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Breakthrough column studies for removal of iron ii from groundwater using

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  • 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 289 BREAKTHROUGH COLUMN STUDIES FOR REMOVAL OF IRON (II) FROM GROUNDWATER USING WOODEN CHARCOAL AND SAND Ahmed Hasan Nury1 , Syed Mustakim Ali Shah2* 1 (Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet-3100, Bangladesh) 2 (Department of Civil Engineering, Leading University, Sylhet-3100, Bangladesh) ABSTRACT Groundwater is an attractive and easily accessible resource of water in Bangladesh. All rural water supplies and most of urban water supplies rely on groundwater for potable supplies. Though groundwater is much less prone to bacterial contamination but in many parts of country has a severe problem with metal contamination particularly higher concentration of iron. Many iron removal units are available but most of these methods are not feasible in the rural and semi-urban areas. As a part of low cost iron removal strategy, this study used processed wooden charcoal (PWC) and processed sand (PS) as filter media and evaluates adsorptive capacity of them for dissolved iron removal through continuous mode column studies. The experiments were carried out using synthetic water containing Fe (II) at a fixed pH of 5.5 and zero dissolved oxygen levels. Different bed depth used to obtain the adsorption breakthrough curves. An increase of breakthrough time and adsorption bed capacity were found with the increase in bed depths, while breakthrough time and uptake of Fe (II) ions onto the adsorbent decreases when the linear flow rate through the bed increases. At different bed depths, PWC shows higher adsorption capacity for Fe (II) as compared to PS. Breakthrough profiles of up-scaled columns and indigenous unit models indicate that for same bed heights and flow rate, the up-scaled columns perform better than indigenous unit models and yield higher breakthrough throughputs. In the meanwhile, the up-scaled columns also performed reasonably well to remove fluoride, turbidity, sulfate and alkalinity at breakthrough point of Fe (II). Keywords: Adsorption, Ground water, Iron removal, Low cost approach, Water treatment 1. INTRODUCTION The effective development of quality water and sustenance is one major way of securing the food security and good health of the populace. Water is essential for growing food, household uses, industrial processes and the sustenance of natural cycles (Rosegrant et al. 2002). In Bangladesh, all INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), pp. 289-303 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET © IAEME
  • 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 290 rural water supplies and most of urban water supplies are ground water based. In addition, groundwater resources are also being utilized excessively for irrigation and industrial purposes (Jahan H. and Ahmed M. F, 2010). According to the United Nations Environment Programme (UNEP) Report 2002, water stress or scarcity will affect more than 2.8 billion people in 48 countries by 2025. This water scarcity affects many developing and emerging countries so that appropriate technologies are needed for purification of groundwater to enable safe use (UNEP, 2002). Several contaminants including heavy metal ions, pesticide residues, phthalate esters, polychlorobiphenyls, micro-organisms etc are capable of compromising the positive applications of water. Removal of various metals from water has been subjected to severe studies in the recent years. However, most of such studies fail to provide a cost effective method (Igwe et al., 2008; Gharbani, 2008; Goyal et al., 2008; Shah et al., 2009; Zvinowanda et al., 2009; Labidi, 2008; Lori et al., 2008; Murugesan et al., 2008; Nabi Bidhendi et al., 2007; Rahmani et al., 2009; Sahmoune et al., 2009; Salim and Munekage, 2009; Shetty and Rajkumar, 2009; Singanan