Hydraulic- And/or Metabolic-selection Pressures Influence Aerobic Granulation And Its Application In Enhanced Biological Phosphorus Removal (ebpr)

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2006Aerobik granülasyon prosesi, farklı hidrolik-seçme baskılarıyla işletilen üç ardışık kesikli reaktörde (AKR) izlenmiş ve değerlendirilmiştir. Hava yukarı akış hızı haricindeki kesme kuvvetlerinin de önem taşıdığı belirlenmiş ve bunların granülasyon prosesine etkileri, çökeltim hızlarının düşük olduğu, ancak anaerobik fazdaki mekanik karıştırma nedeniyle aşırı (16.6cm/s) veya yüksek (6.5-4.3cm/s) kesme hızları uygulanan yayvan-tip reaktörlerde (HW/D=1.2) incelenmiştir. Çökeltme süresinin (veya hızının; 12.4-37.2cm/dak) etkisi ise, kesme kuvvetinin düşük tutulduğu (1.71cm/s) kolon-tip reaktörde (HW/D=10.3) çalışılmıştır. Aşırı durumlar önlendiği sürece hidrolik-seçme baskılarının granülasyonun tetiklenmesine/gelişimine yardım ettiği ve yeterince biyokütlenin oluşması durumunda metabolik/kinetik seçme-baskılarının prosesi desteklediği, aşırı durumlarınsa granülasyonun başlamasını engellediği veya kararlılığını bozduğu belirlenmiştir. Kolon-reaktörde oluşan yüksek-pH kazası sonrası gerek karbon ve fosfor giderimi açısından, gerekse granül makro-yapısı ve çökelme özellikleri (ÇHİ<40-60mL/g) bağlamında gözlemlenen hızlı iyileşme (2-18gün), granüler biyokütlenin üstünlüklerine işaret etmektedir. DGGE ve FISH yöntemleriyle izlenen mikrobiyal topluluk profillerindeki değişim, granülasyon prosesindeki değişimlerle paralellik göstermiştir. DGGE sonuçları, biyokütlenin floküler durumdan granüler yapıya evrilmesinin sadece makro-yapısal düzeyde değil filogenetik bazlı topluluk yapısı bağlamındanda da gerçekleştiğini göstermektedir. Aşırı biyolojik fosfor giderimine (BAFG) çalıştırılan ve hidrolik-seçme baskılarının düşük tutulduğu üçüncü bir yayvan-tip AKR’de münferit bir aşırı kesme kuvveti oluşumu, sistemde granülasyonu tetikleyen fiziksel unsur olmuş; proses, yükseltilen havalandırma hızı ve düşürülen çökeltme zamanı ile desteklenmiştir. Granülasyonu destekleyen metabolik-seçme baskıları (2-saatlik anaerobik faz, 1-saatlik anaerobik besleme, girişte 15-21.4mgKOİ/mgPO4-P), sistemde anaerobik olarak karbon depolayan, aerobik olarak yavaş çoğalan ve fosfor gideren PAO’ların seçilmesini de garantilemiştir. Sistemde, kararlı aerobik granüler biyokütle ile (ÇHİ<40-50mL/g), %95, %99 ve %71’lik karbon, fosfor ve azot giderimi elde etmek olanaklı olmuştur. Mikroskopik incelemeler, biyokütlenin morfolojik açıdan yüksek bir çeşitlilik arz ettiğini göstermiştir. Sistemdeki baskın türün, geleneksel morfolojileri ve fenotipik özellikleriyle çubuksu PAO’lar olduğu belirlenmiştir.Aerobic granulation process was monitored and evaluated in three SBRs operated with different hydraulic-selection pressures. Shear rates other than superficial upflow air velocity were of significance, and their impact on granulation process was studied in the wide-type reactors (HW/D=1.2), subjected to extreme (16.6cm/s), or considerably high shear (6.5-4.3cm/s) due to mechanical mixing (anaerobic phase), while settling velocities were relaxed. Impact of settling time (or velocity; 12.4-37.2cm/min) was studied in the bubble-column SBR (HW/D=10.3), where shear rate was relaxed (1.71cm/s). Hydraulic-pressures promoted initiation/progress of granulation unless extreme conditions were avoided, and metabolic/kinetic selection-pressures supported the process if enough biomass was obtained, yet extreme conditions prevented initiation- or disturbed stability- of granulation. Rapid biomass recovery (2-18days), after an extreme pH incident in the SBBR, both in terms of C- and P-removal performances, and of granule macro-structure and settling properties (SVI<40-60mL/g), was a direct evidence showing the merits of granular biomass. Results from community profiling via DGGE and FISH were closely related with those of initiation/progress of granulation. DGGE data showed that evolution of the biomass from floccular to granular state was not only in terms of macro-structure, but also in terms of phylogeny-related community structure. A third wide-type SBR was operated for EBPR. Hydraulic-selection pressures were considerably relaxed, and a one-time extreme shearing effect was the initial physical trigger for granulation, which proceeded under a higher aeration rate and a lower settling time. Granulation was further promoted by metabolic-selection pressures (2-h anaerobiosis, feeding anaerobically for 1 h, influent C:P ratios of 15-21.4mgCOD/mgPO4-P), which also ensured proliferation of anaerobically C-storing, aerobically slow-growing and P-removing PAOs. It was possible to maintain a stable granular biomass (SVI<40-50mL/g) while securing 95%, 99% and 71% C-, P-, and N- removal efficiencies, respectively. Microscopic observations revealed a morphological diversity, with the dominant population being the rod-shaped PAOs with their conventional morphological and phenotypic characteristics.DoktoraPh

