Sulfate, Chloride and TDS: The IRP Challenge for the 21st Century

TDS and specific common ions such as chloride and sulfate are now being regulated. These pollutants have been forgotten over the last 20 years. Since TDS became a secondary Maximum Contaminant Level (MCL) for drinking water, several states have adopted the MCL concentration as a water quality standard.TDS removal is expensive and, unless an ocean is nearby, so is brine disposal. Finding a low cost way to control TDS is the goal; evaluating the alternatives to find the low cost approach will cross many discipline boundaries. Is TDS control a water resource issue, a water plant issue, an industrial pretreatment program issue or a wastewater plant issue? Where does the low-cost alternative lie? Is it a combination of techniques from the various areas of concern?The only way to determine the best approach to TDS control is to use Integrated Resource Planning (IRP) as an evaluation tool. TDS control is directly related to water supply, water quality and water reuse. Build an area mass and water balance to use as a tool in evaluating options. Develop a long-term plan for TDS control. The City or the controlling agency may have to make ordinance changes to accommodate the TDS control plan. Update the plan periodically and establish funding mechanisms for TDS control.There are many possible ways to approach TDS control. Keep an open mind and use the mass balance to demonstrate the feasibility and the size of effort. Determine the cost of each alternative and compare alternatives on a cost basis, flexibility, sensitivity, impacts from adverse weather, and long term life of the alternative.