https://orcid.org/0000-0002-7631-1636
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ABSTRACT
A lysimeter experiment was conducted to investigate the environmental effects of applying farm dairy effluent (FDE) treated with a chemical coagulant (polyferric sulphate) to land. The coagulant was administered as part of an effluent treatment system known as ClearTech. Two products are produced from the treatment process; treated effluent (TE) and clarified water (CW). Applications were applied in May. When compared to FDE, TE and CW reduced E. coli, Total-P and dissolved reactive P (DRP) leaching losses. Escherichia coli leaching losses were reduced by 99.97% and 99.99% for TE and CW, respectively. This was because of the acidity of the added coagulant and the encapsulation of the bacteria in the flocculated sediment. Compared to FDE, Total-P leaching losses were reduced by 90.5% and 85.7% for TE and CW, respectively. DRP leaching losses were also reduced under TE and CW by 99.5% and >99.99%, respectively. Reductions in phosphorus leaching were attributed to the reduced P solubility, resulting from the iron added in the coagulant binding to the phosphorus. There was no significant difference between treatments in the amount of iron leached, greenhouse gas emissions or Mineral-N leached (except where additional ammonium-N was added to the clarified water).
Acknowledgements
The authors wish to thank Lincoln University and Ravensdown Ltd for funding this research, and Trevor Hendry, Roger Atkinson, Jeneth Hendry, Shelagh Bassett, Stephen Moore, Carole Barlow and William Talbot (Lincoln University) for technical support. The senior author would like to thank the New Zealand Agricultural Greenhouse Gas Research Centre for the Honours scholarship.
Disclosure statement
No potential conflict of interest was reported by the author(s).