Simple Ways To Enhance Your Water Treatment ... - Ohiowater.org

OTCO Class III & IV Workshop
August 18, 2011
Simple Ways to Enhance
Your WTP‟s CT Capacity
Tim Wolfe
MWH Americas
Water Practice Leader

Items to be Discussed Today . . .
• CT in Ohio EPA‟s Approved Capacity Document
• Optimizing CT Credit in Your Clearwells
• Lima‟s CT Credit Enhancements
• Avon Lake‟s Seasonal CT Credits

Clarified Need to Match (Normalize) Clearwell Component Capacity (i.e.,
CT Capacity) with Other Components of the Water Treatment Plant (WTP)
OHIO EPA‟s APPROVED
CAPACITY DOCUMENT

Ohio EPA Plan-approval Letters
Now State the:
• Approved Capacity of the “Water-supply Source” is XX
MGD – and the Limiting component on which the approved
capacity is based,
• Approved Capacity of the “WTP” is YY MGD – and the
Limiting component on which the approved capacity is based,
and
• Approved Capacity of the “Water System” is XX or YY
MGD – i.e., the smaller of the approved capacities for the
Water-supply Source and WTP
4

“Components” of
Water Treatment Plants (WTPs)
• A unit-treatment process (e.g., pre-sedimentation,
rapid-mix, flocculation, sedimentation, filtration,
stabilization, etc.);
• Essential chemical storage-and-feed facilities;
• Disinfection (e.g., chorine, chloramines, chlorine
dioxide, ozone or UV generation and/or contacting
facilities); and
• WTP pumping (e.g., intermediate pumping
between components within the WTP, finishedwater
pumping to convey finished water to the
distribution system, etc.).
5

“Production” is the rate at which
finished water leaves the WTP
• “Customer water demands” are:
– Commercial and Industrial (Large users)
– Residential
– Public use (Billed or Unbilled)
• Most of the difference between WTP Production
and Customer Demands is contributed to
or supplied by distribution storage
6

“Production” . . . (cont)
• “Other items” that cause a difference between WTP
Production and Customer Demands are:
– Accounted-for and Unaccounted-for Distribution-system
Water losses
– Inaccurate meters
– Etc.
7

Each “Part” of a Water System Plays a
Role in Supplying Customer Demands
Source
Avg.-day, or
Max.-day
Surface
Water
Lakes
Reservoirs
Rivers
Ground
Water
Aquifers
WTP
Max.-day
Water
Treatment
Disinfection &
Finished-water
Pumping
Line between Production
and Demands can be Blurry
Instantaneous-peak,
Fire-flow,
Pk.-hour Demands,
Etc.
Comm/Ind
Residential
Public use
Losses
Inaccurate
Meters
Distribution System
8

Distribution Storage is the Buffer
Between Production and Demands
Avg.-day, or
Max.-day
Surface
Water
Lakes
Reservoirs
Rivers
Ground
Water
Aquifers
WTP
Production
Max.-day
Water
Treatment
Disinfection &
Finished-water
Pumping
Pk
hr
Customer
Demand, etc.
Instantaneous-peak,
Fire-flow Demands
Storage
Comm/Ind
Residential
Public use
Losses
Inaccurate
Meters
Distribution System
9

Typical Ratios of Customer Demand
to WTP Production
• Avg.-day Demand
Avg.-day Production = 1
• Max.-day Demand
Max.-day Production = approx. 1
• Pk.-hour Demand
Pk.-hour Production = > 1
Most of the difference between Demand and Production is
contributed to or supplied by distribution-system storage
10

In Essence:
Distribution-system Storage . . .
. . . Provides the difference between:
• The large, customer demands (e.g., Pk.-hour,
Instantaneous-peak and Fire-flow), etc.
AND
• The smaller, more constant, rate at which water is
produced on any given day at the WTP (i.e.,
Production) to supply these various Customer
Min.-day, Avg.-day, or Max.-day demands
11

Storage Buffers Up- & Down-stream
Flow Rates between Components
Avg.-day
Max.-day
Max.-day
Pk.
hour
Water
Treatment
Source-water
Storage
Clearwell
Storage
Finished-water
Pumping
“Source-water storage” allows upstream Water-supply source components
to be designed to meet Avg.-day production (not Max.-day rates).
Likewise, “Clearwell storage” allows upstream WTP components
to be designed to meet Max.-day production (not Pk.-hour rates).
12

