Antiscalant and its application in water and wastewater treatment industry
The preventive solution that is usually offered for this problem is the continuous use of anti-scalant. It is safe to say that antiscalant is the most essential chemical used in the process of industrial water purification. It is obvious that preventing the formation of deposits in this way will increase the life of the device and reduce its maintenance costs.
The solution provided to solve the problem of membrane clogging is the use of anti-fouling agent for anti-scalant in the system. Antiscalant is called membrane antifouling, because it is widely injected into industrial water treatment to prevent clogging of membrane filter openings. The use of these antifouling materials requires special attention, because if they are injected into the system in excess of the allowed amount, not only will they not be effective in removing membrane blockages, but they will cause more problems in the industrial water treatment system.
When using anti-scalant, we must be careful about the quality of the product; Among the famous anti-scalant brands, we can refer to Flucon 260 anti-scalant, Avista anti-scalant, and Genesis anti-scalant.
The necessity of using antiscalant
Anti-scalant is actually anti-scaling with effective compounds, which prevent the formation of mineral salts in water. This antifouling membrane is widely used in the water and wastewater treatment industry, but it is most widely used in industrial water treatment to prevent sedimentation on the membrane filter. Although antiscalants have different types in terms of their constituent materials, they all prevent the formation of calcium carbonate deposits on the surface of the membrane with high power.
The importance of using antiscalant in the reverse osmosis system is very high, otherwise the membrane filter will get clogged and fouled in a short period of time and lose its efficiency in water purification. The sedimentation on the membrane membrane in all reverse osmosis water purification devices with different feed water (such as brackish or well water, sea water, water containing silica or high sulfate) prevents. Therefore, the use of antiscalant in the reverse osmosis water purification system is very necessary.
Natural waters usually contain high concentrations of calcium, bicarbonate and sulfate ions, which can easily form sediment in the water purification process. Common mineral salts that usually contribute to the deposition on the membrane surface include calcium carbonate (CaCo3), calcium sulfate (CaSo4), barium sulfate (BaSo4) and strontium sulfate (SrSo4). Other uncommon descaling substances that can cause fouling or clogging of filter membranes are compounds such as calcium phosphate (CaPo4) and calcium fluoride (CaF2). When these compounds reach their saturation level in water, they cause crystallized particles and crystals on the surface of the industrial membrane filter membrane.
If this problem is not solved in the initial stages, after a short period of time, it will reduce the flux and flow rate, reduce the efficiency and increase the operating costs of the system. This time can be different depending on the type of sedimentary compounds and their saturation level. For example, in a water treatment system that has drinking water with high amounts of calcium sulfate, after 8 days and in another water treatment system that has significant amounts of calcium carbonate after 2 days, the production flow will face a sharp drop. Therefore, calcium carbonate can cause more serious problems for the water treatment system.
The preventive solution that is usually offered for this problem is the continuous use of anti-scalant. It is safe to say that antiscalant is the most essential chemical used in the process of industrial water purification. It is obvious that preventing the formation of deposits in this way will increase the life of the device and reduce its maintenance costs.
What factors cause membrane fouling?
The most important reasons for fouling and clogging of industrial water purification membranes can be said to be the lack of proper design and the use of a pre-treatment system suitable for the machine’s feed water, because if the RO pre-treatment process is done well, the amount of dissolved salts in the water entering the RO unit will undoubtedly be It will be much lower. In general, the important reasons for chemical deposition (scaling) on the membrane filter surface can be classified into four general categories:
• Increasing the concentration of mineral salts in the water entering the RO system
• Increasing the pH of the water
• Sediment formation and increase in sedimentation level
• Increase in water temperature
Important methods of controlling the formation of sediment on the surface of the membrane membrane
In general, there are three important methods to control deposits on the membrane surface, which are as follows:
• Acidification: adding acid to the feed water entering the industrial water purification membrane causes the removal of carbonate ions and destroys one of the active mediators required for the formation of calcium carbonate deposits. This method is very efficient in preventing the precipitation of calcium carbonate, but it does not have a good effect on other deposits. In addition, acid injection can cause corrosion of the tank and industrial equipment in the system, and most importantly, reduce the pH of the water coming out of the purification device.
• Antiscalant injection: Antiscalants are surface active substances, which have a high ability to maintain a supersaturated solution against water-soluble salts.
