The effect of temperature and sludge age on COD removal and nitrification in a moving bed sequencing batch reactor

This study investigates the effect of temperature and the sludge age on the performance of a moving bed sequencing batch biofilm reactor (MBSBBR) for COD removal and nitrification. The experiments are conducted in a lab-scale MBSBBR operated at three different temperatures (20, 15 and 10 8C) with a synthetic feed simulating domestic sewage characteristics. Evaluation of the results revealed that removal of organic matter at high rates and with efficiencies over 90% was secured at all operation conditions applied. The nitrification rate was significantly influenced by changes in temperature but complete nitrification occurred at each temperature. The nitrification rates observed at 20 and 15 8C were very close (0.241 mg NOX-N/m2 d, 0.252 mg NOX-N/m2 d, respectively), but at 10 8C, it decreased to 0.178 mg NOX-N/m2 d. On the other hand, the biomass concentration and sludge age increased while the VSS/TSS ratios that can be accepted as an indicator of active biomass fraction decreased with time. It is considered that, increasing biofilm thickness and diffusion limitation affected the treatment efficiency, especially nitrification rate, negatively.TÜBİTAK - YDABCAG-199Y11

Mikrobiyel yakıt hücresinde Shewanella putrefaciens tarafından organik atıklardan elektrik üretimi

A microbial fuel cell (MFC) is a bioreactor that converts chemical energy in the chemical bonds in organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. Typical two chambered MFC systems are consist of conductive anode (such as carbon cloth or carbon paper) and cathode material (with platinum), proton exchange membrane (PEM), anolyte and catholyte, external conductive wire, and digital multimeter system and computer. In a MFC, power can be generated from the oxidation of organic matter by bacteria at the anode, with reduction of oxygen at the cathode. Anodic and cathodic chambers partitioned by a PEM. A bacterium in the anode compartment transfers electrons obtained from an electron donor (e.g. glucose, acetate) to the anode electrode. This occurs either through direct contact (nanowires) or mobile electron shuttles. During electron production protons are also produced in excess. These protons migrate through the PEM into the cathode chamber. Electrons can be also transferred to the anode by electron chemical mediator. But the toxicity and instability of synthetic mediators limit their applications in MFCs. Shewanella putrefaciens is bioelectrochemically active and can form a biofilm on the anode surface and transfer electrons directly (without mediator) by conductance through the membrane. When they are used, the anode acts as the final electron acceptor in the dissimilatory respiratory chain of the microbes in the biofilm. S. putrefacience was grown on LB broth. For aerobic growth, cultures were shaken continuously on a cooling rotary shaker-incubator at 160 rpm at 25°C. For anaerobic growth, approximately 1.25 liter of anaerobically prepare (in the athmosphere controlled chamber) LB broth in glass bottle was inoculated with 12.5 mL of an aerobically grown overnight culture and incubated without agitation. After 96 h of growth, the cells will be harvested under anaerobic conditions by a continuous centrifugation system at 4800 rpm at 4°C. The cell paste will be washed three times in 50mM sodium phosphate buffer containing 0.1 M NaCl . The washed cells was re-suspended in the buffer and transferred to 100 mL capacity anode compartment of the MFC on anaerobic conditions. The two chambered microbial fuel cells (TCMFC) were constructed using two glass bottles. Each bottle's volumes were 100 mL. Each cell compartment had three ports at the top, for electrode wire, addition and sampling of solutions, and gassing. Two compartments were separated by a PEM. The anode compartment was loaded with freshly prepared bacterial suspension (suspended in 50 mM Na-phosphate buffer (pH 7.0) containing 0.1 M NaCl, vitamin, mineral solution and substrate (acetate, ethanol and propionic acid). The cathode compartment was loaded with 50 mM Na-phosphate buffer (pH 7.0) containing 0.1 M NaCl. Nitrogen and air were continuously purged through anode and cathode compartments to maintain anoxic and aerobic conditions, respectively (flow rate of nitrogen gas was approximately 15 mL per min). The microbial fuel cell was immersed in a water bath to maintain temperature (25°C). Cooler was used to supply for summer conditions and heater was used to supply for winter conditions. The air conditioner was also used to supply constant temperature. Voltage (V, volt) or current (I, amper) was measured using a multimeter with a data acquisition system. Power density (mW/m2) was calculated according to P=Current*Voltage /projected area of the anode (P= IV/A.) When the anode compartment of the microbial fuel cells were loaded with freshly prepared S. putrefaciens, potential development was measured under open circuit conditions. Before the fuel (carbon source) was added, open circuit voltage (OCV) approximately 100-200 mV were observed from the microbial fuel cell containing suspensions of S. Putrefaciens. The addition of substrate as the fuel to the cell containing S. Putrefaciens resulted in a rapid rise in OCV up to 780-840 mV. Maximum OCV observed 832 mV, 777 mV and 810 mV for 10 mM glucose centrifuged from anaerobic growth of 1250 mL, 2500 mL and 800 mL from pure culture, respectively. The addition of ethanol was OCV up to 670 mV and addition of propionic acid was OCV up to 803 mV. A membrane MFC inoculated with S.putrefaciens and the circuit was completed with a fixed load of 5000 W were used to determine the power generation as function of load. 10 mM glucose produced 4 µA current. Power density was 0.8 mW/m2. Keywords: Microbial fuel cell, electricity production, Shewanella putrefaciens, voltage, power density. Mikrobiyal yakıt hücreleri (MYH) oksijensiz ortamda elektrojen mikroorganizmaları biyokatalizör olarak kullanarak organik maddelerden elde edilen kimyasal enerjiyi doğrudan elektrik enerjisine çeviren sistemlerdir.Tipik bir MYH’si anot, katot, proton geçirgen membran ve voltaj yada akım değerlerini ölçen veri toplama cihazından oluşur.Elektrojen bakteri oksijensiz ortamda anot üzerinde biyofilm tabakası oluşturarak organik maddeleri, karbondioksit, elektron ve protona çevirir. Bu çalışmada, iki hazneli MYH ve saf kültür Shewanella putrefaciens kullanılmıştır. Bu saf kültür bakterisinin seçilmesindeki amaç, dış membran enzimlerini doğal olarak kullanma yeteneğinde olduğundan elektronlarını iletken bir anota verme kabiliyetine sahip olmasıdır. Böylece bakteri tarafından üretilen elektronları anot elektroduna iletecek dışarıdan kimyasal bir medyatör kullanma gerekliliği ortadan kalkmıştır. Bu çalışmada, MYH’de farklı organik maddelerden ve farklı miktarlarda çoğaltılan saf kültür S. putrefaciens kullanılarak açık devre voltajları ölçülmüştür. 10 mM glikoz kullanılarak 1250 mL besi maddesi içinde çoğaltılan saf kültürün santrifüjünden elde edilen devre voltajı 832 mV iken, 2500 mL saf kültür için 777 mV, 800 mL saf kültür için ise 810 mV olarak ölçülmüştür.10 mM etanol kullanılarak 1250 mL saf kültürden 670 mV, 10 mM propiyonik asit kullanılarak 1250 mL saf kültür için ise açık devre voltajı 803mV bulunmuştur. Besi maddesi olarak 10 mM glikoz kullanıldığında 5000 Ω dış direnç ile çalıştırıldığında amper değeri 4 µA ölçülmüştür. Güç yoğunluğu olarak 0.8 mA/m2bulunmuştur.  Anahtar Kelimeler: Mikrobiyal yakıt hücresi,elektrik üretimi, Shewanella putrefaciens, voltaj, güç yoğunluğu

Benzo[a]anthracene'nin aktif çamur üzerine kronik etkisinin respirometrik incelenmesi

In this study, activated sludge taken from İstanbul ISKI Paşaköy Biological Treatment Plant, acclimated to synthetic peptone mixture for 6 months. Benzo[a]anthracene (B[a]A) was selected as model xenobiotic and the effect of B[a]A to the acclimated activated sludge was investigated. B[a]A is a toxic and carcinogen polycyclic aromatic hydrocarbon (PAH) and generated via cigarette smoke, diesel exhaust, commercial solvents etc. B[a]A is also listed in Environmental Protection Agency (EPA) priority pollutant list. In this study, 0.011 g/L B[a]A was added to the sequencing batch reactor (SBR). The chronic effect of B[a]A to activated sludge, were performed and monitored through respirometric studies as well as conventional parameters. The activated sludge operated 10 sludge ages for chronic effects. The chronic effect was estimated by using a multi-component model. 0.011 g/L B[a]A addition has no effect on COD removal. While biodegradation of peptone mixture, the B[a]A addition effects hydrolysis rate and PHA storage mechanism. The amount of B[a]A in activated sludge and supernatant monitored through high performance liquid chromatography (HPLC). PAHs, which are a class of xenobiotic, are unique contaminants in the environment because they are generated continuously by the inadvertently incomplete combustion of organic matter. PAHs include 70 natural and anthropogenic organic compounds constituted by aromatic rings, ranging between two and seven, and mainly derived from petroleum activities. In the 20th century there was a great increase of anthropogenic production of PAHs by combustion of fossil fuel. Beside of predominating anthropogenic sources e.g. road traffic and combustion of fossil fuels, there are also natural sources, e.g. volcanic eruptions and forest fires. PAHs consist of fused benzene rings in linear, angular or clustered arrangements and contain by definition only carbon and hydrogen atoms. However, nitrogen, sulfur and oxygen atoms may readily substitute in the benzene rings to form heterocyclic aromatic compounds, which are commonly grouped with the PAHs. Due to their toxicity, 16 PAHs were listed by U.S. Environmental Protection Agency (USEPA) as priority pollutants, which should be monitored in aquatic and terrestrial ecosystems. The increase in the hydrophobicity and electrochemical stability is associated with an increase in the number of benzene rings and angularity of a PAH molecule. The high molecular weight (HMW) PAHs are more persistent and recalcitrant than the low molecular weight (LMW) PAHs. The stability and distribution of the PAHs in the natural environment is influenced by the configuration of the aromatic rings, physico-chemical properties. PAHs are considered as important environmental pollutants since many of the compounds in this group are of major concern to environmental agencies and researchers worldwide due to their mutagenic, toxic, genotoxic and carcinogenic properties depending upon the number and configuration of the benzene rings and the presence and position of their substituents. Microorganisms, such as bacteria and fungi, may transform the PAHs to other organic compounds or to inorganic end products such as carbon dioxide and water. The latter process has been referred to as mineralization. Some PAH-degrading microorganisms, primarily bacteria, are capable to use the PAHs as a carbon and energy source, and may thus transform the contaminants into molecules that can enter the organisms’ central metabolic pathways. Other microorganisms have the capacity to degrade PAHs, while living on a widely available substrate. Such co-metabolism does not always result in growth of the microorganism, and sometime the cosubstrate, i.e. the PAH, is only transformed into another compound without any apparent benefit for the organism. Keywords: Xenobiotic, PAH, activated sludge, Benzo[a]anthracene, modeling, respirometer.Benzo[a]anthracene (B[a]A), toksik ve karsinojen bir polisiklik aromatik hidrokarbon (PAH) olup sigara dumanında, dizel araçların egzoz dumanında, yangın sonucu çıkan dumanlarda, ticari solventlerde vb. bulunmaktadır. B[a]A, Amerika’daki Çevresel Koruma Ajansı (Environmental Protection Agency - EPA) tarafından öncelikli kirleticiler listesinde yer alan 16 PAH’tan biridir. Bu çalışmada, benzo[a]anthracene (B[a]A), model zenobiyotik olarak seçilmiş ve B[a]A’nın sentetik pepton karışımına alışmış aktif çamur üzerindeki kronik etkisi incelenmiştir. Aklimasyon çalışmaları İSKİ Paşaköy İleri Biyolojik Atıksu Arıtma Tesisi’nden alınan biyokütle ile başlatılmış, hidrolik bekletme süresi 1 gün olan doldur-boşalt reaktörler çamur yaşı 10 gün olarak işletilmiştir. Kronik deneylere başlamadan önce sistem 3 ay süre ile organik madde olarak evsel atıksuyu en iyi temsil ettiği düşünülen sentetik pepton karışımı (600 mg KOİ/L) ile beslenmiştir. Kronik etkinin belirlenmesi için günde iki çevrim ile çalıştırılan çamur yaşı 10 gün olan bir ardışık kesikli reaktör (AKR) sistemi kullanılmıştır. Sadece sentetik pepton karışımı ile beslenen AKR sistemi, kronik etkinin belirlenmesi için 21 gün boyunca sabit miktarda B[a]A (0.011 g/L) eklenerek izlenmiştir. B[a]A’nın aktif çamur üzerine olan kronik etkisi, respirometrik yöntemin yanı sıra konvansiyonel parametreler ile de incelenmiştir. 0.011 g/L B[a]A eklemesinin KOİ giderimi açısından AKR sistemi üzerine bir etkisi olmadığı anlaşılmıştır. Yürütülen modelleme çalışması, respirometrik testler aracılığıyla Modifiye Edilmiş Aktif Çamur Modeli No. 3’teki kinetikler hakkında deneysel veri desteği ve bilgi sağlamıştır. Pepton karışımının biyolojik parçalanmasında B[a]A ilavesi hidroliz hızında bir artışa neden olmuştur. Bunun yanısıra sistemin depolama mekanizması üzerinde de bir etkisi olduğu görülmüştür.  Anahtar Kelimeler: Zenobiyotik, PAH, aktif çamur, Benzo[a]anthracene, modelleme, respirometre

The characterization and biological treatability of polyamid fibre based carpet finishing waste waters

Polyamid esaslı halı işlem ve üretiminden oluşan atıksuların biyolojik arıtılabilirliğini değerlendiren bu çalışma, farklı atıksu akımları ve kompozit çıkış suyunun detaylı karakterizasyonu, kinetik tanımlaması ve respirometrik modellemesini içermektedir. Günümüze kadar yapılan endüstriyel atık sudaki çalışmaların çoğunluğu tesis dışına akan maddeleri ve genellikle de boru sonu yaklaşımını üzerinedir. Atıksuyun ortalama KOİ’si 1675 mg/l olup 1450-1900 mgKOİ/l aralığında değişmekte olup biyolojik arıtılabilirlik çalışmalarında açık renk boyama atıksuları kullanılmıştır. Organik maddenin %80-90’ı çözünmüş olmasına karşın çok az bir kısmı biyolojik olarak kolay ayrışabilen ve hemen hemen tamamı yavaş ayrışabilir formdadır. Deney sonuçlarının değerlendirilmesinde respirometrik yöntem ve aerobik sistemdeki oksijen tüketim miktarı başlıca model parametresi olarak kullanılmıştır. Respirometrik değerlendirmeler çerçevesinde yavaş ayrışan fraksiyon en iyi şekilde ikili hidroliz mekanizması ile tanımlanmaktadır. Sürekli ve tam karışımlı aktif çamur sistemleri için dizayn uygulamaları, 10 günlük çamur yaşında pek yaygın olmayan 3 günlük uzun bir hidrolik bekletme süresini tanımlamaktadır. Anahtar Kelimeler: Polyamid elyaf, halı üretimi, biyolojik ayrışabilirlik, atıksu karakterizasyonu, yavaş ayrışabilir KOİ, modelleme.Textile industry uses natural and artificial fibres and produces fabric and other textile products which contain also carpet material. So far, the majority of studies on industrial wastewaters has been conducted on plant effluents and mostly reflects an end of pipe approach. The results in the literature mainly report to what extent wastewaters are biodegradable but contain little or no information on the nature of biologically resistant compounds or COD fractions. Industrial wastewaters include a waste array of chemicals used in different steps of the manufacturing process. The impact of these chemical can best be envisaged in different wastewater streams are evaluated in terms of their individual biodegradation characteristics. Respirometric methods and the use of oxygen uptake rate in aerobic systems as a major model parameter has been a major asset in the identification of COD fractions with different biodegradation rates and in model evaluation and calibration of experimental data. These methods are especially useful in cases individual specific pollutants are hard to identify. This paper evaluates biological treatability of wastewaters generated from polyamid based carpet processing and manufacturing. It involves detailed characterization, kinetic description and respirometric modelling of different wastewater streams and the composite effluent. The average COD of the wastewater is measured as 1675 mg/l, varying in the range of 1450-1900 mg/l. Light color dying wastewaters are utilized for biological treatability due to a higher dye content associated with this process. COD fractionation indicates a 80-90 % soluble COD fraction, almost totally slowly biodegradable with a very small readily biodegradable portion. A dual hydrolysis mechanism best describes the biodegradation of the slowly soluble fraction, based on respirometric evaluations. Experimental results have been tested by a multi-component mathematical model using the endogenous decay approach and hydrolysis constants corre­sponding to the slowly biodegradable COD fractions have been evaluated using curve fitting. The very low rate coefficients characterizing the hydrolysis of the large part of the soluble COD bring interesting difficul­ties in the design of biological treatment systems. Design applications for continuous-flow activated sludge systems identify an unusually long hydraulic retention time of 3 days at a sludge age of 10 days. Respirometric analysis of the main wastewater streams provided in dept information on the biodegradation characteristics, which could be translated into the composite plant effluent and confirmed by appropriate COD mass balance. The evaluation showed that acrylic and polyamid carpet finishing wastewater was quite different from domestic sewage and other textile effluents in terms of COD fractionation and biodegradation. It could be characterized by dual hydrolysis of soluble and particulate COD components occurring at much slower rates compared to other wastewaters. The hydrolysis rate of the particulate COD was almost comparable to endogenous decay. Furthermore, in biological treatability studies, respirometry based modeling showed that the acclimated biomass exhibited similar biological response to individual wastewaters originated from each process step compared to composite sample characterizing the overall process scheme of acrylic and polyamid carpet production. On the other hand, simulation results on performance prediction and overall treatability indicate that slow hydrolysis of the major fraction of soluble COD, although rate limiting, does not pose a significant problem for effluent quality. Keywords: Polyamid fibre, carpet manufacturing, biological treatability, wastewater characterization,  slowly biodegradable COD, modelling

Influence of pH on soluble substrate generation with primary sludge fermentation

Çalışma kapsamında pH’nın ön çökeltme çamuru fermentasyonu sonucu çözünmüş besi maddesi oluşumuna etkisi incelenmiştir. Bu kapsamda pH kontrollü ve konrolsüz koşullarda paralel deney setleri yürütülmüştür. 20°C sabit sıcaklıkta gerçekleştirilen ön çökeltme çamuru fermentasyonu sonucunda çözünmüş Kimyasal Oksijen İhtiyacı (KOİ) salımı ortalama 14 mg/L olarak hesaplanmıştır. Bu değere karşı gelen Uçucu Yağ Asiti (UYA) oluşumu ise 11.7 mg/L KOİ olarak hesaplanmıştır. Elde edilen bu değer, toplam biyolojik ayrışabilir KOİ içeriğinde %5 artışa karşı gelmektedir. Bu değere karşı gelen UYA üretimi ise ortalama 9.2 mg KOİ/L olarak belirlenmiştir. Fermentasyon sonrasında azot (0.4 mg/L) ve fosfor (0.1 mg/L) şeklinde besi maddesi salımlarının ihmal edilebilecek düzeyde olduğu gözlemlenmiştir. Yapılan bütün deneylerin sonucunda asetik asit üretimi toplam UYA’nın %45’inden fazlasını oluşturmuştur. Yüksek pH değerlerinde ve başlangıç UAKM değerlerinin arttığı durumlarda UYA’nın asetik asit içeriğinde düşüş, propiyonik asit ve C4-C5 asitlerinin oranlarında artış gözlenmiştir. Ön çökeltme çamurunda pH ayarının ve kontrolünün 5.5 ve 6 değerlerinde fermentasyon reaksiyonunu olumsuz yönde etkileyerek daha düşük konsantrasyonda UYA oluşumuna neden olduğu belirlenmiştir. Aynı zamanda pH ayarının ve kontrolünün 5.5 ve 6 değerlerinde asidojenik fazda gecikmeye ve reaksiyon süresinin uzamasına neden olduğu görülmüştür. Yüksek pH değerlerinde ise (pH 7.5) hidroliz fazında iyileşme saptanmış, ancak düşük pH değerlerinde olduğu gibi yüksek pH değerlerinin de asidojenik fazı olumsuz etkilediği gözlemlenmiştir. Çamurun başlangıç pH değerine yakın olan pH 6.5 ve 7 kontrollü setleri ise kontrolsüz setlerle aynı sonuçları verdiği için pH kontrolünün ekonomik anlamda uygulanabilir olmadığı belirlenmiştir. Anahtar Kelimeler: Besi maddesi giderimi, çözünmüş fermentasyon ürünleri, KOİ bileşenleri, kütle dengesi, uçucu yağ asitleri.A significant function of primary sludge fermentation is now regarded as the generation of soluble organic compounds, in particular Volatile Fatty Acids (VFAs), that are necessary for Biological Nutrient Removal (BNR) processes. VFAs are by nature readily biodegradable and therefore most suitable carbon source for denitrification. Their presence in sufficient quantity is also required for biological phosphorus removal systems. The merit of primary sludge fermentation is partial conversion of the settled Chemical Oxygen Demand (COD) into soluble and mostly readily biodegradable components and especially VFAs. In fact, pre-fermentation essentially sustains the first phase of anaerobic biodegradation. It is basically characterized by the generation of soluble COD. The study was undertaken to evaluate the effect of pH control on the generation of soluble fermentation products from primary sludge. The effect was tested by running parallel experiments under pH controlled and uncontrolled conditions. Primary sludge samples were taken from the Atakoy treatment plant, a small domestic wastewater treatment facility located in Istanbul, Turkey. The effect of pH on primary sludge fermentation was assessed using a series of experiments where the pH of the anaerobic reactor was sequentially adjusted and maintained at the following pH values: 5.5, 6, 6.5, 7, and 7.5 throughout the tests (controlled series). In fermentation experiments conducted at 20 ºC without pH control, the average soluble COD release was 14 mg per liter of wastewater treated, representing a potential increase of 5% in the biodegradable COD content of the primary sedimentation effluent. 27% lower VFA production was observed at pH 5.5, 18% at pH 6.0 and 12% at pH 7.5. The corresponding average VFA generation was 9.2 mg COD/L. Similarly, soluble COD generation was 10% lower at pH 5.5 and remained practically the same at pH 6.0. Increasing the pH to 7.5 resulted in 26% higher soluble COD generation indicating that higher pH favored hydrolysis but not acidification. Experimental assessment of VFAs composition indicated the predominance of acetic acid in fermentation products. In the majority of runs, the acetic acid fraction of the total VFA was over 45%. The average COD equivalent of VFAs was computed as 1.36 mg COD mg/L VFA for uncontrolled pH conditions. Increasing the pH level of primary sludge fermentation, the acetic acid percentage of the generated VFAs significantly decreased leading to the production of more propionic acid and C4?C5 (butyric, izobutyric, valeric ve izovaleric) acids. The highest percentage of the acetic acid production was around 70%, observed at pH 5.5. In experiments where pH was not controlled, the soluble TKN concentration released changed in the range of 75?175 mg/L with an average value of 97 mg/L, presumably depending on wastewater quality and resulting primary sludge characteristics. The soluble TKN represented on the average 2% of the VSS reduced, 4.6% of the soluble COD released and 5.7% of the VFA COD generated (0.057 mg N/mg CODVFA). Soluble P release was practically the same for experiments with pH controlled and uncontrolled runs with an average value of around 20 mg/L. This level corresponded to 1.3?1.4% of the VFA COD produced (0.013 mg P/mg CODVFA). Sludge fermentation experiments without pH control induced an average soluble COD release of 14 mg/L, which varied in the range of 8.4?19.6 mg COD/L. In terms of mass balance, this represents 5% of the biodegradable COD in the primary sedimentation effluent, which would be increased to 279 mg COD/L if the fermenter supernatant were to be added back to the effluent stream. The corresponding average VFA generation was calculated as 11.7 mg COD/L. Also, 0.6 mg/L of the nitrogen and 0.1 mg/L of phosphorus removed by settling were released with primary sludge fermentation. pH adjustment and control outside the initial pH of the primary sludge had a negative effect on VFA generation. Two general comments may be associated with the pH control (i) delay in acidification/ longer fermentation times (ii) lower VFA production. pH adjustment and control in the range of 5.5?6.0 had a negative effect on fermentation efficiency, mainly observed as lower VFA generation and delay in acidification and longer fermentation times. A similar negative effect was also observed when the pH was increased to 7.5. pH control in the 6.5?7.0 range, close to the initial pH of the primary sludge essentially yielded the same results and did not prove meaningful. Keywords: Nutrient removal, soluble fermentation products, COD fractions, mass balance, volatile fatty acids

The substrate storage concept and the modelling applications for tannery wastewater

Son yıllarda aktif çamur arıtma sistemlerinin tasarımında IWA Çalışma Grubu tarafından önerilen en son model olan ASM3 ile substratın depolama polimerlerine dönüştükten sonra heterotrofik biyokütle tarafından tüketildiği varsayımı dikkate alınmaktadır. Ancak bu yaklaşım uygulama kolaylıkları getirmekle birlikte gerçeği yansıtamamakta ve kolay ayrışan substratın (SS) tanımı uygulamalarda zorluk yaratmaktadır. Bu çalışmada, daha gerçekçi bir yaklaşım olan, substratın kısmen çoğalma kısmen de depolama ürünleri oluşumu ile tüketildiği görüşü deri atıksuyu için uygulanmıştır. Dinamik koşullar altında, farklı modeller olan ASM1, ASM3 ve ASM3’ün simültane çoğalma ve depolamayı içeren versiyonları hazırlanarak elde edilen simülasyon sonuçları birbirleri ve literatür verileri ile karşılaştırılmıştır. Anahtar Kelimeler: Aktif çamur modellemesi, simultane çoğalma ve depolama kavramı, ASM1, ASM3, OTH.Consumption of substrate firstly in the form of stored polymers and subsequent use of the stored polymers by heterotrophic biomass recently introduced in the activated sludge system design by IWA Task Group with ASM3. Although this approach brings ease of application in calculations, it dose not reflect the reality and the definition of readily biodegradable substrate (SS) causes problems in applications. A more realistic approach, that is the simultaneous growth and storage concept on external substrate has been presented and applied for tannery wastewater. Different models, namely, ASM1, ASM3 and modified versions of ASM3 involving simultaneous growth and storage have been investigated under dynamic conditions. The simulation results were compared with each other and literature data. Model simulation results for ASM1 were quite consistent with literature but the results have shown that ASM3 modeling results gave better descriptions of the OUR response compared to ASM1. The comparison of the simulation results lead to the conclusion that the possibility of describing the real case increases, as the model gets more detailed. Observations suggest that the relative weight of biochemical reactions such as growth and storage shifts as the feeding pattern fluctuates between feast and famine conditions and models with a single mechanism like ASM1, although convenient from a practical viewpoint may become insufficient for a consistent explanation when the feeding rate (F/M ratio) changes. Keywords: Activated sludge modelling, simultaneous growth and storage concept, ASM1, ASM3, OUR

Effect of primary sludge fermentation products on mass balance for biological nutrient removal system

