Paper Title
Estimation of Organic Matter Content in Drinking Water Sources; Assuming Humic Acid as the Predominant Species of Organic Matter in Water

Natural Organic matter (NOM) is a complex matrix of organic compounds present in natural surface water sources (Mahvi et al., 2009). Humic substances (HS) are the predominant type of natural organic matter (Richard et. al., 2009). Not only HS affect the odour, colour and taste of water but also affects several processes in drinking water treatment as such as biofouling, increasing chlorine demand etc. (Aoustin et al., 2001). Halogenated HS during water treatment are collectively referred to as disinfection by products (Kurt et al, 2013). HS cause formation of disinfection by products (DBPs) such as chloroform, bromo-dichloromethane, etc., which are suspected carcinogenic compounds (Yildiz, et al., 2008). For this reason, the USEPA currently regulates two classes of DBPs commonly found on drinking water – trihalomethanes (THMs) and halo acetic acids (USEPA, 2009). As the HS predominates in NOM, HS can be used to determine the concentrations of NOM. Still, National Water Supply and Drainage Board does not have a reliable method to measure the concentrations of NOM in water, in its regional laboratories. Therefore, the amount of organic matter entering the drinking water treatment plant is unrevealed. The objective of this study is to quantify the NOM in natural drinking water sources, using available laboratory facilities. Standard solutions of HS were prepared using the commercially available Humic acid powder (Sigma Aldridge brand). A graph was obtained by scanning the samples, against series of wave lengths from 990 to 1100 nm, Using the DR 5000 spectrophotometer. Then the wave length range was filtered to 230 nm to 630 nm, as the absorbance at the other wave lengths were not given considerable variations. The results obtained were used to construct a graph of Absorbance Vs Wave length and it was used to estimate the concentrations of HS in unknown samples. The highest concentration of HS sample has widest absorbance range, while the least concentration has the narrowest curve. Using the results obtained from graph of absorbance Vs Wave length the concentration of HS in the Doluwa water could be estimated. The graph of absorbance Vs Wave length can be used as a reliable method to estimate the Organic matter content in water samples. All the raw water samples measured during the three months period of time (from August to October – 2018), collected from 13 locations of Kandy South region (39 samples), contained organic matter content of less than 0.1 mg/L, which means water sources are less contaminated and still far away from the danger of DBPs. Keywords - Natural Organic matter, Humic acid, Disinfection by products