116 



WARREN WISBY 



retention time of 90 minutes was sufficient 

 for the large majority of our experi- 

 ments. The tank was therefore designed 

 to provide a retention time of li/^ hours at 

 the maximum pumping rate of 36,000 gal- 

 lons per hour. It will cover most of the 

 roof of the building and will be shielded 

 from the direct rays of the sun by a per- 

 manent cover, which also acts to prevent 

 dilution by rain water. 



Provision has been made for cleaning by 

 dividing the tank into two parts. Either 

 part can function as a settling tank while 

 the other is shut down. The settled water 

 will be collected in a sump at the end of 

 the tank for final distribution to the lab- 

 oratories. This will ensure a constant head 

 of water to the secondary piping system. 

 In many cases this water will require no 

 further filtration. Nevertheless, unit fil- 

 ters will be generally available, to be used 

 or bypassed as desired. The filter units 

 are plastic, with disposable filter elements, 

 and are similar to those successfully used 

 elsewhere. The cost of the elements is 

 relatively small, they can be obtained with 

 various pore sizes, and should last from 2 

 to 3 days in an average installation before 

 cleaning or replacement is needed. 



Many of the problems of a salt-water 

 system have to do with the corrosive 

 nature of the sea water, while others are 

 due to the erosive effects of suspended 

 materials. A search was instigated to find 

 a pump which would resist the effects of 

 both of these factors. The investigation 

 has narrowed down to a centrifugal pump 

 with a special rubber lining. A total of 

 three pumps will be installed in parallel 

 connection. The pumps will be actuated 

 automatically by a demand signal from a 

 float-type switch sensing the water level 

 in each distribution sump. As many 

 pumps will be in operation as are required 

 to maintain the desired head of water. 



As in our present sea-water system, all 

 piping will consist of straight runs with- 



out bends or elbows. Four-way fittings, or 

 tees will be used at all corners so that a 

 cleaning rod can be inserted easily. It is 

 planned to use unplasticized nontoxic 

 PVC piping both in the primary and in 

 the secondary distribution systems. All 

 valves will be of similar inert materials, 

 either PVC, Teflon, or hard rubber, 

 depending upon their size. Automatic 

 control systems will be provided for reg- 

 ulating the following environmental 

 parameters. (See Addendum on p. 118.) 



Temperature 



A number of thermostatically con- 

 trolled, portable units for heating and 

 cooling the settled sea water will be avail- 

 able for individual use. 



Salinity 



Water conditioning will take place in a 

 mixing chamber before being introduced 

 into the aquariums. Salinity levels will 

 be sensed by means of a conductivity cell, 

 or inductive type cell, and automatic regu- 

 lation applied to the inflowing water 

 supply. Salinity will be reduced by the 

 metering in of distilled water or of fresh 

 water previously passed through a dechlo- 

 rinator. Salinity will be increased by 

 spraying raw salt water into an evacuated 

 chamber with subsequent reoxygenation. 

 A salinity control of ± 1 part per thou- 

 sand can be provided. 



pH 



Adjustment of pH will take place in a 

 tank before the sea water enters the aquar- 

 iums. Measuring electrodes will be glass 

 (Beckman) with a calomel reference. The 

 measured values will actuate the control 

 system so that an acid or a base will be 

 metered into the mixing tank at a rate 

 sufficient to maintain the desired pH. 



Dissolved oxygen 



Measurement and recording of the dis- 

 solved oxygen will be accomplished with 

 either Kanwisher or Beckman type elec- 



