Oxygen balance of the P.H. Robinson Generating Station Cooling Water Canal System
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Measurements of dissolved oxygen concentrations were made at three sample points in the cooling water supply system for the P.H. Robinson Generating Station. The measurements were taken at the intake to the station and at two discharge points above and below the drop structure on the discharge canal. The main study was made during a 24-hour period on May 27-28, 1969. Additional measurements were taken at the intake point and the discharge point above the drop structure on August 12, 1969, and also on August 19, 1969. These measurements were made to establish reliable patterns and to supplement the observations taken on May 27-28, 1969. The dissolved oxygen concentrations were determined with a Precision Scientific Cell Oxygen Analyzer. Measurements were made at two-hour intervals at each of the three chosen sample points in the cooling water supply system. The most significant conclusions derived from this study area as follows: - dissolved oxygen content showed similar diurnal variations at the three sample points. - stratification of the water at all sampling points was relatively minor. - there was approximately a ten percent increase in the daily average dissolved oxygen concentration between the plant intake and the drop structure. This was apparently due to photosynthetic oxygen production within the discharge canal which resulted in daily average dissolved oxygen concentrations above saturation. - there was approximately a five percent decrease in the daily average dissolved ocygen concentration across the drop structure primarily because the daily average concentration above the structure was higher than saturation. When the water is supersaturated, the drop structure acts to remove oxygen and the water thus approaches saturation. These periods of desupersaturation are minor and not considered harmful. - although the contribution is minor, the agitation produced by the drop structure always adds to the oxygen content whenever the water is less than saturated. The drop structure does not produce a sufficiently vigorus agitation to introduce significant amounts of oxygen. - the cooling water canal system plays a relatively minor role in the overall oxygen balance of Galveston Bay from the standpoint of artificial addition of oxygen. However, it appears that, in terms of dissolved oxygen, the water from Dickinson Bayou may be of better quality than that in Galveston Bay. Thus, the transfer of good quality water into Galveston Bay is beneficial.