Part 11: 💧 Case Studies of Optimization in Switzerland’s Wastewater Treatment PlantsThis overview highlights the impact of optimized contro...
Published on by Hossein Ataei Far, Deputy Manager of the Research, Technology Development, and Industry Relations Center at NWWEC
This overview highlights the impact of optimized control strategies on energy efficiency and nitrogen removal at WWTP Werdhölzli, WWTP Morgental, and WWTP Thunersee.
WWTP Werdhölzli:
🏙️ Background:
Serving Zurich and nearby villages, WWTP Werdhölzli is Switzerland’s largest treatment plant, with a capacity of 550,000 p.e. (205,000 m³/day).
Initially designed for nitrification, it now includes anoxic compartments for enhanced nitrogen removal.
🎯 Objectives:
Improve nitrogen removal and reduce energy consumption for aeration.
Focus on the impact of treating digester supernatant.
📊 Data Quality and Control:
Basic data quality control with routine measurements and diurnal variations.
🛠️ Simulation and Control Strategies:
Various control strategies were simulated to assess their impact on energy usage, phosphate precipitation, and effluent quality.
💡 Best Control Version (V3):
Achieved a 25% reduction in energy costs and over 50% reduction in chemical usage.
Total cost reductions of around 30%, with net savings rising to $1,400,000/year with additional benefits.
💧 Separate Supernatant Treatment (V3a):
Increased net savings by an additional $80,000/year.
Resulted in total net savings of about $2,400,000/year and improved nitrogen removal efficiency to over 80%.
🚀 Implementation:
Adopted the A/I process scheme and ammonia-based control as part of its upgrade.
WWTP Morgental:
🏞️ Background:
A single-stage activated sludge plant with a capacity of 83,000 p.e. (31,000 m³/day), upgraded for nitrification and pre-denitrification.
Faces challenges with aeration control due to outdated equipment and uneven wastewater distribution.
🎯 Objectives:
Reduce energy consumption, with no specific limits or taxes related to effluent quality or total nitrogen.
📊 Data Quality and Control:
Comprehensive data quality evaluation, including testing and calibration of various sensors and analyzers.
🛠️ Simulation and Control Strategies:
Simulation studies indicated potential improvements in nitrogen removal and energy savings.
💡 Optimized Control:
An on-off control strategy with feed-forward control at a DO set-point of 3 mg/L.
Reduced energy consumption by $26,000/year (a 70% reduction) and increased nitrogen removal by 48%.
💰 Cost Reductions:
Total potential cost savings could reach $65,000/year, with further benefits if effluent quality taxes were applied.
Conclusion:
🌟 WWTP Werdhölzli:
Achievements: Significant cost savings and enhanced nitrogen removal.
Methods: Advanced control concepts and supernatant treatment.
💧 These case studies highlight the substantial improvements and cost savings that can be achieved through optimized control strategies in wastewater treatment.
Reference:
[1] Rieger. Leiv, and et al. (2012).
#ControlStrategies
#SimulationStudies
Fig1. Map of Switzerland depicting the locations of the 64 wastewater treatment plants (WWTPs) investigated in 2016 (pink and green dots) and of the subset of 28 WWTPs studied in 2017(green dots)- Ref. : Elke Suess et. al, 2020.