Ammonium removal using ANAMMOX process and characterization of the population

Atıksuların alıcı ortama deşarjında özellikle azot bileşenleri için getirilen sıkı standartlar mevcut sistemlerin yerine alternatif yöntemlerin geliştirilmesini gerektirmektedir. Anaerobik amonyum oksidasyonu (Anammox), özellikle yüksek azot yüküne sahip atıksuların arıtılmasında yeni ve güçlü bir sistem olarak ortaya konmuştur. Bu çalışmada tam karışımlı sürekli bir anammox reaktöründe yüksek konsantrasyonda amonyum içeren sentetik atıksu kullanılarak, 262 gün boyunca amonyum giderim verimi incelenmiştir. 1. ve 262. günler arasında sisteme verilen amonyumun %90’ının ve nitritin %99’unun giderildiği görülmüştür. Reaktörden biyokütle atılmadığından, sistem kademeli olarak artırılan azot ile yüklenmiştir. Yüklemedeki bu artış sonunda hacimsel nitrit ve amonyum dönüşüm hızı ve nitrat üretim hızı artmıştır. Çalışmada anammox prosesini yürüten mikroorganizma topluluğunun FISH analizi ile karakterizasyonu yapılmıştır. Prosesi oluşturan biyokütle topluluğunun Planktomaysit türünde Anammox bakterilerinin Dokhaven-2 alt türünden oluştuğunu göstermiştir. Anahtar Kelimeler: Anammox, amonyum, Flüoresan in situ hibridizasyon (FISH).Stringent standards for nitrogen discharge necessitate the implementation of new systems for the sustainable removal of ammonium from wastewater. One of such systems is based on the process of anaerobic ammonia oxidation called as Anammox, which is a new powerful tool especially for strong nitrogenous wastewaters. In this study, continuous flow experiments were conducted in an anammox reactor with synthetic wastewater for 262 days. Between days 1 and 262, 90% ammonium and 99% nitrite removal was obtained. In this period, the average ammonium and nitrite degradation and nitrate production yielded a ratio of 1:1.31:0.18. Since almost complete biomass retention was achieved in the reactor, the nitrogen load of the reactor could be increased gradually. In this sense, increased volumetric ammonium and nitrite conversion rates were obtained. Volumetric ammonium conversion rate was increased from 0.002 to 0.28 kg NH4+-N m-3reactor day-1 and volumetric nitrite conversion rate was increased from 0.002 to 0.363 kg NO2--N m-3reactor day-1. The microbial community in the reactor was characterized with Fluorescence in situ Hybridization. Results obtained from the continuous flow experiments made possible to evaluate the process performance and dynamics of the anammox population. FISH analysis showed that the biocommunity in the reactor was dominated by Dokhaven strain of Planctomycete-like Anammox bacteria. Keywords: Anammox, ammonium, Fluorescence in situ hybridization (FISH)

Innovative technologies for biological nitrogen removal; ANAMMOX and SHARON processes

