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embargoed access
Embargoed until 2024-08-21
Copyright: Pointing, Lewis
Embargoed until 2024-08-21
Copyright: Pointing, Lewis
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Abstract
Wastewater processing conditions in manufacturing environments often involve the three key factors
for optimum bacterial growth - water, ideal temperature, and a constant food source. Bacteria are
problematic because they can reduce product yield by consuming product and metabolise it into
organic acids which lower the process pH, requiring large amounts of chemicals to control. At a casestudy
wastewater treatment plant, a site-wide analysis of the impacts of chemical sanitation methods
had not been conducted and the efficacy of these chemicals had not been established. To understand
the impacts of current sanitation practices, standard microbiological plating techniques combined with
HPLC testing to measure lactic acid as a proxy for microbial activity were used. Nitrogensource
determination and solids analysis were used extensively to provide a comprehensive picture of
the stream properties throughout the plant. I show that current microbial control methods are
ineffective for significantly limiting microbial growth in the water treatment plant. The most
important factors impacting this are the concentration of nitrogen-sources followed by total organic
solids at chemical dosing sites, which react more rapidly with oxidative sanitisers than bacteria
do. These findings indicate that chemical sanitisers would be more effective if dosed in locations with
minimal concentrations of nitrogen-sources and organic solids. In practice, this is difficult to achieve
in an existing plant without significant capital expenditure and so investigation of alternative, nonchemical
methods of sanitation in combination with more effective use of chemical methods is
recommended.