On this page, we would like to present water treatment methods applied by Dunatec Ltd. We are ready to give expert advice to our clients in any of these methods below and offer our water treatment equipment for different tasks.
Filtration
Water, depending on its origin may contain contaminants or organic load. There is a range of filtering techniques available to eliminate these. We apply specific filter materials in accordance with the composition of the water. Screening vessels are made of plastic or steel. According to the requirements of our clients the filtering equipment is manufactured as a manually operated or automatic implement.
Iron removal (deironization)
After the oxidation of the ferrous iron in ferric iron insoluble iron hydroxide, Fe(OH)3, is formed, which can be filtered out in a mechanical (natural) way. Then the contaminants so collected in the filter reservoirs are removed by an automatic or hand-steered return flushing.
For a successful iron removal, the following presuppositions must be fulfilled: The pH value of the water to be treated must lie in the neutral area, organic compounds should not exist. For the implementation of the process technology a water analysis is necessary.
The iron removal systems are divided in small filter arrangements for private households and project arrangements used by industry and water supply enterprise up to a capacity range of 1.000 m³/h.
The system produces water with an iron content below the limit for drinking water.
Manganese removal
In the water solved manganese salts are converted into insoluble oxide and then can be filtered out. Then the contaminants so collected in the filter reservoirs are removed by an automatic or hand-steered return flushing.
For a successful manganese removal, the following presuppositions must be fulfilled: The pH value of the water to be treated must lie more than 7.4, organic compounds should not exist. For the implementation of the process technology a water analysis is necessary.
The Manganese removal systems are divided in small filter arrangements for private households and project arrangements used by industry and water supply enterprise up to a capacity range of 1.000 m³/h.
The system produces water with an iron content below the limit for drinking water.
Acid removal
In soft watering with too low pH value, carbon dioxide is present in free aggressive form. In the acid removal filtering, this free carbon dioxide is bound to Calciumcarbonat. Thereby rises the pH value and at the same moment a raised hardness of the water takes place. The acid removal material is used up by the connection of the carbon dioxide and must be refilled from time to time. For the implementation of the process technology a water analysis is necessary. The acid removal systems are divided in small filter arrangements for private households and project arrangements used by industry and water supply enterprise. By the project arrangement, the water is neutralized up to the balance pH value of the calcite saturation and corresponds therefore the TVO.
Activated carbon filtration
Activated carbon (AC) filters are used for taste improvement, the elimination of free chloride and organic compounds in water. The type of the AC filter is to be selected according to the field of application. The disturbing contents materials are adsorbed by the activated carbon filling. If the activated carbon is loaded with the contaminants entirely, the filling must be exchanged. The example named at the top is only a possibility of many. The respective process technology and components are selected by presenting of a water analysis. These arrangements are used from a capacity range of 3m³/h – 100m³/h.
Gravel filtering
To the usual dirt filtration, gravel filter arrangements are applied. The disturbing contents materials are held back in the filter reservoirs are enriched and, finally, are removed by flushing. With a combined air water-flushing, the collected contaminants are rinsed out from the countercurrent and are led into the sewerage system. For the back flushing, we normally use the already filtered water from the rinse water tank. The back flushing can be either manually operated or fully automatically. The filter arrangement is implemented either as a single arrangement or as a double arrangement in a pendulum`s-operation. This way, the system can continuously operate during wash-back. The respective process technology and components are selected by presenting of a water analysis. These arrangements are used from a capacity range of 4m³/h – 1000m³/h.
Multi-layer filtering
Multi-layer filters are used to the usual dirt filtration. They have a special filter layer, by which they have in general a higher dirt admission capacity than pure gravel filter arrangements. Their design and operation is identical to sand filters. These arrangements are used from a capacity range of 4m³/h – 1000m³/h.Physical degassing plants are based on the fact that condensable gases (CO2 and CO2) are water insoluble at temperatures above their boiling temperature. In these cases the boiling temperature of water depends on the pressure.
