Monitoring of Heterotrophic Plate Count (HPC) in Treated Water from Distribution System

Heterotrophic plate count (HPC) is a method that enumerates the total number of viable heterotrophs whichinclude bacteria, yeasts and molds. In water quality monitoring, it is performed to measure changes in the microbiological diversity in water treatment and distribution systems, as well as recreational waters and drinking water. It can also indicate risk of other pathogens’ regrowth in water and biofilm formation. Althoughthe Japanese water quality guideline recommends limit of HPC <100 CFU/mL and Canadian & US guidelines of<500 CFU/mL,the reporting of this parameter has not been developed by the Ministry of Health, Malaysia for treated water. Therefore,this study aimed at establishing a monitoring programme for the enumeration of HPC in treated water from distribution system using the ready-to-useCompact Dry AQ media via membrane filtration method. Out of 178 selected treated water samples, only 3 samples showed HPC positive and their counts were between 6 - 21 CFU/100mL, which were below the recommended limits. Hence, it can be suggested that the water treatment and disinfection performance at water treatment processes were adequate during the monitoring period, which further ensures clean and safe water supply to consumers.Further works that can be proposedinclude resampling and retesting of targeted repeating positive HPC sampling points. Meanwhile, other sampling points from different locations may also be included in future monitoring programme.