On-site rainwater harvesting and treatment for drinking water supply: assessment of cost and technical issues

This study assessed the performance of rainwater-harvesting systems installed for selected public utilities in the northern provinces of Vietnam where rainwater was collected, stored in stainless steel tanks, and treated with a complex filtration unit and Ultraviolet (UV) disinfection system (full system). Results from an operation of over 5 years show that the untreated rainwater could not be used directly for drinking purposes as it was contaminated with bacteria (total coliforms TC = 200-300 CFU/100 ml, Pseudomonas aeruginosa PA = 40-160 CFU/100 ml), and turbidity = 2-4 NTU. Most of the heavy metals detected were found below the standard limits. Phenol and its derivatives were detected occasionally as higher than the standard value (1 μg/L). After treatment, all parameters met the drinking water standards. The capital costs of the rainwater systems were approximately US$200/m³ and US$180/m³ for a full system and simplified system (without complex filtration unit), respectively, while the operation and maintenance (O&M) costs were 3 cents/L and 0.8 cents/L on average for a full system and simplified one, correspondingly.