Advanced Treatement Which toxic gas is found mainly in groundwater, is heavier than air, and is odoriferous? Tags: Certification Exam Prep, Distribution System, Hydrogen sulfide, Water Treatment Read more articles Previous PostFiltration Next PostBackflow Prevention Devices You Might Also Like Final Thoughts – Advantages of Online Training February 28, 2019 Automate Your CEU and Safety Compliance Training May 1, 2019 Texas Class B Water System Operator Requirements (part 1) June 12, 2017 Post author: Post published:January 20, 2017 Post category:Certification Exams / Distribution / Water Treatment