Sedimentation of Bacillus sphaericus in tap water and sewage water.
Formulations of Bacillus sphaericus products were applied in 1-m columns of clean water and sewage water in tubes. Samples taken through valves attached to the walls of the tubes showed that spores settled as a function of application method, droplet size, particle size, and water characteristics. In a mixture of deionized and tap water, the slowest sedimentation rate was obtained with a primary powder sonicated in water with 0.1% detergent. This product and a commercial fluid product settled faster in sewage water than in clean water and after 4 weeks, most spores were found in the sediment. In clean water, most spores remained suspended during the 4 weeks but the density was highest at the bottom. Calculation of total spore numbers in the columns after 4 weeks indicated that about 90% of spores disappeared in clean water, and 95-97% disappeared in sewage water. Bioassays showed that toxicity declined in parallel with the sedimentation, but at a higher rate, indicating a loss of toxicity from the residual spores.
Skovmand
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The Danish Pest Infestation Laboratory, Skovbrynet 14, Lyngby, Denmark.
Guillet
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D000818:Animals; D001407:Bacillus / Q000302:isolation & purification*; D015169:Colony Count, Microbial; D009033:Culicidae; D008828:Microbiological Techniques; D012722:Sewage / Q000382:microbiology*; D014867:Water; D014871:Water Microbiology
D012722:Sewage; D014867:Water