Nutrient recovery from anaerobically digested sewage sludge by struvite precipitation

Bu çalışmada, kentsel nitelikli anaerobik çürütülmüş çamurdan strüvit formunda nütrient geri kazanımı potansiyeli araştırılmıştır. Çürütülmüş çamurun katı fazından fosforun geri kazanımı için, katı faza fosfor çözündürme prosesinin uygulanması gerekmektedir. Çalışmada, çürütülmüş çamur katı fazına asidik koşullarda fosfor çözündürme prosesi uygulanması ile mevcut fosfor ortofosfata dönüştürülmüştür. Asidik koşullarda çözündürme prosesi ile oldukça yüksek nütrient içeriğine sahip (1085±4.95 mg/L NH3-N ve 840±21.21 mg/L PO4-P) fosforca zengin sıvı fazı elde edilmiştir. Asidik çözündürme prosesinin uygulanması ile katı fazdaki toplam fosforun yaklaşık %84’ü çözündürülmüştür. Fosfor çözündürme prosesinin strüvit çöktürmesi için başlangıç adımı olarak kullanılabileceği görülmüştür. Strüvit çöktürmesi testlerinde, Mg:N:P ve Mg:P molar oranlarının etkisi ayrı ayrı incelenmiştir. pH 8.5’da, Mg:N:P molar oranının 2:1:1.3 olduğu durumda PO4-P ve NH3-N giderim verimleri %99.84 ve 40.19 olarak elde edilmiştir. Bu durumda, strüvit çöktürmesi ile PO4-P’nin büyük bir kısmının NH4-N’nin ise belirli bir kısmının geri kazanımı gerçekleştirilmiştir. Asidik koşullarda çözündürme uygulaması sonucu fosforun yanı sıra serbest kalan metal iyonları, strüvit çöktürmesi sonucunda metal fosfatlar olarak çöktürülmüştür. Çalışmada, asidik çözündürme sonrası sıvı fazda mevcut bulunan Ca, Al, Fe ve Zn metallerinin yüksek konsantrasyonlarından dolayı, giderilen PO4-P’nin tamamı magnezyum amonyum fosfat olarak strüvit formunda giderilmemiştir. Bu durum strüvit katı fazında yapılan XRD analizi ile desteklenmiştir. XRD analizi sonucu, strüvite ek olarak diğer metal bileşiklerinin de mevcut olduğu görülmüştür. Anahtar Kelimeler: Fosfor çözündürülmesi, çürütülmüş çamur, nütrient geri kazanımı, strüvit çöktürmesi.The recovery of nutrients from the anaerobically digested waste stream is a potential source of revenue. There is an increasing awareness of limited natural resources and importance is given to the sustainable treatment activities; that is why control over the sources of N and P shifted from removal to recovery. This can be explained by the dependency of modern agriculture on P derived from phosphate rock. Phosphorus is an essential nutrient for all forms of life. Phosphorus consumption in the world in year 2006 was around 142 million tons of phosphate rock concentrate, which is annihilating economically extractable phosphate rocks. Therefore, the reliance on phosphate rocks should be stopped and sustainable ways to use phosphorus should be researched. A sustainable way to use phosphorus can be recovery of phosphorus from digested sewage sludge since almost all the removed phosphorus accumulates in treatment sludge in a conventional wastewater treatment plant whether phosphorus in wastewater is removed by biological phosphorus removal or by chemical phosphorus removal. Since mineral fertilizers account for approximately 80% of phosphates used worldwide, it would be beneficiary to recover phosphorus from digested sludge as a fertilizer. On the other hand, as a basic building block of plant protein; nitrogen is an essential element for agriculture and there is a growing demand for the nitrogenous fertilizer in the world. One of the most popular nutrient