하수재이용수의 유리잔류염소 수체감소 특성 연구

Abstract

The reclaimed water has been highlighted as a representative alternative to solve the lacking water resources. This study examined the reduction of residual free chlorine by temperature (5, 15, 25°C) and initial injection concentration (1, 2, 4, 6 mg/L) in the reclaimed water and carried out propose on the calculating method of the optimal chlorine dosage. As the reclaimed water showed a very fast reaction with chlorine at the intial time comparing to that of drinking water, the existing general first-order decay model (Ct = Co(e b)) was not suitable for use. Accordingly, the reduction of residual free chlorine could be estimated in a more accurate way as a result of applying the exponential first-order decay model (Ct = a + b (e b)). (r = 0.872~0.988). As a result of calculating the bulk decay constant, it showed the highest result at 653 day under the condition of 1 mg/L, 25°C for the initial injection whereas it showed the lowest result at 3.42 day under the condition of 6 mg/L, 5°C for the initial injection. The bulk decay constant tends to increase as temperature increases, whereas the bulk decay constant tends to decrease as the initial injection concentration increases. More accurate calculation for optimal chlorine dosage could be done by using the experimental results for 30~5,040 min, after the entire response time is classified into 0~30 min and 30~5,040 min to calculate the optimal chlorine dosage. In addition, as a result of calculating the optimal chlorine dosage by temperature, the relationships of initial chlorine demand (y) by temperature (x) could be obtained such as y = 1.409 + 0.450x to maintain 0.2 mg/L of residual free chlorine at the time after 4 hours from the chlorine injection.