WTP Production Projections
for a Growing Water System
Finished-water Pumping
Finished
Water
Production
Projections
( MGD )
15.0
13.5
10.0
7.5
Pk.-hour Production
Pk.-hour of Treatment
CT Criteria for Clearwells
Max.-day Production
Most WTP Components
Avg.-day Production
Most Source Components
0
Today
Design
Year
13

Productions are Normalized around Max.-day
Production to Calculate Equiv. Max.-day Cap.
Finished
Water
Production
Projections
( MGD )
15.0
13.5
10.0
7.5
Pk.-hour Production
Pk.-hour of Treatment
Max.-day Production
Avg.-day Production
0
Today
Design
Year
14

For Water-supply Components that
Supply Avg.-day WTP Production . . .
. . . The Component Capacity is converted to an
“Equivalent Max.-day Capacity” by:
„Multiplying‟ the Component Capacity by the ratio of
Max.-day to Avg.-day production:
E.g., an aquifer’s safe yield (i.e., component capacity) is 5.0
MGD, and the water system’s ratio of Max.-day to Avg.-day
production is 1.25:
5.0 MGD Avg.-day 1.25 Max.-day
------------------------- X ------------------- = 6.25 MGD Equiv. Max.-day
1 Avg.-day
15

For WTP Components that Supply
Pk.-hr WTP Production . . .
. . . The Component Capacity is converted to an
“Equivalent Max.-day Capacity” by:
„Dividing‟ the Component Capacity by the ratio of
Pk.-hr to Max.-day production:
E.g., the Component (CT) capacity for the Clearwell
is 12.5 MGD for a 10-MGD WTP, and the water
system’s ratio of Pk.-hr “production” to Max.-day
production is 1.5:
12.5 MGD Pk.- hr X Max.-day = 8.3 Equiv. Max.-day
1 1.5 Pk.-hr
16

The Clearwells for this 10-MGD WTP are the
Limiting Component in Year X
15.0
Pk.-hour Production
Finished
Water
Production
Projections
( MGD )
12.5
10.0
8.3
7.5
Max.-day Production
Avg.-day Production
0
Today
Year
X
Design
Year
17

YES – a Clearwell (i.e., CT capacity) can be a
WTP‟s Limiting Component
First thing this water system can do to increase Component
capacity of the Clearwell is to use Pk.-hr of Treatment instead
of Pk.-hour Production for daily CT calculations
(i.e., Production generally > Treatment during Pk.-hr conditions,
and Water level in Clearwell is typically dropping)
Pk.-hr of
Treatment
Pk.-hr
Production
CT = residual disinfectant Concentration x effective contact Time
T is based on pk.-hr of treatment and corresponding clearwell level
18

Using Pk.-hr treatment Increases
Equiv. Max.-day from 8.3 to 9.3 MGD
I.e., the CT capacity of the Clearwell is still 12.5 MGD,
but the water system’s ratio of Pk.-hr “treatment” to
Max.-day production is 1.35:
13.5 MGD Pk.- hr Trtmnt = 1.35
10.0 MGD Max.-day
12.5 MGD Pk.- hr X Max.-day = 9.3 Equiv. Max.-day
1 1.35 Pk.-hr
19

And . . . The Clearwell CT Capacity
now becomes Limiting in Year Y
Finished
Water
Production
Projections
( MGD )
15.0
13.5
12.5
10.0
9.3
7.5
Pk.-hour Production
Pk.-hour Treatment
Max.-day Production
Avg.-day Production
0
Today
Year
Y
Design
Year
20

To Increase the CT Capacity, the
Water System could also . . .
• Increase the “C” of CT by increasing the free
chlorine residual (i.e., CT values req’d are higher,
but DBPs don’t form as readily in the winter)
• Increase the “T” of CT by maintaining a higher
water level in the Clearwells (e.g., install VFDs on
finished-water pumps)
• Increase the “T” of CT by increasing the effective
volume factor, EVF, of the Clearwells (e.g., install
baffles, etc.)
21

Additional Baffles Increased the
EVF from 0.4 to 0.6 and CT Cap.
I.e., the Equiv. Max.-day capacity of the Clearwell is
9.3 MGD, but the EVF is now 0.6 instead of 0.4:
9.3 MGD Equiv. Max.-day X 0.6 = 14.0 Equiv. Max.-day
1 0.4
Now – the Clearwell component capacity no longer limits the
Approved Capacity of this 10-MGD WTP
22

