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The main source of drinking water for rural communities in India is rainwater harvesting ponds. These ponds do have a sand filtration system for turbidity removal, but the bacteriological quality of these ponds is not under compliance in most cases. In this context, Pattikadu village in Kancheepuram District (Tamil Nadu, South India) was chosen as the study area. It was observed that the biological parameter of drinking water from hand pump exceeds the limit prescribed by Indian standards. In this work, zero-energy disinfection technology was developed using UVC-LEDs for drinking water to meet the standards. The electrical power required for the disinfection was taken from the mechanical energy from up and down movement of the hand pump lever. UVC-LEDs (λemission 275 ± 5 nm) were powered by 6 V rechargeable battery which stores electrical energy by mechanical movement of the hand pump lever. Annular-type UVC-LED photo-reactor (1 litre) was developed and 100% disinfection within 6 minutes’ contact time was achieved. The UVC dose-based inactivation rate constant was 0.57 cm2/mJ. The present study demonstrated 2-log inactivation for 4.68 mJ/cm2 UVC dose. The novelty of the study is its practical applicability of a sustainable point-of-use disinfection technology which might be economically implemented to lower-income smaller communities.

The scalability of photocatalytic reactor is the major challenge due to the inability of the light penetration when the laboratory scale reactors are ascended. It is well known that characteristic length of photocatalytic reactor is one of the in uential parameters determining the e ciency of light penetration and also affects the hydrodynamic uid ow behavior inside the reactor. This study visualizes hydrodynamic ow behavior of three differently con gured photocatalytic reactors through numerical simulation of the uid mass transport inside the reactors. The three photocatalytic reactors are 1.Concentric cylindrical glass tube micro-reactor (CGTR), 2. UV-LED strip photocatalytic reactor (STR) and 3. Classical annular reactor (CAR) from our previous work. The simulations of ow behavior con rmed that CGTR exhibited plug ow regime, STR exhibited arbitrary ow (in-between continuously stirred tank reactor and plug ow reactor) and CAR behaved like continuously stirred tank reactor. Also interpretations of numerical modelling were validated through plotting experimental residence time distribution curve.Further, the comparison of performance parameters revealed that the highest modi ed Space Time Yield (STY modi ed ) 225 s − 1 and highest modi ed Photocatalytic Space Time Yield (PSTY modi ed ) 9.375 s − 1 /kW/m 3 was obtained for plug ow reactor when compared to continuously stirred tank reactor (CAR) and arbitrary ow reactor (STR). The study con rms that decrease in characteristic length of photocatalytic reactor onsets plug ow regime, which has highest photocatalytic performance e ciency.

The scalability of photocatalytic reactor is the major challenge due to the inability of the light penetration when the laboratory scale reactors are ascended. It is well known that characteristic length of photocatalytic reactor is one of the influential parameters determining the efficiency of light penetration and also affects the hydrodynamic fluid flow behavior inside the reactor. This study visualizes hydrodynamic flow behavior of three differently configured photocatalytic reactors through numerical simulation of the fluid mass transport inside the reactors. The three photocatalytic reactors are 1. Concentric cylindrical glass tube micro-reactor (CGTR), 2. UV-LED strip photocatalytic reactor (STR) and 3. Classical annular reactor (CAR) from our previous work. The simulations of flow behavior confirmed that CGTR exhibited plug flow regime, STR exhibited arbitrary flow (in-between continuously stirred tank reactor and plug flow reactor) and CAR behaved like continuously stirred tank reactor. Also interpretations of numerical modelling were validated through plotting experimental residence time distribution curve. Further, the comparison of performance parameters revealed that the highest modified Space Time Yield (STYmodified) 225 s− 1and highest modified Photocatalytic Space Time Yield (PSTYmodified) 9.375 s− 1/kW/m3 was obtained for plug flow reactor when compared to continuously stirred tank reactor (CAR) and arbitrary flow reactor (STR). The study confirms that decrease in characteristic length of photocatalytic reactor onsets plug flow regime, which has highest photocatalytic performance efficiency.

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