Abstract
The effects of Biofouling control with intermittent ozone injection in model water pipes were investigated. The experimental model pipes used acrylic test pipes (1 m in length) with points equivalent to 150 and 300 m in actual pipes. Fresh cooling water was passed through the model pipes at a velocity of 1.5 m/s. The results of the experiment are summarized below. (1) The dissolved ozone concentration in the water rapidly decreased by a half in about 50 s because of the self decomposition of the ozone due to the high water temperature of 30°C and a pH of 8. (2) After no ozonation for 35 d, the average dry weight of fouling in the acrylic test pipes covered with aluminum film was about 5.4 mg/cm2 at each point; nearly 2.5 times higher than those which were not covered. The fouling consisted of about 60% organic matter. (3) By injecting ozone into the fresh water twice daily at 12 h intervals for 5 min each at a dissolved ozone concentration of 10 mg/L, the acrylic test pipes at points equivalent to 150 and 300 m were almost completely free from fouling after a test run of 35 d. The residual ozone concentration at a point equivalent to 300 m was about 0.3 mg/L. (4) The fouling in the acrylic test pipes at points equivalent to 150 and 300 m after 35 d without ozonation were almost completely peeled by an intermittent ozone injection of 10 mg/L for 5 min twice daily at 12 h intervals for 21 d.
