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Odor Control

Wastewater treatment facilities are designed to reduce the environmental impact of raw sewage discharge through biological processes. Any biological process can naturally emanate odors, especially when undergoing the treatment process. The City of Concord maintains the existing infrastructure and continues to invest in improving odor control initiatives to contain any naturally emitted odor on-site as much as possible. 

Wastewater Treatment Odor Control Biofilter

Minimizing odor emissions helps employees, residents, and local businesses take greater pride in wastewater treatment efforts. Odor control improvements help to maintain focus on the treatment of wastewater.

Current Efforts

Wastewater treatment staff regularly monitor for hydrogen sulfide (H2S), a common odor from wastewater treatment plants, at various locations near the Hall Street Wastewater Treatment Plant to evaluate our odor control processes. An odor logger unit is set up weekly for H2S detection during the warm weather months.

View our most recent data log to see activity results.

Other Major Efforts

Wastewater Treatment Odor Control Biotower

 The open top sludge holding tanks are identified as significant sources of odor emission. Concrete covers are installed over the open top tanks to contain the emissions. A single stage chemical scrubber and carbon filtration system is installed to treat the air from the sludge holding tanks. 

1993-1997: A new two-stage packed tower wet chemical scrubber replaces single stage scrubber to improve effectiveness. A second odor control system is designed to treat emissions from areas at the headworks and primary clarifiers.

2000-2009: The new odor control system to treat emissions for the primary clarifiers and headworks area is placed in service. A comprehensive odor emissions study is held to identify all remaining odor sources, to establish criteria to eliminate neighborhood odor issues, and develop a plan to implement odor remediation measures. Solids processing area improved with a pretreatment dust collection scrubber and a three-stage packed wet chemical scrubber. 

2011-2014: Covers on remaining open process areas at the headworks and biotowers are put in place. A new biofilter odor control system is installed. Data-logging equipment is purchased to monitor atmospheric hydrogen sulfide concentration levels in the surrounding neighborhood area. Odor emissions sampling and atmospheric dispersion modeling are performed to quantify any remaining odor sources.

Contact Us
Dan Driscoll
Wastewater Treatment Superintendent

125 Hall Street 
Concord, NH 03301

Administration Hours:
Monday - Friday 
7:00 a.m. - 3:30 p.m.

Phone: 603-225-8691
Fax:     603-230-3850