Microbiological features of aerobic granular EBPR biomass

Tam-&ouml;l&ccedil;ekli konvansiyonel bir biyolojik arıtma tesisinden alınan flok&uuml;ler biyok&uuml;tle ile başlatılan laboratuvar-&ouml;l&ccedil;ekli ardışık kesikli reakt&ouml;rde, anaerobik/aerobik işletme ve fosfor ile besleme sonucu biyolojik aşırı fosfor giderimi (BAFG) elde edilmiştir. &Ccedil;&ouml;kelme s&uuml;resinin kısaltılması (15 dak), ilk hacmin d&uuml;ş&uuml;r&uuml;lmesi (V0 1.8 L), hacimsel karbon y&uuml;klemesinin y&uuml;kseltilmesi (1.41 kg KOİ/m3.g&uuml;n) ve havalandırma kaynaklı kesme kuvvetinin artırılması (0.19 cm/s) ile, fosfor depolayan organizmalar (PAO) gibi yavaş-b&uuml;y&uuml;yen organizmaların varlığı ile iyileşeceği &ouml;ng&ouml;r&uuml;len aerobik gran&uuml;lasyon s&uuml;reci desteklenmiştir. &Uuml;st&uuml;n &ccedil;&ouml;kelme &ouml;zelliklerine (&Ccedil;Hİ&lt; 40-50 mL/g) sahip aerobik gran&uuml;ler BAFG biyok&uuml;tlesi ile kararlı halde %92 karbon, %99 fosfor ve %78 azot giderimi elde edilmiştir. Sistemin biyokimyasal performansının izlenmesine paralel olarak, aerobik gran&uuml;ler BAFG biyok&uuml;tlesinin mikrobiyolojik değerlendirmesi i&ccedil;in morfolojik ve ekofizyolojik incelemeler ger&ccedil;ekleştirilmiştir. H&uuml;cre-i&ccedil;i poli-P (poli-fosfor) ve PHB (poli-hidroksi-b&uuml;tirat) depolarının g&ouml;rsel tespiti i&ccedil;in uygulanan Neisser ve Sudan Black B boyamaları sonucu, biyok&uuml;tlenin morfolojik ve ekofizyolojik a&ccedil;ılardan &ccedil;eşitlilik g&ouml;sterdiği saptanmıştır. Sistemde baskın t&uuml;r, tanımlanmış morfolojileri ve ekofizyolojileri ile &ccedil;ubuksu PAO&rsquo;lardır. Bunların yanısıra, morfolojik olarak glikojen depolayan organizmalara (GAO) benzeyen ancak ekofizyolojik &ouml;zellikler a&ccedil;ısından GAO-fenotipine uymayan tetrad/sarcina-benzeri h&uuml;creler (TFO) belirlenmiştir. Ayrıca, diplo-kokkoidlere, yoğun kokoid topluluklara, az miktarda filamentlere ve &ccedil;eşitli protozoalara rastlanmıştır. Mikroskopik g&ouml;zlemler niteliksel olmakla birlikte, sistemin biyokimyasal d&ouml;n&uuml;ş&uuml;m s&uuml;re&ccedil;leri bağlamındaki niceliksel performansı ile &ouml;rt&uuml;şmektedir. Burada mikrobiyolojik &ouml;zellikleri &ouml;zetlenen aerobik gran&uuml;ler BAFG biyok&uuml;tlesinin, m&uuml;hendislik uygulamaları bağlamındaki &uuml;st&uuml;n &ouml;zellikleri nedeniyle, bu uygulamanın biyolojik atıksu arıtımında yeni ve gelecek vaadeden bir se&ccedil;enek olacağı &ouml;ng&ouml;r&uuml;lmektedir.&nbsp;Anahtar Kelimeler: Biyolojik aşırı fosfor giderimi, aerobik gran&uuml;ler biyok&uuml;tle, morfoloji, ekofizyoloji.A lab-scale sequencing batch reactor (SBR) was inoculated with a floccular biomass obtained from a conventional full-scale biological wastewater treatment plant. Enhanced Biological Phosphorus Removal (EBPR) was obtained through application of a sequential anaerobic/aerobic operational mode together with the metabolic selection strategies of anaerobic feeding (with acetate as sole C-source) and supply of phosphate. The first strategy was applied to maintain absolute elimination of the feast period, where direct and fast growth on acetate was possible together with simultaneous C-storage; the former promoting growth and dominance of fast-growers having a negative impact on aerobic granulation. The merit of the anaerobic-feeding strategy was the possibility of directing the entire flux of externally available C-source to anaerobic C-storage mechanism, thus selecting the micro-organisms with the metabolic capability of taking up the acetate under anaerobic conditions, converting it to intracellular C-storage products (i.e., PHB: poly-hydroxy-butyrate), and