recovery applications in this sense is converting nutrients from digested sludge into magnesium ammonium phosphate hexahydrate (struvite). Struvite is a slow releasing fertilizer. Nutrient recovery from anaerobically digested sewage sludge is a viable option because digested sewage sludge is rich in nutrients. Moreover, most of the studies in literature focused on the removal/recovery of the readily available nutrients in the anaerobic digester effluents and little attempt were given on the extraction of the nutrients present in the solid phase of the anaerobic digester effluents. Therefore, this study focused on the removal and recovery of nutrients as struvite from solid phase effluents of a full-scale sewage sludge anaerobic digester. Nutrient recovery from the solid phase was achieved by the adoption of a novel phosphorus dissolution process. The recovery of nitrogen and phosphorus can only be done by using the dissolved fraction, but most of the nutrients are located in solid form. For this purpose, the solid phase was subjected to phosphorus dissolution process, thereby obtaining phosphorus-enriched liquid phase. The use of acidic phosphorus dissolution process was applicable to the solid phase of the full-scale sewage sludge anaerobic digester and can be used as a preliminary step of struvite precipitation experiments to obtain a nutrient rich solution. The dissolution of phosphorus from digested sludge consists of the following steps: Dissolution of the sludge using acids and separation of the phosphorus-enriched liquid phase from the remaining solid phase. The use of acidic phosphorus dissolution process led to the transformation of available phosphates into the orthophosphate. In this study the phosphorus-enriched liquid phase with considerably high concentrations of nutrients (1085±4.95 mg/L of NH3-N and 840±21.21 mg/L of PO4-P) was obtained. More than 80% phosphorus dissolution can be achieved at pH 2.0. In addition to the increase of orthophosphate concentration, acidic dissolution resulted in the release of the metals which were normally integrated in organic complex molecules into the liquid phase. Metals can be incorporated into the crystal lattice or sorbed to the surface of struvite. The phosphorus-enriched liquid phase was analyzed for the metals and heavy metals. In the struvite precipitation experiments conducted with the phosphorus-enriched liquid phase, the effects of molar concentration ratio of Mg:N:P and molar concentration ratio of Mg:P were investigated, separately. In the experiments conducted with the phosphorus-enriched liquid phase of digested sewage sludge by the addition of external phosphorus and magnesium, high recovery efficiencies (>99.7%) of PO4-P and partial recovery of (up to 40%) NH3-N was observed. Whereas in the experiments conducted by the addition of only magnesium, almost complete recovery (99.9%) of PO4-P and partial recovery of (only 5%) NH3-N was attained. The obtained results of the experiments indicated that struvite precipitation process can be used to recover PO4-P only or both NH3-N and PO4-P. The results from XRD analysis for the struvite precipitate collected from the reactor containing phosphorus-enriched solution indicated a struvite formation. Keywords: Phosphorus dissolution, digested sewage sludge, nutrient recovery, struvite precipitation

