SEAWATER FROM RESERVOIR 



BRINE FROM BRINE TANK 



ELECTRIC LINES 

 PIPING 



NULLMATIC 

 CONTROLLER 



ELECTRICITY 



TO 



AIR PRESSURE 



CONVERTER 



SEVEN DAY 

 CHART RECORDER 



TO LABS 



Figure 6. — Schematic of salinity control system. 



During September-December 1974, two filtered raw 

 water samples and two recirculating water samples 

 (entering the wet laboratories) were taken to determine 

 water quality changes caused by recirculation with 

 changfing biomass. Samples were analyzed for nitrate, 

 nitrite, and phosphate by a state-certified water quality 

 laboratory. Temperature, pH, and salinity were measured 

 at this facility (Table 1). 



The results show no significant increase in nitrite, 

 phosphate, and pH with recirculated water. Nitrate does 

 accumulate at low levels but adjustment of the open flow 

 will keep nutrients at acceptable levels. The December 9 



Figure 7.— Control and alarm panel showing alarm indicators (top), 

 conductivity meters (left), nullmatic controller (bottom center), and 

 chart recorder (right). 



condition indicates the seawater system water quality at 

 near maximum biomass and flow rates. 



At this biomass the oxygen content measured in the 

 effluent of the tanks was 1-3 mg/1 below saturation. The 

 actual maximum biomass the system will maintain 

 depends on the species held, temperature, and stress 

 factors. 



For the past year, although bay turbidities sometimes 

 exceeded 100 Jackson Turbidity Units (JTU, Hach 2100 

 Turbidometer), values in the laboratories never exceeded 

 5 JTU. Because of this, cleaning of lines containing 

 filtered water has been unnecessary. The absolute water 

 clarity is important for the efficient functioning of the UV 

 system (Herald et al. 1970). 



The built-in UV output meter in our model (Refco 

 Model EP-120, 316 stainless steel) indicates whether the 

 unit needs cleaning or lamp replacement. To date, one 

 cleaning has been needed (20% acetic acid soak for 1 h) and 

 several lamps have needed replacement. 



The temperature control has been less than satisfac- 

 tory and will be modified. The high temperature variation 

 of ±2°C is due to the cycling of the compressor through 

 five stages of capacity to maintain the set temperature. A 

 modification is planned whereby a two-way proportional 

 valve controlled by an air-operated temperature controller 

 will direct the ethylene glycol flow into the heat 

 exchanger or a bypass line. This arrangement should 

 allow for precise temperature control (±0.5°C). Plans also 

 call for addition of heating capacity via a large-capacity 

 water heater in the ethylene glycol line. 



Salinity control has been precise (±0.5%o) and has 

 been maintained, although bay salinities varied from 12 to 