et al., 2008). Iron removal from groundwater has been a subject of intensive research for the last couple of decades in developing countries like Sri Lanka, Ghana, Burkina Faso, Argentina, South Africa, Uganda and India (Ahamad, 2005; Andersson and Johansson, 2002; Chibi, 1995). Aeration and separation is the most widely used method for removal of iron from groundwater in public water supply systems, which is however, not so popular amongst rural and semi-urban communities lacking piped water supply. Other methods available for iron removal from groundwater are ion- exchange (Vaaramaa and Lehto, 2003), oxidation with oxidizing agents such as chlorine and potassium permanganate (Ellis et al., 2000; Varner et al., 1996), adsorption on activated carbon and other adsorbents (Munter et al., 2005; Berbenni et al., 2000; Ewa et al., 2007; Oztas et al., 2008; Prasenjit et al., 2007) and treatment with limestone (Aziz et al., 2004). But most of these methods and configurations of iron removal units are not feasible in the rural and semi-urban areas either at community levels or at an individual household level due to high capital costs and complicated operation and maintenance requirements of these methods and units. Therefore, efforts have to be directed to look for such techniques for iron removal from the groundwater which is acceptable and easily adaptable to communities especially for rural and semi-urban area lacking piped water supply, so as to ensure acceptable quality potable water on a sustainable basis at an affordable cost. Iron is a common household contaminant in Bangladesh. It is predominantly an aesthetic concern because iron precipitates as insoluble ferric hydroxide at higher pH and settles as red colored silt. It is visible on staining, enameled surfaces such as baths, hand basins, etc. It also gives an offensive taste and odor to water (Reddy and Chakraborty, 2009). The quantity of iron in the groundwater of Bangladesh is more than the WHO’s limit (0.3 mg/L). A field survey was carried out in Moulvibazar district of Bangladesh, where the groundwater contains 1-10 mg/L or more of iron. However, the population in the iron contaminated areas has black colored teeth (WHO, 2004). Other health effects include: acute poisoning in infants and chronic iron poisoning, haemochromatosis. So it is a matter of concern now to ensure low cost methods/ techniques for iron removal from the groundwater in this region. Adsorption is widely accepted as low-cost water treatment applications throughout the world. Present study used community prepared brick chips (CPBC) and river sand (RS) as filter media since wooden charcoal and river sand are easily available, eco-friendly and easy to prepare in Bangladesh. The objective of this study is to develop the knowledge of low cost treatment technology for producing potable water as well as ensuring sustainable availability of safe and hygienic drinking water at individual household levels to both rural and urban areas of country. As a part of low cost iron removal approach, present work estimates Fe (II) uptake capacity of the wooden charcoal and sand through continuous mode column studies to find out the influences of bed depth, linear flow rate and concentration of inlet Fe (II) on the performance of Fe (II) adsorption onto adsorbent media.
  • 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 291 2. MATERIALS & METHOD The community prepared wooden charcoal (CPWC) was collected from a local market called ‘Madina Market’, located about 2 km away from Leading University campus on the north bank of Surma River in Sylhet. River sand (RS), the second filter media is a local construction material was procured from Shahjalal University’s Engineering Materials laboratory, which was mined from the river-beds of Sari Ghat, about 50 km away from Sylhet City. Collected CPWC samples having individual pieces of 2 cm × 1.5 cm × 1.5 cm to 4 cm × 2.5 cm × 1.5 cm in size range were processed