TN and TP: How Low is Low and How Do We Get There?

Nutrient removal is a critical issue throughout the world, and is being globally evaluated to protect waters of beneficial use. Excess nutrients can lead to an increase in algal growth in surface water bodies and subsequently damage aquatic life. In the United States, Section 304 (a) of the United State Environmental Protection Agency (USEPA) Clean Water Act (CWA) lists recommended nutrient removal criteria for 14 different ecoregions. Each of these ecoregions has different water quality standards for Total Nitrogen (TN) and Total Phosphorus (TP), and each are becoming more stringent over time. Utilities across the United States are looking to various membrane technologies to enhance nutrient removal through their treatment process. In Miami-Dade County, Florida, a pilot plant is using multiple membrane technologies to test the removal of nutrients prior to discharge into a wetlands environment. In Las Vegas, Nevada, another pilot plant is evaluating the removal of nutrients through membrane filtration and chemical addition to enhance nutrient removal prior to being used for non-potable uses such as irrigation. In Australia, the removal of nutrients in recycled water plants located near an ocean is generally not an issue, however at recycled water plants located inland discharging into estuaries or rivers, nutrients are a critical issue as they drive algal blooms leading to eutrophication. Case studies at two plants have shown that phosphorus is driving the design of the plant. The objective of this paper and presentation is to present an overview of these plants and to compare the removal efficiencies of nutrients through different membrane plant configurations.This presentation shares a technical solution to meeting increasingly stringent nutrient requirements through the use of multiple membrane technologies. The resulting solution may take on a different shape depending on other factors such as economics, carbon footprint, and public acceptance. Although limited to the evaluation of pilot plants located in the United States and full scale operations in Australia, the identification of baseline information can be shared and applied to projects throughout the world. Additionally, this information can be applied globally by comparing the nutrient removal criteria by region as set forth by the USEPA and the Queensland EPA to similar ecoregions around the world.