Tank Spreadsheet v 6 A

Tank Spreadsheet 3/23/2010

Instructions to Users

Guidelines

>The tank turnover time and mixing calculations are not applicable for every tank. The following are guidelines for these calculations:

>Care should be taken to apply these calculations in the following cases:

-- If you do not know the configuration of the tank inlet or if you do not know if there are any baffles inside the tank.

-- If the inlet is located near the tank wall, mixing will be reduced.

-- If the age of the water entering the tank is significantly old, the turnover time will not approximate the total water age in the tank.

Date Modified: Modifications & By Whom:

10/24/2003 LDD modified tank worksheets to simplify data entry requirements. Provided space for up to 15 tank fill periods.

9/13/2004 MWS added guidelines

10/6/2004 MWS added Data Summary worksheet

12/13/2004 MWS added Summary, Prioritization, and Analysis worksheets. Also revised Data Input worksheet's error in turnover time calculations.

1/27/2005 MWS added calculations for rectangular tanks. Made minor modifications to all sheets for increased functionality.

-- Tanks that operate in a fill/ draw mode

-- Tank inlets oriented horizontally or vertically.

-- Tanks that operate in a fill/ draw mode

-- Tanks with any inlet orientation and baffling

Turnover Time Calculation CANNOT Be Used On:

-- If the tank is baffled or has pillars.

-- Flow-through tanks (tanks operating with

simultaneous inflow and outflow)

-- Irregular-shaped tanks.

-- Cylindrical, rectangular, or hydropillar tanks or certain

tanks having SCADA that report changes in volume

(i.e., elliptical or spherical)

-- Under neutrally buoyant conditions (no temperature

difference between the inlet water and tank water)

Tank Mixing Assessment CANNOT Be Done On:

-- Under any buoyancy conditions (temperature

differences between the inlet water and tank water)

>In situations where the tank is not well mixed or when the mixing calculations cannot be used, the tank turnover time calculations only show the average turnover

time of the tank. There may be much older "dead-zones" of water in the tank.

-- If the temperature difference between the water coming into the tank and the water in the tank is significantly different. This may decrease tank mixing due to

buoyancy.

-- Flow-through tanks (tanks operating with

simultaneous inflow and outflow)

>The purpose of this spreadsheet is to summarize tank characteristics, assess water storage tank turnover time and mixing, and determine operational strategies to

improve turnover time and mixing.

>Enter information into the Summary worksheet about the storage tanks.

>Enter data into the Tank worksheets for the storage tanks in the distribution system. Tank diameter, inlet diameter, and water level changes over a period of time

are required inputs. Water system SCADA data is typically used to determine the changes in tank water levels.

>If the tank mixing calculations (in the Tank worksheet) determine that mixing is poor, the Mixing Analysis should be used to determine solutions to improve mixing.

>If the tank turnover time calculations (in the Tank worksheet) determine that turnover time is high, the Turnover Time Analysis should be used to determine

operational changes to improve turnover time.

-- Tanks with a submerged inlet.

-- Cylindrical, rectangular, or hydropillar tanks or tanks

having SCADA that report changes in volume

-- Tanks with any inlet/outlet configuration

Tank Mixing Assessment CAN Be Done On: Turnover Time Calculation CAN Be Used On:

Instructions:

I. Tank Characteristics (See Glossary worksheet for illustrations of Tank Characteristics)

**Data must be entered into this section for the spreadsheet to function.

**Do not enter tank dimensions if the tank is NOT cylindrical, rectangular, or hydropillar.

**Hydropillar tanks can be approximated as cylindrical tanks depending on their operating range. See glossary for illustration.

Tank #1 Tank #2 Tank #3 Tank #4 Tank #5 Tank #6 Tank #7 Tank #8 Tank #9 Tank #10

A.

B.

C.

D1.

D2.

E1.

E2.

E3.

F.

G.

#DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!

The remaining data is automatically calculated based on the data entered above:

Are the turnover time calculations applicable?3

no no no no no no no no no no

Are the mixing equations applicable?4

no no no no no no no no no no

II. Tank Calculations (from Tank Data Input worksheets)

Turnover Time (days)

Mixing Performance Ratio (Measured/ Desired)

Notes:

1. Hydropillar tanks can be approximated as cylindrical tanks depending on their operating range. See glossary for illustration.

2. In flow-through operation water is simultaneously coming into the tank and leaving the tank. In fill-draw operation water is can either be filling the tank or drawing from

the tank at any one time (this is typical of most tanks).

