Biological nutrient removal in the combined ufflow sludge blanket and rotating biological contactor systems
Biological nutrient removal in the combined ufflow sludge blanket and rotating biological contactor systems
Dosyalar
Tarih
2000
Yazarlar
Kınlı, Hilal
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Institute of Science and Technology
Özet
Bu çalışmada, atıksu arıtımında konvansiyonel olarak kullanılan ünitelerden Yukarı Akışlı Çamur Yatağı (YAÇY) reaktörü, Döner Biyolojik Disk (DBD) reaktörü ve çöktürme tankı birleştirilerek birleşik sistem oluşturulmuş ve bu sistem biyolojik besi maddesi giderimine adapte edilmiştir. Söz konusu birleşik sistemin biyolojik besi maddesi gideriminde kullanılması ilk olarak bu çalışmada gerçekleştirilmiştir. Çalışmada kullanılan YAÇY reaktörü pleksiglas bir kolondan imal edilmiş olup 8.4 1 etkili sıvı hacmine sahiptir. Reaktörün tepe kısmında gaz-sıvı-katı ayırıcısı bulunmaktadır. Çalışmada kullanılan DBD reaktörü pleksiglas malzemeden yapılmış ve yatay bir şaft üzerine 2 cm aralıkla monte edilmiş atıksuyun yönüne dik olarak hareket eden birbirine paralel 20 adet diskten oluşmaktadır. Diskler 30 cm çapında ve 0.5 cm kalınlığında olup mikroorganizmaların gelişmesine elverişli toplam yüzey alanları 2.6 m2,dir. Diskler 29.5 1 hacimli bir tankta çaplarının %33'üne kadar batık halde bulunmaktadır. Çalışmada kullanılan çöktürme tankı pleksiglas bir kolondan imal edilmiş olup etkili sıvı hacmi 3.9 litredir. Söz konusu sistem sıcaklığı 20°C±1 olarak kontrol edilen bir laboratuvarda kurulmuştur. Besleme çözeltisi evsel atıksu kompozisyonunda sentetik olarak hazırlanmıştır. Besleme çözeltisinin TOK konsantrasyonu 70 mg/1, Top.N konsantrasyonu 1 9 mg/1 ve Top.P konsantrasyonu 14 mg/Fdir. Deneysel çalışmaların bazı bölümlerinde besleme çözeltisine ekstra karbon kaynağı olarak asetik asit ilave edilmiştir. Asetik asit ilave edildikten sonra besleme çözeltisinin TOK konsantrasyonu 220 mg/l'ye yükselmiştir. Birleşik sistemde besleme çözeltisi bir pompa vasıtasıyla YAÇY reaktörüne beslenmiştir. YAÇY reaktörünün çıkışı DBD reaktörü çıkışına transfer edilmiştir. DBD reaktörünün çıkışı çöktürme tankına verilmiştir. Çöktürme tankında çöken çamur bir pompa vasıtasıyla YAÇY reaktörünün girişine geri devrettirilmiştir. Çöktürme tankının süzüntüsü ise deşarj edilmiştir. Birleşik sistemde üç adet örnekleme noktası belirlenmiştir. Örneklerden birincisi besleme çözeltisi tankından, ikincisi YAÇY reaktörü çıkışından (bir başka deyişle DBD reaktörü girişinden), üçüncüsü ise birleşik sistemin çıkışından olmak üzere haftada iki kere örnekleme yapılmıştır. Her üç noktadan alınan örneklerde pH, TOK, TKN, (NH4-N, NO3-N, (NO2-N, PO4-P ve Top.P parametrelerinin ölçüm ve analizi yapılmıştır. YAÇY girişinden numune alınamadığından TOK, TKN, NH4-N, NO3-N, xxıı NO2-N, PO4-P ve Top.P parametrelerinin konsantrasyonları kütle dengesi yoluyla hesaplanmıştır. DBD reaktörünün tankında çözünmüş oksijen konsantrasyonu haftada iki kere örnekleme yapılan günlerde ölçülmüştür. Birleşik sistem kararlı denge durumuna eriştiğinde DBD reaktörünün tankından ve YAÇY reaktörünün numune alma musluklarından numune alınarak AKM ve UAKM analizleri yapılmıştır. Deneysel çalışmalar üç grupta gerçekleştirilmiştir. Birinci grupta yapılan deneysel çalışmalarda çöktürme tankından YAÇY reaktörüne geri devir oranının birleşik sistemin biyolojik besi maddesi giderimine etkisi incelenmiştir. Besleme çözeltisi sentetik olarak evsel atıksu kompozisyonunda hazırlanmış ve ekstra karbon kaynağı olarak kullanılan asetik asit besleme çözeltisine ilave edilmiştir. Birinci grup deneysel çalışmalar süresince birleşik sistemin giriş atıksu debisi 37 l/gün' e ayarlanmıştır. Hidrolik kalış süresi YAÇY reaktöründe 5.4 saat, DBD reaktöründe 19.1 saat ve çöktürme tankında 2.5 saat olmuştur. Çöktürme tankından YAÇY reaktörüne geri devir debisi başlangıçta 47 l/gün' e ayarlanmış, birleşik sistem kararlı denge durumuna eriştiğinde adım adım 459 l/gün' e kadar artırılmıştır. Böylelikle geri devir oram başlangıçta 1.3 iken 12.4' e kadar artırılmıştır. Geri devir oram 1.3'ten 12.4'e artırıldığında, TOK giderim veriminde bir değişiklik gözlenmemiştir. Sisteme verilen sabit 8.1 g/gün TOK yükünde ve denenen tüm geri devir oranlarında TOK giderim verimi yaklaşık %95 olmuştur. TKN giderim verimi tüm geri devir oranlarında yüksek olmuştur. Birleşik sisteme verilen 0.7 g/gün sabit TKN yükünde sistemde TKN giderim verimi %96-99 aralığında değişmiştir. YAÇY reaktöründe TKN giderimi ihmal edilecek seviyede olmuş ve TKN giderimi yalnızca DBD reaktöründe