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200 FAQs on Water Treatment Basics

200 FAQs on Water Treatment Basics

Article Introduction This article summarizes 200 basic principles of water treatment. Although brief, this knowledge is practical and will help you in your studies and work, and provide a better understanding of the water treatment industry. 1. 001×7 type resin is (strong acid cation exchange resin). 2. Regular boiler blowdown is mainly to remove (water slag). 3. The ion exchange process is essentially a process of gradual downward movement of the (working) layer. 4. When using strong and weak base resins together, the weak base resin exchanges strong acid root ions, and the strong base resin exchanges (weak acid root ions). 5. The chemical name of Na3PO4 is (trisodium phosphate). 6. The filling ratio of mixed bed anion and cation resins (anion:cation = 2:1). 7. Boiler blowdown methods include continuous blowdown and (periodic blowdown). 8. The temperature control range for anion resin regeneration solution is (30～45℃). 9. The resin layer in the operating exchanger can be divided into the exhausted layer, the working layer, and the (protective layer). 10. When a weak base anion exchanger fails, the first ion to leak is (chloride). 11. When a strong base anion exchanger fails, the first ion to leak is (silicate). 12. During filtration, impurities in the water undergo surface adsorption and (mechanical retention) after contacting the filter media. 13. The total mass of the substances participating in a chemical reaction is equal to the total mass of the substances produced after the reaction. This law is called the (law of conservation of mass). 14. The unit of conductivity is (μS/cm). 16. Resins are composed of two parts: a framework and (active groups). 17. Impurities in natural water are divided into suspended solids, colloids, and (dissolved impurities) according to particle size. 18. In thermal equipment, dissolved oxygen corrosion occurs severely in the (feedwater) system. 19. Chemical oxygen demand is generally represented by the symbol (COD). 20. The molecular formula of sulfuric acid is (H2SO4). 21. Methods for feedwater deoxygenation include thermal deoxygenation and (chemical) methods. 22. Ammonia is added to feedwater to increase (feedwater pH) and prevent CO2 from causing acid corrosion of pipes. 23. Hydrazine is added to feedwater to (remove residual oxygen after thermal deoxygenation to prevent oxygen corrosion of pipes). 24. Safety generally refers to a state of (no danger, no accidents). 25. Work performed more than (2) meters above the ground should be considered high-altitude work. 26. The main function of mixed bed backwashing is (separation of anion and cation resins). 29. For resin model 201×7, 2 indicates that the resin is (strongly alkaline). 30. In a mixed ion exchanger, anion and cation resins are separated based on their different (densities). 31. Anion resins should be protected from oil and (organic matter) contamination. 32. To prevent anion resin degradation, (oxidants) in the influent must be removed. 33. The safety production management policy determined by the "Safety Production Law" is (safety first, prevention first). 34. The regeneration process of ion exchange resin is actually the (reverse reaction) of the desalination process. 35. For motors that have been shut down for more than 15 days, contact electrical operation personnel to measure (insulation) before starting. 36. For metering pumps with a speed of 200～400 r/min, the vibration value should be less than (0.15) mm. 37. When the temperature of the pump motor bearing exceeds (75) ℃, the backup equipment should be started, and the heating equipment should be stopped. 40. The criterion for judging the end point of backwashing separation of cation and anion resins in a mixed bed is (a clear separation line between cation and anion resins). 41. If the backwashing separation boundary of cation and anion resins in a mixed bed is not clear, (NaOH) solution with a concentration of 1～2% should be added to the mixed bed, and then the layers should be separated again. 42. After (2 weeks) of operation for a new pump or a pump that has undergone major repairs, the oil should be changed once if it is oil lubricated, and the solid oil should be replenished once. After that, the oil should be changed every (3 months). This work is completed by the operation notifying the maintenance personnel. 43. The vibration of centrifugal pumps with a speed less than 1800 rpm should be less than (0.7 mm), and the vibration of centrifugal pumps with a speed of 1800-4500 rpm should be less than (0.06 mm). 44. The main factors affecting filter operation are backwashing time, intensity, (filtration rate), and (uniformity of water flow). 45. The main factors affecting coagulation treatment effects include: water temperature, water pH, (dosage), raw water quality, and contact media. 46. The water quality indicators for demineralized water are: YD (≈0 μmol/L), SiO2 (≤20 μg/L), DD (≤0.2 μS/cm), 47. In low phosphate treatment, the phosphate content is controlled at (0.5～3 mg/L), the pH is controlled at (9.0～9.8), and the conductivity is controlled at (60 μS/cm). 48. Low phosphate treatment can reduce or eliminate the phenomenon of (phosphate hiding) in boilers. 