Clean bed head-loss of various filter media

Granüler filtrasyon su arıtımında yaygın olarak kullanılan bir arıtma yöntemi olup bu prosesin tasarım ve işletmesi açısından yük kayıpları büyük önem taşımaktadır. Bu çalışmada laboratuvar ölçekli bir filtrasyon kolonunda sık kullanılan farklı filtre malzemeleri için temiz yatak yük kayıpları belirlenmiştir. Karışık boyutta elde edilen malzemelerin eleme işlemi ile fraksiyonlarına ayrılması sonucu 6 kum, 5 perlit, 8 garnet ve 3 kırık cam fraksiyonu elde edilmiştir. Karşılaştırma amacıyla küreler ile de deneysel çalışma yürütülmüştür. Deney düzeneği filtredeki hidrolik koşulların da etkisini incelemek amacıyla yüksek hızlarda da veri elde edilebilecek şekilde tasarlanmıştır. En yüksek yük kayıpları malzemenin çapına da bağlı olarak 0.1 m/sn filtre hızında 5-6 m olarak gözlenmiştir. Filtrasyon hızı ile yük kaybının lineer olmayan bir şekilde değiştiği tüm malzeme türleri ve her bir fraksiyon için teyit edilmiştir. Aynı zamanda gözeneklilik ve tanecik çapı parametrelerinin yük kaybı üzerindeki etkisi incelenmiştir. Yaklaşık olarak aynı tanecik çapındaki kum, perlit ve garnet yataklarında yük kaybı oluşumu karşılaştırmalı olarak incelenmiş ve gözenekliliğin en düşük olduğu kum yatakta en yüksek yük kaybı elde edilmiştir. Küresellik ile ifade edilen malzeme şeklinin gözenekliliği etkileyen bir unsur olduğu ortaya konmuştur. Tane çapının yük kaybı üzerindeki etkisi kum ve garnetin farklı fraksiyonlarından oluşan kapsamlı bir aralıkta incelenmiş ve her iki malzeme türü için de tane çapı küçüldükçe yük kaybının arttığı gözlenmiştir. Anahtar Kelimeler: Filtrasyon, granüler malzeme, temiz yatak, yük kaybı, gözeneklilik, küresellik.Granular filtration is a process that is widely used for removing particulate matter from water. The granular media filtration process is affected by the properties of the filter media including grain size, bed porosity and specific surface area. Especially, determination of clean bed head loss is important in the design and operation of filters. Clean bed head-loss of various common filter media obtained from several sources was determined in a laboratory scale filter column. The cylindrical column made of plexiglass was 4 cm in diameter and 2 m in height. It was connected to a water tank through a series of pipes and valves. The water tank was filled with tap water and served as a water reservoir for the filtration column. A constant speed centrifugal pump drew water from the tank and pumped it to the top of the column. In addition, the system allowed the water to flow upwards in the column to achieve various porosity ranges as well as to fluidize the media and bleed any residual air. In the filtration cycle the water travelled down the filter column through a bed of media and was then returned to the water tank. A cartridge filter was used to trap possible suspended solids thus ensuring the recirculated water remained clean. To measure the head-loss across the media bed as water passed through it, piezometer taps at the top and bottom of the media were connected to a water-air manometer, as well as a mercury manometer and a differential pressure transducer. Flow rate of the equipment being used determined the choice of the instrument. Flow rate was measured by an electromagnetic flow meter across the range of 0.17-17L/min. Because the density and dynamic viscosity of the fluid changes with temperature, a Pt-100 thermometer was installed on the column and temperature was monitored continuously. Once the media had been loaded in the column, the filter was operated in the down flow mode and the flow rate was gradually increased and then decreased to a minimum value prior to head-loss measurements. As such the compaction of the media during the experiment was prevented. The porosity of the filter bed was determined separately for each run using the weight of the filter media introduced to the column, the height of the filter bed, the inside diameter of the filter column and the specific gravity of the media. The media which were normally composed of different grain sizes were sieved and 6 fractions of sand, 5 fractions of perlite, 8 fractions of garnet and 3 fractions of crushed glass were obtained. Experiments were also conducted on using glass beads for comparison. Experimental set-up was designed so as to obtain data at high filtration rates in order to evaluate the hydraulic behavior in the column. The maximum head-loss was measured as 5-6 m for 0.1 m/s filter rate. Head-loss measurements were made? for a minimum of three porosities for each medium. These porosities corresponded to the maximum compaction that could be obtained by directly tapping on the column, gradual shut off of backwash water and an intermediate value between these. For each type of medium and fraction it was confirmed with literature that there exists a non-linear relationship between filter rate and head-loss. Besides, effect of porosity and grain size on head-loss was assessed. As the bed consists of uniform particles when a sieved fraction of medium is used instead of its mixed form, more robust evaluations were possible. The sensitivity of head-loss to porosity was examined via extensive experiments. The head-loss occurrence in beds of sand, perlite and garnet of approximately same grain size were compared to each other. The highest head-loss was observed for the bed composed of sand due to the lowest porosity value. Also, experiments were conducted with approximately same size of sand and glass beads separately but at the same porosity. It was noticed that sand caused higher head-losses, which were more easily observed at higher filter rates. Different porosities were achieved by directly tapping to the column or gradual shutoff of the backwash water. Also, it was verified that grain shape defined by sphericity affected the porosity. The sphericity of crushed glass being an angular medium was found to be around 0.5. The porosity range obtained with this media showed to be higher than other filter media. To evaluate the effect of grain size on head-loss, several fractions of sand and garnet were compared and an inversely proportional relation was observed independent of the type of the medium. Keywords: Filtration, granular material, clean bed, head-loss, porosity, sphericity