then growing slowly on these storage materials at the aerobic phase; the metabolic processes described for the PAO (Phosphate Accumulating Organisms) and GAO (Glycogen Accumulating Organisms) phenotypes. The second strategy was applied to promote dominance of the PAOs in the system. Aerobic granulation process, suggested to be enhanced by the presence and dominance of slowly-growing microorganisms (like PAOs), was supported via lowering operationally determined settling time and initial reactor volume (TS decreased from 30 to 15 min and V0 decreased from 2.9 to 1.8 L), increasing volumetric COD load (from 0.24 to 1.41 kg/m3.d), and slightly increasing the shear rate due to aeration (vSAir increased from 0.14 to 0.19 cm/s). Monitoring the long-term steady state system performance in terms of biochemical conversion processes indicated that it was possible to secure high carbon, nitrogen and phosphorus removal efficiencies (92% COD removal, 99% EBPR, 78% overall N-removal) with the aerobic granular biomass upholding superior settling properties (SVI< 40-50 mL/g). Parallel to the evaluations with regard to biochemical system performance, morphological and ecophysiological examinations via conventional microscopy and chemical staining techniques were also executed to determine the microbiological features of the aerobic granular EBPR biomass, and to help confirm and interpret system performance with respect to presence of different microbial groups. Application of Neisser's and Sudan Black B stains to the biomass samples for visualization of intracellular volutin poly-P (poly-phosphate) granules and lipophilic PHB inclusions, respectively, revealed a microbial community rich in terms of morphological and eco-physiological traits. The dominant phenotype in the system was the PAOs with their conventional rod-shaped morphology and typical EBPR-physiology of being strongly poly-P(-) and strongly PHB(+) at the end of anaerobic phase, whereas being mostly poly-P(+) and partly PHB(-) at the end of the aerobic-period. In addition to the PAOs, tetrad/sarcina-like cells resembling the GAOs in terms of morphological features were also of significance. However, phenotypic properties of these microorganisms were not in line with those of the GAO-phenotype. Thus, the tetrad/sarcina-like cells, which were PHB(-) both at the end of the anaerobic- and aerobic-phases, were named as "TFOs" (Tetrad Forming organisms), a term for morphological differentiation, rather than "GAOs", a term related with functional properties. The PAOs and the TFOs co-existed with some other morphotypes like diplococci-shaped cells, staphylococci-like clustered populations, and a few filaments with an abundancy of 0-1 in accordance with subjective-scoring. Presence of some fixed protozoa like Vorticella campanula and Carchesium spp., typical for activated sludge systems, was also recorded. Despite the microscopic observations were qualitative, they correlated well with the quantitative biochemical performance data. Finally and from an engineering stand-point, operational flexibility of the SBR configuration, superior settling properties of granular biomass thus possibility of working with smaller reaction volumes or with shorter reaction times, and possibility of decreasing aeration related costs due to presence of an anaerobic phase, together demarcate the Aerobic Granular EBPR Technology as a promising biological wastewater treatment alternative enabling to decrease capital and operational costs while securing desired removal efficiencies. Keywords: Enhanced Biological Phosphorus Removal, aerobic granular biomass, morphology, eco-physiology

