By Anne Lee

Two pilot EcoPond plants are successfully operating in the Te Waihora/Lake Ellesmere catchment zone, helping to reduce the amount of phosphate heading into the sensitive lake.

EcoPond is an effluent treatment system developed by Ravensdown and Lincoln University and uses a common drinking water treatment and food additive, iron sulphate, to treat effluent as it moves from the dairy shed to the effluent pond.

The ground-breaking use of the technology in the treatment of effluent has been proven to not only cut the risk of phosphate leaching from areas where effluent is applied to land by more than 90%, it currently offers dairy farmers one of the greatest single methane reduction options without dropping cow numbers or limiting milk production.

Research published in the Journal of Soils and Sediments by Lincoln University professors Keith Cameron and Hong Di shows methane emissions from effluent ponds could be all but eliminated.

Methane from effluent makes up about 4-5% of a dairy farm's total methane emissions’ profile.

Government targets require farmers to cut methane emission by 10% from 2017 levels by 2030.

A third major benefit of the system is the ability to reduce E. coli bacteria in the treated effluent by more than 90%.

Ravensdown EcoPond development manager Carl Ahlfeld says that for the sensitive Te Waihora catchment the two pilot plants are providing all three significant environmental benefits and helping limit the potential for dissolved reactive phosphate (DRP) and E. coli from entering drains, lowland streams and the lake.

Research will be expanded over the next six to 12 months with five new early adoption units likely to be installed on dairy farms in several regions.

Keith says reducing the risk of DRP leaching from areas where effluent is applied to land is especially important because phosphate is often a limiting factor the growth of aquatic algae associated with the eutrophication of streams and rivers.

“If we can reduce the phosphate going into rivers and lakes it will help to improve the health of those rivers and lakes," he says.

Di says the effluent treatment process cuts leaching risk because the iron sulphate reacts with DRP in the effluent converting it to a slow-release form of phosphate that can be stored in the soil for plants to use.

So while P leaching losses are cut by more than 90%, the level of phosphate as a nutrient for plant growth isn’t reduced and pasture growth is not limited.

Carl says feedback from farmers using EcoPond or ClearTech (which uses the same technology with additional benefit of producing clarified water for yard washdown) systems has been extremely positive.

“They’re excited and grateful for the technology that’s helping them achieve their environmental and farming goals.”

He says the EcoPond system can be readily retrofitted into existing effluent systems with the treatment process occurring “in-line” between the dairy shed where effluent is collected and the pond.

Former Prime Minister Jacinda Ardern views EcoPond with Professors Hong Di and Keith Cameron, and Carl Ahlfeld from Ravensdown.