How to Make Water Treatment?
WATER ARITHMETIC SYSTEMS
Depending on the source of the water and the purpose of use, the removal of all kinds of foreign substances in the water from the water is called water treatment and all equipment used for this purpose is called water treatment systems. Water Treatment is carried out by 3 different methods: physical, chemical and biological.
Physical Treatment; suspended solids such as clay, sediment, sand, which spoil the natural appearance of water and cause turbidity, are separated from water.
Chemical Treatment Process; it is to reduce the ions dissolved in the water to the desired values or to remove them completely from the water.
Biological Treatment Process; neutralization of microorganisms in water through chemical disinfectants or UV Systems (ultraviolet).
FILIATION SYSTEMS
Filtration is also called filtration systems for all the processes of separating suspended solids in the water by filtering them from the water and chemically removing the bad smell and taste created by organic substances in the water and converting the water into its natural state.
The natural state of water is colorless (clear), odorless and tasteless. Water whose appearance is blurred and fragrant is considered dirty water. If the appearance of the water is also colored, it can be considered that there are unwanted organic substances and heavy metals in dissolved form in the water.
Filtration systems are needed to treat all these impurities from water. It is possible to collect classical filtration systems mainly under 3 main headings.
Gravity Filters; They are simple systems used after the sedimentation pool or tank and operate according to the principle of filtering water from a filter bed consisting of various layers of filter minerals through the natural force applied by gravity to water. The aim here is to imitate the filtration that takes place in the natural environment with man-made systems. Gravity filters operate at very low speeds and allow for the large removal of large-grain suspended solids in the water.
Multi-Media Filters; In itself, they are mainly divided into 2 main groups.
Sand (Quartz) Filters; They are specially designed filtration systems based on the principle of filtering suspended solids and removing filtered suspended solids from filter layers by reverse washing (regeneration) by passing water at high pressure and a certain speed from the layers created by stacking sand and gravel particles of different mineral sizes at a certain order and height. In general, these filter layers, which place in a fiber, steel or stainless tank, are called "Multi-Layer (Multi-Media) Sand Filter Systems" and form the first filter unit of all water treatment systems. Its main purpose is to physically filter and separate certain large (>80 μ) suspended solids in the water from the water.
Activated Carbon Filters; Unlike sand filters, its main purpose is; Instead of filtering the suspended solids in the water, they are used to keep the free chlorine and oxidants contained in the water, as well as to remove organic substances and the bad smell and taste they create. They are an integral part of water treatment systems and are usually used before softening systems and Reverse Osmosis.
Green Sand Filters; it is a special and very rare green sand layer for the purpose of keeping iron and manganese, which is dissolved in water and cannot be removed by classical filtration methods. Mechanical filtration capability is moderate and its main purpose is to hold heavy metals dissolved in water.
Cartridge Filters; Gravity and Multi-Media filters are filters used to separate smaller-sized (1-50μ) Suspended Solids from water. The cartridge body can be produced as plastic or steel according to its usage area. Putrex, nylon or steel filters are used as filter material. Putrex filters are designed for single use and need to be replaced with a new one when the filter reaches saturation. Filtration capability is better than nylon and steel cartridge filters. Nylon and steel cartridge filters can be cleaned and used more than once by washing when they are clogged.
SOFTENING SYSTEMS
Systems that separate calcium and magnesium ions, which are dissolved in water and generally referred to as "Water Hardness", from water based on the principle of ion exchange through a catalytic resin are called Softening Systems. It is loaded with resin Sodium (Na) ions in the softening tank. When passing raw water through resin, the calcium (Ca) and magnesium (Mg) contained in the water are replaced by the Sodium (Na) ion on the resin, thus separating the hardness-forming ions from the water. In case of depletion of Sodium (Na) ions on the resin, which is called the saturation of the resin, the resin is washed with a saline solution, releasing the Calcium (Ca) and Magnesium (Mg) ions and loading them again with Sodium (Na) ions. This process is called resin renewal or regeneration. Softening Systems with very low mechanical filtrason capability are fully automatic, depending on the degree of hardness of the water, without the need for the amount of water passing through the resin or human intervention at a time setting. Water Purifiers
Softening systems should be selected according to the following criteria when choosing.
