Mechanisms of thermal treatment on two dominant copepod species in O 3/BAC processing of drinking water

Phyllodiaptomus tunguidus and Heliodiaptomus falxus are dominant copepods species in drinking water processing plants in southern China. With a potential penetration risk, the breeding and leakage of copepods are drawing more and more attention in recent years. The current study provided a thermal treatment method to control copepods and their eggs. Results showed that: (1) the immediate death rates of P. tunguidus and H. falxus after heated to 34-40 °C for 5 min are positively correlated to the treatment temperatures (P < 0.01), and all individuals of the both species were eliminated after heated at 40 °C for 5 min; (2) overall hatching rates of P. tunguidus eggs were negatively correlated with treatment temperatures (P < 0.01) between 39-45 °C, with zero percent hatched after treatment at 45 °C for 5 min; (3) hatching rates of H. falxus were negatively correlated with treatment temperatures (P < 0.01) between 37-41 °C, with no nauplii hatched when treated at 41 °C for 5 min; (4) paraffin section histological examination indicated that thermal treatment caused severe damage to internal organs and egg structure. Finally, based on the experimental data, the application of the thermal treatment method was discussed in ozonation combined with biological activated carbon (O3/BAC) processing of drink water treatment.