Simple Continuous-Flow Device for Combined Solar Thermal Pasteurization and Solar Disinfection for Water Sterilization

Anthony Amsberry,Justin Pommerenck,Clayton Tyler,Alexandré T F Yokochi,William Steinhauff

doi:10.36479/jhe.v3i1.33

Anthony Amsberry, Justin Pommerenck + Show 3 more

Open Access

https://doi.org/10.36479/jhe.v3i1.33

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Abstract

A collection unit and reflective concentrators were used to thermally preheat water to at least 70 °C for thermal pasteurization prior to a solar disinfection stage. The device is offered as a novel combined cycle to be used for either solar thermal pasteurization, during seasonalpeaks in solar irradiation, or as a solar preheat for UV solar disinfection which would occur in a flow-through solar disinfection trough. Inexpensive materials were used in order to simulate in field functionality and applicability to rural regions with low solar input. Solar incidence at Oregon State University, with latitude 45.5°, was recorded during trials conducted during May 1 to June 10 for the purpose of directly scaling the water treatment volumetric flowrate of the device for any future tests in other locations. This scaling by solar irradiation makes this dataset useful for other locations with higher or lower solar input and needing more or less treated water. The simple gravity-fed continuous system presented in this article makes use of a large cold water reservoir, a shell-and-tube heat exchanger, and a solar collector. The system, operating at flowrates of 100-150 mL/min is able to reach outlet temperatures of 74°C. The system is projected to produce 55 L of purified water daily when operating on a sunny day with peak UV radiation above 700 W/m2. System cost was $55 with an added optional $15 for the shell-and-tube heat exchanger.

Highlights

There is a fundamental gap between the effectiveness of water sanitisation mechanisms in developed countries as opposed to their lower starting capital implementation in under-developed rural regions (Kaushal & Varun, 2010)
Dayem et al (2012) produced a parabolic trough concentrating solar collector, which is an example of some of the continuous flow systems Dayem et al (2012) point out the efficient passive flow temperature regulation of the purification system developed by Duff & Hodgson (2005)
That is why combined cycle purification systems (CCPS) or Mode 2 are important using this new synergy between temperature and UV, solar disinfection (SODIS) becomes possible at high throughputs

Summary

INTRODUCTION

There is a fundamental gap between the effectiveness of water sanitisation mechanisms in developed countries as opposed to their lower starting capital implementation in under-developed rural regions (Kaushal & Varun, 2010). Most test systems employ either solar disinfection or thermal pasteurisation and have been used to effectively treat water in developing countries. If the synergistic interplay between temperature and UV inactivation of coliform DNA does occur as described in McGuigan et al (1998) and Safapour et al (1999), the proposed combined cycle can reduce the wait time for solar disinfection (SODIS) from one to two days to minutes. The thermal concentrator is a continuous-flow, gravity-fed system with flat reflectors that uses a simple solar oven to heat influent water to either pasteurisation temperature (70 °C for 7 minutes) or more preferably to synergistic SODIS temperatures (held at 45 to 60 °C under direct UV during SODIS).

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