gerçekleşmiştir. Birleşik sistemde Top.N giderimi denenen tüm geri devir oranlarında yalnızca YAÇY reaktöründe gerçekleşmiştir. Geri devir oram 1.3'ten 12.4'e artırıldığında ve birleşik sisteme uygulanan sabit 0.7 g/gün Top.N yükünde, Top.N giderim verimi %61 'den %8 1 'e artmıştır. Birleşik sistemde Top.P giderimi yalnızca DBD reaktöründe gerçekleşmiştir. Geri devir oram 1.3'ten 12.4'e artırıldığında ve birleşik sisteme verilen 0.52 g/gün sabit Top.P yükünde, Top.P giderim verimi %18'den %39'a yükselmiştir. Birinci grupta yapılan deneysel çalışmalarda, YAÇY reaktöründe toplam AKM değerleri 89000-100000 mg aralığında, toplam UAKM değerleri de 68000-79000 mg aralığında değişmiştir. DBD reaktörünün tankında toplam AKM değerleri 45200- 68600 mg aralığında, toplam UAKM değerleri de 33700-49400 mg aralığında değişmiştir. Çözünmüş oksijen konsantrasyonu DBD reaktörü tankında 4.5-5.9 mg/1 aralığında değişmiştir. pH değerleri; besleme çözeltisinde 5.4-6.6 aralığında, YAÇY reaktörünün çıkışında (veya DBD reaktörünün girişinde) 6.4-7 aralığında, birleşik sistemin çıkışında 6.3-7.2 aralığında değişmiştir. İkinci grupta yapılan deneysel çalışmalarda, birinci grupta birleşik sisteme uygulanan hidrolik yükleme değerlerinden daha yüksek değerlerde birleşik sistemin biyolojik besi maddesi giderim hızı araştırılmıştır. İkinci grupta yapılan deneysel çalışmalarda xxiii kullanılan besleme çözeltisi, birinci grupta yapılan deneysel çalışmalarda kullanılan besleme çözeltisi ile aynı özellikte hazırlanmıştır. Deneysel çalışmalar sırasında birleşik sisteme verilen giriş atıksu debisi başlangıçta 37 l/gün' e ayarlanmış, birleşik sistem kararlı denge durumuna eriştiğinde adım adım 93.5 1/gün'e artırılmıştır. Hidrolik kalış süresi YAÇY reaktöründe 5.4 saatten 2.2 saate, DBD reaktöründe 19.1 saatten 7.6 saate, çöktürme tankında 2.5 saatten 1 saate düşmüştür. Çöktürme tankının dip kısmından YAÇY reaktörüne geri devir debisi başlangıçta 307 1/gün'e ayarlanmıştır. Söz konusu geri devir debisinde başlangıç geri devir oranı 8.3 olup bu değer birinci grupta yapılan deneysel çalışmalarda biyolojik besi maddesi giderimi açısından optimum olarak bulunan değerler arasındadır. Sisteme verilen giriş atıksu debisi kademeli olarak 93.5 1/gün'e artırıldığında, geri devir oram 8.3 'ten 3. 9'a düşmüştür. Birleşik sisteme uygulanan TOK yükü 8.1 g/gün'den 20.6 g'gün'e artırıldığında TOK giderim verimi %96 ile %97 aralığında değişmiştir. Birleşik sistemde TOK giderimi YAÇY ve DBD reaktörlerinin her ikisinde de gözlenmiştir. Birleşik sisteme uygulanan TKN yükü 0.7 g/gün'den 1.78 g/gün'e artırıldığında, birleşik sistemde TKN giderim verimi %95 ile %98 aralığında değişmiştir. Birleşik sisteme uygulanan maksimum 1.78 g/gün TKN yükünde birleşik sistemde TKN giderim hızı 1.74 g/gün olmuş, bunun 1.24 g/gün'ü DBD reaktöründe, 0.5 g/gün'ü ise YAÇY reaktöründe gerçekleşmiştir. Birleşik sisteme uygulanan Top.N yükü 0.7 g/gün'den 1.78 g/gün'e artırıldığında birleşik sistemde Top.N giderim verimi %82'den %97'ye lineer olarak artmıştır. Top.N giderimi birleşik sisteme uygulanan 1.08 g/gün Top.N yükü değerine kadar yalnızca YAÇY reaktöründe gerçekleşmiş, daha yüksek Top.N yükü değerlerinde DBD reaktöründe de Top.N giderimi gözlenmiştir. Birleşik sistemde Top.P giderimi yalnızca DBD reaktöründe gözlenmiştir. Birleşik sisteme uygulanan Top.P yükü 0.52 g/gün'den 1.31 g/gün'e artırıldığında, sistemde Top.P giderim verimi %18'den %91'e artmıştır. İkinci grupta yapılan deneysel çalışmalarda, YAÇY reaktöründe toplam AKM değerleri 86300-100000 mg aralığında, toplam UAKM değerleri de 66400-75200 mg aralığında değişmiştir. DBD reaktörünün tankında toplam AKM değerleri 35600- 68200 mg aralığında, toplam UAKM değerleri de 26100-50300 mg aralığında değişmiştir. Birleşik sisteme beslenen atıksu debisi 37 1/gün'den 93.5 1/gün'e artırıldığında, DBD reaktörü tankında çözünmüş oksijen konsantrasyonu 4.5-5.5 mg/1 seviyesinden 2.9-3.3 mg/1 seviyesine düşmüştür. pH değerleri; besleme çözeltisinde 5.4-6.1 aralığında, YAÇY reaktörünün çıkışında (veya DBD reaktörünün girişinde) 5.7-6.8 aralığında, birleşik sistemin çıkışında 6.5-6.9 aralığında değişmiştir. Üçüncü grupta yapılan deneysel çalışmalarda evsel atıksu özelliklerinde sentetik olarak hazırlanan besleme çözeltisine ekstra karbon kaynağı olarak asetik asit ilave edilmemiştir. Birinci ve ikinci grupta yapılan deneysel çalışmalarda birleşik sisteme uygulanan hidrolik yüklerden daha yüksek hidrolik yükleme değerlerinde birleşik sistemde biyolojik besi maddesi giderimi araştırılmıştır. XXIV Birleşik sistemin giriş atıksu