Determination of Requirement for Lime Chloride Amount at Chlorination of Water

The calculation of the necessary amount of 1 % solution of lime chloride for chlorination of 1000 litres (1 cubic meter) of water:

Of three flasks of investigated water to select the one in which the content of residual chlorine is within the limits of 0.3-0.5 mg of chlorine per litre.

To convert the amount of drops of 1 % lime chloride solution added to the given flask at experimental chlorination to milliliters (1 ml contains 20 drops on average). The amount of dry lime chloride in grams necessary for decontamination of 1 m3 of water is determined according to the formula:

 

where:

Х — amount of lime chloride in grams per 1 m3 of water.

В — amount of 1 % solution of lime chloride (in ml) added to flask at experimental chlorination;

1000 — converting per 1 m3 of water;

100 — converting to grams of dry lime chloride.

Conclusion: 1 gram of dry lime chloride per 1 m3 of water is necessary for decontamination of investigated water.

For example: We titrate 200 ml of water in 3 flasks. To the 1st flask we add 2 drops of 0.01 N solution of sodium hyposulphite, to the 2nd — 4 drops and 3 flask — 8 drops of the solution. What is the necessary quantity of dry lime chloride for disinfection of water (in grams per 1 m3 of water)?

Solution

1) 1 ml of 0.01 N solution of sodium hyposulphitum contains 20 drops. To the 1st flask we add 2 drops

1 ml — 20 drops

Х ml — 2 drops

 

2) 1 ml of 0.01 N solution of sodium hyposulphite contains 20 drops. To the 2nd flask we add 4 drops

1 ml — 20 drops

Х ml — 4 drops

 

3) 1 ml of 0.01 N solution of sodium hyposulphite contains 20 drops. To the 3rd flask we add 8 drops

1 ml — 20 drops

Х ml — 8 drops

 

4) Residue of chlorine in each flask is determined according to the formula:

Х = 0.355 ´ A х 5

In the 1st flask: 0.1 х 5 х 0.355 = 0.17 mg of chlorine per 1 litre;

In the 2nd flask: 0.2 х 5 х 0.355 = 0.35 mg of chlorine per 1 litre;

In the 3rd flask: 0.4 х 5 х 0.355 = 0.71 mg of chlorine per 1 litre.

We select flask № 2, where the residual chlorine is within the norm. (N = 0.3 — 0.5 mg of chlorine per litre).

To the 2nd flask we add 0.2 ml of sodium hyposulphite (4 drops).

5) The amount of dry lime chloride in grams necessary for decontamination of 1 cubic meter of water is determined according to the formula:

 

Conclusion

The amount of dry lime chloride for decontamination of 1 cubic meter of water is equal to 10 grams.

 

 

Theme No 9-10.

Hygienic Significance of Soil. Hygiene of Inhabited Locality.

Hygienic Requirements to Cleaning Inhabited Locality from Waste Products

Soil is one of the important objects of environment where the processes of autopurification take place; in the soil many chemical and microbe pollutants can accumulate, getting then into foodstuffs, atmospheric air, surface and underground waters.

The basic hygienic parameters of soil are:

· Porosity. The more the porosity is, the less the water is filtered, and much of it remains in the ground forming marshy soil which is unfavourable for the man.

· Air permeability is connected with porosity of soil — the more the air permeability is, the more oxygen enters the soil and more biochemical processes of autopurification take place;

· Water penetration, i.e. filtration ability — at sufficient values the ground is dry, and reserves of subsoil waters form there.

· Capillarity — the more the capillarity of ground is, the higher the subsoil waters rise.

Structure of the Soil

The soil consists of mineral, organic, mineral-organic complexes, soil solutions, air and soil microflora. These are important parameters for hygienic estimation of soil, their changes can testify to pollution of soil.

In the soil 2 processes constantly take place:

· Disintegration of organic substances into inorganic — nitrification

· Synthesis of new organic substances called humus — humification.

Sharp disturbance of correlation of these processes testifies to pollution.

The soil microflora is characteristic of each kind of soil and is the basis of autopurification processes of soil. It is estimated by total microbe number (TMN) and amount of the basic groups of microbes.

Hygienic Significance of Soil

v Endemic significanceisthe main factor of formation of natural and technogenic biogeochemical provinces with abnormal content of mineral substances that may through foodstuffs and water cause endemic (characteristic for the given district) diseases of the person. The majority of such diseases refer to microelementhoses (classification and representatives — see in the theme on mineral substances).

To artificial biogeochemical provinces now the accumulation of pesticides, heavy metals, etc. in the ground refer. There are data about the interrelation of health state of population in these territories with the level of accumulation of these toxicants in the ground.

v Epidemiological significance of soil

The causative agents of different diseases can get into the ground and long be kept there causing the following:

Ø Intestinal infections — typhoid, paratyphoid, dysentery, cholera, etc.

Ø Anthropozoonoses — anthrax, etc.

Ø Viruses — hepatitis, etc.

Ø Helminthiases — ascaridiasis, etc.

With soil dust the causative agents of tuberculosis, poliomyelitis, respiratory system diseases, etc. can spread.

v Ecological significance of soil

Ø It is the environment of accumulation and circulation in the nature of pollutants of physical, chemical and biological origin;

Ø It is a source of pollution of other environmental objects — foodstuffs, atmosphere, surface and underground water;

Ø It is the environment of utilization and sterilization of solid and liquid waste products, garbage, sewage, animal and human corpses.

At sufficient self-cleaning ability the soil is a primary factor of autopurification of environment.

Ways of autopurification of the soilare the following:

· Decomposition of pollutants by means of mineralization and humification which is due to the soil microflora, О2, enzymatic activity of the soil;

· Adsorption of pollutants by soil particles;

· Washout by subsoil waters;

· Evaporation into air above the soil;

· Oxidation of toxicants by О2 and effect of UVR in higher layers of the soil;

· Neutralization of toxicants in acid or alkaline soil.

Concept of Soil Pollution

By definition of UNEP the ground pollution is chemical substances, biological organisms and products of their vital functions encountered in the ground not in a proper place, time and amount.