Joe Branca: Researching Bioretention Devices to Improve Water Quality

Meet Joe. Joe Branca is a student at Marquette University studying environmental engineering.

He and fellow Marquette student Camille Nitsche visit Green Tech Station as a field site for an ongoing experiment considering how the media in bioswales can be optimized to remove dissolved phosphorus and nitrogen from urban stormwater. This work is important because excess nutrients, which runs off the land from various sources including lawn fertilizer, can contribute to harmful algal blooms or other ecologically harmful effects in receiving waters. For us in Milwaukee, managing nutrients like phosphorus ultimately means a healthier Lake Michigan.

Marquette has built an array of “mesocosms” in sealed white plastic barrels containing mixtures of soil, sand, and compost—plus special amendments that retain moisture to increase microbial nitrogen update and coal slag to react with dissolved phosphorus. These barrels are housed at Green Tech Station next to the test plaza, where they are exposed to controlled amounts of “synthetic stormwater.” The barrels have sampling devices attached that allow the Marquette team to measure how well different mixtures perform.

The object of the experiment is to quantify the performance of the various mesocosms in order to inform the best designs for larger-scale systems like urban bioswales or other green infrastructure.

If a certain mixture is best at capturing and removing phosphorus from stormwater, for example, this would be good to know for engineers designing systems to meet water-quality goals like those in agreements known as TMDLs (water nerd jargon for total maximum daily loads). There is a TMDL for the Milwaukee River Basin that sets a limit for total phosphorus in the water. We know bioswales should help manage nutrient pollution, but Marquette’s research is important because it promises to quantify how a specific combination of factors makes a measurable difference with a contaminant of concern. The knowledge gained can help define different tools in the portfolio of strategies to meet water quality goals under the TMDL.

Joe has found the collaborative research at Green Tech Station inspiring and exciting. “I was thinking about doing urban planning or environmental engineering for my master’s,” Joe says. “This has further made me interested in this work and makes me want to create sites similar to this in the future and work with green infrastructure.”