Model based process optimization of enhanced wastewater treatment plants

Avrupa Birliği&rsquo;ne uyum s&uuml;recinde 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, &ldquo;Kentsel Atıksu Arıtımı Y&ouml;netmeliği, 2006&rdquo; ile uyum s&uuml;recinde olan &uuml;lkemizde azot ve fosfor standartları mevzuatımıza d&acirc;hil edilmiştir. &ldquo;Kentsel Atıksu Arıtımı Y&ouml;netmeliği, 2006&rdquo; kapsamında mevcut tesislerin besi maddesi giderimine y&ouml;nelik olarak geliştirilmesi, yeni kurulacak tesislerin ise besi maddesi giderecek şekilde en uygun arıtma teknolojisi kavramı &ccedil;er&ccedil;evesinde boyutlandırılması gereklidir. Besi maddesi giderimine y&ouml;nelik en uygun arıtma teknolojisi biyolojik prosesler, bunlar arasında en ekonomik &ccedil;&ouml;z&uuml;m ise aktif &ccedil;amur sistemleri olarak tanımlanmaktadır. Bu &ccedil;alışma aktif &ccedil;amur tesislerinin, Avrupa Birliği normlarında performansını sağlayabilecek optimum tasarım ve işletme s&uuml;re&ccedil;lerinin değerlendirilmesini ama&ccedil;lamaktadır. Bu kapsamda, bir &ouml;rnek olarak ele alınan İstanbul Su ve Kanalizasyon İdaresi (İSKİ) Paşak&ouml;y İleri Biyolojik Atıksu Arıtma Tesisi&rsquo;nde mevcut durumda atıksu karakterizasyonu ve sistem performansı deneysel olarak belirlenmiş, elde edilen bilgiler kullanılarak s&uuml;rekli kullanıma uygun olacak model-bazlı tasarım ile işletme sim&uuml;lasyon programları hazırlanmış ve işletme optimizasyonu &ccedil;er&ccedil;evesinde &ccedil;ıkış besi maddesi konsantrasyonlarının d&uuml;ş&uuml;r&uuml;lmesi amacıyla işletme senaryoları oluşturularak &ouml;nerilerde bulunulmuştur. Y&uuml;r&uuml;t&uuml;len senaryo analizleri ile, havalandırma tanklarındaki &ccedil;&ouml;z&uuml;nm&uuml;ş oksijen seviyelerinin uygun ayarlanması, tesisin geri devir denitrifikasyonu prensibi yerine A2O veya UCT tipi sistem şeklinde işletilmesi ile sistem veriminin arttırılabileceği ve dolayısıyla &ccedil;ıkış besi maddesi konsantrasyonlarının azaltılabileceği belirlenmiştir.&nbsp;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 &ldquo;The Council Directive (91/271/EEC)&rdquo; 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 Paşak&ouml;y 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 Paşak&ouml;y 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 Paşak&ouml;y 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 Paşak&ouml;y 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.&nbsp;Keywords: Paşak&ouml;y wastewater treatment plant, wastewater characterization, model based optimization, process control

