Stakeholders’ views on improving the organic certification system: Results from an EU level workshop

The FP7 CERTCOST project has the overall objective to give recommendations to the public authorities and private actors in the whole organic certification chain on how to improve the organic food certification systems in terms of efficiency, transparency and cost effectiveness. According to the project description (the Description of Work, or DoW) this will be done based on a scientific economic in depth analysis of the certification systems from the farmer to the consumer in 5 EU countries (the Czech Republic, Denmark, Germany, Italy and the United Kingdom), plus Switzerland and the candidate country, Turkey. To safeguard that the CERTCOST objectives, work plan and methodology is in line with the expectations of key stakeholders from all levels of the certification chain the DoW foresaw a Stakeholder workshop to be organised in the beginning of the project. The current report documents the main points of the discussions and recommendation given by the stakeholders at this CERTCOST Stakeholder workshop, which took place on November, 13-15, 2008 in Izmir, Turkey, 2.5 months after the project had started. A total of 20 stakeholders were invited, of whom 16 could participate in the workshop. The participant profile included both users and providers of the certification system at different levels such as representatives of farmers’ organizations certification/control bodies, government authorities, EU Commission, processors/ traders, private experts/consultants. Together with the representatives of the partner institutions in the CERTCOST project, the total number of workshop participants was 35 representing 12 European countries. Given the diverse backgrounds of the workshop participants, a working group approach (World Café approach) was applied in order to give the participants the opportunity to reflect their experiences and ideas on the implementation of the project in a synergetic, comfortable and free environment. After a brief presentation of the project, outlining the tasks of the work packages and describing the proposed links between the project and the stakeholders by the project coordinator, the stakeholders were divided into four groups according to their level in the organic certification chain, as farmers, processors/traders, certification bodies and consumers. Two working group sessions were carried out around the questions provided to the stakeholders before the workshop through electronic mails. The questions had been compiled based on input from the managers of the four work packages which were relevant to the workshop discussion. After the first working group session, a plenary discussion session for clustering of the output given by the working groups, their validation and assessment was carried out. In the second session of the working groups, it was rather aimed to harmonize the understanding between the diversified opinions mentioned in Session 1. The working group approach concluded in a final plenary discussion. On the second day, the CERTCOST work package managers presented how the discussions, comments and inputs of the working group sessions could impact on their working plans. In the final session the stakeholders were addressed directly for providing further ideas both on the project and on future collaboration options. The workshop was strongly focused on the identification of key characteristics of cost factors along the supply chain in relation to their impact on the quality of the given service. However a broad range of related subjects were discussed. The Stakeholder workshop put forward that, the ‘cost’ was among the most important topics relating to the certification system performance. The focus of the project aiming at cost effectiveness and not cost minimization was confirmed by the stakeholders. All of the stakeholders present in the workshop demonstrated elevated levels of interest on several outputs of the project. The workshop revealed very positive expectations among the stakeholders towards the risk based approach to be followed in the CERTCOST project. The detailed picture of the organic certification sector obtained through the workshop will constitute an important input to the CERTCOST project and the workshop is considered to be a successful first step in the project-stakeholder interaction. The Stakeholder workshop provided important insight into the many discussion subjects of the organic certification systems in the EU and worldwide, among others the following should be mentioned. Farmers expect to have, clear rules, fair implementation, and high skilled guidance in the inspection and certification process, and underline the need for training of farmers and certifiers and for better communication between all parties in the certification chain. Processors point out the need for a good relationship with the inspectors and certifiers as well as the fact that there existed different schemes in different countries regarding the inspection process and the related cost structure. They also highlighted the difficulty of managing the relations with increasing number of different standards and different certification bodies. It is agreed that consumers expect something they can trust and they can easily recognize, a label, a logo, a certifier, a brand, a farmer or the word ‘organic’; at local, regional, national, or EU-level. It is also concluded that whether, why and how much some consumers might be willing to pay more for particular logos was unknown and was needed to be investigated. Authorities/certification bodies stress that the issue of knowledge and education is extremely important and that there are complex legislations, no common standards, and differences within and between countries. They underline that there are different catalogues in different countries to deal with irregularities which should be harmonized. They emphasize that a clear definition of certification should be made covering its objectives, principles and tools. While on some of the issues there has been a highlighted consensus among the groups, on some others contrasting ideas became evident. Among those subjects of absolute agreement were the importance of and the need for a more clear understanding of the certification system, its components and rules by all the parties involved. Education and elevated levels of necessary skills from farmer to inspector and to consumer; increased transparency and information exchange, well defined relationships between parties were considered to be an indispensable basis for a well functioning and more efficient certification system. The inspection concept came into prominence, with a discussion on policing vs. development approaches. While an efficient and comparable control system was judged to be crucial, promising private governmental formulations were agreed to be based on country conditions. Complexity of the legislation and lack of transparency were the remarkable barriers to a more efficient control system. The EU logo and the new EU Regulation for organic certification were also discussed among stakeholders. It was suggested that the EU logo might have the potential to boost demand in the ‘less developed’ organic markets, but more promotion then currently planned would be needed. It was agreed that most consumers do not look for logos of particular standards but for the word ‘organic’ and/or an organic logo they are familiar with. This might be different for ‘committed’ organic consumers in more mature markets. Overall, it was agreed that ‘trust’ is the most crucial aspect of organic certification regarding the consumer side. The issue of multiple certification and standards appeared to be a factor deserving more attention in the certification world. Harmonization in certification of the same characteristic of a product was deemed necessary. On the other hand, exchange of experiences and cooperation with markets like ‘Fair Trade’ was agreed to be potentially beneficial

The Relation among retail price main of consumption center of fruit and vegetables and Region of Mediterranean (Turkey) : Test of Market Integration

Spatial price differentials for selected fresh fruits and vegetables, among six cities of Turkey, namely, Adana, Mersin, Antalya, important production centers, and İstanbul, Ankara and İzmir, main consumption centers, were investigated. The relations among retail prices of different cities were analyzed using Vector Auto Regression (VAR) models for each product. The existence or not, and the level of integration -in the affirmative case- among city markets regarding each product were tried to be analyzed using Ravallion’s dynamic analysis method of the market integration. Monthly data used are the retailer price series from 1994 to 2004, obtained from DIE for each of the cities. Retail prices of lemons, lettuce and tomatoes are considered as representative of fresh fruits and vegetables market. Results of the VAR model for lemons market revealed that Adana was the leader market, and that the prices of the other cities were dependent on those of the leader. The highlighted leader position of Adana in this market permitted the dynamic analysis method of market integration suggested by Ravallion to be applied in the lemons market. As the result, long-run market integration with Adana for three out of five local markets was detected. In the lettuce market, on the other hand, the VAR model suggested the retail prices in each city to behave fairly independently from each other. Regarding tomato prices, even though virtual influence of Antalya on other cities was identified examining the impulse response functions (IRF) and the variance decomposition obtained from the VAR model, Adana and Mersin were also observed to have their respective regions of impact. The level of leadership assigned to Antalya in tomatoes market was not highlighted enough for dynamic analysis of integration.Var model, Market Integration, Fruit and vegetables, Retail Price, Region of Mediterranean

Akdeniz Bölgesi ve Başlıca Tüketim Merkezlerinde Yaş Meyve ve Sebze Perakende Fiyatları Arasındaki İlişkiler: Pazar Entegrasyonunun Testi

Spatial price differentials for selected fresh fruits and vegetables, among six cities of Turkey, namely, Adana, Mersin, Antalya, important production centers, and İstanbul, Ankara and İzmir, main consumption centers, were investigated. The relations among retail prices of different cities were analyzed using Vector Auto Regression (VAR) models for each product. The existence or not, and the level of integration -in the affirmative case- among city markets regarding each product were tried to be analyzed using Ravallion’s dynamic analysis method of the market integration. Monthly data used are the retailer price series from 1994 to 2004, obtained from DIE for each of the cities. Retail prices of lemons, lettuce and tomatoes are considered as representative of fresh fruits and vegetables market. Results of the VAR model for lemons market revealed that Adana was the leader market, and that the prices of the other cities were dependent on those of the leader. The highlighted leader position of Adana in this market permitted the dynamic analysis method of market integration suggested by Ravallion to be applied in the lemons market. As the result, long-run market integration with Adana for three out of five local markets was detected. In the lettuce market, on the other hand, the VAR model suggested the retail prices in each city to behave fairly independently from each other. Regarding tomato prices, even though virtual influence of Antalya on other cities was identified examining the impulse response functions (IRF) and the variance decomposition obtained from the VAR model, Adana and Mersin were also observed to have their respective regions of impact. The level of leadership assigned to Antalya in tomatoes market was not highlighted enough for dynamic analysis of integration

