Effectiveness of hybrid soliwave technique in mitigation of microbiologically influenced corrosion

Abstract

The applications of Ultraviolet (UV) radiation as an alternative approach to toxic chemical biocide for disinfecting bacteria such as Sulfate Reducing Bacteria (SRB) to mitigate Microbiologically Influenced Corrosion (MIC) in steel pipeline systems are already established. However, in the case of poor quality effluents, the UV radiation becomes less effective. Recently, Ultrasound technique (US) was observed to be attractive as pre-treatment for various types of physical disinfectant such as UV radiation. Hence, this research aims to investigate the performance of hybrid treatment known as Hybrid Soliwave Technique (HyST) to control MIC activity. The investigation was performed by utilizing two SRB strains namely pure strain ATCC 7757 and isolated SRB species from local site from BARAM, Sarawak. The study focused on three types of disinfection experiments which were individual UV radiation, individual US irradiation and HyST treatment, a combination of US and UV. Turbidity measurement and SRB cells were recorded to determine the most preferable pH and temperature for both SRB strain to proliferate actively. Corrosion rate was determined using weight loss method by exposing the steel coupons to SRB activity and abiotic sample. Both graphical and statistical analyses were performed using a statistical software (SPSS 20), to investigate the significance of SRB remaining cell number and SRB towards the corrosion rate of untreated and treated steel coupons. This study revealed that the preferable pH and temperature for ATCC 7757 and BARAM to grow actively in the Modified Baar’s Media is at pH of 8.5 and temperature of 37˚C. While, the corrosion rate of steel coupons in ATCC 7757 and BARAM strain was 0.5058 mm/year and 0.3209 mm/year respectively. These rates were at least 44% higher as compared to the corrosion rate in abiotic sample (0.1791 mm/year). The treatment results show that the HyST treatment succeeded to reduce the number of active bacteria, hence reducing the corrosion rate by 55%. The results proved that the presence of SRB increased the corrosion rate significantly compared to samples without SRB. The present study also revealed that the HyST treatment is an effective and a feasible approach in substituting toxic chemical biocides in controlling the MIC problems especially for the pipelines. Overall, the HyST treatment shows better efficiency against individual UV radiation treatment.