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ARSENIC BIOSAND FILTER:
“STUDY ON THE EFFECT OF AIR SPACE BETWEEN THE RESTING WATER AND
THE DIFFUSER BASIN ON ARSENIC REMOVAL AND DETERMINATION OF
GENERAL FLOW CURVE” (A case study of Nawalparasi district, Tilakpur V.D.C.)
A Thesis Submitted for partial fulfillment for the Bachelor Degree in Environmental Science (Honor’s Degree) to the department of Biological Science and Environmental Science School of Science, Kathmandu University
By Shashank Pandey
Kathmandu University July 2004
Declaration by student
I, Shashank Pandey, hereby declare that the work presented herein is original work done by me and has not been published or submitted elsewhere for the requirement of a degree programme. Any literature date or work done by other and cited within this thesis has given due acknowledgement and listed in the reference section.
Shashank Pandey Place: Kathmandu University Date:
Certificate
Certified that the thesis entitled “STUDY ON THE EFFECT OF AIR SPACE BETWEEN THE RESTING WATER AND THE DIFFUSER BASIN ON ARSENIC REMOVAL AND DETERMINATION OF GENERAL FLOW CURVE” (A case study of Nawalparasi district, Tilakpur V.D.C.) submitted by Mr. Shashank Pandey towards partial fulfillment for the Bachelor’s Degree in Environmental Science (Honors degree) is based on the investigation carried out under our guidance. The thesis part therefore has not submitted for the academic award of any other university or institution.
___________________ ___________________
Dr. Sanjay Nath Khanal Dr.Roshan Raj shrestha (Supervisor) (Supervisor) Associate Professor
Abstract
The study attempt to investigate the effect of air space between the diffuser basin and the resting water level on removal of arsenic by the Arsenic Biosand Filter. In addition, the study focused on the determination of general flow curve for the filter , determination of time required for volume of water to be filtered and also to comprehend the social acceptance of the filter.
Four filters from Tilakpur VDC of Nawalparasi district were selected for the research.. Altogether 150 water samples were collected and flow rate of each sample was taken. The collected samples were tested for arsenic by using ENPHO arsenic field test kit. Besides this, the social acceptance of the filter was evaluated through questionnaire and informal survey.
To accomplish the objective some hypothesis was set. And the result obtained from the research was compared with the hypothesis set. And according to the comparison the result and conclusion were made. And thus the result obtained from the research was not according to the hypothesis set and this thesis describes the different reasons not satisfying the hypothesis
List of abbreviations
As: Arsenic AIRP: Arsenic Iron Removal Plant Bp: Boiling point BCHIMES: Between Census Household Information Monitoring and Evaluation Centre BSF: Bio Sand Filter CBS: Center Bureau of Statistic Conc.: Concentration DWSS: Department Of Drinking Water Supply And Sewage DMAA: Dimethyl Arsenic Acid ENPHO: Environment and Public Health Organization. EHC224: Environment Health Criteria 224 GOs: Government Organizations IARC: International Agency for Research on Cancer. INGO: International Non Government Organization L: Liter MMAA: Monomthyl Arsenic Acid. Mp.: Melting Point. MIT: Massachusetts Institute of Technology. NGO: Non-Government Organization NRC: National Research Council NRCS: Nepal Red Cross Society. NEWAH: Nepal Water for Health. Ppb. Parts per billion Ppm.: Parts per billion. RWSSP: Rural Water Supply and Sanitation Program RWSSFDB: Rural Water Supply and Sanitation Fund Development Board. TDI: Tolerable Daily Intake UNICEF: United Nation Children Fund. VDC: Village Development Committee. WHO: World Health Organization.
List of Tables
Table 1: Proposed drinking water quality in Nepal Table 2: Properties of arsenic Table 3: Major arsenic minerals occurring in nature Table 4: The national standard of few countries for arsenic in drinking water Table 5: Arsenic level at different district in Nepal as November, 2003 Table 6: Identification of four filter
APPENDICES
Appendix A: Defining the terms used during the sample collection Appendix B: List of data obtained during the survey Appendix C: Photographs
Table Of Contents
3.3.4 Method used for collecting the sample 30
CHAPTER 4 RESULT AND DISSCUSSION 4.1 The effect of air space between the resting water and diffuser 31 Basin in removing the arsenic from Arsenic Biosand Filter 4.2 The flow pattern of water inside Arsenic biosand filter 35 4.3 The time required for the volume of water to be filtered from arsenic 39 biosand filter 4.4 The social acceptance of the filter 42
CHAPTER 5 CONCLUSION 43
CHAPTER 6 RECCOMENDATION 44
REFRENCES
ANNEX A: Defining the terms used during the sample collection
ANNEX B: Table of Data Obtained During The field Study
ANNEX C: Photographs
ANNEX D: Maps
CHAPTER 1 HISTORICAL BACKGROUND
Water resource, water supply and water quality in Nepal
Nepal is the 2nd^ richest country in water resource in the world, possessing about 2.27% of the world water resource (CBS 1999). Despite this fact planned water supply was stated only in the fourth plan (1970-1975). The national coverage of water supply system was only about 4% in
- A separate institution, the Department of Drinking Water Supply and Sewerage (DWSS) was established during that period. By the end of water supply and sanitation decade (1990), the coverage substantially increased to 36% of the total population, with the rural population and urban population at 33% and 67% respectively. The recent Between Census Households Information, Monitoring and Evaluation System (BCHIMES) report-2000 indicates water coverage at 78% for rural and 92.3% for the urban population (Shrestha, 2003).
