Treatment of azo dye production effluents with Photo-Fenton-like advanced oxidation process

Boya üretimi atıksuları içerdikleri ham maddeler, ara ürünler, yardımcı kimyasallar ve kalıntı boyalar nedeniyle yoğun renk ve yüksek kimyasal oksijen ihtiyacına sahip biyolojik olarak zor ayrışabilir nitelikte atıksulardır. Bu atıksuların çevresel özellikleri dikkate alındığında, demir bazlı fotokatalitik ileri oksidasyon prosesleri ile arıtımın iyi bir alternatif oluşturduğu görülmektedir. Bu çalışmada azo boyar madde sentez atıksularının Foto-Fenton-benzeri ileri oksidasyon prosesiyle (Fe3+/H2O2/UV-A) arıtılabilirliği incelenmiştir. Seçilen proses parametrelerinin (başlangıç Fe3+, H2O2 konsantrasyonları, KOİ içeriği ve reaksiyon süresi) renk, KOİ ve TOK giderimleri üzerindeki etkilerinin belirlenmesi, modellenmesi ve proses optimizasyonu amacıyla cevap yüzey metodu kullanılmıştır. 200 mg/L KOİ’ye sahip Asit Mavi 193 içeren sentetik asit boyar madde sentez atıksuyu için optimum işletme parametreleri; 1.5 mM Fe3+, 35 mM H2O2 ve 45 dakika reaksiyon süresi olarak bulunmuştur. Bu koşullar altında deneysel olarak elde edilen toplam renk, KOİ ve TOK giderimleri sırasıyla % 98, % 78 ve % 59'dur. Elde edilen deneysel sonuçların cevap yüzey yönteminin oluşturduğu polinomal regresyon modelinin tahminleri ile uyumlu olduğu görülmüştür. Aynı model, sentetik Reaktif Siyah 39 üretimi atıksuyunun foto-Fenton benzeri oksidasyonla arıtımını da başarılı bir şekilde tanımlamıştır. Reaktif Siyah 39 ters osmoz çıkış atıksuyunun arıtımında elde edilen giderim verimleri ise model tahminlerinin oldukça altında kalmıştır. Arıtma performansındaki bu düşüşün nedeni gerçek atıksuyun yüksek Cl- içeriğine bağlanmıştır. Cl- iyonlarının OH radikali ile reaksiyonu sonucu ortamdaki aktif oksidan miktarı azalmakta, bu da organik madde gideriminin gerek hızını gerekse verimini düşürmektedir. Anahtar Kelimeler: İleri oksidasyon prosesleri (İOP), azo boyar madde sentez atıksuları, Foto-Fenton-benzeri proses, cevap yüzey metodu, proses modelleme ve optimizasyon, OH radiakl tutucu.Dye manufacturing wastewater generally includes residual dyestuffs, dye intermediates as well as unreacted raw materials such as aromatic amines with alkyl-, halogen-, nitro-, hydroxyl-, sulfonic acid- substituents, and inorganic sodium salts. The effluent is normally characterized by a high chemical oxygen demand and intense color. The volume of the dye manufacturing wastewater is about 100-200 m3/day which is considerably low as compared with textile dye bath effluents. Several waste streams being variable in composition and strength are generated during dye synthesis activities. The COD content of the combined dye manufacturing effluent is around 2000-3000 mg/L. The BOD5/COD ratio of the wastewater is quite low, implying that it bears a considerable amount of non-biodegradable organic matter. Another risk hazard is that the dyes and dye intermediates can be reduced in the aquatic environment to produce carcinogenic compounds (i.e. naphthylamines, substituted phenylamines, benzidine analogues) under anoxic conditions. Dye manufacturing effluent may also contain free and complexed, toxic heavy metals (i.e. cobalt, chromium, copper) that result from the production of metal-complex azo dyes. Various combinations of conventional treatment processes, including physical chemical and biochemical methods have been used for the treatment of dye manufacturing wastewater. Recent studies indicated that advanced oxidation processes (AOPs) might be a good alternative