 "Photo: Ed Troxell// STAR")
 "Photo: Ed Troxell// STAR")
Imagine algae with the incredible potential to give solutions to contemporary water treatment problems in the local area. Throughout the last month, SSU Assistant Professor of Biology Dr. Michael Cohen has been doing exactly that.
At the Laguna Treatment Plant in Santa Rosa, Dr. Cohen and one of his graduate students, Catherine Hare, have been investigating the potential use of algae to remove excess nutrients and other contaminants from urban wastewater runoff. These nutrients would otherwise support the unwanted growth of algae and other aquatic plants in the rivers and streams that receive such water runoff.
Now you're probably asking yourself…aren't having nutrients in water for the growth of algae and aquatic plant life a good thing for the environment? Well, Dr. Cohen has shown that it is not. Most of these nutrients come from the runoff of sewage and agricultural waste that lead into streams, rivers, and eventually coastal waters. This runoff water introduces large quantities of nitrate and phosphate plant nutrients, which can cause an explosive growth of harmful algae.
This process of hypoxia takes credit for about 43 oxygen-depleted zones around the United States alone. It damages fisheries and kills off oxygen-consuming fish and bottom dwellers. The low oxygen levels are caused by the rapid growth of algae in nutrient-rich waters followed by their eventual decomposition by growing colonies of oxygen-consuming bacteria. Furthermore, the overgrowth of aquatic plants also creates numerous areas of stagnant water, which increases the mosquito population.
Plants and algae remove nitrogen and phosphorus from the surrounding water as they grow. This is the basic idea behind the project which consists of two parallel polishers (channels) full of mats of different algae and a tiny duckweed plants. Each has its own controlled inflow of an already treated supply of water that stills carries levels of unwanted nutrients.
"As the water flows through the channels," said Dr. Cohen, "the excess nutrients are absorbed by the mats, which need to be harvested daily to keep the rate of nutrient absorption at a steady rate."
A major goal of the experiment is to determine flow rates that will achieve desired nutrient reduction. With analytical assistance from Nels Woldren, a technician in the Department of Chemistry, Dr. Cohen's lab found that a smaller pilot system at SSU was able to lower nutrient concentrations by as much as 97 percent.
"Catherine and I are very grateful for the help Nels provided," said Dr. Cohen.
When the water exits the polishers, it is pumped back into the treatment plant's water storage. It is only released back into the Russian River during the winter and at 5 percent of the rivers existing water flow.
This process of dilution has shown significant progress so far. The algae harvested from the polishers serves further purpose as well. After harvest, it is put into onsite digesters, and the methane byproduct that the algae produces is collected and used to power the treatment plant.
Looking even further into the future, there is a lot of literature that suggests the very real possibility of extracting algal oils prior to feeding it to the digesters to produce biodiesel. The economic viability of this technology will be determined through further research.
The North Coast Regional Water Quality Control Board has raised the bar for Sonoma County. Dr. Cohen has stepped in with his project and data and hopes to give the city some solutions.
The mid-sized experimental project, built by R.S. Duckworth Construction of Sebastopol, was designed to provide data to assess the economic viability of building a full-scale working version.
This project does more than filter wastewater; it gives hope that renewable energy can provide a future for an environment that has been abused, and may ensure our health for generations to come.
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