Sanitation facility is very poor condition having only 29% national coverage and issue on water quality has not been given proper attention (Shrestha et.al, 2203). Rural communities continue to use the most convenient source of water irrespective of quality. Regular outbreaks of water borne epidemics and increasing number of patients being admitted to hospitals due to water related diseases indicates that only supplying of drinking water is not sufficient to improve public health status unless continued effort is made both on water supply and sanitation. Nepal water resources are considerable with surface run-off in the order of 200 km3 annually. In general, there is very little rainfall from November to January. In addition to surface water, Nepal's ground water resources are also extensive.
In Nepal, the guideline value for national drinking water quality standard has been suggested by Pyakural (1994) and Task Force (1995)
Provision of arsenic free water is the only option to safeguard public health in arsenic affected communities. There are several safe water options like improved dug well, pond water filtration, spring water or deep boring water supply. However, all of these options may be unavailable and unaffordable. In this case, arsenic affected communities should be provided with practical and inexpensive household level treatment options. Different types of arsenic removal techniques have been adapted throughout the world in arsenic-affected communities
Most of these treatment techniques are based on coagulation, precipitation, simple aeration, and adsorption. Treatment through activated alumina, use of coagulants and the three kolshi system with iron filings are some of the most common household-level treatment techniques employed in West Bengal and Bangladesh. In Nepal, the provision of safe drinking water options in arsenic- affected communities is still inadequate. Only a few agencies like the Nepal Red Cross Society (NRCS), Rural Water Supply and Sanitation Support Program (RWSSSP), and Rural Water Supply and Sanitation Fund Development Board (RWSSFDB) have safe water provision programs. However, safe water options are usually only reserved for communities who received tube wells under an agency's program. Therefore many arsenic affected communities are yet unaware of treatment options available. In addition, although household treatment options like Two Gagri Filter (a ferric chloride coagulation and filtration process) and Three Kolshi System (a iron fillings adsorption and filtration process) have been practiced in some communities, these options were found to have several technical and social problems after a few months of operation. The problems include quick clogging, difficulties to supply chemicals regularly, and an increase in microbial contamination in treated water
1.2 Objectives and Limitation of the Study
1.2.1 Objectives
The broad objective was to study about the Arsenic Bio-Sand Filter in the Nawalparasi district, Tikapur Village development committee. The specific objectives of the study were:
- To examine the effect of Air space between the resting water and diffuser basin in removing the Arsenic from Arsenic Bio-Sand Filter.
- To determine the flow pattern of the filtered water inside Arsenic Bio-Sand Filter.
- To determine time required for a volume of water to be filtered from Arsenic Bio-Sand Filter.
- To study the social acceptance of the Arsenic Bio-Sand Filter.
1.3 Limitation of the study
- All filters from the Tilakpur V.D.C. were not selected because not all filters were in good condition and also due to time and budget limitation.
- In the case of one filter, the time required for the volume of water to be filtered was not taken, because of the time constriction.
- Some water samples could not be analyzed for cross checking due to the budget limitation.
Another objective was to determine the flow pattern of water inside Arsenic Biosand Filter.
Darcy’s law governs the flow rate of the filter. That is the filter flow rate is proportional to the water level above the outlet pipe. The higher the water level, the higher the hydraulic head, which leads to higher Darcy’s flux through the sand, which in turns means higher flow rate (Ngai.T, 2003.) The imaginary line is drawn according to our hypothesis (Figure..). It is assumed that if the volume of water in the basin is 100%, then the flow rate is maximum (100%) and if there is no any water left in the basin (0%), the flow rate is also 0%
Figure 2: Imaginary line for the flow curves.
0%
20%
40%
60%
80%
100%
1 2 3 4 5 6 7 8 9 Amount of water in the basin (%)
Flow rate (%)
Imaginary Line
CHAPTER 2 LITERATURE RIVIEW
2.1 Chemistry of Arsenic Arsenic is P-Block, group IV element of the periodic table. It has an atomic number 33 and atomic mass 74.91 with the five electrons in outer most shell. The oxidation state of Arsenic compounds found in the environment is either III or V. The two-electron reduction of arsenate As (V) to arsenite As (III) is favored in acidic solution, where as the reverse is true in basic solution. Arsenic can exist in four valency states -3, 0, +3 and +5. Element arsenic is not soluble in water, under moderately conditions, arsenite (+3) may be the dominant form, but arsenate (+5) is generally the stable oxidation state in oxygenated environment. Arsenic is stable in dry air, but tarnishes in moist air, giving first a bronze then black tarnish. When heated in air it sublimes at 615?C and forms AS4O6 not AS4O10 but depending upon the oxygen presents (Lee, 1994)
Table 2: Properties of arsenic Atomic Weight (^12 C= 12.0000) 74. Mp at 39.1 Mpa (38.6 atm), ?C 816 Bp, ?C 615, sublimes Density at 26?C, Kg/m^3 Covalent radius 1.21?A Ionization energy (Kg/mol) 947 (1st) 1950 (2nd) 2732 (3rd) Latent heat of fusion, J/ (mol K) 2 27, Latent heat of sublimation, 31, Specific heat at 25?C, μm/(m?C) 5. Electrical resistivity at 0?C, μ? cm 26 Magnetic susceptibility at 20?C, cgs -5.5*10- Bond type Covalent Crystal system Hexagonal (rhombohedral) Pauling’s electronegativity 2. Hardness, Mohr’s scale 3. (Source: Othmer, 2002; Lee, 1994; EHC224, 2002)