debisi başlangıçta 70 l/gün olarak seçilmiş ve sistem kararlı denge durumuna eriştiğinde adım adım 260 l/gün' e artırılmıştır. Hidrolik kalış süresi; YAÇY reaktöründe 2.9 saatten 0.8 saate, DBD reaktöründe 10.1 saatten 2.7 saate, çöktürme tankında 1.3 satten 0.4 saate düşmüştür. Çöktürme tankının dip kısmından YAÇY reaktörüne geri devir oram olarak, ikinci grupta yapılan deneysel çalışmalarda optimum biyolojik besi maddesi giderimi sonuçlarının elde edildiği 3.9 değerine çok yakın bir değer olan 3.2 değeri seçilmiştir. Birleşik sisteme verilen giriş atıksu debisi kademeli olarak 70 l/gün' den 260 l/gün' e artırıldığında, geri devir oram 3.2'den 1.4'e düşmüştür. Birleşik sisteme uygulanan TOK yükü 4.9 g/gün'den 18.2 g/gün'e artırıldığında birleşik sistemde TOK giderim verimi oldukça yüksek olmuş ve %87 ile %93 aralığında değişmiştir. Birleşik sisteme uygulanan 18.2 g/gün maksimum TOK yükünde, birleşik sistemde TOK giderim hızı 16.4 g/gün olmuş, bunun 12.9 g/gün'ü YAÇY reaktöründe, 3.5 g/gün'ü ise DBD reaktöründe gerçekleşmiştir. Birleşik sistemde TKN giderim verimi birleşik sisteme uygulanan 3.4 g/gün TKN yüküne kadar oldukça yüksek olmuş ve %95-98 aralığında değişmiştir. 3.4 g/gün'den daha yüksek TKN yükü değerlerinde TKN giderim veriminde bir azalma gözlenmiş, 4.94 g/gün maksimum TKN yükünde birleşik sistemde TKN giderim verimi %88'e düşmüştür. Birleşik sisteme uygulanan maksimum 4.94 g/gün TKN yükünde, birleşik sistemde 4.37 g/gün olan TKN giderim hızının 0.45 g/gün'ü YAÇY reaktöründe, 3.92 g/gün'ü ise DBD reaktöründe gerçekleşmiştir. Birleşik sisteme uygulanan Top.N yükü 1.33 g/gün'den 4.94 g/gün'e artırıldığında Top.N giderim verimi %68'den %53'e azalmıştır. Birleşik sisteme verilen maksimum 4.9 g/gün Top.N yükünde birleşik sistemde Top.N giderim hızı 2.6 g/gün olmuş, bunun 2.1 g/gün'ü YAÇY reaktöründe, 0.5 g/gün'ü ise DBD reaktöründe gerçekleşmiştir. Birleşik sisteme uygulanan 3 g/gün Top.P değerine kadar birleşik sistemde Top.P giderim hızı 0.39 g/gün ile 0.69 g/gün aralığında değişmiştir. 3 g/gün'den daha yüksek Top.P yükü değerlerinde Top.P giderim hızı hızla azalmıştır. Öte yandan birleşik sisteme verilen Top.P yükü 1 g/gün'den 3.6 g/gün'e artırıldığında Top.P giderim verimi %51'den %1'e sürekli olarak azalmıştır. Üçüncü grupta yapılan deneysel çalışmalarda, YAÇY reaktöründe toplam AKM değerleri 62900-83900 mg aralığında, toplam UAKM değerleri de 49600-66000 mg aralığında değişmiştir. DBD reaktörünün tankında toplam AKM değerleri 40900- 77000 mg aralığında, toplam UAKM değerleri de 30000-56500 mg aralığında değişmiştir. Birleşik sisteme beslenen atıksu debisi 70 1/gün'den 260 1/gün'e artırıldığında, DBD reaktörü tankında çözünmüş oksijen konsantrasyonu 6.2-7.1 mg/1 seviyesinden 3.5-4.1 mg/1 seviyesine düşmüştür. pH değerleri; besleme çözeltisinde 6-7.4 aralığında, YAÇY reaktörünün çıkışında (veya DBD reaktörünün girişinde) 6.6-7.4 aralığında, birleşik sistemin çıkışında 7-7.6 aralığında değişmiştir. Bu çalışmadan elde edilen temel sonuçlar aşağıda verilmektedir;. Her üç grupta yapılan deneysel çalışmalarda, birleşik sisteme uygulanan tüm işletme şartlarında birleşik sistemde TOK ve TKN giderim verimleri oldukça XXV yüksek olmuştur. Top.N ve Top.P giderim verimleri ise işletme şartlarından etkilenmiştir.. Birleşik sistemde bulunan YAÇY, DBD ve çöktürme ünitelerindeki hidrolik kalma zamanının toplamı olan toplam hidrolik kalma zamanının (THKZ) biyolojik besi maddesi gideriminde önemli bir parametre olduğu bulunmuştur. Birleşik sistemde etkin bir besi maddesi giderimi için geri devir oranının seçiminin de THKZ ile yakın ilişkili olduğu görülmüştür. Birinci grupta yapılan deneysel çalışmalarda, 27 saat sabit THKZ'nda maksimum Top.N ve Top.P giderim verimleri 6 ile 12.4 geri devir oranlan arasında sırasıyla %84 ve %39 olarak elde edilmiştir. İkinci grupta yapılan deneysel çalışmalarda, THKZ 27 saatten 11 saate düştüğünde, geri devir oram da 8.3'ten 3.9'a düşmüş, Top.N giderim verimi %84'ten %97'ye, Top.P giderim verimi de %39'dan %91'e artmıştır.. THKZ'nın yam sıra, besleme çözeltisindeki TOC/N/P oranlarının da birleşik sistemde biyolojik besi maddesi giderimi için önemli bir parametre olduğu görülmüştür. Besleme çözeltisindeki TOC/N/P oranlan ikinci grup deneysel çalışmalarda 15.7/1.3/1, üçüncü grup deneysel çalışmalarda ise 5/1.3/1 olmuştur. Optimum geri devir oranlan ve THKZ'lan ikinci grupta 3.9 ve 11 saat, üçüncü grupta ise 3.2 ve 14 saat olarak bulunmuştur. Ancak Top.N ve Top.P giderim verimleri ikinci grupta yapılan deneysel çalışmalarda sırasıyla %97 ve %68, ve üçüncü grupta yapılan deneysel çalışmalarda sırasıyla %91 ve %51 olarak bulunmuştur. Birleşik sistemde yüksek besi maddesi giderim verimlerinin elde edilmesi sebebiyle, birleşik sistemin geliştirilmek üzere pilot ölçekte ve arazi şartlarında tekrar denenmesinin uygun olacağı sonucuna vanlmıştır.
