HK1021171B - Method and device for the treatment of surface water with a high algae content - Google Patents

Description

The invention relates to a process and device for the treatment of water for the production of drinking water from raw water.

Err1:Expecting ',' delimiter: line 1 column 221 (char 220)

Err1:Expecting ',' delimiter: line 1 column 214 (char 213)

Err1:Expecting ',' delimiter: line 1 column 113 (char 112)

In particular, the treatment of highly polluted seawater from shallow lakes such as the Balaton presents particular problems: such a water treatment process must ensure that blue algae and covalent algae are separated and removed from the highly polluted raw water and that turbid and organic substances are removed or reduced to such an extent that the water meets the EU drinking water standard (and the local Hungarian drinking water standard), with an alkalinity of about 10 million algae per litre (especially algal blooms) with by-products, high levels of organic matter and strong alkalinity and poor taste and taste, so that the water is almost never treated with alkaline water (although a standard of purity of about 10000 tons per litre can be found in almost all parts of the country, and almost never with the Algarve water treatment system, although the current standards for the treatment of alkaline water are almost unchanged).

The following steps are normally included in the management of Balaton water treatment plants: 1. pre-oxidation with Cl2 or KMnO4 or (even in combination) 2. flocculation stage with suspended filter 3. sand filter stage or other structure, but not double layer filter 4. activated carbon filter (present in the water plant Balatonfonyod; missing in the water plant Balatonsplake) 5. disinfection with Cl2.

However, as mentioned above, these current treatment steps do not allow the production of water that meets local Hungarian norms or the EU's higher drinking water standard.The current flocculation is not sufficiently effective against algae.Although it has been proposed to use micro-sips, this would only result in a small retention of about 50% for larger covae, whereas for the much smaller blue algae the micro-sips would be completely useless.

It was therefore thought that filtration was generally inadequate for the small blue algae, so that chlorine, chlorine dioxide and KMnO4 were always used in the pre-oxidation of the raw Balaton water.

In the current treatment methods for Balaton water, flocculation by addition of Al2SO4 is common, mainly between 30 and 40 g/m3 and in high algal density, e.g. during algal bloom, between 80 and 100 g/m3. Ca precipitation is also observed as a result of the lack of CO2 in Balaton water due to the high consumption of carbon dioxide by the algae growing in Balaton.

The total concentration of organic carbon can be measured by means of the so-called DOC value (= dissolved organic carbon) and the COD value (= chemical oxygen demand, known in Hungary as KOI value).

The present invention is therefore intended to demonstrate a water treatment process of the type described at the outset by which raw water from rivers, lakes, dams, etc., which is heavily contaminated with microorganisms, in particular zoo plankton, phytoplankton and algae, can be efficiently and as cheaply as possible converted into drinking water in accordance with the standards by making the most of existing treatment facilities.

According to the invention, this task is solved by a water treatment process for the production of drinking water from raw water with the following steps: (a) Immobilization and/or killing of microorganisms present in the raw water, in particular bacteria, viruses and algae, and oxidation of organic matter in the water; (b) 1. Flushing of substances in the water to be treated by adding at least one flocculant; (c) 1. Filtration of the flocculated water to reduce the content of the killed microorganisms and to reduce DOC and subtropical carbon; (d) 2. Flushing by adding a flocculant; (e) 2. Filtration of the flocculated water to further reduce the amount of organic matter and/or hydrogen and water content; (iv) Pre-filtration of the remaining organic carbon in the water treated with a filter.

The method of the invention, first tested for the treatment of Balaton water in a pilot plant, also allows the treatment of raw water heavily contaminated with microorganisms into pure drinking water. In view of the increasing contamination of inland waters, the possible removal of algae and the reduction of DOC values and turbidity to meet legal drinking water standards in pure water is of particular importance. In water treatment, the cost of the process is also important, which is considerably lower than in the invention method compared to the treatment methods currently used. Another advantage of the invention process is that drinking water is obtained with simple means, in particular by not using iron in large quantities and by not using the existing equipment.

The method of the invention is also advantageous in that it significantly improves the odour, colour and taste of the water, eliminates biological growth in the product water and also removes traces of phenols.

In addition to killing and immobilizing bacteria, viruses and algae, ozonation also causes oxidation of organic substances, pesticides, herbicides, phenols, etc. and oxidation of inorganic substances. Among other things, iron and manganese precipitation also takes place. Particularly advantageous in this variant of the process is the flocculation effect of ozone on certain water solvents. A part of the organic substances in the water is greatly reduced by ozone treatment due to decomposition and microflocculation. Oxidation is achieved by carbon dioxide.

