BIODEGRADABILITY OF BIO-POLYMER SLURRY

Abstract

In recent years, the usage of bentonite slurry in the construction industry has declined and has been substituted by synthetic polymer forms of drilling fluid such as polymer slurry and bio-polymer slurry, and their use in deep foundation construction is becoming more and more common (Likos et al., 2003). This could be due to the fact that it is more economical to manufacture synthetic and highly recyclable drilling fluids or an increasing awareness on environmental sustainability.

A review of past studies was done to understand various physical qualities of polymer slurry and bentonite. Comparisons were made between the two materials with regards to their borehole stability, shaft friction capacity and shear strength of slurry-sand interface. This revealed that the use of polymer-based slurry will increase the performance of the borehole as compared the usage of pure bentonite slurry.

One of the environmental concerns of drilling waste is the biodegradability of the drilling fluid. Biodegradation consists of three stages: biodeterioration, biofragmentation and assimilation. Biodegradation of polymers cleave and fragment polymeric molecules into tiny fractions, reducing progressively their molecular weight resulting in oligomers, dimmers and monomers and releasing carbon dioxide and water at the same time.

Bio-polymer is claimed by slurry specialty manufacturers and industry experts to be biodegradable. Therefore, this research aims to measure the biodegradability and the extent of biodegradability of this material using a scientific experiment that follows closely to ISO 14852 test method.

The experiment showed that bio-polymer had an average percentage biodegradation of 0.65% for test duration of 23 days. This extremely small percentage shows that any biodegradation for bio-polymer slurry is negligible and cannot be used to prove that it is biodegradable.