Computational fluid dynamics aided optimisation of liquid state antiseptic injection to water networks

Waterworks mostly use chlorine as an antiseptic substance. It can be added in gaseous or liquid form. The simplest technique is to use gaseous injection but it carries the most risk as chlorine gas is highly toxic. Therefore, the current trend is to switch to the much safer hypo doser technology, whereby the hypo is injected into the water pipes with injector tubes, similarly to chlorination but the mixing of the antiseptic liquid is more problematic. Correct placement of the inlet and measurement points is indispensable. With the help of the computational fluid dynamic (CFD) simulation not only can the flow of the specific water pipe be modelled but also mixing of the antiseptic fluid can be modelled, thereby the measurement and inlet points can be installed at the optimal locations. In very short pipe sections with a limited amount of pipe length to achieve proper mixing the use of static mixers was suggested. Efficiency of the static mixers is variable and they increase the pressure loss on the specific water pipe section, which inflicts additional energy costs. With the help of CFD modelling, the fluid dynamic phenomena (vortices, backflows, etc.) on these pipe sections can be utilised to help mixing of the antiseptic substance meaning the use of static mixers can be avoided.