Disinfection microbiology and chemistry
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Disinfection: Microbiology and Chemistry. J(Hans) van Leeuwen. Introduction. Need for disinfection Alternative disinfectants Disinfection kinetics Disinfectant chemistry. Topics of Discussion. Diseases borne by water Comparison of disinfectants The Ct concept. Viral. Bacterial.

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Disinfection: Microbiology and Chemistry

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Disinfection: Microbiology and Chemistry

J(Hans) van Leeuwen

Disinfection


Introduction

  • Need for disinfection

  • Alternative disinfectants

  • Disinfection kinetics

  • Disinfectant chemistry

Disinfection


Topics of Discussion

  • Diseases borne by water

  • Comparison of disinfectants

  • The Ct concept

Disinfection


Viral

Bacterial

Protozoan

Typhoid fever

Para-typhoid

Bacterial diarrhea

Cholera

Legionnaires’ disease

Hepatitis

Rotavirus diarrhea

Amoebiasis

Giardiasis

Crypto-

sporidiasis

Some common water-borne diseases prevented by disinfection

Disinfection


The rate of disinfection

Like most biological processes, disinfection follows a first-order reaction with respect to the number of microbes of a certain species surviving as a function of time at a constant level of a disinfectant

- dN/dt = kN, which is also known as Chick’s Law

dN/N = - kdt (separating variables)

ln N/No = - kt or N = No e-kt (from integration)

Disinfection


The Ct Concept

In disinfection, the ability to inactivate

microorganisms is a function of both

disinfectant concentration and time.

Fractional removal, N/No = Cntm

This is generally simplified to

N/No= Ct

Ct values have been determined for

99.99% virus and 99.9% Giardia removal

Disinfection


Disinfection


Ozone Ct values

Disinfection


Chlorination

Disinfection


Chlorinator

Disinfection


Chlorine gas flow control

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Chlorine contact tank with baffles

Disinfection


Gravity fed chlorine solution feeder

Disinfection


Gravity fed chlorine solution feeder

Disinfection


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Ultraviolet Irradiation

Disinfection


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Simple Solar Disinfection

Disinfection


Solar Disinfection

Disinfection


Ozonation

Disinfection


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Biomass bulking control

Disinfection


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Effect of ozonation

on sludge settling

Disinfection


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Selective oxidation

Disinfection


MeBl oxidation

Disinfection


Effect on protozoa

Disinfection


Ships’ Ballast Water Disinfection

NUTECH O3, NOAA, NETSCO, UNCW, UWS, ISU, et al.

Disinfection


Alien Invaders in

our Coastal Waters

- weirder and risky

Disinfection


Disinfection


Zebra Mussel

Distribution

Disinfection


San Francisco Bay:212 exotic species and 140 more suspected

Disinfection


Cross section of ships showing ballast tanks and ballast water cycle

Disinfection


Propeller exposed under

unballasted conditions

Disinfection


Into the Tonsina’s ballast tanks

Disinfection


View of ballast tanks from below

Disinfection


Disinfection

Interconnectivity of ballast tanks in sideview


INSIDE THE OZONE GENERATOR ON THE TONSINA

Disinfection


Side-stream

ozone

injection

Disinfection


Ozone Reactions in Seawater

  • O3 + Br- OBr- + O2

  • OBr- + O3 2O2 + Br-

  • OBr- + O3 BrO2- + O2

  • BrO2- + O3 BrO3-

  • H+ + OBr- HOBr

    HOBr main contribution to total residual oxidant (TRO)

Disinfection


TRO Decay with time

Decrease in TRO (mg/L Br2) in unfiltered Puget Sound seawater over time,

starting at 2.0, 3.0 and 4.0 mg/L Br2. Data are the mean + SD of four replicates.

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