for treating recalcitrant and/or toxic pollutants. AOPs involve the production of strongly oxidizing agents, mainly hydroxyl radicals (OH) that react rapidly and almost non-selectively with most inorganic and organic compounds including biologically-difficult-to-degrade azo dyes and dye intermediates. The advanced oxidation of dye containing wastewaters with Fenton and Photo-Fenton processes is a promising alternative because of their high efficiency in decolorization, ease of operation and relatively low treatment costs. Specially, the low volume and high recalcitrance of dye manufacturing effluent streams make them ideal candidates for Fe-based AOPs. In the current study, the treatability of acid and reactive azo dye synthesis effluents by Photo-Fenton-like advanced oxidation process was investigated. The effect of several operating parameters (Fe3+ and H2O2 concentrations, initial effluent COD, reaction time) on treatment efficiency for acid dye synthesis effluent bearing Acid Blue 193 was evaluated. Improvement in the color, COD and TOC abatements were observed with the increase in initial Fe3+ concentration, while increasing the initial H2O2 concentration only enhanced the removal of TOC. Increasing the initial COD of the wastewater promoted color and COD removals whereas TOC removal efficiency obviously decreased. Hence, the proper selection of the correct reagent concentrations considering the initial organic carbon content was found to be important to achieve high treatment efficiencies. Response surface methodology was employed for optimization of the process in order to maximize percent color, COD and TOC removal efficiencies. For an initial effluent COD of 200 mg/L, optimum working conditions were established as 1.5 mM Fe3+, 35 mM H2O2 and 45 min treatment time. Under these reaction conditions, experimentally achieved color, COD and TOC removal efficiencies were found as 98%, 78% and 59%, respectively. These actual results fitted well to the model predictions. In the Photo-Fenton-like treatment of synthetic Reactive Black 39 production wastewater, experimentally obtained percent removals were slightly higher than the model predictions in terms of color and COD. On the other hand, experimentally achieved TOC abatement was lower than the predicted value, denoting that complete mineralization of Reactive Black 39 production wastewater is more difficult than that of Acid Blue 193 production wastewater. For the real dye manufacturing effluent experimentally obtained COD and TOC abatements established for optimum treatment conditions were considerably lower than the model predictions, and an appreciable retardation was observed in terms of color abatement rates. The significant decrease in the organic carbon removal efficiency was mainly attributed to the high chloride concentration (Cl- = 3500 mg/L) of the real Reactive Black 39 production effluent, which caused OH scavenging reactions. The main conclusion drawn from the present study is that the Photo-Fenton-like oxidation process was found to be effective in the treatment of dye production effluents. However, it is highly recommended to determine the chloride content of the wastewater prior to application of such a photochemical process, since high cloride concentrations could have a significant adverse effect on the oxidation performance. Keywords: Advanced oxidation processes (AOPs), azo dye production wastewater, Photo-Fenton-like process, response surface methodology, process modeling and optimization; OH radical scavenger

