The science of wetlands and wastewater


At Oro Loma Sanitary District, Save The Bay is playing an active role in a restoration project that could provide a blueprint for climate change adaptation around the bay. Though it has a simple appearance, the horizontal levee is actually a complex system that can protect traditional levees from storm surges, provide habitat for vulnerable Bay Area flora and fauna, and reclaim the water that flows out of wastewater treatment plants. Traditionally, this nitrogen containing water would be pumped into the middle of the Bay and forgotten about, but the increased presence of algae in the Bay serves as a helpful reminder that we are failing to protect our ecological neighbors.

Rethinking wastewater

Certain chemicals that come out of our wastewater treatment plants can cause algal blooms at high enough concentrations, but we shouldn’t necessarily regard them as “contaminants.” These chemicals, various forms of nitrogen and phosphorus that are given the label “nutrients”, are the same ones that we use to fertilize our plants and crops. In the wrong place, they can throw off the ecological balance (read: algal blooms). However, if we divert these chemicals to terrestrial plant roots and microorganisms in the subsurface, we can provide plants with nutrients that are needed for growth while preventing those chemicals from making their way into aquatic environments where they can be troublesome. This process can kill two birds with one stone (metaphorically of course, as the levee provides important habitat for birds!)

This is the root of my interest in the restored habitat at Oro Loma. As a part of my research at UC Berkeley, I will monitor the horizontal levee to track chemicals in wastewater as they enter and leave the restored habitat. This is a large-scale experiment, testing to see if a restored habitat can thrive on the outflow from a wastewater treatment plant, as well as whether or not the habitat reduces the concentration of potentially dangerous chemicals that flow through it. By measuring the levels of these chemicals in the water, soil, and plants that the slope is made of, we will be able to understand better the chemical transformations that occur in the horizontal levee, many of which are performed by microorganisms.

Filtering chemicals

But I don’t plan to focus on only nitrogen and phosphorus. Many other chemicals that we put in or on our bodies, such as pharmaceuticals, antimicrobials, food additives and chemicals in personal care products, are collected in wastewater and pass through treatment plants largely unaffected. These chemicals form a group of chemicals known as “trace organic contaminants” many of which may pose threats to living things. The hope is that they will get filtered out of water that flows through the horizontal levee. If everything goes as planned, the slope should act as a sponge, absorbing the chemicals into “sticky” components of the slope, such as dead leaves, roots, and residues from microorganisms. Once absorbed, it is possible that microorganisms will naturally break these chemicals down into less harmful byproducts. Depending on the chemical, this process could be very effective or may do little to help, but these processes are not fully understood and require further study.

This is a fairly new concept and we can’t be certain of how effective it will be, but that is why we are testing it. Before we line the Bay with horizontal levees, we need to make sure we understand how they work. This is a promising new way to pair enhanced wastewater treatment with habitat restoration, and I am thrilled by the role I get to play in studying it!

– Aidan Cecchetti

IMG_1988_cAidan Cecchetti is a graduate student at UC Berkeley where he is working on his PhD in Environmental Engineering. Originally from northeastern United States, Aidan grew up wandering the forests of New Hampshire. After finishing his undergraduate degree at the University of New Hampshire in 2013, Aidan made his way to the Bay Area for graduate school and has been here ever since. In his free time, Aidan enjoys exploring the pockets of nature around the Bay Area, entertaining his cat or playing piano.