Domestic three stage water-treatment option for harvested rainwater in water-stressed communities

Abstract

Rainwater harvesting (RWH) practice can be traced back millennia, the degree of its modern implementation varies greatly across the world. And is the best option for water-stressed communities. A harvested rainwater quality monitoring study was undertaken at 3 lakes constructed in NUST Islamabad, Pakistan for a period of 10 months over two seasons i.e. wet and dry periods. Overall, harvested rainwater was of good quality, falling within the recreational water quality as per WHO standards with the exceptions for pH, color, turbidity, total coliforms and total bacterial count. A large number of samples tested positive for the total bacterial count and total coliforms, showing that disinfection of harvested rainwater is mandatory prior to use and its direct consumption without treatment may pose a health risk. For its treatment, an indigenously designed (SwissPak) water filter employing physicochemical methods were tested for making harvested rainwater fit for potable use. This filter contains silica sand for pre-filtration, granulated chlorine for disinfection and charcoal for removal of taste, odor and dissolved organic while alum was used as coagulant initially. This filter successfully improved the harvested rainwater quality and proved itself a suitable option for water treatment.