Bu çalışmada ANAMMOX ve SHARON reaktörlerinde azot giderim performansı incelenmiştir. Her iki sistemin performansları farklı amonyak yükleri ve farklı hidrolik bekletme süresi gibi dinamik koşullar altında incelenmiştir. SHARON reaktörünün başlangıç periyodunu oluşturan süreçte nitrifikasyon bakterilerinin kültür zenginleştirme çalışmalarında en yüksek spesifik amonyum oksidasyon hızı 0.1 mg NH4+-N/mg UAKM.saat olarak elde edilmiştir. Kemostat reaktörde çamur yaşı 1.15 gün ve reaktör sıcaklığı 35±2oC olarak gerçekleştirilen işletme koşullarında kısmi nitrifikasyona ulaşılmış ve işletme boyunca ortalama %90 amonyum azotu giderim verimi ile 2.8 mg NH4+-N/mg UAKM.saat spesifik amonyum oksidasyon hızı elde edilmiştir. Sistem metanol ilavesi ile döngüsel anoksik-aerobik fazlarla çamur yaşı 1.5 gün olan işletme koşullarında çalıştırıldığında oluşan nitritin ortalama %25’i denitrifiye edilebilmiştir. ANAMMOX reaktörü ise tam karışımlı sürekli akımlı bir reaktörde sistemden biyokütle atılmaksızın işletilmiş ve işletme boyunca sisteme verilen amonyum azotunun %90’nın ve nitrit azotunun %99’unun giderildiği görülmüştür. Çalışmada ayrıca ANAMMOX prosesini gerçekleştiren mikroorganizma topluluğunun FISH analizi ile karakterizasyonu yapılmıştır. Prosesi oluşturan biyokütle topluluğunun Planktomisit türünde ANAMMOX bakterilerinin Dokhaven-2 alt türünden oluştuğu görülmüştür. Deneysel bulgular yüksek amonyum içeren atıksuların arıtımında ANAMMOX ve SHARON proseslerinin yüksek verimlerle ve düşük çamur üretimiyle alternatif teknolojiler olarak kullanılabileceğini göstermektedir. Anahtar Kelimeler: Anaerobik amonyum oksidasyonu(ANAMMOX), kısmi nitrifikasyon-denitrifikasyon (SHARON), floresan yerinde hibritleşme (FISH), kemostat.It is widely acknowledged that nitrogen in wastewater has become one of the major pollutants to the water resources. Nitrate, nitrite and ammonium are important pollutants in municipal and industrial wastewaters. Conventional methods for the biological removal of these compounds involve two discrete steps namely nitrification and denitrification. Firstly, nitrification is an energy demanding process for aeration and due to low growth rate of nitrifiers, large nitrification volumes are required. Secondly, denitrification requires organic carbon as electron donor. If the carbon content in the wastewater is not sufficient, an extra carbon source has to be supplied which causes an increase of overall treatment costs. Stringent standards on disposal of treatment sludges require aerobic or anaerobic biological sludge treatment. The effluents from anaerobic sludge digesters contain high ammonium and low organic matter and they have relatively low flow rates. In wastewater treatment plants with anaerobic sludge digestion, 15-20% of the inlet nitrogen load is recycled with the return liquors from sludge dewatering. Separate treatment of this digester supernatant would significantly reduce the nitrogen load of the main stream and improve nitrogen elimination. Chemical elimination of ammonium with magnesium ?ammonium ?phosphate (MAP) precipitation or with air stripping is feasible but it seems to be more expensive than classical biological processes. Anaerobic ammonium oxidation process (Anammox) is a new low-cost alternative to conventional denitrification systems especially for sludge digestion effluents. Anaerobic ammonium oxidation is the oxidation of ammonium to dinitrogen gas with nitrite as the electron acceptor. The process is mediated by autotrophic bacteria that use CO2 as the only carbon source. Another promising process is SHARON process that is suitable for the treatment of high strength wastewaters (high in ammonia, low in organic matter concentration). The SHARON process makes use of the growth rates of ammonia and nitrite oxidizers at sufficiently high temperatures (more than 26±C). It works at a hydraulic retention time higher than the growth rate of nitrite oxidizers but lower than ammonia oxidizers (about 1 day). This process has no sludge retention thus nitrite oxidizers are not able to remain in the reactor and they are washed out. Process is operated alternating oxic and anoxic conditions with instantaneous methanol addition. If the Anammox process is combined with a preceding nitrification step, only part of the ammonium needs to be nitrified to nitrite while the Anammox process combines the remaining ammonium with the nitrite to yield dinitrogen gas and a small amount of nitrate. Consequently, complete nitrogen removal would be achieved without addition of methanol. Partial nitrification will reduce oxygen demand in the nitrification reactor and leads to a second reduction in costs. The biomass yield of the Anammox process is very low; consequently little sludge is produced. The low sludge production is the third factor that contributes to the substantially lower operation costs compared to conventional biological nitrogen removal systems. In this study, results obtained from Anammox and SHARON reactors are presented comparatively. An enriched culture of Anammox reactor was run for 262 days where high ammonium removal efficiency was observed.  Reactor was fed with increasing nitrogen loads without biomass wastage. 90% of ammonia and 99% of nitrite were converted into dinitrogen gas. Due to complete biomass retention and increased nitrogen loadings, ammonia and nitrite conversion rates were increased. Molecular examination of Anammox culture with FISH analysis showed that culture was dominated by Dokhaven-2 subclass. Ammonium oxidizers were formerly enriched in fill and draw reactors for SHARON reactor with increasing ammonium loadings. Once reliable ammonium oxidation was obtained, the culture was transferred into a chemostat and fed with higher ammonia loads. Reactor was operated with a hydraulic retention time of 0.98-1.15 days and temperature was kept about 35±2oC which is suitable for selective enrichment of ammonia oxidizers. The observed high specific ammonia oxidation rate and formation of nitrite indicated that highly active ammonia oxidizing culture was enriched. The SHARON process was established with alternating oxic and anoxic conditions with subsequent addition of methanol. In SHARON reactor only 25% of nitrite was denitrified principally due to insufficient methanol addition. Keywords: ANAMMOX, SHARON, ammonium oxidation, denitrification, Fluorescent in situ hybridization (FISH)

