Waste not, want not — a different way to treat farm effluent

Chilean biowaste filtering system is an alternative to lagoons in treating liquid waste from dairies

Farmers know that earthworms are good for the soil — now they’re being used to process liquid waste from dairies, hog operations, and slaughterhouses.

The process not only provides faster treatment than using lagoons, but also significantly reduces concentrations of nitrogen, phosphorus, and potassium and therefore the need for as much farmland to dispose of treated waste water.

“The best thing about our system is that it is natural,” said Mai Ann Healy, business development manager for BioFiltro, a Chilean company with offices in California.

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“We are using these nutrients generated by cows to feed more animals, in this case, microbes and bacteria to earthworms — it’s that simple,” she said. “We are using a technology that is billions of years old that is tried and proven by Mother Nature.”

The rapid treatment process using earthworms is called BIDA, and the company’s first commercial-scale system in North America was installed on Royal Dairy, a 5,000-cow operation located between Spokane and Seattle that produces about 750,000 litres of waste water. The dairy used to need 1,600 hectares to dispose of its effluent water, but now only needs about 120 hectares. It also saves the farm about US$300,000 annually on trucking costs, said owner Austin Allred, adding the system, which cost a couple of million, will pay for itself in about five years.

He first heard about the BIDA system at a farm show in California.

“Really what they claimed to be able to do seemed almost too good to be true. The amount of nitrogen that they claimed to be able to remove didn’t seem realistic,” said Allred, adding he would now recommend it to other farms.How it works

The entire installation is enclosed within either a concrete or steel structure, with a network of sensors and control panels tracking the system’s performance and water quality parameters. The effluent first passes through a separator to reduce suspended solids to 2,000 milligrams per litre. (The solids can be reused as bedding or sold.) The waste water then goes to a tank where sensors monitor constituents such as pH and flow, and then to an irrigation system which deposits it on the surface of the BIDA system.

It then trickles through layers of wood shavings, river cobble, and drainage basins before the final discharge. BioFiltro says the process takes just four hours, and the bioreactor is virtually odourless and requires minimum storage capacity.

As part of the installation, a mix of worms and bacteria are added to the wood shavings media. These are naturally occurring, local species of earthworms. The burrowing worms create air channels, digest suspended solids, and achieve densities of 15,700 worms per cubic metre while working symbiotically with bacteria to create a biofilm. This biofilm is what captures and digests the contaminants from the liquid waste.

The high density of earthworms per cubic metre keeps the temperature in the system elevated so it keeps working during winter. It has worked effectively in Washington down to -10 C and is removing 86 per cent of the nitrogen, 84 per cent of the phosphorus, and 94 per cent of total suspended solids in the effluent.

Over time, the earthworms produce castings that they then push to the surface. So the top 26 centimetres of the installation is excavated about every year and a half, and the plan at the dairy is to sell the castings as a soil amendment.

The system not only works for dairy, but for any farm or business generating a biological liquid waste stream, said Healy.

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