The way to obtain drinking water


 

(57) Abstract:

The invention relates to the field of water treatment, industrial and domestic wastewater, in particular to a multi-stage water treatment, and can be used for potable water by cleaning of natural surface and groundwater. The objective of the invention is to improve the quality of drinking water by reducing secondary contamination of water by toxic products (HOS), formed during purification of natural water containing organic compounds. To solve this problem, a method to obtain drinking water, consisting in the processing of the original natural water oxidizing agent is ozone and subsequent chemical processing mode pressure flotation using as a flotation reagent coagulant, repeated treatment with the oxidant is ozone, filtration through active carbon and disinfection of treated water oxidizing agent is chlorine in the ratio of oxidants ozone : ozone : chlorine, equal 1 : (1-4) : (0,3-1,0). Using the proposed method improves the quality of drinking water, which is characterized by a decrease, see HOS 4 to 8 times. 1 C.p. f-crystals, 2 tab.

The invention relates to the field of treatments is Sovana for potable water by cleaning of natural, surface water and groundwater.

Numerous technological scheme of potable water, based on the processes of oxidation, coagulation and filtration in their various combinations, depending on the original composition of natural water.

So, there is a method to obtain drinking water using coagulation, sedimentation, chlorination, filtration and ozonation [F. A. Shevelev, G. A. Orlov. The water supply of large cities in foreign countries. - M.: Stroiizdat, 1987. - 351 S., S. 24 - 28]. The source water enters the mixing chamber, where it is processed coagulation-solution of aluminum sulphate at the rate of 10 - 20 mg/DM3and is routed to the settling tanks, the average residence time of water in which is equal to about 7 days. Before the last tank in the water re-injected a solution of aluminum sulphate at a dose of 10 - 20 mg/DM3then the water enters on the mesh drum filters and chlorinated doses of 5 - 10 mg/DM3followed by treatment with aluminium sulphate (third time) and activated kremnekislotnosti. Dose reagents are, respectively, 10 - 20 and 0.5 - 3.0 mg/DM3. After passing rapid filters, consisting of quartz sand grain size is tee filter, up to 10 m/h, the filtrate is treated with ozone and sent to the clean water reservoir. Before serving in the network, the filtrate is disinfected with chlorine (about 0.5 mg/DM3).

The above method (technological scheme, methods, operations) was used for preparation of drinking water from natural water of the Dnieper river. Dnieper water is characterized by high content of organic substances, mainly humic compounds. Our studies have shown that chlorination of water (7 mg/DM3) before the third treatment coagulant when the original color 53o, turbidity 4.4 mg/DM3and the content 106,3 mg/DM3the amount of humic compounds and fulvic acids (G+f) 15 mg/DM3the amount of aldehydes and ketones (a+C), COD = 36 MgO2/DM3and < 2 mg/DM3chloroform (hereinafter composition 1) leads to the formation of toxic chlorinated organic compounds (HOS) - chloroform, which are almost difficult to remove in subsequent stages of processing water and come in purified water. The concentration of chloroform in the received drinking water is 197 mg/DM3that is 3.3 times the maximum permissible concentration of 60 g/DM3[N. G. The Rybalsky, O. L. Jackets and other Environmental aspects of examination of inventions. Spapr also contains quite a large number of phyto - and zooplankton and microorganisms, for the removal of which in the traditional processes of coagulation, sedimentation takes a long time, large scale structures, which in turn requires a large space.

The disadvantages of this method are secondary pollution received drinking water organochlorine compounds, reducing the efficiency of purification from the source of organic compounds, the duration of the treatment.

There is a method of preparation of drinking water, consisting in preglomerular river water, chemical processing, filtering the clarified water, treatment of leachate by ozone followed by sorption filters with granular coal [Level and indicators of development of housing and communal economy of foreign countries: proceedings of the Academy of Municipal economy named. K. D. Panfilov /lecture notes A. K. H. - M., 1975, vol. 114, S. 35 - 38]. Predhlorirovanie water exercise dose corresponding to the break point. Then the water is fed to the mixers with mechanical agitators, where dispensers impose solutions of aluminium sulphate and activated silicic acid. After chemical treatment of the water enters the clarifiers with suspended sediment type "Pulsator". The clarified water is sent to the IC is anyh filters up to 9 m/H. After treatment of leachate by ozone water is rapid filters, granular activated carbon layer 1300 mm and the size of the grains 0,63 mm, and then enters the fresh water tank.

