During periods of irregular operation when pH adjustments were 

 being made continuously to the desalination plant to control 

 scale build-up, copper levels became extremely high. Since the 

 continuously recording copper analyzer did not read above 2,000 

 ppb, these changes were not recorded in their entirety and, there- 

 fore, the duration of extremely high copper discharges is not 

 known. Effluent samples taken during the bi-weekly water surveys 

 demonstrated that copper values exceed 6,500 ppb during unstable 

 operating conditions. When pH was lowered, the amount of copper 

 discharge increased. 



In June, 1971, most of the large copper-nickel alloy separatory 

 trays were removed from the deaerator section and replaced with 

 wood trays. After the plant resumed operation, copper levels 

 decreased to a low of 205 ppb. Table III shows the analysis of 

 the major ions in the effluent during July. The plant had operated 

 only twelve hours prior to the sampling and should have been pro- 

 ducing excessive amounts of copper. 



Copper concentrations from July to October varied considerably. 

 July and August had the lowest copper levels observed during the 

 fifteen month study period (310 and 426 ppb respectively). In 

 September, the average rose to 1,024 ppb but levels as low as 

 250 ppb were common. In October, copper levels reached an average 

 concentration of 1,119 ppb but were extremely variable with the 

 lowest concentration being 148 ppb and the highest 5,325 ppb. 



In November, the plant closed down for extensive engineering mod- 

 ifications which would bring about the permanent reduction of 

 copper discharge. Titanium tubing was used to replace the monel 

 tube-bundles in the first tube-bundle and a new boiler plant was 

 installed to minimize shut-down periods because of thermal energy 

 requirements. 



In 1972, the remaining copper-nickel separatory trays were replaced 

 with stainless steel. Unfortunately, the field work for the study 

 was terminated in October, 1971 and the results of the retubing 

 have not been assessed. 



Monthly copper concentrations at all stations in Safe Harbor are 

 plotted in Figure 19. Concentrations of copper were generally 

 higher at deeper stations (Series B, the denser shaded areas on 

 the graph) reflecting a higher percentage of effluent present. 

 In contrast, at Control Station 10, copper concentrations were 

 generally greater in shallower water than deep. When the copper 

 discharge was reduced in July and August, 1971, differences in 

 copper concentrations between shallow and deep stations became 

 less prominent. 



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