49. When starting a chemical metering pump, the (outlet valve) must be opened first, then the (pump) is started. 50. When stopping a chemical metering pump, press the (stop) button first, then close the (outlet valve). 51. Boiler blowdown methods are divided into (continuous blowdown) and (periodic blowdown). 52. The purpose of ammonia treatment of feedwater is (to increase the feedwater pH and prevent carbon dioxide corrosion of feedwater pipes). 54. When an online conductivity meter measures the quality of feedwater, condensate, and steam, the water sample must first be treated with a (hydrogen ion exchange column). 55. Periodic blowdown should be carried out at the intervals specified in the boiler operation regulations. Periodic blowdown is performed by (boiler) professionals and supervised by (chemical) professionals. 56. During normal operation, adjust the dosage of the ammonia pump in time according to the feedwater pH value, and control the feedwater pH value within the range of (8.8～9.3). 57. The main reasons for steam contamination are: (mechanical carryover) and (dissolved carryover). 58. During fluidized bed regeneration, the direction of the regenerant is (top-down). Compared with fixed beds, it can better ensure that the resin layer is in a stable and compacted state, and will not cause (layer disorder). 59. When starting to wet dry resin, it should not be soaked in pure water. Generally, (saturated brine) is used to soak it to prevent the resin from (swelling and dissolving) and cracking. 60. The continuous blowdown pipe is generally installed (200～300 mm) below the normal water level of the steam drum. 61. The iron removal filter for process condensate uses (porous filter elements) to intercept suspended impurities. When the resistance increases to a certain value, it is backwashed with (water and air). 62. Methods for removing dissolved gases from water include (thermal deoxygenation) and (chemical reagent) methods. 63. Our unit uses (ultrafiltration) and (reverse osmosis) with a shared chemical cleaning system. 64. "Two tickets" refer to (work permits) and (operation permits). 65. If the backwashing layering is not obvious during mixed bed regeneration, a small amount of (alkali) can be added. 66. Reverse osmosis (RO) chemical cleaning is divided into (alkaline cleaning) and (acid cleaning). 67. The amount of resin filled in the exchanger is usually calculated by multiplying the volume of resin filled in the exchanger by the (wet apparent density). 69. The so-called hardness usually includes (carbonate) hardness and (non-carbonate) hardness. 70. When the anion bed is in operation, when starting the mixed bed, first open the (vent valve) and (inlet valve). After water comes out, open the mixed bed (bottom drain valve), close the vent valve, and flush until the water quality is qualified. Then open the (product water valve) and close the (bottom drain valve) to start operation. 71. Untreated water is called (raw water), and water with calcium and magnesium hard salts removed is called (softened water). 73. The chemical water treatment unit monitors the (TOC) of the process condensate. Unqualified water is directly discharged to the (wastewater collection pool) and does not enter the subsequent treatment system. 75. Activated carbon filters mainly adsorb (organic matter) and (residual chlorine) in water. 77. The indicators characterizing steam quality are (silicon) and (sodium). 81. Methods for power plant supplementary water treatment include (chemical treatment) and (heat treatment). 82. Coagulation tests generally require determining the (optimal dosage) and (optimal pH). 83. When the anion bed is in operation, when starting the mixed bed, first open the (vent valve) and (inlet valve). After water comes out, open the mixed bed (bottom drain valve), close the vent valve, and flush until the water quality is qualified. Then open the (product water valve) and close the (bottom drain valve) to start operation. 84. Filtration can be divided into (mechanical filtration) and (adsorption filtration). 85. Low phosphate treatment is suitable for the treatment of (feedwater with long-term no hardness). 88. Low phosphate treatment can reduce or eliminate the phenomenon of (phosphate hiding) in boilers. 89. The purpose of using an acid mist absorber is (to avoid environmental pollution). 90. Sampling devices for deoxygenated water, feedwater, boiler water, steam, and blowdown must be equipped with (coolers). 91. The continuous blowdown rate of the boiler should not be less than (0.30%). 92. The purpose of continuous blowdown is to remove (suspended impurities) and (high-salt boiler water) from the boiler water. 93. When the reverse osmosis inlet water temperature is high, the desalination rate will (decrease) and the recovery rate will (increase). When the inlet water temperature is low, the recovery rate will (decrease). 94. In order to prevent the loss of ion exchanger resin, a (resin catcher) is generally installed on the outlet pipe of the mixed bed as a preventive measure. 95. In reverse osmosis, the role of the semi-permeable membrane is to allow only (water) to pass through, but not (salt) ions or molecules. 