Broken Arrow Municipal Authority
Meeting of: 12-05-2017
To: Chairman and Authority Members
From: Utilities Department
Title:
title
Approval of and authorization to accept the proposal from Pencco, Inc. to conduct a 45-day chemical addition pilot program for odor control along the County Line sewer trunk line
end
Background:
The 36” diameter concrete cylinder sewer pipe along County Line Road conveys about 90% of the wastewater flow to the Lynn Lane Wastewater Treatment Plant. Several segments of the sewer line were constructed with drop manholes due to changes in elevation. At each drop manhole sewer gases are released as the flow drops down to a lower elevation in the manhole. The sewer gas generated at each drop manhole gets vented to the atmosphere through the corroded concrete manholes and cracks in the pipes. The release of sewer gas primarily Hydrogen Sulfide has become a major concern to the residents in the vicinity of the sewer trunk line and along County Line Road.
A community meeting was held on October 12, 2017 at the Grace Community Church at the corner of 91st and County Line. The purpose of the meeting was to meet with residents and address their concerns pertaining to the sewer odor emanating from the County Road trunk line. In attendance at the meeting were residents, city staff and Vice Mayor Scott Eudey.
At the meeting staff shared the progress being made on the proposed trunk line replacement project at an estimated cost of about $23 million. In the interim to mitigate the generation and release of sewer odor, the possibility of feeding a chemical into the sewer line to minimize the formation and release of sewer gas was discussed. Staff was directed to explore the chemical feed option.
The Utilities Director contacted Pencco, Inc who supplies and manages iron feed systems for odor control at several large cities in Texas, Arizona and California. The Director had worked with Pencco on a similar sewer odor problem elsewhere.
Pencco, Inc field representative and a chemical engineer were on site on October 26 and 27, 2017. Sewer utilities crew joined Pencco representatives and walked the entire line segment, taking Hydrogen Sulfide gas level readings for both dissolved and in air. Odor loggers were left overnight at several locations and retrieved the next day. Pencco representatives made a formal presentation to city staff and shared their findings.
The findings reported are as follows:
• High Sulfide generation occurs in the pipe along County Line Road before the drop manhole at 101st and County Line Road
• Stripping of Hydrogen Sulfide formed occurred at the 101st St manhole due to the high velocity and about 10-15 foot drop manhole. The sewer gas is released to the atmosphere and some remains in solution.
• Dissolved oxygen absorbed from the drop structure and the remaining Hydrogen Sulfide in solution is carried down the line by the wastewater.
• More Hydrogen Sulfide is generated past the Turnpike due to lack of oxygen in the pipe and the wastewater becomes septic.
• High levels of Hydrogen Sulfide production occurs along 185th E Ave and continues to increase past Jasper and towards the wastewater plant.
Based on the findings, Pencco’s recommendation is as follows:
• Set up a bulk chemical feed system to feed the SULFeND chemical solution treatment for Hydrogen Sulfide control. This ferrous salt binds the Hydrogen Sulfide into non-gaseous ferrous sulfide and keeps it in solution till the wastewater reaches the treatment plant.
• The bulk chemical tank and feeds pumps will be located at a manhole along County Line Road.
• Pencco’s field technician will install and commission the feed system. The chemical feed rate and hydrogen sulfide levels will be monitored remotely.
• Pencco will provide program reports to staff during the 45 day test period. Upon completion of the test, Pennco will meet with city staff to discuss results.
Funding is available in the operational budget of the Sewer Repair and Construction Division.
Cost: $40,122
Prepared By: Anthony C. Daniel, Utilities Director
Reviewed By: Finance Department
Assistant City Manager-Operations
Legal Department
Approved By: Michael L. Spurgeon, City Manager
Attachments: Proposal from Pencco for chemical addition for Hydrogen Sulfide
control along County Line Road sewer trunk line
Recommendation:
Approve and accept the proposal from Pencco, Inc. to conduct a 45 day chemical addition pilot program for odor control along the County Line sewer.