Challenges of Recommissioning the APDs at the Columbus

Challenges of Recommissioning the APDs at the Columbus Southerly WWTP

Agenda • Introduction and plant overview • History of the Acid Phase Digesters • Decision making process – Condition assessment – Alternatives evaluation • Science-based/data-driven design approach • Project elements • Conclusions/questions

Key Takeaways • xx

Southerly Wastewater Treatment Plant Overview • Current Operating Conditions – 114 MGD Average Daily Flow – 330 Peak Wet Weather Flow – CEPT will increase Peak Wet Weather flow to 440 (Sept ’ 19)

SWWTP Digestion Train • 2 Sludge Storage Tanks • 3 Acid Phase Digesters (APD) • 6 Methane Phase Digesters (MPD) – 5 floating cover tanks (1 -5) – Digester 6 is a fixed steel cover

The Southerly Acid Phase Digesters • Installed as part of S 66 in 200 X – Each tank holds 353, 800 gal – Designed for an SRT of 1. 4 days

The Southerly Acid Phase Digesters • Operated as Acid Phase Digesters for XX years – Operated at an average SRT of 4 days – Converted to storage tanks and removed from gas system • Acid Phase Digesters were to be permanently converted to storage tanks as part of S 90. – Would allow for additional TPS storage plus a blend tank – Foul odor and gasses sent to biofilter

What Changed?

Old Requirements New Requirements • Incineration off line in 2015 • OARS Tunnel • Wet weather expansion (CEPT) • 100% Class B Sludge • Increase in solids • Plan for growth

Solids Mass Balance Update

Findings

Condition Assessment

Gas Sampling

Previous Evaluations • • Condition assessment of existing assets 3 D scanning of existing facilities Sludge rheology testing Digester grit characterization

Condition Assessment

3 D Scanning

3 D Scanning

Grit Characterization

Rheology Testing

Rheology Testing

Phase 1 – Digester Process Expansion

Phase 1 – Digester Process Expansion

Phase 1 – Surface Withdrawal

Phase 2 – Rehab APDs

Phase 2 – APD/MPD Expansion

Phase 2 – Other Process Improvements • FOG • Nutrient Removal • Food Waste

Summary • Wet weather events impact solids stream too! • A holistic evaluation that includes solids disposal diversity/risks as well as process capacity is needed to determine the most cost-effective solids management approach. • Engagement with plant operations and maintenance staff throughout design provides critical input to identify areas of concern and collective buy -in with process and operational changes. • Leverage science-based/data-driven design approaches for defensible decision making. • Digester Expansion Project should be bidding within the next month – ~$20 M Bid Estimate

Questions?