Biochemical basis and modeling of oxygen requirement in activated sludge

Bu çalışmada, aktif çamur sistemlerinde oksijen tüketimi, değişik biyokimyasal dönüşümleri yansıtan temel süreçler yardımı ile belirlenip modellenmiştir. Modellemede, sübstrat kullanımı ve biyokütle oluşumu esas alınmıştır. Oksijen tüketimini belirten ifadelerde sübstrat ve biyokütlenin tanımı için kullanılan değişik parametre çiftleri kullanılmıştır. Kullanılan modellerin kinetiği ve stokiyometrisi matris formatında her parametre çifti için ayrı ayrı tanımlanmıştır. Oksijen tüketimi için geçerli olan değişik ifadeler bu modellere göre türetilmiş ve bu yaklaşımla literatürde verilen benzer tanımların biyokimyasal temelleri ortaya konmuştur. İncelemede, Türkiye’de aktif çamur tesislerin tasarımında oksijen gereksiniminin hesaplanması için yönetmeliklerde kullanılması önerilen ifadeler de ele alınmış ve bu ifadelerdeki katsayıların geçerliliği değerlendirilmiştir.  Anahtar Kelimeler: Aktif çamur, biyokütle, modelleme, oksijen gereksinimi, sübstrat.In this study, oxygen requirement in activated sludge is evaluated and modelled in terms of fundamental  processes reflecting different biochemical transformations. Modern modeling concepts define substrate  utilisation and endogenous decay as major processes requiring final electron acceptor. In aerobic systems, dissolved oxygen acts as, and therefore, is consumed as the final electron acceptor. Substrate and biomass may be defined in terms of different parameters. Chemical oxygen demand (COD) and biochemical oxygen         demand (BOD5) are the traditional substrate parameters. COD also serves to define biomass along with the more traditional volatile suspended solids (VSS) parameter. Model alternatives covering basic biochemical processes in activated sludge are defined in a matrix format for different substrate and biomass parameters, each associated with a different stoichiometry. These modeling alternatives are used to derive different       oxygen requirement expressions, all compatible among themselves, for each substrate/biomass couple. The biochemical bases of the coefficients in these expressions are set in terms of fundamental model constants. As a practical implication of the conceptual evaluation approach, this study also covers a critical appraisal of formulations proposed in the regulations implemented by the authorities in Turkey, for the evaluation of the oxygen requirements in activated sludge design. Keywords: Activated sludge, biomass, modeling, oxygen requirement, substrate

Akdeniz Bölgesi ve Başlıca Tüketim Merkezlerinde Yaş Meyve ve Sebze Perakende Fiyatları Arasındaki İlişkiler: Pazar Entegrasyonunun Testi

Spatial price differentials for selected fresh fruits and vegetables, among six cities of Turkey, namely, Adana, Mersin, Antalya, important production centers, and İstanbul, Ankara and İzmir, main consumption centers, were investigated. The relations among retail prices of different cities were analyzed using Vector Auto Regression (VAR) models for each product. The existence or not, and the level of integration -in the affirmative case- among city markets regarding each product were tried to be analyzed using Ravallion’s dynamic analysis method of the market integration. Monthly data used are the retailer price series from 1994 to 2004, obtained from DIE for each of the cities. Retail prices of lemons, lettuce and tomatoes are considered as representative of fresh fruits and vegetables market. Results of the VAR model for lemons market revealed that Adana was the leader market, and that the prices of the other cities were dependent on those of the leader. The highlighted leader position of Adana in this market permitted the dynamic analysis method of market integration suggested by Ravallion to be applied in the lemons market. As the result, long-run market integration with Adana for three out of five local markets was detected. In the lettuce market, on the other hand, the VAR model suggested the retail prices in each city to behave fairly independently from each other. Regarding tomato prices, even though virtual influence of Antalya on other cities was identified examining the impulse response functions (IRF) and the variance decomposition obtained from the VAR model, Adana and Mersin were also observed to have their respective regions of impact. The level of leadership assigned to Antalya in tomatoes market was not highlighted enough for dynamic analysis of integration

