Statistical modeling for iodinated trihalomethanes: Preformed chloramination versus prechlorination followed by ammonia addition.

Developing predictive models for iodo-trihalomethane (I-THM) formation in water is needed and valuable to minimize extensive and costly analysis. The main objective of this study was to develop a statistical model for the formation of six types of I-THMs under uniform formation conditions. Prediction of I-THM formation in two different water sources (natural organic matter [NOM] and algal organic matter [AOM]) were comprehensively evaluated during both preformed chloramination and prechlorination followed by ammonia addition conditions. In addition, the prediction of THM10 (sum of six I-THM and THM4) formation was conducted during both oxidation strategies for NOM waters. In total, 460 experimental results were compiled from the literature and our own database. The results showed the coefficient of determination (R) values for the six I-THM species ranged between 0.53-0.68 and 0.35-0.79 in the preformed NHCl and perchlorinated NOM waters, respectively. Among all independent variables, the I exhibited the most significant influence on the formation of all I-THM species in the preformed NHCl, while SUVA was the most influential parameter for perchlorinated NOM water. When the preformed chloramination was compared with prechlorination followed by ammonia addition, the R value for I-THMs (0.93) was higher than for THM4 formation (0.79) in preformed chloramination. In the prechlorination followed by ammonia addition condition, the model prediction of I-THMs (R 0.45) formation was lower than THM4 (R 0.96). Overall, the pH, I, SUVA, and oxidant type are all played crucial roles in determining the I-THM formation, impacting the overall effectiveness and predictability of the models.