Challenges for Implementation of Rain Water Harvesting Project in Arsenic affected areas of Bangladesh

Transcription

1 Challenges for Implementation of Rain Water Harvesting Project in Arsenic affected areas of Bangladesh Md. Mafizur Rahman (Ph.D.) Associate Professor Bangladesh University of Engineering and Technology Dhaka, Bangladesh

2 DISTRIBUTION PATTERN OF ARSENIC

3 Background Crisis in supply of safe drinking water due to increasing trend of arsenic contamination in the ground water. Challenges in replacing handpump, tubewells. RWHS,an alternative water supply option --> since 1997 in Bangladesh.

4 The average annual rainfall 1400 mm.

5 Background (Contd) Advantage: Free from arsenic contamination. The physical, chemical and bacteriological characteristics Disadvantage: High initial cost.

6 To monitor and document water quality, water security, general system management Objectives of the Study To assess technical requirements and feasibility evaluation of cost-effectiveness of tanks of various sizes socio-economic condition of the people To address the socio-economic aspects To evaluate Users' Acceptability To evaluate Cost and affordability

7 Objectives of the Study (Contd.) To monitor long term sustainability To evaluate the social impacts To document good practices and lessons from the study -->disseminate among the sector agencies, community people.

8 Technical Options of RWHS Ferro Cement Tank Brick Tank

9 Ferro Cement Tank Brick Tank (Under ground)

10 Brick Tank Concrete Ring Tank

11 Ferro Cement Jar Brick Tank

12 Motka (Earthen) But additional tanks may be built to ensure a high level of service when money will be available.

13 Study Area The study area-->arsenic affected villages at Bagha and Charghat Upazilas in Rajshahi district in the western part of the country. Total 3,290 families-->13 villages namely Miapur, Anupampur, Arazi Sadipur, Chandpur, Talbaria, Kaluhati, Batikamari, Fakirpara, Jotnasti, Kishorpur- Beelpara, Monigram, Habashpur and Bajubagha.

14 Project Area Rajshahi District Charghat & Bagha Upazilas 13 arsenic affected villages

15 Status of Fe and As affected GW sources in the study area 80 Percentage As% Fe% Village no. Figure: Relationship between As and Fe affected ground water sources.

16 Contd. The average family size: 4.31 to 5.2. Main occupation: Agriculture (61.29%).Business (14.51%), Day laborers (15.14%), Service holder (4.71%), other occupation (4.53%). No strong educational background. Most of the villagers live below poverty line. Example: In Kaluhati village among 776 people 458 (59.2%) were living always in financial deficit.

17 Methodology of the Evaluation Study Technical evaluation of the RWHS--> analysis of design considerations, field observation, case studies, interviewing people. Interview-->140 families (caretakers)--> evaluating the cost and affordability and maintenance of RWHS-- > base line studies. The study population :11 to 60 year age groups. Randomly selected water samples--> laboratory testing--> stored rainwater quality.

18 Data Collection and Analysis Rainwater Storage Reservoir Storage=Actual supply of fresh water-water demand Supply: Average catchment area for RWH=20m 2 (approximately) Run-off coefficient = 0.8 (assuming for ideal CI roof catchment) Average yearly rainfall = 1400 mm Average annual water supply from rainfall = 20 m 2 *0.8*1.4 m =22.4 m 3

19 Contd. Demand: Consumption per capita per day, C = 7.5 liters Number of people per household, n = 6 Monthly water demand = 7.5*6*30 = 1350 liters = 1.35 m 3 Annual demand = 1.35* 12 =16.2 m 3 Storage volume required for a nuclear family = =6.2 m 3 (Assumption: Water demand 7.5 L/ person/ day --> drinking and cooking purposes)

20 Rainwater Storage Reservoir Total 268 RWHS capacities -->300 liters, 500 litters, 1.0 m 3,2.0m 3,2.5 m 3, 3.2m 3 materials-->concrete, brick, Ferro-cement, plastic, Earthen Motka etc. Tank types --> FC tiles tank, FC Jar, RCC ring, Brick tank, Chari tank,earthen motka, plastic tank.

21 r 2 FC tiles tank (4500tk) RCC ring(4400tk) Brick tank(5000tk) Brick tank (ss)(5500tk) FC jar(4400tk) Reservoir type Number of reservoi Figure 1: Number and types of reservoir of capacity 2500 liter and catchment area sft.

22 .FC jar, RCC ring, brick tanks of 1000 liter--> used at less frequency (Fig. 2). Num ber of reservoir FC jar(2800tk) 6 5 RCC ring(2700tk) Brick tank(3500tk) Reservoir type Figure 2: Number and types of reservoirs of capacity 1000 liter and catchment area sft.

