After multiple complaints of sewer odor in the neighborhood of Fountain Ridge Section III (FR III), the County staff investigated the wastewater collection system that serves the neighborhood. Odor was proliferating throughout the neighborhood and corrosion of the sewer manholes was clearly evident.
Sewer System Description
There are 526 total homes from four neighborhoods that gravity flow to three terminal pump stations and one lift station. The three terminal stations discharge to a common interceptor force main. This interceptor is four miles of 10” and 12” PVC pipe that discharges to the gravity system at FR III. Additional direct connections to the interceptor include 2 commercial/retail parcels: a Sunoco Gas Station with a car wash, and Dockside Restaurant (at the time of monitoring H2S levels, the restaurant was not in service).
A hydrogen sulfide (H2S) gas monitor was installed on 10/30/2019 inside the manhole where the force main discharges and transitions to a gravity system within FR III. Data was collected continuously for one week. The initial reading indicated a weekly average H2S level of 250 ppm and a peak level of 1167 ppm.
The County purchased the Wet Well Wizard (WWW) aeration device and was subsequently installed on 11/18/2019. The unit was installed in the lift station, which was experiencing anaerobic conditions, evidence by the 4-6” layer of fats, oils & grease (FOG). The three terminal stations did not have FOG build up so only one WWW was used to begin the effort to reduce the H2S at FR III. Within 14 days of installation, the Wet Well Wizard was able to eliminate nearly all the FOG by keeping the wet well in a constant aerobic state.
The H2S monitor continued to collect data for four weeks after the installation of the WWW producing the following data:
- 10/30 – 11/8: Avg H2S level= 250 ppm, peak of 1167 ppm
- 11/8 – 11/21: Avg H2S level= 185 ppm, peak of 870 ppm
- Aeration unit installed on 11/18
- 11/21 – 12/5: Avg H2S level= 60 ppm, peak of 772 ppm
- 12/5 – 12/10: Avg H2S level= 48 ppm, peak of 496 ppm
- 12/10 – 12/17: Avg H2S level= 27 ppm, peak of 235 ppm
The use of the Wet Well Wizard has caused the wet well to remain in a constant aerobic state. As a result, the entire wastewater collection system has experienced reduced H2S levels. By eliminating the FOG within the wet well of the lift station, costs to remove it using a vactor truck have been avoided.