Green water turns into yard wash

The patented technology, known as ClearTech, looks to cut freshwater use, help existing effluent storage ‘go further’ and reduce environmental and safety risks linked with dairy effluent. 

It is now being tested at pilot scale at the Lincoln University Dairy Farm, where it was publicly unveiled on May 3, giving farmers a preview of likely future technology.

Installed between the dairy shed and the effluent pond, ClearTech automatically monitors and treats circulating effluent.  

It uses a special coagulant to bind effluent particles together to settle them out from the water. The separation process kills up to 99% of microorganisms such as E. Coli, and reduces smell.  

Ravensdown said the pilot has so far cost the co-op $1.5 million.  

Jamie Thompson, Ravensdown’s effluent technology manager, said the technology has potential to reduce the environmental impact of effluent discharge on farms and to transform ‘green water’ for use as yard wash.

“About a quarter of a dairy shed’s fresh water use is in yard washing, so the potential benefits to New Zealand are enormous of safely reusing ClearTech-treated water. 

“It could save 42 billion litres of freshwater a year -- the equivalent of 17,000 Olympic-sized swimming pools.”

Thompson said 70% of dairy farmers’ environmental spending is on effluent management.  ClearTech can make their effluent storage go further and help them meet compliance obligations. 

Lincoln University soil science professors Keith Cameron and Hong Di are joint leaders in the science of the new system.

Cameron said they are “encouraged” at the industry’s willingness to collaborate in the development.

Ravensdown chairman John Henderson said he is finding dairy farmers determined to work together to tackle issues related to water use. 

“This new technology is one important step... towards continuous improvement in the sector.” 

Dairy Holdings chief executive Colin Glass said the technology could transform the use of water in dairy operations and help reduce nitrogen losses. 

“[To shareholders] it makes sense Ravensdown is the driving force behind it, because the company is increasingly seen as a nutrient efficiency specialist.”

The university and Ravensdown have been working on ClearTech for the last three years.

After looking at overseas water purification practices, including the use of coagulants, the Lincoln team tested potential coagulants to find the best for use with dairy effluent. They then developed computer algorithms to monitor the effluent and apply the right amount of coagulant as required over time.

Late 2018 release

Ravensdown says its new ClearTech effluent treatment will likely go on sale later this year, once testing is complete.

It recycles water for yard washing and stores any remaining treated effluent in the farm’s effluent pond. 

An integrated system comprises computerised processors, controllers, tanks, pumps and pipes.  It can be retrofitted between a dairy shed and an existing effluent pond. 

The benefits:

Recycling effluent water-content into yard-wash reduces the daily effluent volume, so reducing the quantities going into a farm’s storage pond.

Less likelihood of environmental breaches from effluent ponds overflowing, and less need to apply effluent to land when soil conditions would not allow this. 

Less freshwater used for dairy yard washing. The clear liquid portion of the treated effluent goes to a holding tank for the next yard wash, possibly cutting freshwater yard washing by as much as 65%.

Reduces microorganisms and odours via a 99% cut in E. coli in treated dairy effluent.