In this thesis a mathematical model for accumulation of disinfection by-products is established. The model concerns combined chlorine, which has nitrogenous compounds as precursors. The model is based on knowledge gained by a literature review.

The validity of the model is tested using three sets of data. These tests show that the model is not in totally agreement with reality. However, the tendency of the curve for formation and removal of disinfection by-products is similar to those found in reality. For this reason the model is used for simulation of the effect of source water on the quality of pool water.

Three simulations are made. First the effect of ammonia from source water on the concentration of combined chlorine in pool water is studied. This simulation shows that source water does not affect the concentration of combined chlorine in pool water. The second simulation is focusing on calcium and carbonate species in the source water and shows that the source water alone is not enough to cause supersaturated pool water. Carbon dioxide is formed in the pool during breakdown of urea. The results of the final simulation show that this carbon dioxide does affect the saturation of pool water and for hard water may cause supersaturation.