Non-pressure block-modular non-chemical water treatment plant Crystall-B

Crystall-B is meant to remove high concentrations of iron, manganese, ammonia and suspended solids from groundwater, reduce dissolved gases and toxic impurities as well as disinfect the treated water in accordance with the requirements of SanPiN 10124RB99 and SanPiN 2.1.4.1074- 01.

The technology is based on the method of contact oxidation of iron and manganese by air oxygen in the oxidation chamber (bioreactor) and subsequent filtration. This method provides stable plant operation when treating water of various compositions due to the possibility to remove dissolved gases (carbon dioxide, hydrogen sulfide, methane, etc.) as well as reduce oxidizability, color and ammonia. This is achieved by enhanced aeration and inclusion of the biological component of contact oxidation.    

The plants are developed with the use of modern achievements and advanced technologies in the field of water treatment and made of polymer materials resistant to ultraviolet radiation according to TU RB 390 15 1606. 001 2008, have a hygienic certificate of the Republic of Belarus No. 08 33 2.57350.

It is reasonable to use non-pressure deironing stations at water intake facilities where clean water tanks and the second stage pumping station present as well as at single wells or groups of wells operating directly in connection with a water supply network.

Advantages

  • all body elements and parts of the plant are made of polymer materials and have a guarantee service life of not less than 30 years;
  • construction chamber has a special aeration system and a polymer bed that provide intensive mass-exchanging oxidizing physicochemical and biological processes as well as degassing and aeration of the treated water;
  • self-washing filters with a floating bed do not require tanks for wash water storage and special wash pumps;
  • simple and reliable automation system with a minimum amount of shut-off valves provides washing of filters and operation of well pumps and the second stage pumping station without permanent presence of the maintenance staff;
  • if clean water tanks are lacking, the plant is equipped with a distributing tank and second stage pumps with a frequency-regulated drive providing actual water consumption from the water supply network;
  • long filter-cycle (not less than 48 hours at initial iron concentration of 15 mg/liter), short washing period (about 5 minutes), low water pressure required at the input into the plant (not more than 1.0 kg/cm2) provide plant operation economy;
  • minimum operating costs (no need in permanent presence of the maintenance staff; energy consumption of the plant for own needs is not more than 0.01 kW/m3 of the treated water and meant for automation and dispatching control; wash water volume does not exceed 1.0-1.2% of plant capacity).

The basic elements for station construction are the oxidation chamber (bioreactor) and the filter-modules manufactured according to TU BY 390151606.001-2008. Dimensions, number and packaging of bioreactors and filter-modules are determined by station capacity, source water composition and local conditions (means of transport, dimensions of the existing buildings, high-altitude location of clean water tanks, etc.).

Basic parameters of bioreactors and filter-modules

Bioreactor, filter-module diameter, m

1.0

1.2

1.4

1.6

1.8

2.0

2.4

3.0

Capacity at filtration velocity = 7.5 m/hour, m3/hour

6.0

8.5

11.5

15.0

19.0

23.5

34.0

53.0

The capacity indicated in the table may vary depending on the complexity of water composition. The bioreactor diameter is usually equal to the diameter of the filters. In this case, the ratio of the amount of bioreactors to filters is assumed to be 1:3 or 1:4 depending on water composition. This ratio can vary because of a corresponding change in the diameter of the bioreactor and filters. The height of the bioreactors is up to 7.0 m, the height of the filters is up to 4.5 m.

Constructional design of deironing stations

Bodies and single elements of bioreactors and filter-modules are made of spirally twisted pipes PE according to TU 2248-004-45726757 and sheet polyethylene HDPE according to GOST 16338. Fittings and HDPE pipes are made of HDPE according to TU RB 390151606.003.

The bioreactor is a cylindrical tank 5.0 m high (basic version) at the top of which the degassing-aeration zone of source water is located. In the middle part of the bioreactor there is a special polymer bed in the form of free floating bulk elements with a developed surface (180 m2/m3) for the intensification of mass-exchanging physicochemical and biological oxidation processes of iron, manganese and other compounds. The lower cone-shaped part of the bioreactor provides discharge, densification and accumulation of the excess biofilm and other oxidation products. Depending on the quality of source water, the upper part of the bioreactor can be equipped with a secondary structure (dry cooling tower) for blowing off of dissolved gases and additional aeration of source water. In this case, the bioreactor can be up to 7.0 m high.