Türkiye'de optimum maliyete dayalı atıksu arıtma tesisi tasarımı

Besides the civilization process, the economic conditions of Turkey make realization of the most of the investment necessary for urbanization, impossible.  One of the strongest examples of this is the inadequacy of the wastewater collection and treatment systems in our cities. It is an absolute necessity of the life in a city that the discharged water shall be collected, treated and disposed to the receiving bodies afterwards, without any damage. Therefore; determination of the treatment method for each population range, based on optimum cost and application, provides most convenient use of the already limited financial resources of our country, considering the variable populations of around 3,000 municipalities, which do not have a wastewater treatment plant. In this study, a standard method for the design and establishment of a wastewater treatment plant process, base on optimum cost for the settlement populations ranging between 5,000 people up to 2,000,000, will be proposed. In the determination of this method the most convenient processes of the available treatment processes have been studied based upon the analyses, carried in all population ranges in the consideration of the laws and regulations currently in force, unit wastewater formation with respect to population and wastewater characterization. The investment amounts obtained, and main operational costs have been analyzed and the most convenient treatment technology has been proposed for each of population range. Keywords: Wastewater, finance and optimization of wastewater treatment plant, unit treatment cost.   Türkiye’de atıksu arıtma tesisi olmayan yaklaşık 3 000 belediyenin değişken nüfus değerleri dikkate alındığında her biri için optimum maliyete dayalı arıtma yönteminin belirlenmesi ve uygulanması kısıtlı finansman kaynaklarının uygun biçimde kullanılmasını sağlar. Bu çalışmada nüfusu 5 000 ile 2 000 000 arasında değişen yerleşim birimleri için optimum maliyete dayalı atıksu artıma tesisi prosesinin belirlenmesine çalışılmış ve tasarımı için bir standart yöntem önerilmiştir. Bu yöntemin belirlenmesinde mevcut kanun ve yönetmelikler, nüfusa bağlı birim atıksu oluşumu ve atıksu karakterizasyonu, bütün nüfus değerleri için hesaplara temel alınmıştır. Mevcut arıtma proseslerinin uygun olanları denenmiş, elde edilen yatırım maliyetleri ve ana işletme giderleri, finansman hesaplarından değerlendirilerek, her nüfus aralığı için birim atıksu miktarı başına en düşük maliyeti getiren arıtma teknolojisi optimum yöntem olarak önerilmiştir.  Anahtar Kelimeler: Atıksu, atıksu arıtma tesisi finansmanı ve optimizasyonu, birim arıtma maliyeti. &nbsp

Ozonation application in activated sludge systems for a textile mill effluent

The study investigates the effect of partial ozonation of textile wastewater, both at the inlet (pre-ozonation) and the outlet (post-ozonation) of biological treatment, for the optimization of COD and color removals, both typical polluting parameters associated with the textile industry. Pre-ozonation provides at optimum contact time of 15 minutes 85% color removal, but only 19% COD reduction. Removal of the soluble inert COD fraction remains at 7%, indicating selective preference of ozone for simpler compounds. Post-ozonation is much more effective on the breakdown of refractory organic compounds and on color removal efficiency. Ozonation after biological treatment results in almost complete color removal and a 14% soluble inert COD reduction. The polishing effect of post-ozonation also proves quite attractive from an economical standpoint, involving approximately 50% of the ozone utilization at the same ozone flux rate and contact time, yet providing a lower soluble residual COD level

Wastewater reuse for the minimization of fresh water demand in coastal areas—selected cases from the textile finishing ındustry

Availability of water to the industry often becomes prohibitive, both in terms of quality and cost, in coastal areas. This study takes the textile industry and evaluates the prerequisites of water recovery and reuse. In this context, a large spectrum are studied for their water, the general quality of wastewater generated, quality and treatability of reuse wastewater streams, and expected changes in the overall effluent quality after segregation of the recovery wastewater portion