Hydraulic Behaviour Of Non-spherical Particles Through Fixed-beds

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu çalışmada Ergun denkleminin mevcut katsayıları ile sabit yataklarda küresel olmayan malzemeler için geçerliliği araştırılmıştır. İlk aşamada denklemin küresel malzemeler için kullanılıp kullanılamayacağını araştırmak üzere 9 farklı boyutta cam küre ile çalışılmış ve denklemin mevcut katsayıları ile küreler için oldukça başarılı neticeler verdiği belirlenmiştir. Bu bulgu ile aynı zamanda kullanılan deneysel düzeneğin ve yöntemin güvenilirliği de teyit edilmiştir. İkinci aşamada farklı şekillerde (küp, silindir, halka, tablet, dikdörtgenler prizması, üçgen prizma) ve boyutlarda olmak üzere özel olarak imal edilmiş 11 çeşit düzgün geometrik malzeme ile sabit yatak deneyleri yürütülmüştür. Düzgün geometrik şekillerin küreselliği teorik olarak hesaplanabildiği için değişik hızlarda meydana gelen yük kayıpları Ergun denklemi ile hesaplanmış ve deneylerde ölçülen yük kayıpları ile karşılaştırılmıştır. Kullanılan malzemelerden her biri için Ergun denklemindeki katsayıların ne derece geçerli olduğu ve beklenebilecek hata oranları tespit edilmiştir. Teorik küresellik ve teorik çap değeri bilinen düzgün şekilli malzemelerden oluşan sabit yataklar için Ergun denkleminin yük kayıplarını % 11 - 55 aralığında değişen hatalar ile tahmin edebildiği görülmüştür. Bu kadar geniş bir hata aralığı Ergun denkleminin mevcut k1 ve k2 katsayıları ile küresel olmayan malzemeler için kullanılamayacağı sonucuna varılmasını sağlamıştır. Son aşamada ise su filtrasyonunda yaygın olarak kullanılan malzemelerle deneyler yürütülmüştür. Değişik boyutlarda ve değişik kaynaklardan elde edilmiş 6 fraksiyon kum, 5 fraksiyon perlit, 8 fraksiyon garnet ve 3 fraksiyon kırık cam ile gerçekleştirilen deneylerde Ergun tarafından teklif edilen k1 ve k2 değerlerini kullanarak yük kaybı verilerinin ne kadar iyi temsil edilebildiği araştırılmıştır. Ergun denkleminin mevcut katsayıları ile kum, perlit ve garnet için yük kaybını tahmin etmekte başarılı olduğu görülmüştür.In this study, the validity of Ergun equation in fixed beds for non-spherical particles with its original coefficients was examined. First, experiments were conducted with 9 different sized glass spheres in order to determine the validity of the equation for spherical particles and it was found out that the equation was fairly successful. This finding also confirmed the reliability of the experimental set-up and the method applied. In the second stage, fixed bed experiments were conducted with 11 types well defined geometric shaped particles of different shapes (cube, cylinder, hollow ring, tablet, rectangular prism, triangular prism) and sizes. As the sphericity of the well defined geometrical particles can be calculated theoretically, head-loss measured at various flow rates were compared with the head-loss calculated by Ergun equation. The possible error and the validity of the coefficients in the Ergun equation was determined for each type of media. It was found that Ergun equation could predict the head-loss within 11%-55% for fixed beds made of well-defined geometric shapes whose sphericity and equivalent diameter are calculated theoretically. Such a wide range in the prediction lead to the idea that Ergun equation can not be used for non-spherical particles with the proposed coefficients. Finally, experiments were carried on a variety of media used in water filtration. 6 fractions of sand, 5 fractions of perlite, 8 fractions of garnet and 3 fractions of crushed glass with various sizes were obtained from several sources. It was examined how strongly the headloss data could be presented by using the coefficients as proposed by Ergun. The equation was found to be successful in predicting the head-loss for sand, perlite and garnet.DoktoraPh