Alternatively or in addition to ozonation, H2O2 can be added to the raw water in step (a), further enhancing the positive effects of ozonation described above and killing most of the microorganisms present in the raw water.

A further improvement is achieved by further immobilization of the microorganisms in step (a) by irradiation of the raw water with ultraviolet light.

Preferably, in step (b), one or more flocculants are added to the water to be treated in a quantity of approximately 1/2 to 1 1/2 g/m3.

The flocculant is preferably FeCl3.

At the same time, in step (b), the pH of the water to be treated can be regulated, in particular by adding hydrochloric acid or sulphuric acid to reduce the often too high pH, thus avoiding precipitation of Ca from the water to be treated.

The first step (c) of the filtration process preferably involves a filter life of more than one day, after which the filter used for the first step (a) is cleaned to remove the large amount of microorganisms killed from the water and to reduce DOC and water mist.

The filter or filters used for the first filtration are preferably cleaned by rinsing with a high speed water stream.

The second flocculation in step (d) is preferably followed by approximately twice the amount of flocculant added as in step (b), preferably between 1,5 and 2,5 g/m3.

Addition of polyaluminium chloride to the water to be treated is also advantageous in step (d).

The second filtration in step (e) is preferably carried out in a two-layer filter system, which operates as a room filter with a filter speed of between 5 and 10 m/h.

The material in the double layer filter is loosened, in particular before the filter is started, after periods of standstill by short-term air flow, the air volume being dosed in such a way as to maintain the material separation of the double layer filter structure.

The first filtration in step (c) can be achieved with a filter runtime of approximately 48 to 72 hours despite high raw water load, as the fine filter is significantly relieved by the coarse filter.

The remaining organic substances present in the water are oxidised in step (f) by adding ozone or peroxide or a combination of both to the water to be treated.

Preferably the amount of ozone added is between about 1/3 and 1 g/m3, which further breaks down the remaining organic matter into easily biodegradable substances.

In particular, in step (g), the water to be treated is filtered with a biologically adsorbent charcoal filter, which has a bacterial population to further remove organic residues from the water. In general, inorganic compounds such as iron or manganese are removed as far as possible from the treated water during step (c) and step (e) during step 2 and DOC levels and water vapours are reduced to close to the final values. The oxidative post-treatment of the water in step (f) is then achieved in step (g) in the biologically adsorbent charcoal filtration process, with a further reduction of the organic residues to 1-2 mg/Wl of DOC.

It is important that during the oxidation in step (f) the amount of oxidizing agent is released into the treated water in such an optimized manner that the biological activity of the bacterial population in the downward activated carbon filter is not hindered and the organically decomposed substances in the water are largely absorbed by the activated carbon.

In another preferred method, the filters used in steps (e) and (g) are rinsed with air and/or water from time to time as required, while the filters used in step 1 (c) are rinsed with water only if they are designed as floating grain filters.

In a particularly preferred process variant, a partial amount of product water obtained from step (g) is flushed back, diverting and returning the purified water needed for flushing back to allow for flushing back with clean, germ-free water.

The main quantity of product water obtained from step (g) is discharged into a pure water tank, preferably with a small amount of chlorine or chlorine dioxide added before discharge to ensure that the supply system is in good condition and that no problems with the formation of halophores or re-growth of product water are encountered.

In addition to the above method, the present invention also includes a water treatment plant for the production of drinking water from raw water with a pre-treatment stage in which the raw water to be treated can be introduced to immobilize and/or kill the microorganisms contained in it, in particular bacteria, viruses and algae, and to oxidize organic matter in the water, with a downstream 1. flocculation stage for the flocculation of substances present in the water to be treated by the addition of a flocculant, with a downstream 1. filtration stage for the reduction of the content of dissolved organic microorganisms and for the reduction of the level of dissolved organic carbon (DOC) and the oxidation of organic matter in the water, 1. flocculation stage for the separation of the residual substances in the water to be treated by the addition of a flocculant, with a downstream 1. filtration stage for the reduction of the content of dissolved organic matter and for the reduction of the level of dissolved organic carbon (DOC) and 2. dissolved carbon, 1. flocculation stage for the separation of the water after treatment with a filter, 2. flocculation stage for the separation of the residual substances in the water after treatment with a filter, 2. flocculation stage for the separation of the water from the dissolved organic matter in the water, with a filter filter filter.

