Dissertations/Theses - Department of Civil Engineering
Browse
13 results
Search Results
Item Effectiveness of multistage filtration in removing iron, manganese and arsenic from groundwater of Bangladesh(Department of Civil Engineering (CE), 2009-10) Matiar Rahman Mondol, Md.; Ahmed, Dr. FarooqueThe presence of iron, manganese and arsenic in ground water beyond the permissible limit is now considered to be a major problem throughout the world and produce numerous adverse effects. These problems are severe in the context of Bangladesh as groundwater is a vital source for the safe drinking water supply. In the present study seven numbers of multistage filtration units (MSFU) have been constructed in Sirajgonj,Comilla and Jessore ( three different hydro-geological conditions) to investigate the effectiveness of multistage filtration in removing iron, manganese and arsenic from groundwater of Bangladesh adopting the technique of adsorption and co-precipitation of arsenic and manganese onto the flocs of ferric hydroxide, making use of the naturally occurring iron of groundwater. The MSFU, which is attached to a tube well, has three chambers, 1st chamber (Aerator plus Down-flow Flocculator), 2nd chamber (Sedimentation plus Up-flow Roughing Filter) and 3rd chamber (Down-flow Roughing Filter) .The flocculation and roughing filtration processes in the MSFU were accomplished through the use of brick chips. The MSFU is connected to the spout of tube well with a short piece of 75 mm PVC / flexible pipe. Water entering the first chamber is distributed uniformly over the whole bed of course media through a porous thin ferro-cement plate placed on the top, resulting strip out of CO2 and increase of pH value for the oxidation of soluble iron. In the Down-flow Flocculator oxidation and subsequent precipitation of iron oxy-hydroxides occurs respectively on the top and within the interstices of coarse media which adsorbs arsenic oxy-anions as well as manganese ions. Sinusoidal flow across the coarse media enhance collisions for the flocculation of precipitated particles. Comparatively larger flocculated precipitates settle at the bottom of the sedimentation chamber. Significant removal of precipitated particles occurs by sorption on to iron oxy hydroxides and mechanical straining during up-flow through the comparatively finer coarse media bed in the 2nd chamber. Final removal of precipitated particles occurs through sorption on to iron oxy hydroxides and mechanical straining during down-flow through the comparatively finer coarse media bed in the 3rd chamber. Water samples collected weekly from different location of the Multi-Stage Filtration Units (MSFU) were tested in the laboratory for determining the concentration of iron, arsenic and manganese. Around 97 % of iron reduction was achieved through the MSFU. Arsenic removal efficiency upto 91 % was achieved through the MSFU without using any chemicals. Two different equations have been developed to express the effect of tube well water iron concentration on iron and arsenic removal performance respectively. Using these equations it will be easy to determine the residual iron concentration in the final effluent achieved through properly designed MSFU treating tube well water of different initial iron concentration. Manganese removal was observed as a function of raw water manganese concentration. Higher the manganese concentration, greater was the removal performance. Up to 85 % manganese removal performance was achieved through the MSFU. Contribution of DRF alone in removing manganese was observed very significant (around 37%). For tube well water having manganese concentration around 1.5 mg/l and iron concentration around 15 mg/l, a residual Mn concentration below maximum permissible limit (WHO health risk guide line value for Mn) of 0.4 mg/L could be maintained through the MSFU. Performances of Iron Chips Column (filled with iron chips and iron coated sand.) attachment with the MSFU were also monitored and necessary modifications in the design have been recommended. Operation and maintenance procedure (cleaning) were determined .The initial effluent flow from the URF were around 85 % of tube well water flow. Length of filter run between cleaning should be maximum 3 - 4 weeks. MSFU will be cleaned when flow from the outlet of URF chamber will reduce by 45-50% of the tube well flow i.e. flow from the URF chamber = 9-10 L/min. Numbers of users and water consumption was increased by about 10 folds after the installation of the MSFU.Item Arsenic adsorption characteristics of magnetite nanoparticles(Department of Civil Engineering (CE), 2009-04) Roy, Preetom Kishore; Ali, Dr. Muhammad AshrafItem Contamination of dugwell water and its control(Department