Assessment of chemical treatability of olive mill wastewaters by coagulation and electrocoagulation

Zeytinyağı üretiminde ortaya çıkan karasuyun arıtımı yüksek biyokimyasal oksijen ihtiyacı (BOİ5 = 15-135 g/L), kimyasal oksijen ihtiyacı (KOİ = 37-318 g/L), askıda katı madde (AKM = 6-69 g/L) ve toplam fenol (TF = 2-5 g/L) içeriği nedeniyle önem taşımaktadır. Zeytinyağı endüstrisi atıksuları aynı zamanda 10 g/L'yi aşan fenolik ve tannik asit içerikleri nedeniyle biyolojik olarak zor ayrışan bir yapıya sahip olup antimikrobiyal aktiviteye, başka bir deyişle toksisiteye sebep olmaktadırlar. Bu çalışmada, zeytinyağı karasuyundan koagülasyon ve elektrokoagülasyon yöntemleriyle organik madde giderimi hedeflenmiştir. Sönmüş kireç (Ca(OH)2), demir(III) klorür (FeCl3.6H2O), alum (Al2(SO4)3.18H2O) ve demir bazlı ticari koagülan ve pıhtılaştırma yardımcısı kullanılarak gerçekleştirilen koagülasyon deneylerinde elde edilen en yüksek KOİ ve TOK giderim verimleri, kireç ile çöktürme için pH 11’de % 49 ve % 38, demir(III) klorür ile çöktürme için pH 7.0’de 1000 mg/L FeCl3 dozajında % 44 ve % 53, alum ile çöktürme için pH 6.5’da 1500 mg/L dozajda % 40 ve % 36 ve demir bazlı ticari bir koagülan ve pıhtılaştırma yardımcısı ile çöktürme için ise % 46 ve % 43 olarak belirlenmiştir. Uygulanan kimyasal arıtma prosesleri arasında en yüksek organik madde giderimi, çelik elektrodlar kullanılarak gerçekleştirilen elektrokoagülasyonda KOİ ve TOK bazında sırasıyla % 60 ve % 65 oranlarında elde edilmiştir. Elde edilen deneysel sonuçlar değerlendirildiğinde, koagülasyon ve elektrokoagülasyon arıtma proseslerinin organik karbon ve fenolik madde gideriminde yaklaşık olarak aynı düzeyde giderim sağladığı sonucuna varılmıştır. Bu çalışma çerçevesinde incelenen kimyasal arıtma proseslerinin karasu ön arıtımı için uygun ve uygulanabilir yöntemler olduğu tespit edilmiştir. Anahtar Kelimeler: Antioksidan aktivitesi, elektrokoagülasyon, koagülasyon, organik karbon giderimi, toplam fenol, zeytinyağı karasuyu.Olive oil industry is of vital economic importance for many Mediterranean countries, accounting for approximately 95% of the olive oil production worldwide. Generation and disposal of around 30 million m3 of olive mill wastewater per year constitute a serious environmental problem for the Mediterranean Region, due to the unique features associated with this type of agro-wastewater, namely seasonal (typically between November and February) and localized production and the high organic carbon content quite resistant to biodegradation. The characteristics of olive mill wastewater generated in the small-to-medium scale companies largely depend on the type of extraction process employed -the traditional press method or the continuous, three-phase centrifugation process. Accordingly, the high and refractory organic content of olive mill wastewater varies in the range of 37 - 318 g/L chemical oxygen demand (COD), 15 - 135 g/L biochemical oxygen demand (BOD5), 6-69 g/L suspended solids and 2.5 g/L total phenolic content (TPh). Different physical, chemical and biological processes have so far been proposed for olive mill wastewater treatment. Recently, olive mill wastewater was subjected to sequential coagulation/ flocculation/sedimentation /filtration processes as well as lime treatment, resulting in 62-73% phenolics removal depending upon the process applied for olive oil extraction. More than 40% COD and about 95% oil and grease removals were obtained in these studies. Olive mill wastewater could also be partially treated via coagulation using different polyelectrolyte materials; nearly complete reduction in suspended solids was accomplished accompanied with partial reductions in COD and BOD5 up to 55% and 23%, respectively. The use of conventional coagulants such as alum and ferric chloride was also reported, resulting in 90-91% total phenols and 94-95% COD removals after preliminary acid cracking. Biological treatment methods such as the activated sludge process and anaerobic digestion were also investigated, all reporting different operating problems due to the high toxicity and bio-inhibitory effect of the olive mill wastewater on heterotrophic biomass. Therefore, the elimination of polyphenolic compounds from olive mill wastewater via appropriate chemical pretreatment methods was considered as an important criterion for toxicity reduction. As briefly summarized above, results of previous experimental work on the treatability of olive mill wastewater, although extensive, are too diverse and conclusive, mainly because they only focus on collective parameters describing the organic carbon content of wastewater, such as COD, BOD5, etc. Within the scope of the present experimental study, organic carbon removal from olive mill wastewater via different chemical treatment processes (coagulation and electrocoagulation) was investigated. For this purpose, hydrated lime (Ca(OH)2), ferric chloride (FeCl3.6H2O), alum (Al2(SO4)3.18H2O) and commercial grade iron base coagulant and coagulant aid were employed as coagulants. Highest COD and TOC removals were obtained with lime precipitation at pH 11 as 49% and 38%, with 1000 mg/L ferric chloride at pH 7.0 as 44% and 53%, with 1500 mg/L alum at pH 6.5 as 40% and 36%, and with commercial grade iron base coagulant and coagulant aid as 46% and 43%, respectively. Highest organic carbon removal was achieved with electrocoagulation using stainless steel electrodes resulting in 60% and 65% COD and TOC abatement respectively, accompanied with 55% antioxidant activity and 52% total phenolics removals. It could be concluded that applying electrocoagulation (with stainless steel electrodes) that has recently received great interest because of its enigmatic treatment performance, resulted in considerably higher treatment performance as compared to the other chemical treatment processes due to its combinative abatement modes featuring redox reactions as well as coagulation, adsorption, precipitation and flotation. Considering the obtained experimental results, it can be concluded that coagulation and electrocoagulation are suitable treatment options for organic carbon and phenolic matter removal from olive mill wastewater. In the light of the experimental findings, it can be inferred that all investigated chemical processes are suitable for chemical pretreatment of olive mill wastewater. Keywords: Antioxidant activity, coagulation, electrocoagulation, olive mill wastewater, organic carbon removal, total phenol.