Although the individual steps of the water treatment plant of the invention and the individual steps of the procedure described above are known in each case, it is only the combination of the individual steps in the order described above that leads to the positive effects of the invention in the sense of a solution to the above-mentioned problem.

In a particularly preferred embodiment of the water treatment plant of the invention, the pre-treatment stage includes a device for ozonation of the water to be treated.

Alternatively or additionally, the pre-treatment stage may also have a device for adding H2O2 to the water to be treated.

Further training is also useful, in which the pre-treatment stage includes a device for irradiating the water to be treated with ultraviolet light, which can at least immobilize the proportion of microorganisms not caught by oxidation, prevent further multiplication and then in further stages finally kill and filter out of the water to be treated.

Particularly preferred are embodiments of the water treatment plant of the invention where the first filter stage includes a floating bed filter and/or an upstream filter and/or a floating grain filter and/or a filter filled with sand and/or hydroanthracite H.

In particular, when sand filters are used, a sand grain of 0,35 to 0,5 mm is preferred.

The second stage of filtration is preferably a two-layer system.

In the case of a further development of this embodiment, the double layer filter system shall have a storage space of at least 2 m or more which can be used for flocculation.

Another advantage is that the two-layer filter system has a layer of sand, preferably quartz sand, with a grain of 0.35 to 0.5 mm or 0.4 to 0.6 mm and a layer of hydroanthracite H above it with a grain of 1.4 to 2.5 mm. This further reduces the DOC (or the corresponding KOI/COD) values in the treated water.

The sand layer in the two-layer filter will generally be 3/4 to 1 1/4 m high, preferably 0.8 to 1.2 m, and the hydroanthracite H layer will be 1 to 1 1/2 m high.

In the case of preferred training, the two-layer filter system has a special nozzle floor, on which a support layer of coarser grain is stored, which in turn is superimposed by a layer of fine grain.

In other preferred embodiments of the water treatment plants of the invention, the second flocculation stage and/or the second filter stage is a basin for intermediate storage of the treated water before being passed on to the next treatment stage, into which the water from the two-layer filter described above can be passed on to the filter floor via special filter nozzles. The water passed on from this stage to the treatment stage has an equilibrium pH, a very low turbidity and DOC values, which already reach the values of the waste water discharged to the water supply networks of the previous ballast water plants.

In a preferred embodiment of the water treatment plant of the invention, the oxidation stage, which is downstream from the second filtration stage, includes a device for ozonation of the water to be treated.

The charcoal filter stage in the water treatment plant of the invention preferably includes, as described above, a biologically adsorbent activated charcoal filter, which has a bacterial population for further degradation of organic substances from the treated water. The activated charcoal consists of tiny graphite crystals with an immense cavity system of molecular dimension. This results in an extremely large internal surface to which molecules of all kinds can be attached or absorbed by physical attractive forces. The charcoal is also adsorbed to remove the catalytic residue from the treated water.

Preferably the activated carbon filter contains extruded carbon particles with a diameter of 3/4 to 1 mm, preferably ≤ 0,9 mm.

In preferred embodiments, the granulated activated carbon is based on organic raw material, in particular peat, lignite or coal.

In any case, the granulated activated carbon should be suitable for reactivation, in particular thermal reactivation up to and including 900 °C, and be of high purity, in particular with an ash content ≤ 5 ppm.

The activated carbon layer should have a layer height of about 1 3/4 to 2 1/2 m and be operated at a filter speed of between 5 and 10 m/h.

As described above, the amount of oxidizing agents (especially ozone) added to the treated water in the oxidation stage must be optimized so as not to impede the biological activity of the bacterial population in the activated carbon stage.

A hydroanthracite H layer may be placed below the activated carbon layer, the grain of the hydroanthracite H layer should be between 0.6 and 1.6 mm and the height of the layer should be optimized according to the requirements of the product water.

After the charcoal filter stage, the purified water obtained fully complies with the legal limit values for inorganic substances, has a DOC of 1,0 to 2,0 mg/l and a water turbidity of 0,2 to 0,5 NTU and the observed algal count is also below the prescribed limit values.

Finally, a further embodiment of the water treatment plant of the invention is preferable, in which the grain-coal filter stage is connected to a sink in which a partial amount of the treated water flowing from the grain-coal filter stage can be introduced for the purpose of flushing back filters.