The filter-module is a self-washing filter with a floating bed in the form of expanded polystyrene of various sizes. Water filtration is carried out from the bottom to the top. In the lower part of the filter there is a system for source water supply and uniform wash water withdrawal. In the middle part there is a floating filter bed 1.0-1.2 m high that is held by the drainage system of a special design. In the upper part of the filter (above-filter space) there is a wash water reserve that is used for periodic washing of filters.

In order to reduce the volume of the above-filter space, which must be not less than the volume of the water required for washing of one filter, the upper part of several filters is combined into a total volume of the wash water reserve. The height of the filter-module depends mainly on the high-altitude water flow pattern at water treatment facilities and should be sufficient for the unhindered flow of the treated water into the clean water tank under hydrostatic pressure. For this purpose, the calculated water level mark in the filter-module must be higher than the mark of water outflow in the clean water tank by the pressure head loss in the utilities and the free outflow, and be determined on a calculated basis. The filter is equipped with a device for the regulation of water supply to the filter and valves with a pneumatic drive for the automation of the washing process.

Basic technological scheme and operation principle of the water treatment plant

Source water from the wells is supplied to the upper part of the bioreactor where intensive degassing and aeration is provided by special devices; as a result, dissolved gases (carbon dioxide, hydrogen sulfide, methane and others) are removed from the water and almost complete saturation with air oxygen occurs. In this case, pH and oxidation-reduction potential (Eh) increase substantially what increases the rate of subsequent oxidation processes.

In the central part of the bioreactor, on the extended bed surface there is a biofilm consisting of oxidized forms of iron, manganese and iron and manganese-oxidizing bacteria. As a result of complex catalytic physicochemical and biological processes in the bioreactor, the basic mass of ferrous iron is oxidized and removed by at least 50-70% in the form of excess biofilms and other oxidized forms; at the same time manganese pre-oxidation occurs. This reduces the load on the filter, increases cycle duration between regeneration periods and significantly reduces wash water flow rate. The lower cone-shaped part of the bioreactor provides discharge, densification and accumulation of the excess biofilm and other oxidation products. The generated sludge is characterized by high concentration, large flakes; it can be well densified and dewatered due to biofloaculation processes and formation of crystalline forms of iron oxyhydroxides. The sludge from the bioreactor is removed periodically (2-3 times per month) by a sludge pipe.

The pre-treated water from the bioreactor enters (through the distributing gears) the lower part of the floating bed filters. By water filtration through the bed, the microflakes of the oxidized iron forms carried out from the bioreactor are retained in the bed; full oxidation and removal of residual concentrations of dissolved iron and full oxidation of manganese also occur here. Due to intensive biological processes, oxidized iron and manganese are retained in a more compact form what increases dirt-holding capacity of the filter by several times and reduces wash water flow rate.

As the pore space of the filter bed is clogged, its hydraulic resistance increases. When the maximum head loss in the filter is reached, it is washed by opening an automatic shutter with a pneumatic drive on the line of wash water discharge. At the same time, the water from the block of above-filter spaces of several filters passes through the bed top-down with a certain intensity (on average 12 l/s m2), expands it transforming into a fluidized state and provides intensive hydromechanical removal of the retained contaminants from the pore space and from the granule surface of the filter material.

The frequency of filter washing depends on the content of contaminants in source water and is set during the commissioning works. Usually it is from 2 to 5 days and is finally determined during the commissioning. The duration of washing does not exceed 4-5 minutes.

To keep a constant water volume in the above-filter space, the plant is equipped with a transferring column mounted on the elbow bend for the treated water discharge to the clean water tank.

For informative commissioning, monitoring of processes during operation and automation, the station is equipped with samplers and sensors at each stage and for each equipment item.

Taking into consideration continual improvement of technological and design solutions, the supplier retains the right to make changes that do not worsen technical and economic performance of the supplied products. Technological scheme development and equipment selection are performed for each single facility by the specialists of UP Polymerconstruction on the basis of the completed data sheet and are provided to the customer or the project organization in the shortest possible time.
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