Estimation of hazardous waste factors

The first step of establishing a reliable waste inventory is the determination of waste factors. This study presents a detailed survey for the estimation of waste factors from different manufacturing sectors. Waste factors were obtained in units of “tons of hazardous waste generated per 1 ton of production of related industry” using waste generation figures given by Turkish Statistics Institute (TURKSTAT) and production figures given by The Union of Chambers and Commodity Exchanges of Turkey (TOBB). Estimated waste factors were cross-checked with the information obtained from field surveys conducted for basic metal and metal finishing industries. The hazardous waste factors obtained from TURSTAT and TOBB data for Basic Metal Industries (37) and Manufacture of Fabricated Metal Products, Machinery and Equipment (38) are 0.0035 and 0.0068, respectively. From the field surveys, the average hazardous waste factor of eight facilities in category (37) is estimated as 0.054 and that for six facilities in category (38) is determined as 0.007. In a parallel evaluation, hazardous waste factors obtained from production and waste generation figures declared by nine facilities in Basic Metal category (37) and 16 facilities in Metal Finishing category (38) are calculated as 0.017 and 0.012, respectively. These varying results indicate that for reliable waste factors estimation, hazardous waste generation and production figures of the industries should be attained correctly and checked with various data obtained from different sources before they are used for establishing the waste inventories. © 2011 Taylor & Francis Group, LLC

Effect of chemical treatment on the aromatic carbon content and particle size distribution-based organic matter profile of Olive mill wastewaters

The present experimental work was carried out to examine the physicochemical treatability of a high-strength olive oil mill wastewater (OMW). Firstly, the wastewater was subjected to environmental characterization and particle size distribution-based COD-TOC-UV254-UV280 analyses. The following treatment schemes were selected for the study: Coagulation-flocculation in the presence of anionic and commercial polymers at varying pH and coagulant/polymer dosages; Fenton treatment at different pH's and Fe(II): H2O2 concentrations as well as electrocoagulation using stainless steel electrodes at different electrolyte concentrations and current densities. Results of the study have indicated that none of the investigated physicochemical treatment methods was capable of removing the organic carbon content of the wastewater by more than 30% in terms of COD and 20% in terms of TOC that is at least partially attributable to the high, soluble organic carbon content of the wastewater. Alternative treatment processes and/or combinations have to be explored for effective treatment of OMW effluent. © by PSP

