The document summarizes drinking water purification methods. It discusses parameters for water sources, such as acceptable coliform and turbidity counts. Surface water is treated through clarification and disinfection, including coagulation, flocculation, sedimentation and filtration to remove particles, as well as chlorination to disinfect. Regulations like the Safe Drinking Water Act establish standards for drinking water quality. Treatment systems filter water and use disinfectants like chlorine, ozone and UV light to remove pathogens before water is stored and distributed.

1. Chapter 6 –Drinking Water Purification
(Hwk#6- pp.179 2,4,6,8)
•water source – Coliform count up to 5000/100 mL
and turbidity of up to 10 units is good. Over
20,000/100 mL and turbidities that exceed 250 units
is very poor for treating to potable water.

2. Chapter 6 –Drinking Water Purification
•Surface Water Treatment-Clarification and
disinfection. (Clarification –coagulation-flocculation,
sedimentation, and filtration; Disinfection –
chlorination)
•SDWA- Safe Drinking Water Act(1974)-protect
surface water quality for people consumption
•1996 revision included: stricter controls on
microbial contaminants,and by-products of
chlorination, water utilities notify public of water
saftey violations within 24hrs, and EPA certification
for water system operators
Lehigh Valley Water Supply Tour
http://www.lvwater.org/tour/frame_tour.htm

3. Chapter 6 –Drinking Water Purification
Primary Standards (Drinking Water) -set
maximum permissible levels of potentially harmful
substances
•MCLs- Maximum Contaminant Levels
•MCLGs- Maximum Contaminant Level Goals
[this level is not expected to cause any health
effects; it is not enforceable;zero for carcinogens]
•primary contaminants includes organic and
inorganic chemicals, microorganism, turbidity,
radionuclides
•See table 6.1 & 6.2 in text pp.150 & 151
Secondary Standards (Drinking Water) –are
guidelines that apply to the esthetic qualities of
drinking water (i.e. color and odor) see Table 6.3

4. Chapter 6 –Drinking Water Purification
Sampling Procedures
•Sampling Frequency
•Points or Location of Sampling (for
representative sample- fully flushed sample for
most contaminants, except lead and copper which
would be the first draw)
• Type and Size of Containers(i.e. 100ml for
coliform to 1L for radionuclide)
•Temperature/Air Space – VOCs should not
allow for any air space
•Time for Chain of Custody – Coliform must be
delivered within 24 hrs. and radionuclides within
a year
Record Keeping and Reporting
•SDWA requires that public water systems
submits reports for the public and a monthly
report for local regulatory agency
•The State must be notified within 48 hrs. of a
Violation of a primary MCL

5. Sedimentation [sedimentation tank, settling tank,
or a clarifier]
•particles settles to the bottom under quiescent
conditions (when flow velocities and turbulence
are minimal)
•sludge – is the accumulated solids on the bottom
•Depends on density, size, drag, buoyancy,
temperature and viscosity of water
•discrete settling – occurs at lower concentrations,
no interference from other particles
•hindered settling – interference from other
particles due to high concentrations
Detention Time
Chapter 6 –Drinking Water Purification
Note: Zone of stream pollution on page 122 &123
tan
( )
D
D
V
T
Q
where T dententiontime
V volumeof water in k
Q average flowrate volume per unit time





6. Overflow Rate – is the average upflow velocity of
water in the settling tank, where particles that settle
faster than Vo reach the sludge layer.
Chapter 6 –Drinking Water Purification
tan ( )
o
S
o
s
Overflow Rate or Surface loading
Q
V
A
V overflow rate
Q average flow rate
A k surface area top view




Suspended
Solids
Effluent
Channel
Clear
Water

7. SWD- side water depth is the actual depth of the
water in a settling tank. see p.157 - fig. 6.6
Freeboard – it serves to prevent splashing of
water over the tank sides.
Short-circuiting – Time to flow out of the settling
tank exceeds the detention time for settling the
particles
Weir loading rate – The flow rate per foot that
should be less than the specified maximum value.
(should keep particles from flowing over the weir)
Chapter 6 –Drinking Water Purification
Settling Tank Design

