A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water

Karaelmas Fen ve Müh Derg 614149 2016 Karaelmas Fen ve Mühendislik Dergisi Journal home page httpfbdbeunedutr Research Article Corresponding Author kadirozdemir73 yahoocom Received Geliş tarihi 09022016 Accepted Kabul tarihi 11032016 A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Seramik Ultrafiltrasyon Membran Sistemi İle Yüksek Kalitede İçme Suyu Üretimi Kadir Özdemir Bülent Ecevit University Department of Environmental Engineering Zonguldak Turkey Abstract In this study ultrafiltration UF with ceramic membranes was used to produce safe and quality drinking water Te small scale UF membrane system had a capacity of 144 m3d Te UF membrane filtration process includes two parts a tubular ceramic membrane formed by a porous support αalumina and a tube reactor chamber 10 m long and 5 cm in diameter to generate electrocoagulation In this study raw water treated with smallscale UF membrane systems was taken from the Alibey Lake in Istanbul City Turkey Te system removed 75 to 85 of ferrous and turbidity contaminants Te decrease in pH chloride and total hardness was similar but ammonia and manganese removal was much lower than expected Nevertheless removal of total organic carbon TOC was the best only 15 remained Te UF ceramic membrane filtration system produced water that met Turkish Standards TS266 regulated standards for drinking water in Turkey Chemical cleaning with a cleaninplace CIP operation was successful in removing fouling and scaling materials in ultrafiltration UF ceramic membrane Te UF ceramic membrane filtration system produced water with no added chemicals as a coagulant and disinfectant Indeed producing water with no chemicals and disinfection byproducts DBPs like trihalomethenes THMs is better for human health than the approaches used at conventional drinking water treatment facilities Keywords Ceramic membrane Electrocoagulation Ultrafiltration Water treatment Water quality Öz Bu çalışmada tübüler seramik membrane kullanılarak oluşturulmuş küçük ölçekli Ultafiltrasyon UF membran sistemi ile kaliteli bir içme suyu üretilmesi hedefenmiştir Bu amaçla kullanılan UF membrane filtrasyon sistemi 144 m3 günlük bir su üretim kapasitesine sahiptir Bu UF membrane filtrasyon sistemi αalumina içeren gözenekli bir destek tabakası ve elektrokoagülasyon prosesini gerçekleştirmek için 5 cm çapında ve 10 m uzunluğunda tubüler bir reactor odasından meydana gelmektedir Bu çalışmada UF membran sistemi ile arıtım amaçlı olarak kullanılacak ham su İstanbul şehrinin önemli içme suyu kaynağı olan Alibeyköy baraj gölünden sağlanmıştır Bu sistem ile yapılan deneysel çalışmalarda demir ve bulanıklık giderim oranlarının sırası ile 75 ve 85 olduğu gözlenirken pH klorür ve toplam sertlik parametre değerlerinde herhangi bir değişim olmadığı ortaya konulmuştur Bununla beraber Toplam Organik Karbon TOK değerlerinde o yaklaşık 15lik bir düşüş oldğu gözlenirken Amonyak ve Mangan değerlerinde ise tahmin edilenden daha düşük bir giderim verimi sağlandığı tespit edilmiş olup arıtma sonunda alınanan su numunelerinin bakteriyolojik olarak temiz olduğu rapor edilmiştir Bu çalışmanın en önemli sonuçlarından biri herhangi bir kimyasal ve dezenfektan kullanmadan UF membrane filtarsyon sistemi ile üretilen suyun TS266 içme suyu standartlarında yer alan temel su kalite parametre değerlerini sağlamış olmasıdır Bununla beraber konvansiyonel içme suyu arıtma tesisleri ile karşılaştırıldığında dezenfektan olarak klor kullanımı sonucu meydana gelen Trihalometanlar gibi özellikle insan sağlığı üzerinde kanserojenik etkiye sahip dezenfeksiyonyan ürünlerinin olmaması UF membrane sistemi ile üretilen içme suyunun sağlıklı güvenli ve kaliteli olduğunu ortaya koymaktadır Anahtar Kelimeler Seramik membran Elektrokoagülasyon Ultrafiltrasyon Su arıtımı Su kalitesi Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 42 1 Introduction Te lack of safe potable water and increased demand as well as higher standards have increased the need for membrane technologies to produce high quality drinking water Bagga et al 2008 Moreover conventional water treatment processes including coagulationfocculation sedimentation fltration and disinfection processes are not very efective at meeting these stringent regulations