Design Concept of Two Tank Reservoirs to Maintain pH Value for Tiger Prawn

Shrimp culture is the fastest growing sector of the aquaculture industry in Malaysia. In culturing tiger prawn, the pH level needed for water is around 7.0-8.5. Currently, prawn farmer in Malaysia still using a manual method to control the water pH level by adding chemical (Lime), in which, the process required constant monitoring and control by labor. Since the prawns are so sensitive on pH level, an automatic pH control system is required to maintain the water pH automatically and precisely. This research was conducted to design a system that can control and provide feedback on the changes of pH level and been implemented at the reservoir tank that can act as water storage tank and prawn pond. Control system and pH sensor are the important components in controlling the pH level. Input from pH sensor was processed by controller. Moreover, after an error is detected by controller, the correction will be delivered to the system as a feedback process. Nitric acid with concentration of 0.001M was added to 25 liter water in tank 1 so that the pH level is decreased to pH 3.00. Different concentrations were used for slaked lime; 0.5M, 0.4M. 0.3M, 0.2M and 0.1M, to increase the pH from acid to slightly alkaline in the range of pH value 7.00-8.50. Slaked lime was pumped to Tank by water pump and it will stop if the pH level reaches the setting level. The time for the system to recover from pH 3.00 to 7.00-8.50 was recorded. The results shows that slaked lime with the concentration 0.5M has the fastest recover time which was 29s follow by 0.4M in 69s, 0.3M in 92s, 0.2M in 151s and 0.1M in 252s, respectively.