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Dewatering Unit

.. index::
   pair: watertap.unit_models.dewatering;dewatering

The main assumptions of the implemented model are as follows:

  1. Single liquid phase only
  2. Steady state only
  3. Has no volume

Introduction

Dewatering is a process commonly used in wastewater treatment plants to separate water from solids using centrifugal motion and/or vacuums. In doing so, the dewatering unit reduces the sludge volume, which improves system operation and mitigates costs related to storage, processing, disposal, etc. This implementation of the dewatering unit is based on the IDAES separator unit.

Degrees of Freedom

The degrees of freedom in a dewatering unit model are the inlet feed state variables:

  • temperature
  • pressure
  • component mass compositions

Model Structure

The dewatering unit model does not use ControlVolumes, and instead writes a set of material, energy and momentum balances to split the inlet stream into two outlet streams. Dewatering models have a single inlet Port (named inlet) and two outlet Ports (named overflow and underflow).

Sets

Description Symbol Indices
Time t [0]
Phases p ['Liq']
Particulate Components j ['X_I', 'X_S', 'X_P', 'X_BH', 'X_BA', 'X_ND']
Non-particulate Components j ['H2O', 'S_I', 'S_S', 'S_O', 'S_NO', 'S_NH', 'S_ND', 'S_ALK']

NOTE: These components are defined in the ASM1 Property Package documentation.

Parameters

Description Symbol Variable Name Index Value Units
Percentage of suspended solids in the underflow p_{dewat} p_dewat None 0.28 \text{dimensionless}
Percentage of suspended solids removed TSS_{rem} TSS_rem None 0.98 \text{dimensionless}

Equations and Relationships

Description Equation
Suspended solid concentration C_{TSS} = 0.75 (C_{X_{I}} + C_{X_{IP}} + C_{X_{BH}} + C_{X_{BA}} + C_{X_{S}})
Dewatering factor f_{dewat} = p_{dewat} (\frac{10}{C_{TSS}})
Remove factor f_{q_{du}} = \frac{TSS_{rem}}{100 * f_{dewat}}
Overflow particulate fraction split_{particulate} = 1 - TSS_{rem}
Overflow soluble fraction split_{soluble} = 1 - f_{q_{du}}

Class Documentation

.. currentmodule:: watertap.unit_models.dewatering


.. autoclass:: DewateringUnit
    :members:
    :noindex:

References

J. Alex, L. Benedetti, J.B. Copp, K.V. Gernaey, U. Jeppsson, I. Nopens, M.N. Pons, C. Rosen, J.P. Steyer & P. A. Vanrolleghem Benchmark Simulation Model no. 2 (BSM2)