Ön çökeltme çamuru fermentasyonunun kolay ayrışabilir organik madde oluşturma potansiyeli ve karbon, azot ve fosfor olmak üzere oluşan ön çökeltme ürünlerinin kütle dengesine olan etkisi, laboratuvar ortamında, 20°C sabit sıcaklıkta gerçekleştirilen kesikli deneyler ile incelenmiştir. Fermentasyon sonucunda, ön çökeltme çamurundaki uçucu askıda katı madde’nin %18’den %30’a varan oranlarda çözünmüş biyolojik ayrışabilir KOİ’ye dönüştürüldüğü gözlenmiştir. Fermentasyon sonrasında, çözünmüş KOİ’nin %85’inin uçucu yağ asitlerinden oluştuğu belirlenmiştir. Uçucu Yağ Asitlerinin (UYA) dağılımı, %47 asetik asit, %35 propiyonik asit, %9 bütirik asit ve %9 valerik asit olarak bulunmuştur. Toplamda oluşan UYA’ların KOİ karşılığı 1.38 mg KOİ/ mg UYA olarak hesaplanmıştır. Biyolojik fermentasyon sonrasında elde edilen ve toplam uçucu yağ asitlerinin yaklaşık yarısını oluşturan asetat, denitirikasyon ve biyolojik besi maddesi gideren sistemlerde çok önemli bir karbon kaynağıdır. Ön çökeltme çamurunun fermentasyonu sonucunda, çözünmüş azot üretiminde 0.7 - 3.6 mg NH4-N/g KOİ ve çözünmüş fosfor üretiminde 0.3 - 0.8 mg PO4-P/g KOİ dönüşüm oranları belirlenmiştir. Fermentasyon ürünlerinin, 0.4’ten 0.1’e doğru düşen anoksik hacmin proses hacmine oranı (VDN/V) çalıştırma koşullarına bağlı olarak ön çökeltme çıkış akımında denitrifikasyon potansiyelini (NDP) %10 - 20 arasında arttırdığı görülmüştür. Fermente olmuş ön çökeltme çamurunun üst fazının geri kazanılabilen kısmı, çıkış akımının kolay ayrışabilir KOİ içeriğini %5 ve aynı zamanda çözünmüş azot ve fosfor içeriğini de %2 arttırabilmektedir. Anahtar Kelimeler: Aktif çamur, besi maddesi giderimi, çökelebilen KOİ, fermentasyon ürünleri, KOİ bileşenleri, kolay ayrışabilir KOİ, ön çökeltme.Nutrient removal from wastewater is the main concern, especially in areas sensitive to eutrophication. Coastal zones open to touristic activities require wastewater treatment involving maximum nutrient control in order to maintain the delicate balance between excessive land use and desired water quality. Effective biological nitrogen and phosphorus removal requires full utilization of the internal pool coming from the process influent. In most cases, primary settling is the commonly prescribed step before biological wastewater treatment. It removes a significant portion of the influent COD, around 30 to 40% in domestic sewage. Primary settling step is sometimes omitted to increase the internal carbon potential in cases where the magnitude of the COD available in the influent is critically limiting for the desired level of nutrient removal. It is a fact that, the nature and the biodegradation rate of the available carbon are important factors for an efficient system operation. The COD fractionation identifying fractions with different biodegradation rates has been a milestone in understanding and modeling the substrate utilization, especially in nutrient removal. This study evaluates mass balance applicable to internal organic carbon pool of domestic sewage in terms of different COD fractions, with the specific objective of investigating the potential of simple (uncontrolled) primary sludge fermentation for the generation of readily biodegradable substrate. Fermentation products were also evaluated by means of respirometric analyses. Batch experiments were conducted, at 20°C constant temperature, to investigate the potential of primary sludge fermentation for the generation of readily biodegradable substrate and to evaluate the effect of primary sludge fermentation products on mass balance including nitrogen and phosphorus. Limited fermentation without pH control converted 17% of the particulate COD removed from sewage by means of primary settling to simpler soluble compounds, mainly to VFAs through acidification of the sludge in the fermenter. Experimental evaluation shows that fermentation converted between 18 to 30% of the initial volatile suspended solids (VSS) in the sludge into soluble biodegradable COD. Approximately 85% of the soluble COD is volatile fatty acids after the fermentation process. The net yield giving the fraction of the total COD in the primary sludge converted into volatile fatty acids (VFA's) varied in the range of 0.095 to 0.19 g VFA COD/g COD. The average fraction of the VFA's in fermentation is 47% acetic acid, 35% propionic acid, 9% butyric acid and 9% valeric acid. Based on these observations, the COD equivalent of VFA was calculated as 1.38 mg COD/mg VFA. The recoverable fraction of the fermented sludge supernatant was calculated to have the potential of increasing the biodegradable COD content of the primary effluent by 5% and the readily biodegradable COD in the effluent by 30%. The results clearly showed that the predominant fermentation products are always acetic and propionic acid, independent of the values of the operational parameters. The most important volatile fatty acids obtained during the biological fermentation process is acetate with approximately half of total VFA concentration, which is one of the most important carbon source for denitrification and biological nutrient removal processes. Ammonium and phosphate release during biological fermentation process were less than 1% and 2%, respectively. Therefore, the fermentation may be used directly in the BNR process without any separation of ammonia and phosphate. Primary settling reduced NDP of the raw sewage by 17 to 29%, approaching the level of the COD fraction removed as VDN/V ratio increases. Fermentation products provided an additional denitrification potential of around 2 mg N/L, increasing NDP of the primary effluent in the range of 10 to 20% depending on the gradual decrease of the operating VDN/V ratio from 0.4 to 0.1. Model simulation indicated that fermentation products could improve the biological P removal potential of the primary effluent reducing the effluent P concentration from 2.7 mg P/L to 0.6 mg P/L. The recoverable fraction of the fermented sludge supernatant may potentially increase the readily biodegradable COD content of the primary effluent by 5% and soluble nitrogen and phosphorus content by 2%. Keywords: Activated sludge, nutrient removal, settleable COD, fermentation products, COD fractionation, readily biodegradable COD, primary settling