23 Earthen motka-->low income group people(such as agri-labor,day labor)-->monthly income less than 1500 Tk. Number of reservoir Plastic tank(3300tk) 127 Earthen motka(550tk) Reservoir type 8 Brick tank(1300tk) Figure 3: Number and types of reservoirs of capacity 500 liter and catchment area sft.

24 Interviewing 140 families--> FC jar, Brick tank, Earthen motka, plastic tank--> used by 35, 39, 37 and 2 families respectively (Fig.4)-->low cost, capacity, durability, availability of the reservoir and materials % 1.40% 25% FC jar FC tank Brick tank 5% 27.90% 14.30% RCC tank Earthen motka Plastic tank Figure 4: Percentage of different types of reservoir in use during survey period.

25 Contd. The FC tiles tanks -capacity 3200 liter, RCC ring tanks -capacity 2000 liter, plastic tanks-->limited use -->relatively higher cost against capacity, need of high catchment area. Chari tank-->limited use--> low performance.

26 not washing the empty storage tank with bleaching powder. Quality of Harvested Rainwater 1340 water samples Tested TC:samples 894 bacteria free, 446 contaminated. FC: samples 1083 bacteria free, 254 contaminated Causes not cleaning the roof catchment & inlet gutter before rain events, Improper release of first flush

27 Contd water samples-->ph:335 samples within the acceptable limit ( ) water samples-->turbidity:50 samples unacceptable (greater than 5 NTU)--> improper collection of water from the catchment. Pb and Zn: all within acceptable limit. Iron and Fluoride: below detectable range of measurement, i.e., < 0.05 mg/l.

28 Operation & Maintenance Low cost of O&M, nearly 20 Tk/ year. Poor operation and maintenance : Lack of education and awareness.

29 Table1: Types of caretakers considering quality of O&M of different types of reservoirs Type of reservoir Good Medium Bad Total no. of reservoirs FC jar FC tank Brick tank RCC ring Earthen motka Plastic tank Less number good caretakers of Earthen motka(table 1)-->used by the people of low income group,almost no educational background.

30 Social Aspects Economic value of Rain Water. Change of beliefs and attitude toward Rain Water. Positive health effect for using Harvested Rain Water. Growth of ownership feelings and enhancement of status. Development of Rain Water Management Skill. More time saving for fetching household water

31 Comparison of RWHS with different options in practiced in the project area: Best Better Good Good Better Best RWHS Dug-well RWHS Three Pitchers RWHS BTU RWHS SODIS RWHS No. 6 TW

32 Comparison of RWHS with Tubewell from different aspects: Best Better Good Good Better Best RWHS Water Quality Tubewell RWHS Water Quantity Tubewell RWHS Time cost Tubewell RWHS Labour Cost Tubewell

33 Social advantage received by the users (especially the Women) from RWHS: Less fuel cost for Cooking 1 Positive from religious view 3 Convenient for Pregnant women 4 Feels proud for Plant 5 Advantages Minimum Labour Cost Minimum Time Cost Easily Available Suitable for Cooking Available inside house Arsenic free water Respondent (nos.)

34 Conclusion Rain water is potentially safe, reliable and affordable alternative source of water supply. Can be used for drinking and cooking for at least 8-10 months of the year. RWHS is widely used because different types of reservoirs are available and people of different income level can afford it according to their income level. Simple operation and low maintenance cost (20Tk/year)

35 Contd. Availability of CI roof catchment area. The quality of stored rainwater is well accepted by people of the study area.

36 RERCENT MODIFICATION AND PROBABILISTIC MODELING APPROACH FOR DESIGN OF COST EFFECTIVE RWHS

37 Calculate the daily demand = Demand of 1 person No. of persons. Draw a vertical line from the daily demand value to the appropriate room area line. Then draw a horizontal line from the previous intersection to the vertical axes to obtain the tank size. Tank Size (liters) Sardah : Chart 6 Catchment Area (m 2 ) Dem and (liter/day)

38 If you don t know the size Calculate the required Tank size OR Take the tank size you have decided to make. Then draw a vertical line from base to the appropriate curve (for persons to be served) The ordinate of the intersecting point is the degree of security Sardah : Chart 5 Degree of Security (%) Person 3 Persons 5 Persons 7 Persons Storage Volum e (liter)

39 The probabilistic design approach can be adopted for design of RWHS at any part of the World and Bangladesh as well Cost effective RWHS Known risk/reliability of the system

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