Contents (1)Biocorrosion fundamentals (2)Monitoring devices (3)Electrochemical monitoring system BIOX (4)Areas of application
Biocorrosion fundamentals Corrosion is the reaction of a material with substances in the environment, which causes a detrimental alteration of the material. It describes the electrochemical, chemical and metallophysical alteration of metals (translated from DIN50900). Definition of corrosion:
Biocorrosion fundamentals Kinds of corrosion processes: Anodic process: Me Me 2+ + 2 e - Cathodic process: ½ O 2 + H 2 O + 2 e - 2 OH - (Oxygen corrosion) 2 H 3 O + + 2 e - H 2 + 2 H 2 O (Acid corrosion) H 2 S + 2 e - S 2- + H 2 (H 2 S corrosion) S 2- + Fe 2+ FeS
Biocorrosion fundamentals Parameters influencing corrosion: pH-value redox-potential oxygen concentration water activity All of these corrosion relevant parameters can be influenced by microorganisms leading to the so called biocorrosion. Biocorrosion does not represent a new form of corrosion processes, instead it describes the influence of microorganisms on the kinetics of these processes.
Biocorrosion fundamentals Microorganisms involved: Acid-producing MO Inorganic acids: H 2 SO 4 (sulfuroxidisers), HNO 3 (nitrifyers), H 2 CO 3 (heterotrophic organisms) Organic acids: Acetic acid, formic acid, oxalic acid, citric acid, lichen acids Sulphate reducing bacteria (SRB) Most important!! Accounting for 95% of all biocorrosion cases. Formation of H 2 S Metal-depositing bacteria Formation of Fe 2 O 3 (Iron oxidisers), MnO 2 (Manganese oxidisers) …
BIOX system BIOX system is an innovative on-line monitoring tool designed to optimise the antifouling and sanitising water treatments against biofilm growing in industrial cooling circuits, tube networks, pipelines and equipment.
BIOX system The system core consists of a special tubular electrochemical sensor, inserted in suitable ways in plant circuits, which output (electric signal,1 Volt) is correlated both to aerobic biofilm growth and to the presence of oxidant species in the water: the biofilm growing on metal surface of the sensor the oxidant species in the water bulk crossing the tubular probe.
BIOX Probe Stainless Steel - Cathode Zinc - Anode water flow outwater flow in ohmic drop measurement
Monitoring The optimal monitoring method should indicate: -Location-Composition -Extend-Kinetics This information should be acquired: -on-line -in situ-non destructively -in real time -accurately-representatively -reproducibly -automatically In addition the devices should be easy to handle, robust and cheap. Deposit
BIOX application details 1)Technique: 2)Main purpose: 3)Application: 4)Environment: 5)Resolution: 6)Interferences: 7)Limits: 8)Advantages: 9)Comments: High resistance - galvanic coupling On-line measurements of the microbial fouling growth in the presence of oxidizing species, in particular chlorine and bromine. Laboratory, Pilot: Preliminary test for: Biocide qualification, Water quality qualification, Process water qualification Plant: Biocide treatments optimization Others: Possible application for risk assessment of biofilm and MIC in drinking water and process water Seawater, Fresh water, Industrial water = 0-10 6 bacteria/cm 2 ; = 0-1 mg/l (chlorine) weakly sensitive to Fe ++ /Fe +++ couple that is present during anticorrosion treatments with ferrous salts. not sensitive to oxidant in the water if biofilm covers the probe; not sensitive to biofilm if high concentration of oxidant in the water; the probe doesnt work if the flow is absent Real time estimation of the biofouling growth, Real time estimation of oxidant presence in the water, Real time (indirect) estimation of chlorine or other oxidant demand of water. Optimization of the consumption of oxidants, with respect to concentration and time. It does not require skilled personnel in the biological or chemical field, and is easy to handle. The probe must be mechanically cleaned only once a year.
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