Wastewater Engineering - Formulae & Calculations

Updated 27 July 2008

Wastewater Engineering Group is pleased to provide you the following formula and calculations most commonly used in water and wastewater engineering. We hope you find this page useful and please feel free to send us your comments or if you would like us to include a particular calculation:

1. Wastewater Screening Design Calculator:

• External resource: http://www.ajdesigner.com/phpscreening/screening_fine_screens_gravity.php

2. SVI - Sludge Volume Index Calculations:

• First obtain the SSV (Settled Sludge Volume) through 30 minute settling test, ususal value is 100~300 mL/L for activated sludge systems
• SVI = SSV x 1000/MLSS
  where MLSS is in unit of mg/L
  Assume SSV = 200 mL/L and MLSS = 3000 mg/L, then SVI = 66.7 mL/g

  Source: Wastewater Engineering: Treatment and Reuse

3. Sludge Volume Reduction through dewatering for fuel treatment (Industrial Effluent)

Dry sludge content	Sludge volume
1% (roughly 10000 mg/L MLSS)	1 volume
25%	12% (reduced by 88%)
30%	10% (reduced by 90%)
40%	7.5% (reduced by 92.5%)
50%	6% (reduced by 94%)

Note:
1. Source: Filters and Filtration Handbook by Ken Sutherland, 5th edition
2. The above table has its limitations and should not be blinded applied. In the original text the author was trying to give an idea on sludge from oil fuel

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Other Resources on Water, Wastewater Engineering Calculations: