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Plant-wide model-based analysis of iron dosage strategies for chemical phosphorus removal in wastewater treatment systems

Kazadi Mbamba, C. LU ; Lindblom, E. LU ; Flores-Alsina, X. ; Tait, S. ; Anderson, S. ; Saagi, R. LU ; Batstone, D. J. LU ; Gernaey, K. V. LU and Jeppsson, U. LU (2019) In Water Research 155. p.12-25
Abstract


Stringent phosphorus discharge standards (i.e. 0.15–0.3 g P.m
−3
) in the Baltic area will compel wastewater treatment practice to augment enhanced biological phosphorus removal (EBPR) with chemical precipitation using metal salts. This study examines control of iron chemical dosing for phosphorus removal under dynamic loading conditions to optimize operational aspects of a membrane biological reactor (MBR) pilot plant. An upgraded version of the Benchmark Simulation Model No. 2 (BSM2) with an improved physico-chemical framework (PCF) is used to... (More)


Stringent phosphorus discharge standards (i.e. 0.15–0.3 g P.m
−3
) in the Baltic area will compel wastewater treatment practice to augment enhanced biological phosphorus removal (EBPR) with chemical precipitation using metal salts. This study examines control of iron chemical dosing for phosphorus removal under dynamic loading conditions to optimize operational aspects of a membrane biological reactor (MBR) pilot plant. An upgraded version of the Benchmark Simulation Model No. 2 (BSM2) with an improved physico-chemical framework (PCF) is used to develop a plant-wide model for the pilot plant. The PCF consists of an equilibrium approach describing ion speciation and pairing, kinetic minerals precipitation (such as hydrous ferric oxides (HFO) and FePO
4
) as well as adsorption and co-precipitation. Model performance is assessed against data sets from the pilot plant, evaluating the capability to describe water and sludge lines across the treatment process under steady-state operation. Simulated phosphorus differed as little as 5–10% (relative) from measured phosphorus, indicating that the model was representative of reality. The study also shows that environmental factors such as pH, as well operating conditions such as Fe/P molar ratios (1, 1.5 and 2), influence the concentration of dissolved phosphate in the effluent. The time constant of simultaneous precipitation in the calibrated model, due to a step change decrease/increase in FeSO
4
dosage, was found to be roughly 5 days, indicating a slow dynamic response due to a multi-step process involving dissolution, oxidation, precipitation, aging, adsorption and co-precipitation. The persistence effect of accumulated iron-precipitates (HFO particulates) in the activated sludge seemed important for phosphorus removal, and therefore solids retention time plays a crucial role according to the model. The aerobic tank was deemed to be the most suitable dosing location for FeSO
4
addition, due to high dissolved oxygen levels and good mixing conditions. Finally, dynamic model-based analyses show the benefits of using automatic control when dosing chemicals.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Chemical precipitation, Iron, Membrane bioreactors, Phosphorus removal, Plant-wide model, Wastewater treatment
in
Water Research
volume
155
pages
14 pages
publisher
Elsevier
external identifiers
  • scopus:85062073407
  • pmid:30826592
ISSN
0043-1354
DOI
10.1016/j.watres.2019.01.048
language
English
LU publication?
yes
id
6f42368b-bc1f-4cb6-95f0-8ca408f1d043
date added to LUP
2019-03-05 14:03:08
date last changed
2020-03-24 06:41:29
@article{6f42368b-bc1f-4cb6-95f0-8ca408f1d043,
  abstract     = {<p><br>
                                                         Stringent phosphorus discharge standards (i.e. 0.15–0.3 g P.m                             <br>
                            <sup>−3</sup><br>
                                                         ) in the Baltic area will compel wastewater treatment practice to augment enhanced biological phosphorus removal (EBPR) with chemical precipitation using metal salts. This study examines control of iron chemical dosing for phosphorus removal under dynamic loading conditions to optimize operational aspects of a membrane biological reactor (MBR) pilot plant. An upgraded version of the Benchmark Simulation Model No. 2 (BSM2) with an improved physico-chemical framework (PCF) is used to develop a plant-wide model for the pilot plant. The PCF consists of an equilibrium approach describing ion speciation and pairing, kinetic minerals precipitation (such as hydrous ferric oxides (HFO) and FePO                             <br>
                            <sub>4</sub><br>
                                                         ) as well as adsorption and co-precipitation. Model performance is assessed against data sets from the pilot plant, evaluating the capability to describe water and sludge lines across the treatment process under steady-state operation. Simulated phosphorus differed as little as 5–10% (relative) from measured phosphorus, indicating that the model was representative of reality. The study also shows that environmental factors such as pH, as well operating conditions such as Fe/P molar ratios (1, 1.5 and 2), influence the concentration of dissolved phosphate in the effluent. The time constant of simultaneous precipitation in the calibrated model, due to a step change decrease/increase in FeSO                             <br>
                            <sub>4</sub><br>
                                                          dosage, was found to be roughly 5 days, indicating a slow dynamic response due to a multi-step process involving dissolution, oxidation, precipitation, aging, adsorption and co-precipitation. The persistence effect of accumulated iron-precipitates (HFO particulates) in the activated sludge seemed important for phosphorus removal, and therefore solids retention time plays a crucial role according to the model. The aerobic tank was deemed to be the most suitable dosing location for FeSO                             <br>
                            <sub>4</sub><br>
                                                          addition, due to high dissolved oxygen levels and good mixing conditions. Finally, dynamic model-based analyses show the benefits of using automatic control when dosing chemicals.                         <br>
                        </p>},
  author       = {Kazadi Mbamba, C. and Lindblom, E. and Flores-Alsina, X. and Tait, S. and Anderson, S. and Saagi, R. and Batstone, D. J. and Gernaey, K. V. and Jeppsson, U.},
  issn         = {0043-1354},
  language     = {eng},
  pages        = {12--25},
  publisher    = {Elsevier},
  series       = {Water Research},
  title        = {Plant-wide model-based analysis of iron dosage strategies for chemical phosphorus removal in wastewater treatment systems},
  url          = {http://dx.doi.org/10.1016/j.watres.2019.01.048},
  doi          = {10.1016/j.watres.2019.01.048},
  volume       = {155},
  year         = {2019},
}