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The growing problem of wastewater in oceans and coastal habitats

The growing problem of wastewater in oceans and coastal habitats

Researchers at World Water Week 2021 discuss the link between ocean health and wastewater.
 
When wastewater enters watersheds and coastal habitats, it can cause significant changes in ecosystems that harm the health and livelihoods of communities. At World Water Week 2021, scientists shared their latest research, and organizations discussed how they are addressing the problem. Xylem’s Dr. Lindsay Birt shared results from a pilot project at a wastewater treatment plant that showed digital solutions had the potential to reduce nitrogen in effluent by 30 percent.
 
The wide-ranging problems caused by wastewater in coastal habitats were discussed by Dr. Stephanie Wear, Senior Scientist & Strategy Advisor at The Nature Conservancy. Her organization is part of the newly formed Ocean Sewage Alliance, made up of organizations and academic scientists focused on reducing the threat of sewage and other wastewater pollution in oceans.
 
“An estimated 80 percent of our global wastewater is discharged untreated into the environment,” she said during her presentation. “The assumption has been, not surprisingly, that the ocean can handle it, that in fact the ocean can treat the wastewater. Let me be very clear that our oceans and our environment in general cannot handle it, and in fact have been very severely impacted by it.”
 
Even when wastewater is treated, Wear says, ecosystems and communities are still affected by overflows caused by storms and through insufficient treatment of wastewater.
 
“Many cities have been designed to combine stormwater and sewer water, so that rain events don’t overwhelm treatment plants,” she said. “Ultimately this results in the discharge of tens of trillions of gallons of sewage and stormwater into the ocean every year.”

Wear presented an overview of some of the impacts and mechanisms that are leading to decline in key coastal habitats and fisheries, which billions of people depend on for food.
 
“Recent science has shown us that coastal fish populations are extremely vulnerable to pollution,” she said. “Deformities are being found in the tissues of juvenile fish living near tertiary sewage treatment plants. They are actually getting contaminated from treated water.”

Mapping wastewater discharge to oceans

Dr. Benjamin Halpern, Director of the UCSB National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara, shared the results of a recent study that created a model of how wastewater is discharged into oceans around the world.

“Wastewater can come from multiple different sources,” he said during his presentation. “It can be treated sewage from wastewater systems, it can be in septic systems or tanks and pits, or it can be direct input into the system. Understanding these sources is really important for understanding the pathways to solving the problem and mitigating the input from wastewater nitrogen into coastal waters.”
 
Excess levels of nitrogen in groundwater can cause health problems when it is used for drinking, and in waterways it can cause harmful algal blooms that impact recreation, tourism, human health and fisheries.
 
“The first highlight result is that wastewater nitrogen is about 40 percent of the amount being put into coastal waters from agriculture, livestock, and manure,” he said. “Agriculture nitrogen runoff gets lots of attention, but the problem of wastewater is on equal magnitude and is something we definitely need to be paying attention to.”
 
The model created in the study, based on many different data inputs, found that about 37 percent of wastewater input globally is coming from septic and direct input, with 63 percent coming from sewer systems.
 
“In many countries, nearly 100% is coming from septic and direct systems,” he said. “Thinking about solutions for these countries is going to be very different than those that are primarily on sewer systems.”

Using digital twins to improve the health of Europe’s oceans

Dr. Lindsay Birt, Client Solutions Manager for Xylem's Decision Intelligence Solutions, presented how new technology can help reduce nitrogen in effluent and decrease energy consumption at wastewater treatment plants. A pilot study conducted by Xylem, a global charitable foundation, and a coastal water utility in Northern Europe, used digital twins and predictive analytics to help optimize the utility’s wastewater collection and treatment.
 
“A digital twin is a digital replica of a device or product that can be modeled to use in simulation or prediction of behavior,” she said during her presentation. “Digital twins can represent assets from the physical world and the digital world. Digital twins can empower wastewater system operators to make data-informed decisions and prioritize actions that matter most to the communities they serve – environmental sustainability, resilience, and ocean health.”

Using “Sense, Predict, Act” to make informed decisions

The project used the approach of sense, predict and act. In the sense phase, a broad spectrum of data – including historical data, sensor data, and data about weather patterns – is brought together in one centralized platform. In the predict phase, the data is analyzed using digital twins of the collection and treatment systems. Thousands of simulations are run using machine learning.
 
In the act phase, the operator is guided by recommendations from the digital twins to optimize processes. These include recommendations about how to best use available wastewater collection storage, and recommendations about the optimal aeration needed during treatment.

Reducing nitrogen in effluent by optimizing flows and processes

The pilot study found that when hydraulic peak flows into the wastewater treatment plant are reduced, by storing collection system flows, and when aeration at the wastewater treatment plant is reduced, based on predictive analytics, total nitrogen loads in the effluent can be reduced.
 
“At the coastal utility in northern Europe, we saw some really amazing results,” Dr. Birt said. “By leveraging digital twins in the wastewater collection and treatment systems, we were able to demonstrate potential reductions of nitrogen in the effluent by 30 percent and reductions in aeration energy usage by 17.5 percent.
 
“Our team envisions a world where utilities are empowered to make decisions on nutrient management that achieves both economic and environmental benefits, receiving oceans show significant water quality improvements, and all people can live in a healthier ecosystem,” she said. “This will transform utilities and how they manage and operate the maintenance of their wastewater networks.”
 
Learn more about Xylem's digital solutions platform: Xylem Vue.

Watch the presentation about the digital twins project