Hydrogen sulfide poses a major challenge not only in the collection system but also at the wastewater treatment plant. Here are five reasons why you should monitor H2S at the WWTP:
1. H2S causes foul-smelling odors
H2S causes unpleasant malodors at the wastewater treatment plant. The rotten-egg odors can be registered in H2S concentrations as low as 0.01ppm making it a major nuisance to both plant operators and nearby residents.
2. H2S poses a major worker-safety concern
Frequent hydrogen sulphide issues form the basis for an unhealthy and even dangerous work environment at the treatment plant. Prolonged exposure to H2S concentrations in the range 2-5ppm can cause nausea, tearing of the eyes, headache and breathing problems, while exposure to concentrations above 20ppm may cause fatigue, loss of appetite, headache, irritability and dizziness. At 100-150ppm, H2S can no longer be registered by the nose, and at concentrations above 500ppm it causes eye damage, rapid unconsciousness and death according to OSHA.
3. H2S causes plant assets to break down prematurely
The corrosive properties of hydrogen sulfide are well-established, and these problems are just as common at the wastewater treatment plant as they are in the collection system. Hydrogen sulfide gas is converted into sulfuric acid when sulfate-reducing bacteria in the biofilm on concrete surfaces reacts with the gas. This causes a corrosion attack that slowly converts otherwise healthy concrete constructions into fragile plaster.
4. H2S inhibits biological treatment processes
Hydrogen sulfide directly inhibits some of the biological treatment processes at the WWTP. According to a study, H2S has an inhibitory effect on both ammonium and nitrite oxidizing processes. This indicates that even low concentrations of sulfide may strongly alter the nitrifying activity of activated sludge and provoke nitrite accumulation. Additionally, H2S is a major issue that needs thorough attention at treatment plants with anaerobic digesters.
5. H2S is still an unknown process parameter
As mentioned in the four paragraphs above, H2S poses a major problem at the treatment plant because it causes malodors, worker safety concerns, premature asset corrosion, and because it inhibits biological treatment processes. However, despite all these unwanted effects, H2S is still largely an unknown process parameter at the wastewater treatment plant.
We therefore believe the most important reason why you should monitor H2S at the treatment plant is to get a full and dynamic insight into how it impacts your plant. Equipped with this knowledge, you can mitigate the problems directly at the plant – or even better – move upstream in the sewer network, solve the problems at the source, and thereby prevent high H2S concentrations from even entering the plant altogether.