New Zealand Journal of Agricultural Research abstracts
Bacterial survival and dispersal in spray irrigation aerosols
A. Donnison1
C. Ross1
M. Noonan2
G. Fisher3
J. Waller1
1AgResearch
Private Bag 3123
Hamilton, New Zealand
email: andrea.donnison@agresearch.co.nz
2Lincoln University
Animal and Food Sciences Division
P.O. Box 84
Lincoln University
Canterbury, New Zealand
3National Institute of Water and Atmospheric Research
Ltd
P.O. Box 109 695
Newmarket
Auckland, New Zealand
Abstract New Zealand environmental authorities
favour land-based treatment for wastewaters of faecal origin. However,
microbial aerosols from spray irrigation could be a health risk. This
study investigated bacterial survival in irrigation aerosols in 105
field trials in spring and summer. Serratia entomophila and
tracer spores of Bacillus subtilis var. niger were
added to well water at about 105 ml–1 and
sprayed onto a flat paddock through either a high-pressure
horticultural sprayer (1400 kPa) to maximise aerosol production or a
low-pressure hammer-head rotary sprayer (300 kPa), commonly used for
irrigation. Aerosol particles were collected in six-stage Andersen air
samplers. Recovery of viable B. subtilis spores decreased with
increasing distance from the sprayers, due to dispersion. There was a
greater decrease for S. entomophila. Assuming similar
dispersion of both micro-organisms, the relative decrease in S.
entomophila was due to inactivation and this inactivation
correlated with decreasing relative humidity. Under the prevailing
meteorological conditions, viable S. entomophila were dispersed
to at least 100 m from the low-pressure sprayer and 200 m
from the high-pressure sprayer. Irrespective of sprayer type, sampling
distance or micro-organism, the majority of viable organisms were
collected on those Andersen sampler stages corresponding to the
respirable fraction of inhaled air.
Keywords aerosols; spray irrigation; wastewater;
bacterial cells; bacterial spores
A04027; Received 19 April 2004; accepted 19 August 2004; Online
publication date 15 December 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47:
575–585
0028–8233/04/4704–0575 © The Royal Society of New Zealand 2004
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