Process for water purification from nitrites

Description:

The invention relates to a process for the purification of nitrifying water and can be used in the process of treating surface and mine waters at wastewater treatment plants or for purifying water in domestic conditions.

Water supply in the Republic of Moldova is made in proportion of about 30% of surface water and about 70% of groundwater. It has been found that about 50% of groundwater does not meet the standards set for drinking water, with quantities of fluorine, iron, manganese, ammonium ions, nitrides etc. being recorded. The ammonium ion in aerobic conditions is biologically oxidized and transformed into nitrif ions, which leads to their concentration in drinking water. It is well known that nitrif ions are toxic and cause inetglobinin disease, which particularly attacks young people. Taking into account the above, the elimination of nitrite ions from water is a current problem and of great importance, especially for rural localities.

It is known the process of purification of waters containing nitrifions, which consists in the processing of water with reducers, for example with ascorbic acid (AAs) in the molar ratio [AAs]: [NO₂] = 10: l. Its processing time is 30 .. .40 min. In the aforementioned process the nitrification ions are transformed into nitrogen oxide (II) [1].

The process is similar to the use of sodium dihydroxyfumarate as a reducing agent [2].

The disadvantages of these processes are that in the drinking water large quantities of organic substances are added, which leads to the increase of the chemical and biological oxygen consumption, the decrease of the pH of the water, thus causing the quality of the drinking water to worsen. The proposed reducers are also expensive enough to be used extensively.

Also known is the process of purification of waters containing nitrides, consisting of oxidation of nitrides ions with hydrogen peroxide [3].

The disadvantage of this process is that the oxidation process proceeds slowly at low concentrations of nitrites and it is difficult to measure the amount of hydrogen peroxide in the purification system.

Also known is the process of purification of waters containing nitrides, hydrogen sulphide, manganese and iron ions, which consists of nitrification oxidation by air bubbling [4].

The disadvantage of this process is that the process of oxidation of the nitrites runs very slowly and is carried out at high pressures.

Also known is the process of purification of nitrify ion waters, which consists of air oxidation of nitrify ions into nitrite ions on a catalytic support of activated carbon obtained from metal impregnated by-products [5].

The disadvantage of this process is that the process is discontinuous in static conditions and is durable, and the catalyst used is relatively more expensive than industrially active coal.

The problem solved by the invention consists in the elaboration of a process for the purification of the water of nitrifying ions under dynamic conditions by oxidizing the nitrides with accessible and cheap reagents.

The problem is solved by the use of air as an oxidant, and the oxidation process is catalyzed by the industrial coal intact, in a fluid bed reactor having catalytic support for the coal mines.

The process of purifying the nitrifi waters consists of aerating the water in the presence of the activated carbon, at the same time the granulated activated carbon АГ-5 is used, the aeration of the water is carried out for 120 ... 180 min, with an air flow of 0.7 .. .08 L / hour per 100 g of activated carbon, and the mass ratio of activated carbon: water is 1: (9 ... 10).

In the process of catalytic oxidation the nitrites are oxidized by oxygen from the air to the nitrites.

The claimed process is effectively catalyzed specifically by the AG-5 granulated activated carbon, well known to specialists in various fields in which activated carbon is used.

The result of the invention consists in the fact that the nitrif ions are oxidized into the nitrite ions, the admissible limit concentration of which is 45 ing / 1, which is much higher compared to the admissible limit concentration of the nitrites in the water.

MD 3567 G2 2008.04.30

The invention is explained by the drawings in figures 1 and 2, which represent:

FIG. 1, diagram of the installation for water aeration under dynamic conditions with fluidizing bed of catalyst;

FIG. 2, the degree of purification of nitrate ion waters according to the aeration time.

The process is performed with the help of the installation mentioned in fig. 1, which consists of an air pump 1, an air meter 2 for regulating the flow of air bubbled, a reactor 3 with a glass filter 4 to support the catalyst layer. Water samples during bubbling are collected using tap 5.

Example of embodiment of the invention

AG-5 type granulated activated carbon, which is well known in the CIS and other states by specialists in the field of water treatment technologies, has been used. О 100 g of activated carbon AG-5 was boiled for 10 min to replace the air in the carbon absorber. Subsequently, the activated carbon was passed into reactor 3 with a diameter of 8 cm and a height of 30 cm. 980 ml of NaNO solution were stained in the reactor₂ with the initial concentration of nitrites of 10.26 mg / L. Air was blown through the reactor at a speed of 0.75 L / hour using the air pump 1 and the air meter 2.

Over time intervals of 2, 15 30 and 60 min through tap 5 samples were collected to determine the nitrite concentration. The obtained results are shown in fig. 2.

The analysis of the results presented in fig. 2 shows that, when performing the proposed process, a purification degree of 80 ... 85% is reached when air bubbling for 2 ... 3 hours of water containing nitrates in concentrations comparable to those of natural waters.