Evaluation of aerobic stabilization of biological treatment sludges

Ülkemizde uygulanan çevre mevzuatı gerekleri, atıksu arıtma tesislerinde oluşan çamurun arıtımını ve nihai uzaklaştırılmasını zorunlu kılmaktadır. Evsel ve endüstriyel atıksu arıtma tesislerinden kaynaklanan arıtma çamurları üzerinde yapılan analizler sonucu, bu çamurların özellikle toplam ve çözünmüş organik karbon değerlerinin yönetmelikteki değerleri sağlamadığı ve çamurların bu parametreler bakımından tehlikeli atık sınıfında değerlendirmesi gerektiğini ortaya koymaktadır. Bu çalışma kapsamında Marmara Bölgesi’nde yer alan çeşitli evsel ve endüstriyel arıtma tesisinden kaynaklanan çamurların organik madde içerikleri değerlendirilmiş ve bu çamurların stabil hale getirilmesi için aerobik stabilizasyon işlemi uygulanmıştır. Aerobik stabilizasyon reaktörlerinde, 15 gün süreyle organik madde içeriklerinin değişimi UAKM, TOK ve ÇOK parametreleri esas alınarak ve evsel çamur numuneleri için zehirlilik parametresi de dikkate alınarak incelenmiştir. Elde edilen sonuçlara göre aerobik stabilizasyon sonunda genel olarak TOK değerleri azalırken, ÇOK değerlerinde çamur numunelerine bağlı olarak artış ya da azalmalar gözlenmiştir. İncelenen evsel çamurların ikisinde de TOK konsantrasyonu %50’den daha fazla azalırken ÇOK değerlerinde artış tespit edilmiştir. Endüstriyel atıksu arıtma çamurları arasında en yüksek TOK giderimi %62 ile Nevresim Endüstrisi çamurunda gözlenmiş olup, bu endüstri ÇOK giderimde de en yüksek verimi sağlamıştır. Elde edilen bu sonuçlar ışığında, aerobik stabilizasyon işleminin uygulanma aşamasından önce her tesis için ayrıca değerlendirme yapılması gerekliliğini ortaya koymuştur. Her çamur örneği için standartların sağlanması aerobik stabilizasyon ile mümkün olamamasına rağmen, bu işlemin bazı organik maddelerin giderilmesini sağladığı aerobik stabilizasyon sonrasında evsel numunelerdeki zehirliliğin tamamen giderilmesi ile ortaya konmuştur. Anahtar Kelimeler: Çamur, stabilizasyon, aerobik, evsel- endüstriyel-tehlikeli atık.The main waste-product of the biological wastewater treatment processes is the excess sludge which needs to be disposed properly to prevent the entry of the pollutants back into the water cycle, especially after the disposal of the wasted sludge cakes into the landfill area. During the adaptation period of European Union membership of Turkey, the increase in the number of both municipal and industrial Wastewater Treatment Plant (WWTP) due to the stringent new regulations for wastewater treatment will pose more significant sludge disposal and sanitation problems in the future for Turkey. Treatment and ultimate disposal of domestic and industrial wastewater treatment plant sludges is obligated according to the regulations in Turkey. Treatment sludges categorized in three different groups namely: inert sludge, non-hazardous sludge and hazardous sludge according to the characteristics of the sludge. The total organic carbon (TOC) concentration of the sludge itself and dissolved organic carbon (DOC) concentration in the eluent of the sludge are mainly used for this classification. The higher levels of TOC and DOC values qualifies the domestic and industrial wastewater treatment sludges as hazardous sludge. The principal objective of sludge treatment is its stabilization, that is a controlled decomposition of easily degradable organic matter resulting in a significant reduction of volatile suspended solids (VSS) content, a change of an unpleasant smell into an earthy one, and an elimination of sludge putrescibility. Aerobic biological stabilization at ambient conditions has traditionally been undertaken for the stabilization of treatment sludges originated from both domestic and industrial wastewater treatment plants. In this study the characterization of the different treatment sludges originated from domestic and industrial wastewater treatment plants in Turkey was investigated and the stabilization level of these sludges was evaluated by using aerobic stabilization process. The stabilization level of sludges was evaluated by monitoring the VSS, TOC and DOC content of the sludge. Moreover, ecotoxicological assays were conducted on domestic wastewater treatment plant sludges to observe the effect of stabilization on the toxicity. Respirometric and modeling studies were also performed to assess the decrease in the organic content of the domestic wastewater treatment plant sludge during aerobic stabilization. The results of analysis conducted on the sludge itself and sludge eluent indicated that the sludges are in hazardous nature. These results suggest that the treatment sludge generated from both domestic and industrial treatment plants have to stabilized before ultimate disposal. During the course of the aerobic stabilization experiments, VSS, TOC and DOC measurements were performed at the beginning and 15 days after the beginning (at the end of the stabilization experiment) in order to monitor the extent of VSS, TOC and DOC removal. Measured TOC and DOC concentrations during the stabilization experiments of studied treatment sludges did not show a consistent trend during the 15 days of stabilization. However, the stabilization of the industrial wastewater treatment plants sludges showed a paralel stabilization to the domestic sludge. However, it is important to conduct laboratory studies prior to the application of aerobic stabilization to a treatment plant on the case basis. The acute toxicity as EC20 (%) and EC50 (%) shows the toxic value in terms of effective concentrations (%) of tested solutions that result in 20 and 50% of bioluminescence decrease. The EC20 and EC50 values were found between 0.3 and 7.3% for the studied raw domestic sludges which is in accordance with the literature data. Significant decrease in the toxicity of domestic wastewater treatment plant sludges were observed at the end of the 15 days of aerobic stabilization. The evaluation of the results obtained in this study showed that aerobic stabilization could be an alternative for stabilization of sludges originated from domestic and industrial wastewater treatment plants. However, the organic content of the sludges mainly depend on the influent wastewater characterization of wastewater treatment plant which affects the stabilization performance. Sludge stabilization results indicate higher VSS, TOC and DOC removal efficiencies for domestic wastewaters compared to the industrial sludges. Although aerobic stabilization was not successful for the compliance with the standards in each case, the removal of toxicity exerted by sludges after 15 day-stabilization suggest that at least some toxic organic material has been succesfully biodegraded during the stabilization. In order to provide appropriate municipal and industrial sludge management in Turkey, more elaborate research and engineering experience should be gained. Keywords: Sludge, stabilization, aerobic, domestic- industrial-hazardous waste

