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2021 Pickering Medal: Technology to treat dairy effluent

Professor Keith Cameron ONZM FRSNZ and Professor Hong Di ONZM FRSNZ, both from Lincoln University, have been presented the Pickering Medal by Royal Society Te Apārangi for new technology 'ClearTech®’, invented to treat effluent on dairy farms.

The Pickering Medal is presented for innovative technological work with significant benefits or commercial success.

ClearTech® is a fully-automatic treatment system for farm dairy effluent that uses a coagulant to produce 'clarified water' and 'treated effluent'. It reduces the volume of effluent that needs to be irrigated or stored each day; separates and purifies water that can be recycled to wash the farmyard; and reduces the risk of contamination of rivers, lakes and groundwater. It recycles more than 50% of the water and can reduce phosphate and E coli leaching from effluent areas into water by over 90%.

The system was developed in collaboration with Ravensdown Ltd and was designed to be installed between the dairy shed and effluent pond. It intercepts and treats the farm dairy effluent with a coagulant to settle out the solids.

The ‘treated effluent’ that remains goes to the effluent pond to be eventually spread on pasture in the usual way, but it has reduced bacterial loading and its phosphorus content has been changed into a less leachable form.

With the solids removed, the ‘clarified water’ can be recycled for washing out the farmyard or used for irrigation.

Economic and environmental benefits as published in four internationally peer reviewed papers, show:

·        a saving of approximately 3,500,000 litres of freshwater on an average 400-cow NZ dairy farm per year by recycling clarified water;

·        more than 90% reductions in phosphate and E. coli leaching from effluent-applied areas on a dairy farm into rivers, lakes and groundwater,

·        a 60% reduction in the volume of dairy effluent that needs to be irrigated or stored each day.

The technology was developed in response to farmers asking for help from the researchers because they were concerned about the adverse impacts of farm dairy effluent on the environment and the risk to their business of breaching their effluent consents. An average 400-cow New Zealand dairy farm produces around 28,000 litres of farm dairy effluent each day and over 7,500,000 litres per year. Effluent can only be applied to the land when soil and environmental conditions ensure there be no risk of ponding, runoff or leaching; this can be difficult when soils are wet, or if it is raining.

The fundamental process involves treating the effluent with a precise dose of coagulant in a mixing and clarification tank. The coagulant neutralises the negative electrical charges on the surfaces of colloidal particles in the effluent (e.g. soil, dung and organic matter), allowing these particles to form into 'flocs' with sufficient mass to settle out of the water under gravity. Once settled, the 'clarified water' in the top 60% of the mixing tank can be recycled to wash the farmyard, saving valuable fresh water.

Laboratory based research identified the best type of coagulant to treat farm dairy effluent, and determined the relationships between coagulant dosage rate, effluent turbidity, and effectiveness of clarification.

Field based soil lysimeter studies measured leaching losses from treated effluent versus untreated effluent. The pilot plant, built on the Lincoln University Dairy Farm using a 30,000 L tank system, enabled the development of the ClearTech® commercial unit; a totally automated whole treatment system controlled by a programmable controller, without the need for farmer intervention.

The research team worked in partnership with Ravensdown Ltd to commercialise the effluent treatment system specifically for dairy farms. Four New Zealand patents have been granted for the ClearTech® technology and Ravensdown Ltd have established a new business unit for ClearTech® 

In 2019, the ClearTech® won the NZ Primary Industry 'Research & Science Award', the 'Agri-Innovation Award' at the South Island Field Days; and a highly commended award at the '2019 National Fieldays'.

Professor Keith Cameron was the establishment head for the Centre for Soil and Environmental Research at Lincoln University in 1995 and Professor Hong Di is Professor of Soil and Environmental Science at Lincoln University. Both were appointed as an Officer of the New Zealand Order of Merit in 2008 for services to agricultural research in the Queen’s Birthday Honours. They are both Fellows of the Royal Society Te Apārangi of New Zealand, the New Zealand Institute of Agricultural and Horticultural Sciences and the New Zealand Society of Soil Science.

Upon winning the medal, Keith and Hong said: “We feel greatly honoured by the award of the Pickering Medal from the Royal Society of New Zealand. We would like to thank Ravensdown Ltd for their collaboration and co-funding of the research work that that led to the development of the ClearTech dairy effluent treatment system. We are also grateful to Lincoln University for co-funding and would like to thank our superb technical team for their support and their hard work; especially Roger Atkinson, Steve Moore and Carole Barlow.”

The Pickering Medal is awarded annually to a person or team who, while in New Zealand, has through design, development or invention performed innovative work the results of which have been significant in their influence and recognition both nationally and internationally, or which have led to significant commercial success.

To Keith Craig Cameron and Hong Jie Di for inventing new technology to treat farm dairy effluent to recycle water and reduce phosphate and E coli leaching into water.