The first flocculation stage and the first filter stage can also be bypassed if the raw water to be treated is less affected by algae and organic matter and pH control is performed in the second flocculation stage to optimise the process.

Further advantages of the invention are derived from the description and drawing. Similarly, the features mentioned above and those listed further on may be used individually or in combination with one or more of them in accordance with the invention. The embodiments shown and described are not to be understood as a final list but are rather exemplary in describing the invention.

The invention is shown in the drawing and is explained in more detail by an example of the work. Figure 1a first embodiment of the water treatment plant of the invention; and Figure 2a further embodiment with a suspended filter system as the first filter stage.

The invention proposes a process guide for the treatment of water from highly contaminated raw water, such as that obtained from microbial and algal contaminated shallow water, with the following steps: (a) Immobilization and/or killing of microorganisms present in the raw water, in particular bacteria, viruses and algae, and oxidation of organic matter in the water; (b) 1. Flushing of substances in the water to be treated by adding at least one flocculant; (c) 1. Filtration of the flocculated water to reduce the content of the killed microorganisms and to reduce DOC and subtropical carbon; (d) 2. Flushing by adding a flocculant; (e) 2. Filtration of the flocculated water to further reduce the amount of organic matter and/or hydrogen and water content; (iv) Pre-filtration of the remaining organic carbon in the water treated with a filter.

This process was first tested in a pilot plant with Balaton water. The plant was optimized to meet and even exceed the local limits for drinking water with the product water produced from the plant. In particular, the structure of the filtration steps, material and grain composition, process speeds and contact times in the treatment stages, and the amount of flocculant and oxidizing agent added at raw water temperatures between 3°C and 24°C were optimized. The process is suitable not only for the treatment of Balaton water, but also for raw water from rivers, lakes and valleys and other micro-organism-rich bodies of fresh water. The high organic weight of particularly small leaves, which can be extracted by other means, can be significantly reduced.

The oxidation process simultaneously produces micro-flocculation with the organic substance, which is then removed from the product water by means of the first flocculation, which is then carried out in a very specific way in the first filtration, and which reaches normal values in the second flocculation and the second filtration in the turbidity.

Even at particularly high stresses on the raw water - in Balaton water several million algae per litre are observed during the algal bloom period - the introduction of the first filtration ensures a decisive filtration of all the water components.

The oxidation in step (f) is used to further break down the remaining organic substance in the product water, so that better adsorption can be achieved in the following biologically adsorbent charcoal filter. The charging times of the charcoal filter at the above process speeds and contact times increase accordingly.

The limits for pure water in the Balaton range can be fully satisfied by the method of the invention, in particular a proportion of Fe < 0,2 mg/l, Mn < 0,05 mg/l, O3 < 0,05 mg/l, dead microorganisms = 0,01 · 106/l, DOC values of 1 to 2 mg/l and turbidity values of 0,2 to 0,5 NTU.

Figure 1 illustrates a typical embodiment of the water treatment plant of the invention. First, water from a water body 1, in particular from a shallow water heavily contaminated with microorganisms, is taken as raw water by means of a pump 2 and fed to a pre-treatment stage 3, in which a large part of the microorganisms contained in the raw water, in particular bacteria, viruses and algae, are immobilized and killed, and in which an oxidation of the organic substances contained in the water takes place. Preferably, the pre-treatment stage 3 includes ozonation, but alternatively or in combination, peroxidation of the raw water and possibly also ultraviolet irradiation.

The pre-treatment step 3 is followed by a 1st flocculation step 4 in which flocculant, preferably FeCl3, is added to the water.

The water is then fed to a first filter stage 5 where, in the example shown, a large part of the flocculated particles, in particular the killed micro-organisms, are removed from the water in the upstream.

From the first filter stage 5 the treated water is passed to a second flocculation stage 6 where flocculant, including polyaluminium chloride if necessary, is added to the water.

This is followed by a second filter stage 7, preferably a two-layer system, which is used to further reduce organic and/or inorganic water content and to reduce water mist again.

The treated water is then fed into an intermediate tank 8 for intermediate storage before being passed to the next treatment stage. By means of a pump 9 the water from the intermediate tank 8 is fed into an oxidation stage 10 operating downstream. Alternatively, however, the treated water can also be fed directly into the oxidation stage 10 from the second filter stage 7.

Preferably, the oxidation state 10 includes a device for ozonation of the water to be treated, but additional or alternative peroxide may be added.

The water from the oxidation stage 10 is then introduced into a grain-coal filter stage 11 which is also run in the drain.