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

Nitrifikasyon-denitrifikasyon kinetiğinin deneysel karakterizasyonu

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1995Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1995Atıksu arıtma süreci incelendiğinde, yalan geçmişe kadar yürütülen biyolojik arıtma çalışmalarının daha çok organik karbon giderimine yönelik olduğu, azotlu bileşiklerin giderilmesi ile pek fazla ilgilenilmediği görülmektedir. Azotlu bileşiklerin alıcı ortamlarda sebep oldukları zararlı etkiler nedeniyle azot giderimine ancak son yıllarda Önem verilmeye başlanmış, karbon-azot gideriminin birlikte gerçekleştirildiği biyolojik nitrifikasyon-denitrifikasyon sistemlerinin en ekonomik çözüm olarak ortaya çıktığı görülmüştür. Bu sistemlerin yaygın olarak kullanımı nitrifikasyon-denitrifikasyon mekanizmalarının kinetik esaslarının ve sistem bileşenlerinin ortaya konmasını gerektirmektedir. Bu çalışmada nitrifikasyon-denitrifikasyon mekanizmalarının kinetik esaslarının araştırılması, ototrof ve heterotrof organizmaların maksimum çoğalma hızlarının belirlenmesi ve sistem bileşenlerinin ortaya konması hedeflenmiştir. Bu hedef doğrultusunda istanbul evsel atıksuyu, sentetik atıksu ve endüstriyel atıksular (et, süt, şekerleme endüstrileri) ile deneysel çalışmalar yürütülmüştür. Birinci bölümde genel olarak azotlu bileşiklerin alıcı ortamlarda yarattığı problemler üzerinde durulmuş, çalışmanın amaç ve kapsamı tanımlanmıştır. İkinci bölümde nitrifikasyon ve denitrifikasyon mekanizmalarının esasları detaylı olarak ele alınmış, stokiometrik ve kinetik ifadeleri ortaya konmuştur. Geniş bir literatür araştırması ile bu konuda yapılmış olan çalışmalar hakkında bilgi verilmiştir. Üçüncü bölümde ototrofik ve heterotrofik mikroorganizmaların maksimum spesifik çoğalma hızlarının belirlenmesi için kullanılan yöntemlerin kritiği yapılmış ve bu mevcut yöntemlerin deney ve değerlendirme aşamasında uygulanacak bazı değişiklikler ile geliştirilmesi önerilmiştir. Dördüncü bölümde ototrof ve heterotrof organizmalar ile yürütülen deneysel çalışmanın düzeni ve analiz yöntemleri açıklanmıştır. Beşinci bölümde ototrof ve heterotrof organizmalar ile çeşitli atıksularda yürütülen deneylerin sonuçlan detaylı olarak verilmiştir. Altıncı bölümde deney sonuçlan atıksu bazında değerlendirilmiş, literatürde mevcut olan veriler ile karşılaştırılmıştır. Yedinci bölümde sonuçlar ve öneriler tartışılmıştır.Wastewaters are treated to a great extent mainly by biological wastewater treatment systems before being discharged in receiving waters. The system most commonly used is the activated sludge. Until 1970's these systems were designed and operated only for the removal of organic carbon. The observations and experience indicate that removal of organic matter is not enough to solve all the problems encountered in maintaining the quality of receiving waters for specific benefical uses. Most of these problems, such as eutrophication, excess depletion of oxygen, fish toxicity, etc., are readily associated with particular forms of nitrogen. Nitrogenous materials may enter the aquatic environment from either natural or man-caused sources. Natural sources of nitrogenous materials include precipation, dustfall, nonurban runoff and biological fixation. Man-caused sources may be listed as runoff from urban areas, subsurface drainage from agricultural lands, municipal and industrial wastewaters. Various forms of nitrogen present in a wastewater discharge can be undesirable in receiving waters for several reasons: as free ammonia, it is toxic to fish and many other aquatic organisms; as ammonium ion or ammonia, it is an oxygen-consuming component which will deplete the dissolved oxygen in receiving waters; in all forms, nitrogen will be available as a nutrient to aquatic plants and consequently contribute to eutrophication; as the nitrate ion, it is a potential public health hazard in water consumed by infants. On the basis of scientific evidence provided, nitrogen control has become increasingly important in water quality management. This new approach also triggered efforts to explore the merit and the potential of biological treatment, especially the activated sludge process, as a biochemical tool to secure the necessary conversion and removal of nitrogen forms. Nitrogen naturally exists in various compounds with a valence ranging from -3 to +5. Transformations of the nitrogen forms resulting in valence changes are associated with metabolic activities of different types of organisms. Oxidation of ammonia first to nitrite (N02~) and then to nitrate (N03~) is called nitrification, which is carried out by the autotrophic species Nitrosomonas and Nitrobacter, respectively. Conversely, the reduction of nitrate to molecular nitrogen by heterotrophic microorganism species is named denitrification. The effluent guidelines and standarts to protect the receiving waters promote nitrification- denitrification as a very feasible treatment process capable of ensuring the necessary level of conversion and removal of nitrogen forms. xvii For design and operation of a nitrification-denitrification system achieving simultaneous carbon and nitrogen removal, different mathematical models are used. Development of these models requires a complicated conceptual approach. It involves identification of all carbonaceous and nitrogenous components, correct assessment of the stoichiometric relationships between those components, and