RIVER-BANK FILTRATION: CLOGGING EFFECTS

Abstract

Water is an indispensable source of living. Adequate amount of water both in terms of quantity and quality is requisite for human existence. Access to good quality and sound water makes stupendous difference in our quality of life. As we enter twenty first century, it is observed that the trend towards urbanization is posing ever increasing challenges to water supply. India accounts for only 4 % of world's average annual supplies, while its population is 17.86% of world's population. This reflects how much stress is there on fresh water resources and on immediate need for potable water. Many cities are located at the bank of rivers and are dependent on river water for drinking purpose which is supplied after treatment to inhabitants. But, due to pollution and sewerage disposal in water bodies, quality of the water is degrading and cost of treatment is escalating. Especially during summer when surface flow of the river is negligible, water quality gets detrimental and generate problem in water supply. This shows an expedite need for an economical system to supply potable water all-round the year. River bank filtration-RBF is one of the most productive and low cost technology for obtaining required amount of water throughout the year. In many countries like Europe and United States, RBF is the successfully adopted method for public water supply. But, the main problem we come across in River bank filtration is "clogging". In present study, laboratory experiments were conducted to find mechanism and the parameters which influence clogging process. Through experimental analysis it was found that Ratio of mean size of filter material to mean size of suspended particles, Concentration of suspended load, Initial flow rate and time are the main factors that influence clogging process. After that an attempt was made to compare experimental results with existing equations given by Schälchli and found that with increase in head loss, hydraulic gradient increases resulting in increase in specific resistance. Regression analysis was also performed on observed data by using STATISTICA software and equations were developed for calculating hydraulic conductivity of two uniformly graded fine grained soil samples with different porosity as clogging progresses. The equations developed were found to fit best with in the given range of data