Municipal Wastewater Disinfection – Two Important Terms You Must Know

The waste generated by municipalities is always a matter of concern to various bodies charged with preventing environmental pollution. In my previous article I had discussed Watson’s law and its relevance to the wastewater treatment process. In this article I discuss two more terms that should be understood by those wanting to understand municipal wastewater disinfection methods.

1. Disinfection (Inactivation Rate Microorganisms (Chick’s Law)) –

Like the Watson’s law, this law also 甲醛 describes the relationship between the time required for the disinfecting agent to disinfect wastewater and it concentration. This is represented in the equation – dx/dt = kx, where x represents the quantity of the microorganism at an instant of time t and k represents the rate of decay of the microorganism measured as 1/time. But this law can also be written as ln(x/xo) = -kt, where x represents the number of microorganisms noticed during the time t measured as number / unit volume. xo represents the amount of microorganisms before the addition of the disinfectant also measured as number / unit volume, k like before is the decaying rate of microorganisms, and t the time taken for this operation to complete.

When this law is actually actually applied for measuring the disinfectant, one has to assume that the conditions will stay stable. Thus the disinfectant will always be at the same level of concentration, all the different verities of microorganisms are assumed to have equal level of susceptibility to the disinfectant and most of all there wont be any adverse conditions to disturb the reaction. Therefore this law is not follow a first order rate kinetics reaction. Like the Watson’s law, this law too when plotted on an x-y plane reveals a straight line. But compared to that, this law has severe limitation and is better suited for laboratory analysis rather than a field level analysis of the municipal wastewater disinfection process. But it can be used to understand the disinfecting wastewater methodologies.

2. Disinfection (lethality coefficient)

This coefficient is actually an important wastewater terminology useful in the measure of the efficacy of the disinfecting agent used in wastewater. This coefficient is written as the following reaction – 8 = 4.6 / C T99, where 4.6 is actually taken as the natural logarithmic value of 100, T99 is the time required to achieve a percentage level of 99 % with the aim of eliminating the contaminating microorganisms usually measured in minutes and C is residue left behind after the required action has been completed the quantity of which is measured in mg/l. The value obtained by using the above mentioned reaction will be different for different types of disinfectants. This is an important term for anyone trying to understand the complexities of the municipal wastewater disinfection process.

Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched.

 

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