Partial desalination
The part desalination is a combination of two processes, in which a de-carbonating filter is combined with a softener filter. This procedure finds application with priority at the boiler feed water treatment, if water with high carbonate hardness must be processed. The carbon dioxide formed in the de-carbonating process is lead through the softener filter and separated in the degassing unit along with oxygen.
Carbonate removal (De-carbonation)
De-carbonating equipment is used to decrease the carbonate hardness of water. Such systems are used in the following fields: boiler feed water, cooling water and pre-treatment of water for the food industry. In the process, calcium and magnesium ions bound to hydrogen carbonate are removed with the help of an ionic exchanger in slightly acidic medium. In the meantime, hydrogen carbonate is transformed into water and carbon dioxide. To prevent corrosion, the water should then pass through a degasser to eliminate carbon dioxide. For the continuous supply of de-carbonated water, two parallel switched filters are needed in plastic or rubberized steel execution, which are alternating in the work and regeneration cycle. Water to be treated is driven from top to bottom in the equipment. In the regenerating phase acid is driven in the opposite direction from the bottom of the filter to the top while excess acid is eliminated in the connecting washer. Our carbonate removing equipment comes either in a manually operated or in a fully automated design and can have a one-way or a two-way system. Flow rate can vary in the range of 1.5-100 m3/h.
Membrane technology
The membrane method incorporates processes in which solutions, ions, or particles are separated with the help of a membrane. With conventional methods, the separation limit falls in the range of 1-10 µm. For the separation of all particles smaller than that range, other methods should be used. With the pressure-driven membrane procedures, for the transport of the medium by the membrane, pressure is exerted of the liquid. In practice, four types of membrane methods are differentiated: reverse osmosis, nanofiltration, and ultrafiltration and crossflow microfiltration.
Reverse osmosis
Reverse osmosis equipment is used in many areas: hospitals, clinics, catering facilities, breweries, the printing industry, galvanising plants, carwash facilities, air conditioners and ventilating equipment, heating boilers etc. The method is mostly applied as part of the preparation of potable water through desalination or partial desalination without the addition of chemicals. They come in a wide range of design from compact wall units (50 l/h ... 350 l/h), through compact closet systems (500 l/h ... 1000 l/h) to frame mounted systems (above 100.000 l/h). The attainable permeate-quality, depends therby very strongly on the salt content of the water to be treated. According to the concept of the equipment the remaining conductivity can be lowered to the range of 5-50 µS/cm. Equipment using reverse osmosis consist of a water preparation unit, the actual reverse osmosis system, a permeate container and a pressure increaser unit. The preparatory unit usually contains a filter and a water softener with the purpose of eliminating calcium and magnesium ions that would decrease the life span of the membrane. In certain cases, the use of hardness stabilizers can be considered instead of ion exchange. Other pre-treatment like iron and manganese removal or chloride reduction should be applied in consideration of the quality of water. The reverse osmosis system/equipment itself consist of the following units, independent of its capacity: primary filter, high-pressure pump, pressure pipes with the membrane elements, measurement and control equipment pressure holding system and control panel. In special cases, elimination of dissolved carbon dioxide might be necessary (in hospitals or laboratories for the sterilization of linen or mattresses). This can be effectuated with the addition of caustic soda solution before reverse osmosis. This way, the carbon dioxide is transformed into sodium hydrogen carbonate which is separated by the system.
2-phase reverse osmosis
2-phase reverse osmosis systems are used in areas where the requirements for the quality of the permeate are especially high. This occurs mainly in the pharmaceutical industry, in hospitals, clear steam producing plants and laboratories. In such cases, the “raw” permeate gained after the first reverse osmosis is driven to a second phase, where it is treated again. This way, remaining conductivity of the range of 1 and 5 µS/cm (depending on water quality) can be reached. 2-phase reverse osmosis systems consist of a water preparation unit, two reverse osmosis systems and a permeate container (with sterile degassing). Preparation, here again, consists of filtering and water softening. Instead of ion exchange hardness stabilization may be considered. Iron and manganese removal or chloride reduction might be necessary in function of water quality. The reverse osmosis equipment itself consist of the following units, regardless its capacity: primary filter, high-pressure pump, pressure pipes with the membrane elements, measurement and control equipment pressure holding system and control panel.
