 1 and 2 were 10 and 20, respectively. According to the results, doubling of COD/N significantly increased the biofilm mass from 15 mg/media to 25 mg/media and as well increased the effluent COD from 22 mg/L to 192 mg/L, for phases 1 and 2, respectively. However, it had trivial effect on the concentration of suspended solids. The ammonium concentration in effluent of phase 2 was around 30 mg N/L which was about 33% more than that of phase 1 (10 mg N/L). This indicates a decrease in the rate of ammonium oxidation in phase 2 which most probably was attributed to increase of the population of heterotrophic bacteria and inhibition of the growth of autotrophs as a result of the higher abundance of organic matter in this phase compared with phase 1. In phase 2, in spite of increasing biofilm mass and remaining part of the organic matter until the end of the cycle (the factors that make the conditions more desirable for denitrification), denitrification decreased and from about 39% in phases 1 reached to 12 % in this Phase. The reason for this observation was the lack of proper nitrification and low concentration of nitrate in phase 2. Therefore, it can be said that by increasing COD/N ratio, the nitrate concentration, or in the other words the nitrification process, has become the controlling factor of the denitrification process. In general, in phase 1 (COD/N of 10) simultaneous nitrification and denitrification took place much better so that more than threefold nitrogen removal efficiency was achieved compared with phase 2 (COD/N of 20).

کلیدواژه‌ها [English]

  • Simultaneous Nitrification and Denitrification (SND)
  • Moving-Bed Sequencing Batch Reactor (MBSBR)
  • COD/N Ratio
  • Biofilm
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