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The term hardness refers to the quantity of dissolved calcium and magnesium in water. These minerals, which come primarily from limestone type rock formations, are found to some degree in almost all natural waters. Calcium and magnesium cause problems for two principal reasons: When the water is warmed, they precipitate out of solution and form a hard, rock-like scale. This scale accelerates corrosion, restricts flow, and reduces heat transfer in water heaters and boilers. When they combine with soap, they react to form a curd, which interferes with cleaning, dries out skin, and leaves deposits on plumbing and clothes (bathtub ring; ring around the collar). The minerals in hard water gradually settle out forming a hard scale. Scale centimeters thick can build up over time in hard water areas. Scale build up will eventually clog pipe, and can decrease the life of toilet flushing units by 70 percent and water faucets by 40 percent according to a report published by the American Water Works Association (AWWA). Hardness scale can also shorten life of washing equipment, dishwashers, and clothes washers by as much as 30 percent according to the AWWA report. Hardness is measured in parts per million (or the equivalent mg/L) or in grains per gallon (gpg). Note: if the water analysis is given in ppm as CaCO3 then 1 gpg = 17.1 ppm. There is no established limit for the acceptable level of hardness in water, but it is generally considered to become problematic at around 3 gpg. Levels of hardness are referred to as follows:
HydroFLOW prevents the formation of hard scale due to increases of temperature and pressure change, under all normal operating conditions. Users are advised to contact Hydropath Technical Support if they suspect that conditions are unusual. Scale Removal Old scale is normally broken down. The time taken depends on the volume of water, the flow of water to remove the excess scale crystals, the porosity of the old scale and variations in the temperature and the pressure of the water. In most cases the process is fairly rapid, and up to 95% or more of old scale is broken down and treated within the first three months. Hard scale may be slow to break down where there is low water volume and little variation of temperature, flow, hardness and pressure. In such cases HydroFLOW is best fitted from new or after chemical cleaning. If HydroFLOW is applied to a heavily-scaled system, where scale may have formed on the inside of a narrow pipe or plate heat exchanger there is a small risk of blockage due to dislodged pieces of scale. The user is advised to have a system cleanse or to install suitable coarse filters prior to fitting HydroFLOW. The HydroFLOW signal is effective both up and down stream and can cause a large quantity of scale to be broken down. In most cases the only effect may be that users see the crystals as they emerge from open taps. This does not always happen and stops within three months. There will be no adverse effect in a closed recirculating system unless there is significant evaporation or there has previously been some significant leakage. Corrosion The application of HydroFLOW cannot itself cause corrosion or leaks. Scale is a direct cause of corrosion and its removal may reveal leaks. Rust coatings in mild steel pipework are altered, resulting in a hard black surface deposit, magnetite, rather than normal rust and further corrosion is prevented. This effect is due to an interference with the electro-chemical reaction needed for corrosion to take effect. Maintenance HydroFLOW uses solid state circuitry and does not require maintenance. Its signal cannot create films which would reduce performance. There is a red light which is powered directly by the generated signal and is a positive indication of correct operation. If the operation of the device is critical, users should monitor this light as part of a planned maintenance procedure. Residual Effect Once water has left the plumbing system or left the protection zone, it can no longer be subjected to the HydroFLOW conditioning field. 30 minutes may be taken as a conservative guide to the time that the water retains its full scale prevention ability. Soft Scale In systems with no turbulence the crystals can settle. This can occur in commercial kettles, coffee machine reservoirs, large clarifiers and cooling tower pools. The resulting soft scale is removed during maintenance or using filters.Recirculating Systems with Evaporation Where a recirculating system involves evaporation, e.g. cooling towers or humidifiers, the suspended crystals must be removed using filtration (50 microns) or blow down to avoid concentration. On initial application existing scale will be broken down leading to an excess of precipitate which users must address. The easiest approach is to increase blow down. A suitable filter with automatic back wash will also control the problem and will reduce water costs. PH can be controlled using sulphuric acid to reduce the rate of precipitation. Plate Heat Exchangers When using HydroFLOW to protect plate heat exchangers, existing scale in the pipes upstream of the device will be broken down. This will lead to excess precipitate in the heat exchangers which can continue to cause scale for the first few weeks. If the plate heat exchanger is heated using steam, it is advised that the hot steam supply is connected to the same side as the water return. The heat exchanger will give increased performance through the avoidance of boiling. |
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Membrane UF capillary (0.9 mm)Ultra filtration reliably removes particles, bacteria, germs and viruses out of the water – independent from the feed water quality! This means that also highly polluted water can be securely purified and all pathogenic ingredients will be excluded in order to be able to use the water as pure drinking water. In order to be able to guarantee a complete elimination of any harmful substances, disruptions and leakages within the membrane must be totally avoided. In addition to a high chemical and biological resistance, the membrane must additionally be of a high mechanical stability so that it will also sustain high-pressure water hammers which may be caused by valve circuits. The risk of water hammers is especially high in large water purification plants due to the huge water quantities that are manouvered. The minimization of membrane rupture can be obtained by using the UF membrane. Completely new is the arrangement of 7 capillaries in one fiber in contrast to the conventional single bore membrane. Whole-arrangement enables a tremendous stability due to the foamy support structure that is located in between the capillaries (cf. figure 1, right side). The inner layer of the seven capillaries represents the very thin active filtration surface. The foamy support structure in between the capillaries shows a permeabilty that is approx. 