Effectiveness of Household Water Treatment Technologies based on WHO Guidelines

Abstract

This thesis examines the bacteriological removal efficiency of different Household Water Treatment (HWT) technologies. Tests were conducted according to guidelines laid out by World Health Organization (WHO). Bacterial removal efficiencies of Ceramic Filters, Chlorination, Ultra-violet disinfection and Coagulation and Sedimentation were tested in a controlled environment by using two types of Test Water as per WHO requirement. Each of these options were tested using the two types of test water. The tests were conducted in the IUT Environmental Lab. E.Coli bacteria was used as the test organism to determine the removal efficiencies of these HWT methods before and after treating the test waters. Physicochemical parameters of the water samples were also measured along with the bacterial removal efficiencies. For all the methods of household water treatment systems, two types of test waters were used as per WHO guideline for household water treatment systems (HWTS) Ceramic Water Filters (CWF) have gained immense popularity over the recent years especially in developing countries. CWF implements porous ceramic and activated carbon to treat water at households. They have been identified as one of the most promising and accessible technologies for treating water at the household level. (Thomas F. Clasen). 8 filters of different companies were set up in the laboratory for control experiment to determine the efficiency of CWF in removing bacteria (E.Coli). A total of 1000 liters of water were passed and the bacteria removal efficiencies at 0%, 25%, 50%, 75% and 100% of water passage was measured. A total of at least 20 liters of water were passed per filter each day in order to replicate the water requirement of an average household size of approximately 5 people in Bangladesh. (Health Bulletin 2012). The physicochemical parameters of the water samples before and after filtration were recorded on a weekly basis. It was found that the effectiveness of the filters slowly declined with time. Laboratory results showed that after every cleaning process the efficiency of the filters increased. Chlorination is a chemical disinfection method that uses various types of chlorine or chlorinecontaining substances for the oxidation and disinfection of what will be the potable water source. Test waters were subjected to treatment by chlorination and it was found that this method had a v very high bacteria removal efficiency. Physicochemical data were also recorded for every experiment. A chlorine solution of 0.1N was used as the chemical disinfectant. Coagulation and sedimentation is the process in which a coagulant is added to water and mixed thoroughly to cause sedimentation. In this experiment 0.1N alum solution was used. The coagulant produces positive charges to neutralize the negative charges on the particles. Then the particles can stick together, forming larger particles which are more easily removed. Alum concentration was varied and for each concentration the bacteria removal was measured. For lower concentrations the removal efficiency was very poor but showed gradual improvement with increasing concentration. However the increased alum dosage rendered several unwanted physicochemical properties to the water which caused the water to lose its drinking water characteristics. Though this method yielded favorable results in removing bacteria, it showed unsatisfying results in physic-chemical studies. It was found that the dosage that is needed to remove E. coli completely from the sample water, creates acidic condition in the water. The pH level was found to be 3.85. So the method can’t be used to remove E. coli from water. Ultra Violet Radiation has been found to have disinfecting abilities and recent studies show that they may implemented as an effective method of disinfecting contaminated water. UV Water Purification systems use special lamps that emit UV light of a particular wavelength that have the ability, based on their length, to disrupt the DNA of micro-organisms. These UV light waves are also referred to as the Germicidal Spectrum or Frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). As water passes through a UV water treatment system, living organisms in water are exposed to UV light which attacks the genetic code of the microorganism and rearranges the DNA /RNA, eliminating the microorganism's ability to function and reproduce. According to studies it has been found that this process removes 99.99% of harmful microorganisms. From laboratory experiment it has been found that all the E. coli was removed from the sample water within 30 minutes for both type 1 and type 2 water. All the physic-chemical behavior was satisfactory. So the method can be used to remove E. coli in household level.