Abstract
Ambitious energy targets in the 2020 European climate and energy package have encouraged many stakeholders to explore and implement measures improving the energy efficiency of water and wastewater treatment facilities. Model-based process optimization can improve the energy efficiency of wastewater treatment plants (WWTP) with modest investment and a short payback period. However, such methods are not widely practiced due to the labor-intensive workload required for monitoring and data collection processes. This study offers a multi-step simulation-based methodology to evaluate and optimize the energy consumption of the largest Italian WWTP using limited, preliminary energy audit data. An integrated modeling platform linking wastewater treatment processes, energy demand, and production sub-models is developed. The model is calibrated using a stepwise procedure based on available data. Further, a scenario-based optimization approach is proposed to obtain the non-dominated and optimized performance of the WWTP. The results confirmed that up to 5000 MWh annual energy saving in addition to improved effluent quality could be achieved in the studied case through operational changes only.
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Abbreviations
- ASM:
-
Activated sludge model
- bA :
-
Autotrophic decay rate
- BME:
-
Combined blower and motor efficiency
- BNRAS:
-
Biological nutrient removal activated sludge
- BOD5 :
-
5-Day biochemical oxygen demand
- BSM1:
-
Benchmark simulation model no 1
- Cc:
-
Clarification coefficient
- COD:
-
Chemical oxygen demand
- CODs :
-
Soluble chemical oxygen demand
- CODt :
-
Total chemical oxygen demand
- C p :
-
Heat capacity of air at constant pressure
- CSTR:
-
Completely stirred tank reactor
- d a :
-
Airflow per diffuser
- d d :
-
Diffuser submergence depth
- d de :
-
Diffuser density
- DO:
-
Dissolved oxygen concentration
- e :
-
Combined blower and motor efficiency
- E Ca :
-
Aeration energy consumption
- E Cm :
-
Mixing energy consumption
- E Cp :
-
Pumping energy consumption
- E Ct :
-
Total energy consumption
- E Pw :
-
Total energy produced from WAS
- EQI:
-
Effluent Quality Index
- F c :
-
Correction factor
- F f :
-
Fouling factor
- GHG:
-
Greenhouse gas
- HC-D:
-
High-load condition in dry-weather operational mode
- HC-W:
-
High-load condition in wet-weather operational mode
- H d :
-
Dynamic head
- HRT:
-
Hydraulic retention time
- H s :
-
Pumping head
- H st :
-
Static head
- I c :
-
Current absorption
- IMLR:
-
Internal mixed liquor recycle
- K :
-
Dynamic head-loss coefficient
- K c :
-
Proportional gain
- K OA :
-
Oxygen half-saturation index for autotrophic biomass
- MLE:
-
Modified Ludzack-Ettinger
- MLSS:
-
Mixed liquor suspended solids
- NC-D:
-
Normal condition in dry-weather operational mode
- OTE:
-
Oxygen Transfer Efficiency
- PAC:
-
Performance assessment criterion
- P D :
-
Delivered power blower
- P e :
-
Pump efficiency
- P FL :
-
Pipe friction loss
- PI:
-
Proportional Integral
- P PUV :
-
Power per unit volume of mixing
- PS:
-
Primary sludge
- P s :
-
Barometric pressure
- Q :
-
Pumping flow rate
- Q IMLR :
-
Internal mixed liquor recirculation flowrate
- Q N :
-
Normalized air flux
- Q RAS :
-
Return activated sludge flowrate
- R :
-
Universal gas constant
- RAS:
-
Return activated sludge
- RWS:
-
Reject water from sludge treatment units
- SCADA:
-
Supervisory control and data acquisition
- SOTE:
-
Standard oxygen transfer efficiency
- SRT:
-
Solids retention time
- STOWA:
-
Acronym for the foundation for applied water research in Netherlands
- SVI:
-
Sludge volume Index
- T a :
-
Blower inlet air temperature
- T i :
-
Integral time
- TKN:
-
Total Kjeldahl nitrogen
- TN:
-
Total nitrogen
- TP:
-
Total phosphorous
- TSS:
-
Total suspended solid
- VS:
-
Volatile solids
- VSS:
-
Volatile suspended solids
- w :
-
Mass of the airflow
- WAS:
-
Wasted activated sludge
- WWTP:
-
Wastewater treatment plant
- α:
-
The ratio of process water to clean water mass transfer coefficients
- ΔPd :
-
The pressure drop of the piping and diffuser downstream of the blower
- μA :
-
The maximum specific growth rate for autotrophic biomass
- φ :
-
Power factor
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Acknowledgments
This research was financially supported by Società Metropolitana Acque Torino (SMAT). The authors wish to thank SMAT managing, laboratory, maintenance, and operation personnel for their engagement and cooperation during the sampling campaigns of this project.
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Borzooei, S., Amerlinck, Y., Panepinto, D. et al. Energy optimization of a wastewater treatment plant based on energy audit data: small investment with high return. Environ Sci Pollut Res 27, 17972–17985 (2020). https://doi.org/10.1007/s11356-020-08277-3
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DOI: https://doi.org/10.1007/s11356-020-08277-3