into smaller sizes, washed with distilled water and dried at 105°C in a drying oven at Leading University laboratory. Sieve analysis was performed using dried wooden charcoal as per IS 2720 (1975). Particles passing through 450 µm sieve openings but retaining over 300 µm sieve openings were selected as study material which were termed as processed wooden charcoal (PWC). The collected RS contains many foreign materials like floating debris, dirt, clay etc since they are available natural construction material. Sample sand was washed until all foreign materials removed and then dried at 105° C in the drying oven. Sieve analysis was also carried out for river sand as per IS 2720 (1975) and particles passing through 300 µm sieve openings but retaining over 150 µm sieve openings were selected for this study which were termed as processed sand (PS). The scanning electron microscopy of PWC indicated presence of numerous pores while that of PS indicated absence of pores (Ahamad and Jawed, 2008). However, the properties of PWC and PS are presented in Table 1. Table1. Properties of processed wooden charcoal (PWC) and processed sand (PS) Properties PWC PS Particle size range 425 µm – 300 µm 300 µm – 150 µm Bulk density 290 kg/m3 1523 kg/m3 Moisture content 10% 0.5% Ash/Inert content 8% 94% Generally, the dissolved ferrous iron [Fe (II)] turned into insoluble ferric hydroxide [Fe (III)] at higher pH and settles as red colored silt. Therefore, experiment was organized to assess the solubility of Fe (II) in pH range of 2 to 12. To prepare a Fe (II) stock solution of 200 mg/mL ferrous sulfate (FeSO4.7H2O) was used. Required amount of stock solution was taken in a 100 mL specimen tube and pH was adjusted by mixing appropriate acid (0.2N HNO3) or lime (Rao and Rekha, 2004). A digital pH meter was used to check solution’s pH accuracy. The final volume was
  • 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 292 made up to 100 mL with distilled water to give a final Fe (II) concentration of 5 mg/L. Whole specimen tubes were shacked manually (5-8 min) for proper mixing, with (»40-50 rpm). Phenanthrolinthe method was used to estimate remaining Fe (II) concentration in the solution (APHA, 1998). Later the solubility of Fe (II) in the presence of DO was assessed at room temperature (24±1°C) via separate experiment. A plastic bucket with 10–12 L of distilled water was taken and 0.2N HNO3 was used to fix a pH value at 5.5 in the presence of DO. Initial DO level was estimated as per Standard Methods (APHA, 1998) and then brought down to zero by adding slightly more than the stoichiometric requirement of sodium sulfite (Na2SO3). The liquid volume was made up to 15L by adding required amount of Fe (II) stock solution to achieve an initial Fe (II) concentration of 6.5 mg/L. A normal air pump was used to ensure aeration. A Buffer system was developed using acetic acid and sodium acetate (1 mL of 0.2M acetic acid and 9 mL of 0.2M sodium acetate mixed to give 10 mL of buffer solution) (Jeffery, 1996) to monitor pH fluctuation. Samples were drawn at regular intervals for estimation of Fe (II) and DO. A glass column having 38 mm internal diameter was used for this experiment as shown in Fig. 1. The column was filled up to a desired depth with adsorbing media (PWC or PS), mounted up and kept submerged throughout the runs to avoid air entrapment in the beds. A multi-channel peristaltic pump was used at two different flow rates of 2 and 3 mL/min to ensure continuous down flow through the column. The column studies were carried out at the room temperature (29±1°C) with Fe (II) concentration of 6.5 mg/L at a fixed pH of 5.5 and zero dissolved oxygen (DO). Samples from the column were collected at regular intervals till the bed exhausted or yielded effluent with 90% of initial Fe (II) concentration. To compare the performance of up scaled columns fabricated using PWC and PS with the models of indigenous units using PWC and RS, a PVC tubes of 10 cm internal