The application of this technological scheme for obtaining drinking water from the Dnieper showed the following. In the process of predhlorirovanie river water are formed organochlorine products, inefficiently removed in the subsequent process of coagulation and ozonation chlorinated water exacerbates secondary contamination of water in light of the formation of toxic organic substances more dangerous to human health than the original substances. So, drinking water is obtained from R. Dnieper (part 1), contains HOS-chloroform in the amount of 235 g/DM3that is 4 times higher than the MAC, which is the main disadvantage of preventing the use for drinking water from natural water with high content of organic impurities.

Closest to the invention to the technical essence and the achieved effect is a well-known way to obtain drinking water, where the river water is treated with ozone and served in a liquid reservoir. Duration prebivalista coagulant-aluminium oxychloride and chlorine dioxide for pre-chlorination. The dose of chlorine dioxide does not exceed the 4.7 mg/DM3. Next, the water passes through the camera flocculation, equipped with a mechanical stirrer, stacked clarifiers and rapid sand filters. The filtering rate is 9 m/h, the thickness of the load 1.4 m with an average grain size of grains of sand 1 mm Filtrate is re-processed with ozone and served on sorption filters loaded activated carbon. The filtering rate is 9 m/h, the thickness of the load 1 m with an average particle size of coal particles 1 mm After the carbon filters in the water for the third time injected ozone. The average dose of ozone is equal to 3.8 mg/DM3including for pre-ozonation - 0.8 mg/DM3. For the final (third) ozonation dose of ozone determined on the basis of ensuring the residual ozone at the level of 0.4 mg/DM3within 4 minutes the Final water treatment process is chlorination of small doses of sodium hypochlorite prior to feeding into the clean water reservoir.

As follows from technical nature, the known method provides for triple ozonation, predhlorirovanie and disinfection with chlorine during drinking water. However, it is known that the combination of ozonation and chlorination river in their drinking water [Alekseeva L. P. The effect of the combination of ozonation and chlorination of water on the formation of chloroform// Chemistry and technology of water. - 1986. - 8, N 5, S. 62 - 64], as confirmed by our data.

During the preparation of drinking water from water R. the Dnieper, which contains natural organic compounds (humic and pulvinate acid), using a known method, chlorination ozone treated water and seasoned for a long time leads to the formation of large amounts of toxic chlorinated organic compounds which are not removed in subsequent processing steps (koagulirovannogo, sedimentation, filtration through sand filters). Re ozonation of the filtrate resulted in a further significant increase in the concentration of toxic products, i.e., the combination of ozonation - chlorination-ozonation during the processing of the Dnieper water (part 1) leads to secondary pollution of the treated water by toxic substances, and in quantities exceeding MPC: the content of chloroform in drinking water is 163 mg/DM3.

In addition, the process of obtaining drinking water from R. Dnieper by a known method is characterized by relatively great length is the (> 120000 m3/day) will require three-dimensional structures, which occupies a large area.

Thus, in the prior art, it follows that the known methods of preparation of drinking water does not solve the problem of improving water quality by avoiding secondary pollution of water generated during the processing of oxidizers toxic products.

Object of the invention is to provide such a method of obtaining drinking water by treating the water with ozone in several stages in combination with physico-chemical processes, in which the changing conditions of chemical treatment and processing of oxidant would improve the quality of drinking water by reducing secondary contamination of water by toxic products formed during purification of natural water containing organic compounds, as well as a significant decrease in the duration of the process of obtaining drinking water by accelerating coagulation and settling.

To solve this problem, a method for obtaining potable water system, including source water oxidant is ozone, followed reagent treatment, re-treatment with oxidant is ozone, filtration hereandnow treatment is carried out in the mode of pressure flotation, and as the flotation reagent used coagulant, and the dose of oxidant at each of the stages is chosen from the ratio of ozone:ozone:chlorine, equal 1:(1-4):(0,3-1,0), used flotation concentration of 40 - 60 mg/DM3.

We found that the claimed ratio of the doses of ozone:ozone:chlorine selected from the conditions ensuring the deep purification of water from organic substances and disinfection, preventing re-contamination of treated water organochlorine compounds.

The claimed ratio of the doses of ozone is optimal:

- to ensure the necessary depth of the oxidation of natural organic compounds (humic acids) to carboxyl compounds, which effectively removed during the subsequent coagulation. So, for example, formed as a product of oxidation of carboxylic acids enter into complex formation with ions of aluminum (coagulant) and form insoluble compounds that are centres of further crystallization, which contributes to a deeper flow of the coagulation process;

- for the preparation of water contained in the remaining amount of organic compounds to effectively biodegrade in the loaded activated carbon.

