جداسازي توده هاي ميكروبي در راكتورهاي زيست فيلمي بستر متحرك به وسيله ي صافي هاي دست ساز

Biomass Separation in Moving Bed Biofilm Reactors with Innovative Filters

يكي از عيب هاي راكتورهاي زيستي بستر متحرك،خروج توده هاي ميكروبي، همراه پساب تصفيه شده ي خروجي از سامانه است كه وجود مخزن ته نشيني بعد از راكتور را ضروري مي كند. به طور معمول براي رفع مشكل هاي ناشي از نصب ته نشين كننده ها، از سامانه هاي غشايي استفاده مي شود اما از عيب هاي عمده اين سامانه ها ، هزينه زياد غشاهاي صنعتي است. هدف از اين مطالعه ، نصب صافي هاي دست ساز به جاي غشاي صنعتي، درون راكتورهاي زيستي بستر متحرك، براي جلوگيري از خروج توده هاي ميكروبي و حذف مخزن ته نشيني و مقايسه آن با راكتور زيستي بستر متحرك بدون صافي است كه افزون بر اين كه كار غشا را انجام مي دهد ، مشكل هاي ناشي از هزينه زياد غشاهاي صنعتي را نداشته و اقتصادي تر است. صافي ها از پارچه و الياف ساخته شده و طي سه مرحله تكميل تر شدند. تعداد صافي هايي كه مورد آزمايش قرار گرفتند به ترتيب، سه ، دو و يك عدد بودند و در زمان هاي ماند 48 ، 24 و 18 ساعت با COD برابر با mg/L 1000 وmg/L 3000 و mg/L5000 مورد آزمايش قرار گرفتند. سه صافي، غلظت جامدهاي معلق در مايع خروجي را بهmg/L 12 رسانيد كه توانست جايگزين مخزن ته نشيني شود، دو صافي هم اين غلظت را به mg/L 300در خروجي رسانيد كه مي توانست جايگزين ته نشين كننده ها شود اما تك صافي ، تفاوت زيادي با راكتور زيست فيلمي بستر متحرك بدون صافي نداشت و نتوانست جايگزين مخزن ته نشيني شود. بيشترين بازده حذف در راكتور صافي دار 95% و در راكتور بدون صافي 92% بوده است.

Membrane bioreactors (MBR Process) are now considered as one of the main new processes in wastewater treatment. Membranes used for wastewater purification are fabricated from different oil based polymers including PVC, polysulphonates, polyamides and many other synthetic polymers. Fabrication technology is advanced and only in possession of very few multinational companies. For these reasons, membranes are expensive and not easily available. This study was carried out to test an innovative, locally made filter element for separation of flocks in an MBBR reactor. This innovative filter is seen as a viable replacement to a conventional settling tank that may be even as effective as synthetic polymer membranes. The filter’s element was made very cheaply and had important advantages in installing and operation. Experiments were carried out using a laboratory scale MBBR unit as the biological aerated reactor, fixed with filter elements inside aeration chamber, similar to a MBR installation. The filter elements consisted of 3 plastic filter tubes with perforations and covered with dense cotton-polyester yarns and were placed inside the aeration chamber. The bioreactor was run over a period of 10 months with usual conditions resembling a real biological wastewater treatment unit. Reactor performance was measured regularly and the results indicated that 99% of suspended solids are separated under normal conditions. Filter clogging, a very familiar problem with membrane bioreactors, was not seen as an obstacle in bioreactor operation. Outflow TSS was lower than 12 mg/L, while overall organic removal was over 95 percent. Next set of experiments were carried with fewer filter elements and higher value of TSS in the effluent was observed, indicating that filters surface area (or number of filter elements) have a profound effect on treatment efficiency as could be well expected. Overall the experiments indicated that locally made MBR can easily be applied in existing plants, saving money and operational difficulties.