H/D ratio

3. If the tank operates flow-through the turnover time calculations are not applicable.

**If data is missing the reason could be that the tank mixing equations may not be applicable or the tank may not be cylindrical, hydropillar, rectangular, or have SCADA that reports

volume rather than level.

Tank Summary

2. After completing section I, go to the tank worksheets entitled "Tank #1", "Tank #2", etc. Enter the operational data in Step 1 of the worksheet. Once the data is entered in Step 1, proceed to

Step 2 and 3, if appropriate.

3. If the tank calculations in Step 1 determine that turnover time and/or mixing is poor, Step 2 and 3 of the tank worksheet will determine possible ways to improve tank operations. The

calculations analyze current operations and develop operational solutions to decrease water age and increase mixing in the tank.

1. Enter tank characteristics into section I below. Section II and III will be populated automatically when data is entered into the tank worksheets. NOTE: Data inputted by the user are shown

in red. Data must be entered into section I for the spreadsheet to function.

If SCADA/ telemetry is reported in volume,

are the tank mixing equations applicable - see note 4 (y/n)?

Name of Tank

Volume (MG)

Is the tank Cylindrical (C), Rectangular (R),

Hydropillar1 (H), or None of these (n)?

Does the SCADA/ telemetry report tank level

in volume (y/n)?

If the SCADA/ telemetery reports tank level in feet answer question C, then

answer questions E, F, and G. If the SCADA/ telemetry does not report the

tank level in feet, answer "n" in question C and then answer questions D1, D2,

E3, F, and G.

4. The mixing calculations are applicable if the tank shape is cylindrical, rectangular, elliptical, or a hydropillar AND the tank operates fill-draw. The mixing calculations are

not applicable if the tank operates flow-through OR the tank is irregularly shaped.

(all tanks) Is the tank operated fill-draw (fd) or flow-through2 (ft)?

(if cylindrical/hydropillar/) Tank diameter or

(if rectangular) Longest Sidewall length, D (ft)

(If rectangular) Shortest Sidewall length, L (ft)

(all tanks) Inlet Diameter, d (ft)

(all tanks) Maximum Operating Water Depth, H (ft)

Step 1: Data Input- Tank Turnover and Mixing Calculations

Tank Name: 0

Volume, MG: 0

Cylindrical (C), Rectangular

(R), Hydropillar (H), or None of

these (n)? 0.00

If none, does SCADA report

volume (or % full) rather than

level? 0.00

0

0

0

#DIV/0!

Inlet diameter, d: 0.00 ft

Instructions: Enter tank fill data (obtained from plant SCADA) for up to 15 fill periods. Data inputted by the user are shown in red.

Date Time Min Level Max Level Date + Time Delta Time Level Change

Ft Ft Days Ft

1/0/00 0:00 0.0 1

1/0/00 0:00

1/0/00 0:00 2

1/0/00 0:00

1/0/00 0:00 3

1/0/00 0:00

1/0/00 0:00 4

1/0/00 0:00

1/0/00 0:00 5

1/0/00 0:00

1/0/00 0:00 6

1/0/00 0:00

1/0/00 0:00 7

1/0/00 0:00

1/0/00 0:00 8

1/0/00 0:00

1/0/00 0:00 9

1/0/00 0:00

1/0/00 0:00 10

1/0/00 0:00

1/0/00 0:00 11

1/0/00 0:00

1/0/00 0:00 12

1/0/00 0:00

1/0/00 0:00 13

1/0/00 0:00

1/0/00 0:00 14

1/0/00 0:00

1/0/00 0:00 15

1/0/00 0:00

Tank #1 Worksheet

Spreadsheet is not set up for shapes other than

cylindrical, hydropillar, & rectangular unless SCADA

reports tank volume!

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 0.2 0.4 0.6 0.8 1 1.2

Level (f

t/g

al)

Time (days)

Tank #1 Graph

Fill period Low/Min Level High/Max Level Vol at start Vol added Volume drawn Ave Tank Vol

of fill cycle during fill cycle during drain cycle during fill cycle Actual Req'd Fill Time

(ft) (ft) (MG) (MG) (MG) (MG)

Volume Exchange

Fraction (VEF)

Volume Exchange

Fraction (VEF) (days)

1 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a















Turnover Summary

Avg Vol Added in One Fill Period #DIV/0! MG Avg Min Water Level #DIV/0! ft

Avg Vol Drawn in One Drain Period #DIV/0! MG Avg Actual VEF #VALUE!

Avg Fill Time #DIV/0! days Avg VEF Needed for Good Mixing #DIV/0!

