1. Introduction

Nosy-be is an exceptional island because of its geology and its relief, that is to say in the island of Nosy-Be, there are 12 great sacred lakes.

The island of Nosy-Be is divided into five (5) arrondissements, so the research is carried out for the borough of BEMEGNONDROBE. The number of inhabitants in this district is given by the following table:

Among the 12 sacred lakes we call lake ANJAVIBE, this lake is located in the borough of BEMAGNONDROBE. It is located in the north of the island. The population in this borough uses this lake as drinking water. So this for cella that we draw from my research aims to analyze the physicochemical parameters and the quality control of this lake called ANJAVIBE to make known the situation of this lake is what drinkable or not.

2. The Characteristics of Lake ANJAVIBE

The study of these parameters is different from other research,

This study consists of four parts, beginning with the bibliographic synthesis and then the results of measurement for the physico-chemical and microbiological analyzes, followed by the interpretation and the discussion of this result, and ends with the conclusion.

3. Bibliographic Synthesis

Water has the liquid, solid and gaseous structure, the general formula is H₂O.

The chemical operation of water: is the dissociation in H + and in OH- ion, the separation of the two ions is measured with the Potential of Hydrogen.

The chemical composition of the water: consists of dissolved gases of base to oxygen.

The water contains several organic materials: in various concentrations, it also contains the organic materials presented in dissolved forms.

4. Norm of Quality

1 - Recommendation of the WHO

2 - Recommendation of EU

3 - Recommendation of the EM

Recommendation of the WHO

Recommendation of the EU

Recommendation of the EM

Metals: may exist in water form trace.

Pollutions: these very dangerous in water it presents in microbe.

Quality standard

The standard of qualities is referred to by the European Union (U.E) recommendation and the World Health Organization (WHO).

5. Analysis Parameters

- Turbidity: it is the transparency of water.

- pH: to know the water is acid, base and neutral, its depends on the variation of this pH.

- Conductivity: allows appreciating the quality of salt dissolved in the water.

- Organic matter: allows estimating the quality of organic matter in water, BOD and COD.

- Salinity: this is the measure of salt concentration in water.

- Alkalimetric title: this is the basic salt content, ie to know the concentration of OH- ion in water.

- Determination of nitrate content: Determination of nitrate concentration in water.

- Total hardness: Determines the calcium and magnesium content in the water.

- Dosages of iron: to know the concentration of iron in water, it is in the form of trace.

- Ammonium: the ammonium ion indicates an existence of pollution in water.

- Sodium: is responsible for the hydro-electrolyte balance.

- Potassium: plays a role as a calcium in human life.

- Calcium and magnesium: concentrations are very high in drinking water.

- Aluminum, Lead and Copper: are lord metals, their existences in drinking water do not accept for international standards.

- Determination of chloride: it is a major ion contained in natural water.

6. Results of Measures

I / -Parameters

1- Temperature

The temperature is in the potability frame, so it is acceptable

2- Turbidity

The turbidity is equal to 1.31 NTU thus acceptable for the international standard

3- The pH

The pH is equal to 7.1 therefore it is acceptable for the quality standard for potability

4- Conductivity

The conductivity is 280μs / cm acceptable for the potability standard

II- chemical parameters

1- Organic materials

Oxygen dissolved the value found is greater than 2mg / l therefore outside of potability standard

2- Salinity

Salinity is zero and therefore normal

3- Title Alkalimetry

The TAC 13.4 ° f almost normal for the potability of water

4- Nitrate assays

Normal nitrate is equal 0.9mg / l water is clear

5- The total hardness

Hardness 28mg / l water is not so so normal

6- Determination of iron

Iron 0 mg / l therefore no trace for water

7- Ammonium

Ammonium 0.01mg / l therefore no pollution water

8- Sodium

Sodium 4.5mg / l very low so the water lacks a lot of sodium

9- Potassium

Potassium 13mg / l higher normal value

10- Calcium

Calcium 35mg / l, the standard is 400mg / l so the water low in calcium

11- Magnesium

Magnesium is 47.5mg / l value is normal for drinking water

12- Aluminum

Aluminum 0mg / l this water no aluminum

13- Copper

The copper value is 0.2mg / l in trace form

14 - Lead

Lead 0mg / l water no danger

15- Determination of chloride

Chlorides 7.1mg / l very low concentration found by international standards

7. Bacteriological Analyzes

8. Quality Control

In quality control, values on physical parameters, chemical parameters and bacteriological parameters are compared with international standards in order to conclude the potability of water.

Physical parameters

The temperature 16°C, turbidity 1.31 NTU, pH 7.1 and conductivity 280 μs/cm [1, 4] are admissible to international standards.

The organic matter such as dissolved oxygen is equal to 2 mg / l, this value is outside for the standard by WHO and EU because the required value is <2mg / l. [5]

Chemical parameters

In general, the results obtained are admissible to the values required by the potability of the water, despite some inadequacies of concentrations such as calcium is 34.5 mg / l, [5-8].

Required value is 400mg / l and the chloride is 7.1 mg / l, the required value is 250mg / l. [9]

Bacteriological analysis

The water of the lake called ANJAVIBE that we will study is not microbial [3].

9. Conclusions

The physical parameters of ANJAVIBE lake exactly meet the WHO and EU standards, chemical parameters meet almost 90% of the requirements for water potability and 100% allowable for microbiological conditions.

Therefore the water of Lake ANJAVIBE used by the population of the 5th Arrondissement named BEMAMGNOBE in the District of Nosy-be is drinkable.