Evaluation of a quasi-cuboid batch solar disinfection (SODIS) reactor for treatment of harvested rainwater in resource-poor, clinical environments

We present a 150 L cuboid “Fish Tank Reactor” (FTR) batch reactor for solar disinfection (SODIS) of harvested rainwater was designed for ease of manufacture and maintenance in low-income countries. Each reactor wall was made from 15 mm thick poly(methyl-methacrylate) (PMMA) sheets silicon-bonded together, with removable polished aluminium reflectors and aluminium reinforcements. Inactivation comparison studies were carried out under natural sunlight, using Escherichia coli, Enterococcus faecalis and MS2 coliphage, against a previously reported V-Trough Reactor (VTR) comprising four interconnected 50 L PMMA photoreactor tubes of 5 mm wall thickness. Comparisons were also completed between FTR configurations with and without reflectors, and between FTR and VTR reactors. Reflector removal on the FTR provided an average decay constant reduction of 54.7% ± 4.2% across all microbial species. VTR and FTR (with reflector) achieved Log reduction values (LRVs) > 6 log units for E. coli and E. faecalis (in under 5 h with 800 kJ/m 2 solar UV). The corresponding decay constant of the VTR is 1.8 times larger than that of the FTR for E. coli and 1.9 times for E. faecalis . Neither FTR reflector configuration achieved a LRV > 2.0 for MS2 coliphage due to poor UV-B transmittance (cut-off 300 nm) of the PMMA. While the advantages of using locally available materials in LMICs are obvious, the poor virus inactivation highlights that careful attention must be paid to container wall UV transmittance if targeted or comprehensive protection from waterborne pathogens is to be achieved.