This study was undertaken to determine the microbial populations in ANC, SLP and MW sludge that would not be incorporated, and to determine the persistence over time of indicator organisms. A spring and fall field study was established in NW-30-59-12-W5 approximately 5 km southwest of Whitecourt on May 25, 1998 and on August 27, 1998.
- The spring study was comprised of an open site and a shaded site.
- The open site had nine 1 m x 1 m plots for the application of the sludges and one 1 m x 1 m control plot.
- The shaded site was comprised on one sludge and one control.
- The sludges were applied at a rate of 50 t/ha and samples were obtained prior to spreading to obtain baseline data.
- The fall study was established adjacent to the spring site and had three replicates of fresh sludge applied at 50 t/ha. A fall shaded site was not established.
- Following sludge application, samples were collected daily for seven days, weekly for four weeks, bi-weekly for eight weeks, and monthly for two months. The samples were enumerated for Klebsiella spp., fecal Enterococcus spp., and fecal coliforms (FC).
- Climate monitoring stations were set up at the sites to monitor meteorological conditions and assess the effect of climatic parameters on the indicator microorganisms.
- There was usually an ↑ in bacterial numbers immediately after sludge spreading.
- The rate of decline in bacterial populations after sludge application varied for different bacteria and different sludges.
- The large amount of water retained in the sludge impacted bacterial inactivation and death by desiccation.
- Similar patterns of bacterial concentrations were observed in open and shaded locations for each sludge evaluated.
- Generally changes occurred sooner at the shaded locations indicating that dehydration and UV radiation probably did not play a major role in the rate of decline bacterial populations in these sludges.
- Klebsiella pneumoniae, the microorganism of concern was not isolated from any of the sludge samples.
- Fecal coliforms were enumerated in all three sludges, however, fecal coliform isolates were only identified in two sludges.
- Drying and inactivation and death by desiccation will decrease as sludge application rate and/or thickness of the sludge layer applied increases.
- Similar precautions to those related to the handling of animal manure or sewage sludges are warranted when applying and incorporating sludge as a result of potential fecal coliforms.
- Due to the persistent nature of several of the indicator microorganisms, recommendations were made in the context of application of the sludge without incorporation.
- For land used for livestock grazing a waiting period of one month before grazing is recommended
- Composting prior to application is recommended for home lawn and garden use.
- No specific recommendations regarding applications without incorporation in the forest are provided except for the reminder regarding handling while spreading.
Sample collection from the sludge plots
Samples were placed in an autoclaved bottle or sterile plastic bag.
Climate monitoring station at the open site.