Maximum permissible concentrations (MPC) of harmful elements are the norm of sanitary-hygienic rules established by state acts. Failure to comply with the limit values indicated therein is an offense for which violators are held accountable in accordance with the law. The MPC norm in water gives instructions on those limit values of pollutants, the content of which does not entail damage to human health or life.
The main sources of toxic elements are the numerous functioning enterprises of the industrial complex. Their emissions pollute air, soil and water quite strongly. Chemical elements that have a negative impact on our environment, it is customary to divide into groups depending on the degree of their danger to humans. These include substances that have a danger:
- emergency;
- high;
- moderate.
There is also a group of hazardous elements.
MPC in water of various chemicals are reflected in specially designed tables. There are also various formulas, the use of which allows the calculation of the maximum tolerance of toxins. They are used by specialists to carry out control measures for water used by humans. Such actions can be carried out by any of us. To do this, it is enough to analyze the state of drinking water in your home and compare it with the permissible norms for the presence of various elements in it. For example, the content in milligrams per liter should not be higher:
- dry residue - 1000;
- sulfates - 500;
- chlorides - 350;
- copper - 1;
- zinc - 5;
- iron - 0.3;
- manganese - 0.1;
- residual polyphosphates - 3.5.
The total hardness of the water should not exceed seven milligrams per liter.
Of great importance is the control over the state of the soil. It is the earth that serves as the accumulator and filter of various compounds. The maximum permissible concentration of wastewater, which is constantly discharged into the soil, must also comply with the standards, since the constant migration of harmful substances in its upper layers pollutes the entire environment quite strongly.
According to sanitary standards, in the soil can be no more than:
- 0.02 mg / kg benzapyrene;
- 3 mg / kg of copper;
- 130 mg / kg nitrates;
- 0.3 mg / kg toluene;
- 23 mg / kg of zinc.
If the MPC is exceeded in water, bodies involved in environmental monitoring will determine the cause of this phenomenon. Quite often, the increase in the amount of chemicals in nature is influenced by ordinary household waste. Particularly acute is the problem of cleaning water bodies from phosphate and nitrogen compounds. In order to solve this problem, three different approaches can be used:
- chemical;
- biological;
- a combination of the first two methods.
Bringing the maximum permissible concentration in water to a standard value using chemical purification involves the formation of metal phosphates, which, being insoluble, settle on the bottom of a special tank. This process occurs using reagents. The use of chemical cleaning is widely used in industrial enterprises. Carrying out these works is possible only by specially trained employees.
If phosphorus or P-bacteria are used in water treatment, this method is biological. This is a modern, natural approach to avoiding excess MPC. Special zones of treatment tanks are supplied alternately with aerobic and anaerobic bacteria. This method is used in biofilters, septic tanks and aeration tanks.
The combination of biological and chemical methods is used in treatment systems, where it becomes necessary to accelerate and strengthen the decomposition of sewage.