definition of the rate expressions for all the aerobic and anoxic processes. Within the framework of this study, the most critical design parameters in nitrification-denitrification process are experimentally surveyed along with the conventional characterization and COD fractionation for i) Istanbul domestic sewage, ii) synthetic waste, iii) a meat processing plant effluent, iv) a dairy effluent, v) a confectionary effluent, vi) different combinations of domestic-synthetic and domestic-industrial wastewaters. The critical design parameters considered include maximum spesific growth rate for autotrophic and heterotrophic biomass, correction factors for anoxic conditions and endogenous respiration rate. Maximum Specific Growth Rate for Autotrophic Biomass The maximum specific growth rate for autotrophic biomass, jxA is the most critical parameter in the modelling and design of nitrification systems, as it plays a dominant role on the magnitude of the washout sludge age for nitrifiers. The value of this kinetic coefficient is very much dependent on wastewater characteristics; therefore, it should be determined specifically for the wastewater of interest. Activated sludge reactors designed for nitrification utilize a mixed culture of heterotrophic and autotrophic biomass. For this reason, experimental techniques developed for pure cultures and relying on the evaluation of autotrophic growth by direct measurements of nitrifiers cannot be used for such systems. For suspended growth biological nutrient removal systems, the generally adopted approach is to determine (xA by monitoring the concentration of oxidized nitrogen, S^ in batch reactors, mainly because S^ is the only parameter solely related to autotrophic growth and batch systems offer a simpler interpretation of the reaction kinetics for experimental evaluation. Based upon the growth kinetics of nitrifying biomass, the following expression is applicable for the kinetic description of such systems: where SNO0 is the initial Nox concentration at the beginning of the test, X^ is the concentration of autotrophic biomass initially added to the reactor, YA is autotrophic yield coefficient and bA is autotrophic decay coefficient. Since X^, YA and bA xvni cannot be separately determined during the experiment, it may be convenient to use an experimental setup with sufficiently low values of S^ and X^ so that the related terms may be neglected (Antoniou et al., 1990). In this case, the above expression may be expressed in the following linear form: In S" = In ^^- XA + (fi.A - bA) t (2) YA VA ~bA The value of £iA - bA is then obtained as the slope of this linear function; jxA is then estimated with a reasonable assumption for bA. However, a careful evaluation of this method shows that it is not generally mathematically justifiable to accept the simplifying assumptions leading to the above procedure, because (i) even for very low Sjjoo and X^ values, the initial concentration of oxidized nitrogen and the term including XA0 will not be equal and cancel out, and (ii) neglecting SNO0 as an initial condition will lead to the same values for the slope of the linearized expression at different temperatures. Within the framework of this study, the proposed new approach defines a "curve fitting" procedure in order to minimize the errors in the determination of jxA with the same experimental data. For this new procedure, expression (1) is arranged to yield: AA0 &A By setting, Y. û. - b.... k = -± LA ± (4) XA0 ftl the following logarithmic expression is obtained; k K5» " Ssoo) * + 1] = (A, - bA) t (5) In this expression k is a constant for a given experimental setup. The value of jxA-bA with the highest correlation coefficient is then computed using a search technique known as the Fibonacci search with different values for k. Experiments were conducted in batch reactors seeded with an initial biomass concentration of around 50 mg SS/1 from a mixed culture of the fill and draw unit operated at a sludge age of 10 days. The proposed method is successfully tested on Istanbul domestic sewage and on a synthetic substrate to depict possible inhibition effects. Similar studies are also carried out alone on samples from a meat processing plant effluent and on different combinations with domestic sewage. Characteristics Associated with Respirometric Measurements In this study, respirometric procedures, based on OUR (Oxygen Uptake Rate) and NUR (Nitrate Uptake Rate) measurements in batch reactors were adapted to assess xix the maximum specific growth rate of heterotrophic biomass under aerobic and anoxic conditions. The data of the same test were also used to calculate the readily biodegradable COD fraction. The most important point in NUR experiments is to measure the reduced electrons from nitrate to nitrogen gas, as an accurate representation of the amount of oxidized substrate. Any accumulation of nitrite means, that the second step of the denitrification process is stopped somehow and electrons used up in this step (3/5 electrons) can not be further transferred. To determine the real electron transfer rates under anoxic conditions the nitrate uptake rates should be corrected as AN03~-N- 0.6 AN02"-N. Comparing the results of the OUR method mentioned above with another procedure, which gives £H independent from XH, also based on OUR measurement the active fraction of biomass was calculated. The NUR measurements were also used to calculate denitrification