A FIELD TRIAL ON THE PREVENTION OF COLOUR FORMATION IN TUBE WELL WATER OF CHAVAKCHCHERI AREA

Abstract

In Chavakachcheri (Jaffna district), an unpleasant odour, taste, and reddish-brown colour developed with time when clear water was drawn out from some tube wells. The coloured water has created problems in carrying out essential daily work. The previous research (paper 66, OURS 2020) findings reveled that brown colouration is due to Fe(OH)3 and both coconut shell (CSC) and rice husk charcoal (RHC) of 212 µm (0.025 g in 25 mL of water) were effective in preventing colour formation by adsorbing iron (>78%) from tube well water within one minute of equilibration. The objective of the study was to apply these findings on a large scale in a user-friendly manner with respect to particle size, filtering medium and shaking to the community and get their views for further development. In this study, water samples were taken directly from the tube wells and total [Fe] was determined using the thiocyanate colourimetric method. Since RHC did not settle and could not be filtered using household filtering methods, a study was carried out with CSC only. In optimising studies of CSC, different weights of hand crushed (approximately 1 cm2 area) and uncrushed charcoal were added to 500 mL and 5 L of water and were shaken 10 times every 5 minutes for 1 hr., filtered using a single cloth strainer and total [Fe] was determined before and after equilibration. The applicable least weight of biosorbent/volume of water ratio of crushed and uncrushed CSC was 0.3 – 4.0 g /500 mL and 20 g/5 L. The community trial for 6 houses was done in the rainy season with 20 g/5 L shaken 10 times /every 5 minutes for 1 hr., and nearly 50% of Fe could be removed. Treated water was used to wash a white pillowcase 3 times and allowed to sun-dry. Kept treated water in white porcelain cups for 6 hrs. Neither pillowcases nor porcelain cups were discoloured. The trial was repeated, and the results were the same. Face-to-face interviews with the householders showed that they were satisfied with the process and the outcomes, but wanted to simplify shaking and improve the filtering strainer type. The effect of shaking on Fe adsorption on CSC was determined with unshaken and shaken samples at different time intervals for different time durations. There was no effect of shaking. When applied to the community, Fe adsorption >50% resulted. To avoid filtering, a sack of different material (cotton, cotton + polyester) filled with CSC were applied but was unsuccessful since the sac materials used reduced the adsorption of Fe by CSC. The treated water was tested for drinking water quality chemical parameters, and the results showed that CSC can reduce the [Fe] to an acceptable level even in larger volumes of water without shaking. In addition, CSC can reduce the turbidity, Cl-, TDS, SO4- and total hardness levels, but some only to the accepted level. This study shows that hand-crushed CSC can be used as a cost-effective, environmentally friendly biosorbent in a simple way to prevent colour development by Fe in water, with other additional advantages.