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This study presents findings of a modeling work in which the effects of internal recycle (IR) and return activated sludge (RAS) ratios on the treatment performance of an A²O process were investigated. Simulations were performed using activated sludge model no.3 extended with biological phosphorus removal processes at an influent wastewater temperature of 20°C. The results showed that not only IR ratio but also RAS ratio affects both nitrogen and phosphorus removal processes. The removal efficiencies for total nitrogen (TN) and total phosphorus (TP) changed between 71%–83% and 53%–80%, respectively, at different IR and RAS ratios. On the other hand, chemical oxygen demand (COD), total Kjeldahl Nitrogen (TKN), and total suspended solids (TSS) removal efficiencies stayed relatively constant at around 90%, 96%, and 93%, respectively, with varying IR and RAS ratios. Results indicated that an optimum set of IR and RAS ratios can be found out by activated sludge modeling. For A²O process, an IR ratio of 2.5 to 3.5 at a RAS ratio of 0.75 to 0.90 offer the best performance in terms of both TN and TP removal efficiencies.

This paper presents the implementation of an MS Excel tool for backpropagation neural networks in environmental engineering education. A number of test cases, Darcy friction factor and oxygen solubility, were also provided to test the performance of the tool. Relative mean square errors and coefficients of determination for Darcy friction factor were calculated as 1.53*10-3±0.59*10-3 and 0.9983±0.0003 while they were calculated as 4.78*10-4±2.33*10-4 and 0.9998±0.0000 for oxygen solubility. Results suggested that the tool’s performance is satisfactory. The tool produces satisfactorily fast and reliable results and can be used for environmental education in undergraduate/graduate level.

This paper presents the implementation of an MS Excel tool for parameter optimization in environmental engineering education. Visual Basic for Applications v7.0 were used for implementation of the program. A number of test cases were also provided to test the performance of the tool including the fields of air pollution control, water treatment, and anaerobic treatment. For each test case, calculated coefficients of determination were 0.98 and above. Results suggested that the MS Excel tool produces satisfactorily fast and reliable results, and can be used confidently for optimization works in environmental studies.

In this study a laboratory-scale slow sand filter (SSF) is used for removal of iron and manganese and the effects of various inlet concentrations on removal efficiency were investigated. SSF was operated at a filtration rate of 0.2 m.h-1 with two different synthetic inlet waters (Run1 and Run2). Iron and manganese concentrations in two runs were 1.09±0.13mg.L-1–1.06±0.10 mg.L-1 for Run1 and 2.02±0.15 mg.L-1–2.10±0.14 mg.L-1 for Run2. In Run1, the removal efficiencies of 96.3±2.48%, 92.3±6.1%, 92.6±5.7%, and 55.3±8.3% were obtained for turbidity, iron, manganese and total organic carbon (TOC), respectively. In Run2, on the other hand, the removal efficiencies were obtained as 97.9±1.3%, 93.1±8.1%, 94.4±5.8%, and 55.5±6.8%, respectively. Results suggested that the SSF was the most efficient in turbidity removal at a filtration rate of 0.2 m.h-1. Sequence analyses of DGGE bands from Run1 and Run2 were also performed and results indicated that a range of bacteria were present, with 16S rRNA gene sequences similar to groups such as Gallionella, Leptothrix, Crenothrix, and an uncharacterized environmental clone.

This paper presents the results of a study in which a pilot scale five-stage biological nutrient removal system with an active volume of 8.6 m3 was operated with two different processes to remove carbon and nutrients from domestic wastewaters. During the application of both processes, hydraulic retention time was 16.08 hours, MLSS concentration was between 4500 and 5500 mg/L, and sludge age was about 15 days. The sludge volume index (SVI) ranged from 50 to 150 mL/g. Both processes were evaluated in the aspect of their performances for COD, TKN, NH4-N, TP, PO4-P, SS, and VSS removal efficiencies. The removal efficiencies for the first process, which is a new process (A – Modified Five-Stage Bardenpho process), were 86.5%, 85.5%, 92.7%, 88.9%, 88.1%, 93.7%, and 93.5%, respectively for COD, TKN, NH4-N, TP, PO4-P, SS, and VSS, while the removal efficiencies were 86.7%, 84.0%, 92.5%, 89.5%, 87.5%, 94.8%, and 95.0%, respectively, for the second process (B – Two- Stage, Cascade Biological Nutrient Removal process). The results suggested that both processes are suitable for carbon and nutrient removal from domestic wastewaters and they can be employed in full-scale treatment plants.