• Water softening through the ion exchange process: in this method, ion exchange resins are used to replace magnesium and calcium ions in water with sodium ions in the resin bed, as a result, the water entering the industrial water purifier is softened. After that, the membrane filter is washed and regenerated with a saline solution. This method reduces the need for continuous injection of acid and antiscalant, but its cost is much higher. Although resin systems are highly efficient, their use in systems containing feed water with high TDS or sodium ion concentration above the permissible limit is limited.
How antiscalant works to prevent scale formation
Antiscalant with its special properties prevents the formation of most mineral deposits and reduces the rate of sedimentation of these substances in the system. This sediment inhibitor is absorbed on the surface of the membrane membrane and prevents further growth of salt crystals and reaching the concentration required for sedimentation. Most of antiscalants have suspending or dispersing properties and by surrounding suspended salt particles, iron particles and organic substances, these substances are expelled by dissolved anions. In this way, it prevents the accumulation of particles that have a higher tendency to deposit. Antiscalants prevent sedimentation on the surface of industrial water purification membranes based on the following three mechanisms:
• Increasing the inhibition threshold: antiscalants have a high power to prevent the deposition of supersaturated salts.
• Changes in sediment structure: Anti-fouling membrane by changing the crystalline structure of sediments, turns them into soft and non-sticky sediments. Antiscalants that have a negative surface charge are able to absorb crystal positive ions and prevent the formation of sediment on the surface of the membrane.
• Spreading or dispersing property: Most antiscalants have an anionic structure and by inducing a negative charge to sediment particles, they suspend them and prevent the formation of a mass of particles.
The most important applications of antiscalant
Antiscalants are widely used in the sewage and water treatment industry, and if this antiscalant is chosen according to the desired industrial water treatment unit, it will remove fouling of membrane filters and improve the performance of the device. Among the uses of antiscalant, the following can be mentioned:
1- Special use in RO and UF systems with high inhibition capability
2- Nanofiltration (NF) systems
3- Industrial and semi-industrial desalination devices
4- Sea water desalination device
5- Water cooling systems (cooling towers)
6- Steam boilers and heating systems
7- Descaler in refrigeration systems
8- Oil, gas and petrochemical industries (to prevent sediment formation)
The unique advantages of anti-scalant
The important advantages of antifouling membranes include the following:
Preventing the formation of any sediment on the surface of the membrane
Membrane protection
Longer lifetime of membrane filters
Easy to use because it is liquid
Optimum recycling
Environmental compatibility
Reduction of biodegradation by high efficiency
Stability in system performance
Low injection dose and affordability
Types of anti-scalant
In addition to acid and alkaline types, antiscalants are classified into the following two types based on their ingredients and chemical formula:
• Phosphate-based antiscalant (phosphonate)
Phosphonate-based antiscalants have carboxylic acid and phosphate functional groups. These antiscalants are among the best types in preventing the formation of sulfate and carbonate deposits, but they have much more limited spreading properties. This type of antiscalant is made of polyacrylic molecules with low molecular weight (in the range of 100 to 5000) or high molecular weight (in the range of 6000 to 25000) and contains several functional groups of carboxylic acid (COOH-).
Combined type antifoulants usually perform better compared to single molecule antifoulants. If monomolecular antifouling is injected into the system in an amount greater than the allowed limit, the inhibitor itself will be removed from the solution as a polyvalent cation. Some commonly used antiscalants are a combination of polyacrylics with light and heavy molecular weight, so that the produced product has a higher inhibitory power.
• Polymer based antiscalant
These types of antiscalants have a high molecular weight and prevent the formation of deposits such as carbonate and phosphate deposits to a high extent. This type of anti-scalant is non-toxic and does not cause skin or respiratory problems in case of contact with the body.
Polymeric antiscalants have a very high concentration and a very low corrosion rate, and their use is suitable for sea water, salty wells, and water that has a hardness of less than 1000 mg/liter. This type of anti-sediments has a very favorable performance in preventing the formation of algae and biological pollutants.
Buy and price of antiscalant
In the maintenance process of the industrial water purifier, it is vital to use a suitable anti-scalant to prevent sedimentation and remove membrane filter fouling. For this purpose, the selection of acidic or alkaline antiscalant and its type should be done according to the complete analysis of the incoming water, system performance and the type of sediment created on the membrane membrane. This analysis includes the measurement of TDS, sulfate, alkalinity and total hardness (TH) of the water.