96. The self-cleaning filter is a fully imported product and can be fully automatically operated by controlling the power supply. When it runs to a certain (time) or (pressure difference), it can automatically use (self-produced water) for backwashing. During backwashing, the raw water pump (continues to operate) without any changes or stops. 97. "Three violations" refer to: violation of command, violation of operation, (violation of labor discipline). 98. The items generally monitored during normal operation of the anion bed are the conductivity and (silicon content) of the effluent. 99. For anion exchangers, the greater the influent (acidity), the better. 100. (Pneumatic diaphragm valves) are composed of two parts: a diaphragm valve and a pneumatic actuator. 101. The key reason for poor regeneration of mixed ion exchangers is poor (backwashing layering) effect. 102. pH is the negative logarithm of the concentration of (H-). 103. If the dissolved oxygen in the feedwater is unqualified, it can be considered that the operation condition of the (deaerator) is poor. 104. If the water pump does not pump water and the outlet pressure gauge indicates a high pressure, after excluding the valve problem, the (outlet pipe) should be considered to be blocked. 105. The main reason for the deterioration of cation resin is that it is easily corroded by (oxidants). 106. The greater the water permeability of the reverse osmosis membrane, the greater its (desalination rate). 107. When selecting ion exchange resins, the (particles) of the resin should be as uniform as possible. 108. The wet true density of cation resin is usually (smaller) than that of anion resin. 109. For boiler steam drums, poor water quality will cause scaling, salt accumulation, and (metal corrosion) in the water-steam system. 110. When adding ammonia to feedwater, if the amount of ammonia is (too large), it may cause corrosion of copper pipes. 111. When the boiler load increases sharply, PO43- in the boiler water decreases, and phenolphthalein alkalinity increases, which is because the salt temporarily (disappears). 112. When a cation exchanger fails, the conductivity will temporarily (decrease). 113. The pH of demineralized water is generally between (6.5-7.5). 115. Generally speaking, the chemical stability of anion resin is (worse) than that of cation resin. 116. The smaller the crosslinking degree of ion exchange resin, the greater the water content of the resin, and the stronger the anti-pollution performance. 117. Phosphate treatment can both prevent corrosion and (scaling). 118. When the pH of water ≥8.3, it indicates that (no) CO2 exists in natural water. 119. After ion exchange resin is contaminated by iron, aluminum, and their oxides, the color (darkens). 120. In natural water, the most common metal ions that form water hardness are (Ca2+, Mg2+). 121. In natural water, the alkalinity of water is mainly composed of salts of (HCO3-). 122. Substances usually have three aggregation states: (solid), (liquid), and (gaseous). Under certain conditions, these three states can be transformed into each other. 123. The reaction of an acid and a base to produce a salt and water is a (neutralization) reaction. 124. A solution is composed of a (solvent) and a (solute). 125. A solution that can resist changes in pH when strong acids or strong bases are added is called a (buffer solution). 126. pH=7 indicates that water is (neutral), pH<7 indicates that water is (acidic), and pH>7 indicates that water is (alkaline). 127. The smaller the pH value, the (higher) the concentration of (hydrogen) ions. 128. In redox reactions, the substance that loses electrons is called the (reducing agent), and the substance that gains electrons is the (oxidizing agent). 129. The pH of a solution is equal to the (negative logarithm) of its (hydrogen ion concentration). 130. The role of filling a certain height of inert white balls in the fluidized bed is (to protect the resin and prevent broken resin from blocking the water outlet device). 131. When the pressure difference between the inlet and outlet water of the fluidized bed reaches (0.2) MPa or more, the resin should be cleaned. 132. After the boiler is ignited, when the pressure rises to (1.0 MPa), start the phosphate dosing pump and start adding chemicals to the boiler water. When the boiler water has hardness, the phosphate content in the boiler water should be controlled at the (upper limit). 133. After the boiler is ignited, when the pressure rises to (1.0 MPa), continuous blowdown is started; if the boiler water appears cloudy, appropriate (periodic blowdown) should be carried out. 134. During normal operation, the oil level in the oil chamber of the metering pump should be (1/3 to 2/3) of the oil window. 135. The online instrument cabinet is equipped with an automatic temperature control device to maintain the water sample temperature at (25±2℃). 136. When the unit starts, the content of various water sample impurities is high, and (blowdown) should be carried out for each steam and water sample. 137. Ammonia is added to the feedwater in the (deaerator downcomer). 138. When the unit is running normally, the ammonia pump should be kept running (continuously). 139. When the stroke of the ammonia pump is adjusted to a very small value, but the feedwater pH is still high, the operator should (add water to dilute) the ammonia solution in the ammonia solution tank. 140. The main reasons for steam contamination...

