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2710 TESTS ON SLUDGES*

* Approved by Standard Methods Committee, 1997.

 

2710 D. Sludge Volume Index

1. General Discussion

 

    The sludge volume index (SVI) is the volume in milliliters occupied by 1 g of a suspension after 30 min settling. SVI typically is used to monitor settling characteristics of activated sludge and other biological suspensions. 1 Although SVI is not supported theoretically,2 experience has shown it to be useful in routine process control.

 

2. Procedure

 

    Determine the suspended solids concentration of a well-mixed sample of the suspension (See Section 2540D).

    Determine the 30 min settled sludge volume (See Section 2710C).

 

3. Calculations

 

                                                        settled sludge volume (mL/L) X 1000

                                            SVI =                                                               

                                                                suspended solids (mg/L)

 

4. Precision and Bias

 

    Precision is determined by the precision achieved in the suspended solids measurement, the settling characteristics of the suspension, and variables associated with the measurement of the settled sludge volume. Bias is not applicable.

 

 

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5. References

  1. Dick, R.I. & P.A. Vesilind. 1969. The SVI What is it? J. Water Pollut. Control Fed. 41:1285.

  2. Finch, J & H. Ives. 1950. Settleability indexes for activated sludge. Sewage Ind. Wastes 22:833.

6. Bibliography

 

Donaldson, W. 1932. Some notes on the operation of sewage treatment works. Sewage Works J. 4:48.

 

Mohlman, F.W. 1934. The sludge index. Sewage Works J. 6:119.

 

Rudolfs, W. & I.O. Lacy. 1934. Settling and compacting of activated sludge. Sewage Works J. 6:647.

 

Standard Methods for the Examination of Water and Wastewater. 20th Ed. American Public Health Association, American Water Works Association, Water Environment Federation.