Treatability of wastewaters containing complex metal by electrocoagulation process

Toxic metals have been categorized in priority pollutant lists and their proper management is the main subject of recent environmental studies. Conventionally, hydroxide precipitation of metals is being employed for the treatment of metal finishing industry wastewaters. However, effluents bearing complexed heavy metals cannot be efficiently removed by employing precipitation methods. Recent research has demonstrated that electrocoagulation (EC) offers an attractive alternative to conventional treatment methods applied to metal finishing wastewaters. EC is known as an easy-to-operate and efficient electrochemical treatment method preferentially applied to treat "hard" industrial wastewater. EC using stainless steel and aluminum electrodes appears to be an ideal candidate for treatment of wastewaters containing complexed metals. Considering the above indicated facts, the present study focused on the treatability of metal finishing effluent originating from the nickel and zinc plating process by EC using stainless steel electrodes. In order to observe the system's performance as a function of varying process variables such as electrolyte (chloride) concentration, current density (mA/cm2), initial pH of the reaction solution and operation time, the feasibility of the proposed alternative treatment system was evaluated under different working conditions in terms of heavy metal (nickel and zinc) and organic matter (TOC) removal. Generally speaking, the treatment performance of EC  highly dependent upon the pH of the wastewater to be treated and the pH increases from its original pH to alkaline pH values during the course of reaction due to cathodic hydroxide formation. For the evaluation of the effect of initial pH on process performance, a series of experiments were carried out with the effluent at a fixed electrolyte concentration (1615 mg/L chloride) and current density (22.5 mA/cm2) at initial pH values of 3-10. The obtained findings indicated that the overall TOC removals were independent from pH at the studied pH range. On the other hand, heavy metal removal via EC was governed by the effluent pH. This is mainly because the pH value reached at the end of the selected EC operation time (120 min) was in the proper range for zinc and nickel hydroxide precipitation. On the other hand, nickel removal was influenced by the residual TOC and significant nickel removal began after TOC fell below 100 mg/L. The electrolyte concentration increases the conductivity of the reaction solution which in turn reduces the voltage needed to achieve a certain current. The effect of electrolyte concentration on the process performance was also examined. The experiments were conducted with effluent having initial pH of 6.0 at a fixed current density (22.5 mA/cm2) at electrolyte (chloride) concentrations in the range of 1500-3000 mg/L. Increasing the chloride concentration from 1500 to 3000 mg/L accelerated the TOC removals for an operation time of 75 min. However, the actual chloride concentration of the wastewater (1350-1480 mg/L) was adequate for TOC, nickel and zinc removal employing EC. In terms of both treatment efficiencies and electrical energy requirements, the applied current density is the most critical factor and hence key design parameter affecting the treatment systems's response time as well as dominant separation/pollutant mode. For any specific application, the optimal current density has to be determined and will invariably involve a trade-off between operational costs and most efficient use of the produced coagulant. Therefore, a series of EC experiments was carried out with the same effluent at densities varying between 2.25 - 56.25 mA/cm2. For the evaluation of the affect of current density on system performance the original pH (6.0) and chloride concentration (1480 mg/L) of the wastewater were selected. From the experimental results it could be concluded that increasing the current density from 2.25 to 9.0 mA/cm2 dramatically increased TOC removal efficiencies from 20% to 60%. For the higher current densities investigated (22.5-56.25 mA/cm2), the same TOC removal efficiencies could be achieved but at relatively shorter reaction times. Keywords: Electrocoagulation; metal finishing industry, nickel and zinc removal; organic carbon abatement, stainless steel electrodes.Günümüzde ağır metal içeren atıksuların arıtılması gerek bu tip akımların çok çeşitli kaynaklarının olması gerekse kirlenmede taşıdıkları önem nedeniyle dikkatle değerlendirilmesi gereken bir nokta olarak gündeme gelmektedir. Kompleks olarak bağlı metal içeren atıksular, bünyelerinde organik kompleks yapıcıların (organik ligandların) bulunduğu atıksulardır. Henüz bu atıksularının arıtımı için uygun bir arıtma teknolojisi tanımlanmamıştır. Bu çalışmada elektrokoagülasyon prosesinin, metal son işlemleri endüstrisi kompleks olarak bağlı metal içeren atıksularına uygulanabilirliği, bir asidik nikel çinko kaplama banyosundan kaynak bazında alınan atıksu numunesi ile bu işlemi takip eden yıkamaları karakterize etmek üzere hazırlanan kompozit numune (TOK=173-207 mg/L; Ni=275-291 mg/L, Zn=226-236 mg/L) kullanılarak araştırılmıştır. Elektrolit konsantrasyonunun, başlangıç pH sının ve akım yoğunluğunun çinko ve nikel ile birlikte organik madde (TOK) giderimi üzerine etkileri incelenmiş ve değerlendirilmiştir. Deneysel çalışmadan elde edilen sonuçlar; paslanmaz çelik elektrodların kullanıldığı elektrokoagülasyon uygulaması ile söz konusu atıksulardan nikel ve çinkonun % 100 verimle tamamen giderilebildiğini göstermiştir. Başlangıç pH sının ve elektrolit konsantrasyonunun TOK giderimi üzerine önemli bir etkisinin olmadığı ve atıksuyun kendi bünyesindeki klorür konsantrasyonunun elektrokoagülasyon prosesinin işletimi için yeterli olduğu sonucuna varılmıştır. Akım yoğunluğunun etkisinin belirlendiği deneysel çalışmalarda ise 2.25-9.0 mA/cm2 akım yoğunlukları arasında artan akım yoğunluğu ile TOK giderme veriminin arttığı, daha yüksek akım yoğunluklarında (22.5-56.25 mA/cm2 aralığı) ise aynı TOK giderim verimlerine daha kısa sürelerde ulaşıldığı belirlenmiştir. Bu proses ile optimum işletme koşullarında (akım yoğunluğu= 22.5 mA/cm2; başlangıç pH= 6); numunenin kendi bünyesindeki çözünmüş madde konsantrasyonundan elektrolit olarak  faydalanılarak çinko ve nikel tamamen, TOK ise %50 oranında giderilmiştir. Anahtar Kelimeler: Çelik elektrodlar, elektrokoagülasyon, kompleks olarak bağlı metal içeren atıksular, metal son işlemleri endüstrisi,  nikel ve çinko giderimi, organik madde giderimi