Resin height; In order to achieve optimal efficiency during operation, the tank height and consequent resin height, as well as the swelling rate of the resin during reverse washing, should be calculated very carefully. Otherwise, during reverse washing, the system may experience resin leaks and therefore water hardness cannot be adequately removed. Water Purifier
Determination of the time between two regenerations; The most important factors in determining the regeneration period are the type of resin, the hardness of raw water, the soft water flow to be obtained, the tank diameter and, accordingly, the flow rate of the water that will pass over the resin. According to all these values, the design should be made and the most appropriate softening system should be selected. In general applications, softening systems should be designed assuming that each softening system will perform regeneration (maximium 3 times) at least once a day. This process can happen no more than 3 times a day. How many times a day this process should be usually depends on the quality of raw water and the initial investment cost. Therefore, if the wrong choice is made, either the quality and quantity of the product water will decrease or the initial investment cost will be unnecessarily increased.
Absorbing coefficient of the resin to be used; There are many commercial resins used in water treatment systems. The important thing is to be able to meet the needs of the softening system and choose a resin that can completely soften the water. A saving of the resin type, taking into account commercial concerns, will lead to the inefficient operation of the system and then undesirable negatives such as lime/sediment formation. Especially in industrial applications, lime formation, damages and costs to be spent to eliminate are hundreds of times higher than the initial investment cost of resin. Therefore, the initial investment cost should not be avoided and a softening system should be designed by selecting a resin with a high coefficient of absorbing suitable for raw water.
Operating system; Softening systems can be operated in three different forms of application called Single, Dublex (Tandem) and Triplex depending on raw water hardness and the product water flow required. Single Softening Systems are systems used for low flow and relatively less hard water and are softening systems that do not produce product water during regeneration and operate intermittently.
Duplex (Tandem) softening systems, as the name suggests, are systems created by the way two single softening systems are connected in parallel. They are used in waters with high flow requirement and high hardness value. The system is designed to produce water at the flowne that is constantly needed and one of the softening units works, while the other completes the regeneration process and waits in a stand-by position. When the resin of the working softening system reaches saturation, the hibernation unit is activated and the regeneration of the other unit is carried out. This process is controlled fully automatic volumetrically and no human intervention is required. The flowmeter at the exit of the system determines which softening tank will be activated by measuring the amount of product water and this process continues sequentially. The most important point here is to accurately calculate the maximum amount of water that can pass through each softening system depending on the raw water hardness according to the resin absorbing coefficient and define it to automation. This value defined in system automation is measured by the flowmeter and sends a signal to the automatic valve group to commission the first tank as much as the value entered. When the calculated maximum pass flow is reached, the flowmeter sends a second signal, allowing the second softening tank to be activated, while the first softening tank is regenerated and left in a ready position. This process is repeated as long as water passes through the system sequentially, resulting in uninterrupted soft water.
Triplex (Triple Softening Systems) systems are also suitable for working in very high flow and very hard waters for continuous water production, such as Duplex (Tandem) systems. There are 3 softening systems in the system that operate independently of each other and operate in parallel. They are also controlled as fully automatic volumetrics, such as duplex (Tandem) systems. The system operates in the form of 2+1, that is, on the principle of regenerate and hibernate one while two units are in operation, and this process is repeated for each softening system, respectively.
Reverse Osmosis (osmos)
Factors Affecting Productivity ;
Water quality obtained by RO depends on many factors such as membrane type, operating pressure, pH, anchovy characteristics and temperature. 2-value ions such as Ca, Mg and sulfate are generally removed more effectively than single-value ions such as Na and Cl. Some substances, for example, are significantly affected by borate pH.
The pressure is;
Operation pressure in RO's; depends on the total dissolved solids in the feed water and the desired filter pressure efficiency. TDS decides the osmotic pressure of the system. 100 mg/lt TDS corresponds to 1 psi. The feed must be greater than the sum of the filter pressure with the difference in osmotic pressure. That's why seawater treatment requires much higher pressure than salt water. In addition, the increase in pressure difference improves the filtering quality. While the salt passage is constant, water pressure is increased and higher quality water is obtained.
This is not true, even if it is thought that by increasing the RO system pressure, as much water can be obtained as desired. Membrane manufacturers design according to max flow, daily water flow and surface area. This is due to the fact that minerals are made next to the membrane, known as concentration polarization. Furthermore, membranes get stuck over time due to pressure. This slows down the diffusion of water passing through it, and the production rate (flow rate) decreases.
