A new tool to protect marine environments from wastewater nutrients
April 06, 2022
The POINT tool is a quick way to begin planning for the right nutrient-removal technology
Nitrogen is, quite literally, in the air we breathe. In fact, it¡¯s most of what we breathe¡ª78%.
It is one of the most abundant chemicals on the planet and one of the key elements in the chemistry of all living creatures. Nitrogen is part of amino acids, which are the building blocks of proteins. Through nitrogen fixation, microbes convert it into ammonia for plants.
It¡¯s essential to life. But it can also be a problem, especially when too much of it gets into our water.
It¡¯s particularly troubling in the Pacific Northwest, where we live. The marine and estuarine waters of Puget Sound are as iconic to the region as Seattle¡¯s Space Needle or Mount Rainier. They are, however, experiencing areas of low oxygen levels that has been linked to the decline of marine species within the Sound¡ªfrom mussels to salmon to killer whales.
Washington¡¯s scenic Puget Sound. The Washington State Department of Ecology recently implemented new regulatory changes impacting many of the wastewater treatment plants in the region.?
But clean water isn¡¯t just about marine species. It¡¯s about people, too.
And it¡¯s not only a problem in Puget Sound¡ªand it¡¯s not always just about nitrogen. Wastewater treatment plants (WWTP) release ¡°clean¡± effluent into water bodies¡ªlakes, rivers, or oceans¡ªall around the world. However, just how clean is clean? In Nevada, excess phosphorus is a huge issue for Lake Mead. News of algae blooms is nothing new.
The bottom line? There is a need to remove macronutrients of nitrogen, phosphorus, and other inorganic and organic substances from our treated discharged wastewater. More stringent regulations require it.
But how? Creative solutions for local wastewater utilities are essential. We need to understand what¡¯s happening after the treated wastewater is discharged. And we need a quick way to start the process of picking our next generation of treatment.
Understanding the science of our receiving water
WWTPs are not the only contributors of excessive nutrients to water bodies. Fertilizers used on farms often end up washing into nearby waterways. There is runoff from your lawn, pet waste, and other pollutants. Ultimately, we see eutrophication¡ªwhen the water is enriched with nutrients.
Eutrophication sets off a chain reaction in the ecosystem. It starts with an overabundance of algae and creates low-oxygen (hypoxic) waters that can kill fish and seagrass. The National Oceanic and Atmospheric Administration estimates that 65% of the estuaries and coastal waters in the contiguous US are moderately to severely degraded.?
An example output from the Â鶹´«Ã½-design POINT tool. The 3-D curve illustrates performance of a typical nutrient removal process, the flat plane shows a potential effluent TIN permit limit, and the black dot indicates data from a wastewater treatment plant. That data includes plant effluent TIN (total inorganic nitrogen), the SRT (solids retention time), and influent COD:N (carbon to nitrogen ratio).
That means we end up with coastal waters they can¡¯t support plant life, fish habitats, bivalves, and fish. In Puget Sound, that impacts killer whales and other marine life.
So, how can we help? Addressing nutrient and dissolved oxygen challenges in the Puget Sound¡ªand elsewhere¡ªrequires creative solutions of both time tested and emerging strategies for nutrient removal and recovery.
As we mentioned, it¡¯s not all about wastewater treatment. But that¡¯s one of the best places to start. The treatment plants are a known contributor of nutrients to water bodies. We can easily identify where the outfalls are, so it¡¯s a great place to start.
A new tool to help speed the process
As our population grows, we simply have more wastewater to process. We can¡¯t keep doing it as we¡¯ve always done it before. In addition to more people and more waste, we have the impacts of climate change. It¡¯s a worrisome combination for our waters.
We know nutrient removal from wastewater is one way to help protect Puget Sound. It¡¯s believed to be so important that the Washington State Department of Ecology recently implemented new regulatory changes impacting many of the WWTPs in the region. What may be less known is how different treatment strategies can improve the performance of WWTPs.
The challenge facing us is multifaceted:
- Most WWTP facilities are not designed for nutrient removal
- Operators and regulators are often unfamiliar with the nutrient-removal technology options
- Utilities face limited financial resources to implement the technologies
- Too often, technology selection is complicated
But there is a quick and easy solution.
The Â鶹´«Ã½-designed Process Optimization and Identification for Nutrient Treatment (POINT) tool can quickly help WWTP owners and operators visualize what their discharge looks like today and how various treatment options can change it. The tool was developed by Â鶹´«Ã½¡¯s Institute for Water Technology & Policy.
It basically POINTs owners and operators in the right direction.
Since technology selection can be complicated¡ªand it¡¯s a multimillion-dollar decision¡ªthe POINT tool helps take the guesswork out of it. And it comes with minimal time and financial investment.
As our population grows, we simply have more wastewater to process. We can¡¯t keep doing it as we¡¯ve always done it before.
The POINT tool is designed as a starting place for utility operators and plant managers. Currently, the tool can compare four nutrient-removal options, essentially eliminating those that are ineffective or expensive overkill for what¡¯s needed at a facility.
A quick analysis starts with understanding each plant¡¯s influent characteristics, including total suspended solids, chemical oxygen demand, nitrogen concentration, and other characteristics. Add a little more information about the plant¡¯s current biological system, solids retention time, and effluent inorganic nitrogen. Then you can let the POINT tool do the work.
Using the four nutrient-removal processes, we get the information on which is likely the most appropriate solution for each plant. In this case, our goal is to help the 58 domestic WWTPs discharging to marine and estuarine waters of Puget Sound to meet the Puget Sound Nutrient General Permit requirements.
Excess nutrients¡ªor eutrophication¡ªsets off a chain reaction in marine ecosystems. The National Oceanic and Atmospheric Administration estimates that 65% of the estuaries and coastal waters in the contiguous US are moderately to severely degraded.?
Finding the right solution to reduce nutrient troubles
Strategic investments in nutrient removal should be grounded in a thorough understanding of existing wastewater characteristics and plant performance. They must maximize the return on ratepayer investment in existing infrastructure.
Where additional or enhanced treatment capacity is required, improvements must provide robust process performance, reliable compliance, and flexibility to respond to an evolving regulatory and economic landscape. The solution for each utility will be unique, but the path to reaching the solution includes the common steps of assessment, optimization, expansion, and innovation.
With the right information¡ªaided by the new POINT tool¡ªwe¡¯re in a better position to help wastewater clients here in the Pacific Northwest. But it can also help clients on the other side of the continent and across the globe.
That makes the planet a better place for orcas, salmon, and everyone else as well.?