More about Persulfate-Assisted Ferrilanthanide-Mediated Photocatalysis of Textile Industry Dye Reactive Black 5: Surface Properties and Structural Assessment

Color and organic matter removal from dyehouse effluent remains a challenging issue for the environmentalist and textile dyer. Until now, various treatment processes have been proposed with limited success. In this study, the textile dye and model industrial pollutant Reactive Black 5 (RB5; 20 mg/L) could be rapidly degraded by persulfate (PS)-enhanced photocatalytic treatment using a novel, home-made lanthanum iron oxide (LF; 0.5 g/L). LF-mediated heterogeneous photocatalysis was effective when the solution pH was kept below 4. The photocatalytic degradation of RB5 solution was enhanced in the presence of 0.6 and 1.2 mM PS. The dissolved organic carbon (DOC) content of the aqueous, hydrolyzed RB5 solution (initial DOC = 5.15 mg/L) was effectively reduced by LF/UV-A (LF = 0.5 g/L; 52–54% DOC removal after 150–180 min) and LF/PS/UV-A (LF = 0.5 g/L; 60–66% DOC removal after 120 min) treatments. LF photocatalyst could be reused in four consecutive cycles for complete color and partial DOC removals without significant deterioration of the treatment performance with the LF/PS/UV-A/pH 3 process. Instrumental analyses of LF’s surface morphology/chemical composition and structural features via EDAX/SEM/Raman/FTIR/UV-vis/fluorescence spectroscopy indicated that LF remained practically intact throughout photocatalytic treatment, though slight changes/decreases in particle size/partial surface deformation and agglomeration coverage were observed, particularly during LF/PS/UV-A treatment. The presence of RB5 and its degradation products on the LF surface revealed that surface adsorption played a major role in LF-mediated photocatalysis. The Fe-content did not deviate appreciably from its original value after photocatalytic treatment. © 2023 by the authors