diameter were used with different bed combinations. This study considered two combinations of layered bed for the up- scaled columns: (i)10 cm bed depth of PWC on top and 10 cm bed depth of PS at bottom, and (ii)10 cm bed depth of PS on top and 10 cm bed depth of PWC at bottom. Similarly, two combinations of layered bed were selected for the models of indigenous units: (i) 10 cm bed depth of CPWC on top and 10 cm bed depth of RS at bottom, and (ii) 10 cm bed depth of RS on top and 10 cm bed depth of CPWC at bottom. Total bed depth for up-scaled column and indigenous units became 20 cm where the overall height of the PVC tube used for fabrication was restricted to 30 cm. The selection of bed depth was dictated by the height of PVC tube. Whole experimental system including up-scaled columns and models of indigenous units were operated in parallel at a flow rate of 11.53 mL/min (16.6 L/d) in down flow mode with initial Fe (II) concentration of 6.5 mg/L. The solution pH was adjusted to 5.5 and DO level made to zero. The up-scaled columns were also operated with actual ground water at a flow rate of 6 mL/min using selected two different bed arrangements. Mass balance of the packed- bed reactor is carried out and its variation during the reaction could be illustrated by Fig. 1. The equation of mass balance material is: input flow = output flow + flow inside pores volume + matter adsorbed onto adsorbent material. For this system, the balance could be expressed according to the following equation, QvC0 = QvC+Vp ௗ஼ ௗ௧ ൅ ݉ ௗ௤ ௗ௧ ……………………………………….(1) Where Qv is the volumetric flow of the solution in the column (L/min), C0 and C respectively the inlet and outlet solute concentrations (mg/L), QvC0 the inlet flow of solute in the column (mg/min), QvC the outlet flow of solute leaving the column (mg/min), Vp the pore volume (Vp = ଵ ଵିԪ Va ; where Va is the bulk volume and ε the porosity), Vp ୢେ ୢ୲ the flow rate through the column bed depth
  • 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 293 (mg/min) and m ୢ୯ ୢ୲ the amount of solute adsorbed onto column media (mg/min) where m is the mass of adsorbent material and ୢ୯ ୢ୲ the adsorption rate. According to Eq. (1), the determining factors of the balance for a given bed depth of the column are the linear flow rate (u = ୕୴ ୗୡ , where Sc is the column section, m2 ), the initial solute concentration, the adsorption potential and the pore volume even if previous studies (Costodes et al., 2005) showed that the latter parameter may be neglected. Therefore, in order to optimize the adsorption process in a packed bed column, it is necessary to examine these parameters and to estimate their influence. Fig.1. Schema of packed-bed reactor (Where u is the linear flow rate and also the average rate of the liquid flow when the column is empty) The breakthrough curve represents the evolution of the solution concentration in function of adsorption parameters like adsorbent depth, contact time between liquid and solid phase, solvent concentration and so on. A typical breakthrough profile of a column study is shown in Fig. 2. Normally the top portion of adsorbent layer adsorbs pollutant more quickly during its first contact with the fluid. Thus at early time the fluid leaving the column is partially free from pollutants then other times (points P1, P2 and P3 in Fig. 2.). As the polluted water flow through column bed increases, adsorption zone gradually decreases called zone of mass transfer (MTZ). In this MTZ, adsorption is complete and the concentration of pollutant in the bed column varies from 100% of Co (corresponding to total saturation) to approximately 0% of Co (corresponding to the virgin adsorbent). Additionally, the height of mass transfer zones ‫ܪ‬ெ்௓ was estimated using the relation (Tchobanoglous et al., 2003). ‫ܪ‬ெ்௓ ൌ ௏ಶି௏ಳ ௏ಶି଴.ହሺ ௏ಶି௏ಳሻ …………………………………….. (2) Where Z = height of the adsorption column, ܸ஻= throughput volume to breakthrough and ܸா= throughput volume to exhaustion.
