‘Flash pasteurization’ of contaminated streams using a direct contact gas-fired water heater Original Research Article

A commercial direct contact gas-fired water heater was modified for in-lab evaluation of microbial reduction and temperature consistency at various water flow rates. The water heater was modified so that a contaminated input stream could be treated using 50-gal (189.3-l) bulk feed tanks. A final reservoir tank was bypassed using six sampling ports placed in pairs along three locations in the vertical heating column with which to test the efficacy of a single pass at different positions in the heating zone. Temperature probes were utilized to follow water temperature at 8, 10, and 12 gal min−1 (30.3, 37.9, and 45.4 l min−1). When using inoculated water streams, we obtained 4–7 log10 cycle reductions of various micro-organisms tested suggesting that this may have potential use in situations where water recycling is of interest in food processing environments.