Water reuse model development and application

Abstract

Supporting the water demand for various water users, in the growing world is a big challenge in many parts of the world, especially in arid and semi-arid regions. To address this problem different techniques are being investigated and practiced. Reuse of treated wastewater for agriculture is one of these techniques that is considered in many countries. However, reuse of treated wastewater for irrigation can be challenging and many factors should be considered in any reuse project. Water reuse effects on soil salinity, crop yield, and environment (pollution of ground water and surface water) are some of the important factors that should be considered. A new user-friendly mathematical model was developed in VB.NET to address some of the challenges of reuse of treated wastewater. The new model is developed for comparison of various scenarios of water reuse, in aspects such as crop yield, surface and groundwater pollution due to phosphorus and nitrogen, as well as water conveyance and pumping requirements. This model is composed of three sub-models: the first sub-model calculates the daily water and salt balance considering factors such as irrigation and rainfall, deep percolation, runoff, groundwater contribution and ponded water based on irrigation method and crop yield. The second sub-model calculates the nitrogen and phosphorus balance in the root zone area. The third sub-model estimates the pumping and conveyance requirements based on the land topography. The feasibilities of various water reuse projects in Cache County, Utah were studied, using this new model. The details of the model, input and output data as well as the results from the case study in Utah and how they could benefit the user, are described in this study. The model described herein is a useful and convenient tool to help decision makers analyze various aspects of reuse of treated wastewater. An important conclusion from the results analysis of the model is, even though reuse of treated wastewater for irrigation and uptake of nutrients by the crops could result in less water pollution, without good management a large amount of nutrients will be released into the surface waters