Studies on Chemical Effect and Feasibility of Biosensor for Arsenic Detection in Water.

Abstract

220 water samples of different Arsenic (As) -affected areas in Bangladesh have been collected for analysis. Of them 58 samples were from Sagordari village of Jessore. 53 from Koyra village of Kolaroa, 56 from Hajigong village of Chandpur and 53 from Arihazar village of Narayangonj district. Various water quality parameters such as, p1-I, conductivity, chloride, iron content, hardness and dissolved oxygen were analyzed using standard analytical techniques. The suitability of investigated water for drinking and other purposes was also analyzed comparing with standard values. As content for the 220 different water samples have been perceived in there different methods, i.e., Merck field test kit, ARSOlux biosensor and ICP-MS methods. To find out an easy, low cost and environmentally friendly method for As content in ground water three different methods have been adopted. A comparison has been made among the three different test methods. Effect of different water quality parameters on As test methods has been analyzed. The p1-I range has been found to 6.2-8.1. It is seen that most of the samples i.e., 88.6% are alkaline while those of 10.5% are acidic and only 0.9% are neutral in nature. It is seen that only 4.5% samples have conductivity values with in the limit of drinking water range. Rest of the samples has high conductivity values. Of which 78.6% samples have the conductivity (cy) values of 0.5<cy!~1 .0 mS/cm and 15.0% samples have that of abnormally high values. The chloride values of the investigated 220 Tube-well (TW) water samples varied from 35.5 - 496.2 ppm. No health-based guideline value is proposed for chloride in drinkingwater. Chloride concentrations in excess of about 250 ppm can give rise to detectable taste inwater and not suitable for drinking. But the threshold depends upon the associated cations.Consumers can, however, become accustomed to concentrations in excess of 250pm. Only 10% samples have the chloride value beyond the mentioned value. In drinking water,iron is seldom found at concentrations greater than 10 ppm. 220 TW water samples havebeen investigated for the iron content and the results varied from 1.2 - 18.4ppm. No sample was found less than 0.3 ppm can cause water to turn a reddish brown color is the maximum permissible limit of iron for drinking purpose. Hardness is most commonly Expressed as milligrams of calcium carbonate equivalent per liter or ppm, water containing Less than 60 ppm generally being considered as soft. 220 1W water samples have been Investigated for the determination of hardness. The average value of hardness is 0.74 ppm. It is seen that the minimum value of hardness was found in Chandpur and Narayangonj Districts and the value is 0.2 ppm while that of the maximum is 2.6 ppm in Jessore. It is

-4- found that all the samples have hardness value with in drinking water range. 220 TW water samples have been investigated for the determination of dissolved oxygen. The average value of dissolved oxygen is 1.8 ppm. It is seen that the minimum value of dissolved oxygen was found in Narayangonj district and the value is 1.3 ppm while that of the maximum is 3.2 ppm in Chandpur district. The mentioned values of dissolved oxygen of the investigated samples are quite permissible for the drinking purpose. For As test, it is found that ARSOlux biosensor method is inexpensive, accurate, easy and simple. On the other hand Merck field test kit method is expensive, unreliable and environmentally problematic. Arsine gas is produced in Merck field test kit method is environmentally hazardous and carcinogenic. But there is no environmental threat in ARSOlux biosensor method. As test results by ARSOlux biosensor and ICP - MS methods are very close to each other. ICP - MS method is accurate and reliable but expensive and laboratory based while both ARSOlux biosensor method and Merck field test kit method are mobile techniques. No Effects of different water quality parameters on As test methods were unearthed