of Civil Engineering (CE), 2005-08) Nehreen MajedWater quality studies conducted so far have shown that dug wells have reduced arsenic ingestion but exposed population to high levels of health risk from microbial contamination. This study aims at understanding the nature of contamination of dugwell water and decontamination by in-situ chemical disinfection. For preliminary water quality analysis, dugwells were selected from Sirajdikhan, Singair, Daudkandi and Sharsha upazilas. After preliminary water quality analysis, two dugwells with high microbial contamination from Sirajdikhan and one dugwell with high arsenic content from Sharsha were selected for decontamination study. Natural growth/decay of total coliform and faecal coliform was studied in the laboratory and break point chlorine dose was determined for the samples under consideration. Then, starting from the break point dose, different doses were applied to the dugwell water in the laboratory and the chlorine dose for complete removal of coli forms from the water was determined. The effect of chlorination on other water quality parameters like arsenic, ammonia, manganese, iron, turbidity, etc. was also studied in the laboratory. Chlorination was performed in each of the selected dugwells and continued for a couple of days. Water samples were collected from each of the dugwells both before and after chlorination and analyzed for selected water quality parameters on each day of chlorination. Finally, recharge capacity of 51 dugwells in Sharsha upazila was studied and user acceptability surveyed at Sirajdikhan. Rate of microbial decay in the dugwell water has been found to be significantly high (maximum of0.455/day). The negative or very low Eh (-102 mY) and low dissolved oxygen (0 mg/I) of dug well water are not favourable for oxidation of iron, arsenic and odour producing substances. Dissolved arsenic (as high as 0.14 mg/I at Sharsha), iron (as high as 10 mg/I at Daudkandi) and manganese (as high as 1.48 mg/l at Sirajdikhan) were present in dugwells. There was hardly any difference between the water quality of open and closed dug wells and the efforts made for keeping the dug wells open seemed futile. The improved dugwells produce an average of 2.09 m3/day of water in the wet season and 0.58 m3/day of water in the dry season, which are inadequate to meet the requirements. Residual chlorine in the range between 0.5 to 1 mg/I destroyed all coli forms. However, the chlorine level quickly decreased with the inflow of new groundwater in the dug well and rendered the well vulnerable to renewed contamination. Chlorine dosing increased redox potential of dug well water from soluble reducing fields to highly oxidizing fields in Eh-ph phase-stability diagrams of both Fe and As. Although, the oxidizing condition prevails in the DW, following chlorination, the As and Fe concentration increased in the collected samples which is contradictory to the theory. However, this might have happened as the Fe flocs formed due to oxidized condition settling downward being pumped directly through the uptake pipe and thus, increasing the Fe and As level in the samples. This dynamic flow condition might have caused the effects opposite to those found in theory as well as in the laboratory. In spite of some aesthetic water quality problems, dug well water appeared to be acceptable to most of the respondents at Sirajdikhan. Most of the people in the study areas had no complain about drinking chlorinated water at the levels of 0.5 - 1.0 mg/l of residual chlorine in water. But, intermittent dosing of chlorine even at an interval of once a day has been found to be ineffective in maintaining the coliform to desired level of zero.Item Quantification of arsenic release from arsenic rich wastes and soil in presence of cowdung(Department of Civil Engineering (CE), 2004-05) Azizur Rahman, Mohammad; Abdul Jalil, Dr. Md.To combat the arsenic crisis, a number of household and community based arsenic removal technologies have been developed and a number of such technologies are currently being used in many arsenic affected areas in Bangladesh. All arsenic removal units generate some form of arsenic-rich wastes. Currently, disposal of such wastes in cow-dung bed is widely practiced. It has been suggested that biochemical processes in cow-dung bed transform inorganic arsenic into volatile forms and release them into air. In this study elimination of arsenic from arsenic solution, arsenic rich wastes and soil was evaluated in the laboratory. Role of phosphate in displacing arsenic from soil was also observed. Batch experiments were done to assess the elimination of arsenic from arsenic solution (unbound arsenic), arsenic rich wastes and soil (bound arsenic) in