Reduction of Microbial Population in Cheese Whey by UV in a Single and Series Conventional Reactors

In this study, the effectiveness of two conventional UV reactors in series for the online sterilization of cheese whey was compared to that of a single conventional reactor. The single reactor and the two reactor series were tested at eleven flow rates (5, 10, 15, 20, 25, 30, 35, 40, 50, 60 and 70 mL min^-1) and five flow rates, (35, 40, 50, 60, 70 mL min^-1), respectively. 100% destruction efficiency could not be achieved in the single reactor. When two reactors were connected in series, the destruction efficiency reached 100% at the flow rate of 35 mL min^-1 and lasted for 25 min. The temperature of the effluent decreased with the increase in flow rate in both systems. The rate of microbial destruction in the single reactor and the two reactor series was described by an exponential equation. The maximum effluent temperatures in the single reactor and the two reactor series were 45.8 and 36.0°C, respectively. The flow in both reactors was laminar (R_e=1.39 at 5mL min^-1 and R_e= 20.10 at 70 mL min^-1). Visual observation revealed less fouling on the UV lamps of two reactor series than the single reactor. A different design in which there is no contact between the liquid and the UV lamp should be investigated. The quartz sleeve could also be replaced with fluropolymer coiled tube around the UV lamp. The smooth surface of the fluropolymer would reduce scaling and extend the effective operating time.