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Discussion on the resource recovery and utilization of reverse osmosis concentrate

Discussion on the resource recovery and utilization of reverse osmosis concentrate

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The Ministry of Ecology and Environment released the 2021 Yellow River Basin "Clean-up Action" work progress.

The Ministry of Ecology and Environment released the 2021 Yellow River Basin "Clean-up Action" work progress.

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2022

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The Ministry of Ecology and Environment issued the "Enterprise Environmental Information Disclosure Format Standard"

The Ministry of Ecology and Environment issued the "Enterprise Environmental Information Disclosure Format Standard"

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2022

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The first day of the first lunar month is called New Year's Day.

The first day of the first lunar month is called New Year's Day.

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A review of the salt freezing and denitrification process for chemical nitrate-containing wastewater

A review of the salt freezing and denitrification process for chemical nitrate-containing wastewater

Article Publication Recently, Honzon Company successfully published a research paper titled "Review of Salt and Nitrate Separation and Cold Crystallization Technology for Chemical Wastewater Containing Nitrate Salts" in "China Well and Mine Salt", with the publication number being Volume 52, Issue 6, 2021. Honzon Company focuses on innovation of new technologies, research and development of new processes and products, and attaches importance to R&D investment. It has made continuous breakthroughs in research results and has now developed into a world-class provider of zero-discharge wastewater solutions and membrane equipment. The salt separation process for chemical wastewater containing nitrate salts is widely used in the environmental protection field. This article compares and analyzes the composition characteristics of chemical wastewater containing nitrate salts and the technical and economic aspects of the applied salt separation and cold crystallization technology for nitrate extraction, and draws preliminary conclusions on various process routes. Publication Details Magazine Article Inside Pages Original Content Summary I. Existing Salt Separation and Cold Crystallization Technology for Nitrate Extraction from Chemical Wastewater Containing Nitrate Salts The components of nitrate wastewater from a certain coal chemical enterprise are shown in Table 1. Table 1 Nitrate Wastewater Components Analysis of Table 1 shows that the nitrate wastewater has complex components, including sodium sulfate, sodium chloride, sodium nitrate, magnesium sulfate, calcium sulfate, sodium fluoride, sodium bicarbonate, COD, etc. After pretreatment, chemical wastewater usually contains salt, nitrate, and COD. Due to the presence of COD, traditional processes such as the thermal salt-nitrate co-production process are limited, and the investment risk of the device is increased. Therefore, in recent years, environmental protection projects in the industry have adopted the cold crystallization technology for nitrate separation to achieve nitrate-salt separation. The existing salt separation and cold crystallization technology for nitrate extraction from chemical wastewater containing nitrate salts mainly includes: 1.1 Evaporation denitrification, cold crystallization denitrification, and evaporation desalination process (referred to as Process 1) The components of the reverse osmosis concentrated brine after pretreatment of nitrate wastewater from a certain coal chemical enterprise are shown in Table 2. Table 2 Reverse Osmosis Concentrated Brine Components Using reverse osmosis concentrated brine as raw material, the process flow of evaporation denitrification, cold crystallization denitrification, and evaporation desalination (Process 1) is shown in Figure 1. Using reverse osmosis concentrated brine as raw material, evaporation and concentration crystallization are used to obtain sodium sulfate. The nitrate-making mother liquor is frozen to obtain mirabilite, which is returned to the evaporation nitrate-making process to recover sodium sulfate. The cold crystallization denitrification brine is evaporated to obtain sodium chloride, and the salt-making mother liquor is dried to obtain mixed salts. Figure 1 