Ultimate Guide to Water Treatment: Everything You Need to Know

Glossary of Water Treatment Terms (Summarized in Eight Key Areas)

1. Raw Water: Refers to untreated natural water or municipal tap water, also known as unprocessed water.
2. Clarified Water: Water that has had suspended impurities removed.
3. Deionized Water: Water from which cations and anions have been largely removed, often through methods like distillation, electrodialysis, reverse osmosis, or ion exchange.
4. Turbidity: Indicates the cloudiness of water, caused by suspended particles (including colloids), measured in NTU (Nephelometric Turbidity Units). It is a key indicator of water clarity and potential contamination.
5. Flocculant: A chemical that causes suspended particles in water to coalesce and settle.
6. Total Alkalinity: The total concentration of substances in water that can neutralize strong acids.
7. Acidity: The total concentration of substances in water that can neutralize strong bases.
8. Hardness: Refers to the concentration of specific metal ions, usually calcium and magnesium, in water that can form precipitates.
9. Conductivity: The ability of water to conduct electricity between two parallel electrodes one centimeter apart. It indirectly reflects dissolved salt concentration.
10. Resistivity: An indicator of water’s resistance to conducting electricity, typically measured in MΩ·cm. Resistivity is the inverse of conductivity. For example, if water conductivity is 0.2 µS/cm, its resistivity is 5 MΩ·cm.
11. TDS (Total Dissolved Solids): The concentration of dissolved inorganic substances remaining after filtration and evaporation, measured in ppm or mg/L. TDS correlates roughly with conductivity (e.g., 1 ppm TDS corresponds to approximately 2 µS/cm conductivity for sodium chloride).
12. pH Value: The measure of acidity or alkalinity in water, defined as the negative logarithm of the hydrogen ion concentration. A pH of 7.0 is neutral; below 7.0 is acidic, and above 7.0 is alkaline.
13. Alkalinity: The concentration of substances in water that can neutralize hydrogen ions, mainly from carbonate, bicarbonate, and hydroxide ions.
14. SDI (Silt Density Index): A metric indicating the level of suspended solids in feed water used in reverse osmosis systems.
15. Ozone: An unstable, highly reactive form of oxygen produced naturally by lightning or by high-voltage electricity, often used as an oxidant and disinfectant.
16. Residual Chlorine: The remaining effective chlorine in water after disinfection over a certain period.
17. Total Coliform Count: A measure of coliform bacteria, including aerobic and facultative anaerobic, Gram-negative, non-spore-forming rods that ferment lactose at 37°C within 24 hours, producing acid and gas. The count is expressed as the number of coliforms per liter of water.
18. Recovery Rate: The ratio of the flow of product water to the flow of feed water in a system.
19. Salt Rejection Rate: An indicator of membrane performance, typically over 97% for a single-pass RO membrane. Calculated as: (feed water conductivity – product water conductivity) / feed water conductivity.
20. Salinity: Also known as mineralization, salinity reflects the total amount of dissolved salts in water, measured as the sum of all cations and anions present.
21. Sedimentation: Sedimentation is a wastewater treatment method that involves physical and chemical processes. Physical sedimentation, the most common form, uses gravity to separate suspended solids from water. This occurs because the suspended particles have a different density than water, causing them to settle or float. Chemical sedimentation involves adding chemicals to wastewater, which react with dissolved substances to form insoluble compounds that precipitate out.
22. Treated Water: Treated water, also known as “reclaimed water” or “recycled water,” refers to wastewater that has been processed to meet specific quality standards for non-potable uses. It falls between potable water and untreated wastewater in terms of quality. Reclaimed water can be used for irrigation, industrial processes, or cooling, but is not suitable for drinking.
23. Organic Pollution: Organic pollution refers to natural organic substances like carbohydrates, proteins, amino acids, and fats, as well as certain biodegradable synthetic organic compounds. It primarily originates from domestic wastewater and industrial effluents.
24. Concentration Polarization: Concentration polarization occurs during reverse osmosis when salt concentrates on the membrane surface, creating a concentration gradient. If the flow rate is low, the high salt concentration at the membrane surface hinders diffusion, affecting system efficiency.
25. Suspended Solids (SS): Suspended solids refer to solid particles, including inorganic and organic materials, silt, clay, and microorganisms, suspended in water. The concentration of suspended solids is an indicator of water pollution and is measured by drying the residue left on a filter paper at temperatures between 103-105°C. The unit is mg/L.
26. Aeration: Aeration is the process of transferring oxygen (O2) from the air into water to support microbial activity. It is essential for providing dissolved oxygen to microorganisms, such as activated sludge, to facilitate their metabolic processes.
