An investigation on biological stability of product water generated by lab-scale and pilot-scale distillation systems

Abstract

Lab-scale and pilot-scale distillation systems were assessed in this study and the effectiveness of the treatment processes on Assimilable Organic Carbon (AOC) removal was also investigated. Seawater as one of the alternative water sources was used as the feed water and the resulting product water was intended for industry use. Acidification, ion trapping and anti-scaling chemical dosing were adopted as the pre-treatment processes to the feed water before distillation for pilot-plant system. The AOC assay was used to evaluate the efficiencies of various unit processes for AOC removal. Heterotrophic Plate Counts (HPC) was adopted in conjunction with AOC to determine the biological stability of the water samples. It is noted that the distillation system was able to produce a product water with an acceptable AOC concentration of less than 20 μg acetate-C L-1. This would suggest that the distillation system was capable of delivering a biologically stable product water. The results from lab-scale system indicated that pretreatment such as acidification, chlorination and antiscalant would increase AOC, although this does not affect the general performance of distillation system.