Process Flow Diagram of Evaporation Denitrification, Cold Crystallization Denitrification, and Evaporation Desalination Process 1 1.2 Nanofiltration, cold crystallization denitrification, evaporation desalination, and evaporation denitrification process (referred to as Process 2) The components of the nanofiltration dilute brine and concentrated brine after pretreatment of nitrate wastewater are shown in Tables 3 and 4 respectively. Table 3 Nanofiltration Dilute Brine Components Analysis of Table 3 shows that when the nanofiltration dilute brine of nitrate wastewater is evaporated, sodium chloride precipitates first, and then other components are concentrated and saturated. Table 4 Nanofiltration Concentrated Brine Components Analysis of Table 4 shows that when the nanofiltration concentrated brine of nitrate wastewater is evaporated, sodium sulfate precipitates first, and then other components are concentrated and saturated. Based on the above Tables 1-3 nanofiltration dilute brine and Tables 1-4 nanofiltration concentrated brine components, the process flow of nanofiltration, cold crystallization denitrification, evaporation desalination, and evaporation denitrification (Process 2) is shown in Figure 2. Using the pretreated brine as raw material, sodium chloride (dilute brine) and sodium sulfate (concentrated brine) solutions are obtained through pretreatment and nanofiltration. The concentrated brine is frozen to obtain mirabilite; the dilute brine is evaporated to obtain sodium chloride; the dissolved mirabilite solution and the nitrate-making mother liquor are evaporated to obtain sodium sulfate; and the salt-making mother liquor and nitrate-making mother liquor are dried to obtain mixed salts. II. Technical and Economic Analysis of the Process 2.1 Technical and Economic Analysis of Process 1 Sodium sulfate and nitrate-making mother liquor are obtained by evaporation and crystallization of reverse osmosis concentrated brine. The amount of nitrate-making mother liquor is small, and the refrigeration load is small; the reasonable utilization of equipment for returning mirabilite to the evaporation nitrate-making process for recovering sodium sulfate is conducive to reducing investment; the sodium chloride evaporation process in the brine is rich in COD, and the evaporation crystallization impurities are many, resulting in poor salt quality; the end point of the salt-making mother liquor evaporation is affected by the co-saturation point of salt and nitrate and the COD concentration, resulting in a small amount of salt-making mother liquor and less mixed salts obtained by drying. 2.2 Technical and Economic Analysis of Process 2 Using the pretreated brine as raw material, sodium chloride (dilute brine) and sodium sulfate (concentrated brine) solutions are obtained through pretreatment and nanofiltration; the sodium chloride (dilute brine) contains less COD and sodium sulfate, and the quality of the evaporated salt is better, which is beneficial to downstream use; The concentrated brine is frozen to obtain mirabilite and brine, with a large freezing amount and high energy consumption; the brine and dissolved mirabilite solution are evaporated to obtain sodium sulfate separately, the device setting is unreasonable, and the investment is increased; the brine contains high calcium, magnesium, and COD concentrations, which affect the evaporation and brushing cycle and the amount of mother liquor discharged; the amount of salt-making mother liquor and nitrate-making mother liquor at the evaporation end point is large, and more mixed salts are obtained by drying. III. Process Improvement Suggestions 3.1 Improvement Suggestions for Process 1 It is suggested that in the process: measures to reduce the amount of calcium, magnesium, and COD in the brine should be added, the evaporation conditions of sodium chloride should be improved to obtain better salt quality, and the use of salt should be expanded. 3.2 Improvement Suggestions for Process 2 It is suggested that in the process: the salt-making mother liquor should be frozen, the recovery rate of sodium sulfate should be increased, and the amount of mixed salts should be reduced; measures to reduce the amount of calcium, magnesium, and COD in the brine should be added, the evaporation conditions of sodium sulfate should be improved, and the amount of mixed salts should be reduced; the mirabilite should be returned to the brine evaporation process to reduce the investment in the sodium sulfate evaporation process.

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