Plants treating pulp and paper mill process effluents are designed to convert water contaminated with chemicals from pulping, bleaching and papermaking processes into water clean enough to discharge in the permitted manner. Effluent streams from pulping and bleaching processes normally are more corrosive than streams from paper-making processes. Common corrosion problems include oxygen pitting of carbon steel; attack of concrete by condensed acids and wastewaters; microbiologically influenced corrosion (MIC) of carbon and stainless steels and abrasion-enhanced corrosion in grit chambers. Selection of construction materials that inadequately anticipates corrosion mechanisms results in costly problem mitigation in effluent trenches and piping, clarifiers, grit basins, mixing and settling tanks, etc. General mitigation measures are discussed in this paper.
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