8. Chapter 6 –Drinking Water Purification
http://www.h2o4u.org/story/index.html#contents

9. 2. The floc settles on these plates and
eventually falls to the bottom of the basin,
leaving clear water on the top!
Then, an underwater vacuum cleaner travels
along the bottom of the basin and sucks up all
the sediment.
1.As the water flows into this basin, it is forced
to flow uphill between hundreds of flat 'plates.'
As the water flows over the top of these plates,
the floc gets stuck on the surface and collects
there.

10. Chapter 6 –Drinking Water Purification
Coagulation and Flocculation
Coagulants- causes colloids to stick together by
neutralizing their charge.
Flocs – are larger clumps of colloids that can settle
out.
Coagulation – Is considered the combined
process of flash-mix of coagulant and the slow
mix allowing for sedimentation.
Weir loading rate – The flow rate per foot that
should be less than the specified maximum value.
(should keep particles from flowing over the weir)
Rapid Filters .vs. Slow Sand Filters – rapid
filters have water flowing 30 times faster through
them than Slow Sand Filter and includes a
backwashing system (see P. 161 in Text)
Filtration (sand filtering system)

11. Chapter 6 –Drinking Water Purification
1.Water flows into these filter beds and slowly
flows through layers of anthracite coal, sand and
gravel, which collect fine particles and micro-
organisms.
2.These controls monitor the level of water in the
filter beds to make sure it is evenly distributed
among all the filters.

12. Chapter 6 –Drinking Water Purification
Disinfection
THM (TriHaloMethanes) – A carcinogenic
compound produced by the decay of an organic
substance such as vegetation in Chlorine. (i.e.
Chloroform)
Note: The lower the pH the more effective the
chlorine disinfection.

13. Chapter 6 –Drinking Water Purification
Disinfection
Chloramines – a compound form from the
reaction of ammonia and chlorine (or combined
chlorine). (used in swimming pools)
• It is a slower disinfectant but last longer.
•It has an objectionable taste and odor
Free available Chlorine – The radicals HOCL
(hypochlorous acid) and OCL- (hypochlorite
radical). It is a faster disinfectant
Breakpoint Chlorination- is when enough
chlorine is added to satisfy the chlorine demand
and to react with all the dissolved ammonia.

14. Chapter 6 –Drinking Water Purification
Method of Disinfection
•#1 Chlorine Residual - After filtration, extra
chlorine travels with the water through the
underground pipes that bring the water to your
home. If there is any bacteria in the pipes, it will be
killed by the remaining chlorine
•We monitor the chlorine residual to make sure it's
high enough to kill any bacteria it encounters on
the way to your home, but low enough to be safe
and to reduce odor and taste problems.

15. Chapter 6 –Drinking Water Purification
Method of Disinfection
•#2 Turbidimeter - This meter displays numbers
which tell us the 'turbidity' level of the water.
'Turbidity' is a measure of the cloudiness of the
water. At this stage of the treatment process, the
water should be very clear and clean!

16. Chapter 6 –Drinking Water Purification
Method of Disinfection
•#3 Particle Counter - As the water passes through
this test, the equipment counts the number of
particles that pass through it. It also measures the
size of the particles. The information generated by
this equipment helps us to refine our filtering
process.

17. Chapter 6 –Drinking Water Purification
Method of Disinfection
Ozone (O3) – a gaseous disinfectant
•It has been used for greater than 90yrs in Europe
•Produced by passing very high electric current
into the air (very expensive to produce)
•It is very unstable and cannot be stored
•It leaves no measurable residual in water, so that
some chlorine must be used as a precaution
•It does not produce THM (carcinogen)
•It is stronger than Chlorine
•It can assist as a coagulant when used with alum
(aluminum sulfate-a coagulant), reducing the
amount of chemicals needed to adjust pH
•It also aids in the filtration process as a coagulant
•Read the Milwaukee Case study - Text 171
•Also oxidizes and precipitates iron, sulfur, and
manganese so they can be filtered out of solution.
•Ozone treatment creates its own byproduct that
can be harmful to health if they are not controlled
(e.g., formaldehyde and bromate).
•Ozone will oxidize and break down many organic
chemicals as well

