Το θέμα του μαθησιακού υλικού – Φύλλο για τον μαθητή “Regulating pH in fish-holding tanks” – student handout

Γενικές πληροφορίες General Information  
This task is related to the maintenance of appropriate pH level in fish-holding tanks of a fish hatchery unit. This activity reflects one of the jobs that a responsible person of such a unit needs to take into account and is related to a certain extent to the chemistry. The task is simple and can be tackled by small groups of students, while each group has to present its own proposal and solution.  

Το έργο/Η δραστηριότητα The task
In a fish hatchery of gilt-head breams, there are open sea fish-holding cages, and smaller enclosed fish-growing tanks. In these enclosed tanks juvenile fish is growing until it reaches a certain size and then is transferred in the open sea cages. The usable volume of these fish-growing tanks is 18m3. 
Watch the following video: 
https://onedrive.live.com/redir?resid=2BC277A7AE32D507!38782&authkey=!AGIalFqWDudmasM&ithint=video%2cwmv

The video shows the installations of a fish hatchery. In the last scenery an employee measures the pH of the water in the tanks. Note that the appropriate level of pH for the development of fish is naturally that of the sea, about 8,2. The respiration of fish has as a result the decrease of this level. If pH becomes acid enough, then there is a danger fish to die. The value of pH that meets BIOSAFETY* standards for fish well being is about 7,2-7,5 (this also depends on the kind of fish).
Suppose you are the fish hatchery production foreman. You have to think, take actions and report on a number of issues. Discuss in your group the following issues:
•	Appropriate methods to control and regulate the level of pH.
•	Description of what each method implies.
•	Estimation of a viable proposal for a specific case.
•	Exploration of environmental issues.
•	Decision about the selected method.

Your advices should come in form of a report, where you explain your decision and actions that need to be undertaken.  
*BIOSAFETY is a strategic and integrated approach that encompasses the policy and regulatory frameworks (including instruments and activities) for analysing and managing relevant risks to human, animal and plant life and health, as well as associated risks to the environment.