To Increase the Approved Capacity,
the Water System could also . . .
• Decrease the “Ratio” of Pk.-hour of treatment to
Max.-day water production (e.g., install VFDs on
both source-water and finished-water pumps),
• Decrease the “Ratio” of Pk.-hour water production
to Max.-day water production (e.g., construct
additional distribution-system storage),
• Request a “seasonal CT” approved capacity for
the Clearwells (particularly if the Summer, Max.-
day water production is significantly larger than the
Winter, Max.-day water production)
23

OPTIMIZING CT CREDIT IN
YOUR CLEARWELLS

Effective Volume Factor (EVF)
Increasing Effective Volume
Factor (EVF) – Baffles
0.8
0.6
0.4
Available on the Ohio EPA Website
0.2
10:1 20:1 30:1 40:1
Length to Width (L:W) Ratio

Typical Baffled Clearwell
length of pass ( l ) = 10 W
From
the
Filters
Baffles
Width of pass ( W ) = W
Total Length ( L ) = 3 ( l ) = 3 ( 10 W ) = 30 W
F-w
Pumps
Side Water Depth ( SWD ) = 1.25 W
From
the
Filters
Baffles
3 W
Length to Width ( L : W ) Ratio = 30 : 1

Increasing EVF
Flow-Through Inlet Wall
8 to 10 %
of the wall
is openings
for the influent
to the clearwell
to flow through

Inlet Wall Installed near Point of
Clearwell Influent Flow
length of pass ( l ) = 10 W
Flow-Through Inlet Wall
W
Total Length ( L ) = 3 ( l ) = 3 ( 10 W ) = 30 W
Side Water Depth ( SWD ) = 1.25 W
3 W
Flow-Through Inlet Wall
Length to Width ( L : W ) Ratio = 30 : 1

Increasing EVF - Turning Vanes
length of pass ( l ) = 10 W
W
Turning Vanes
Total Length ( L ) = 3 ( 10 W ) = 30 W
Side Water Depth ( SWD ) = 1.25 W
Turning Vanes
3 W
Length to Width ( L : W ) Ratio = 30 : 1

Increasing EVF - Summary
Bottom Line is to Increase EVF to a value as
close to 1 as possible:
By
• Maximizing plug-flow regions
And
• Minimizing completely-mixed flow regions
• Minimizing dead spaces

LIMA‟s CT CREDIT
ENHANCEMENTS

Lima is Installing Post-filter GAC to Control
T&O and as a DBP Buffer (i.e., to meet LRAA)
SMALL CLEARWELL
To
Distribution
0-3 MGD
LARGE
CLEARWELL
EVF = 0.2
EVF = 0.375
0-17 MGD
From
Filters
OLD CLEARWELL
Flow
Control
0-20 MGD New Baffles
GAC
0-40 MGD
EVF = 0.3

Finished-
Water
Pump Sta.
Filters, and
Clearwells
Underneath
New GAC
Contactors
Location
Old
Clearwell

Existing Clearwell System
Presents Some Challenges
To Lima‟s Distribution
System
Finished-water
Pump Station
Large
Clearwell
No. 2
From the
Dual-media
Filters
Small
C.W. No. 1
Old Clearwell No. 3
has same influent &
effluent pipe
Old
Clearwell
No. 3
High chlorine residuals required to meet winter-time CT values.

Lima‟s WTP has an Approved
Capacity of 30 MGD
Projected, Design-year Parameters:
– Pk.-hour production = 40.0 MGD *
– Max.-day production = 30.0 MGD
– Avg.-day production= 22.5 MGD
= 1.33
= 1.33
* For calculation of daily CT values, the Pk.-hour of
treatment (i.e., clearwell influent) is assumed to be
equal to Pk.-hour production (i.e., clearwell effluent, or
the finished-water pumping rate)

Intermediate Pumping was Required @ Lima
WTP to Convey Filter Effluent through GAC
Two Clearwells No. 1 & 2 located beneath filters
Ten (10)
Dual-Media
Filters
Four (4) New, GAC Contactors
(with 10 ft depth of GAC)
New, 36-in. tie-in with two
Clearwells beneath filters
New, Intermediate Pump-station
New, 36-in. tie-in
With Old Clearwell No. 3

Intermediate Pumping Presented
Opportunity to Enhance CT Cap.
– New 36-in. pipeline from GAC to old clearwell No. 3:
• eliminates potential T&O issues
• allows clearwells No. 1 – 3 to be operated in series
– New 36-in. pipeline from GAC to small clearwell No. 1:
• allows clearwells No. 1 & 2 to be operated in parallel with old
clearwell No. 3
– Control valve with flow meter in small clearwell No. 1
influent pipe:
• allows clearwells to be isolated and cleaned in the summer

