Features
Project Assesses Use of Reed Plants in Treating Waste
Alfred Campus researchers study reed bed filters for use in sewage treatment
BY ANDREW VOWLES
Call it a sewage treatment plant — with the emphasis on “plant.” At U of G's Alfred Campus, researchers are using reeds planted in a modified sandbox in hopes of yielding a cheaper and more efficient way to treat sewage for municipalities and other treatment operators.
Pending provincial regulation will ban the application of untreated septage (sludge from septic tanks) to agricultural land. Prof. Chris Kinsley says a reed bed filter offers promise for treating that waste.
He and other Alfred researchers are studying this technology with René Goulet Septic Tank Pumping, a private operator. The project is based at the company's waste-treatment site in Alexandria, about 45 minutes from the campus.
Two years ago, the researchers installed a lined pit about two metres deep filled with layers of gravel and sand and planted with reeds. Septic waste collected from area homes is pumped in and percolates through the pit. The idea is to separate liquid from solids.
Liquid percolating through the filter is pumped into the company's treatment lagoon and used to irrigate a poplar plantation that will eventually be harvested. Biosolids trapped in the filter could be applied to land as composted fertilizer.
Kinsley says the reed plants are vital to proper filtering. Sand alone serves as a natural filter, but it clogs up easily. Plant roots break apart the clogging layer of solids and create capillaries that allow water to drain. The plants also suck up water that ultimately evaporates from their leaves, helping to dry the biosolids in the waste material.
The reeds also pump oxygen into the root zone. That allows bacteria to grow and break down waste aerobically, preventing odours from anaerobic decomposition.
The researchers use common reeds that grow wild in wet areas in Ontario. Kinsley says plant scientists might be interested in testing various species to see which ones work better. He says it's important to let the reed plants establish themselves before beginning to dump in waste. The Alfred team had to replant during its first season.
Besides separating liquids and solids, the system “is actually treating the waste water,” says Kinsley. Water percolating to the bottom of the filters is already much cleaner when it arrives at the lagoon.
He says the system is intended as a pilot site to test the concept. If it works — if the system filters waste without clogging up and if it functions through Ontario winters — a municipality might adapt it for larger-scale treatment. He says land costs might be critical because the reed beds need sufficient space.
Kinsley is now designing a system to be installed in Algonquin Park next year. He expects to use that installation to generate research data for U of G.
Reed bed technology was developed in Denmark, where it's used to treat the excess bacteria and detritus that accumulate in municipal waste-water treatment facilities. The idea has spread to other countries, including France and Germany.
Kinsley says the systems cost less to build and maintain than conventional treatment plants. But researchers need to learn more about the kinds of questions he's investigating, including how much material the system can take at a time.
The reed bed is a form of built wetland, which has been a focus of research by Kinsley and Alfred colleague Anna Crolla for about 10 years. They have built and evaluated systems to treat municipal lagoon effluent, runoff from dairy operations, landfill leachate and mining waste streams.
Under a current project funded by the Association of Universities and Colleges of Canada, a pilot wetland system has been built in Morocco to study treatment and reuse applications in an arid climate.
Both Kinsley and Crolla belong to the U of G-based Ontario Rural Wastewater Centre.