Tus use of pressure driven membrane processes such as microfltration MF and ultrafltration UF are increasingly popular in drinking water treatment Jacangelo et al1995 Yuan and Zydney 1999 Zularisam et al2007 Furthermore the chlorine used as a disinfectant in conventional water treatment plants reacts with Natural Organic Matter NOM and produces disinfection byproducts DBPs that are carcinogenic and mutagenic Rook 1974 Membranebased fltration such as microfltration MF ultrafltration UF nanofltration NF and reverse osmosis RO have been investigated as a potential alternative to conventional water treatment options for small communities Membrane installations are easily automated Te UF NF and RO remove signifcant levels of trihalomethene THM precursors from drinking water supplies and deliver excellent microorganism control Hence membrane fltration removes turbidity reduces THM precursors and disinfects in a single step Richard and Paul 2003 Small scale membrane treatment systems such as MF and UF systems are highly efective for turbidity as well as bacteria and virus removal from surface waters such as rivers and lakes Jacangelo et al1991 Madaeni 1999 Neranga et al2014 Zhu et al2005 Tey also indirectly assist in DBPs control by lowering chemical disinfection requirements for the fltered water Furthermore the goals of smallscale treatment systems are simplicity no chemicals dynamic remote control long service interval times and low energy use Ceramic membranes have several advantages over poly meric membranes such as high chemical mechanical and thermal resistance as well as higher permeability rates than polymeric membranes Nevertheless ceramic membranes are substantially more expensive though this may be com pensated by their higher fuxes and extended lifetimes Van Der Bruggen et al2008 Kim et al2007 BarredoDamas et al2012Porous ceramic membranes are an important membrane category that is of particular interest in applica tions requiring high chemical or thermal stability Pagana et al2006 Shams Ashaghi et al2007 Tubular ceramic membranes are formed by a porous support generally a Al2O3 with one or more layers of decreasing pore diameter and an active or separating layer αalumina zirconia etc covering the internal surface of the tube Te use of ceramic membranes for microfltration and ultrafltration is of great interest because they can remediate fouling problems asso ciated with those processes and solutions ie adsorption or deposition of macromolecules on the membrane poressur face Tis strongly reduces volume fow and requires harsh chemicals and high temperatures for cleaning In turn this damages the polymeric membranes Richard et al 2013 Verberk et al 2002 Tus the use of these systems is still limited by fouling It has also been suggested that viruses are etiologic agents responsible for the majority of unidentifed outbreaks because they are typically more difcult to analyze than bacterial pathogens It is difcult to remove viruses by fltration because of their small size Tanneru and Chellam 2012 EPA 2006 Urase et al 1996 Mi et al 2005 Pontius et al 2009 Electrocoagulation EC has been widely studied in water and wastewater treatment to remove heavy metals organics bacteria hardness turbidity and other contaminants Tsouris et al 2001 Can et al 2003 Al malack et al 2004 Mills 2000 Zhu et al2005 EC has been widely studied in water and wastewater treatment Here the electrodes are consumed as the coagulant is generated and precipitated No liquid chemicals are added No basic chemical are used and the pH does not have to be adjusted Mills 2000 Zhu et al2005 Additionally EC pretreatment is an alternative to conventional chemical coagulation using Fe or Al salts prior to MF or UF membrane systems In electrocoagulation the coagulant Fe or Al is generated by electrolytic oxidation of an anode Te advantages of EC over conventional chemical coagulation include 1 no addition of lime ferric and coagulant chemicals 2 no change in bulk pH 3 simple operation and maintenance and 4 low sludge generation Bagga et al 2008 Cazinares et al 2006 Hu et al2013 Te most important advantage of EC pretreatment is the reduction in fouling problems that occurs in smallscale MF and UF membrane systems Bagga et al 2008 Al Malack et al 2004 Te aim of this study