Water For People, Water for Plants: Engineers Keep the Taps Flowing

By Tamara Kamis
Monday, July 11, 2022

Many at Shoals Marine Laboratory ran inside when rain began to pelt the island, but not the sustainability engineering interns; they rushed outdoors to see the Celia Thaxter’s Garden rainwater collection system working in real-time.  

Shoals Marine Lab is located on Appledore Island, 10 miles from the Market Street dock in Portsmouth, New Hampshire. Surrounded by the salty ocean, maintaining a freshwater supply is a major concern for this remote field station. Current strategies in place at Shoals Marine Lab include using rainwater to irrigate the historic Celia Thaxter’s Garden and encouraging people to conserve water in their daily lives. Sustainable Engineering Interns Zach Katz, Izzy Medeiros, Jason Shao, and Tess Hays are working at the lab this summer to help better conserve the island’s fresh water supply while protecting the environment.  

The interns are assembling a comprehensive picture of the materials used in every component of the lab’s drinking water system, which draws on both a freshwater well and a reverse osmosis machine that turns seawater into freshwater. They are guided by the expertise of the island’s engineers and University of New Hampshire Civil and Environmental Engineering professor Dr. Weiwei Mo, who taught the interns how to conduct life cycle analysis.  

“When you look at whether something is sustainable, you may just look at its current use and come to the conclusion that it is sustainable,” Shao said. “Really, you have to look at a system’s sustainability throughout all of its phases, including manufacturing, transport and disposal, which people often overlook.” 

The interns are creating an assessment of the drinking water system life cycle. Their recommendations may help the island engineers to make decisions when they repair or replace components of the island’s drinking water system in the future. 

“If we find out that a certain type of pipe requires an incredible amount of carbon emissions to make it and transport it here, we can recommend that if you have to replace this pipe, maybe replace it with something else,” Hays said. 

The island’s reverse osmosis system is one component of the drinking water system that the interns are particularly interested in better understanding. It makes fresh water out of seawater. When the island is sunny and windy, the solar and wind energy systems at Shoals Marine Lab sometimes produce more energy than the island residents need. It is at these times that the reverse osmosis machine is turned on; it produces fresh water while keeping energy from going to waste. 

“They can generate more fresh water at times where even though that might not be needed, it can be stored,” Hays said. “On cloudy days when we haven't had a lot of rainfall and the well itself is low, we can have that fresh water without needing to run the diesel generator to produce it.” 

Around the world, experts are realizing the necessity of developing strategies to store renewable energy. The use of excess renewable energy to run reverse osmosis machines would be a promising strategy for other institutions to learn from, if the life cycle analysis supports this recommendation. 

Due to the limited supply of well water on Appledore Island and the energy intensive nature of reverse osmosis, Celia Thaxter’s Garden is partially irrigated with collected rainwater. The interns are working to improve the rainwater collection system, further ensuring that even if a future summer is drier than normal, the garden will have enough water. 

By watching the rainwater collection system in action, the interns brainstormed ways to improve its efficacy. While the system for transporting water to the garden works well, the rainwater storage system – which collects rainwater – does not capture heavy rain as well as it could. The interns discussed the rainwater collection system with Tufts Civil and Environmental Engineering professor John Durant, who helped them think through their design process. 

They also learned more about the garden’s operations from Terry Cook, the Shoals Marine Lab Garden Steward. 

“I think it’s interesting that we can harness water to irrigate the garden in a more controlled way,” Medeiros said.