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Tank Spreadsheet 3/23/2010Instructions to Users

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

>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.

Guidelines

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

Tank Mixing Assessment CAN Be Done On: Turnover Time Calculation CAN Be Used On:-- Tanks that operate in a fill/ draw mode -- Tanks that operate in a fill/ draw mode-- Tank inlets oriented horizontally or vertically. -- Tanks with any inlet orientation and baffling

-- Tanks with a submerged inlet. -- Tanks with any inlet/outlet configuration

Tank Mixing Assessment CANNOT Be Done On: Turnover Time Calculation CANNOT Be Used On:

-- Irregular-shaped tanks.-- If the tank is baffled or has pillars.

>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 guidelines10/6/2004 MWS added Data Summary worksheet12/13/2004 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.

>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 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 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.

-- Cylindrical, rectangular, or hydropillar tanks or certain tanks having SCADA that report changes in volume (i.e., elliptical or spherical)

-- Cylindrical, rectangular, or hydropillar tanks or tanks having SCADA that report changes in volume

-- Under neutrally buoyant conditions (no temperature difference between the inlet water and tank water)

-- Under any buoyancy conditions (temperature differences between the inlet water and tank water)

-- Flow-through tanks (tanks operating with simultaneous inflow and outflow)

-- Flow-through tanks (tanks operating with simultaneous inflow and outflow)

-- 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.

>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.

Tank Summary

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. Name of TankB. Volume (MG)

C.

D1.

D2.

E1.

E2. (If rectangular) Shortest Sidewall length, L (ft)E3. (all tanks) Inlet Diameter, d (ft)

F. (all tanks) Maximum Operating Water Depth, H (ft)G.

H/D ratio #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:no no no no no no no no no nono 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.

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

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.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.

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.

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 SCADA/ telemetry is reported in volume, are the tank mixing equations applicable - see note 4 (y/n)?

(if cylindrical/hydropillar/) Tank diameter or (if rectangular) Longest Sidewall length, D (ft)

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

Are the turnover time calculations applicable?3

Are the mixing equations applicable?4

**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.

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).

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.

Tank #1 WorksheetStep 1: Data Input- Tank Turnover and Mixing Calculations

Tank Name: 0Volume, MG: 0

0.00

0.00

0

0

0

#DIV/0!

Inlet diameter, d: 0.00 ft

Date Time Min Level Max Level Date + Time Delta Time Level ChangeFt Ft Days Ft

12/30/99 0:00 0.0 112/30/99 0:0012/30/99 0:00 212/30/99 0:0012/30/99 0:00 312/30/99 0:0012/30/99 0:00 412/30/99 0:0012/30/99 0:00 512/30/99 0:0012/30/99 0:00 612/30/99 0:0012/30/99 0:00 712/30/99 0:0012/30/99 0:00 812/30/99 0:0012/30/99 0:00 912/30/99 0:0012/30/99 0:00 1012/30/99 0:0012/30/99 0:00 1112/30/99 0:0012/30/99 0:00 1212/30/99 0:0012/30/99 0:00 1312/30/99 0:0012/30/99 0:00 1412/30/99 0:0012/30/99 0:00 1512/30/99 0:00

Cylindrical (C), Rectangular (R), Hydropillar (H), or None of

these (n)?

If none, does SCADA report volume (or % full) rather than

level?

Spreadsheet is not set up for shapes other than cylindrical, hydropillar, & rectangular unless SCADA reports tank volume!

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

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

2

4

6

8

10

12

Tank #1 Graph

Time (days)

Leve

l (ft

/gal

)

Fill period Low/Min Level High/Max Level Vol at start Vol added Volume drawn Ave Tank Vol Mixing calculationsof fill cycle during fill cycle during drain cycle during fill cycle Actual Req'd Fill Time

(ft) (ft) (MG) (MG) (MG) (MG) (days)### 1 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 2 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 3 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 4 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 5 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 6 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 7 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 8 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 9 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 10 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 11 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 12 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 13 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 14 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a### 15 0.00 0.00 error error n/a #VALUE! #DIV/0! #DIV/0! n/a

Turnover Summary Mixing SummaryAvg Vol Added in One Fill Period #DIV/0! MG Avg Min Water Level #DIV/0! ftAvg 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 Inlet Diameter Needed for Good Mixing #DIV/0! inchesAvg Flow Rate into tank #DIV/0! MGD

#DIV/0!