Experimental assessment of substrate storage yield

Çevre biyoteknolojisindeki son gelişmeler doğrultusunda aktif çamur sistemlerinde substrat depolama kavramı önemli bir proses olarak kabul edilmektedir. Substrat depolama kavramı, aktif çamur modellemesine, Aktif Çamur Modeli No.3 (ASM3) ve saf substratlar için önerilen biyokimyasal modellerle dâhil edilmiştir. Depolama kavramının ortaya konması, modele çok fazla serbestlik derecesi sağlayarak, modeli daha karmaşık bir hale getiren pek çok kinetik ve stokiyometrik katsayının da eklenmesine yol açmıştır. Substrat depolama dönüşüm oranı, YSTO, ASM3 modelindeki en önemli parametrelerden biridir. Depolama dönüşüm oranı, substratın stokiyometrik olarak ne kadarının depolama ürünlerine dönüşeceğini belirleyen etkin bir model bileşenidir. Bu çalışma, ASM3 modelinde tanımlanan substrat depolama dönüşüm oranının (YSTO), deneysel olarak belirlenmesini amaçlamaktadır. Önerilen yöntem, atıksularda depolama ürünlerinin miktarlarının belirlenmesini gerektirmeyen, respirometrik bir prosedürdür. Yöntemde, model simulasyonlarından yararlanılarak, depolama prosesi için tüketilen oksijen miktarının oksijen tüketim hızı (OTH) eğrisi üzerinde belirlenmesinin esasları ortaya konmuştur. Önerilen yaklaşım kesikli deneylerle elde edilen oksijen tüketim hızına (OTH) dayanmaktadır. Yöntem substrat depolaması için kullanılan oksijen miktarının hesaplanması için grafiksel bir metot tanımlamaktadır. Yöntemin değerlendirilmesi için farklı deneysel başlangıç koşullarının kullanıldığı model simülasyonlarından yararlanılmıştır. Önerilen yöntem ile YSTO değeri %2’den daha düşük hata oranları ile belirlenebilmiştir. Deneysel yöntem ile, asetat, glikoz ve evsel atıksuyun kullanıldığı ve farklı F/M oranlarında yürütülen respirometrik testler sonucunda, depolama dönüşüm oranları, asetat için 0.78 gKOİ/gKOİ, glikoz için 0.87 gKOİ/gKOİ ve evsel atıksu için 0.96 gKOİ/gKOİ olarak belirlenmiştir. Anahtar Kelimeler: Asetat, Aktif Çamur Modeli No.3, evsel atıksu, glikoz, respirometri, depolama.Substrate storage under dynamic conditions is recently regarded as a significant process for activated sludge systems. The dynamic conditions and substrate gradients convey activated sludge cultures to develop a storage response when external substrate is present in the system. Substrate storage is incorporated into activated sludge modeling with Activated Sludge Model No. 3 (ASM3) and with biochemical models for pure substrates. ASM3 has been proposed for activated sludge systems both for aerobic and anoxic conditions. Introducing storage phenomena has also introduced a number of stoichiometric and kinetic coefficients making the model rather complicated with many degrees of freedom. Some default values have been proposed, but calibration of kinetic and stoichiometric parameters is needed for various applications. The storage yield (YSTO) is one of the most important parameters of the model, since it represents the stoichiometric amount of substrate converted into storage products, which are subsequently utilized for growth. The assessment of YSTO is therefore crucial for the accurate estimation of the overall electron acceptor utilization and sludge production. The information on the magnitude of the storage yield was mostly derived from pure culture studies. ASM3 suggested value of YSTO as 0.85 mgCOD/mgCOD under aerobic  conditions for domestic sewage. An experimental procedure was developed for the respirometric determination of bacterial storage yield (YSTO) as defined in the Activated Sludge Model No. 3. The proposed approach is based on the oxygen utilization rate (OUR) profile obtained from a batch test and correlates the area under the OUR curve to the amount of oxygen associated with substrate storage. The procedure is based on respirometry and does not involve measurement of storage products, as it will not always be possible or reliable to determine the amount of all the storage products when a complex substrate such as domestic sewage is concerned. It is theoretically possible to compute substrate storage yield (YSTO) if the oxygen used for the storage of a known amount of readily biodegradable COD can be determined by means of respirometric measurements. Such measurements however only provide the total oxygen utilization rate (OUR) of the system and not the OUR specific for the process of interest alone. Thus, it is necessary to understand and interpret the components of a total OUR versus time curve associated with the utilization of a readily biodegradable substrate. Model simulation was used to evaluate the procedure for different initial experimental conditions. Obtained results indicated that the proposed procedure was quite consistent with model-input values, involving an error of less than 2%, aside from analytical errors associated with standard COD measurements, for tests to be conducted with feeding (F/M) ratios over 0.1 gCOD/g cellCOD. The procedure was used to determine the storage yield, YSTO, associated with acetate, glucose and domestic sewage, together with mixtures of acetate/glucose and acetate/domestic sewage at different initial F/M ratios. YSTO was calculated as 0.78 gCOD/gCOD for acetate, 0.87 gCOD/gCOD for glucose and 0.96 gCOD/gCOD for domestic sewage. The high YSTO level related to domestic sewage, consistently obtained for a wide range of initial F/M ratios, challenges the validity of the concept of SS in ASM3, which is defined as the biodegradable fraction of the soluble substrate and tested in the study. The assumption introduced with ASM3 that the entire soluble biodegradable COD could be regarded as readily biodegradable substrate, although valid for pure substrates, requires, as in this case, careful evaluation for wastewaters with more complex substrate compositions. If readily biodegradable substrate is actually less, the corresponding oxygen consumption can only be interpreted with a superficially higher YSTO. The experiments conducted on substrate mixtures confirmed the validity of YSTO values calculated for individual substrates, yielding a transient pattern reflecting the character of the dominant substrate fraction in the mixture. For glucose/acetate mixtures, they provided a clear indication of a faster storage rate for glucose as compared to acetate. The proposed procedure may also be used to calculate initial readily biodegradable COD concentration, SS1, for a generally adopted YSTO value, as it defines a stoichiometric procedure between the storage yield and the available readily biodegradable substrate. Keywords: Acetate, Activated Sludge Model No.3, domestic sewage, glucose, respirometry, storage

