Water Chemistry

1
Water Chemistry MicrobiologyOn completion of
this module you should be able to

• Have some knowledge of the chemical and physical
  properties of water
• Have an understanding of water microbiology
• Be aware of some disease causing microorganisms
• Be able to describe the microbiological standards
  of drinking water

2
Typical Raw Water
3
Drinking Water Quality

• Water for human consumption must be free from
  pathogenic organisms and from chemicals hazardous
  to health
• Water must be aesthetically acceptable (odour,
  colour, taste), and also non-corrosive or scale
  forming
• Water should conform to some acceptable
  guidelines e.g. WHO, NHMRC

4
Water Quality CharacterisationWe can
characterise water quality in terms of the
following

• Chemical
• Physical
• Radiological
• Bacteriological

5
Chemical Properties of Water

• Dependent on the composition of solutes present
• Solutes are natural or introduced anions and
  cations in water, which may contribute to taste,
  odour and hardness
• Concentrations of solutes that are injurious to
  to health
• Solutes are largely inorganic but some may be
  organic

6
Some Health related Chemical Characteristics
7
pH of water
0
7
14
seawater
1 M NaOH
Gastric juice
Household ammonia
Pure water
1 M HCl

• pH -log10 H3O
• Buffering ionic forms of CO2 that offer
  resistance to pH change
• Diurnal changes in raw water may affect pH values

8
Effects of buffering in water
Pure water
Carbonate in water
Well water
Carbonic acid
9
Physical Properties of Water

• Colour
• Turbidity or total suspended solids (TSS)
• Total dissolved solids (TDS) which may be related
  to hardness
• Odour and taste
• Temperature

10
RadiologicalRadioactivity is the energy released
from the breakdown of radionuclides

• Naturally occurring radioactive species in
  drinking water sources
• Contamination from concentration of natural
  levels such as mining and processing of minerals
• Artificial radionuclides which may enter drinking
  water supplies from medical and industrial use of
  radioactive materials

11
Water MicrobiologyOf living organisms (apart
from animals and plants) there is a third kingdom
of Protisa

• Eucaryotic cells (2 - 200 micron)
• Procaryotic cells (0.5 - 2 micron)
• Viruses (20 - 100 nm)

12
Procaryotic CellsBacteria, blue green algae
(cyano-bacteria)

• Small size with simple organisation
• Nuclear region - single DNA molecule not
  separated from cytoplasm by any defined structure
• Cytoplasm - a site of protein synthesis (RNA), a
  colloidal suspension of proteins, carbohydrates
  and complex organic compounds
• Cytoplasm membrane with enzymes for transport of
  food into cells and removal of wastes
• Cell wall to maintain rigidity and shape of cell

13
A Bacterium Cell
14
Bacteria Cells
15
BacteriaSome are pathogenic. Majority assist in
breaking down matter. The bacterial cell is a
chemical machine that transforms energy through
metabolism

• Catabolism where larger molecules are broken down
  with the release of energy
• Anabolism a biosynthesis of new molecules from
  simple nutrients

16
Bacteria may be classified as

• Heterotrophic requiring an external organic
  source for energy and carbon
• Autotrophic that utilises inorganic compounds for
  energy and uses CO2 as a carbon source
• Aerobic, anaerobic and facultative in relation
  with O2

17
Eucaryotic CellsExamples are algae, fungi,
protozoa

• More complex than procaryotic cells
• Well defined nucleus with a nucleus membrane
• Membrane bound organelles that perform various
  tasks
• Unicellular or multicellular

18
Algae

• Resembles plants but without roots, stems, leaves
• Photosynthetic, autotrophic microorganism
• Important role of recycling nutrients in the
  aquatic food chain
• Contributes to clogging of filters, odour taste
  in water, and eutrophication

19
Fungi (yeast, mould, mushroom)The ability of
fungi to survive under low pH and nitrogen
limiting conditions, and distinctive degradative
ability makes them important in wastewater
treatment

• Non-photosynthetic
• Multi/or unicelluar and immotile
• Reproduce sexually or asexually
• Yeasts are unicellular, capable of aerobic and
  anaerobic growth
• Moulds are strict aerobes

20
Protozoa

• Non-photosynthetic
• Single cell eucaryote that obtain energy from
  metabolising organic matter by feeding on
  bacteria, fungi and algae
• Important role in the secondary settling of the
  wastewater treatment process
• Some are a concern in drinking water e.g.
  cryptosporidium, giardia

21
Protozoa
However, Scottish Water said it was safe to use
for washing clothes and dishes and for bathing -
although not for bathing babies.
22
VirusesDo not have the ability to reproduce
themselves but replicated only within a host cell

• Small structures of non-living compounds
• Composed of 2 kinds of macromolecules i.e protein
  and DNA or RNA
• Acellular
• Obligate intracellular parasites

23
Waterborne Diseases and AgentsDependent on the
causal agent

• Bacterial e.g. cholera, typhoid fever
• Viral e.g. hepatitis A, diarrhoea
• Protozoal e.g. amoebic dysentry, giardiasis
• Helminths e.g. schistosomiasis

24
Indicator Microorganisms for Drinking
WaterColiform group of microorganisms is present
in large numbers in animal and human excreta. Why
is there a need for such indicators?

• Pathogenic microorganisms are small in numbers
• Routine testing is not practicable and expensive
• Involves skilled labour and specialist equipment
• Specific tests may not be available

25
Indicator Microorganisms PropertiesMicrobial
indicators are E.coli and the coliform group

• Always present when pathogens of like origin are
  present
• Present in large numbers, gtgt pathogens
• Easy and quick to detect
• Equal or greater survival time than pathogens
• Absent from unpolluted waters
• Similar sensitivity to disinfection as pathogens

26
Bacterial Standards of Drinking Water

• 98 of samples in any one year should not have
  any E.coli in 100 mL
• 95 of samples in any one year should not have
  any coliform organisms in 100 mL
• Max 10 coliform organisms per 100 mL in any one
  sample
• No coliform organism in 100 mL of any two
  consecutive samples

27
Objectives of Water Sampling

• Ensure aesthetic qualities, adequate residual
  chlorine and free from harmful chemicals
• Bacterial qualities of raw and treated water are
  acceptable
• Sources of pollution or potential contamination
  are known

28
Types of SamplingRelated to population size

• Residual chlorine concentration
• Simple bacteriological test
• Simple chemical analysis
• Full chemical and bacteriological analysis

29
Frequency of SamplingRelated to population size
30
END OF MODULE 4