Bacteria and worms filter water?!

Brown Swiss and Jersey dairy cows. (Photo taken in Oxapampa, Peru, by P. Froese.)

Two weeks ago, the Union-Bulletin of Walla Walla, Washington, reported a recent partnership between Organix Inc., a local organic waste management company, and BioFiltro, a Chilean firm. Organix will be the local distributor of the proprietary BIDA® organic wastewater filtration system sold by BioFiltro.

I became intrigued as I looked more closely at BioFiltro’s BIDA® filter, and thought I would share this (unaffiliated) short post about it.

How it works

The innovative BIDA® wastewater filtration system consists of an open-topped concrete tank filled with layers of earthworm humus, sawdust, and gravel. (This YouTube video explains it nicely.) The humus, sawdust, and gravel matrix supports a teeming society of earthworms and bacteria—the filter’s active agents.

Screened wastewater is sprayed over the top of the tank, and as it percolates through, the bacteria, in synergy with the earthworms, remove nitrogen and phosphorous contaminants. The filter also catches suspended solids, oil, and grease, which feed both bacteria and worms. Four hours later, water leaving the filter is ready to be applied to crops again. The byproduct, rich organic humus, is a high-value organic soil amendment and source of essential plant nutrients.

The filter has many strengths:

• It’s low-tech, with few moving parts, minimal maintenance, and a simple infrastructure.

• It uses little electricity—gravity and biological processes minimize power inputs—but the system still matches or exceeds the filtration efficacy of traditional mechanical or chemical methods.

• It’s versatile: the filter does well with high-fat effluent—like that from a slaughterhouse—which would tend to clog mechanical filters, or with high sugars, as encountered in winery waste. It also operates under a wide range of ambient air temperatures; a BIDA® filter has been happily filtering sanitary waste on the Eduardo Frei Chilean Airforce base in Antarctica for 10 years.

• It produces beneficial by-products: carbon and macronutrients, like nitrogen and phosphorous, which are considered contaminants in wastewater and can be greenhouse gas liabilities in the air, are sequestered in the filter in the form of worm castings and humus. When the filter is refurbished, the humus can be spread on crops as a natural fertilizer, thus helping to close the nutrient cycle. Worms, a high-protein feed source, are also harvestable from the filter. These benefits together have Fetzer Vineyards of California, a recent adopter of the BIDA® filter, anticipating becoming a Net Positive winery by 2030.

The adaptability and scalability of biological systems make for an ideal filter. In an earlier post, I reported on research work with bacteria to boost barley’s nitrogen use efficiency. BioFiltro’s BIDA® filter works on a similar concept by using bacteria to stabilize the chemistry of nutrients in effluent streams, turning contaminants into fertilizers while producing clean water.

It’s great to see BioFiltro’s success in leveraging the power of humble worms and bacteria to make a high-performance, energy-efficient filter with unconventional benefits. Compared to other areas of study in agriculture, microbiology is very underdeveloped. Much remains to be learned about the microbiome; the more we know, the more we’ll be able to use it to help us improve our agricultural practices.

Author: Paul Froese

I am a freelance Spanish to English translator specializing in scientific and technical texts. Visit my translation website at

Leave a Reply

Your email address will not be published. Required fields are marked *