Dimethyl phthalate degradation by Peroxymonosulfate (oxone)/UV-C photochemical process

Ftalik asit esterleri (ftalatlar) kağıt, karton, kozmetik, deterjan, şampuan, sabun, tıbbi malzeme, plastik kap ve boya üretiminde hammadde veya yardımcı kimyasal madde olarak kullanılmaktadır. Endüstrilerde, malzemelerin esneklik özelliğini arttırmak için kullanılan ftalatlar, toksik özellik gösteren, kanserojen, endokrin bozucu ve birikme potansiyeline sahip maddelerdir. Ftalatların arıtımında konvansiyonel arıtma prosesleri ile yüksek giderme verimleri elde edilememekte ve bu nedenle arıtımlarında adsorpsiyon ve ileri oksidasyon proseslerinden yararlanılmaktadır. Bu çalışma kapsamında endokrin bozucu ve toksik etkileri nedeniyle kullanımlarında yasal düzenlemeler yapılmış ftalatlara örnek teşkil etmek üzere seçilen dimetil ftalat (DMF) model kirleticisinin sulu çözeltisinin fotokimyasal ileri oksidasyon proseslerinden olan peroksimonosülfat (PMS-okson)/UV-C ile arıtımı incelenmiştir. Giriş PMS konsantrasyonunun ve başlanıç pH değerinin proses giderim verimi üzerine etkisi araştırılmış ve prosesin arıtma performansı DMF ve TOK ölçümleri yapılarak değerlendirilmiştir. Gerçekleştirilen deneysel çalışmalarda PMS/UV-C prosesi ile DMF’nin gideriminin birinci dereceden hız kinetiğine uyum sağladığı belirlenmiştir. Belirli bir değere kadar (50mM) artan PMS konsantrasyonu ile DMF giderimi için birinci dereceden hız sabitinin arttığı tespit edilmiştir. En yüksek hız sabiti k40mM= 0.276 L/dk olarak bulunmuştur ve PMS konsantrasyonu 50 mM’a arttırıldığında hız sabiti k50mM= 0.246 L/dk değerine düşmüştür. TOK giderimi incelendiğinde ise artan PMS konsantrasyonu ile tam mineralizasyonun sağlandığı arıtma süreleri azalmaktadır. Optimum PMS konsantrasyonunda (40mM) 40. dakikanın sonunda tam mineralizas-yon sağlanmıştır. Elde edilen sonuçlar ışığında DMF gideriminde PMS/UV-C prosesinin uygulanabilir etkin bir arıtma prosesi olduğu sonucuna varılmıştır.  Anahtar Kelimeler: Dimetil ftalat; elektrik enerjisi tüketimi; endokrin bozucu maddeler; fotokimyasal arıtma; kimyasal oksidasyon; peroksimonosülfat (okson).Phthalate esters (PAEs) are used as plasticizers to impart flexibility and resilience to plastic products. Other uses of phthalates are in ceramic, paper, cosmetic, ink, and paint industries. In recent years, PAEs have become a controversial issue because many phthalates are suspected to be mutagens, hepatotoxic agents and endocrine disruptors, and can lead to adverse effects on organisms even in a low concentration. The short-chained esters such as dimethyl phthalate (DMP), which mainly originate from industrial wastewater discharge and leaching and volatilization from plastic products during their usage and after disposal, are among the most frequently, identified PAEs in diverse environmental samples including marine water, surface waters and sediments. Studies of DMP?s biodegradation in fresh water, marine water, sediment, wastewater and sludge, have revealed a low degradation rate in the range of several days to a few months. Thus the destruction of these bio-recalcitrant organic pollutants requires the application of vigorous oxidizing agents, such as those used in advanced oxidation processes (AOPs). Recently, sulfate radical based-AOPs have attracted great scientific and technological interest in the area of wastewater treatment and other environmental applications. OxoneÒ, the commercial name of potassium peroxymonosulfate, is a triple salt with the composition of 2KHSO5·KHSO4·K2SO4 is a convenient source of generating sulfate radical (SO4·-). Peroxymonosulfate (PMS), is a mono-SO3- substituted hydrogen peroxide (H2O2) and has been used in a restricted way as an oxidant in light induced processes. Radiolysis, photolysis, or thermal activation of PMS leads to the formation of both SO4·- and hydroxyl radical (HO·). The use of UV light leads to the generation of SO4·- and HO· through the photolysis of the PMS. SO4·- is a very strong oxidant (Eo = 3.1 eV) and engages in at least three reaction modes with organic compounds similar to HO·: by abstracting a hydrogen atom from saturated carbon, by addition to unsaturated or aromatic carbon, and by removing one electron from carboxylate anions and from certain neutral molecules which may eventually lead to the mineralization of the organic substance. The main targets of the present study were: to assess the performance of PMS/UV-C process in the treatment of aqueous solution of DMP (100 mg/L) selected as a model PAE and to explore the effect of some important operating parameters, such as reaction pH (3-9), initial PMS concentration (0-60 mM) and reaction time (0-120 min) on DMP and organic carbon abatement rates. The  results of this study is expected provide fundamental and practical information as a guide for the treatment of bio-recalcitrant organic pollutants by the PMS/UV-C process. For the initial pH values tested, it was found that lowering the initial pH of the aqueous DMP solution slightly improved the degradation rate of DMP. For instance, higher than 95% DMP abatement was achieved after 60 min at pH 3 while the extended reaction times, i.e. 90 and 120 min, required in order to achieve the same level of DMP reduction at initial pH values of 6 and 9 for 5 mM initial PMS concentration, respectively. However, TOC abatements were slightly enhanced with increasing the initial pH. Based on these results pH 3 was selected as the most effective pH for the degradation of DMP. DMP abatement increased with elevating initial PMS concentrations from 5 to 40 mM. Further increase in initial PMS concentration to 50 and 60 mM, however, slightly reduced the extent of DMP removal. With an initial DMP concentration about 100 mg/L, more than 95% of DMP could be removed at time of 20 min under an initial PMS concentration of 40 mM. DMP degradation by PMS/UV-C process successfully represented by a pseudo first-order kinetic model and the highest reaction rate constant was calculated as 0.276 L/min for 40 mM initial PMS concentration. As aforementioned further increase of the PMS concentration slightly reduces the DMP removal rates to 0.246 L/min for 50 mM and 0.243 L/min for 60 mM initial PMS concentrations. The photodegradation of aqueous organic pollutant is an electrical-energy-intensive process, and electrical energy typically represents a major fraction of the operating costs. The lowest electrical energy per order (EE/O) value for DMP oxidation by PMS/UV-C process was calculated as  2.9 kWh m-3 order-1 at the case of 40 mM PMS concentration. Keywords: Dimethyl phthalate; operating cost analysis; endocrine distrupting compounds; photochemical treatment; peroxymonosulfate (oxone), chemical oxidation

