28026

هم‌كشتي ميكروجلبك و باكتري جهت تصفيه پساب سنتزي

كارشناسي ارشد

مهندسي شيمي

1398

1401/12/10

فرشته نعيم پور

مهندسي نفت گاز شيمي

Human activities results in formation of a large volume of wastewater containing carbon, nitrogen and phosphorus which should be treated before releasing into environment. Although activated sludge has been widely used in wastewater treatment, co-cultivation of microalgae and bacteria has recently been proposed with the aim of increasing the efficiency of nutrients removal and reducing the costs. In this research, the co-cultivation of Chlorella vulgaris and Pseudomonas aeruginosa in synthetic wastewater was investigated aiming at enhancing nutrients removal and improving growth and cell content. Firstly, the effect of level of glucose as organic carbon as well as the ratio of two cells in inoculum as two important factors in formation of consortium were investigated. According to the optimal results, subsequent experiments were designed and performed .Co-cultivation performance was then compared with the single culture of microalgae and bacteria after 144 hours under photo-, hetro, and mixo-trophic conditions (According to the optimal level of glucose & inoculum ratio obtained from previous experiment). Finally, the effect of two-stage co-cultivation at different nitrate levels (400 and 800 mg/L) and illumination strategies (24h L: 0h D light and 16L: 8D light cycle) were examined (Considering the results of optimal metabolism obtained from previous experiment). Glucose as organic C-source at 2 gr/L and inoculation ratios of microalgae to bacteria at 50:50 and 70:30 were found appropriate for cultivation of co-culture. Mixotrophic co-cultivation was superior to microalgae alone with removals of up to 99% carbon, 43% nitrate and 99% phosphorus (after 96 h) compared to 76% carbon, 23% nitrate and 99% phosphorus (after 144 h). Biomass, starch and lipid contents under mixotrophic co-cultivation were 8.7 and 2.1% higher compared to single microalga culture. Two-stage co-cultivation showed that this method improved carbon removal up to 12% in 84 hours compared to conventional co-cultivation. Illumination for 24 h as opposed to cyclic lighting initial nitrate level of 400 instead of 800 mg/L enhanced biomass lipid and starch contents by 30% compared to single stage, reaching final lipid and starch contents of 737 and 461 mg/L, respectively. Co-cultivation increased the rate of sedimentation up to 3 times compared to single cultivation. The results of this research showed that microalgae and bacteria consortium can enhance nutrient removal efficiency and lipid & starch contetn in addition to facilitating the sedimentation process.

1401/12/21

Synthetic wastewater treatment using symbiotic co-culture of microalgae and bacteria