Zachowania organochlorine compounds and to provide the necessary degree of disinfection of water.

It should be emphasized that the deep purification of water from organic and suspended solids, aquatic organisms and algae is achieved by the combination of the proposed processing modes ozone with carrying out chemical treatment in the conditions of pressure flotation using as a flotation reagent coagulant. Such is the nature of the reagent processing eliminates predhlorirovanie raw river water and use only ozonation. Due to the intensification of the processes of coagulation, driven mode flotation processing, the processing time is reduced from 3 to 4 hours when using the traditional technology of coagulation water treatment up to 20 - 30 minutes

It is very important that in the process of flotation coagulation is effective removal of blue-green algae, which are easily pop up and removed. This prevents putrefaction processes in stagnant zones and biological fouling treatment facilities.

The result of the complex technological scheme of potable water is also reduced structures occupied land area, reducing investment.

Thus, the claimed set of essential features of the method of receipt is ltate - preventing re-contamination of water by toxic compounds formed during processing of the source water, which provides a substantial improvement in the quality of drinking water, as well as reducing the time consuming process of obtaining high-quality drinking water while reducing the volume of buildings and the spaces they occupy.

The method is implemented as follows.

For drinking water treatment is subjected to natural water R. Dnieper containing 106,3 mg/DM3the amount of humic compounds and fulvic acids (G+f), 15,0 mg/DM3the amount of aldehydes and ketones (A+K) < 2 mg/DM3chloroform, COD = 36 MgO2/DM3.

The water is treated in the following sequence of technological operations. Water in the amount of 15 DM3put in the contact tank, which represents a hollow column with a bubbler at the bottom, and is subjected to ozone treatment with ozone dose of 3.3 mg/DM3within 7 minutes the Ozone receive laboratory ozonizer with a capacity of 10 g/h production OP the Bureau of the Institute.

Then ozonated water is subjected to the reagent processing mode pressure flotation by directing water consistently at smesitel the>of coagulant solution of aluminum sulfate with an initial mass concentration of 10 mg/DM3. Mixing water with coagulant is carried out at a speed of 60 rpm for 5 minutes, Treated with coagulant water enters the chamber flocculation, where is 10 minutes From the camera to direct water in a flotation column through a throttling device is introduced pre-saturated air in the saturator (pressure vessel) recirculation (tap) water in a ratio of 1:4 by volume of water to be purified, i.e., 3,8 DM3. The flotation time equal to the time of clarification of the liquid by moving in the foam layer Smagulova suspension is 10 minutes

The clarified water enters the sand filter, loaded quartz sand layer 800 mm and the size of grains of 0.95 mm, the filtering rate is 7 m/h, the filtrate is sent to the contact tank water ozonation dose of ozone 3,30 mg/DM3within 10 minutes ozone Treated water is supplied to the sorption filters, granular activated carbon. The filtering rate of 6 m/h at the load height of 2 m and an average particle size of coal particles of 1.5 - 2.0 mm

Purified carbon filters water is subjected to disinfection with chlorine is obtained drinking water is characterized by the following indicators (table. 1, example 4): COD = 17,0 MgO2/DM3, (G+f) = 31,3 mg/DM3, chroma 6othe turbidity of 0.14 mg/DM3(A+K) = 13 mg/DM3the chloroform of 26.5 g/DM3, aluminum 0.08 mg/DM3. These figures indicate a high quality of drinking water, while some of them exceed the requirements of GOST and MAC.

Thus, according to GOST drinking Water" 3351-74 color is the 20oand the turbidity of 1.5 mg/DM3(example 6oand 0.14 mg/DM3respectively.

According to the requirement of "who Guidelines on quality control of drinking water 1977 - 1978, the residual aluminium concentration should not exceed 0.2 mg/DM3(in the example, 0.08 mg/DM3); and, as mentioned previously, according to the requirement above. MPC for chloroform is 60 g/DM3(in the example of 26.5 g/DM3), it should be emphasized that the quality of drinking water obtained by the described example, far exceeds the quality of drinking water obtained by a known method, primarily on indicators of secondary pollution: the content of chloroform is 163 mg/DM3that 6 times.

When implementing the proposed mode of chemical treatment of the coagulation time and the AZ less than by a known method.

Analogously to example implementations of the method have been carried out experiments on the production of drinking water from water R. Dnieper composition 1 in the processing of oxidants in the claimed range of ratios, and beyond, using as a flotation reagent coagulants different nature in quantities that are in the claimed range of doses and beyond. The data presented in table 1.