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.

Water-wastewater resources based on river basins in Turkey and urban wastewater treatment potential

Bu makalenin başlıca amacı ülkenin su ve atıksu ile ilgili konularda mevcut durumunu tanımlayarak, sürdürülebilir su ve atıksu yönetimi çabalarına katkıda bulunmaktır. Çalışmada, ülkenin çevre sorunlarının incelenmesi açısından en uygun değerlendirme boyutunu oluşturması nedeni ile su havzaları esas alınmıştır. Her bir havzanın özelliği, coğrafik yapılarına, iklim koşullarına, endüstriyel faaliyet yoğunluklarına, kıyı şeridine olan uzaklıklarına ve Büyükşehir Belediyesi sınırları içinde yer almalarına bağlı olarak birbirinden farklı bulunmuştur. Veri eksiklikleri ve/veya elde edilen bilgilerin güvenilir olmaması ile birlikte, söz konusu veri tabanlarının farklı devlet kuruluşları bünyesinde dağınık olarak bulunması, sürdürülebilir su ve atıksu yönetimini iyileştirme ve yeniden düzenleme konusundaki çalışmaları oldukça zorlaştırmıştır. Anahtar Kelimeler: Sürdürülebilir su ve atıksu yönetimi, Türkiye’nin nehir havzaları, kentsel atıksu arıtma tesisleri, su kaynakları.Sustainable wastewater management can only be promoted when the existing situation is well defined. It also necessitates the investigation of the national monitoring and control acts, as without an idea on the national water and wastewater policies it is very hard to establish a healthy and satisfactory management strategy. As a rapidly developing country, Turkey faces certain difficulties in having a well-organized and systematic database concerning especially infrastructure facilities. The major objective of this paper is to identify the prevailing situation of water and wastewater issues to promote sustainable water and wastewater management efforts in Turkey. For that purpose, a detailed data inventory followed by the evaluation of the existing urban wastewater treatment facilities was conducted. The study was solely based on the river basins of the country as basin wide approaches seem to be the most convenient scale to deal with such environmental issues. The characteristics of each basin were found to vary from each other, mainly due to the variations in geographical structure, climatic conditions, the intensity of industrial activities, proximity to the coastlines, and locations within the boundaries of Greater Municipalities. Lack of information and/or reliance on available data together with data scattered among various governmental organizations made the study of improving and re-establishing a sustainable water and wastewater management strategy for the country rather difficult.Keywords: Sustainable water and wastewater management, Turkish river basins, urban wastewater treatment plants, water resources