Pre-evaluation for the chemical substitution in a textile mill in Turkey

Kirlilik önleme çalışmalarında temel yaklaşımlardan birisi, kirletici özellikteki maddelerin daha az kirletici olanlar ile değiştirilmesidir. Bu çerçevede, biyolojik olarak kolay parçalanan maddelerin zor parçalananlara oranla uzun vadede daha az ekolojik problemlere neden olacağından hareketle, üretimde kullanılan kimyasal maddelerin biyodegradasyon özellikleri göz önüne alınması gereken önemli bilgilerden birisidir. Tekstil kimyasallarının toksik ve biyodegradasyon özellikleri konusunda yayınlanmış sınırlı sayıda çalışma bulunmaktadır. Kimyasalların biyodegradasyon potansiyellerini belirleme aşamasında, söz konusu kimyasala uygun yöntem seçilmesi önem arz etmektedir. Bu çalışmada, problemli kimyasalların ve alternatiflerinin biyodegradasyon potansiyellerini belirlemek amacıyla, OECD 302b (Zahn-Wellens) test metodu seçilmiştir. Testler, Türkiye’deki bir tekstil fabrikasında uygulanmakta olan reçetelerde kullanılan 2 adet kompleks yapıcı kimyasal madde (A ve B) ve kullanılma potansiyeli olan 1 adet kompleks yapıcı kimyasal maddenin (B*) biyodegradasyon potansiyellerini hem tek başlarına bulunmaları halinde var olan değerlerini doğrulamak, hem de birlikte kullanılmaları durumunda etkileşimlerini tespit etmek ve böylece, kimyasal değişikliğine karar verme aşamasında kullanmak amacıyla uygulanmıştır. Bu amaca yönelik olarak, kompleks oluşturan maddelerin farklı kombinasyonları ile kesikli reaktör deneyleri gerçekleştirilmiştir. Deneysel bulgular faktör analizi yöntemi ile istatistiksel analize tabi tutularak biyodegradasyon (bağlı değişken olarak) ve kompleks yapıcı madde konsantrasyonu (bağımsız değişken) arasındaki ilişki belirlenmiştir. Bu analizler, STATGRAPHIC istatistiksel yazılım programı kullanılarak yapılmıştır. Mümkün olabilecek kimyasal değişimine yönelik ön değerlendirme yapma amacıyla, doğrusal çoklu regresyon yöntemi ile matematiksel model oluşturulmuştur. Anahtar Kelimeler: Biyodegradasyon, doğrusal çoklu regresyon modeli, kimyasal değişimi, kirlilik önleme, kompleks yapıcı madde, tekstil endüstrisi.Substitution of less-pollutant chemicals for more-pollutant ones is a main focus for pollution prevention. In this respect, knowledge of the biodegradability of chemicals is one of the most important factors to be considered.  In this study, to measure the biodegradability potential of the problematic chemicals (complexing agents A and B) used in a Turkish Textile Mill and their alternatives (complexing agent B*), OECD 302b (Zahn-Wellens) tests were conducted. Experiments were performed at different combinations of complexing agents using unacclimatized activated sludge bacteria as seed. The biodegradability tests results obtained for the combination of complexing agents A and B revealed that the biodegradability of complexing agent B (46-67%, depending on its concentration) is higher than that of complexing agent A (15-21%, depending on its concentration), when they are present alone. When they are together, the biodegradability varies between 36 and 45% depending on their existence levels.  From these findings, the negative effect of having complexing agent A besides complexing agent B was apparent. The experimental results were also analyzed statistically by using factor analysis in order to clarify the relationship among the biodegradability and complexing agents. The following linear multiple regression model of the type was considered:  Y = B1X1 + B2X2 + B12X12 + B11X11 + B22X22 Where; Y: Biodegradability of mixture of complexing agents A and B or A and B* (%); B1: Coefficient for the effect of complexing agent A; B2: Coefficient for the effect of complexing agent B or B*; B12: Coefficient for combined effects of complexing agents A & B or A & B*; B11: Coefficient for quadratic effect of complexing agent A; B22: Coefficient for quadratic effect of complexing agent B or B*; X1: Complexing agent A (mL/L); X2: Complexing agent B or B* (mL/L); X12 : Interaction term of X1 and X2 ; X11 : Quadratic term of complexing agent A; X22: Quadratic term of complexing agent B or B*. The form of the model obtained for the combination of complexing agents A and B is as follows; Y = -19.2502 X1 + 24.6749 X2 - 3.59036 X12 + 16.3031 X11 - 2.20622 X22 The biodegradability test results for combination of complexing agents A and B* revealed that the biodegradability of complexing agent B* is higher than that of B with a biodegradability varying between 79 and 89%, depending on the concentration. When together with the complexing agent A, the biodegradability varies between 58 and 69%. The model obtained is as follows; Y = -20.0037 X1 + 34.1467 X2 - 3.05722 X12 + 16.707 X11 - 3.20648 X22 The effects of complexing agent B and B* on the biodegradability is found to be both in the positive direction. That is, complexing agents B and B* strongly enhance the biodegradability characteristic of the mixes.  When the complexing agents A and B, or A and B* (i.e. the term of X12) are present together, the total effect is inhibitory. According to the results of the models, there is an increase in the coefficient magnitude for the term X2 while using the complexing agent B* as compared to using the complexing agent B. This means that individual effect of complexing agent B* is higher than the individual effect of complexing agent B on biodegradability. According to the mix cases, the models show that there is also a small increase observed on term of X12 while using the complexing agent B*. The mix of complexing agent A and B has negative effects on biodegradability as understood from the negative sign of the coefficient. For the case of the complexing agent A and B* mix, this effect is again negative but it has a less magnitude value than mix of complexing agent A and B. By all things considered, complexing agent B* has better biodegradability characteristic than B. This behavior of B* is proven either by biodegradability tests of individual and mix concentrations and mathematical models set up by all experimental results. So, based on the results obtained in this study, if the mill considered to start using of this new chemical B* in the production line, a possible enhancement on biodegradability in wastewater would be achieved by the mill. Keywords: Biodegradability, linear multiple regression model, chemical substitution, pollution prevention, complexing agent, textile industry

