The Use of Pinus radiata Sawdust or Bark, or Zeolite to Reduce E. coli in Stand-Off Pads or Associated Drainage

Abstract

Cow dung slurry containing a total of 7.4 × 10⁵ E. coli was applied to laboratory-scale microcosms of Pinus radiata sawdust or bark. Rainfall was simulated by application of water at rates of 25 mm h^-1 or 50 mm h^-1 over 30 minutes. For sawdust 5% and 11% (respectively) of the E. coli were transferred to drainage compared to 12% and 28% for bark. After collection of drainage less than 10% of the retained E. coli were recovered from sawdust compared to about 90% for bark. Stand-off pad drainage (10²E. coli 100 mL^-1) was passed through laboratory-scale microcosms at 0.42 mL min^-1 for 4 weeks. The E. coli concentration was reduced by 1.5 log₁₀ for sawdust microcosms but there was no significant reduction for bark and zeolite. P. radiata sawdust seems an unfavourable environment for E. coli and its use in stand-off pads could reduce transmission of faecal microbes from dairy farms to waterways.