Development of a software for the design of stripping towers to remove trihalomethanes from disinfected water

Abstract

The aim of this project is to develop a software (called STRIP) able to design how an stripping tower should be to remove components dissolved in a liquid. In special, after analysing technical and environmental sustainable alternatives, the aim is focused on removing trihalomethanes (THMs) from water putting the flow in contact with air along a stripping tower. Consequently, the idea is to reduce the potential carcinogenic risk associated to the THMs formed in the water after a disinfection process. Accordingly to input parameters such as the initial and final concentrations and the flow desired to treat, STRIP calculates the most efficient features of the system to carry on the operation ensuring its correct performance. The software code is developed by Matlab as it is programming language widely used and known by scientists and engineers. Therefore, a wide range of different topics are integrated in this project: from the calculation of the efficient size and features of the stripping tower depending on the input data to the study of legislation and cancer risk rates in order to analyse the effects of THMs on the potential consumers: humans. After the complex methodology carried on, STRIP provides different information as results: On one hand, the indispensable values regarding on the stripping tower: its height, diameter, the best type of fillings, an approach of the investment required... plus the potential cancer risk of the water before and after its installation. On the other hand, it shows graphical representations of the equilibrium of the stripping system and the resistance of the liquid and gas streams against the mass transfer. In addition, a text file is created in the same folder where the software is executed with more detailed values: flows velocities, individual and overall mass transfer coefficients, molar fractions on the top and the bottom of the tower, features of the filling selected... Finally, once STRIP is validated and checked it gets the best theoretical solution, it is purposed several proper applications for the stripping towers to remove THMs. Basically, using information from 2 different Drinking Water Treatment Plants (DWTPs) located in Spain and one city of Venezuela, it is studied the possibility to install a stripping tower in a certain point between the water disinfection treatment and the final users consumption point. In order to analyse the viability, health carcinogenic indexes are related with economical costs of the installation and the population to who the quality water is supplied to estimate how much costs to save a human life in each scenario.