The grain carbon filter stage 11 includes a biologically adsorbent activated carbon filter which has a bacterial population to further break down organic substances from the water; in addition, the bottom layer in the grain carbon filter stage 11 may also be formed from a hydroanthracitic H layer with a coarseness slightly greater than the carbon particles in the activated carbon layer to minimise the release of extruded activated carbon particles.

In the example shown, a sub-stream of product water from the grain-coal filter stage 11 is diverted to a flushing basin 12 so that the filter can be flushed back into the plant with clean, germ-free water. A small amount of disinfectant, particularly chlorine or chlorine dioxide, can be added to the main stream of product water at a disinfection station 13 to prevent re-infection. The treated water is then fed into a pure water basin 14 from which it can be drawn for supply to the water supply network.

The water treatment plant of the invention shown in Figure 2 differs from the water treatment plant shown in Figure 1 by using a 5' floating filter system as the first filter stage.

Claims (10)

1. Method of treating water for producing drinking water from untreated water comprising the following steps:

   (a) immobilization and/or destruction of microorganisms present in the untreated water, in particular, bacteria, viruses and algae, and oxidation of organic substances in water;

   (b) 1. flocculation of substances contained in the water to be treated through addition of at least one flocculant;

   (c) 1. filtration of the flocculated water for reducing the content of destroyed microorganisms and for reducing the DOC values (DOC = dissolved organic carbon) and the clouding of water;

   (d) 2. flocculation through adding a flocculant;

   (e) 2. filtration of the flocculated water for further reducing the organic and/or anorganic water content substances and clouding of water;

   (f) oxidation of the remaining organic substances present in the water;

   (g) filtration of the treated water through a grained carbon filter (11).
2. Method according to claim 1, characterized in that in step (b), the pH value of the water to be treated is regulated, in particular in that hydrochloric acid or sulphuric acid is added.
3. Method according to any one of the preceding claims, characterized in that in step (c ) the first filtration is carried out with a filter running time of ≥ 24h, that subsequently the filter used for the first filtration is cleaned and cleaning of the filter is carried out through a strong water flow.
4. Method according to any one of the preceding claims, characterized in that filtration of the treated water is effected in step (g) with a biologically adsorptively acting grained carbon filter (11) which has a bacteria population for further reduction of organic substances in the water and that in step (f) only a minimum amount of oxidant is supplied to the water to be treated such that the biological activity of the bacteria population is not impaired in the subsequent grained carbon filter (11).
5. Method according to any one of the preceding claims, characterized in that the filters used in steps (e) and (g) are backrinsed with air and/or water from time to time and that backrinsing is effected with part of the water obtained in step (g).
6. Water treatment plant for producing drinking water from untreated water comprising a pre-treatment step (3) into which the untreated water to be treated can be introduced for comprehensive immobilisation and/or destruction of the microorganisms contained therein, in particular bacteria, viruses and algae, and for oxidation of organic substances in the water, with a subsequent first flocculation step (4) for flocculating substances contained in the water to be treated through addition of a flocculant, comprising a subsequent first filtering step (5;5') for reducing the content of destroyed microorganisms and for reducing the DOC value (DOC = dissolved organic carbon) and the clouding of water, having a subsequent second flocculation step (6) spatially separated from the first flocculation step (4), with a subsequent second filtering step (7) spatially separated from the first filtering step (5;5') for filtering out substances flocculated in the second flocculation step (6) from the water to be treated, having a subsequent oxidation step (10) for disintegrating the remaining organic substances in the treated water into substances which can be biologically decomposed and comprising a subsequent grained carbon filtering step (11) for further filtration of the treated water.
7. Water treatment system according to claim 6, characterized in that the first filtering step (5; 5') comprises a floating bed filter (5') and/or an up-current filter (5) and/or a floating grained filter and/or a filter filled with sand and/or hydroanthrazite-H.
8. Water treatment plant according to any one of the claims 6 or 7, characterized in that the second filtering step (7) comprises a two-layer filtering plant.
9. Water treatment plant according to any one of the claims 6 through 8, characterized in that the second flocculation step (6) and/or the second filtering step (7) is followed by a basin (8) for preliminary storage of the treated water before passing it on to the next treatment step.
10. Water treatment system according to any one of the claims 6 through 9, characterized in that the grained carbon filtering step (11) is followed by a rinsing water basin (12) into which part of the amount of the treated water discharged from the grained carbon filtering step (11) can be introduced for backrinsing the filters.