is to provide high quality potable water without added chemicals via a smallscale membrane treatment system consisting of UF ceramic membranes Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 43 We compared the treatment performance of conventional treatment process in Kagithane Water Treatment Plant KWTP and UF membrane fltration process and characterized the pH turbidity total organic carbon TOC and total hardness 2 Materials and Method 21 Source Water Quality Water quality is an important factor in determining the treatment performance of smallscale UF membrane systems For this study raw water taken from the Alibey Lake in Istanbul City Turkey was used as feed water for smallscale UF membrane systems during the winter period January February and March in 2011 Tis surface water supply is one of the major drinking water sources of Istanbul City Also Alibey Lake is one of the most important water reservoirs in Istanbul and provides up to 700000 m3day of raw water to produce drinking water Raw water samples were collected by plant personnel as a grab sample and shipped to a water quality laboratory Istanbul Water Utilities Administration ISKI on the same day Samples were stored in the dark at 4oC to prevent biological activity prior to analysis 22 Membrane In this study the smallscale UF membrane fltration system used to purify Alibey Lake water was composed of tubular ceramic membranes formed by a porous support α Alumina Fig 1 Tese membranes consist of 580 mm long channels with an external diameter of 4 mm and 2 mm Teir efective pore sizes are 004 µm and the efective flter area is 18 m2 as surface area per volume m 2 m 3 Table 1 lists other relevant properties of these membranes 23 Electrocoagulation EC unit Coagulation process in the EC used a dedicated tube reactor Tis reactor chamber consists of a 10 m long tube 5 cm in diameter Te rodshaped iron anodes are 50 cm long Te cylindrical stainless steel cathodes are placed in a electrode chamber and are 1 m long Te total anode surface area was 100 cm2 and the current density was typically 015 mAcm2 During iron EC the following electrochemical reactions occur Anode Fe0 s Fe33e Fe3 3H2O FeOH3 s 3H Cathode 3H2O 3e 3OH 32 H2 Overall Fe03H2O FeOH3s 32 H2 24 Experimental UF Membrane Filtration Setup UF fltration experiments were conducted in a multi tubular ceramic membrane Te process was designed for a fux of 60 Lm2hr As seen in Fig 2 surface lake water was taken from the 1000 L tank with a peristaltic pump and transferred into the reactor chamber for EC processing In the meantime the iron electrodes are sacrifced at this step at a concentration of 4 ppm In this way it is possible to have dynamic inline process control as well as a short residence time in the tube reactor for foc growth After coagulation the raw water was passed into the second part including the UF ceramic membrane Te fow level and temperature sensor were located at the frst part of the reactor water levels in the reactor were held constant Permeating and backwashing operations were performed automatically with an automatic control system To save Figure 1 Tubular ceramic membrane Table 1 Typical characteristics of the membrane used in this study Parameter Value Unit Material Ceramic aAl2O3 Pore size nominal 004 µm Efective area 18 m2 Feed water fux 60 Lh1m2 Max operating pressure 065 bar Max operating temperature 30 0C pH range 411 Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 44 pH total hardness chloride manganese and ammonia were measured according to the literature APHA 1998 3 Results 31Treatment performance of the UF ceramic membrane fltration system In this study we measured the quality of the water produced by the UF ceramic membrane fltration system Alibey Lake water was treated with the UF ceramic membrane fltration system and Table 2 details physicochemical characteristics of raw Alibey Lake water versus the treated water As seen in Table 2 the turbidity values drop from 65 NTU to below 1 NTU Te concentrations of ferrous and manganese were 003 and 005 mgL respectively in clean water In other words the removal percentage of turbidity wasapproximately 85 Te conductivity was 740 µScm1 and the pH was 771 on average in treated water Te total hardness and chloride in treated water remained