failures. Almost a year went by before it was properly corrected and 

 began consistantly producing reliable results. The Hydrolab IV temperature 

 and conductivity modules worked well but the pH probe suffered from large 

 electrostatic charges generated by the seawater flowing through the 

 desalination system. The pH measurements were, therefore, made twelve 

 times daily by testing a sample of the effluent on a Beckman laboratory 

 pH meter. 



Independent samples of well water and effluent were taken twice a week 

 during normal field collections. These samples were analyzed along with 

 the samples from the harbor (see below) for temperature, salinity, 

 alkalinity, and total copper. The effluent was also sampled quarterly 

 for emission spectrographic and atomic absorption analyses of the major 

 elements. Additional samples were taken periodically to examine heavy 

 metal discharge following periods when the plant had been closed for 

 maintenance and descaling. 



Every two hours, the plant operators recorded maintenance data for the 

 desalination plant including temperatures, water flows and pH readings. 

 These measurements provided the most reliable data on the long-term 

 operation of the facility and were the source of the averages presented 

 in the report showing long-term trends in parameters of the effluent. 



Samples taken and analyzed concurrently with the field station collections 

 were used for estimation of the percent effluent at the stations and as a 

 cross-check for the data calculated from maintenance records. 



Salinity, temperature, and pH were calculated from the maintenance books. 

 Since salinity measurements of the blowdown were not taken by the 

 plant operators, they were calculated by comparing the total water 

 flowing through the system, the amount of freshwater being produced, and 

 the salinity of the well water. Well water salinity averaged 38.266 o/oo 

 with a standard deviation of only 0.01 o/oo. 



Using the observed salinity of the well water (S ) , the total amount of 

 seawater pumped (T) , and the amount of water produced (P) , the salinity 



of the effluent (S ) was calculated as: 



e 



T 

 S = S 

 e w 



T P 



Temperature of the effluent was recorded by laboratory-grade glass 

 thermometers at the point of discharge into the open sump. Two separate 

 readings were taken; one for the stage 50 brine (brine blowdown temperature) 

 and one for the reject water. Since the volume of the reject water was 

 known to be one third the volume of the brine blowdown (under normal 

 operating conditions) the temperature of the combined effluent (_T ) was 

 calculated from the temperatures of the brine blowdown (T, ) and the reject 



water (T ) using the formula: 



-b' 



T + T 

 T = ^b r 



e „ 



19 