the presence of cowdung. Different concentrations of arsenic were mixed with different weight of fresh cowdung and the elimination of arsenic was studied under both cap-open condition (for simulating aerobic condition) and cap-closed condition (for simulating anaerobic condition). Results of batch experiments performed on a\\'ide range of arsenic aqueous solution suggest that, in general, significant elimination of arsenic (III) occurred from aqueous solution in the presence of fresh cowdung. The range of elimination was 13% to 96%. Majority of this elimination appeared to take place during the first few days. The results of this study suggest that the elimination of arsenic is not proportional to the amount of cowdung added to the aqueous solutions and initial concentration of arsenic in aqueous solution. Similar results were obtained for the batch experiments with As (V) aqueous solution. With arsenic rich wastes (Steven's Technology for arsenic Removal unit and Bucket Treatment Unit), the range of elimination was 9% to 69%. The elimination of arsenic from soil was observed 2% to 25% without using cowdung whereas the range of arsenic elimination was 52% to 89% with using cowdung. This study also suggest that elimination of unbound arsenic (aqueous solution) is quite high compared to bound arsenic (arsenic in wastes and soil.) In some cases it has been found that with increasing initial arsenic concentration elimination of arsenic decrease but more study is needed to ascertain this. The possible reason for great variation in the elimination of arsenic from solutions and wastes are variability in the number and type of microorganisms present in cowdung and in the availability of nutrients. Again, it has been found that As (V) reduced to As (III) before elimination, which has been suggested in literature. The ability of phosphate in displacing arsenic from soil was also observed in laboratory. From the study it can be suggested that bio-chemical processes eliminate arsenic from arsenic rich wastes and soil in the presence of cowdung but the reaction involved, type of volatile arsine produced, characteristics of microorganism present in the cowdung should be studied in more detail for better understanding of the elimination process.Item Identification of causes of arsenic contamination in graoundwater of Bangladsh(Department of Civil Engineering (CE), 2006-09) Aktarul Islam Chowdhury, Mohammod; Ahmed, Dr. M. FerozeArsenic contamination of groundwater in shallow aquifers has become a scvere water supply and hcalth problem in many parts of Bangladesh. A national survey has idcntified 1.44 million tubewell contaminated with arsenic exceeding the Bangladesh drinking water standard of 0.05 mg/L and 38,420 cases of arsenicosis patient. In this study, groundwater, river water, suspended sediment of the river water, riverbed sediment, and floodplain sediment of three rivers (Jamuna, Padma and Meghna), and borehole sediment of alluvial plains of five arsenic affected districts of Bangladesh were collected and studied in an effort to identify sources of arsenic and mechanisms of its mobilization in the subsurface. Arsenic content in river water, suspended sediment, riverbed sediment, and floodplain sediment of three rivers - Jamuna, Padma and Meghna was analyzed. Arsenic was found in suspended sediment at concentrations comparable to average arsenic content in soils in Bangladesh, but very little arsenic was found in the river water samples. The sediments were fractionated into sand, silt and clay fractions and the arsenic content in each of the fractions was determined. Highest concentration of arsenic was found in clay fraction of the sediment, followed by silt, with lowest concentration in sand. The arsenic content of fine-grained materials like clay is higher because they have higher surface area as well as adsorption sites per unit volume/weight. The beels and haors receive higher quantity of Arsenic as the clayey materials are deposited in these stagnant water bodies. It has been found that the districts with beel and haors and low-lying areas are severely affected by Arsenic contamination of groundwater. An estimated 11,000 metric tons of arsenic is transported through Bangladesh each year from upstream with 2.4 billion tons sediment; a large fraction of this arsenic however is discharged in the Bay of Bengal with the sediment. The suspended sediment and river bed sediment may be an important source of arsenic in Bangladesh. Arsenic concentration in the floodplain sediments of three rivers - Jamuna, Padma and Meghna as well in the borehole sediments of alluvial plains of Sylhet, Chandpur, Munshiganj, Kushtia and Nawabganj were analyzed. Arsenic concentrations of these sediments