Buying the correct anti-scalant is very important and if not done correctly, it can cause more deposits on the membrane surface. In addition, the compatibility of the selected antiscalant with the membrane filter of the device is important, because if an antiscalant incompatible with the membrane is used, it will lead to clogging and fouling on its surface. The price of anti-scalant also depends on various factors, including the brand and ingredients.
To change this text, click on the edit button. Lorem Epsom is a fake text with incomprehensible simplicity produced by the printing industry and using graphic designers. Disadvantages of using low-quality antiscalant
It should be noted that if the antiscalant is not used correctly, it will not only cause the membrane filters to become clogged, but also cause serious problems in the water purification system. These problems include the following:
Pressure increase on the floor pump and its failure
More energy consumption
Reducing the output water flow
Increasing the amount of dissolved substances and TDS of the outgoing water
Increasing the frequency of membrane washing and reducing its useful life
Short-term replacement of membrane filters
The best and highest quality anti-scalant brands
It is very important to choose the appropriate antiscalant compatible with membrane filters, because if this choice is not made carefully, it may cause the formation of sediment and membrane fouling. The best and highest quality anti-scalant brands
Anti-scalant in different types and brands have been produced and marketed by the relevant companies. There are imported and domestic types of anti-scalants available in Iran. These imported products include Avista anti-scalant, Flucon and Genesis anti-scalant. The most famous anti-scalant products in Iran are Flucon 260, made in England, Avista brand, and Tochal Shimi, which use the best raw materials in their production.
Flucon 260 anti-scalant
Antiscalant Flocon 260 is an aqueous solution of polycarboxylic acid, which prevents the formation of mineral salt deposits and the clogging of industrial membrane filters. This antiscalant is an additive to water that must be placed in the pre-treatment section of the reverse osmosis system in the device. Flocon 260 anti-scalant is actually a multi-purpose anti-fouling, which can be used for a wide range of feed water, including sea water and brackish water (well water). This Floken anti-fouling is a light yellow liquid in appearance, which has a pH lower than 2 and is slightly acidic.
Injecting the allowed dose of Flocon 260 antiscalant can reduce the pH of water and increase the solubility of calcium carbonate and eliminate membrane fouling. This antiscalant prevents the formation of all sediments containing carbonate, sulfate and fluoride to a high extent. Other types of this antiscalant are Flocon 135, 190 and Flocon Plus, but the use of Flocon 260 anti-scalant in the reverse osmosis system is much more common than other products.
Avista anti-scalant
Avista anti-scalant is a product of Avista Vitec brand, which is sold in 25, 230 and 1100 kg gallons with good quality and reasonable price. This membrane antifouling material prevents the formation of all organic and inorganic deposits such as calcium carbonate, calcium sulfate, barium sulfate, calcium fluoride, strontium sulfate, and silica deposits. Due to the nature of its ingredients, Avista antiscalants are fully compatible with all kinds of organic materials and perform well even in low injection doses. Avista anti-scalants have different types and models, such as Vitec 4000, 2000, 3000 and Vitec 1000 models, and its best-selling products are Vitec 5000, 5100 and 5300 models.
The chemical composition of Avista anti-scalant model 5300 is similar to Flucon 260 and it is recommended to use it pure in the system. If there is a need to dilute this product, it is better to consult with the product supplier first. Avista antiscalant model 5300 is a light amber liquid with a pure pH in the range of 5.5 to 6.5, which is soluble in feed water in any ratio. Vitec 5300 model anti-scalant is very effective in preventing mineral and organic deposits due to its special formulation. It is cost-effective to use this product in marine reverse osmosis systems and urban drinking water. The exact injection dose of Avista antiscalants can be calculated using the special software of this company called Avista Advisor.
Antiscalant Genesis
Genesys antiscalant is a neutral solution containing phosphonic acid, which consists of non-toxic materials. This antifouling membrane is a straw-colored liquid with a pH in the range of 9.8 to 10.2. Genesis anti-scalant is a concentrated phosphate anti-fouling, which prevents the formation of most mineral deposits such as carbonate and sulfate and trivalent metals such as iron, aluminum and manganese on the surface of the membrane filter. Antiscalant Genesis is completely compatible with all carbon steel pipes and similar materials due to the type of ingredients.
