Evaluation of Greenhouse Gas Emissions from Septic ... - Geoflow

3.2.3 Sampling Method for Vent System1. The cap of the cleanout port located before the septic tank was removed to verify that therewas no water flowing through the pipe to avoid damaging the hot wire anemometer.2. The length of the anemometer as well as the sampling line was adjusted to make sure that itwas placed exactly in the middle of the pipe (see Figure 3-5).3. The sampling device was installed in the cleanout port and the anemometer was turned on.4. The 12 mL syringe was inserted into the sampling septum (Figure 3-8) and used twice towithdraw a total sample volume of 24 mL into an evacuated vial, as above. An air velocityreading was made each time a sample was taken.5. Two more samples were taken following step four with a sampling interval of two minbetween them. Finally, the sampling device was removed and the cleanout cap was replaced.Figure 3-8. Sampling of Gases from the Venting System.3.2.4 Sampling Method for Aqueous Methane1. Plastic tubing attached to a 12 mL syringe was inserted to approximately the middle ofthe liquid column in the first compartment of the tank.2. Two full syringes of wastewater were withdrawn to purge the tube line. A final 12 mLsample was taken. Five mL of this sample were inserted into an evacuated vial. Then thesyringe was pulled out leaving the hypodermic needle inside the septum for 30 sec toequilibrate the sample to ambient pressure (Alberto et al., 2000). A second 5 mL samplewas drawn.3. The plastic tubing was then inserted in the middle of the liquid column of the secondcompartment and step two was repeated.4. After returning the samples to the laboratory, all the samples were shaken for 24 hours(Guisasola et al., 2008) to let the methane equilibrate between the liquid and gas phases.3-8