A revisit of pressure drop-flow rate correlations for packed beds of spheres

A large number of correlations can be found in the literature for the calculation of pressure drop caused by fluid flow through packed beds. New correlations continue to be proposed and there appears to be no general agreement regarding which correlation is the most accurate. In this work, experiments have been carried out with water using glass spheres of nine different sizes, varying from 1.18 mm to 9.99 mm. For each size, experiments were repeated with at least two different porosities. A total of 38 correlations from the literature have been evaluated and a uniform notation was established to facilitate the comparison of the correlations. While the Ergun equation remains the most widely-used correlation, the data collected in this work shows that it should not be used above Re-m approximate to 500. A simple new equation (f(v) = 160 + 2.81Re(m)(0.904)) is proposed to represent the data collected in this work. The new equation yields the smallest mean error among all the correlations considered here. While a substantial amount of the data collected in this work involved D/d(p) ratios less than 10, the correlations that fit the current data best do not have any wall effect correction terms. (C) 2015 Elsevier B.V. All rights reserved

Overcoming challenges in mainstream Anammox applications: Utilization of nanoscale zero valent iron (nZVI)

Although Anammox process is a proven technology for sidestream nitrogen removal, the process faces challenges for mainstream applications in sewage treatment plants (STPs). The aim of this study was to investigate the effect of zero valent iron nanoparticles (nZVI) on process performance to eliminate confronts for mainstream applications. An SBR (sequencing batch reactor) system was fed with various nZVI concentrations (0.04-5000 ppb) within 310 days of operation. Ammonium (NH4+N) and nitrite (NO2-N) removal rates showed 58% increase in daily measurements and 73% increase in instant measurements. Specific Anammox Activity (SAA) was noticeably higher on the days the system was exposed to nZVI compared to the unexposed days. EPS secretion, which enhances granulation of Anammox bacteria was favored by nZVI. Despite lower sludge retention time (SRT) values, the fraction of Anammox bacteria in total bacteria reached to 91-92% implying a boosting effect of nZVI on growth rate of Anammox bacteria. High Resolution Melting (HRM) analyses showed that four distinct clades were present in the reactor. (C) 2018 Elsevier By. All rights reserved

Engineered Iron Nanoparticles via Green Routes and Their Applications for Textile Wastewater Treatment

Textile wastewaters are characterized by high chemical oxygen demand (COD) concentration, strong color, high pH and temperature, and low biodegradability. Conventional treatment methods are considered to be inefficient to comply with the discharge limits. Recently, nano zero-valent iron (nZVI) technology has received increasing attention of the scientific community as an emerging technology for treatment of polluted streams. Due to smaller particle size, larger surface area and higher surface reactivity of iron nanoparticles, the removal of pollutants occur very rapidly. In this work, we synthesized nZVI employing green chemistry principles in a chemical reduction reaction. Iron precursor solution (FeSO4) was reduced by plant extracts that contain polyphenols. Plant polyphenols are known to possess strong reducing agent properties and act as effective metal chelators. The objective of this study was to characterize the green synthesized iron nanoparticles in terms of size and zeta potential parameters under various synthesis conditions (pH, precursor concentration and precursor/extract volume ratio) and compare the reactivity of the engineered nanoparticles for textile wastewater treatment. Green tea leaves-GT and Rose leaves-R were selected as the plant sources. Plant extracts were examined in terms of their Total Phenolic Content (TPC) expressed as Gallic Acid Equivalent (GAE). Rose leaves were found to possess 2062 mg/L TPC whereas, Green Tea leaves were found to have 1882 mg/L in grinded powder form. Results showed that 74% color removal along with 18% TOC removal could be achieved with 5 ppm of GT-ZVI nanoparticles synthesized at a 2/1 ratio (v/v) of precursor to extract. With the same concentration of R-ZVI nanoparticles, 78% color removal and 40% of TOC removal were observed

Occurrence of THM and NDMA precursors in a watershed: Effect of seasons and anthropogenic pollution

In pristine watersheds, natural organic matter is the main source of disinfection by-product (DBP) precursors. However, the presence of point or non-point pollution sources in watersheds may lead to increased levels of DBP precursors which in turn form DBPs in the drinking water treatment plant upon chlorination or chloramination. In this study, water samples were collected from a lake used to obtain drinking water for Istanbul as well as its tributaries to investigate the presence of the precursors of two disinfection by-products, trihalomethanes (THM) and N-nitrosodimethylamine (NDMA). In addition, the effect of seasons and the possible relationships between these precursors and water quality parameters were evaluated. The concentrations of THM and NDMA precursors measured as total THM formation potential (TTHMFP) and NDMA formation potential (NDMAFP) ranged between 126 and 1523 mu g/L THM and <2 and 1648 ng/L NDMA, respectively. Such wide ranges imply that some of the tributaries are affected by anthropogenic pollution sources, which is also supported by high DOC, Cl- and NH3 concentrations. No significant correlation was found between the water quality parameters and DBP formation potential, except for a weak correlation between NDMAFP and DOC concentrations. The effect of the sampling location was more pronounced than the seasonal variation due to anthropogenic pollution in some tributaries and no significant correlation was obtained between the seasons and water quality parameters. (C) 2012 Elsevier B.V. All rights reserved