Dünya nüfusunun günden güne artmasına bağlı olarak oluşan atıksu miktarı da artış göstermekte ve bu durum atıksuların arıtılması maksadıyla daha ekonomik ve çevre dostu sistemlerin geliştirilmesi ihtiyacını ortaya çıkarmaktadır.Bu çalışmada evsel atıksuların arıtılması maksadıyla İSKİ Ataköy İleri Biyolojik Atıksu Arıtma Tesisi'nde bulunan 8,6 m3 hacimli 10 m3/gün kapasiteli pilot ölçekli biyolojik atıksu arıtma prosesi kullanılmış olup, çalışmada yeni geliştirilen Modifiye Beş Kademeli Bardenpho Prosesi ve İki Kademeli Kaskat Beslemeli Biyolojik Nütrient Giderim Prosesi olmak üzere iki farklı prosesin arıtma performansı ve işletme sürecinde sistemlerdekimikroorganizma tipleri ortaya konmuştur.Bu maksatla çalışmada ilk aşamada KOİ, TKN, NH4-N, NO2-N, NO3-N, TP, PO4-P ve AKM konsantrasyonları sırasıyla 645±115 mg/L; 79±13 mg/L; 52±9 mg/L; 0,04±0,03 mg/L; 0,11±0,10 mg/L; 7,9±0,8 mg/L; 3,4±0,7 mg/L ve 321±156 mg/L olan gerçek evsel atıksukullanılmış ve geri devir oranı %80 olan yeni geliştirilen Modifiye Beş Kademeli Bardenpho Prosesi kullanılarak biyolojik olarak arıtımı incelenmiştir. Çalışma sonucunda yeni geliştirilen Modifiye Beş Kademeli Bardenpho Prosesi'nde tüm işletme süresince elde edilen ortalama KOİ, TKN, NH4-N, TP, PO4-P ve AKM giderim verimleri sırasıyla %76; %63; %68; %80; %72 ve %80 olarak belirlenmiştir. Ancak çalışmada sekizinci haftadan sonra kararlı duruma ulaşılmış ve bu haftadan sonra elde edilenanaliz neticelerine göre giderim verimleri değerlendirilmiştir. Bu durumda kararlı hal durumunda KOİ, TKN, NH4-N, TP, PO4-P ve AKM için ortalama giderim verimleri sırasıyla%87; %86; %93; %89; %88 ve %94 olarak tespit edilmiştir. Yeni geliştirilen Modifiye Beş Kademeli Bardenpho Prosesi'nin uygulandığı ilk aşamada mikrobiyal tür analizleri degerçekleştirilmiş olup, kararlı hal için arıtımdan sorumlu bakteriler olarak Nitrosomonas, Nitrosospira, Accumulibacter, Dechloromonas, Firmicutes cinslerine ait türler ve diğer tanımlanmamış türler belirlenmiştir.İkinci aşamada iki Kademeli Kaskat Nütrient Giderme Prosesi çalışmalarına geçilmiş olup; bu aşamada giriş atıksuyu (10 m3/gün) ikiye bölünerek %50'si (~5 m3/gün) bio-P ünitesine, %50'si (~5 m3/gün) ise denitrifikasyon2 ünitesine beslenmiştir. Çalışma parametrelerinin değiştirilmediği bu aşamada giriş KOİ, TKN, NH4-N, NO2-N, NO3-N, TP, PO4-P ve AKM konsantrasyonları sırasıyla 555±60 mg/L; 72±7 mg/L; 44±7 mg/L; 0,03±0,02 mg/L; 0,06±0,04 mg/L; 8,1±0,4 mg/L; 4,0±0,5 mg/L ve 316±47 mg/Lözelliğinde evsel atıksu kullanılmıştır. Prosesin iki Kademeli Kaskat Nütrient Giderme Prosesi şeklinde işletilmesi sonucunda KOİ, TKN, NH4-N, TP, PO4-P ve AKM için elde edilen giderim verimleri sırasıyla %87; %84; %93; %90; %88 ve %95 olarakbelirlenmiştir. Çalışmanın bu aşamasında da mikrobiyal tür analizleri gerçekleştirilmiştir. Arıtımdan sorumlu bakteriler olarak Nitrosomonas, Nitrosospira, Accumulibacter, Dechloromonas ve diğer tanımlanmamış türler tespit edilmiştir.Her iki proses için elde edilen verimler ve işletme koşulları dikkate alındığında yeni geliştirilen Modifiye Beş Kademeli Bardenpho Prosesi'nin orta kuvvetli atıksular için daha uygun olacağı ortaya konmuştur. Diğer taraftan literatürde çoğunluklalaboratuvar ölçekli çalışmaların bulunması sebebiyle, çalışmanın literatüre önemli bir