Abstract
A model experiment monitoring the fate of total residue oxidant (TRO) in water at a constant temperature and salinity indicated that it decayed exponentially with time, and with TRO decaying faster in seawater than in distilled water. The reduction of TRO by temperature ( degrees K) was found to fit a curvilinear relationship in distilled water (r(2) = 0.997) and a linear relationship in seawater (r(2) = 0.996). Based on the decay rate, flow rate, and the length of cooling water flowing through at a given temperature, the TRO level in the cooling water of a power plant could be estimated using the equation developed in this study. This predictive model would provide a benchmark for power plant operators to adjust the addition of chlorine to levels necessary to control bio-fouling of cooling water intake pipelines, but without irritating ambient marine organisms.
Highlights
Operation of thermal or nuclear power plants located near the seashore requires massive amounts of water for cooling purposes
The duration of chlorine remaining in the pipeline and discharging trench could be estimated from flow rate and the length of pipeline
We confirmed that the iodine colorimetric method is a feasible approach for determining total residue oxidant (TRO) concentration below 5 mg/L, is extremely precise, and has a stable reaction product for up to 96 hrs
Summary
Operation of thermal or nuclear power plants located near the seashore requires massive amounts of water for cooling purposes. Many sedentary marine organisms, such as barnacles, spirorbis, oysters and bryozoa proliferate on the inner wall of cooling water intake pipelines. Previous studies have indicated that bromine ions in the presence of chlorine would be converted to hypobromic acid and hypobromte, and even molecular bromine [9, 10]. When chlorine is used as an anti-fouling reagent in a power plant, TRO remaining in discharge seawater is almost inevitable. The maximum level of chlorine residue allowed in discharge water in Taiwan is 0.5 mg/L, which is set by Taiwan’s Environmental Protection Administration in 2001. There is an increasing importance to establish guidelines for the addition of chlorine to seawater for power plant operators, as well as to produce a more realistic view of the impact of chlorine on the marine environment. The results from this study provide a baseline for the operator of power plant to balance the tradeoff between antifouling requirements and environmental protection
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