Agricultural reuse of water and nutrients from wastewater treatment in Turkey

TÜBİTAK ÇAYDAG01.02.2012Atıksu arıtma tesisleri işletilmeye başlatıldığı tarihten bu yana hem kentsel hem de endüstriyel alanlarda çevre korunmasına katkı sağlamaktadır. Ancak konvansiyonel atıksu arıtma teknikleri modern bir sürdürülebilir kaynak yönetimi gereksinimlerini çoğunlukla sağlayamamaktadır. Bu teknolojilerinin ana özelliği nutrient ve karbon kaynağı gibi atıksu içinde bulunan değerli kaynakları ve kirleticileri ortadan kaldırılmaktır. Diğer bir deyişle konvansiyonel atıksu arıtma teknolojileri doğal kaynaklardan değerli nutrient kaynakların kaybına sebep olmaktadır. Özellikle yüksek su ve nutrient talebi olan bölgelerde, yenilikçi atıksu arıtma sistemleri ile değerli bileşiklerin kullanılmasını sağalamak gerekmektedir. Atıksu artık bir atık olarak görülmemeli, yeniden kullanılabilir ve değerli kaynakların bir karışımı olarak kabul edilmelidir. Suyun yeniden kullanımı tarımsal sulamada, çevre sulamada, endüstriyel geri dönüşümde ve yeraltı suyu geri beslemesinde umut verici bir kaynak olarak gösterilmektedir. Tüm bu uygulamalar arasında tarım en büyük bölümü temsil eder ve bu ihtiyaç gelişmekte olan ülkelerde yüksek bir ivmeyle artmaktadır. Bu projede, Türkiye'de atıksuyun yeniden kullanılabilirliğine yönelik yapılan potansiyel çalışması sonuçları ve belirli bölgelerde atıksuyun yeniden kullanılabilirliğinin teknoloji açısından değerlendirilmesi sunulmuştur. Yeni ve yenilikçi bir yaklaşım olarak, sunulan koşullar altında en iyi teknolojiyi belirlemek için modüler atıksu arıtma tesisi tasarımları gerçekleştirilmiştir. Bu bağlamda, farklı senaryolar için sistemlerin enerji tüketimi ve enerji üretimi; bunun yanı sıra yatırım ve işletme giderleri analiz edilebilir. Sonuçlar göstermektedir ki atıksuyun geri kullanımı özellikle tarımsal üretime katkı sağlamaktadır. 1.000 MWh’dan fazla enerji tasarrufu sağlanabilmekte ve tarımsal faaliyetlerde kullanılabilecek ek fosfor ve azot kaynağı oluşturulabilecektir. Sonuç olarak, eğer bir atıksu arıtma tesisi yapılacaksa veya bir tesiste değişiklikler öngörülüyorsa, modüler atıksu arıtma tesisi tasarımları kullanılarak geri kullanım açısından en uygun sistem seçilebilecektir.Wastewater treatment systems have undoubtedly improved environmental protection in urban and industrial areas since their introduction. However it has to be considered that conventional wastewater treatment techniques are mostly incompatible with the requirements of a modern sustainable resource management. The main characteristics of these end-of-pipe technologies is an extensive resource demand and elimination of valuable resources contained in wastewater such as nutrients and energy. In other words, conventional wastewater treatment technologies withdraw nutrients from the natural cycle thus interrupting the resource cycles. Especially in regions with high water and nutrient demand, innovative systems should be developed and implemented in order to allow a reuse of wastewater or its valuable compounds. Wastewater should no more be considered as an interfering waste product but rather as a mixture of valuable resources which should be recovered. Water reclamation has been shown to be promising in agricultural irrigation, landscape irrigation, industrial recycling and reuse and groundwater recharge. Among all applications agriculture represents the large reuse volume and accelerating increase is expected in developing countries. In this study, the results of an on-going international joint research project, aiming to determine the potential and feasibility of wastewater reuse techniques in specific regions in Turkey, are presented. As a new and innovative approach, a modular concept estimating best available technology for a given set of conditions has been developed. In this context, energy demand and energy production as well as investment and operating costs of considered modules can be analysed. Over 1.000 MWh can be saved by adopting the existing WWTP to agricultural reuse concepts while supplying the local farmers with additional phosphorus and nitrogen. As a result, transferring the modular investigation to cases where the wastewater treatment system has to be newly constructed, the overall most reasonable option can be identified

