Monitoring Corrosion in Continuous Bio-degradation of Sulfur-containing, Volatile Organic Compounds

摘要

Continuous biodegradation of air pollutants i.e., volatile organic compounds (VOC), which are released to the atmosphere during many industrial operations, is one of the fastest-growing areas of bio-technology. Substantive bacterial growth, immobilization and VOC-degradation reaction, accompanied by typical fluctuations of other variables like pH, can significantly alter the general corrosion rate as well as potential for localized corrosion. Results from on-line corrosion measurements performed utilizing multiple electrochemical techniques in a large-scale, continuous bio-degradation of VOC mixture are presented in this paper. The VOC mixture containing styrene, alcohol and a sulfur compound, was decomposed involving a mixture of Pseudomonas and Thiobacillus bacteria immobilized on- polypropylene rings. Corrosion measurements were obtained by using industrial-type, electrochemical probes with electrodes made of carbon and stainless steels (UNS G10180, UNS S31603; UNS S30400). Four corrosion variables - general corrosion rate, localized corrosion potential (Pitting Factor), Stern-Geary Co-efficient (B Value) and capacitance (CMI) were continuously recorded concomitant with other process parameters such as solution pH, oxygen concentration, flow rate, temperature etc. Observed fluctuations of corrosion variables were in line with bacteria growth showing the build-up of the bio-film. Significant potential for localized corrosion (Pitting Factor) was observed to be accompanied by fluctuations in bio-process parameters.