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

Treatment of surfactants by advanced oxidation processes: Process optimization and toxicity analysis

Bu çalışma kapsamında, ülkemizde ve dünyada ticari olarak önem taşıyan tekstil ve kimya başta olmak üzere pek çok endüstride yoğun olarak kullanılan ve çevrede yarattıkları olumsuz etkilerden dolayı önem taşıyan noniyonik (nonil fenol etoksilat), anyonik (dioktil sülfosuksinat) ve katyonik (kuaterner amonyum etoksilat) türü yüzey aktif maddelerin (YAM) Foto-Fenton ve H2O2/UV-C ileri oksidasyon prosesleri ile arıtılabilirlikleri incelenmiştir. Yapılan ön arıtılabilirlik deneyleri sonucunda, incelenen fotokimyasal ileri oksidasyon proseslerinin yüzey aktif maddelerin arıtımı için uygun ve etkin olduğu saptanmıştır. Yüzey aktif maddelerin fotokimyasal arıtımı için seçilen H2O2/UV-C ileri oksidasyon prosesi Cevap Yüzey Yöntemi kullanılarak ana madde, KOİ ve TOK giderimleri açısından modellenip, optimize edilmiştir. H2O2/UV-C prosesi ile yapılan arıtılabilirlik çalışmalarında giriş KOİ değerinin, reaksiyon süresinin ve H2O2 konsantrasyonunun (proses bağımsız değişkenleri) ana madde, KOİ ve TOK giderim verimleri (proses çıktıları/bağımlı değişkenleri) üzerindeki etkileri araştırılmıştır. Yapılan deneysel tasarım çalışmaları sonucunda proses çıktılarını bağımsız değişkenler cinsinden tanımlayan ikinci dereceden eşitlikler türetilip geçerlilikleri istatistiksel araçlar kullanılarak sorgulanmıştır. Yüzey aktif maddelerin H2O2/UV-C prosesi ile ileri oksidasyonunun Cevap Yüzey Yöntemi ile yeterli hassasiyetle modellenebildiği sonucuna varılmıştır. Farklı giriş KOİ değerleri için optimize edilen reaksiyon koşullarında yürütülen fotokimyasal oksidasyon deney sonuçlarının model çıktıları ile uyum gösterdiği gözlenmiştir. Çalışmanın son aşamasında ise yüzey aktif maddelerin ve fotokimyasal oksidasyon ürünlerinin toksisiteleri aktif çamur inhibisyon testi ile belirlenmiştir. Deneysel çalışma sonuçları ışığında YAM içeren çözeltilerin heterotrofik biyokütle üzerindeki inhibisyon etkilerinin fotokimyasal arıtma ile çok yüksek oranda azaltıldığı ve oksidasyon süresi boyunca oluşan oksidasyon ara ve son ürünlerin toksik etkisinin olmadığı söylenebilmektedir. Anahtar Kelimeler: Anyonik, katyonik ve noniyonik yüzey aktif maddeler, H2O2/UV-C arıtımı, cevap yüzey yöntemi, optimizasyon, aktif çamur inhibisyonu.Surfactants are widely used in household detergents, personal care products, paints, inks, polymers, pesticide formulations, pharmaceuticals, mining, oil recovery, pulp and paper, tannery and textile industries. Due to their amphiphilic characteristics, surfactants tend to sorb and hence accumulate onto sludge and soil sediments thus imparting serious ecotoxicological risks in the environment. As a consequence, more effective and at the same time economically feasible treatment processes have to be applied to alleviate the chronic problem of surfactant accumulation in the aquatic ecosystems. Among different alternative treatment options, in particular chemical and photochemical advanced oxidation processes (AOPs) have proven to be good candidates for the destructive treatment of surfactants. Response surface methodology (RSM) is a collection of statistical and mathematical techniques that are employed for the development, improvement and optimization of certain processes in which a response of interest is affected by several process variables and the objective is to optimize this response. RSM offers several advantages over classical experimental optimization methods in which a "one process variable at a time" approach. RSM provides more information from a relatively