Dewatering

The dewatering unit thickens the digested sludge from the digester. The reject water is recycled to the inlet of the primary settler.

Input

1. Q: flow from Anaerobic Digester (m3/day)
2. T: wastewater temperature (degree C)
3. Soluble: Si, Ss, So, Sno, Snh, Snd, Salk
4. Particulate: Xi, Xs, Xbh, Xba, Xp, Xnd, TSS

Parameters

1. Percentage of suspended solids in the underflow of the thickener: dewater_perc = 28 %
2. Percentage of TSS removal: TSS_removal_perc = 98 %
3. Ratio of Xi convert to TSS: X_I2TSS = 0.75
4. Ratio of Xs convert to TSS: X_S2TSS = 0.75
5. Ratio of Xbh convert to TSS: X_BH2TSS = 0.75
6. Ratio of Xba convert to TSS: X_BA2TSS = 0.75
7. Ratio of Xp convert to TSS: X_P2TSS = 0.75
8. Dewatering factor (Similar to Thickening factor in Thickener unit): dewater_factor = dewater_perc*10000.0/TSS
   • Note we might have to recalculate TSS using Xi, Xs, Xbh, Xba, and Xp if their ratio to TSS in dewatering block is different from other ADM2ASM interface block.
   • It is an error if the dewatering factor is lower than 1.
9. Underflow/Sludge flow factor: Qu_factor = TSS_removal_perc/(100.0*dewater_factor)
10. Reject water factor (Similar to Thinning factor in Thickener unit): reject_factor = (1.0 - TSS_removal_perc/100.0)/(1.0-Qu_factor)

Outputs

1. if dewatering factor > 1
   1. Sludge
      1. Q = Q * Qu_factor
      2. T = T
      3. Soluble = Soluble
      4. Particulate = Particulate * dewater_factor
         1. if we have to recalculate TSS, TSS = new_calculated TSS * dewater_factor
   2. Reject water
      1. Q = Q * (1-Qu_factor)
      2. T = T
      3. Soluble = Soluble
      4. Particulate = Particulate * reject_factor
         1. if we have to recalculate TSS, TSS = new_calculated TSS * reject_factor
2. If dewatering factor <= 1, the influent is too high on solids to thicken futher. Therefore all the influent leaves with the dewatered flow (sludge). No return reject flow.
   1. Sludge
      1. Q = Q
      2. T = T
      3. Soluble = Soluble
      4. Particulate = Particulate
   2. Reject water
      1. Q = 0.0
      2. T = 0.0
      3. Soluble = 0.0
      4. Particulate = 0.0