have been found to be comparable to average arsenic contents in soils of Bangladesh. Arsenic present in different chemical forms in the sediment samples from floodplain and alluvial plain were analyzed by sequential extraction method. Relatively small amount of Arsenic was found to be present as ionically bound and strongly adsorbed forms. Comparatively a larger amount of Arsenic was found to be associated with amorphous iron oxyhydroxides. However, there are variations in the chemical forms of Arsenic associated with sediment, depending on the geological history of the sediment. The Arsenic present in the sediments as ionieally bound (IB), strongly adsorbed (SA), and associated with amorphous iron oxydydroxides (Ala) accounts for significant quantities of total arsenic, which could be mobilized under reducing condition. Arsenic and other relevant water quality parameters of groundwater samples were determined. Arsenic concentration was found to be positively correlated with ammonia, alkalinity and hardness of groundwater. This relationships support the process of Arsenic mobilization with the microbial breakdown of organic mailers in the sub-soil environment. Arsenic was also found to be inversely correlated with oxidation-reduction potential (ORP) of groundwater. The phase stability diagrams show that the eH-pH values of groundwater samples in the arsenic affected areas lie in the iron and arsenic soluble ficlds of the diagram. It indicates that arsenic and iron in the groundwater is likely to remain in soluble arsenite and ferrous form. The presence of soluble iron and arsenic (1II) in fresh groundwater supports the findings. The presence of very low sulfate concentration found in the groundwater is also consistent with a reducing environment, and negates Arsenic mobilization as a result of oxidation of Arsenic bearing minerals. Arsenic release from sediment was studied in the laboratory by simulating anaerobic reducing environment prevailing in aquifers in arsenic affected areas by introducing organic carbon in the form of glucose and molasses in closed reactors. Significant quantities of Arsenic were released in aqueous phase from sediment under anaerobic reducing condition at low Eh while no arsenic release was observed in control batch where enough oxygen was allowed to enter into the reactor to maintain aerobic condition. Arsenic was released from the sediments only when Eh values were lowered to less than zero. The study demonstrated that bacteriamediated reducing state was a requirement for the release of arsenic from sediments.Item Assessing the effectiveness of iron - coated bottom ash in removing arsenic , manganese and iron from groundwater(Department of Civil Engineering (CE), 2009-07) Mahbuba Iasmin, Most.; 1007041031 PArscnic removal USing iron-coated botlom ash (ICBA) IS a novcl proccss of removing arsenic fi'om groundwater invcntcd by rcscarchcrs at Lawrence Berkeley International Laboratory, USA. Adsorption/co-prccipitation mcthod has been cmploycd in this ncw technology. The prcscnt study involvcs development of a community-based trcatment unit and investigations relating its performance using iron coated bottom ash (lCBA) in reducing the clcvatcd Icvels of arsenic, and other contaminants such as iron and mangancse from groundwater of Bangladesh. In this rcsearch, the samples have been collccted for batch analyscs from Besgao village, Sreenagar, Munshiganj, an arsenic affected area which has been the subject of several arscnic rclatcd investigations for the last five years. From the investigations performed in the laboratory scale, an ICBA dosage of 4 giL and coagulant dosage of 0.25 gil have been found to be optimum for good arsenic removal and therefore selected for subscquent batch cxperiments. ICBA seems to work better for pH levels 5.71-8.78 for synthetic groundwater samples. The higher the initial pH, the higher is thc arsenic removal. Interference of phosphate content with arsenic removal has been obscrved to increase with the increase in phosphate concentration. Further investigations are necessary to better understand the mechanism of phosphate with arsenic adsorption using ICBA. Results from the investigations performed with the community based tre~tment unit show that the performance of the unit varies with the flow rate. A flow rate of 100 Liters per hour provides the best pcrformancc. The lower the initial arsenic concentration, the betier is thc pcrlormancc of thc prototype in reducing arsel11c concentration in the treated water below the Bangladesh drinking water standard. Performance of the unit in removing inevitable bacteriological contamination is enhanced when there is low level of contamination. For higher TC/FC, it takes around eight days to attain the rcquired bactcriological quality of water. Presence of Iron-Related Bacteria (lRB) seems to change the performance of ICBA in removing As, Fe and Mn by attacking the adsorptive bonds between the contaminants and the ICBA. The number of IRB population has been observed to be as high as 1,40,000 cfu/ml in thc raw groundwater. This number can be reduced to 9000 efu/ml after trcatment with ICBA and chlorination dosc of 1.55 mg/L, but cannot bc completely rcmoved within a rcasonablc limc. It is important to mention that the number of TC/FC present in the same water is also very high. In that case, presence of high IRB may have some contribution in giving false notion of prcsencc of such high TC/FC. Arsenic sludge ii'om iron coated bottom ash does not allow arsenic to Io::achout under low pH environment. However, very high pl-! conditions ('" 11) can cause leaching of arsenic from the sludge. Both arsenic and cadmium contents in raw wastes and leachates arc within the guidcline practiced for surface disposal according to US EPA (1995). For groundwater having low initial arsenic concentration (around 200 ~g1L), low initial manganese content (S O.I25 mglL), and low bacteriological contamination, a hundred liter per hour prototype can be successfully implemented in treating the groundwater to achieve the Bangladesh drinking water standard. However, aesthetic quality of the treated watcr is not possible to obtain for high level of iron content (> 6 mg/L) without incorporation of a filtration unit. Howcver, acccptability of this prototypc system to the community could not be ascertained as the prototype lu; not been installed in the field for use of the community.Item Accumulation of arsenic in rice plant from arsenic contaminated irrigation water and its effect on nutrient content(Department of Civil Engineering (CE), 2005-04) Zahangir Alam, Md.; Mujibur Rahman, Dr. Md.To achieve self-sufficiency in food grain production, the HYV rice varieties are widely produced in Bangladesh, particularly in the dry season, and this requires a large volume of groundwater for irrigation. Groundwater of many areas of our country is severely contaminated with arsenic. So, there is a possibility of arsenic .accumulation in rice plants from arsenic contaminated irrigation water. Generally, consumption of protein is not adequate for our people due to insufficient production of major protein sources like fish, meat, milk, eggs, etc. and also due to economic constraints. Any adverse effect on protein content in rice due to use of arsenic contaminated irrigation water may, therefore, aggravate the malnutrition problem of our people. Similarly any adverse effect on amylose content, which is about one forth portion of rice grain by weight, would cause deficiencies in calorie supply. This study aims at assessing the accumulation of arsenic in rice plants and its possible effect on nutrient (protein and amylose) content of rice grains. Arsenic contents in different parts of rice plants were tested using hydride generation Atomic Absorption Spectrophotometry (Shimadzu, AA6800). For assessing nutrient contents (protein and amylose), rice samples were tested at the Laboratory of Grain Quality and Nutrition Division of Bangladesh Rice Research Institute (BRRI), Gazipur. Results from this study show that arsenic accumulates in different parts of rice plants, though the accumulation varies from variety to variety. Highest arsenic concentration was found in root hair with a mean 16.7 mglkg and maximum 38.5 mglkg, and least in grain with a mean 0.32 mglkg and maximum 1.1 mglkg. Mean arsenic concentrations in husk, leaf and stem were found to be 1.06 mglkg, 3.98 mglkg and 3.32 mglkg, respectively. Presence of arsenic in straw (leaf and stem) at moderately high concentration poses risks for cattle and human health. Arsenic concentration in top soil samples of study fields were found to be up to 12 mg/kg. From linear regression analysis only a moderate correlation (R2 = 0.45) was found between arsenic in water and arsenic in root hair. Measured nutrient contents were compared with the standard values. Test results for protein content show rice grain contain less protein than standard values. Similarly, for most samples, amylose content was found to be less than standard value. More studies are needed to better understand these phenomena.Item Contamination of agricultural land by arsenic from irrigated water(Department of Civil Engineering, 2009-01) Shahinara Begum, Musammat; Hossain, Dr. Md. DelwarEnsuring safe drinking water is one of the prime objectives of the Government and the others those arc working in the water supply sector in Bangladesh. Arsenic is not only present in water but also in