Hydrogen Sulfide: Jerome J605 Analyzer Streamlines Testing

Having never been to a wastewater treatment facility, I had some prejudices on what I would be exposed to while visiting the plant in Tolleson, Ariz.

I was informed that the operations manager, David Tyler, was going to run some tests, and Garrett Rowe and I were welcome to join him. In accordance with their air-quality testing protocol, when Maricopa County receives three odor complaints from nearby residents, the facility must test the air at the closest occupied location, which happens to be an elementary school on the corner of 91st Ave. and Lower Buckeye Rd.

We checked in at the front office at 11:40 a.m. and discussed the local odors with some of the staff. From the discussion we learned that there was a very pungent aroma in the area that smelled like burned materials. Since H₂S has a distinct rotten egg smell we didn’t believe the odor they were describing was coming from the wastewater facility. We also learned that there is a meat packing plant and a dairy within two miles of the school, and these places may be contributing to the unpleasant smells.

Once we left the office I took some deep breathes with my nose to try and characterize the odor. There was a faint but distinct smell of manure, but no rotten egg smell that would be expected with the presence of H₂S. We sampled the air for 30 minutes in the parking lot using the Jerome J605 portable analyzer from Arizona Instrument fitted with an ammonia scrubbing filter. The instrument was set to survey mode and the location was named “school.” The J605 was in range 0 and did not detect any H₂S during the testing period. We returned to the elementary school office and informed them that we didn’t detect any dangerous gases.

In addition to the testing conducted at the school, the wastewater facility operations manager also conducted a perimeter test, walking along the surrounding fence and measuring emissions in survey mode with the location set to “fence.” During this testing the instrument read 0.00 ppb for the vast majority of the fenceline. The one exception was the area where the wastewater entered the facility.

There the instrument measured concentrations as high as 110 ppb. As we left the high-concentration area the readings returned to 0.00 ppb. A few processing areas did have ammonia and chlorine bleach odors, but no signal was produced.

Following the perimeter walk, we walked from end to end through the middle of the compound, starting in the north and heading to the south, and again from the east and heading west. During the north/south testing the instrument did not register a reading above 0.00 ppb. As we traversed from east to west we passed through the sludge drying beds where solid waste is air dried before being shipped or sold. The material beds were approximately 30 percent filled, and smelled like plant fertilizer. No rotten egg smell was noticed and the instrument did not provide a reading above 0.00 ppb in this area. Once we reached the area where raw sewage entered the facility the instrument responded again.

The final areas we tested were the air scrubbers they use at the exhaust of the sealed sewage processing station. Two 6-foot-diameter cylindrical scrubbers rose approximately 20 feet off the ground. The scrubbers were filled with activated carbon and were in year three of five before needing to be replaced. David informed me that no prior testing had been conducted and these were the initial tests to ensure the scrubbers were maintaining efficiency. At the top of the scrubber where the air enters the atmosphere the instrument measured close to 8 ppm H₂S for scrubber 2 and 3 ppm for scrubber 1. The gases coming into the scrubbers were measured at 1 ppm, but there was a pressure gradient that would influence the results.

During general conversation the topic of solid content in sludge was brought up. David stated that they have the capability of testing solids in sludge, but don’t typically do this because the sludge is air dried for weeks prior to distribution off-site. However, many larger facilities do not have the ability to air dry their sludge for weeks and a rapid loss-on-drying instrument would be vital to monitoring mechanical drying processes. We also discussed testing Hg in water, and he stated they do test for Hg, but send water samples to an independent lab for metal analysis.

Overall, the Tolleson wastewater facility did a lot to dispel some of the prejudices I was expecting to encounter. Very few unpleasant smells were present, and the sludge material did not appear grotesque. In fact, it looked like topsoil available at a garden center. From a testing standpoint, we were able to begin understanding the process of cleaning the water, and how our instruments will best be used to ensure that wastewater facilities’ H₂S emissions are below prescribed levels. For our first visit we were able to point out that the cleaning scrubber could be monitored to ensure it is working properly.

Additionally, solid content determination would best be marketed to facilities that are only doing mechanical drying processes and shipping material shortly after drying. This would help them ensure their dryers are working efficiently, and they aren’t spending money shipping water. Hg testing would be worth pursuing, but difficult as a stand-alone method, since they are interested in other metal contaminant levels, as well.

For more information on the Jerome J605 portable analyzer from Arizona Instruments, call 800/528-7411 or visit www.azic.com/products_jerome_hydrogensulfide.aspx?MAG=Treatment+Plant+Operator&TYPE=February+Sweet+Sponsorship.