rates. Endogenous respiration rate was determined with OUR measurements. Maximum Specific Growth Rate for Heterotrophic Biomass A respirometric method for the evaluation of (% has been developed by Ekama and Marais (1986). It is the procedure involving an aerated batch reactor where a preselected volume of wastewater, V^, is mixed with a preselected volume of mixed liquor, V^, having a total biomass concentration of XT'. Neglecting the endogenous respiration, the initial level of OUR observed in the test, OURj [mg 02/l.h] is proportional to u,H as indicated by the following expression: £" = J*_ OUR. (V"*+Vww) 24 hid (6) where yield coefficient YH is expressed as [mg VSS/mg COD]. The same procedure is also applied to an anoxic batch reactor to determine the specific growth rate of denitrifiers. The only difference is the electron acceptor, nitrate nitrogen. Nitrate respiration measurements are carried out in a closed reactor. 2.86 y" (V^+VwJ ÇLm = £ NUR, - * - T 24 hid (7) 1 *h L XTV, ml Both expressions include the active fraction of the mixed liquor, fa, which must be previously known. Some procedures are described for the estimation of this fraction. On the other hand Kappeler and Gujer (1992) developed another aerobic procedure independent of XH which involves a batch test with centrifuged wastewater and a very small amount of biomass corresponding to an initial COD/VSS ratio of 4. A linear relationship is defined between the logarithms of relative OUR (OUR/OURq) and time, with the slope equal to jxH-bH. xx (£" - bH) t =ln [2HEl] (8) \rH "j l0URQ In this study the endogenous respiration is neglected to make both procedures similar to each other. a t = In [-^] (9) Upon equalization of both expressions (6 and 9) the active fraction can be obtained as fallows; f = _?_ OURx K « v** 24 hid (10) I-?* û Xi V Correction Factors for Anoxic Conditions Two important parameters, T]g and %, reflect changes in the rates of microbial growth and substrate utilization when the system is switched from aerobic conditions to anoxic conditions. These values can be estimated by measuring OUR and NUR in two parallel tests. Tig is defined as a ratio of maximum specific growth conditions, whereas îih indicates the ratio of hydrolysis phases. ûT NUR,"",. T] = rSB. = 2.86 I (11) * A* OUR, NUR. Tj = 2.86 * (12) * OURh Readily Biodegradable COD In the aerobic batch test, the OUR initially measured is associated with both readily and slowly biodegradable substrate in the sewage sample and endogenous respiration. The initial OUR may stay constant during a certain time where the readily biodegradable substrate S^ is high enough to sustain maximum growth rate, with the selection of a suitable F/M ratio. After the consumption of S^, the OUR is expected to drop to a lower level. At this time OUR is correlated only to hydrolysed substrate and endogenous respiration. The readily biodegradable substrate S^, in the wastewater is calculated with this relationship: Sso = 7V A° (13> XXI where AO is the difference between total respiration and respiration due to hydrolysed substrate and endogenous metabolism. The same parameter may also be calculated from the corrected N03"-N profile in the anoxic reactor. In this test, the initial N03"-N utilization is faster, due to oxidation of readily biodegradable substrate. The amount of N consumed during this period, if corrected for the interference of the hydrolysed, substrate may be used to calculate Sso with the following relationship: 1 lH Endogenous Respiration Rate In a batch aerobic digester, under endogenous decay conditions containing no external substrate, OUR = IAS (l-fE)bHXH (15) and X = X e'*"»1 (16) AH AH0 e V / Substituing the value of XH above, In OUR = In [1.48(1 -fj bH Xm) - bH t (17) shows that the slope of a plot of In OUR versus time yields the value of 1%. Results of Istanbul Domestic Sewage The experimental survey program to characterize the Istanbul domestic sewage was carried out approximately 3 years including the experiments with autotrophs and heterotrophs. The results show that for raw sewage, average concentrations of 560, 64, 43 and 11 mg/1 can be associated with COD, TKN, NH4+-N and TP parameters respectively; the corresponding COD/N ratio is computed as 8.8. The maximum specific growth rate of nitrifiers was experimentally determined for 12 domestic sewage samples selected to represent different wastewater properties. The results show that jlA - bA levels at 20 °C were highly variable within a range of 0.24-0.52 d~\ with an average value of 0.38 d"\ No correlation was possible or justifiable between jxA-bA values and any of the conventional parameters characterizing domestic sewage samples. At 10 °C, which is the critical wastewater temperature in winter for the design of treatment systems, the average value of ftA-bA was observed to drop to 0.14 d"1, approximately one third the level associated with 20 °C and its variation for different sewage samples stayed within a narrower xxn range of 0.10-0.17 d"1. The results obtained also confirm the validity of this expression yielding an average value of 1.098 for the temperature coefficient, 6, quite in accordance with the range of 1.08-1.123 reported in the literature. Experiments which have been carried out with synthetic substrate parallel to domestic sewage reactors to evaluate the existence and the extent of inhibitors indicate similar levels of ftA-bA in the range of 0.25-0.52 d"1. These observations lead to the conclusion that inhibition, if present, is of no practical importance for Istanbul domestic wastewaters. It is determined that the maximum specific growth rate for heterotrophic growth rate [% of Istanbul domestic wastewater vary in the range of 2.7-6.5 1/day, with an average of 4.6 1/day. For anoxic conditions, values of around 0.88, consistently calculated for r\h are significantly higher than the level typically suggested for this parameter by the IAWPRC Task Group (Henze et al., 1987), but support the findings of Oles and Wilderer (1991) and Kristensen et al.