Microfiltration (CFM)
Crossflow-Microfiltration (CFM) is a special technique in the field of liquid filtration. Compounds to be separated flow through the membrane tangentially and the permeate /filtered material is conducted away in a right angle. Consequently, the medium to be filtered does not filter through the membranes directly but it flows across the membranes. Driving the medium this way of cleans the membrane and multiplies its life span. Microfiltering membranes separate particles or colloid solved suspensions. The dimensions of their pores are in the range of 0.05-10 µm. The ceramic membrane material is definitely robust with high temperature tolerance and operates between wide limits of pH values.
Ultrafiltration
Ultrafiltration is a method used for the separation of large organic substances (proteins, viruses and bacteria). In contrast with reverse osmosis the system is not suitable for the retention of salts. Membranes have real pores and their filtering ability depends on the design of module geometry the flow conditions between membranes and the components of the water. Like in other membrane processes there are tangential flow conditions to prevent sedimentation. Details >>>
Nanofiltration
An equipment for nanofiltration, like other membrane technology equipment, consist of the following components: primary filter, high-pressure pump, pressure pipes with nanofiltering elements, measurement and control equipment pressure holding system and control panel. Thus, purification systems consist of water pre-treatment, the actual nanofiltering device and a buffer provided with pressure increaser. In general, pre-treatment consists of a filtering phase and water softening. In certain cases water softening can be replaced by hardness stabilizing system adding the necessary chemicals. Other pre-treat processes like iron or manganese removal or chloride removal might be necessary in the knowledge of the quality of the water to be treated. Nanofilters, thanks to their ion selective qualities are widely used in potable water cleaning and desalination. The method also allows for partial desalination.
Sterilization
The objective of sterilization is to neutralize present pathogenic organisms like viruses or bacteria. This objective can be achieved by physical or chemical sterilization processes. Conventionally, these organisms are neutralized and destroyed in the process. Sterilization is the final phase of water purification. In practice it is not possible with exception of very small water systems to kill all micro-biological components contained in it to 100 %. The technological and environmental limits for microbiological components are under statutory regulations and the technologies in use are calibrated to meet these criteria.
Neutralization
An important parameter for the characterization of Water is the pH value. Among them one understands the negatively Briggs logarithm of the hydrogen ion concentration. The pH value of acidic waters is in the range of 1-6 while basic waters have a pH value in the range of 8 to 14. Neutral water is denoted by pH 7. In general industrial waste water is highly acidic or alkaline so before its drainage to the sewers or further treatment must be neutralized. Acidic waters are neutralized with e.g. caustic soda solution while alkaline waters are pre-treated and neutralized with hydrochloric acid or sulphuric acid.
Degassing
Degassing means the elimination of gases (oxygen or carbon dioxide) dissolved in water. These gases cause corrosion in warm or hot water systems or steam boilers.
Thermal pressure degassing
During thermal pressure degassing means the elimination of gases (oxygen or carbon dioxide) dissolved in water at high temperature. In such cases, water is heated with low pressure steam with the help of a steam boiler. The reaction takes place at 106 0C with a pressure of 1.3 bar. This is based on the fact, that water simmers with pressures over the atmospheric pressure at temperatures over 100 °C.
- Filtration
- Deironization
- Manganese removal
- Acid removal
- Activated carbon filtration
- Gravel filtering
- Multi-layer filtering
- Partial desalination
- De-carbonation
- Membrane technology
- Reverse osmosis
- 2-phase reverse osmosis
- Microfiltration
- Ultrafiltration
- Nanofiltration
- Sterilization
- Neutralization
- Degassing
- Thermal pressure degassing
- Sewage watertreatment
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