Assessment of deficiency of fish tank water ultraviolet disinfection and remedial measures.

1. Better bacterial inactivation was observed with higher ultraviolet (UV) doses. There is a need for better tank configuration (hydraulic performance) to ensure proper water circulation or a need to suppress microbial recovery. Addition of titanium dioxide (TiO2) during UV irradiation was effective in controlling microbial recovery. 2. Higher water temperature enhanced the fouling rate on quartz sleeves, revealing the need for more frequent cleaning of UV tubes to remove the fouling and enable higher UV transmittance for bacterial inactivation. 3. In a fish tank setup, better water circulation facilitates the UV disinfection system and minimises dead zones. This can be achieved by diagonal positioned inlets and the outlets, providing inlet baffles, and enabling better artificial mixing with oxygen diffusers. 4. UV system validation and maintenance practices need to be in place to secure the effectiveness.