Avg Draw Time #DIV/0! days Avg Measured Water Level Change #DIV/0! ft

Avg Fill Rate #DIV/0! gpm #DIV/0! ft

Avg Draw Rate #DIV/0! gpm #DIV/0!

Avg Duration (Fill + Draw Time) #DIV/0! days #DIV/0! inches

Avg Flow Rate into tank #DIV/0! MGD

Avg Tank Vol #DIV/0! MG

Turnover Time #DIV/0! days

#DIV/0!

Desired Water Level Change Needed for

Good Mixing

Inlet Diameter Needed for Good Mixing

#DIV/0!

Mixing Performance Ratio

(Measured/Desired)

Mixing calculations

Dimension-

less Mixing

Time

Mixing Summary

Step 2: Turnover Time & Mixing Analysis

Instructions: Five scenarios are available for experimenting with changing tank operations to improve turnover time. Experiment with lowering the both the Max and Min levels,

only the Min level, and only the Max level. Modify data shown in red. Do not use this analysis if the turnover time equations are not applicable!

These five scenarios are also available for experimenting with reducing inlet diameter to improve mixing. Note that improving the level change will also improve mixing.

Modify data shown in red. Do not use this analysis if the mixing equations are not applicable (H/D>1)!

No Changes Scenario A Scenario B Scenario C Scenario D Scenario E

0 0 0 0 0 0 ft

0 0 0 0 0 0 ft

Inlet Diameter 0.00 ft

High/Max Level FALSE ft

Low/Min Level FALSE ft

Actual Level Change #DIV/0!

Dimensionless Mixing Time #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!Desired Level Change

Needed for Good Mixing #DIV/0!

Pressure Drop After Change

in Min Water Level 0.0 0.0 0.0 0.0 0.0

Fill rate/ Pumping rate #DIV/0! #DIV/0! #DIV/0! #DIV/0! gpmDraw rate/ consumer

demand #DIV/0! #DIV/0! #DIV/0! #DIV/0! gpm

Avg fill time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Avg draw time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Avg volume added during fill #DIV/0! MG

Avg Duration (fill +draw) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Ave Flow Rate #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! MGD

Ave Tank Vol #DIV/0! MGMixing Performance Ratio

(Measured/Desired) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!

Turnover Time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Step 3: Chlorine Residual Analysis

Instructions: Five scenarios are available for estimating the minimum chlorine concentration exiting a completely mixed or plug flow tank during a

drain cycle. This analysis may be able to 1) identify if the performance problem at the tank is due to incomplete mixing, 2) determine the chlorine concentration

needed to enter the tank in order to achieve target chlorine residuals leaving the tank, or 3) determine the chlorine decay rate needed at the tank in order to

achieve target chlorine residuals leaving the tank. Remember - ideal tank performance is complete mixing! Modify data shown in red.

No Changes -

Estimated Current

Conditions Scenario A Scenario B Scenario C Scenario D Scenario E

High/Max Level FALSE 0.00 0.00 0.00 0.00 0.00 ft

Low/Min Level FALSE 0.00 0.00 0.00 0.00 0.00 ft

Mixing Performance Ratio #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!

Turnover Time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! daysChlorine Decay Rate

Constant (determined from

bottle test) (k) day-1

Volume at Start of Fill Cycle

(Ve) #DIV/0! error error error error error MG

Volume at end of fill period

(or at the start of the draw

period) (Vf) #DIV/0! error error error error error MG

Avg fill time (Tf) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Avg draw time (Te) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! daysMaximum time that a water

parcel stays in a plug flow

tank (Tmax) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Concentration entering the

tank (from field data) (Ce) mg/LComplete Mixing: Minimum

concentration leaving the

tank1, 2

#DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! mg/LPlug Flow: Minimum


tank1, 2

#DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! mg/L

1. Equation from p. 211 - Water Quality Modeling in DS Storage Tanks" AWWARF study

2. The user should assume that when the tank is well mixed (mixing PR >= 1) the minimum concentration leaving the tank is close to the completely mixed result. If

the tank is poorly mixed (mixing PR < 1) the user should be cautious about using the plug flow result to determine the minimum concentration leaving the tank.

Tanks can operate in many different and unpredictable ways. If the tank is not baffled (like a clearwell) or specifically designed to be plug flow, then the tank

operation is probably not plug flow. In most cases, if the tank is not well mixed (mixing PR < 1) there may be some areas of the tank volume that are mixed (e.g.,

close to the inlet zone) and other areas (i.e., dead-zones) that are unmixed and probably have an undetectable chlorine residual. If this is the case, neither the plug

flow nor completely mixed result for minimum concentration leaving the tank is applicable.

Tank #1 Worksheet