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STATE POINT ANALYSIS

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					  STATE POINT
   ANALYSIS
WesTech Engineering, Inc.
Salt Lake City, Utah, USA


                            1
    Simplified Activated
    Sludge Flow Sheet

                   Q + RAS                 Q
Q     Aeration
      Basin                  Clarifier

                 RAS

                                     WAS



    State Point Analysis

                                               2
      Key Parameters used in
       State Point Analysis
Factor / Parameter                  Symbol
Influent flow rate                    Q
Return activated sludge flow rate     RAS
Mixed liquor concentration            Xmlss
Sludge settling characteristics       V o, k
Clarifier surface area                A

                                           3
                        State Point Diagram
              8.0
              7.0
                            Solids Flux Axis
G, Kg/m2-hr




              6.0
              5.0
              4.0
              3.0
              2.0                   Solids Concentration Axis
              1.0
              0.0
                    0   2   4   6     8    10 12   14   16   18   20
                                          X, g/l

                                                                       4
         What is Solids Flux?
         Solids flux is the movement
         of solids through a clarifier
Solids Flux = mass per unit area per unit time
                kg / m2 - hr


         Solids Loading Rate (SLR)
         is one type of solids flux
                                             5
                        State Point Diagram
                        We will plot three elements
              8.0
              7.0
                            - Overflow rate line
G, Kg/m2-hr




              6.0
              5.0           - Underflow rate line
              4.0           - Settling flux curve
              3.0
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18   20
                                        X, g/l

                                                                     6
                        State Point Diagram
              8.0
              7.0
G, Kg/m2-hr




              6.0
                                        Overflow rate line
              5.0
              4.0                       Slope = SOR = Q/A
              3.0
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16     18   20
                                        X, g/l

                                                                       7
                        State Point Diagram
              8.0
              7.0                                   Xmlss(Q+RAS)
                            Solids loading rate
G, Kg/m2-hr




              6.0                                         A
              5.0
              4.0                     State Point
              3.0                          Underflow rate line
              2.0
              1.0                            Slope = SUR = RAS/A
              0.0
                    0   2     4   6    8    10 12    14   16   18   20
                                           X, g/l
 mlss                                      Expected underflow conc.
 concentration                                                           8
         Settling Flux

    Settling Flux, Gs = X Vs
Where:   X = Solids concentration
         Vs = Settling velocity at
              that concentration

   Determine Vs with settling tests

                                      9
Settling Flux
        Settling tests at various
        solids concentrations
          Interface height

             We record
             interface
               height
                  vs
                time


                               10
                                       Settling Curve
                        1600
                        1400                             Vs is the slope of the
Interface Height (mm)




                        1200                             straight section of
                        1000                             the settling curve
                        800
                        600
                        400
                        200
                        0
                               0   5   10   15   20     25 30      35   40   45    50
                                                      Time (min)
                                                                                  11
             Settling Flux
    Now that we have the settling
    velocity Vs we can calculate Gs
               Gs = X Vs
This gives us one (1) point on the flux curve.
To get more points we need to run more tests
at different solids concentrations.

                                             12
          Settling Flux
  For most activated sludge there
  exists the following relationship
             Vs = Vo e-kX
          Substitution gives
            Gs = X Vo e-kX

With a few settling tests we can solve for
Vo and k and define the whole flux curve.
                                         13
                     Veslund Relationship
        2.0
        1.5
        1.0                             Vo = y intercept
        0.5                             k = line slope
ln Vs




        0.0
        -0.5
        -1.0
        -1.5
        -2.0
               0.0     1.0   2.0            3.0   4.0      5.0
                                   X, g/l
                                                            14
                        State Point Diagram
              8.0
              7.0
                                         Now we plot the
G, Kg/m2-hr




              6.0
              5.0                        three elements
              4.0                        together to form the
              3.0                        State Point Diagram
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18   20
                                        X, g/l

                                                                 15
                            Thickening Failure
              8.0
              7.0
G, Kg/m2-hr




              6.0                         Thickening failure
              5.0
              4.0
              3.0
              2.0
              1.0
              0.0
                    0   2    4   6   8    10 12   14   16   18   20
                                         X, g/l

                                                                  16
                                Inventory Shift
              8.0
              7.0
G, Kg/m2-hr




              6.0
              5.0
              4.0               1
              3.0           2
              2.0
              1.0
              0.0
                    0   2       4   6   8    10 12   14   16   18   20
                                            X, g/l

                                                                     17
                        Clarification Failure
              8.0
              7.0
G, Kg/m2-hr




              6.0                        Clarification failure
              5.0
              4.0
              3.0
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18    20
                                        X, g/l

                                                                  18
                            Flow Increase
              8.0
              7.0
G, Kg/m2-hr




              6.0                    Overflow line gets steeper
              5.0
              4.0
                                    State point moves up
              3.0
              2.0
              1.0
              0.0
                    0   2   4   6    8    10 12   14   16   18   20
                                         X, g/l

                                                                  19
                    Change Settling Properties
              8.0
              7.0
G, Kg/m2-hr




              6.0
              5.0
              4.0
              3.0
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18   20
                                        X, g/l

                                                                 20
                        Optimizing RAS Rate
              8.0
              7.0
G, Kg/m2-hr




              6.0
              5.0
              4.0
              3.0                   RAS rate too high
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12    14   16   18   20
                                        X, g/l

                                        Underflow conc. too low   21
                        Optimizing RAS Rate
              8.0
              7.0
G, Kg/m2-hr




              6.0
              5.0                        Lower RAS
              4.0                        pumping, higher
              3.0                        RAS concentration
              2.0
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18   20
                                        X, g/l

                                                                 22
                        State Point Analysis
              8.0
              7.0
                            State Point Analysis is a useful
G, Kg/m2-hr




              6.0
              5.0           tool for both designers and
              4.0           operators to graphically
              3.0           understand the dynamics of an
              2.0           activated sludge clarifier.
              1.0
              0.0
                    0   2   4   6   8    10 12   14   16   18   20
                                        X, g/l

                                                                 23
State Point Analysis



      Questions ?




                       24

				
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Description: STATE POINT ANALYSIS