2/29/2024 12:00:00 AM

مقادير زيادي از پساب¬هاي حاوي مواد مغذي كربن، نيتروژن و فسفر به دليل فعاليت¬¬‌هاي انساني توليد مي-شوند كه لازم است قبل از رهاسازي در طبيعت تصفيه شوند. اگرچه تصفيه بيولوژيكي با لجن فعال سال¬ها كه مورد استفاده قرار گرفته است، در سال‌هاي اخير استفاده از هم¬كشتي ميكروجلبك و باكتري باهدف افزايش راندمان حذف مواد مغذي و كاهش هزينه¬هاي تصفيه، مطرح شده است. در اين تحقيق، هم‌كشتي ميكروجلبك كلرلاولگاريس و باكتري سودوموناس آئروژينوزا در پساب سنتزي با هدف افزايش راندمان حذف مواد مغذي و بهبود رشد و محتواي سلولي مورد بررسي قرار گرفت. در ابتدا به بررسي اثر غلظت اوليه كربن آلي و نسبت اوليه تلقيح به‌عنوان دو عامل مهم در شكل¬گيري كنسرسيوم ميكروبي پرداخته شد. سپس با توجه به غلظت منبع كربن و نسبت تلقيح بهينه شده در آزمايش‌هاي قبل، به مقايسه عملكرد هم‌كشتي با كشت منفرد ميكروجلبك و باكتري در حالت‌هاي فتو-، هترو- و ميكسوتروفيك پرداخته شد. در انتها نيز با توجه به متابوليسم بهينه در حذف مواد مغذي، اثر كشت دومرحله‌اي بر هم-كشتي در دو غلظت اوليه نيترات و دو استراتژي متفاوت نوردهي و نيز تأثير هم¬كشتي بر سرعت ته¬نشيني پرداخته شد. طبق نتايج، غلظت مناسب كربن gr/L 2 و بهترين نسبت تلقيح ميكروجلبك به باكتري در نسبت¬هاي 50:50 و70:30 مشاهده شد. نتايج نشان داد هم¬كشتي ميكسوتروفيك بالاترين حذف كربن (99%)، نيتروژن (43%) و فسفر (99% بعد از 96 ساعت) و سپس ميكروجلبك منفرد در شرايط هتروتروفيك با حذف كربن (76%) و نيتروژن (23%) و فسفر (99% بعد از 144 ساعت) در رتبه بعدي قرار دارد. نتايج رشد و محتواي نشاسته و ليپيد بايومس در شرايط ميكسوتروفيك نيز نشان داد هم¬كشتي علي¬رغم كاهش توليد زيست توده نسبت به ميكروجلبك منفرد (%28 كمتر)، محتواي ليپيد و نشاسته را به ترتيب تا ميزان %7/8 و %1/2 داده است. كشت دومرحله¬اي نسبت به هم¬كشتي معمول، سبب بهبود حذف كربن تا ميزان 12% در مدت 84 ساعت شده است. نوردهي پيوسته به‌جاي سيكلي در كشت دومرحله‌اي در غلظت پايين‌تر نيتروژن (400 به‌جاي 800 ميلي‌گرم بر ليتر) مي¬تواند تا ميزان 30% سبب افزايش محتواي ليپيد و نشاسته شود به‌طوري‌كه محتواي ليپيد و نشاسته در انتهاي آزمايش به ترتب به مقادير 737 و mg/L 461 رسيد. همچنين استفاده از هم¬كشتي نسبت به كشت منفرد مي‌تواند سرعت ته‌نشيني را تا ميزان 3 برابر افزايش دهد. نتايج اين تحقيق نشان مي¬دهد كنسرسيوم¬هاي¬ ميكروجلبك و باكتري مي‌توانند باعث افزايش راندمان حذف مواد مغذي و افزايش محتواي ليپيد زيست توده و همچنين مزيت عدم نياز به هوادهي و تسهيل فرايند ته¬نشيني را به همراه داشته باشند.

حذف مواد مغذي ، تصفيه بيولوژيكي پساب سنتزي، هم‌كشتي ميكروجلبك و باكتري

Human activities results in formation of a large volume of wastewater containing carbon, nitrogen and phosphorus which should be treated before releasing into environment. Although activated sludge has been widely used in wastewater treatment, co-cultivation of microalgae and bacteria has recently been proposed with the aim of increasing the efficiency of nutrients removal and reducing the costs. In this research, the co-cultivation of Chlorella vulgaris and Pseudomonas aeruginosa in synthetic wastewater was investigated aiming at enhancing nutrients removal and improving growth and cell content. Firstly, the effect of level of glucose as organic carbon as well as the ratio of two cells in inoculum as two important factors in formation of consortium were investigated. According to the optimal results, subsequent experiments were designed and performed .Co-cultivation performance was then compared with the single culture of microalgae and bacteria after 144 hours under photo-, hetro, and mixo-trophic conditions (According to the optimal level of glucose & inoculum ratio obtained from previous experiment). Finally, the effect of two-stage co-cultivation at different nitrate levels (400 and 800 mg/L) and illumination strategies (24h L: 0h D light and 16L: 8D light cycle) were examined (Considering the results of optimal metabolism obtained from previous experiment). Glucose as organic C-source at 2 gr/L and inoculation ratios of microalgae to bacteria at 50:50 and 70:30 were found appropriate for cultivation of co-culture. Mixotrophic co-cultivation was superior to microalgae alone with removals of up to 99% carbon, 43% nitrate and 99% phosphorus (after 96 h) compared to 76% carbon, 23% nitrate and 99% phosphorus (after 144 h). Biomass, starch and lipid contents under mixotrophic co-cultivation were 8.7 and 2.1% higher compared to single microalga culture. Two-stage co-cultivation showed that this method improved carbon removal up to 12% in 84 hours compared to conventional co-cultivation. Illumination for 24 h as opposed to cyclic lighting initial nitrate level of 400 instead of 800 mg/L enhanced biomass lipid and starch contents by 30% compared to single stage, reaching final lipid and starch contents of 737 and 461 mg/L, respectively. Co-cultivation increased the rate of sedimentation up to 3 times compared to single cultivation. The results of this research showed that microalgae and bacteria consortium can enhance nutrient removal efficiency and lipid & starch contetn in addition to facilitating the sedimentation process.

Majed Tavakkol

Dr. Fereshteh Naeimpoor