little number of experiments as compared with conventional optimization procedures, which is less expensive and time consuming. In particular, in more complex treatment systems such as photochemical advanced oxidation processes, interactive and synergistic effects are quite common making these applications ideal candidates for RSM. Considering the above mentioned facts, the present experimental study aimed at investigating the photochemical oxidation of commercially important anionic (a dioctyl sulfosuccinate), cationic (a quaternary ammonium ethoxylate) and nonionic (a nonyl phenol ethoxylate derivative) surfactant types. RSM-Central composite design (CCD) was used to analyze, model and optimize surfactant (parent compound, PC) and organic carbon (COD, TOC) removals during photochemical treatment. Two different experimental and statistical design matrices were developed for the assessment of both surfactants (parent compound) and their organic carbon content removals on the basis of treatment time. Process optimization was based on two photochemical treatment targets; (i) partial oxidation (for COD, TOC removals) to achieve complete parent pollutant abatement and (ii) full treatment for complete oxidation (mineralization) of aqueous surfactant solutions. The established polynomial regression models were validated by running separate experiments under photochemical oxidation conditions being previously optimized for different initial CODs. In the last stage of the study, separate experiments were run at the same local optima to examine the inhibitory effect of photochemical treatment of aqueous surfactant solutions on the oxygen uptake rate of activated sludge microorganisms. In the preliminary baseline experiments, rapid degradation of all studied textile surfactant solutions accompanied with high COD and TOC removals was observed. Surfactant abatements were complete within 15-20 min photochemical treatment, whereas over 90% COD and TOC removals could be achieved after prolonged oxidation periods for an initial surfactant COD of 450 mg/L and an initial pH of 10.5. The efficiency of the H2O2/UV-C process was appreciably influenced by all selected process outputs in the following decreasing order; photochemical treatment time (positive effect) > initial COD content of the surfactant formulation (negative effect) > initially added H2O2 concentration (positive effect, except for parent compound removals, that required low concentrations compared to organic carbon abatements). Analysis of variance revealed that the established factorial design models were statistically significant and described parent compound, COD and TOC removals at satisfactory levels. The highest correlation coefficients were obtained for TOC removals (surfactant mineralization rates). The established response surface models could be used to precisely optimize specific photochemical treatment targets for full and partial (pre-) treatment of different types of surfactants. The experimental design models were also capable of predicting advanced oxidation efficiencies at different photochemical treatment durations and varying initial CODs of the aqueous surfactant solutions. Activated sludge inhibition experiments conducted with heterotrophic biomass indicated that during the application of H2O2/UV-C treatment under optimized reaction conditions, no toxic oxidation products were formed. Keywords: Anionic, cationic and nonionic surfactants, H2O2/UV-C treatment, response surface methodology, optimization, activated sludge inhibition.

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

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