Odor control system for wastewater settling tank with gas velocity test probes

A settling tank for clarifying wastewater, said tank having an outer wall containing a pool of wastewater so that the water at the surface of the pool is clarified, an outlet in said tank comprising:

• (a) an effluent trough supported at a raised position in the pool against the outer wall of the tank, said trough having a side wall parallel to the tank wall and lying somewhat below the surface of the pool;
• (b) a weir supported on the side wall and extending upwardly therefrom to permit clarified water from the pool to spill over into the trough;
• and
• (c) a flat walk plate overlying the trough and the weir and including a hatch cover section providing access to the weir, said walk plate extending horizontally from the tank wall to the upper edge of a vertical sidewall that extends downwardly into the pool, said walk plate and said vertical sidewall together acting to confine noxious gases emitted into the region above the trough and the weir to prevent their discharge into the atmosphere, said gases being entrained in air flowing at a specified velocity through said region to produce a specified velocity gas-laden air stream, said walk plate having a closable access port therein in alignment with a vertical center line going through the trough to permit the insertion of test probes to measure the velocity of the stream and the concentration of gases therein while the system is in operation, said said access port and said test probes being configured such that, said test probes when inserted in said port, then effectively seal said port to prevent the escape of the air stream from the region.