The injection dose of this antiscalant in the reverse osmosis system is usually between 0.5 and 1 ppm, and according to the NSF standard, this antiscalant should be used in concentrations lower than 5 ppm. Since, like other membrane anti-fouling agents, injecting the exact dose of Genesis antiscalant in the system is very important, its exact amount can be calculated using the exclusive Genesys Membrane Master software. Important applications of Genesis Antiscalant include the use to recycle salt water or reduce the pH of raw water, even if the pH of the water has not been reduced by injecting acid. Genesis antiscalant is compatible with all types of membrane filters and is suitable for use in brackish water and sea water. This anti-scalant has different types and is sold in 25, 250 and 1300 liter gallons.
Safety recommendations for the use of anti-scalant
Acidic and alkaline antiscalants are dangerous chemicals, which will cause serious damage to a person’s health if they come into contact with the body. Therefore, it is necessary to use gloves and glasses for chemicals, an anti-acid mask with a suitable filter, anti-acid clothes and boots when using anti-scalant, and if this problem occurs, following the safety recommendations below can prevent further damage. The accident victim should prevent:
• Contact of anti-scalant with the skin can cause sensitivity and inflammation in the skin. If this problem occurs, wash the skin immediately with plenty of water for 15 minutes.
• Inhaling this anti-fouling substance can cause damage to a person’s pulmonary system. In case of encountering this danger, it is necessary to move the person to the open environment and use an artificial respiration device if necessary.
Contact of the antifouling membrane with the eye can cause burns. If this hazard occurs, immediately flush the eye with plenty of water for 15 minutes.
• Swallowing some anti-scalant can cause stomach irritation and damage to the digestive system. If you face this danger, first keep your cool and give the person enough water and fluids, if necessary, take the injured person to the medical center.
Antiscalant injection unit in industrial water purification devices
Antiscalants are mainly named according to their inhibition power by an index called Langelier Index (LSI). In fact, this index indicates the tendency to create sediment and corrosion in the system and depends on parameters such as temperature, pH and water hardness. Based on this, zero LSI indicates a state of balance and lack of desire to create sediment and corrosion in the system. It should be noted that the Langelier index is only used at a temperature lower than 80 degrees and in slow water flows, so the use of antiscalant is not suitable for systems such as boilers or steam boilers.
شاخص لانژلیه مناسب برای آنتی اسکالانت معمولاً در محدوده 1 تا 2 است و اگر شاخص لانژلیر ضد رسوب مورد نظر بالاتر از 2 باشد، جهت کاهش اندیس لانژیلر معمولاً از آنتی اسکالانت به همراه اسید استفاده می شود. اسیدهایی که عمدتاً بدین منظور استفاده می شوند، اسید کلریدریک و اسید سولفوریک هستند. از آنجایی که تزریق اسید سولفوریک به میزان بالا می تواند سبب فولینگ فیلتر ممبران شود، بنابر این از این اسید به صورت محدودتری استفاده می گردد.
برای تزریق مداوم ضد رسوب ممبران از واحد تزریق آنتی اسکالانت در دستگاه RO استفاده می شود. بدین منظور توجه به این نکته اهمیت دارد، که در صورت خاموش کردن دستگاه، واحد تزریق آنتی اسکالانت نیز بلافاصله متوقف گردد. مناسب ترین مکان برای نصب واحد تزریق آنتی اسکالانت پس از فیلترهای شنی و کربنی و نیز پیش از فیلترهای کارتریج یا میکرونی می باشد، بنابراین موجب جلوگیری از تشکیل رسوب بر سطح فیلتر ممبران و فیلترهای کارتریجی شده و درنتیجه طول عمر آنها را افزایش می دهد. سیستم تزریق آنتی اسکالانت دارای یک میکسر، دوزینگ پمپ و مخزنی برای نگهداری محلول آنتی اسکالانت می باشد.
Antiscalant injection dosing pump
Dosing pumps or in other words metering pumps are pumps that pump or inject a specific dose of a liquid in the system, in this sense they are also called injection pumps. In these pumps, parameters such as flow rate and pressure are of great importance, as a result, these devices are usually designed in such a way that the flow rate passing through the pump can be adjusted. An important feature that separates the dosing pump from its similar pumps is the ability to change the direction (period) of going back and forth. It should be noted that in all dosing pumps, the flow rate also changes when the flow direction changes. However, in most of these pumps, changing the injection frequency is also used to adjust the flow rate.