In this study, an Upflow Sludge Blanket (USB) reactor, a Rotating Biological Contactor (RBC) reactor and a settling tank which are conventionally used wastewater treatment units were combined and adapted for biological nutrient removal from domestic wastewater. This combined system was installed in a 20°C±1 constant temperature room. Adaptation of this system for biological nutrient removal was firstly realized in this study. USB reactor used in the study was made of a plexiglas column having an effective liquid volume of 8.4 1 and equipped with gas-solid-liquid separator on the top. RBC unit consisted of 20 parallel circular discs made of plexiglas mounted 2 cm apart on a horizontal shaft and rotated perpendicular to the direction of the wastewater. The discs were 30 cm in diameter and 0.5 cm thick giving total surface area of 2.6 m2 for microbial growth and they were submerged in a 29.5 1 tank to about 33% of the disc diameter. Settling unit was made of a plexiglas column having an effective liquid volume of 3.91. Feeding solution was prepared synthetically in the domestic wastewater composition which has TOC concentration of 70 mg/1, TKN and TotN concentration of 19 mg/1 and TotP concentration of 14 mg/1 basically. Acetic acid was added into the feeding solution as an extra carbon source in some part of the experimental studies. After addition of acetic acid solution into the feeding solution, TOC value of the feeding solution raised from 70 mg/1 to 220 mg/1. In the combined system, feeding solution was fed into USB reactor by means of a pump. Effluent of USB reactor was transferred into the RBC reactor. Effluent of RBC reactor was given into settling tank. Settled sludge in the settling tank was recycled back into USB reactor by means of a pump. Supernatant of settling tank was discharged. Three sampling points were defined in the combined system; first one from feeding solution tank, second one from effluent line of USB reactor (in other words influent line of RBC reactor), and third one from effluent line of the combined system. Samples picked up from these points were analyzed for the parameters pH, TOC, TKN, NH4-N, NO3-N, NO2-N, PO4-P and TotP two times a week. Sampling from the influent of USB reactor was not possible. Therefore, concentration of TOC, NH4- XVII N, NO3-N, Tot.N, PO4-P and Tot.P parameters in the influent of USB reactor were calculated from material balance analysis. Dissolved Oxygen (D.O.) concentration was measured in the trough of RBC reactor two times a week in the days of sampling for analysis. MLSS and MLVSS analysis were made from the trough of RBC reactor and from sampling ports of USB reactor only once when the steady state conditions have been reached in the combined system. Experimental studies were carried out in three groups. In the first group of experiments, the effect of recycle ratio, which was the ratio of recycle flowrate from the bottom of the settling tank to USB reactor, to the influent flowrate of the combined system, on biological nutrient removal rate of the combined system were investigated. Feeding solution was prepared synthetically in the domestic wastewater composition. Acetic acid was added into the feeding solution as an extra carbon source. During the experimental studies, influent domestic wastewater flowrate applied to the combined system was arranged at 371/d. Hydraulic retention time was 5.4 h in USB reactor, 19.1 in RBC reactor and 2.5 h in the settling unit. Initially recycle flowrate from the bottom of settling tank to USB reactor was arranged at 47 1/d (giving recycle ratio of 1.3) and increased to 459 1/d (giving recycle ratio of 12.4) step by step after steady state conditions have been reached. TOC removal efficiency of the combined system didn't change with recycle ratio within the range of 1.3-12.4. TOC removal efficiency of the combined system was observed about 95% for all of the tried recycle ratios at 8.1 g/d TOC loading rate applied to the combined system. TKN removal efficiency was high in the combined system for all of the recycle ratios tried experimentally. TKN removal efficiency was observed in the range of 96-99% at 0.7 g/d constant TKN loading rate applied to the combined system. TKN removal in USB reactor was negligible and TKN and