Effect of Seasonal Changes in Water Quality on Biofouling and Corrosion in Fresh Water Systems

Abstract

This paper describes the seasonal variations in the water quality of a fresh water reservoir at Kalpakkam and its influence on the corrosion rates of carbon steel and on the biofouling rates of stainless steel, brass, titanium and admiralty brass. The study conducted during May 1992 to August 1993 showed that the quality of inflow water changes on storage in the open reservoir due to excessive growth of macro and micro algae in the reservoir. There was an increase in the nutrient content and conductivity during the months of May to September 1992 followed by a decrease in all the water quality parameters except oxygen and silica contents during October to December 1992. Corrosion rates of carbon steel determined by short-term exposures showed an increase from 7.6 mpy (May 1992) to 10.6 mpy (August 1992) to 15.1 mpy (November 1992) and then a decrease during subsequent months. The Langelier index value in November indicated that the reservoir water should not be corrosive. However, the total viable count of bacteria (3 × 107 cfu cm-2) on the coupons was found to be at a maximum in November '92. Thus, the higher corrosion rate in November could be attributed to the possibility of microbially induced corrosion (MIC). Another possible contributing factor could be the relatively high dissolved oxygen observed in the reservoir during that period. Studies on the extent of biofouling by algae on various materials showed short-term fouling rates to be relatively high on titanium and long-term fouling rate to be the highest on stainless steel.