soil which are the main media of food production. The present study has been conducted to observe the contamination of agricultural land by arsenic from irrigated water. The study was conducted to find out a correlation between arsenic concentration in irrigation water and soil nutrient of different locations of Sadar upazila, Keshabpur upazila and Jhikargacha upazila of Jessore district. From this study it has been found that water of a significant number of irrigation wells in Jessore district (Sadar upazila, Jhikorgacha upazila and Keshabpur upazila) are contaminated by arsenic. There is no significant correlation between arscnic in ground water and other important parameters of ground water. In Keshabpur upazila, irrigated soil was collected ii'om SIX locations and corresponding irrigation water also collected and tested. However, it is found that relation between arsenic concentration of irrigation watcr and arsenic concentration in irrigated land is insignificant. The food chain issue is becoming more and more important as there is increased evidence of arsenic buildup in crops and different types of vegetation. In Samta village of Jessore district, rice and wheat are irrigated with arsenic affected water and it has been found that irrigated lands are also affected by arsenic. Average arsenic concentrations in rice grain are higher than wheat. However, the concentration of arsenic in rice and in wheat grain is insignificant. Arsenic concentration in root, grain and straw of rice is higher than wheat. The values obtained with grain, straw and root agreed well with the general trend of variation, i.e., grainItem Arsenic removal from groundwater by alum(Department of Civil Engineering, 2004-08) Ehosan Habib, Md.; Abdul Jalil, Dr. Md.Widespread arsenic contamination of shallow aquifers in Bangladesh has posed a major public health concern as most of its population uses the aquifers as the sources of water supply. There is an urgent need to supply arsenic-safe drinking and cooking water to the millions of arsenic affected people in Bangladesh. The present study is focused on removal of arsenic from groundwater by alum coagulation. An arsenic removal unit based on co-precipitation-adsorption-sedimentation and filtration processes was used to study the arsenic removal efficiency under a variety of conditions both in the laboratory and field. Optimum alum dose for As(V) removal was found to be 100 ppm and the percent removal efficiency was better for higher initial arsenic concentration. A moderate mixing of the coagulant was required for satisfactory removal of arsenic from water. The optimum sorbate/sorbent ratio was 75 flg As I mg AI. Under normal concentrations of pH, alkalinity, hardness, chloride, nitrate, ferric iron, silicate in Bangladesh groundwater, these parameters individually had no significant effect on arsenic removal efficiency. Fe(II) enhanced the efficiency slightly. Phosphate decreased the removal efficiency significantly. At low concentrations, anions had no synergistic effect on arsenic removal efficiency, but at medium to high concentrations, the anions reduced the removal efficiency very significantly. At low permanganate dose (1.0 ppm) and medium iron and phosphate concentrations (5.0 ppm and 3.0 ppm, respectively), the removal efficiency varied little with the form of arsenic. Higher concentration of Fe(II) in the feed water required higher dose of potassium permanganate for effective As(III) removal. Sand filtration was very effective in removing residual color and residual arsenic. One hour settling time in the top bucket was found enough for the alum based arsenic removal unit. It was found that the adsorption capacity of the iron present in the sand filter greatly enhanced the arsenic removal efficiency. Performance of arsenic removal unit was evaluated in the field in order to determine their suitability at household levels. The variations of raw water arsenic and phosphate concentrations with time were found significant. The residual arsenic concentrations in the treated water of 3 field units were found to be mostly below 20 ppb, much below the Bangladesh standard at alum dose of 100 ppm and permanganate dose of 1 ppm. These doses were enough to remove arsenic effectively from natural groundwater if its iron content was high (~ 9 ppm) and phosphate content was low «1.0 ppm). Alum dose of 100 ppm and permanganate dose of 1 ppm could not produce arsenic-safe water of two field units where moderate amount of iron (4.0 - 5.0 ppm) and high concentration of phosphate (4.84 - 5.54 ppm) was present in the raw water. Higher permanganate dose was required for effective arsenic removal by the two field units. For arsenic and phosphate concentrations of 190 