NH4-N removal realized only in RBC reactor. TotN removal in the combined system realized only in USB reactor for all of the tried recycle ratios. When the recycle ratio was increased from 1.3 to 12.4, Tot.N removal efficiency in the combined system increased from 61% to 81% at 0.7 g/d constant Tot.N loading rate applied to the combined system. TotP removal realized only in RBC reactor. When the recycle ratio was increased from 1.3 to 12.4, TotP removal efficiency increased from 18% to 39% at 0.52 g/d constant Tot-P loading rate applied to the combined system. In the first group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 89000-100000 mg and 68000-79000 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 45200-68600 mg and 33700-49600 mg, respectively. Dissolved oxygen concentration in the trough of RBC reactor was in the range of 4.5-5.9 mg/1. pH values was in the range of 5.4-6.6 in the xvui feeding solution, 6.4-7 in the effluent of USB reactor (in other words, in the influent of RBC reactor), and 6.3-7.2 in the effluent of the combined system. In the second group of experiments, biological nutrient removal rate of the combined system were investigated at higher hydraulic loading rates applied to the combined system than first group of experiments. Feeding solution was prepared in the same composition used in the first group of experimental studies. During the experimental studies, influent wastewater flowrate given to the combined system was increased step by step from 37 1/d to 93.5 1/d after steady state conditions have been existed in the combined system. Hydraulic retention times decreased from 5.4 h to 2.2 h in USB reactor, from 19.1 h to 7.6 h in RBC reactor and from 2.5 to 1 h in the settling unit. Recycle flowrate from the bottom of settling tank to USB reactor was arranged initially at 307 1/d giving initial recycle ratio of 8.3 which was observed as optimum for biological nutrient removal in the first group of experimental studies. When the influent flowrate of the combined system was increased step by step to 93.5 1/d, recycle ratio decreased from 8.3 to 3.9. When the TOC loading rate applied to the combined system was increased from 8.1 g/d to 20.6 g/d, TOC removal efficiency changed in the range of 96-97%. TOC removal was observed in both of the USB and RBC reactors. When TKN loading rate applied to the combined system was increased from 0.7 g/d to 1.78 g/d, TKN removal efficiency in the combined system changed in the range of 95-98%. TKN removal rate in the combined system was obtained as 1.74 g/d of which 0.5 g/d removed in USB reactor and 1.24 g/d removed in RBC reactor at 1.78 g/d maximum TKN loading rate applied to the combined system. When Tot.N loading rate applied to the combined system was increased from 0.7 g/d to 1.78 g/d, Tot.N removal efficiency increased 82% to 97%. Tot.N removal realized only at USB reactor up to 1.08 g/d TotN loading rate and it realized also in RBC reactor at higher TotN loading rates. TotP removal in the combined system was observed only in RBC reactor. When TotP loading rate applied to the combined system was increased from 0.52 g/d to 1.31 g/d, Tot.P removal efficiency in the combined system increased from 18% to 91%. In the second group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 86300-100000 mg and 66400-75200 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 35600-68200 mg and 26100-50300 mg, respectively. When the influent flowrate of the combined system was increased from 37 1/d to 93.5 1/d, dissolved oxygen concentration in the trough of RBC reactor decreased from 4.5-5.5 mg/1 level to 2.9-3.3 mg/1 level. pH values was in the range of 5.4-6.1 in the feeding solution, 5.7-6.8 in the effluent of USB reactor (in other words, in the influent of RBC reactor), and 6.5-6.9 in the effluent of the combined system. xix In the third group of experiments, acetic acid was not added into the domestic wastewater solution as an extra carbon source. Feeding solution was prepared at the domestic wastewater composition. Influent flowrate applied to the combined system was initially arranged at 70 1/d and increased step by step up to 260 1/d when the steady state conditions in the combined system have been reached. Hydraulic retention time decreased from 2.9 h to 0.8 h in USB reactor, from 10.1 to 2.7 h in RBC reactor and from 1.3 to 0.4 h in the settling unit. Recycle flowrate from settling tank to USB reactor was arranged initially at 225 1/d giving recycle ratio of 3.2. which was near to the optimum recycle ratio (3.9) for