Semiclosed Seawater System With Automatic Salinity, 

 Temperature, and Turbidity Control 



SIDKORN' 



ABSTRACT 



The new seawater system at the Southwest Fishery Center, Tiburon Laboratory, is described. The 

 system delivers up to 450 l/min of filtered, ultraviolet sterilized, temperature- and salinity -controlled 

 seawater suitable for extended holding of marine fish and invertebrates. Unique aspects of the system 

 including provisions for open and/or closed circulation, and the pneunutic salinity control components are 

 described in detail. The design of this facility may offer ideas to others desiring near-oceanic quality 

 seawater from marginal sources. 



INTRODUCTION 



The purpose of this paper is to describe the new 

 seawater facility of the National Marine Fisheries Service 

 (NMFS), Southwest Fisheries Center, Tiburon Labora- 

 tory. Special emphasis is placed on the salinity control 

 components and design features that allow for either open 

 or closed circulation. I hope this information will assist 

 other facilities with water supplies varying in tempera- 

 ture, salinity, and turbidity, in their effort to obtain 

 near-oceanic quality water. 



This facility is located on San Francisco Bay where 

 water conditions vary considerably in temperature, salini- 

 ty, and turbidity, partially caused by runoff from the 

 Sacramento-San Joaquin rivers. The former seawater 

 system, operating from 1967 to 1971, did not control 

 temperature or salinity and had a limited filtering 

 capacity. Fouling of waterlines and tanks, wide fluctua- 

 tions in temperature (range 9°-20°C) and salinity (range 

 2-30%o>, and bacterial disease problems made research 

 impossible during certain times of the year. This facility is 

 used for physiological research and needs a system that 

 supplies water of near-oceanic quality with constant 

 physical conditions. 



Final specifications and design work were completed 

 by consulting engineers. The system was constructed from 

 November 1972 to April 1973. 



The new seawater system (Fig. 1) is a semiclosed 

 system which can circulate 450 l/min of filtered, sterilized, 

 temperature- and salinity-controlled water. Most of the 

 system is duplicated to facilitate repairs and cleaning with- 

 out disruption of the waterflow. 



Due to the high cost of salinity and temperature 

 control, most of the water is recirculated. However, some 

 open circulation is required when toxic effluents from 

 experiments are involved and to insure that problems 

 associated with recirculating water do not occur. After 

 water has been recirculated for extended periods through 

 tanks containing a biomass, nitrates accumulate, trace 



'Southwest Fisheries Center Tiburon Laboratory, National Marine 

 Fisheries Service, NOAA, Tiburon. CA 94920; present address: Auke 

 Bay Fisheries Laboratory, National Marine Fisheries Service, NOAA. 

 P.O. Box 155, Auke Bay, AK 99821. 



elements may be lost, and pH may change. Therefore, we 

 always maintain at least 10% of the total flow to open 

 circulation. Toxic effluents are filtered through activated 

 charcoal before being discharged. 



FLOW DESCRIPTION 



Seawater is pumped by one of two centrifugal pumps 

 (Ace 3 horsepower, hard rubber [Fig. 2)), through a 

 two-stage, automatically backflushing, high-rate sand 

 filter (Baker Model HRB-30). From the filter, the flow is 

 directed to either the sump tank or back into the bay by 

 an electrically actuated valve, which is controlled by a 

 level indicator in the reservoir (Fig. 1). This is done to 

 prevent excess water from entering the system. Dual 

 3-inch PVC (polyvinyl chloride) lines allow for cleaning of 

 lines and changing of the pump. 



The 600-liter epoxy-lined concrete sump tank collects 

 new filtered water and water that has been recirculated 

 through the laboratories. As the water level rises, one of 

 two 10-horsepower centrifugal pumps (Allis Chalmers 

 Model F-4, 316 stainless steel) is activated by a float 

 valve. Water is pumped through a second single-stage 

 sand filter (Baker Model HRB-36) to the 53,000-liter 

 reservoir (Fig. 3). The water enters the reservoir through 

 a redwood splash tray aerator patterned after a similar 

 design at the Southwest Fisheries Center, La Jolla, Calif. 

 (Lasker and Vlymen 1969). 



The concrete reservoir is epoxy-lined and is divided by 

 a concrete wall into two sections. Water can be valved to 

 enter and leave one or both sides. This allows for the 

 cleaning of one half of the reservoir without disrupting the 

 flow through the system. The capacity of the tank allows 

 for a 2-h full flow reserve in the event of a failure. By 

 reducing flow rates to 112 l/min this reserve can be 

 extended to 8 h. 



Water flows (up to 450 l/min) by gravity from the 

 reservoir to the wet laboratories passing through: an 

 ultraviolet (UV) sterilizer; a heat exchanger; and tempera- 

 ture- and salinity- measuring probes. The flow is then 

 directed into tanks and aquaria as needed (Fig. 4). 

 Depending on the need for open or closed circulation, the 

 effluent line is valved to direct flow into concrete trenches 