The temperature;
The increase in the temperature of the feed water increases the filtering flow, but does not affect the quality of the filtering. Depending on the selectivity of the membrane structure, this heat effect can be 1.5-2% per 1 fahrenheit. Increasing the temperature is only beneficial below the membrane's special operation maximum. At temperatures above this, the membrane is damaged.
Recovery Percentage ;
The percentage of improvement in which the membrane works directly affects the filter quality. The elimination of non-ionic compounds such as organics, pyrogens (fever), cells, viruses and bacteria is the filtration process. In cases where the concentration of bacteria is very high, they can also be found in the filtering current. When the membrane passes through the pores , it is considered that this can happen, although it is not certain that they settled here. Therefore, pre-ro bacteriological treatment should be performed.
Factors Affecting Membrane Life;
In order to reveal design performance, factors that reduce filter quality and operational efficiency should be taken into account. Degradation is a decrease in production caused by inorganic, organic or microbiological reproduction. Or the descent could mean a decrease in water quality due to irreversible damage to the membrane surface.
Inorganic Contamination;
The most common inorganic contamination problems can be eliminated by proper pre-treatment.
Suspended Solids;
The typical filtration requirement is 25 microns or less, depending on the max 5 micron size in the perforated transition membrane and the feed rate in spiral wrapped membranes. Blur is usually considered smaller than 1 NTU.
Bicarbonate Alkalinite;
All water contains calcium bicarbonate and can turn into a form of calcium carbonate, or at the last stage it can form sediment and clog the membrane. To avoid this problem; the feed water is either softened or treated with acid to reduce pH to prevent calcium carbonate precipitation. In general, it uses pH control in small ro units, softening of small ro units, large units. If the membrane is clogged with calcium carbonate, it can be cleaned by washing with acid. Prepared acid washing apparatus is generally made with citric acid or phosphoric acid.
Calcium Sulfate;
Calcium sulfate is found in water at a limited resolution. If it is located in water, the feeding water passes through the saltwater section with filtering, its concentration increases and clogs the membrane, forming a deposit. Feeding water is treated with antisykalants or through the pre-softening unit. Membranes clogged with calcium sulfate can be cleaned by treating them with acid. Removing calcium sulfate with acid is more difficult than calciumcarbonate.
Iron, Manganese, Silicate and Colloidal Matter;
When dissolved iron in the water comes into contact with air, it oxidates or precipitates in such a way as to form ironhydroxide and/or ironoxide. This is a gelatinous precipitation and clogs the membrane. If the amount of iron is between 0.05 – 0.5 mg/lt, it should be removed with foreground. Iron blockage may be due to corrosion products. Problems caused by manganese, silicate, aluminum and colloidal substances are the same as iron.
Organic Contamination;
If the membrane is clogged due to organic substances, it can be cleaned with detergent or caustic soda. TFC membranes are considered to be easy to clean because they have a wider pH range tolerance than cellulosic membranes.
Microbiological Contamination;
Cellulose acetate membranes promote microbiological reproduction, while polyamide-type membranes do not. Both may face microbiological contamination problems. Cellulose acetate membranes are kept away from this contamination by chlorination of feeding water. Polyamide membranes cannot tolerate the oxidative properties of chlorine. chlorinated feeding water must be treated before entering the system.
Oxidation;
It is primarily related to TFC membranes and is considered when there is resistance to chlorine. However, not every oxide has the same effect. If the membrane is exposed to excessive oxidizing chemical, the system collapses and unacceptable salt transitions occur.
Hydrolysis;
It concerns cellulosic membranes and has parallels with the oxidation of TFCs. In the same way, the system can be damaged by hydrolysis and excessive salt passage occurs. This is irreversible harm, as in oxidation. The higher the pH of the water that the membrane feeds, the faster the hydrolysis occurs. Generally, pH max is limited to 8 – 8.5.
Polarization;
The membrane holds side by side two stagnant solutions, the mineral concentration of which is very different. This concentration is called polarization and is regulated by the membrane manufacturer with max filtering flow for membrane type. The longer membrane filtering, the longer the polarization lasts.
Drainage Connection;
The RO system represents the potential transit link between the feeding and drainage water, and therefore the appropriate drainage connection should be made in such a way as to prevent the passage of disease-causing bacteria to the water supply line.
Building Materials;
The modules operate in 200 psig and are made entirely of plastic material. The temperature limits of the plastic material exceed the temperature limits of the membrane. In the study of 400 psig and above, some sections are made of 304 stainless steel, bronze or brass.
