Microbiological Corrosion Aspects of the Great Man-made River Project, Great Socialist People’s Libyan Arab Jamahiriya.

Abstract

Microbiological Corrosion Aspects of the Great Man-made River Project, Great Socialist People’s Libyan Arab Jamahiriya

The Great Man-made River Project (GMRP) in Great Socialist People’s Libyan Arab Jamahiriya is the largest civil engineering project in the world. It is designed to convey freshwater from extensive wellfields in the desert to the coast, for irrigation and drinking supplies. One of the phases is nearing operational stage, others are currently under construction. Microbiological corrosion aspects have been considered at an early stage in the project. Measures (such as chlorine treatment and modification of operational regimes) have been taken to minimise microbiological problems.

The system has a design life of 50 years and an integral part of the design is protection against microbiologically induced corrosion (MIC). Water wells in the vicinity experienced pitting corrosion of stainless (flask-shaped cavities and penetrations in riser pipes and well screens) and galvanised steels (sulphide-containing, wide, deep pits). This was due to the combined action of iron bacteria and sulphate-reducing bacteria (SRB), and occurred after relatively short service life. Shut-in (non-pumping) wells supported the growth of SRB and iron bacteria. Biofouling experiments demonstrated a rapid surface colonisation by bacteria upon exposure of steel to flowing water.

A detailed monitoring and control programme has been initiated to minimise attack of stainless steels, Monels, aluminium-bronze alloys, galvanised steel and pre-stressed concrete cylinder pipe by iron bacteria, sulphur-oxidising bacteria (thiobacilli) and SRB under different operating regimes.