(1992). An average value of T|g 0.59 is calculated. Readily biodegradable substrate Sso is calculated to vary in the range of 12-92 mg COD/1 with an average of 50.5 mg COD/1 on the basis of NUR test; the aerobic test yielded an average value of 50 mg COD/1 within a range of 21-86 mg CODA. The readily biodegradable fraction is around 9%. The denitrification rates in maximum growth, hydrolysis and endogenous decay phases are calculated 0.029, 0.014 and 0.010 mg N/mg VSS.h on the basis of active biomass, respectively. The endogenous decay rate is determined as 0.24 1/day. Additionally, experiments with domestic-synthetic waste mixtures were carried out to investigate the impact of S^ on OUR and NUR measurements. Syntetic waste as defined by Henze (1992) represents the readily biodegradable substrate in domestic sewage. This part of the study indicated that S^, externally added, could be recovered successfully with the electron uptake rate measurements. Results of the Meat Processing Plant Effluent The characterization program of the meat processing plant effluent was carried out for approximately 6 months including the experiments with autotrophs and heterotrophs. The results show that for raw sewage, average concentrations of 2130, 158 and 80 can be associated with COD, TKN and NH/-N parameters respectively; the corresponding COD/N ratio is computed as 13.5. Experimental assessment of ftA for this industrial wastewater was also realized with a monitoring program extended over three months. A point of interest in connection with this evaluation is the observation that the meat processing wastewater yields xxm markedly higher p,A- bA values as compared to domestic sewage. The average flA- bA level for the meat processing effluent is 0.59 d"1 at 20°C, 80 % higher than 0.32 d"1 calculated as the average value for domestic sewage at the same temperature. The same observation remains also valid for the experiments at lower temperatures: At 10 °C for example, average values of 0.28 d"1 and 0.13 d"1 have been found to characterize this coefficient for the meat processing waste and domestic sewage, respectively. Another significant observation relates to the experiments conducted on mixtures of sewage and meat processing wastes, where the meat processing waste appeared to control the rate of nitrification with a higher autotrophic activity. The maximum specific growth rate of heterotrophs is determined to be 3.8 1/day (average) within a range of 3.6-4.2 1/day. The t|g and T|h values are both calculated as 1.5, greater than 1, which is the maximum value given in literature. Sgo varies in the range of 304-416 mg COD/1 with an average value of 374 mg COD/1 on the basis of NUR test. The readily biodegradable fraction is around 16%. The denitrification rates in maximum growth, hydrolysis and endogenous decay phases are calculated 0.064, 0.027 and 0.016 mg N/mg VSS.h on the basis of active biomass, respectively. Results of the Dairy Industry Effluent The results show that the influent to biological process has average concentrations of 1745, 75 and 23 can be associated with COD, TKN and NH/-N parameters respectively; the corresponding COD/N ratio is computed as 23. The maximum specific growth rate of heterotrophs is calculated to be 3.1 1/day (average) within a range of 2.9-3.3 1/day. The T|g and T|h values are both determined greater than 1, as 1.02 and 2.25, respectively. Sgo is calculated in the range of 394-425 mg CODA with an average value of 406 mg CODA on the basis of NUR test. The readily biodegradable fraction is around 23%. The denitrification rates in maximum growth, hydrolysis and endogenous decay phases are calculated as 0.079, 0.039 and 0.028 mg N/mg VSS.h on the basis of active biomass, respectively. The endogenous decay rate is determined as 0.14 1/day. xxiv Results of the Confectionary Industry Effluent The wastewater taken from the influent of a biological system analized for conventional parameters. The results show that average concentrations of 3790 and 13 and 23 can be associated with COD and TKN parameters respectively, with a COD/N ratio of 292. The purpose of the NUR measurements in this part of the study is to outline the denitrification potential in a possible common treatment scheme where it is handled together with a domestic sewage or a wastewater with a high nutrient content. (Ih is calculated as 4.1 1/day, r\s and % values are determined 0.86 and 1.7 respectively. Sgo is calculated with an average value of 720 mg COD/1 on the basis of NUR test. The readily biodegradable fraction is around 19%. The denitrification rates in maximum growth, hydrolysis and endogenous decay phases are calculated to be 0.111, 0.074 and 0.006 mg N/mg VSS.h on the basis of active biomass, respectively. The endogenous decay rate is determined as 0.24 1/day. The experimental results summarized above pro