18. Chapter 6 –Drinking Water Purification
Method of Disinfection
Ultraviolet Radiation (UV) – an electromagnetic
radiation just beyond the blue end of the light
spectrum.
•It is absorbed by genetic material in micro-
organisms interfering with their reproduction
•Mercury Lamps are best suited for large fractions
of UV energy that is needed for disinfection
•It is very unstable and cannot be stored
•It does not involve any chemical handling
•It leaves no residual in water

19. Chapter 6 –Drinking Water Purification
Ground Water Pollution
http://www.timesunion.com/news/special/water/graphics/ground.stm
http://www.cyber-nook.com/water/contrisks.htm#sources

20. Chapter 6 –Drinking Water Purification
Method of Disinfection
1Leakage from landfill.
2Chemical application to parks and lawns.
3Road salt.
4Irrigation.
5Industrial emission.
6Municipal sewage discharge.
7Underground mining.
8Water table reduced by heavily pumped well.
9Sewer and pipeline leaks.
10Storm water runoff.
11Underground storage tanks.
12Fresh water aquifer.
13Municipal water supply well.
14Pesticides and fertilizers from agricultural land.
15Private well.
16Leaks from oil storage tanks.
17Leakage from septic tanks.
18Saturated zone.

21. Chapter 6 –Drinking Water Purification
19Water table.
20Livestock waste.
21Marine waste.
22River water contaminated with urban,
industrial and agricultural pollutants.
23Brine from oil injection well.
24Leaks from waste lagoon.
25Deep-well hazardous waste disposal.
26Water-bearing sandstone.
27Limestone.

22. Chapter 6 –Drinking Water Purification
Aluminum Sulfate

23. Chapter 6 –Drinking Water Purification
A Treatment Plant
1. Intake: Water is taken from the source. Logs, fish
and plants are screened out at the intake and then the
water is drawn into the treatment plant. If the source is
groundwater, the "screening" is done by the soil as the
water travels under the earth's surface. Sometimes
very little treatment is required for groundwater.
2. Chemical Addition: Aluminum sulfate (alum)
polymers and/or chlorine are added to the water.
These kill germs, improve taste and odor, and they
help settle solids still in the water. The water and these
chemicals are then mixed together.
3. Coagulation and Flocculation: Here, the alum and
other chemicals from the chemical addition step cling
to particles in the water. This is called coagulation. It
causes the particles to stick together and form larger
particles called floc.

24. Chapter 6 –Drinking Water Purification
4. Sedimentation: The water and the floc particles
flow into a sedimentation basin. Here the floc settles
to the bottom and is removed from the water.
5. Filtration: From the sedimentation basin, the
water flows through filters. Filters are made of layers
of sand and gravel. The filters are used to remove
any remaining particles left in the water.
6. Disinfection: A small amount of chlorine, or other
disinfecting chemicals, is added. This is used to kill
any remaining germs and to keep the water safe as it
travels to the public. In some water systems,
especially those with groundwater sources, this is the
only treatment provided.

25. Chapter 6 –Drinking Water Purification
7. Storage: The water is placed in a closed tank or
reservoir called a clear well. This allows time for the
chlorine to mix throughout the water in order for
disinfection to take place. The water then flows into
the distribution system.
The water is sampled and tested throughtout the
treatment plant. Sampling is performed to make sure
the processes are working and that the water is safe
before it leaves the plant. In North America,
governments have set standards for drinking water.
When water leaves a treatment plant, it is as clean or
cleaner than required by these standards.

26. LECTURE #6
Chapter 6 –Drinking Water Purification
Municipal Water Treatment (GAC)
City of Oulu (Finland) –
municipal water treatment plant