A SURVEY OF DISINFECTION BY-PRODUCTS IN TAP WATER FROM SELECTED AREAS IN NAIROBI COUNTY AND THIKA SUB-COUNTY, KENYA

Abstract

Over 1.1 billion people in the world lack access to potable water. Diarrheal and other waterborne diseases cause an estimated 2.2 million deaths per year. To curb these diseases, chlorination is a proven water treatment method. Concerns have been raised about the potential long term health effects of formation of disinfection by-products to users of chlorinated water. These by-products have limits of which they should not exceed. This study investigated the production of trihalomethanes (THMs) in chlorinated tap water from selected areas in Nairobi County and Thika Sub-County, Kenya. Water samples were directly collected from the taps, and taken to KEBS for analysis of THMs using Gas Chromatography-Electron Capture Detector. Data obtained was subjected to Microsoft Excel and analysis of variance. Water samples from Kawangware Estate, Technical University College of Kenya and Hurlingham had some significant amount of chloroforrm; 7.4µg/L with SD of 1.0, 5.3 ±3.0 and 15 ±4.0 (µg/L) respectively. Water samples from Technical University College of Kenya, Karura Forest, Catholic University of Eastern Africa, Kawangware Estate and Hurlingham showed traces of dibromochloromethane as follows: 6.5, 5.6, 3.7, 5.3, 7.1 (µg/L) respectively with SD ranging from 0.1 to 1.1. The studyinvestigated how pH, Temp, Turbidity and DOC affects the formation of THMs in chlorinated water. The results showed that THMs concentration was high in samples with high values of pH, Temp, DOC and Turbidity. A narrow range of turbidity (4.5–4.9 NTU) and DOC (1.0–2.3 µg/L) was recorded. SD for turbidity in water samples ranged from 0.03-0.07 and 0.04-0.26 for DOC. The data presented herein clearly show that chlorination of filtered waters does not lead to THMs concentrations above the WHO guideline values. Therefore, proper chlorine disinfection in municipal and borehole water in Kenya is recommended.