MULTIVARIATE STATISTICAL DETERMINATION OF WATER QUALITY INDICATOR FOR ROOF HARVESTED RAINWATER IN UMUAHIA SOUTH-EAST, NIGERIA

This study aimed to assess the quality of harvested rainwater from two (aluminum and corrugated zinc) commonly used roof materials in several urban and rural parts of Africa, and particularly in Nigeria for potable use, and to identify and select appropriate water quality indicator sensitive to variations in response to roof types and precipitation sampling time regimes. A total of 36 samples (first-flush and post-flush) were taken from two different urban residential roofs during six rainfall events, within the months of June (3 events) and July (3 events), and analyzed for selected water quality parameters. The results showed that concentrations were far below recommended guidelines (WHO and NSDWQ). However, concentration levels in First-flush samples for the two roofs were relatively higher than Post-flush. This implies that quality improves with initial roof wash-off as traditionally practiced. Results also showed that sampling (interval) time had significant influence on quality parameters than roof material. Multivariate statistical tool was employed to identify a sensitive quality indicator. Factor analysis (FA) was used to group parameters into significant factors that explained over 72% of variations in water quality parameters. Discriminant analysis identified Sulphate and Chloride as the most sensitive parameters for residential roof harvested rainwater, and therefore, may be applied for water quality monitoring in the region.