Activities performed in this project:
– Design and purchase, installation and operation of the control valve panel
– Buying Siemens PLC modules and installing them in the PLC panel of the control room
– Programming the valve control loop with advanced Siemens PCS7 software
– Transmitting the signal of the flowmeter and the control valve of the Varamin route to the PLC panel of the control room
Before the implementation of this project, the control valve of the Varamin route was controlled through an RTU board that was located in the corner of the conference room of the treatment plant and had no connection with the control system of the treatment plant, causing problems for the operators.
With the implementation of this project, the RTU board was completely removed and some input and output modules were installed in the PLC board of the control room and connected to the control system.
A bamboo wall panel was made for the control valve and next to the PLC panel of the control room
was installed
It was possible to open and close the control valve from the panel door.
At the same time, the percentage status signal of the control valve and the instantaneous flow rate of the Varamin route were also transferred to the HMI screens of the control room.
It was possible to apply the flow set point on the HMI pages and the operator could apply any set point.
According to the telemetry network between the treatment plant and the central water and sewage building of Tehran, the important information of the treatment plant was transmitted online, and the discharge signal of the Varamin route was also transmitted to Tehran with this method.
Activities performed in this project:
– Design and purchase, installation and operation of the control valve panel
– Buying Siemens PLC modules and installing them in the PLC panel of the control room
– Programming the valve control loop with advanced Siemens PCS7 software
– Transmitting the signal of the flowmeter and the control valve of the Varamin route to the PLC panel of the control room
Before the implementation of this project, the control valve of the Varamin route was controlled through an RTU board that was located in the corner of the conference room of the treatment plant and had no connection with the control system of the treatment plant, causing problems for the operators.
With the implementation of this project, the RTU board was completely removed and some input and output modules were installed in the PLC board of the control room and connected to the control system.
A bamboo wall panel was made for the control valve and next to the PLC panel of the control room
was installed
It was possible to open and close the control valve from the panel door.
At the same time, the percentage status signal of the control valve and the instantaneous flow rate of the Varamin route were also transferred to the HMI screens of the control room.
It was possible to apply the flow set point on the HMI pages and the operator could apply any set point.
According to the telemetry network between the treatment plant and the central water and sewage building of Tehran, the important information of the treatment plant was transmitted online, and the discharge signal of the Varamin route was also transmitted to Tehran with this method.
Activities performed in this project:
– Designing the SCADA system of the treatment plant
– Preparation of required control documents
– Modification of the PLC program of the units
– Programming in the control room with Siemens STEP7 software
– Designing HMI pages with Siemens WINCC software
– Testing feedback and command of units in the control room
Before the implementation of this project, different units were working independently and the operator should always check the present unit and the system.
The SCADA system was implemented with Profibus network and fiber optic substrate in the form of a ring.
Activities performed in this project:
– Preparing the map of the boards
– Designing floor pump board map
– Purchase and installation of screed pumps
– Purchase and installation of the engine room panel
– Purchase and installation of JB behind the lime board
– Purchase and installation of floor pump JBs
– Corrections related to lime board
– Buying cables and trays and unifying the boards of floor screed pumps
The electric panels of Ahek package were very irregular and poorly made, and the operators were facing problems in fixing the defects. Also, there was no map of the panels.
With the presence of technical people for several days, the plans of the boards were prepared and the necessary corrections were made.
The electrical panel of the engine room was also rotten and damaged, which was replaced with a high-quality galvanized panel.
Mission statement in the electrical, instrumentation and automation sector
The engineering and design department of this company, by benefiting from the cooperation of expert experts with an average of 15 years of design experience in industrial projects, provides its engineering services in the field of basic or detailed electrical design, control and precision instruments, machine mechanics, pipes They provide drawing and process. Among the experiences in the mentioned team are basic and advanced design in petrochemicals, refineries, urban water and sewage treatment plants, industrial wastewater treatment in steel industries, cement industries, etc.
In the industrial water treatment system, antiscalant is usually injected into the device after sodium meta bisulfite to remove the chlorine in the water before it enters the membrane filter. The proper injection dose of antiscalant in the reverse osmosis system is measured as follows: amount of antiscalant consumed in 24 hours (gr) = (1-6ppm) recommended dosage x volume of water entering the system in (m3) for 24 hours
