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Corrosion Control When Using Secondary Treated Municipal Wastewater as Alternative Makeup Water for Cooling Tower Systems
Author(s) -
Hsieh MingKai,
Li Heng,
Chien ShihHsiang,
Monnell Jason D.,
Chowdhury Indranil,
Dzombak David A.,
Vidic Radisav D.
Publication year - 2010
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143010x12681059117094
Subject(s) - corrosion , wastewater , biocide , cooling tower , chlorine , effluent , water cooling , metallurgy , sewage treatment , environmental science , secondary treatment , chemistry , environmental engineering , environmental chemistry , waste management , pulp and paper industry , materials science , mechanical engineering , organic chemistry , engineering
Secondary treated municipal wastewater is a promising alternative to fresh water as power plant cooling water system makeup water, especially in arid regions. Laboratory and field testing was conducted in this study to evaluate the corrosiveness of secondary treated municipal wastewater for various metals and metal alloys in cooling systems. Different corrosion control strategies were evaluated based on varied chemical treatment. Orthophosphate, which is abundant in secondary treated municipal wastewater, contributed to more than 80% precipitative removal of phosphorous‐based corrosion inhibitors. Tolyltriazole worked effectively to reduce corrosion of copper (greater than 95% inhibition effectiveness). The corrosion rate of mild steel in the presence of free chlorine 1 mg/L (as Cl 2 ) was approximately 50% higher than in the presence of monochloramine 1 mg/L (as Cl 2 ), indicating that monochloramine is a less corrosive biocide than free chlorine. The scaling layers observed on the metal alloys contributed to corrosion inhibition, which could be seen by comparing the mild steel 21‐day average corrosion rate with the last 5‐day average corrosion rate, the latter being approximately 50% lower than the former.