katkı sağlayacağı düşünülmüştür. Gradual increase in world?s population has lead to increase in wastewater generationrates, which, in turn, brings the necessity of development of treatment systems thatare more cost-efficient and more environmentally friendly.This study focuses on the use of a pilot-scale biological treatment process of totalvolume 8.6 m3 and capacity 10 m3.d-1 installed within the ISKI Ataköy AdvancedBiological Wastewater Treatment Plant. Two different processes, one being the newlydevelopedModified five-stage Bardenpho process and the other one being two-stagecascade-feed biological nutrient removal process, were evaluated in the aspect theirtreatment performances. Besides, microorganism speciation was done during theoperating period for each process.In the first stage of the study, the treatment of the domestic wastewater with COD =645±115 mg.L-1, TKN = 79±13 mg.L-1, NH4-N = 52±9 mg.L-1, NO2-N = 0.04±0.03 mg.L-1,NO3-N = 0.11±0.10 mg.L-1, TP = 7.9±0.8 mg.L-1, PO4-P = 3.4±0.7 mg.L-1, and SS =321±156 mg.L-1, by newly-developed Modified five-stage Bardenpho process with arecycle ratio of 80% was investigated. The average treatment efficiencies for COD,TKN, NH4-N, TP, PO4-P, and SS by the newly developed process during the whole studyperiod were 76%, 63%, 68%, 80%, 72%, and 80%, respectively. The results showed thatthe system has reached steady-state conditions after 8 weeks of operation. Understeady-state conditions, the treatment efficiencies were calculated as 87%, 86%, 93%,89%, 88%, and 94%, respectively. Microbial speciation was also done during the whole period, the results of which suggested that Nitrosomonas, Nitrosospira,Accumulibacter, Dechloromonas, Firmicutes, and some other uncultured genus wereresponsible for the treatment during the steady-state conditions.In the second stage, the process was converted into a Two-Stage Cascade-FeedBiological Nutrient Removal Process by feeding fifty percent of the inlet wastewater (5m3.d-1) to the bio-P unit, and the rest (5 m3.d-1) to the denitrification2 unit by keepingall other operational parameters constant. Average wastewater characterizationduring this stage of the study COD = 555±60 mg.L-1, TKN = 72±7 mg.L-1, NH4-N = 44±7mg.L-1, NO2-N = 0.03±0.02 mg.L-1, NO3-N = 0.06±0.04 mg.L-1, TP = 8.1±0.4 mg.L-1, PO4-P= 4.0±0.5 mg.L-1, and SS = 316±47 mg.L-1. The treatment efficiencies for COD, TKN, NH4-N, TP, PO4-P, and SS were calculated as 87%, 84%, 93%, 90%, 88%, and 95%,respectively. It was determined that the microorganisms responsible for the treatmentin this Two-Stage Cascade-Feed Biological Nutrient Removal Process wereNitrosomonas, Nitrosospira, Accumulibacter, Dechloromonas, and some otheruncultured genus.Comparing the treatment performances of and operational conditions for bothprocesses, newly-developed Modified five-stage Bardenpho Process would be a betterselection for medium-strength domestic wastewaters. On the other hand, this study isto contribute much to the current literature considering the fact that literature data iscomposed mostly of lab-scale studies. 145

