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Log reduction is a measure of how thoroughly a decontamination process reduces the concentration of a contaminant.It is defined as the common logarithm of the ratio of the levels of contamination before and after the process, so an increment of 1 corresponds to a reduction in concentration by a factor of 10.
In microbiology, in the context of a sterilization procedure, the D-value or decimal reduction time (or decimal reduction dose) is the time (or dose of an antimicrobial drug) required, at a given condition (e.g. temperature) or set of conditions, to achieve a one-log reduction, that is, to kill 90% of relevant microorganisms. [1]
Z-value is a term used in microbial thermal death time calculations. It is the number of degrees the temperature has to be increased to achieve a tenfold (i.e. 1 log 10 ) reduction in the D-value . The D-value of an organism is the time required in a given medium, at a given temperature, for a ten-fold reduction in the number of organisms.
Aerobic digestion is a process in sewage treatment designed to reduce the volume of sewage sludge and make it suitable [1] for subsequent use. [2] More recently, technology has been developed that allows the treatment and reduction of other [3] organic waste, such as food, cardboard and horticultural waste.
The target of reduction in canning is the 12-D reduction of C. botulinum, which means that processing time will reduce the amount of this bacteria by a factor of 10 12. The D R for C. botulinum is 0.21 minute (12.6 seconds). A 12-D reduction will take 2.52 minutes (151 seconds).
Specialist companies will often advertise a certain log reduction, e.g., 6-log reduction or 99.9999% effective, instead of sterilization. This takes into consideration a phenomenon known as light and dark repair ( photoreactivation and base excision repair , respectively), in which a cell can repair DNA that has been damaged by UV light.
Treatment times are very long, with a minimum time between removals of solid waste of a year; during treatment the volume of the solid waste is decreased by 90 percent, with most being converted into water vapor and carbon dioxide. Pathogens are eliminated from the waste by the long durations in inhospitable conditions in the treatment chamber. [5]
This minimizes the loss of residual food in the treated effluent. In simple terms, the more the biomass consumes the lower the biochemical oxygen demand ( BOD ) will be in the discharge. It is important that MLSS removes COD and BOD in order to purify water for clean surface waters, and subsequently clean drinking water and hygiene.