5 Unusual Examples of Biofiltration

Biofilters are a simple and efficient way to control pollution. From the air to water supply, living natural matter is used to remove toxins and ensure the output of a safe, usable resource. But biofiltration is a varied science and sometimes it is applied in unusual and surprising ways…

1. Seaweed and fish tanks

Weeds are typically seen as pests. But seaweed has a significant role to play when it comes to aquaculture - by filtering out pollutants emitted via brachial excretion from the gills of fish and other underwater animals. Each plant targets a specific pollutant - for example red seaweed, known as Gracilaria Heteroclada, successfully filters nitrogen, while sea lettuce removes ammonia. These biofilters are often found in fish tanks and require oxygen to work.

2. Peat and manure storage

One thing’s for sure - farming facilities can produce some foul smells, especially where livestock such as cows and pigs are concerned. Biofilters containing media such as peat and wood chippings are used to reduce odour, as well as harmful gases such as hydrogen sulfide, ammonia and methane. These filters are then placed on barns or manure storage facilities. Reduced smells is a big benefit, but some less obvious advantages include a reduction in the spread of airborne viruses and less greenhouse gas emission.

3. Plant roots and wastewater

According to horticulturalists at Penn State University, plant roots in combination with soil and crushed limestone can create a biofilter to turn wastewater into a usable resource. Using two long plastic corrugated pipes, they reduced the levels of boron from washing machine wastewater by 92% - with similar reductions seen in other pollutants over a two to three-day period. While boron is, in fact, useful to growing plants, it is toxic in high levels - so this process allows wastewater to be safely used on vegetable patches and flower beds. During the biofiltration, bacterial colonies found among the plant roots eat dissolved organic matter, and by replacing the plants on a periodic basis, trapped pollutants could also be removed.

4. Biofiltration and septic tanks

If your property is not connected to a mains sewerage system, you’ll have a septic tank to deal with waste. A biofilter can be used to reduce the size of your leach field or to eliminate it entirely. It reduces the risk of flooding and stops unpleasant smells. It’s also kinder to the soil, because the resulting water quality meets the required standards.

5. Oysters

Believe it or not, oysters filter out pollution by filtering sediment and toxins out of the water. This is why New York City is currently trying to re-populate local water with oysters. It will be 2050 before the oysters are safe to eat — but this is another example of turning to nature to mend the damage caused by man. For more information on this fascinating topic, read: Cleaning up with Oysters? The Story NYC’s Unlikely Saviour.