New Zealand Journal of Agricultural Research abstracts
Algal abundance, organic matter, and physico-chemical characteristics of dairy
farm facultative ponds: implications for treatment performance
JAMES P. S. SUKIAS
CHRIS C. TANNER
ROBERT J. DAVIES-COLLEY
JOHN W. NAGELS
National Institute of Water & Atmospheric
Research Ltd
Private Bag 11 115
Hamilton, New Zealand
RONALD WOLTERS
Golder Associates (UK) Limited
54-70 Moorbridge Rd
Maidenhead, Berkshire,
England SL6 8BN, United Kingdom
Abstract Six Waikato (New Zealand) dairy farm facultative
ponds (DFPs), which met the larger sizes specified in recent dairy industry
guidelines, were sampled monthly over an annual period. Median wastewater BOD5
was 65 g m-3, suspended solids (SS) 206 g m-3,
ammoniacal N 37 g m-3, total nitrogen 69 g m-3, and
faecal coliforms 24 000 (100 ml)-1. This was 20-70% better than
reported for DFPs built to previous guidelines, except for SS levels which were
within reported ranges. However, performance was highly variable and only
1/2 of the DFPs studied consistently met an effluent standard of
<=100 g m-3 BOD5 and only one reached <=150 g m-3
SS. Removal of BOD5 was much lower than recorded for SFPs in New Zealand with
equivalent BOD5 loading. Although the mean euphotic depth was only 0.11 m,
algal biomass in DFPs was similar to that recorded for SFPs. Low phaeophytin
concentrations and daytime oxygen exceeding 200% saturation in the shallow
epilimnion on sunny days suggested a relatively healthy photosynthetic algal
population was present in the DFPs. However, wastewater entering DFPs showed
high median COD levels (1420 g m-2). COD:BOD5 ratios of c. 12.1
(compared with 1.5-1.8 for SFPs) and BOD10:BOD5 ratios of c. 2 indicated the
presence of a large pool of slowly degradable organic matter in the wastewater.
This resulted in sustained exertion of BOD in the pond, explaining the
"apparent" poor removal of BOD5 by DFPs. Conductivity was found to be a useful
single-measure indicator of overall pond performance and management of sludge
levels in the preceding anaerobic pond was identified as a key factor affecting
DFP performance. Further improvements in dairy farm stabilisation pond
performance are likely to be required on many farms to meet receiving water
guidelines for the protection of water quality and aquatic life.
Keywords wastewater; dairy effluent; waste stabilisation
ponds; agricultural wastes; algal biomass; ammonia; sludge; pollution;
environmental effects
New Zealand Journal of Agricultural Research, 2001, Vol. 44: 279-296
0028-8233/01/4404-0279 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (1302K); (scanned from paper original: notes about this process)
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