  • 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 294 Fig. 2. Typical breakthrough profiles from a column study (Source: Tchobanoglous et al., 2003) As the filtering period increases the adsorption zone moves downwards through the bed column until the breakthrough occurs. When this zone reaches the bottom of the bed the pollutant dissolved in the solution could not be adsorbed any longer. This moment is called “breakpoint”. The plot obtained after this point gives the concentration history and is called breakthrough profile or breakthrough curve. Practically, breakthrough point determines the solute concentration in the effluent and also expresses the treated volume known as throughput volume (VB). For most adsorbent–pollutant systems, the breakthrough curve is obtained after an effluent concentration of 50% has been reached. To facilitate the calculations of the bed adsorption capacity, the breakthrough curve is often fixed at 50% (P4, Fig. 2), sometimes at 10% (P3, Fig.2) of the inlet concentration according to the target quality of the final effluent (Tchobanologus et al., 2003). When MTZ reaches to the column bottom (P5, Fig. 2), the adsorption bed became completely saturated. In this condition adsorption in the bed does not occur and the effluent which leaves the column has the same concentration as the one that enters. The quantity of adsorbed pollutant at breakpoint (qB in mg/g) could be estimated for a single column from the following relation suggested by Tchobanologus et al. (2003) with known breakthrough time (tB) using: ‫ݍ‬஻ ൌ ቀ ௫ ௠ ቁ ஻ ൌ ቀ ௫ಳ ௠ೌ೏ೞ೚ೝ್೐೙೟ ቁ ൌ ܳ௏ ቀ‫ܥ‬଴ െ ஼ಳ ଶ ቁ ௧ಳ ௠ೌ೏ೞ೚ೝ್೐೙೟ ……………… (3) Where ቀ ௫ ௠ ቁ = breakthrough adsorption capacity (mg/g), xB = mass of adsorbate adsorbed in the column at breakthrough (mg), madsorbent = mass of adsorbent in the column (g), Qv = flow rate (mL/min), Co = influent adsorbate concentration (mg/L), CB = breakthrough adsorbate concentration (mg/L) and tB = time to breakthrough (min). The important assumptions associated with the development of Eq. (3) were: Co taken as constant and that the effluent concentration increased linearly with time from 0 to CB. The term ቀ‫ܥ‬଴ െ ஼ಳ ଶ ቁ represented the average concentration of the adsorbed up to the Breakthrough point.
  • 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 295 3. RESULT & DISCUSSION The variation in Fe (II) remaining in solution with pH and DO levels is presented in Fig. 3(a) and 3(b) respectively. Iron remained in soluble form at pH < 6, but at pH > 7 almost all iron turned into insoluble form shown by Fig. 1(a). Fig. 3. Variation in Fe (II) solubility with (a) pH and (b) DO level at fixed pH 5.5. [Initial Fe (II) conc. = 6.5 mg/L, Temp = 29±1 o C] The effect of DO levels on the solubility of Fe (II) observed at DO levels > 1 mg/L. When the DO level reached a steady value of 6.8 mg/L, the Fe (II) decreased to the lowest level. Therefore, further experiments were carried out at a fixed pH of 5.5 with zero DO levels to ensure availability of iron in Fe (II) form. A breakthrough curves was plotted by the concentration ratio of Ct/Co versus throughput volume to represent Fe (II) adsorption onto PWC and PS. Two different bed depth of PWC and PS; 15 and 20 cm, at a constant linear flow rate of 2 mL/min were considered to obtain breakthrough curves which are illustrated in Fig.4 while a summary of results are presented in Table 2. 0 1 2 3 4 5 0 2 4 6 8 10 12 Fe(II)conc.(mg/L) pH Series1 Series2 (a) 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 120 Fe(II)conc.(mg/L) Time (min) (b) 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 120 DO(mg/L) Time (min) (b)