High-rate anaerobic treatment of digestate using fixed film reactors

Ulgudur, Nilufer/0000-0003-3410-0598; Demirer, Goksel/0000-0001-6030-2041WOS: 000483405400073PubMed: 31284204The effluent stream of the anaerobic digestion processes, the digestate, accommodates high residual organic content that needs to be further treated before discharge. Anaerobic treatment of digestate would not only reduce the residual organic compounds in digestate but also has a potential to capture the associated biogas. High-rate anaerobic reactor configurations can treat the waste streams using lower hydraulic retention times which requires less footprint opposed to the conventional completely stirred tank reactors. This study investigated the high-rate anaerobic treatment performance and the associated biogas capture from the digestate of a manure mixture composed of 90% laying hen and 10% cattle manures in fixed-film reactors. The results indicated that it was possible to reduce total chemical oxygen demand content of the digestate by 57-62% in 1.3-1.4 days of hydraulic retention time. The corresponding biogas yields obtained were in the range of 0.395-0.430 L-biogas/gVS(added) which were found to be comparable to many raw feedstocks. Moreover, significant total phosphorus reduction (36-47%) and greenhouse gas capture (over 14.5-18.1 tCO(2)e/d per m(3) digestate) were also recorded in the anaerobic fixed-film reactors. (C) 2019 Elsevier Ltd. All rights reserved

Sequential (anaerobic/aerobic) biological treatment of malt whisky wastewater

The anaerobic treatability of malt whisky distillery wastewater was investigated. Biochemical methane potential (BMP) experiments were conducted both with and without basal medium (BM) to observe the effect of nutrient supplementation. For batch reactors containing no nutrients but only NaHCO3, net total gas production at the end of 29 days were observed as 0.019 m(3) gas/kg COD removed. With nutrient supplemented reactors the net total gas production was 0.020 m(3) gas/kg COD. Continuous reactor experiments were carried out in two stage upflow anaerobic sludge blanket (UASB) reactors. These experiments indicated that the two stage UASB reactor configuration is an efficient system for malt whisky wastewater treatment until up to 33 866 mg/l influent COD concentration. Following the UASB experiments aerobic experiments in batch reactors were also conducted and further COD and BOD removal of up to 55 and 70%, respectively, were achieved

Simultaneous dissolution and uptake of nutrients in microalgal treatment of the secondarily treated digestate

Ulgudur, Nilufer/0000-0003-3410-0598WOS: 000489307800030Anaerobic digestion processes result in large volumes of digestates which still require the development of elaborate and viable management options to improve the sustainability of these processes. Coupling of secondary anaerobic treatment with a microalgal nutrient removal process may serve benefits such as residual biogas and associated greenhouse gas capture from the digestate content, microalgal biomass build-up and its further valorization. This study investigated the applicability a microalgal nutrient removal process in a secondarily treated digestate (the digestate of a digestate) as a complementary unit. The results indicated that up to 100% dissolved reactive phosphorus (DRP), 97.8% total dissolved phosphorus (TDP) and 93.7% ammonium nitrogen (NH4+-N) removal could be attained in the treatment of the digestate of a digestate using microalgal cultures. Folding phosphorus concentrations via dissolution was found to compensate for dilution related phosphorus deficiency for microalgal growth. Microalgal biomass obtained by the end of operation could be concentrated from 6.4-15.5 mg/L to 164.2-502.6 mg/L (2100-7900%) by simple gravity settling which was correlated with the prevalence of agglomerated particles in the size range of 10-100 mu m. The results demonstrated not only the applicability of the microalgal process after secondary anaerobic treatment of the digestate, but also brought about the dissolution concept for nutrients during microalgal growth