1000 times higher than the filtration surface so that an equal distribution throughout the whole cross section of the fiber can be guaranteed. An ultrafiltration membrane generally has a molecular weight cutoff (MWCO) of ca. 100.000 g/mol which in an average correlates to a pore size of 10 nm. Despite the very low pore size, the permeabilty of the membrane in very clean water is about 700 l/m²/h. An additional advantage of the UF membrane is the high resistance against cleaning chemicals, such as acids, bases or oxidation agents, e.g. hydrogen peroxide and active Chlorine. Characteristics and advantages of in-out-filtration Filtration takes place in the so called in-out-mode. This procedure assures that an ongoing and equal overflow on the side of the membrane on which a layer cake is formed, is generated to make the cleaning of the membrane more efficient. Furthermore the water volume on the side of the brackish water can be decreased to a minimum. E.g. the volume of waste water of a UF module with a membrane surface of 45 m² only amounts to ca. 10 liter. Thereby, the backwash can be carried out in relatively short periods of time with only little filtrates to be used; and furthermore the layer cake will be loosened and removed completely. In contrast to the in-out-filtration, the very high amount of sludge which incurred in out-in-systems can only be loosened but not removed completely. This leads to a steadily concentration of the sludge water up to 5-20 times, depending on the total recovery. Furthermore, in out-in-systems the membranes are continuously exposed to a high feed concentration while with in-out-filtration such a high feed concentration will only be reached at the end of a filtration cycle (cf. figure 2). In average, the feed concentration of out-in-systems is said to be 3 to 4 times higher compared with the in-out-filtration if using the same raw water. Secondly, out-in-systems have to be put into separated tanks for an intensive and complex chemical cleaning on a regular basis. This procedure has to be carried out in addition to the regular chemical enhanced backwashes. In order to avoid the building of a strong layer cake on the membrane due to the high sludge water concentration, an extra backwash with air has to be carried out. In case the feed water has been flocculated before the membrane filtration, this air backwash may destroy the flocculants. Advantages of the 0.9 mm capillary diameter The capillary diameter of 0.9 mm enables a more flexible operation of the membrane:
Operating the module only in one (top) mode, just the upper collection connector comes in touch with feed water while the lower collection connector always is in touch with backwash water. This helps to avoid that backwash water will be flushed into the module. Characteristics and advantages of singlebore capillaries For raw water types that carry high turbidity or a high amount of larger particles, a treatment using capillaries of a larger diameter is recommended. Additionally, modules with larger capillaries can be operated at a higher cross-flow-speed as the pressure loss throughout the length of the capillary is less. Even at very high flux rates the total pressure loss will be of a minor amount. A UF structure is not needed for this type of capillary as the mechanical stability results from the much thicker wall strength compared to the conventional 0.8 mm single bore capillary. Modules of this membrane type will be mostly used in waste water and sludge water treatment (e.g. in the treatment of backwash water of conventional filters and / or UF plants as well as in the area of swimming pool water treatment). Characterics and advantages of UF Modules In order to guarantee the high performance of the membranes also when they are implemented in the modules and furthermore to enable an efficient cleaning of the membrane during the backwash, only a marginal pressure drop within the membrane bundle on the permeate side of the module is required. Only then it can be guaranteed that each capillary will be charged with the same transmembrane pressure (TMP). This fact is required for carrying out an efficient backwashing that reaches every location within the module. This results to a shortening of the backwashing cycle which concurrently increases the recovery of the total filtration process. The UF module enable an optimized flow distribution due to their specifically module housing.
Fundamentals of water softening Water is a very complex fluid. It retains a little bit of practically everything that it contacts; the air while falling as rain, the earth as it percolates into the ground, the piping as it is transported and all kinds of organic and inorganic matter it may contact in its series of uses. Dissolved minerals in the water that can be either positively or negatively charged with electrons. The positive ions are called cations and the negative ions are called anions. It is these positive cations in the form of calcium, magnesium, iron and manganese that causes the hardness that is associated with water. Removal of these hardness ions via ion exchange is the process used for softening water. The ion exchange process requires a resin tank and brine tank as a simple design requirement. Brine is educed into the mineral tank and washes over the resin in the mineral tank. Since the resin has a salt splitting capability and a cation accepting characteristic, sodium ions of the sodium chloride (brine) solution are attracted to the resin beds. This is called the regeneration process and it will continue until most of the exchange sites have been occupied with the sodium ions As the complex raw water enters the tank, the positive hardness ions exchange on the resin and displace the sodium ions to the service stream. Because calcium and magnesium are positive cations, the resins, being charged with positive sodium ions, will exchange with the calcium and magnesium ions. Calcium and magnesium will now occupy the exchange sites on the resin beds. This process will continue for a length of time until the hardness ions begin to leak out of the bottom of the resin bed. For all practical purposes, the resin is exhausted with calcium and magnesium and has no more sodium available to displace. This is the point where the softener must be regenerated. | |||||
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