Assessment of organic carbon removal by particle size distribution analysis

Particle size distribution (PSD)-based fractionation, an alternative methodology in wastewater characterization, was employed to gather detailed information on the organic matter content of a raw olive mill wastewater (OMW) and to investigate the changes brought about in this characteristic after application of certain chemical treatment alternatives, namely, lime precipitation-coagulation, Fenton oxidation, and electrocoagulation. PSD-based analysis of the untreated OMW demonstrated that more than two-thirds of its organic carbon content, measured as chemical oxygen demand (COD) (69%), total organic carbon (TOC) (74%), as well as antioxidant activity (AOA) (74%) caused by the polyphenolic carbon fraction, was at the soluble range (<2 nm). Treatability experiments, with maximum overall removal efficiencies below 50% even under optimized conditions, indicated that none of the applied chemical pretreatment methods was sufficiently effective in removing the organics from the investigated OMW. Nonetheless, PSD-based fractionation of the pretreated samples provided an insight about the treatment alternatives and the size fractions where they performed better. Electrocoagulation was capable of removing particulate and colloidal matter and provided a relatively higher overall performance with 23, 20, and 34% decreases in COD, TOC, and polyphenol contents of the OMW, respectively. Fenton process, on the other hand, showed a lower overall performance in terms of COD and TOC removal (17 and 15%, respectively), yet it was significantly effective on the soluble fraction, and thus more successful in removing the polyphenols mostly originating from the soluble range, with an overall efficiency of 42%. Based on these observations, PSD analysis was suggested as a useful tool to perform detailed wastewater characterization, as well as to differentiate between specific impacts of different pretreatment processes and help choose between alternatives, especially when a particular pollutant is targeted. Copyright 2009, Mary Ann Liebert, Inc

Effects of high-concentration influent suspended solids on aerobic granulation in pilot-scale sequencing batch reactors treating real domestic wastewater

The aim of this study was to investigate the effect of high-influent-concentration suspended solids (SS) on the cultivation, structure and long-term stability of aerobic granular sludge (AGS). Cultivation and long-term stability of AGS were monitored in two pilot-scale sequencing batch reactors fed with raw (R1) and settled (R2) domestic wastewater, representing high and medium SS content, respectively. The real domestic wastewater had high chemical oxygen demand (COD) content (1100 +/- 270 mg COD L-1). Aerobic granular sludge was cultivated in 44 days (R1) and 25 days (R2) under the conditions of high settling velocity (18 m h(-1)) and high organic loading rate (OLR) (2.1-2.4 kg COD m(3) day). The AGS in both reactors had similar structural properties during long-term operation and remained structurally and functionally stable during the last five months of operation. Comparative evaluation of the results indicated that the high influent SS content of the real domestic wastewater had a positive influence on maintaining significantly lower SVI30 and relatively lower effluent SS concentration. Moreover, a higher influent SS content resulted in smaller mature granules during the stable period. Microbial community analyses helped to understand the aerobic granular sludge structure and showed that the sludge retention time and OLR affected the granular sludge population. The high influent SS increased biomass detachment from the granular sludge surface and caused wash-out of some bacteria colonizing the exterior of the granular sludge. (C) 2017 Elsevier Ltd. All rights reserved

Resource recovery from an aerobic granular sludge process treating domestic wastewater

This study presents the application of resource recovery from domestic wastewater such as irrigation water, structural extracellular polymeric substances (EPS), and polyhydroxyalkanoates (PHAs). The resource recovery system consisted of an aerobic granular sludge (AGS) reactor processing domestic wastewater and an external membrane reactor receiving the AGS effluent. The AGS effluent contained large numbers of biomass patches detached from the granular sludge. Therefore, the external membrane served to eliminate the biomass patches and individual bacteria from the AGS effluent. The permeate of the membrane reactor was compared with the national irrigation water standards. The results showed that the membrane effluent was suitable to be used as irrigation water, but the boron parameter should be checked for long-term irrigation. Extracellular polysaccharides recovered from the granular sludge were characterized as structural EPS. The analyses showed that PHA accumulating organisms, namely Uncultured Candidatus Competibacter sp. and Competibacteraceae, were dominant in the AGS reactor, and the PHA content of the AGS was approximately 10 % when operated under high organic loading rate conditions. PHAs, therefore, may also be obtained from AGS. For the management of membrane concentrate and zero-waste discharge approach, it is recommended to investigate the recovery possibilities of structural EPS and PHA biopolymers from the membrane concentrate further because the effluent of AGS contained mostly biomass patches detached from granular sludge