Finished-
Water
Pump Sta.
Filters, and
Clearwells
Underneath
New GAC
Contactors
Location
Old
Clearwell
New 36-in. dia.
Connection to
Old Clearwell

Benefit / Cost Ratio for these
Additional Pipelines was Significant
Finished-water
Pump Station
To Lima‟s
Distribution
System
Large
Clearwell
No. 2
Small
C.W. No. 1
New,
36-in. Pipeline
Old Clearwell
No. 3
From GAC

Baffling of Old CW No. 3 and Large CW No. 2
Provided a True 30-MGD Approved Capacity
– Baffling of old clearwell No. 3 increases effective
volume factor (EVF) to 0.3 without a tracer study (i.e.,
length-to-width [L:W] ratio = 10.5)
– Baffling of large clearwell No. 2 increases EVF to 0.375
without a tracer study (L:W ratio = 14.5)

Pipelines and Baffles Provide Several
Advantages for CT Capacity @ Lima WTP
Finished-water
Pump Station
To Lima‟s
Distribution
System
From GAC
Large
Clearwell
No. 2
Small
C.W. No. 1
Recommended
Baffles
New,
36-in. Pipeline
Flow in
only one
direction
Old Clearwell
No. 3

Design-year Winter CT values can be met at
a Cl 2 Residual of only 1.8 mg/L
• CT CALCULATIONS
– Worst-Case Conditions:
• Water Temperature (C) = 4
• Max pH Value > 9
• Cl2 residual (mg/L) =1.8
– Max CT Value Required – Winter (mg/L-min) = 63.3
• CT values achieved at 40 MGD (Design-year,
Pk.-hour production for Lima‟s 30-MGD WTP):
– Clearwells in Series: 64.7 mg/L-min
– Clearwells in Parallel: 63.3 mg/L-min

Clearwell Flow-path Changes
Provide Lima Advantages:
– Increase currently limited CT capacity of existing
Clearwells (i.e., a cost-effective, side-benefit since
intermediate pumping is required anyway for the postfilter,
GAC adsorption units)
– Eliminate dead-spaces in existing, Old Clearwell No. 3
(i.e., GAC-treated water would now enter and exit Old
Clearwell No. 3 at different points)
– Allow a Clearwell to be taken out-of-service for
maintenance during warm weather (i.e., Since CT
values are easier to meet in warm weather, and
Clearwells can now be operated in parallel)

AVON LAKE‟s SEASONAL CT
CREDITS

Avon Lake Municipal Utilities Serves the
City and Numerous Other Communities
Avon
Lake‟s
WTP
Avon Lake‟s
Distribution
System
RLCWA‟s
Extended
Distribution
System
Served
by Avon Lake

Avon Lake‟s WTP Serves a System with
Growing Estimated Demands (Max.-day)
Year
City’s
System
Extended
System
Total
2000 5.0 26.6 31.6
2005 5.1 31.7 36.8
2010 5.3 36.6 41.9
2015 5.4 41.6 47.0
2020 5.6 46.5 52.1

Summer / Winter Approved Capacities
were in Place for Avon Lake‟s WTP
Based on a full-scale Demonstration study:
• The Summer approved capacity was 40 MGD
• The Winter approved capacity was 36 MGD
(i.e., winter water production was not yet high
enough to demonstrate 20 MGD through one of
the two existing, 18-MGD rapid-mix units)

CT is more difficult to meet in the Winter
• Winter CT req’d = 51 mg/L-min
• Summer CT req’d = 27 mg/L-min
• pH = 8
• Temp: Winter = 0.5 C Summer = 10 C
• Chlorine residual = 1.1 mg/L
• 0.5-log inactivation of Giardia

Winter Clearwell Component Capacity was
Limiting WTP Capacity
Volume (MG)
(@ min. Depth)
Clearwells Clearwells All
1-4 5-6 Clearwells
0.4 1.0 1.4
E.V.F 0.2 0.5
Max CT Req’d 51 51
Component
Cap. (MGD)
5 40 45

Equivalent Max.-day Capacities were really
Challenging
• Pk.-hour to Max.-day Ratio = 1.35
• Therefore, Equiv. Max.-day Capacities were:
45 MGD Max.-day
X
1 1.35 Pk.-hour
= 33 MGD (winter)
85 MGD Max.-day
X
1 1.35 Pk.-hour
= 63 MGD (summer)