Bu çalışmada yeraltı sularından demir ve mangan gidermek maksadıyla laboratuvar ölçekli yavaş kum filtresi kullanılmıştır. Çalışmada farklı filtrasyon hızlarının ve farklı demir-mangan konsantrasyonlarının filtre verimine etkisi araştırılmıştır. Laboratuvar ölçekli yavaş kum filtresi sistemi, 40 cm x 60 cm x 50 cm boyutlarında iki adet paralel filtreden oluşmaktadır. Filtrenin işletilmesi süresince yük kayıplarını tespit etmek maksadıyla farklı derinliklerde manometreler kullanılmıştır. Ayrıca her işletme şartında etkin türlerin tespiti için mikrobiyal tür analizi yapılmış olup bu analiz için her işletme şartında farklı derinliklerde numuneler alınmıştır . Yavaş kum filtresinde uygulanan işletme şartları sırasıyla şu şekildedir: YKF1: 1 mg/L demir- mangan ve 0,1 m/sa, YKF2: 2 mg/L demir-mangan ve 0,1 m/sa, YKF3: 1mg/L demir mangan ve 0,2 m/sa, YKF4: 2 mg/L demir-mangan ve 0,2 m/sa YKF5: 1 mg/L demir-mangan ve 0,3 m/sa, YKF6: 2 mg/L demir-mangan ve 0,3 m/sa. İşletme süresince YKF1, YKF2, YKF3, YKF4, YKF5 ve YKF6 için belirlenen ortalama bulanıklık giderim verimleri sırasıyla %94,8±2,8, %95,9±2,6, %96,3±2,4, %97,9±1,3, %97,7±0,8 ve %98,2±0,8'dIr. İşletme süresince YKF1, YKF2, YKF3, YKF4, YKF5 ve YKF6 için tespit edilen ortalama demir giderim verimleri sırasıyla %90,4±4,8, %94,4±3,2, %92,3±6,1, %93,1±8,1 %93,4±4,4 ve %95,4±4,8'dir. İşletme süresince YKF1, YKF2, YKF3, YKF4, YKF5 ve YKF6 için belirlenen ortalama mangan giderim verimleri ise sırasıyla %90,3±5,8, %95,4±5,2, %92,7±5,7, %94,3±5,7 %94,9±6,1 ve %95,9±3,5'dir. İşletme süresince YKF1, YKF2, YKF3, YKF4, YKF5 ve YKF6 için tespit edilen ortalama toplam organik karbon giderim verimleri sırasıyla %52,3±3,6, %49,3±5,8, %55,3±8,3, %55,5±6,8 %52,0±4,8 ve %57,6±8,2'dir. Çalışmada her işletme şartı için etkin mikrobiyal türler; Gallionella sp., Leptothrix sp., Crenothrix sp. ve Hyphomicrobium sp. olarak bulunmuştur. In this study, a laboratory-scale slow sand filter was used to remove iron and manganese from ground waters. The effects of different filtration rates and different iron-manganese concentrations on the filtration efficiency were investigated. The laboratory-scale slow sand filter with 40x60x50 cm dimensions composed of two filter units in parallel. Headloss through the filters was measured by several manometers at various depths of the filter units. In addition, microbial species analysis was carried out to determine the active species and samples were taken at different depths in each operating conditions. Operating conditions in experimental study includes: SSF1: 1 mg/L Fe-Mn at 0.1 m/h, SSF2: 2 mg/L Fe-Mn at 0.1 m/h, SSF3: 1 mg/L Fe-Mn at 0.2 m/h, SSF4: 2 mg/L Fe-Mn at 0.2 m/h, SSF5: 1 mg/L Fe-Mn at 0.3 m/h, SSF6: 2 mg/L Fe-Mn at 0.3 m/h. Average turbidity removal efficiencies in SSF1, SSF2, SSF3, SSF4, SSF5, and SSF6 were 94.8±2.8%, 95.9±2.6%, 96.3±2.4%, 97.9±1.3%, 97.7±0.8% and 98.2±0.8%, respectively. On the other hand, iron removal efficiencies were 90.4±4.8%, 94.4±3.2%, 92.3±6.1%, 93.1±8.1%, 93.4±4.4% and 95.4±4.8%, while manganese removal efficiencies were 90.3±5.8%, 95.4±5.2%, 92.7±5.7%, 94.3±5.7%, 94.9±6.1% and 95.9±3.5%, respectively. Average total organic carbon removal efficiencies in SSF1, SSF2, SSF3, SSF4, SSF5, and SSF6 were 52.3±3.6%, 49.3±5.8%, 55.3±8.3%, 55.5±6.8%, 52.0±4.8% and 57.6±8.2%, respectively. Effective microbial species for each operating condition in the study; Gallionella sp., Leptothrix sp., Crenothrix sp. and Hypochondrium sp. was found. 121