Variation of chemical species in infiltrating treated sewage water using the multi-component solute transport model

Due to uncertainties raised about the presence of contaminants from recycled water it is necessary to identify the chemicals likely to be present in treated sewage water, and assess approaches for minimizing their release. The relevant physical, chemical and biochemical processes must be understood in order to determine the state and movement of contaminants. To simulate the mechanisms responsible for the movement of chemical species, predictive tools in the form of mathematical models have been developed. This study deals with the processes and chemical transport in an aqueous soil similar to paddy fields where successive reduction reactions occur. To examine the behaviour of the different chemical species present in the secondary treated sewage water, a two-soil column experiment was conducted. In order to more fully understand chemical and biochemical processes, a solute transport model that takes into consideration the biochemical reactions and cation exchange reactions was developed in this study. The soil column experiment and the solute transport model produced interesting observations on the behaviour of different chemical species. The observed concentrations correlated fairly well with the simulated concentrations and the sequence of reduction reactions were reproduced by the developed solute transport model.