relatively constant Table 2 Te drinking water was produced from Alibey Lake water with the UF ceramic membrane fltration Fig 3 illustrates energy the fltering process was planned at a low trans membrane pressure TMP Up to 025 bar of TMP was used for the expected focsizes Te membrane cleaning process used flter backwashing and chemical cleaning with an automatic control system Filter backwashing was automatically performed every 20 minutes with water treated by the UF membrane system Chemical cleaning of the membrane was automatically carried out using 200 ppm NaOCl and 500 ppm H2O2 using chemical dosage pumps every 15 hours Tis avoids membrane fouling from microbial contamination 25 Analytical Methods Te TOC analysis used high temperature combustion according to Standard Methods SM 5310 B using a Shimadzu TOCVCPH analyzer equipped with an auto sampler APHA 1998Te total iron was measured using atomic absorption spectroscopy AAnalyst 300 Perkin Elmer Corp CT after acidifying the samples to pH2 using HNO3 according to Method 3111 in the Standard Methods APHA 1998 Turbidity was determined by with a Termo turbidimeter according to Standard Methods Te Figure 2 A schematic diagram of the UF ceramic membrane fltration system Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 45 As shown Fig 4 the pH of the water was not signifcantly infuenced by treatmentthe results were within the known target limit for Turkish Standards 266 TS266 regulated standards for drinking water in Turkey that turbidity of Alibey Lake water did not exceed 03 NTU at the efuent of the UF ceramic membrane fltration system To better compare the turbidity values we plotted the data Fig 3 tenfold Table 2 Te relevant parameters used to evaluate the UF ceramic membrane fltration system including pre and posttreatment water Parameters Units Raw Water Average Product water Average Standarts for drinking water in Turkey TSI266 pH 782 771 6585 Turbidity NTU 654 097 5 Conductivity µScm 651 664 6502000 Total Hardness mg CaCO3 L 15335 1555 300 Chloride mgL 8014 7982 250 Ammonia mgL 032 024 05 Dissolved Oxygen mgL O2 1052 111 Not defned TOC mgL 612 518 Not defned Iron mgL 011 003 02 Manganese mgL 0067 005 005 TColiBacteria cfu100 mL 20000 None None Figure 3 Turbidity values NTU in raw water and treated water with UF membrane fltration system Figure 4 pH values in raw water and treated water with a UF membrane fltration system Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 46 generate iron in proportion to the current by operating it continuously at diferent current values Te process has been designed for a fux of 60 Lm2hr Te Fe electrodes of the system are sacrifced during the process at a concentration of 4 ppm Tis gives dynamic inline process control and a short detention time as needed for foc growth To determine the current efciency the amount of iron generated was calculated using Faradays Law Eq1 m I x t xMW ZxF Eq1 Where m is the mass in grams of Fe generated at a specifc current I amps over a time interval t seconds Term Z is the number of electrons transferred per Fe atom MW is the molecular weight 5585 g mol1 and F is Faradays constant 96486 C eq1 Te desired iron concentration was obtained by adjusting the operating current and fow rate of the source water For example when the feed fow rate was 250 mLmin and the operating current was 015 A the iron concentration was Tere was no change in total hardness during the membrane fltration as occurs with chloride treatment Fig 5a b In other words both parameters had similar removal percentages Ammonia and manganese removal through the ceramic UF membrane fltration was much lower than expectedonly 25 was removed Fig 6ab Of all of the water quality metrics turbidity had the highest removal ratio at 85 Fig 7 the TOC removal ratio was only 15 Moreover the performance of the UF membrane system was much lower for the TOC parameter Fig 8 Tis result is expected because the electrocoagulation time is very short Tis also means that it is not enough time for the needed focgrowth in the EC due to low retention time No bacteria were found in the UFfltered water despite the lack of chlorine Tus no disinfection byproducts were present in the UF water that might result in adverse health efects 32 Operation of the EC unit After designing