biological nutrient removal in the second group of experimental studies. When the influent flowrate of the combined system was increased step by step from 70 1/d to 260 1/d, recycle ratio decreased from 3.2 to 1.4. When the TOC loading rate applied to the combined system was increased from 4.9 g/d to 18.2 g/d, TOC removal efficiency in the combined system changed in the range of 87- 93%. Total TOC removal rate in the combined system was observed as 16.4 g/d of which 12.9 g/d was observed in USB reactor and 3.5 g/d was observed in RBC reactor at 18.2 g/d maximum TOC loading rate applied to the combined system. TKN removal efficiency in the combined system was quite high up to 3.4 g/d TKN loading rate in the combined system and it changed in the range of 95-98%. TKN removal efficiency in the combined system decreased to %88.4 at 4.9 g/d maximum TKN loading rate applied to the combined system. TKN removal rate was obtained as 0.45 g/d in USB reactor and 3.92 g/d in RBC reactor at 4.94 g/d maximum TKN loading rate applied to the combined system. When the Tot.N loading rate applied to the combined system was increased from 1.33 g/d to 4.94 g/d, Tot.N removal efficiency in the combined system decreased from 68% to 53%. Maximum Tot.N removal rate in the combined system was 2.6 g/d of which 2.1 g/d realized in USB reactor and 0.5 g/d realized in RBC reactor at 4.9 g/d maximum Tot.N loading rate applied to the combined system. Tot.P removal rate in the combined system changed in the range of 0.39-0.69 g/d up to 3 g/d TotP loading rate applied to the combined system and it decreased rapidly at higher TotP loading rates than 3 g/d. On the other hand, Tot.P removal efficiency decreased continuously with Tot.P loading rate applied to the combined system. When the Tot.P loading rate applied to the combined system was increased from 1 g/d to 3.6 g/d, Tot.P removal efficiency in the combined system decreased from 51% to 1%. In the third group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 62900-83900 mg and 49600-66000 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 40900-77000 mg and 30000-56500 mg, respectively. When the influent flowrate of the combined system was increased from 70 1/d to 260 1/d, dissolved oxygen concentration in the trough of RBC reactor decreased from 6.2-7.1 mg/1 level to 3.5-4.1 mg/1 level. pH values was in the range of 6-7.4 in the feeding solution, 6.6-7.4 in the effluent of USB reactor (in xx other words, in the influent of RBC reactor), and 7-7.6 in the effluent of the combined system. Main results of this study is given below;. TOC and TKN removal efficiencies in the combined system were quite high in all of the operational conditions applied to the three groups of experiments. Tot.N and Tot.P removal efficiencies were the indicators for the selection of the optimum experimental conditions in the combined system.. Total hydraulic retention time (THRT), which was the sum of the hydraulic retention times of USB reactor, RBC reactor and the settling tank in the combined system, was an important parameter for biological nutrient removal efficiency in the combined system. Selection of an optimum recycle ratio for an effective biological nutrient removal in the combined system was closely related with THRT in the combined system. In the first group of experiments, maximum Tot.N and Tot.P removal efficiencies were obtained about 84% and 39% between recycle ratios of 6 and 12.4 respectively at 27 h constant THRT in the combined system. However, when the THRT decreased from 27 h to 11 h in the second group of experiments; recycle ratio also decreased from 8.3 to 3.9, Tot.N removal efficiency increased from 84% to 97%, and TotP removal efficiency increased from 39% to 91%.. Besides THRT, TOC/N/P ratios in the feeding solution was also an important parameter for achievement of excellent biological nutrient removal efficiency in the combined system. TOC/N/P ratios in the feeding solutions were 15.7/1.3/1 in the second and 5/1.3/1 in the third groups of experiments. Optimum recycle ratios and THRTs were found as 3.9 and 11 h in the second, and 3.2 and 14 h in the third groups of experiments. However, Tot.N removal efficiencies were 97% and 68% and TotP removal efficiencies were 91% and 51% at the same recycle ratios in the first and the second groups of experiments, respectively. Achievement of excellent biological nutrient removal efficiencies in the combined system indicated that this combined system is promising for future development in pilot scale with real domestic wastewater.