  • 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 296 Fig. 4. Effect of bed depth on the breakthrough curves for Fe(II) adsorption through columns of (a) PWC alone and (b) PS alone [Qv= 2 mL/min; Co =6.5 mg/L] PWC and PS were used separately as column beds for different depth to produce an ideal adsorption system. Resulting breakthrough curves shows “S” shaped profile. Mass transfer phenomena that take place in this process could be used to explain the displacement of the front of adsorption with the increase in depth. When the bed depth is reduced, axial dispersion phenomena predominate in the mass transfer and reduce the diffusion of metallic ion and hence solute [Fe (II) ion] has no enough time to diffuse into the adsorbent mass. Therefore, the volume of solution at the breakthrough point reduced considerably when the bed depth in the column decreases from 20 to 15 cm represented by Fig. 4 and Table 2. In addition, adsorbent mass increases with bed depth while an increase in the bed adsorption capacity (qB) is also noticed at the breakthrough point [Table 2]. Table 2. Summary of breakthrough results for Fe (II) adsorption on columns of different bed depths Column Bed Bed Depth (cm) Adsorbent Mass (g) Throughput Vol. VB (mL)a Breakthrough time tB (min)a HMTZb (cm) Adsorption bed capacity qB (mg/g)c PWC alone 15 0.853 128 65 16.7 0.789 20 1.392 215 80 21.9 1.432 PS alone 15 11.004 230 95 15.78 0.278 20 17.645 450 198 22.18 0.457 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 Ct/Co Throughput Volume (mL) Bed Depth 15 cm (a) 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 Ct/Co Throughput Volume (mL) Bed Depth 20 cm (a) 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Bed Depth 15 cm (b) 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Bed Depth 20 cm (b)
  • 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 297 Fig. 5. Effect of variation in linear flow rates for breakthrough curves of Fe(II) adsorption through column of (a) PWC alone and (b) void space of PWC filled with PS [Z = 10 cm; Co = 6.5 mg/L, mc(PWC) = 4.65 g] It may occur be due to the increase in the specific surface of the adsorbent which supplies more fixation binding sites. The breakthrough time also increases with the height of the bed. Therefore, as the breakthrough point delayed the adsorbent get more time to adsorb pollutants. So the larger breakthrough time, the better are the intra particulate diffusion phenomena and the bed adsorption capacity. The initial solute concentration and bed depth were kept constant (Co = 6.5 mg/L, Z = 15 cm) with a linear flow rate 2 mL/min to examine the effect of linear flow rate through the column beds. The resulting breakthrough curves are presented in Fig. 5 while results are summarized in Table 3. The linear flow rate of solution through the filter bed has an effect on all breakthrough parameters. Throughput volume reduces until breakthrough point as the flow rate changes from 2 to 3 while height of mass transfer zone increases. This is due to the decrease in contact time between Fe (II) ions and the adsorbent at higher linear flow rates. A reduction in bed adsorbent capacity also found from breakthrough profile. It is occurred due to the contact time between Fe (II) ions and adsorbents. At low flow rate Fe (II) get more time to diffuse amidst the particles of adsorbent. At a higher linear flow rate, the adsorbent gets saturated early because of a reduced contact time which leads to a lower diffusivity of the Fe (II) amidst the particles of the adsorbent Cost odes et al. (2005). The effect of variation in inlet Fe (II) concentrations of 6.5 and 10 mg/L was tested with a linear flow rate of 2 mL/min using bed depth of 15 and 20 cm for PWC and PS respectively. The breakthrough 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Q=2 (mL/min) PWC 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Q=3 (mL/min) PWC 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Q=2 (mL/min) PWC with PS 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Q=3(mL/min) PWC with PS