Avg Tank Vol #DIV/0! MGTurnover Time #DIV/0! days

#DIV/0!

Dimension-less Mixing

TimeVolume Exchange

Fraction (VEF)Volume Exchange

Fraction (VEF)

Desired Water Level Change Needed for Good MixingMixing Performance Ratio (Measured/Desired)

L51

Function of diameter of the inlet pipe and the volume at the beginning of the fill cycle.

C76

Average time between the end of last fill cycle and the beginning of the the next fill cycle.

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,

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.

No Changes Scenario A Scenario B Scenario C Scenario D Scenario E0 0 0 0 0 0 ft0 0 0 0 0 0 ft

Inlet Diameter 0.00 ftHigh/Max Level 0.00 ftLow/Min Level 0.00 ft

Actual Level Change #DIV/0!

Dimensionless Mixing Time #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!

#DIV/0!

0.0 0.0 0.0 0.0 0.0Fill rate/ Pumping rate #DIV/0! #DIV/0! #DIV/0! #DIV/0! gpm

Draw rate/ consumer demand #DIV/0! #DIV/0! #DIV/0! #DIV/0! gpmAvg fill time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! daysAvg draw time #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

Avg volume added during fill #DIV/0! MGAvg Duration (fill +draw) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! daysAve Flow Rate #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! MGDAve Tank Vol #DIV/0! MG

#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 concentrationneeded 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

Scenario A Scenario B Scenario C Scenario D Scenario EHigh/Max Level 0.00 0.00 0.00 0.00 0.00 0.00 ftLow/Min Level 0.00 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! days

#DIV/0! error error error error error MG

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!

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

Desired Level Change Needed for Good Mixing

Pressure Drop After Change in Min Water Level

Mixing Performance Ratio (Measured/Desired)

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

No Changes - Estimated Current

Conditions

Chlorine Decay Rate Constant (determined from bottle test) (k) day-1

Volume at Start of Fill Cycle (Ve)

#DIV/0! error error error error error MGAvg fill time (Tf) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! daysAvg draw time (Te) #DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

#DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! days

mg/L

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

#DIV/0! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! mg/L1. Equation from p. 211 - Water Quality Modeling in DS Storage Tanks" AWWARF study

Volume at end of fill period (or at the start of the draw period) (Vf)

Maximum time that a water parcel stays in a plug flow tank (Tmax)

Concentration entering the tank (from field data) (Ce)Complete Mixing: Minimum concentration leaving the tank1, 2

Plug Flow: Minimum concentration leaving the tank1, 2

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

Draw Time

(days)n/an/an/an/an/an/an/an/an/an/an/an/an/an/an/a



0.00

0.00

0

0

0

#DIV/0!



12/30/99 0:00 0.0 112/30/99 0:0012/30/99 0:00 212/30/99 0:0012/30/99 0:00 312/30/99 0:0012/30/99 0:00 412/30/99 0:0012/30/99 0:00 512/30/99 0:0012/30/99 0:00 612/30/99 0:0012/30/99 0:00 712/30/99 0:0012/30/99 0:00 812/30/99 0:0012/30/99 0:00 912/30/99 0:0012/30/99 0:00 1012/30/99 0:0012/30/99 0:00 1112/30/99 0:0012/30/99 0:00 1212/30/99 0:0012/30/99 0:00 1312/30/99 0:0012/30/99 0:00 1412/30/99 0:0012/30/99 0:00 1512/30/99 0:00


these (n)?


level?



0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

2

4

6

8

10

12

Tank #2 Graph

Time (days)

Leve

l (ft

/gal

)







#DIV/0!


#DIV/0!


TimeVolume Exchange


Fraction (VEF)


L51


C76
