Transcript New Treatment Technologies

What’s new in Water Treatment?
Coagulants and Filter Aids
Sticky Particles vs. Sticky Media
Particle Capture Efficiency
Sand filters are inefficient capturers of
particles
 Particles come into contact with filter media
surfaces many times, yet it is common for
filters to only remove 90% - 99% of the
particles.
 Failure to capture more particles is due to
ineffective attachment (not limited by
transport)

Techniques to Increase Particle
Attachment Efficiency

Make the particles stickier
 The
technique used in conventional water
treatment plants
 Control coagulant dose and other coagulant aids
(cationic polymers)

Make the filter media stickier
 potato
starch?
Sticky Media vs. Sticky Particles

Sticky Media



Potentially treat filter
media at the beginning
of each filter run
No need to add
coagulants to water for
low turbidity waters
Filter will capture
particles much more
efficiently

Sticky Particles

Easier to add coagulant
to water than to coat
the filter media
How can we make filter media sticky?
Why do slow sand filters work?
Slow sand filters don’t use any coagulants,
yet their performance improves with time
 Their improved performance is due to
natural particulate matter that is captured by
the filter
 What is it about this particulate matter that
makes the filters work better?

Role of Natural Particulates in
SSF
Could be removal by straining
 But we are removing particles 1 mm in
diameter!
 To remove such small particles by straining
the pores would have to be close to 1 mm
and the head loss would be excessive
 Removal must be by attachment to the
sticky particles!

Particle Removal by Size
1
control
3 mM azide
0.1
0.01
0.001
0.8 1
10
Particle diameter (µm)
Research project in CEE 453 in
2000
Successfully extracted a coagulant from
Cayuga Lake Seston using 1.0 N HCl
 The CLSE fed filters removed up to
99.9999% of the influent coliforms!!!!
 Analysis of the CLSE

 Nonvolatile
solids were 44% of the TSS
 Volatile solids were 56% of the TSS
 Aluminum was dominant metal
E. coli removal as a function of
time and CLSE application rate
1
control
0.1
0.62
0.01
E. coliout
E. coliin
3.1
0.001
15
0.0001
g
m 2 ×day
end azide
0.00001
0.000001
0.0000001
0
2
4
6
time (days)
8
10
Horizontal bars indicate
when CLSE feed was
operational for each filter.
Head loss produced by CLSE
control
0.62
g
3.1 m 2 ×day
15
end azide
head loss (m)
1.2
1
0.8
0.6
0.4
0.2
0
0
2
4
6
time (days)
8
10
What do we know about this
Polymer?
Soluble at very low (<1) and at very high
(>13) pH
 Forms flocs readily at neutral pH
 Contains protein (amino acids)

 In
acid solution amino acids are protonated and
exist as cations
 In basic solution amino acids are deprotonated
and exist as anions
Future Work



Identify the amino acids
Develop a better source of the protein coagulant
(synthetic, bacteria culture, algae culture?)
Develop application techniques to optimize filter
performance




How can we coat all of the media?
Will the media remain sticky through a backwash?
Will it be possible to remove particles from the media
with a normal backwash?
What are the best ways to use this new coagulant?
Polymer in a void between glass
beads
Polymer in a void between glass
beads
Polymer on and bridging between
glass beads
Polymer Bridge between Glass
Beads
Dissolved Air Flotation

Shown to be more effective at removing
Cryptosporidium than conventional sedimentation


DAF clarification performed better than lamella
sedimentation and consistently resulted in lower
turbidity levels and particle counts.
Journal AWWA - Giardia and Cryptosporidium
Removals by Clarification and Filtration Under
Challenge Conditions
Vol. 92 - No. 12
Waterborne disease outbreaks
caused by distribution system
deficiencies



Gunther F. Craun and
Rebecca L. Calderon
JOURNAL AWWA
September 2001
Vol. 93, No. 9
pp. 64–75
Distribution system contamination has resulted in a significant number of waterborne
disease outbreaks in the United States. A review of the 113 distribution-associated
outbreaks reported over the past 30 years finds 498 hospitalizations and nine deaths.
Since 1996, distribution system deficiencies have caused 45% of all outbreaks reported
in community water systems. Most distribution-associated outbreaks were attributable to
chemical and microbial contamination from cross-connections and backsiphonage.
Preventing contamination of the distribution system is key to reducing the risk of
waterborne disease outbreaks. Important preventive steps include maintaining adequate
water pressure throughout the system; identifying and replacing older, leaking water
mains; maintaining a chlorine residual and routinely monitoring the residual; adopting
cross-connection control programs; inspecting storage facilities on a routine basis;
adequately disinfecting after system repairs; and increasing corrosion control efforts.
An aging water system infrastructure renders the United States even more vulnerable to
the risk of waterborne disease outbreaks. More regulations may be required to prevent
these outbreaks unless water suppliers take action to reduce distribution system
contamination and sufficient funds are allocated for system maintenance, repair, and
replacement.