New technology treats dairy waste and odours

A Battelle technology brought to Northwest America by researchers at the US Department of Energy's Pacific Northwest National Laboratory is transforming a waste lagoon into a waste treatment facility at a Washington State dairy.

The George DeRuyter Dairy in Outlook, Washington has been fitted with InStreem since January. The technology is said to enhance naturally occurring biological activity to clean waste lagoons.

Lagoons traditionally have been used in the US to store manure and liquid effluents from dairy herds.

Wastes stored over the winter are pumped onto fields in the spring where crops utilise the manure's nutrients. However, more nutrients, such as nitrogen and phosphorous, may be applied to crops than can be used effectively.

'InStreem is designed to use a dairy's existing infrastructure to convert lagoons from waste storage facilities to facilities that solve waste problems,' said John Jaksch, PNNL program manager for the project in the Pacific Northwest. 'In doing so, this technology addresses one of the dairy industry's most pressing issues.'

Unlike conventional treatment methods, InStreem converts existing lagoons into extended aeration systems, establishing conditions favourable for both aerobic and anaerobic degradation of wastes.

The aerobic process is designed to remove excess nitrogen and the anaerobic process is designed to remove other nutrient constituents, such as phosphorous.

InStreem maintains an oxygen deficit condition in the lagoon and does not over aerate, while still allowing nutrient reduction to take place and bacteria to work on reducing the manure sediments. One InStreem unit treats a lagoon 1 to 1 1-2 acres in size.

To date, the demonstration is exceeding Jaksch's expectations. 'In three months, the depth of solids dropped from six feet to six inches, and that was during the coldest part of the year,' Jaksch said. 'And since InStreem uses a small, five horsepower engine to circulate the entire lagoon, it's energy efficient.'

In addition, InStreem has been successful tackling a problem common to all dairies - odour.

Equipped with 10, 48-inch aeration discs powered by the five horsepower motor, the floating InStreem unit displaces water in adjustable horizontal and vertical planes around a barrier dividing the lagoon.

In dairy applications, the technology replicates fixed site municipal wastewater biological treatment technologies, used at more than 400 community waste treatment plants across the United States and Canada,' said Jaksch.

The DeRuyter dairy, located on the dry, eastern side of Washington, is a large operation with about 2,600 head of cattle. DeRuyter utilises a flush system in which the feed/loafing areas are flushed hourly with water.

Manure is carried by water through a solids separator. The solids are turned into compost and the wastewater, laden with suspended manure solids, is returned to the lagoon where it is recycled back into the flush system after processing.