Model based process optimization of enhanced wastewater treatment plants

Avrupa Birliği’ne uyum sürecinde ele alınan atık sorunu kapsamında, alıcı ortamlara yapılacak deşarjlarda konvansiyonal parametrelerin yanısıra azot ve fosfor (besi maddesi) parametrelerinin de belli standart değerlerin altına indirilmesi gerekli hale gelmiştir. Bu nedenle, “Kentsel Atıksu Arıtımı Yönetmeliği, 2006” ile uyum sürecinde olan ülkemizde azot ve fosfor standartları mevzuatımıza dâhil edilmiştir. “Kentsel Atıksu Arıtımı Yönetmeliği, 2006” kapsamında mevcut tesislerin besi maddesi giderimine yönelik olarak geliştirilmesi, yeni kurulacak tesislerin ise besi maddesi giderecek şekilde en uygun arıtma teknolojisi kavramı çerçevesinde boyutlandırılması gereklidir. Besi maddesi giderimine yönelik en uygun arıtma teknolojisi biyolojik prosesler, bunlar arasında en ekonomik çözüm ise aktif çamur sistemleri olarak tanımlanmaktadır. Bu çalışma aktif çamur tesislerinin, Avrupa Birliği normlarında performansını sağlayabilecek optimum tasarım ve işletme süreçlerinin değerlendirilmesini amaçlamaktadır. Bu kapsamda, bir örnek olarak ele alınan İstanbul Su ve Kanalizasyon İdaresi (İSKİ) Paşaköy İleri Biyolojik Atıksu Arıtma Tesisi’nde mevcut durumda atıksu karakterizasyonu ve sistem performansı deneysel olarak belirlenmiş, elde edilen bilgiler kullanılarak sürekli kullanıma uygun olacak model-bazlı tasarım ile işletme simülasyon programları hazırlanmış ve işletme optimizasyonu çerçevesinde çıkış besi maddesi konsantrasyonlarının düşürülmesi amacıyla işletme senaryoları oluşturularak önerilerde bulunulmuştur. Yürütülen senaryo analizleri ile, havalandırma tanklarındaki çözünmüş oksijen seviyelerinin uygun ayarlanması, tesisin geri devir denitrifikasyonu prensibi yerine A2O veya UCT tipi sistem şeklinde işletilmesi ile sistem veriminin arttırılabileceği ve dolayısıyla çıkış besi maddesi konsantrasyonlarının azaltılabileceği belirlenmiştir. Anahtar Kelimeler: İleri biyolojik atıksu arıtma tesisi, atıksu karakterizasyonu, model-bazlı tasarım, işletme optimizasyonu.The Urban Wastewater Treatment Directive published in the Official Gazette No. 26047 of 08.01.2006 was adapted from the “The Council Directive (91/271/EEC)” concerning urban waste-water treatment was accepted in European Union Countries, which imposes enforcements about the collection and treatment of wastewater. This directive requires that also nitrogen and phosphorus (nutrients) to be removed together with the conventional parameters. In this context, it is very important to follow and apply the technological advances while the harmonization of legislations in Turkey with European Union Standards. Mathematical models are frequently used for the design and optimum operation of wastewater treatment systems. In order to use the activated sludge models for the process design and control, it is crucial to understand the behavior of complex biological reactions under steady and dynamic conditions. The initial step for the use of models should be, a model calibration according to the data obtained from the treatment plant and an analysis of the behavior of the treatment plant under dynamic influent and environmental conditions (Vanrolleghem et al., 2003). After the calibration of the prepared model according to the operational conditions of the treatment plant, the model can be used for the optimization of the plant, meeting the effluent quality standards, minimizing operational costs and for developing appropriate process control strategies. On the other hand the effect of changes in the process conditions on the model stability should be taken into consideration (Insel et al., 2007). The aim of this study was to evaluate the optimum design and operational criteria of advanced biological wastewater treatment plants by applying international monitoring and evaluation mechanisms that will increase the performance to norms required in the European Union. Accordingly, İSKİ Paşaköy Advanced Biological Wastewater Treatment Plant (ABWWTP) was chosen as a model plant and in the first stage on influent wastewater characterization, chemical oxygen demand (COD) fractionation and performance of the activated sludge system were experimentally determined. In the second stage, using the dimensions of the İSKİ Paşaköy ABWWTP units and the experimentally determined operational parameters, model calibration studies were conducted. On this context, theoretical parameters of model-based design and operational simulation programs applied for the plant were evaluated. In the last stage of the study, for operational optimization, according to the results obtained from the experimental and simulation studies conducted at İSKİ Paşaköy ABWWTP, operational scenarios were developed and suggestions were made. In the scenario analysis reduction of effluent phosphorus and total nitrogen concentration was aimed and the effect of (i) the aeration system control, (ii) recycle denitrification (iii) influent VFA concentration was analyzed and the effect of (iv) different system configurations was evaluated. The results of statistical data analysis of wastewater characterization studies conducted at İSKİ Paşaköy Advanced Biological Wastewater Treatment Plant aiming nitrogen and phosphorus removal revealed that due to low influent Chemical Oxygen Demand (COD), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and Volatile Fatty Acids (VFA) concentrations, high efficiencies of biological phosphorus removal was not achievable. According to the scenario analysis performed for the treatment plant it has been concluded that it is possible to increase the removal efficiency of the system and achieve lower effluent total nitrogen and phosphorus concentrations by setting the dissolved oxygen levels to appropriate levels and operating the systems as an A2O or a UCT type system instead of a recycle denitrification system. It has been concluded that if the scenario analyses were applied it is not possible to meet the European Union Effluent Quality Standard of 1.0 mg/l for the phosphorus parameter. Experimental and model based studies have to be conducted for the installation of a fermentation process together with different system configurations that are required to meet the effluent quality standard by biological treatment. Keywords: Paşaköy wastewater treatment plant, wastewater characterization, model based optimization, process control

Performance of a moving bed sequencing batch reactor for carbon and nutrient removal

The aim of this study was to investigate the performance of a Moving Bed Sequencing Batch Biofilm Reactor (MBSBBR) with regard to organic matter removal and nitrification. Within the scope of this study, the kinetic constants for organic matter removal and nitrification in a lab-scale MBSBBR fed with a synthetic influent of domestic wastewater characteristics were determined. The evaluation of the results revealed that removal of organic matter at high rates and with efficiencies over 90% was secured at all operational conditions applied. Full nitrification was obtained with a rate of 0.241 g NOX-N/m2.d-1 at 20 °C. The autotrophic growth rate was determined to be 0.50 d-1