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DO Probe Presentation
- 1. Operations Ingenuity at WEFTEC Waste Water Sampling Presented By: Sam McAdoo October 1st, 2014
- 2. H2S Monitoring Program 2 • As Part of an EPA Consent Decree Requirement, HRSD was required to establish a Hydrogen Sulfide Baseline Monitoring Program • 90% of HRSD’s pipelines are pressurized mains which make it difficult to obtain sample characteristics of both gas pockets and wastewater.
- 4. Modified Air Sample Tube 4
- 6. Design 6
- 7. Questions?
Editor's Notes
- Goals of Program: Establish a Relationships between Hydrogen Sulfide in the wastestream and internal corrosion Prevent/Minimize Odor Complaints Protect Assets against Corrosion Minimize Health and Safety Concerns related to H2S
- Initially HRSD’s Blow Off Pipe was adapted to collect a large air sample in a Tedlar bag. This required samplers to bleed off the 3 liters of air that the blow off pipe housed to get a good sample. Initial Sampling had high levels of Nitrogen and Oxygen from being contaminated by the ambient air in the Blow Off Pipe.
- The modified Air Sample Tube used a small hose to reduce the internal volume of the vent tube by 99% from 3 liters of ambient air to 0.3 liters. This allowed for quick purging of ambient air which proved to be very valuable especially during winter months where gas pockets where much smaller and there was less to sample.
- The initial Dissolved Oxygen readings were also high. The Existing technique for sampling was to collect a wastewater sample from the force main in a small container and insert a DO probe into that container. The free falling wastewater into the container concerned the team that the wastewater may be getting aerated during collection of the sample. That concern led to the creation of the DO insertion Probe which is inserted directly into the pressurized main to collect a DO sample.
- This Probe Insertion Apparatus was built in house and tested on a pressurized raw water main HRSD uses for emergency repair training. The Apparatus was used successfully in the field at multiple sites but after comparing the dissolved oxygen levels between the two collection methods there proved to be very little variation in the results. The insertion probe being the more difficult of the collection methods was retired, but it did relieve concerns of contaminated samples with the preliminary dissolved oxygen sampling method.