Farms Represent Sources of Environmental Zinc, Copper11 September 2012
JAPAN - Because of the large number of animals kept on most pig farms, such units are considered to represent a significant point source of zinc in bodies of water, according to researchers at the National Institute for Agro-Environmental Sciences. They also examined copper loads and output of both minerals from dairy farms.
Zinc and copper are toxic to aquatic organisms at very low concentrations that do not affect humans. In a paper published recently in Water Science Technology, Kaoru Abe and colleagues at the National Institute for Agro-Environmental Sciences in Tsukuba measured the daily output of Zn and Cu in wastewater from livestock farms to aquatic environments because waste from animal husbandry operations contains high levels of Zn and Cu.
At most pig farms in Japan, a mixture of urine, some faeces and service water is treated in on-site wastewater treatment facilities and discharged into a water body. Some dairy farms also have wastewater treatment facilities. The researchers surveyed 21 pig farms and six dairy farms.
The unit, i.e. per-head, output load from piggery wastewater treatment facilities ranged from 0.13 to 17.8mg per head and day for zinc and from 0.15 to 9.4mg per head and day for copper. More than 70 per cent of pig farms had unit output loads of zinc and copper below 6mg and 2mg per head and day, respectively.
For dairy farms, the unit output load from wastewater treatment facilities was estimated at 1.8-3.6mg per head and day for zinc and 0.6mg per head and day for copper.
The unit output load for zinc from piggery wastewater treatment facilities was similar to that from treatment facilities for human waste. However, pig farms generally raise several thousand to tens of thousands of pigs; pig farms are, therefore, presumed to be a significant point source of zinc in rural areas, Abe and co-authors concluded.
Abe K., Waki M., Suzuki K., Kasuya M., Suzuki R., Itahashi S. and Banzai K. 2012. Estimation of Zn and Cu unit output loads from animal husbandry facilities. Water Sci Technol., 66(3):653-8.
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