Effect of water quality parameters on solar water disinfection: a statistical experiment design approach

Abstract

With a view to evaluating the effects and interactions of three influential factors, turbidity, pH and dissolved oxygen (DO), on the efficiency of solar water disinfection process, response surface methodology (RSM) based on Box–Behnken design was employed. Total coliform (TC) removal and heterotrophic plate count (HPC) removal were used as response factors. The RSM models were developed based on the experimental results of four-hour solar exposure in polyethylene terephthalate bottles. The measured and predicted removals were close to each other. Though the HPC removal and TC removal showed similar trends, the HPC removal was much lower (40–66%) compared to TC removal (68–97%) for the conditions studied. The results showed that turbidity up to certain levels (10–20 NTU) did not adversely impact the bacterial removal. In the range studied (6.0–9.5), pH showed little influence on the removals. While bacterial inactivation showed significant reduction at low DO levels, increasing DO beyond a certain level (5–6 mg/L) did not show any beneficial effect on bacterial inactivation. The study thus demonstrated the usefulness of RSM in modelling and analysing solar disinfection process.