SEA- WATER SUPPLY IN THE TROPICS 



115 



supplied with running sea water, and each 

 level is connected by a drain hose to a gut- 

 ter which carries the waste back to the 

 bay. 



The feature of the distribution system 

 which is considered to be the most impor- 

 tant is that nowhere in the entire system is 

 an elbow joint used. Where it is necessary 

 to turn a corner, a four- way fitting is used 

 and the unwanted openings are capped. 

 Thus, any section of pipe can be 

 thoroughly cleaned with a plumber's 

 "snake" merely by removing the cap that 

 leads in a straight line to the proper sec- 

 tion. We have found through experience 

 that such cleaning must be part of the 

 regular maintenance schedule owing to 

 the rapid growth of settling organisms in 

 the tropics. 



SALT-WATER SYSTEM FOR NEW 

 BUILDING 



The sea-water system designed for the 

 new laboratory remains relatively un- 

 changed from this original concept. It 

 will, of course, be much larger and more 

 sophisticated as to controls, but the basic 

 principles have been judged sound and 

 time-tested and will be adhered to. All 

 primary and secondary piping will be of 

 PVC plastic, including the valves, and 

 will be installed in duplicate down to the 

 final distribution level. Provisions will be 

 made to keep unused portions filled with 

 fresh water to destroy any marine orga- 

 nisms which may have settled during their 

 periods of use. Our experience has shown 

 that if this is done bimonthly, the major- 

 ity of settling organisms will be so small 

 that the calcareous shell will be removed 

 from the walls of the pipe when the orga- 

 nism dies. Provision will also be made for 

 flushing the used portion of the system 

 with a fast flow of sea water daily, thus 

 preventing sediment from accumulating 

 in the piping in use. 



The question of filtration was again ex- 



amined in detail and the conclusion was 

 the same as that arrived at when the ex- 

 isting system was planned — that a settling 

 tank on the roof was most suited to our 

 needs. Our water supply was first sub- 

 jected to scrutiny. It was found, by drill- 

 ing test wells, that our underground salt 

 water, although crystal clear, contained so 

 much dissolved HoS as to render it unsafe 

 for use with small marine organisms, even 

 after treatment. Also, while it might be 

 possible to maintain living fishes in this 

 treated water, whether they could then be 

 considered "normal" in activity and in 

 behaviour is questionable. 



Mechanical and biological filters were 

 also discussed and discarded; the former 

 because of the difficulty of cleaning and 

 the frequency with which this would be 

 necessary with our water conditions, and 

 the latter because of the undesirable con- 

 tribution of additional larvae and eggs 

 to the already present problem. It was 

 also decided that the settling tank should 

 be on the roof, as at present, for several 

 reasons. First, pressure systems, the other 

 alternative, are not satisfactory in the trop- 

 ics because of the danger of supersatura- 

 tion of dissolved gases with even slight 

 warming of the water, with resultant 

 trauma to the tissues of the experimental 

 organisms. Second, our ground water is 

 so near the surface as to make digging 

 difficult. Third, a large underground tank 

 would have to be kept filled with water 

 in order to prevent its "floating," especially 

 in the event of storm flooding, and this 

 would make cleaning difficult. Fourth, a 

 ground surface tank would take up valu- 

 able space and would necessitate two sets 

 of pumps, one to pump into the tank and 

 one to pump from the tank to the roof of 

 the building, where a gravity tank would 

 be installed. 



Tests were again conducted on the rate 

 of settling of the materials suspended in 

 the intake water, and it was found that a 