In this study, an Upflow Sludge Blanket (USB) reactor, a Rotating Biological Contactor (RBC) reactor and a settling tank which are conventionally used wastewater treatment units were combined and adapted for biological nutrient removal from domestic wastewater. This combined system was installed in a 20°C±1 constant temperature room. Adaptation of this system for biological nutrient removal was firstly realized in this study. USB reactor used in the study was made of a plexiglas column having an effective liquid volume of 8.4 1 and equipped with gas-solid-liquid separator on the top. RBC unit consisted of 20 parallel circular discs made of plexiglas mounted 2 cm apart on a horizontal shaft and rotated perpendicular to the direction of the wastewater. The discs were 30 cm in diameter and 0.5 cm thick giving total surface area of 2.6 m2 for microbial growth and they were submerged in a 29.5 1 tank to about 33% of the disc diameter. Settling unit was made of a plexiglas column having an effective liquid volume of 3.91. Feeding solution was prepared synthetically in the domestic wastewater composition which has TOC concentration of 70 mg/1, TKN and TotN concentration of 19 mg/1 and TotP concentration of 14 mg/1 basically. Acetic acid was added into the feeding solution as an extra carbon source in some part of the experimental studies. After addition of acetic acid solution into the feeding solution, TOC value of the feeding solution raised from 70 mg/1 to 220 mg/1. In the combined system, feeding solution was fed into USB reactor by means of a pump. Effluent of USB reactor was transferred into the RBC reactor. Effluent of RBC reactor was given into settling tank. Settled sludge in the settling tank was recycled back into USB reactor by means of a pump. Supernatant of settling tank was discharged. Three sampling points were defined in the combined system; first one from feeding solution tank, second one from effluent line of USB reactor (in other words influent line of RBC reactor), and third one from effluent line of the combined system. Samples picked up from these points were analyzed for the parameters pH, TOC, TKN, NH4-N, NO3-N, NO2-N, PO4-P and TotP two times a week. Sampling from the influent of USB reactor was not possible. Therefore, concentration of TOC, NH4- XVII N, NO3-N, Tot.N, PO4-P and Tot.P parameters in the influent of USB reactor were calculated from material balance analysis. Dissolved Oxygen (D.O.) concentration was measured in the trough of RBC reactor two times a week in the days of sampling for analysis. MLSS and MLVSS analysis were made from the trough of RBC reactor and from sampling ports of USB reactor only once when the steady state conditions have been reached in the combined system. Experimental studies were carried out in three groups. In the first group of experiments, the effect of recycle ratio, which was the ratio of recycle flowrate from the bottom of the settling tank to USB reactor, to the influent flowrate of the combined system, on biological nutrient removal rate of the combined system were investigated. Feeding solution was prepared synthetically in the domestic wastewater composition. Acetic acid was added into the feeding solution as an extra carbon source. During the experimental studies, influent domestic wastewater flowrate applied to the combined system was arranged at 371/d. Hydraulic retention time was 5.4 h in USB reactor, 19.1 in RBC reactor and 2.5 h in the settling unit. Initially recycle flowrate from the bottom of settling tank to USB reactor was arranged at 47 1/d (giving recycle ratio of 1.3) and increased to 459 1/d (giving recycle ratio of 12.4) step by step after steady state conditions have been reached. TOC removal efficiency of the combined system didn't change with recycle ratio within the range of 1.3-12.4. TOC removal efficiency of the combined system was observed about 95% for all of the tried recycle ratios at 8.1 g/d TOC loading rate applied to the combined system. TKN removal efficiency was high in the combined system for all of the recycle ratios tried experimentally. TKN removal efficiency was observed in the range of 96-99% at 0.7 g/d constant TKN loading rate applied to the combined system. TKN removal in USB reactor was negligible and TKN and NH4-N removal realized only in RBC reactor. TotN removal in the combined system realized only in USB reactor for all of the tried recycle ratios. When the recycle ratio was increased from 1.3 to 12.4, Tot.N removal efficiency in the combined system increased from 61% to 81% at 0.7 g/d constant Tot.N loading rate applied to the combined system. TotP removal realized only in RBC reactor. When the recycle ratio was increased from 1.3 to 12.4, TotP removal efficiency increased from 18% to 39% at 0.52 g/d constant Tot-P loading rate applied to the combined system. In the first group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 89000-100000 mg and 68000-79000 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 45200-68600 mg and 33700-49600 mg, respectively. Dissolved oxygen concentration in the trough of RBC reactor was in the range of 4.5-5.9 mg/1. pH values was in the range of 5.4-6.6 in the xvui feeding solution, 6.4-7 in the effluent of USB reactor (in other words, in the influent of RBC reactor), and 6.3-7.2 in the effluent of the combined system. In the second group of experiments, biological nutrient removal rate of the combined system were investigated at higher hydraulic loading rates applied to the combined system than first group of experiments. Feeding solution was prepared in the same composition used in the first group of experimental studies. During the experimental studies, influent wastewater flowrate given to the combined system was increased step by step from 37 1/d to 93.5 1/d after steady state conditions have been existed in the combined system. Hydraulic retention times decreased from 5.4 h to 2.2 h in USB reactor, from 19.1 h to 7.6 h in RBC reactor and from 2.5 to 1 h in the settling unit. Recycle flowrate from the bottom of settling tank to USB reactor was arranged initially at 307 1/d giving initial recycle ratio of 8.3 which was observed as optimum for biological nutrient removal in the first group of experimental studies. When the influent flowrate of the combined system was increased step by step to 93.5 1/d, recycle ratio decreased from 8.3 to 3.9. When the TOC loading rate applied to the combined system was increased from 8.1 g/d to 20.6 g/d, TOC removal efficiency changed in the range of 96-97%. TOC removal was observed in both of the USB and RBC reactors. When TKN loading rate applied to the combined system was increased from 0.7 g/d to 1.78 g/d, TKN removal efficiency in the combined system changed in the range of 95-98%. TKN removal rate in the combined system was obtained as 1.74 g/d of which 0.5 g/d removed in USB reactor and 1.24 g/d removed in RBC reactor at 1.78 g/d maximum TKN loading