More about Persulfate-Assisted Ferrilanthanide-Mediated Photocatalysis of Textile Industry Dye Reactive Black 5: Surface Properties and Structural Assessment

Color and organic matter removal from dyehouse effluent remains a challenging issue for the environmentalist and textile dyer. Until now, various treatment processes have been proposed with limited success. In this study, the textile dye and model industrial pollutant Reactive Black 5 (RB5; 20 mg/L) could be rapidly degraded by persulfate (PS)-enhanced photocatalytic treatment using a novel, home-made lanthanum iron oxide (LF; 0.5 g/L). LF-mediated heterogeneous photocatalysis was effective when the solution pH was kept below 4. The photocatalytic degradation of RB5 solution was enhanced in the presence of 0.6 and 1.2 mM PS. The dissolved organic carbon (DOC) content of the aqueous, hydrolyzed RB5 solution (initial DOC = 5.15 mg/L) was effectively reduced by LF/UV-A (LF = 0.5 g/L; 52–54% DOC removal after 150–180 min) and LF/PS/UV-A (LF = 0.5 g/L; 60–66% DOC removal after 120 min) treatments. LF photocatalyst could be reused in four consecutive cycles for complete color and partial DOC removals without significant deterioration of the treatment performance with the LF/PS/UV-A/pH 3 process. Instrumental analyses of LF’s surface morphology/chemical composition and structural features via EDAX/SEM/Raman/FTIR/UV-vis/fluorescence spectroscopy indicated that LF remained practically intact throughout photocatalytic treatment, though slight changes/decreases in particle size/partial surface deformation and agglomeration coverage were observed, particularly during LF/PS/UV-A treatment. The presence of RB5 and its degradation products on the LF surface revealed that surface adsorption played a major role in LF-mediated photocatalysis. The Fe-content did not deviate appreciably from its original value after photocatalytic treatment

Treatability of a simulated spent disperse dyebath by chemical and electrochemical processes

Electrocoagulation (EC) using aluminum (Al) and stainless steel (SS) electrodes was investigated for color and chemical oxygen demand (COD) removal from a simulated spent disperse dyebath. EC was optimized for electrolyte (NaCl) concentration (750 - 3000 mg/ L), current density (9 - 87 mA/ cm(2)), and initial pH (3.5-11.5). Optimum EC conditions were established as 2,500 mg/ L NaCl, pH(o) = 7.0 and 44 mA/cm(2) for 100% color and 58% COD removals using Al electrodes (total treatment time = 30 min), whereas 100% color and 45% COD removals were obtained for 2,000 mg/ L NaCl, pH(o) = 7.3 and a current density of 44 mA/cm(2) when SS electrodes were employed for a 60-min treatment. EC results were compared with color and COD removals achieved via coagulation with alum, ferrous sulfate, and ferric chloride at varying doses (200 - 2,000 mg/L). Alum was more effective in color (100%) and COD (64%) removals than ferrous sulfate and ferric chloride. The amount of sludge formed during EC using SS electrodes was approximately 10 times less than the sludge produced during EC with Al electrodes, whereas electrical energy requirements to achieve 100% color and 50% COD removals were 10 and 30 times higher, respectively, when SS electrodes were employed for EC