1. Treatment of organic impurities and water disinfection:
1.1. Purple pot: (KMnO4)
Purple potion removes organic substances and heavy metals.
For marine resources with high amount of silt, high turbidity, high content of heavy metals. They must be removed before being disinfected.
- Based on the principles of using purple potions according to equations (1) and (2) as follows:
(1) 3Fe (HCO3) 2 + KMnO4 + 7H2O -> MnO2 + 3Fe (OH) 3 + KHCO3 + 5H2CO3
- 1mg Fe2 + / lit = 0.94mg KMnO4
(2) 3 H2S + KMnO4 + S + MnO + 3H2O
- 1mg H2S / lit = 6.19 mg KMnO4 / lit
Normally, the amount of potassium permanganate needed to treat sea water from Vung Tau to Ca Mau is from 0.5 to 2 mg / liter.
Sea water after the use of purple pot for treatment will have a purple color but quickly lose color and precipitate. If the amount of potassium is sufficient, after 24 hours the water will be clear.
1.2 Water treatment by EDTA
In addition, EDTA can be used at a concentration of 5-10ppm to treat water in the larval rearing tank.
1.3. Disinfecting water with Chlorine
Chlorine Ca(OCl)2, when mixed with water will exist in the form of Cl2.HOCl.OCl.Cl2 has a high disinfection effect.
Regular Commercial Chlorine 70% means that 1 gr of Chlorine contains 0.392 Cl2
In practice, chlorine is commonly used at concentrations of 15-25ppm (equivalent to 5.8-9.8gr Cl2.) After chlorine treatment, the excess of Cl2 in water, excess excess Cl2 in water will also cause For shrimp and larvae larvae, the excess of Cl2 must be removed by thiosulphate prior to the introduction of water into the shrimp culture tank:
Cl2 + 2Na2S2O3.5H2O -> Na2S2O6 + NaCl + 10H2O
* How to test excess CL2 in water:
Take 10-20ml of treated water Chlorine 1 - 1 drops of Orthotolidin reagent 1% if water appears yellow is left over Cl2, if colorless water proves that no residual Cl2.
* According to experience, after 24 hours treatment of Chlorine, Thiosulphate is equivalent to the amount of Chlorine used to disinfect excess Cl2 in water.
2. Mechanical Filter
The water in the settling tank has been removed from the organic matter and the sterilization will be filtered through the sand filter tank.
Normally, the sand filter tank has a volume of 2m3 using 300kg of sand with a diameter of 0.5-1mm 100kg of stone 1-2.
3. Procedures for water treatment in hatcheries
Step 1: Pumping water from the sea to the settling tank
Step 2: Treatment of purple pill (within 24 hours)
Step 3: Pumping water from the settling tank to the treatment tank.
Step 4: Chlorine treatment in the treatment tank (for 24h)
Step 5: Pumping water from the settling tank to the cistern
Step 6: Water from the filter tank flows automatically to the tank as required.