Without Seasonal Capacities: Ohio EPA
Plan-approval Letter would have Stated . . .
• Approved Capacity of Pretreatment at the WTP is 36 MGD
• Equiv. Max.-day CT Capacity of the Clearwells is 33 MGD
• Approved Capacity of WTP is 33 MGD
51

With Seasonal Capacities:
Ohio EPA Plan-approval Letter Stated . . .
• Approved Capacity of Pretreatment at the WTP is 40 MGD
Summer
• Approved Capacity of Pretreatment at the WTP is 36 MGD
Winter
• Equiv. Max.-day CT Capacity of the Clearwells is 63 MGD
Summer
• Equiv. Max.-day CT Capacity of the Clearwells is 33 MGD
Winter
• Approved Capacity of WTP is 40 MGD Summer
• Approved Capacity of WTP is 33 MGD Winter
52

First Tracer Study was Performed
on an Isolated Clearwell 5
Sampling
Point
Central
High
North
High
4
3
2
Clearwells
1
5 6
F: 0 - 1.0 mg/L
Sampling
Point
From Filters

8:00
8:30
9:00
9:30
10:00
10:30
11:00
11:30
12:00
12:30
13:00
13:30
14:00
C/Co
1
Clearwell 5: Graphical Method
0.9
0.8
0.7
E.V.F. = 1.80 / 2.47 hrs = 0.73
0.6
0.5
0.4
0.3
0.2
T= 1.80 Hrs
0.1
0
Time

log(1-C/Co)
0.0
Clearwell 5: Numerical Method
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
E.V.F. = 0.785
-0.8
-0.9
-1.0
-1.1
-1.2
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
t/T

Tracer Study on Clearwells 1 – 4
was Performed Next
Central
High
F 0.5 mg/L
North
High
4
3
Sampling
Point
2
Clearwells
1
5 6
Sampling
Point
F 0.8 mg/L
From Filters

12:00
12:30
13:00
13:30
14:00
14:30
15:00
15:30
16:00
16:30
17:00
17:30
18:00
18:30
19:00
19:30
20:00
20:30
21:00
21:30
22:00
Fluoride (mg/L)
Start 13:50
15:22 (T10=92 min.)
1.4
Clearwells 1 - 4: Graphical Method
1.3
1.2
1.1
1
0.9
10% of Test Range
0.8
0.7
0.6
E.V.F. = 92 / 168 min = 0.55
0.5
Time
Influent Effluent Avg. Inffl. 90% Retention Curve

log(1-C/Co)
0
Clearwells 1 - 4: Numerical Method
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
E.V.F. = 0.55
-0.7
-0.8
-0.9
-1
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6
t/To
log(1-C/Co) Linear T10

EVFs and Clearwell Component Capacity
Increased After Tracer Studies
Volume (MG)
(@ min. Depth)
Clearwells Clearwells All
1-4 5-6 Clearwells
0.4 1.0 2.2
E.V.F. 0.55 0.7
Max CT Req’d 51 51
Component
Cap. (MGD)
14 55 69

Equivalent Max.-day Capacities were No
Longer Challenging
• Pk.-hour to Max.-day Ratio = 1.35
• Therefore, Equiv. Max.-day Capacities are:
69 MGD Max.-day
X
1 1.35 Pk.-hour
= 51 MGD (winter)
130 MGD Max.-day
X
1 1.35 Pk.-hour
= 96 MGD (summer)

Without Seasonal Capacities: Ohio EPA
Plan-approval Letter would have Stated . . .
• Approved Capacity of Pretreatment at the WTP is 36 MGD
• Equiv. Max.-day CT Capacity of the Clearwells is 51 MGD
• Approved Capacity of WTP is 36 MGD
61

With Seasonal Capacities:
Ohio EPA Plan-approval Letter Stated . . .
• Approved Capacity of Pretreatment at the WTP is 40 MGD
Summer
• Approved Capacity of Pretreatment at the WTP is 36 MGD
Winter
• Equiv. Max.-day CT Capacity of the Clearwells is 96 MGD
Summer
• Equiv. Max.-day CT Capacity of the Clearwells is 51 MGD
Winter
• Approved Capacity of WTP is 40 MGD Summer
• Approved Capacity of WTP is 36 MGD Winter
62

. . . Items that were Discussed Today
• CT in Ohio EPA‟s Approved Capacity Document
• Optimizing CT Credit in Your Clearwells
• Lima‟s CT Credit Enhancements
• Avon Lake‟s Seasonal CT Credits