rate applied to the combined system. When Tot.N loading rate applied to the combined system was increased from 0.7 g/d to 1.78 g/d, Tot.N removal efficiency increased 82% to 97%. Tot.N removal realized only at USB reactor up to 1.08 g/d TotN loading rate and it realized also in RBC reactor at higher TotN loading rates. TotP removal in the combined system was observed only in RBC reactor. When TotP loading rate applied to the combined system was increased from 0.52 g/d to 1.31 g/d, Tot.P removal efficiency in the combined system increased from 18% to 91%. In the second group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 86300-100000 mg and 66400-75200 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 35600-68200 mg and 26100-50300 mg, respectively. When the influent flowrate of the combined system was increased from 37 1/d to 93.5 1/d, dissolved oxygen concentration in the trough of RBC reactor decreased from 4.5-5.5 mg/1 level to 2.9-3.3 mg/1 level. pH values was in the range of 5.4-6.1 in the feeding solution, 5.7-6.8 in the effluent of USB reactor (in other words, in the influent of RBC reactor), and 6.5-6.9 in the effluent of the combined system. xix In the third group of experiments, acetic acid was not added into the domestic wastewater solution as an extra carbon source. Feeding solution was prepared at the domestic wastewater composition. Influent flowrate applied to the combined system was initially arranged at 70 1/d and increased step by step up to 260 1/d when the steady state conditions in the combined system have been reached. Hydraulic retention time decreased from 2.9 h to 0.8 h in USB reactor, from 10.1 to 2.7 h in RBC reactor and from 1.3 to 0.4 h in the settling unit. Recycle flowrate from settling tank to USB reactor was arranged initially at 225 1/d giving recycle ratio of 3.2. which was near to the optimum recycle ratio (3.9) for biological nutrient removal in the second group of experimental studies. When the influent flowrate of the combined system was increased step by step from 70 1/d to 260 1/d, recycle ratio decreased from 3.2 to 1.4. When the TOC loading rate applied to the combined system was increased from 4.9 g/d to 18.2 g/d, TOC removal efficiency in the combined system changed in the range of 87- 93%. Total TOC removal rate in the combined system was observed as 16.4 g/d of which 12.9 g/d was observed in USB reactor and 3.5 g/d was observed in RBC reactor at 18.2 g/d maximum TOC loading rate applied to the combined system. TKN removal efficiency in the combined system was quite high up to 3.4 g/d TKN loading rate in the combined system and it changed in the range of 95-98%. TKN removal efficiency in the combined system decreased to %88.4 at 4.9 g/d maximum TKN loading rate applied to the combined system. TKN removal rate was obtained as 0.45 g/d in USB reactor and 3.92 g/d in RBC reactor at 4.94 g/d maximum TKN loading rate applied to the combined system. When the Tot.N loading rate applied to the combined system was increased from 1.33 g/d to 4.94 g/d, Tot.N removal efficiency in the combined system decreased from 68% to 53%. Maximum Tot.N removal rate in the combined system was 2.6 g/d of which 2.1 g/d realized in USB reactor and 0.5 g/d realized in RBC reactor at 4.9 g/d maximum Tot.N loading rate applied to the combined system. Tot.P removal rate in the combined system changed in the range of 0.39-0.69 g/d up to 3 g/d TotP loading rate applied to the combined system and it decreased rapidly at higher TotP loading rates than 3 g/d. On the other hand, Tot.P removal efficiency decreased continuously with Tot.P loading rate applied to the combined system. When the Tot.P loading rate applied to the combined system was increased from 1 g/d to 3.6 g/d, Tot.P removal efficiency in the combined system decreased from 51% to 1%. In the third group of experiments, total mass of suspended solids and total mass of volatile suspended solids in USB reactor was in the range of 62900-83900 mg and 49600-66000 mg, respectively. Total mass of suspended solids and total mass of volatile suspended solids in RBC reactor was in the range of 40900-77000 mg and 30000-56500 mg, respectively. When the influent flowrate of the combined system was increased from 70 1/d to 260 1/d, dissolved oxygen concentration in the trough of RBC reactor decreased from 6.2-7.1 mg/1 level to 3.5-4.1 mg/1 level. pH values was in the range of 6-7.4 in the feeding solution, 6.6-7.4 in the effluent of USB reactor (in xx other words, in the influent of RBC reactor), and 7-7.6 in the effluent of the combined system. Main results of this study is given below;. TOC and TKN removal efficiencies in the combined system were quite high in all of the operational conditions applied to the three groups of experiments. Tot.N and Tot.P removal efficiencies were the indicators for the selection of the optimum experimental conditions in the combined system.. Total hydraulic retention time (THRT), which was the sum of the hydraulic retention times of USB reactor, RBC reactor and the settling tank in the combined system, was an important parameter for biological nutrient removal efficiency in the combined system. Selection of an optimum recycle ratio for an effective biological nutrient removal in the combined system was closely related with THRT in the combined system. In the first group of experiments, maximum Tot.N and Tot.P removal efficiencies were obtained about 84% and 39% between recycle ratios of 6 and 12.4 respectively at 27 h constant THRT in the combined system. However, when the THRT decreased from 27 h to 11 h in the second group of experiments; recycle ratio also decreased from 8.3 to 3.9, Tot.N removal efficiency increased from 84% to 97%, and TotP removal efficiency increased from 39% to 91%.. Besides THRT, TOC/N/P ratios in the feeding solution was also an important parameter for achievement of excellent biological nutrient removal efficiency in the combined system. TOC/N/P ratios in the feeding solutions were 15.7/1.3/1 in the second and 5/1.3/1 in the third groups of experiments. Optimum recycle ratios and THRTs were found as 3.9 and 11 h in the second, and 3.2 and 14 h in the third groups of experiments. However, Tot.N removal efficiencies were 97% and 68% and TotP removal efficiencies were 91% and 51% at the same recycle ratios in the first and the second groups of experiments, respectively. Achievement of excellent biological nutrient removal efficiencies in the combined system indicated that this combined system is promising for future development in pilot scale with real domestic wastewater.
Açıklama
Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2000
Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2000
Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2000
Anahtar kelimeler
Atık su arıtma,
Azot,
Fosfor,
Reaktörler,
Çamur yatağı,
Çöktürme,
Waste water treatment,
Nitrogen,
Phosphorus,
Reactors,
Sludge blanket,
Percipitation