Pollutant footprint analysis for wastewater management in textile dye houses processing different fabrics

BACKGROUND: This study investigated the water and pollution footprints of a dye house, which processed cotton knits, polyester (PES) knits and PES-viscose woven fabrics. Experimental evaluation was carried out for each processing sequence. Variations in wastewater flow and quality were established as a function of the production program in the plant. A model evaluation of wastewater dynamics was performed and defined specifications of an appropriate treatment scheme. RESULTS: The plant was operated with a capacity of 4300 t year−1 of fabric, which generated a wastewater flow of 403 500m3 year−1 and a COD load of 675 t year−1. The overall wastewater footprint of the plant was computed as 91m3 t−1 and the COD footprint as 160 kg t−1 of fabric. Depending on the fabric type, results indicated expected changes in wastewater flow between 600 and 1750m3 day−1 in COD load between 1470 and 2260 kg day−1 and in COD concentration between 1290 and 3400mgL−1. CONCLUSION: A model simulation structured upon COD fractionation and related process kinetics revealed partial removal of slowly biodegradable COD, coupled with high residual COD, which would by-pass treatment. Resulting biodegradation characteristics necessitated an extended aeration system, which could also enable partial breakdown of residual COD. Effluent COD could be reduced to 220–320mgL−1 with this wastewater management strategy. © 2018 Society of Chemical Industr

Effect of chemical treatment on soluble residual COD in textile wastewaters

The effect of chemical treatment on the magnitude of soluble residual COD in the biological treatment effluent is investigated for knit fabric finishing wastewater. Bentonite is selected for its potential to remove soluble COD together with color and particulate components. Chemical treatment using bentonite, when applied prior to biological treatment removes around 40% of the biodegradable as well as soluble inert COD initially present in the wastewater. As a chemical post-treatment, it acts as a polishing step, removing particulate matter and a minor portion of around 20% of the remaining soluble COD. These findings suggest chemical pre-treatment as a better alternative for the optimization of soluble COD removal