  • 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 298 profiles are presented in Figure 6 while a summary is given in Table 3. A rise in inlet Fe (II) concentration yields reduced throughput volume before the packed bed got saturated. An increase in inlet metal concentration develops extra pressure on adsorbent media which results quick saturation of filter bed, thereby decreasing the breakthrough time. Adsorption capacity also reduced by increase metal concentration as illustrated in Table. The saturation of the adsorbent required much more time and the breakthrough was reached before all the active sites of the adsorbent were occupied by the metal ions. The PWC column showed higher affinity for Fe (II) as compared to PS column under the experimental conditions of this study. The breakthrough profiles obtained through upscale columns as well as models of indigenous unit are presented in Fig.7 while results are summarized in Table 5. Table 3: Summary of breakthrough results for Fe (II) adsorption with variation in linear flow rates Column Bed Flow rate Qv (mL/min) Throughput Vol. VB (mL)a Breakthrough time tB (min)a HMTZb (cm) Adsorption bed capacity qB (mg/g)c PWC 2 128 52 16.70 0.789 3 100 45 17.32 0.734 PWC (Voids filled 2 250 75 17.87 0.678 3 185 56 18.24 0.483 Fig. 6. Effect of variation in inlet Fe (II) concentration on breakthrough curves through column of PWC and PS [ZPWC = 10 cm, ZPS = 10 cm, mc(PWC) = 4.65 g, mc(PS) =32.8 g, Qv = 2 mL/min] 0 0.2 0.4 0.6 0.8 1 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Inlet Fe (II) conc. 6.5 mg/L PWC 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Inlet Fe (II) conc. 10 mg/L PWC 0 0.2 0.4 0.6 0.8 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Inlet Fe (II) conc. 6.5 mg/L PS 0 0.2 0.4 0.6 0.8 0 400 800 1200 1600 2000 Ct/Co Throughput Volume (mL) Inlet Fe (II) conc. 10 mg/L PS
  • 11. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 299 Fig. 7. Comparison of breakthrough profiles of up-scaled columns and indigenous unit models [Co = 6.5 mg/L, Temp = 24±1 oC, mPWC = mCPWC = 14.1 g and mPS = mRS = 205 g] Fig. 8. Breakthrough profile of up-scaled columns obtained with actual groundwater samples [Co = 6.5 mg/L, Temp = 24±1 o C, mPWC = 14.1 g, mPS = 205 g] 0 0.1 0.2 0.3 0.4 0.5 0 10 20 30 40 50 60 70 80 Ct/Co Throughput Volume (mL) Up-Scaled:PWC at top & PS at bottom 0 0.1 0.2 0.3 0.4 0.5 0 10 20 30 40 50 60 70 80 Ct/Co Throughput Volume (mL) Indigenous:CPWC at top & RS at bottom 0 0.1 0.2 0.3 0.4 0.5 0 10 20 30 40 50 60 70 80 Ct/Co Throughput Volume (mL) Up-Scaled: PS at top & PWC at bottom 0 0.1 0.2 0.3 0.4 0.5 0 10 20 30 40 50 60 70 80 Ct/Co Throughput Volume (mL) Indigenous:RS at top & CPWC at bottom 0 0.1 0.2 0.3 0.4 0.5 0.6 0 10 20 30 40 50 Ct/Co Throughput Volume (mL) PWC at top & PS at bottom 0 0.1 0.2 0.3 0.4 0.5 0.6 0 10 20 30 40 50 Ct/Co Throughput Volume (mL) PS at top & PWC at bottom
  • 12. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 300 Table 4: Summary of breakthrough results for Fe (II) adsorption through PWC and PS beds with variation in inlet metal concentrations Column Bed Inlet Conc. Co (mg/L) Throughput Vol. VB (mL)a Breakthrough point tB (min)a Adsorption bed capacity qB (mg/g)b PWC 6.5 650 126 0.948 10 430 78 0.764 PS 6.5 720 138 0.267 10 400 86 0.176 a Obtained from Figure 6; b Calculated using Eq. (3) Table 5: Performance summary of up-scaled columns and indigenous unit models Column/Unit Bed arrangement Fe (II) conc. (mg/L) Throughput Vol. VB (L)a Breakthrough time, tB (min)a Up-scaled PWC at top & PS at bottom 6.5 13 1535 PS at top & PWC at bottom 8 1348 Indigenous CPWC at top & RS at bottom 6.5 9 978 RS at top & CPWC at bottom 6 856 a Obtained from Fig. 7. Table 6: Performance summary of up-scaled columns with actual groundwater Bed Arrangement Throughput volume, VB (L) PWC at top & PS at bottom 8.5 PS at top & PWC at bottom 7.6 It is apparent from the results that the up- scaled columns yielded higher volume of throughput as well as enhanced service time at the breakpoint compared to models of indigenous units indicating possibility of enhancing the performance of indigenous household iron filter units by selecting the filter media of appropriate size ranges. Table 7: Performance of up-scaled column in terms of other water quality parameters with actual groundwater Water Quality Parameters Groundwater Sample Treated by up-scaled columns with # PWC at top & PS at bottom PS at top & PWC at bottom Fe(II) (mg/L) 8.20 0.257 0.257 Fluoride (mg/L) 0.58 0 0 pH 6.20 6.89 7.10 Turbidity (NTU) 22.00 0.4 0.95 Sulfate (mg/L) 8.00 1.285 1.30 Nitrate-N (mg/L) 2.7 2.7 2.7 Nitrite-N (mg/L) 0 0 0 Ammonia-N (mg/L) 0.21 0.115 0.098 Hardness (mg/L as CaCO3 ) 240 240 215 Calcium (mg/L) 56.25 56.10 54.25 Potassium (mg/L) 2.43 2.43 2.43 Alkalinity (mg/L as CaCO3) 290 109 115 # monitored after breakthrough with Fe (II)
  • 13. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 301 Groundwater samples containing various other ionic species in addition to Fe (II) were taken to evaluate the performance of up-scaled columns. The breakthrough profiles are presented in Figure 8, while the summary of breakthrough throughput is presented in Table 6. It was evident that up- scaled columns were able to perform effectively with actual groundwater also and yield appeared to be reasonable and comparable in both the bed arrangements In addition to monitoring the performance for Fe (II) removal and the breakthrough profiles, the performance of up-scaled columns were also monitored for other water quality parameters at the breakthrough, which is presented in Table 7. The up-scaled columns were able to remove fluoride, turbidity, sulfate as well as alkalinity along with Fe (II). 4. CONCLUSION The solubility of Fe (II) was significantly affected by the pH and DO levels particularly when pH>7. In addition, the dissolved ferrous iron [Fe (II)] turned into insoluble ferric hydroxide [Fe (III)] at higher pH and settles as red colored silt (precipitate). Obtained breakthrough profiles for different bed depths shows that the volume of solution at the breakthrough point reduced considerably when the bed depth in the column decreases. Besides, an increase in adsorbent mass and bed adsorption capacity also noticed at the breakthrough point. A reduction of throughput volume was found until breakthrough point due to the change of linear flow rate from lower to higher. The effect of variation in inlet Fe (II) concentrations was also observed from breakthrough profile. A rise in inlet Fe (II) concentration yields reduced throughput volume before the packed bed got saturated. Comparison of breakthrough profiles of up-scaled columns and indigenous unit models found higher affinity of PWC for Fe (II) as compared to PS. Besides, the up-scaled columns yield higher volumes of throughput compared to models of indigenous units. However, the up-scaled columns perform reasonably well with actual ground water containing various other ionic species and indicate its ability to remove fluoride, turbidity, sulfate and alkalinity at breakthrough point of Fe (II). REFERENCES 1. Rosegrant M.W., Cai X. and Cline S.A. (2002) “World Water and Food to 2025: Dealing with Scarcity”, IFPRI Brief, International Food Policy Research Institute, Washington, DC, U.S.A. 2. Jahan H. and Ahmed M. F., Participatory management of low-cost water supply and sanitation (ITN-BUET, Centre for Water Supply and Waste Management, Dhaka, 2010). 3. UNEP (2002), “Vital Water Graphics, Freshwater Stress”, available at http://www.unep.org/dewa/assessments/ecosystems/water/vitalwater21.htm#21b. Accessed on January 23, 2009. 4. Igwe J. C., Abia A. A. and Ibeh C. A., Adsorption kinetics and intra particulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber, International Journal of Environmental Science Technology, 5 (1), 2008, 83-92. 5. Gharbani P., Tabatabaii S. M. and Mehrizad A., Removal of Congo red from textile wastewater by ozonation. International Journal of Environmental Science Technology, 5 (4), 2008, 495-500. 6. Goyal P., Sharma A., Srivastava S., and Srivastava M. M., Saraca indica leaf powder for decontamination of Pb: removal, recovery, adsorbent characterization and equilibrium modeling, International Journal of Environmental Science Technology, 5 (1), 2008, 27-34. 7. Shah B. A., Shah A. V. and Singh R. R., Sorption isotherms and kinetics of chromium uptake from wastewater using natural sorbent material, International Journal of Environmental Science Technology, 6 (1), 2009, 77-90.
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