As coagulant use aluminum sulfate - Al2(SO4)3(GOST 3758-75), technical alumina - TG containing from 51.3 58,12% Al2(SO4)3(GOST 12966-85), hydroxochloride aluminum (passport No. 31), containing Al2(OH)5Cl 9.1 per cent.

It is established that the claimed ratio of oxidants ozone:ozone:chlorine, conducting chemical treatment of water using pressure flotation using coagulant as a flotation reagent, and the claimed dose of flotation reagent selected from the conditions that provide the necessary depth of oxidation of organic contaminants to compounds effectively removed in the processes of coagulation, flotation and filtration, as well as the almost complete prevention education HOS in the purified water with the minimum content of the compared the O3:O3=1:4,5, i.e., when high-dose of ozone in the second stage, leads to the decrease of the degree of purification from the original organic compounds (concentration (G+f) reaches 41,2 mg/DM3), and secondary pollution of drinking water concentration (a+C) amounts to 34.5 mg/DM3and chloroform of 42.3 g/DM3that exceeds their content in the source water in 3 and 21 times, respectively (table 1, example 15).

Beyond the ratio of O3: O3= 1:0,50 that meets the conditions of the oxidation at low dose of ozone in the second stage, leads to a sharp decrease of the effect of treatment from organic substances concentration (G+f) is 73,7 mg/DM3COD 31 IHO2/DM3. Indicators of treated water is lower compared to the prototype (table 1, examples 16 and 21).

A lower dose of chlorine in the disinfection process (O3:O3:Cl2=1:2:0,2) leads to the absence of residual chlorine after 30 minutes of contact with water, and therefore, there is provided the microbial safety of water in the distribution network, is a secondary bacterial contamination of drinking water, which is unacceptable (table 1, example 17).

When used in the process of pollution of drinking water the content of (a+C) up to 55 mg/DM3and chloroform - 65 g/DM3(exceeds MPC) (table 1, example 18).

It was established experimentally that the optimal dose of fluoresent - coagulant is 40 to 60 mg/DM3. This dose provides effective removal coagulatory and flatironing organic contaminants, phyto - and zooplankton with a minimum content of residual aluminum in the water.

When the dose of coagulant as below the proposed limit and above, there is a decrease in the effect of water purification that is especially evident when beyond lower doses (chromaticity reaches 22othe turbidity of 1.65 mg/DM3). In both cases, the secondary pollution of drinking water by aluminum, the content of which increases to 0.52 - 0,57 mg/DM3(table 1, examples 19 and 20).

Provide proposed method high quality drinking water is also confirmed by table 2, which reflects the achieved results in water treatment R. Dnieper, characterized by different color, turbidity, COD, humic substances. When using the output water with high turbidity (formulations 2 and 3) preferably in the reagent processing to add naznacite the coy company "Watertec. Inc.", for example, MOF-1906 N-high molecular weight nonionic high-activity; MT-573 with - low-molecular cation; MT-A - high-molecular anion exchange resin.

The advantages of the proposed method to obtain drinking water are shown in tables 1,2. As follows from the presented data, the proposed method provides compared to known to improve the quality of drinking water, which is expressed primarily in preventing secondary contamination of toxic organochlorine compounds, the content of chloroform is a 21.1 - 37,5 mg/DM3that 1.6 - 3 times lower than the MPC, while using known techniques leads to the content of chloroform, equal 163,0 g/DM3that is 2.7 times higher than the MAC. Thus, the secondary pollution HOS decreases in 4 - 8 times.

The cleaning effect of the primary organic compounds also increased the content of (G+f) is 25.1 - of 34.5 mg/DM3that 1.75 - 1.25 times lower than in drinking water obtained by a known method. The proposed method provides a reduction in the duration of the process of obtaining drinking water by accelerating coagulation and sedimentation from 3 to 4 hours up to 20 - 30 min, i.e., 6 - 9 times compared to known what level of 0.2 mg/DM3and below, which confirms the high quality of water.

1. The way to obtain drinking water, including treatment of the source water oxidant is ozone, followed reagent treatment, re-treatment with oxidant is ozone, filtration through active carbon and disinfection of treated water oxidizing agent is chlorine, characterized in that the chemical treatment is carried out in a mode pressure flotation, and as a flotation reagent used coagulant, and the dose of oxidant at each of the stages is chosen from the ratio of ozone : ozone : chlorine, equal 1 : (1 - 4) : (0,3 - 1,0).

2. The method according to p. 1, characterized in that the dose of the flotation reagent is 40 to 60 mg/DM3.

 

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