Project Information
- Location: Citronelle, Alabama
- Project Type: Municipal Wastewater Treatment
- Completion Date: April 2016
Treatment Objectives
- Design Flow:
1,500 m3/day (0.40 MGD) Average
2,900 m3/day (0.76 MGD) Peak - Effluent Quality:
0.022 mg/L Total Phosphorus
PROJECT BACKGROUND & CHALLENGES
The town of Citronelle, Alabama consists of approximately 5000 people located about an hour from the Gulf Coast within the boundaries of Mobile County. Geographically unique, Citronelle is built atop a giant salt-cored dome that is still rising steadily, within the eastern Interior Salt Basin in southwest Alabama.
The NEI Answer
The permit issued to Citronelle, Alabama is currently among the most stringent requirements being met by reactive filtration to date, at < 0.022 mg/L. There, the wastewater treatment plant discharges to Puppy Creek, contributing a very significant percentage of dry weather flow to the creek.
In collaboration with Speaks & Associates Consulting Engineers, Inc., we created an upgraded system for Citronelle by adding Blue PRO® reactive filtration for enhanced treatment efficiency and cost minimization. The reactive filtration phosphorus compliance upgrade was sized for a peak daily flow of 0.76 MGD, and its implementation has allowed the WWTP to meet its discharge permit cost effectively.
The project was contracted in late 2014, equipment was delivered to the site during late summer of 2015, assembled in the fall, and construction was completed in December 2015. The system was commissioned, and all checkouts were completed before year-end in preparation for performance testing.
Site Construction
UPGRADED SYSTEM PERFORMANCE
The performance test was a condition of process warranty and was conducted in February and March of 2016. Filter effluent during the performance test averaged < 0.013 mg/L TP in certified lab-analyzed 24-hour composite samples; values were corroborated by split samples analyzed in the field averaging 0.006 mg/L TP. The performance test’s successful completion signaled project completion.
The Citronelle WWTP must comply with a monthly average discharge limit of 0.022 mg/L TP from April through October.
Its first ultra-low-level compliance season was completed in 2016. Results from the site’s Discharge Monitoring Reports (DMRs) exhibit compliance for all months except August, when the site experienced an Act of God: a lightning strike damaged the plant controls. Despite this, the plant averaged just over 0.1 mg/L TP running many systems in manual settings. Replacement control system components were installed, and the plant was back within full compliance in under two weeks.
CONCLUSIONS
Citronelle’s WWTP meets its treatment goals operating with manual dose setpoint control and no online phosphorus feedback to the control system, since no online analyzers could reliably read total phosphorus below the required control line when the plant was designed. The facility also uses low molar dosing ratios ranging from 2 to 4 Fe:P, despite its ultra-low limits and use of dose setpoint control.
Citronelle tells a story. It shows reactive filtration as being among the most effective treatment solutions for meeting low µg/L phosphorus targets, in a manner that is both efficient and relatively simple to maintain. As technology evolves further, the future suggests that online analysis may lead to further chemical optimization under certain site design considerations. Until then, the results from Citronelle, Alabama, indicate an effective and sustainable solution for maintaining its permit of < 0.022 mg/L TP.
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