ppb and 4.84 ppm respectively, the required permanganate dose was 3 ppm. The permanganate dose requirement was 6 ppm for arsenic and phosphate concentrations of 278 ppb and 5.54 ppm respectively. Under favorable conditions (low phosphate concentration and high iron concentration), the unit removed arsenic satisfactorily without addition of any chemical. All the five tubewells were bacteriologically contaminated. So chlorine dose was introduced and it was found that 0.45 ppm was satisfactory for disinfections. Filtration removed a substantial amount of arsenic (39-49%) when natural iron content was 9 to 20 ppm. Proper operation of the system was essential to obtain satisfactory performance. Users' acceptability of the units was found to be satisfactory especially among the poor and conscious people.Item Assessment of hematite nanoparticles as adsorbent for arsenic removal(Department of Civil Engineering, 2009-01) Mahbuboor Rahman Choudhury; Ali, Dr. M. AshrafWidespread presence of elevated levels of arsenic (As) in groundwater is a major public health concern in Bangladesh. Although a number ofmcthods are presently used for removal of As from groundwater, they all suffer from certain drU\vbacks. Technologies based on nanoparticles (typically 1-100 11m in size) have received significant attention in recent times regarding their prospective lise in groundwater treatment (e.g., for As removal). However, because their minuscule size, nanoparticles cannot be used directly in an As removal system. For developing such a system, it is extremely important to characterize the nunoparticle itself (e.g. size, aggregation characteristics. etc.) and also to assess their adsorption characteristics. In this study, adsorption characteristics of arsenic on commercially procured hematite nanoparticles (HNPs) have been assessed in laboratory batch experiments. Characterization tests of the commercially procured HNPs were carried out to assess the structure, composition, particle size, distribution, specific surface area and surface charge. The XRD analysis confirmed structure of the a-Fe20) (Hematite) nanoparticles and absence of significant impurity. The specific surface area of the nanoparticles found from the BET test (13.81l1~/g) \vas well below the manufactured-rep0l1ed value of 50rn2/g. Potentiometric titration revealed the pH of zero surfltce charge (i.e., pHpzC>of IINPs to be around pH 6.5. which is an important parameter in assessing the adsorption characteristics. An important tinding of the DLS test was that the hydrodynamic radius (I5.0 under similar conditions. For pH<5.0 the adsorption of arsenite and arsenate \vas almost similar. \Vith increasing pH there was an initial decrease of arsenate adsorption onto hematite nanoparticles with the maximum adsorption of 0.065 mol/kg occurring at around pH 4.0 and minimum adsorption of 0.040 mol/kg at around pH 7.0. As pH increased further, adsorption of arsenate increased gradually to about 0.058 Illollkg at around pH 10.0. Similar but less pronounced trend was observed for the adsorption of arsenite on HNPs. The effect of pH on adsorption of As could be explained by the aggregation characteristics of HNPs and charge on the aqueous arsenic species. Adsorption isotherms showed that the maxilllulll As adsorption capacity (590~1I1101/gat pH 9.3) was more than that of arsenate (435~111l01/gat pH 6.1). However. at lower concentration of As «I71.1I1101/L), the adsorption of arsenate was more than that of arsenite. Significant reduction in the adsorption of both arsenite and arsenate on HNPs was observed in the presence of co~cxisting phosphate (PO/) Adsorption of As from natural groundwater on the HNPs was also found to be lower than that from aqueous solution containing inditTerent electrolyte NaNO). These results suggest significant effect of competing ions and aggregation properties of HNPs on As adsorption. The effect of dispersion of the HNPs on adsorption was found to be significant. Kinelics experiments showed that As adsorption reached equilibrium within 24 hours, with majority of adsorption taking place within the !irst few hours. The results of arsenic adsorption on HNPs indicates that along with other adsorbents (e.g., MnO" Geothite, Alumina, Fe(OH)" TiO,), the HNPs could be used as an effective adsorbent for As removal. The higher arsenite adsorption capacity of HNPs could potentially be used in removing As from groundwater (without the necessity of an oxidizing agent). where it is present primarily as arsenite. HNPs could be used for both in-situ and ex-situ treatment of groundwater; hO\vcver, such treatment systems must be carefully designed keeping in mind the adsorption as well as aggregation characteristics of the nanoparticles.