the EC unit it was tested for its ability to Figure 5 A Total hardness mg CaCO3L and B Chloride mgL values in raw water and treated water from the UF membrane fltration system Figure 6 A Ammonia mgL and B manganese mgL in raw water and treated water A A B B Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 47 and 20 minutes After 5 cycles of operation the system was automatically backwashed for 2 minutes As shown in Fig 10 when the TMP was 065 bar the system automatically switches to chemical cleaning mode to remove bacteria and or viruses from the membrane Chemical cleaning with cleaninplace CIP operation is the usual method to restore the membrane permeability Tere are several reagents including alkalis acids oxidants chelating agents and surfactants that could be used for CIP Zhu et al2005 Jacb and Jafrin 2000 Many aspects should be considered when selecting CIP reagents Te two main factors are feed composition and the composition of the fouling layer Zhu et al2005 In this study H2O2 and 36 mgL Fig 9 presents FeIII concentration as well as the EC unit operating current Te Fe III formation at 250 mLmin is a function of EC operating current 33Efects of backwashing and chemical cleaning on the UF ceramic membrane fltration Te backwashing and chemical cleaning processes were conducted automatically in the UF membrane system to control membrane fouling Ceramic membranes have a higher permeability versus traditional polymeric membranes if the backwash interval is extended Zhu et al 2005 Jegatheesen et al 2009 In this study the UF ceramic membrane fltration was operated with Alibeyköy Lake water for 24 hours One cycle required between 15 Figure 7 Total iron values mgL in raw water and treated water Figure 8 TOC mgL values in raw water and treated water treated Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 48 fltration Te TMP during backwash never exceeded 035 Bar Te TMP after every backwash at the start of the fltration cycle varied between 017 and 019 bar 4 Conclusion In this study we produced potable water in accordance with EC standards using UF ceramic membrane fltration system with no added chemicals We studied the performance metrics of the UF membrane Except for the TOC and ammonia all of the relevant water parameters including pH turbidity Fe and manganese met the required specifcations Moreover the Fe and turbidity were removed at nearly 75 and 85 respectively Bacteria were not found in the treated water despite the lack of chlorine During EC the Fe electrodes are consumed at concentration of 4 ppm Moreover the Fe III formed at 250 mLmin is a function of the EC unit operating NaOCl were selected because they have strong chemical inertia and do not afect the thermal stability of the ceramic membrane Te use of chemicals was limited to cleaning and the total amount needed can be extrapolated from the volume of the flter elements During this experiment the chemical concentration was adjusted to pH 2 and 500 ppm H2O2 and 200 ppm NaOCl Under normal circumstances we used 15 minutes of soaking Figure 10 shows changes to the TMP as a function of time 0432 hours during operation As shown the Figure 10 the TMP increases after chemical cleaning Te TMP decreased from 065 to 01 bar It also demonstrated that a large number of microorganisms and colloids resulting from membrane fouling were removed by chemical cleaning Fig 10 Furthermore TMP during the fltration tests varied between 017 Bar and 023 Bar Te fow was kept constant during Figure 9 Fe III generated at 250 mLminute as a function of EC operating current Figure 10 TMP changes as a function of time during UF ceramic membrane fltration Özdemir A Ceramic Ultrafiltration Membrane System for Producing High Quality Drinking Water Karaelmas Fen Müh Derg 2016 614149 49 Kim HG Park C Yang J Lee B Kim SS Kim S 2007 Optimization of backfushing conditions for ceramic ultrafltration membrane of disperse dye solutions Desalination 202 150155 Madaeni SS 2009 Te application of membrane technology for water disinfection Water Res 33 2 301308 Mi B Marinas BJ Curl J Sethi S Crozes G Hugaboom D 2005 Microbial passage in low pressure membrane Elements with Compromised Integrity Environ Sci Technol 39 11 42704279 Mills DA 2000 New 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