27. Biochemical Oxygen Demand (BOD): BOD refers to the amount of dissolved oxygen consumed by microorganisms to decompose organic matter in water under specific conditions. It is commonly measured over five days at 20°C (BOD5), and is expressed in mg/L.
28. Chemical Oxygen Demand (COD): COD measures the amount of oxygen required to oxidize organic compounds in wastewater using a strong oxidant under controlled conditions. Potassium dichromate is typically used as the oxidizing agent, and the result is expressed in mg/L.
29. Water Hammer: Water hammer, also known as hydraulic shock, occurs when there is a sudden change in water flow, such as when a valve closes abruptly or a pump stops suddenly. This causes a rapid pressure fluctuation, which can damage pipes and equipment.
30. Adsorption: Adsorption is a process where pollutants are removed from wastewater by a porous solid material. The pollutants are attracted and held on the surface of the adsorbent, effectively purifying the water.
31. Enzymes: Enzymes are biological catalysts produced by living organisms. Composed mainly of proteins, enzymes accelerate biochemical reactions, playing a critical role in biological processes.
32. Wastewater: Wastewater refers to water that has been contaminated by human activity, including domestic, industrial, and agricultural waste. It is water that has been used and is no longer suitable for its original purpose.
33. Wastewater Treatment: Wastewater treatment involves using various methods and technologies to remove pollutants from wastewater, making it suitable for discharge or reuse. The goal is to separate contaminants, recycle usable materials, or convert them into non-harmful substances.
34. Wastewater Reuse: Wastewater reuse refers to the process of treating wastewater to a standard that allows it to be used again in industrial or domestic applications, such as irrigation, cooling, or non-potable purposes. This is also known as water reclamation.
35. Scale: Scale forms when water quality is poor, causing solid deposits to form on heat exchange surfaces over time. It occurs when dissolved minerals in the water precipitate out and adhere to surfaces, affecting equipment efficiency.
36. Sludge: Sludge consists of solid particles suspended or settled in water, such as sediment or residue from chemical processes. It forms during water treatment processes and needs proper disposal or further treatment to prevent environmental impact.
37. Iron, Manganese, and Aluminum: Small amounts of iron, manganese, and aluminum can cause discoloration, scaling, and odor in water. Iron, in its reduced form, is soluble in water but oxidizes upon contact with air, forming insoluble particles that can clog membranes and cause scaling.
38. Purified Water: Purified water is water that has undergone filtration to remove contaminants, including salts and weak electrolytes like silica and carbon dioxide. The total dissolved solids (TDS) content is typically below 1.0 mg/L, and the conductivity is less than 3 µS/cm.
39. Ultrapure Water: Ultrapure water is water that has nearly all dissolved solids and impurities removed, including colloids, gases, organic materials, and ions. It is used in high-precision industries like semiconductor manufacturing. The TDS is less than 0.1 mg/L, and the conductivity is less than 0.1 µS/cm.
40. Distilled Water: Distilled water is produced by heating water to create steam, then condensing the steam back into liquid form. Distilled water typically has a conductivity of around 10 µS/cm. Re-distilled water, obtained through multiple distillations, can have a conductivity as low as 1 µS/cm.
41. Scale Inhibitor: A scale inhibitor is a chemical agent that disperses insoluble inorganic salts in water, preventing or disrupting the precipitation and scaling of these salts on metal surfaces. It helps maintain the heat transfer efficiency of metal equipment by reducing scale formation.
42. Ion Exchange Resin: Ion exchange resins are insoluble, high-molecular-weight polymers with functional groups capable of exchanging ions. Typically in spherical form, these resins facilitate the exchange of ions between water and the resin, making them effective in water treatment processes.
43. Ion: An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a charged particle. This process, known as ionization, occurs when atoms achieve a stable electron configuration, typically with 8 electrons in their outer shell (or 2 for helium). Ions are classified as cations (positively charged) or anions (negatively charged), and they combine to form neutral compounds, like sodium chloride, composed of sodium and chloride ions.
44. Water Production Rate: Water production rate, or flux, refers to the amount of water that passes through a reverse osmosis membrane per unit of time. It is typically expressed in tons per hour (t/h) or gallons per day (g/d).
45. Electrodeionization (EDI): Electrodeionization (EDI) is an advanced water purification technology developed in the 1990s, combining electrodialysis and ion exchange techniques. EDI uses ion-exchange membranes to selectively transport ions, and ion exchange resins to further remove ions under the influence of a direct current (DC) electric field. This process effectively produces ultra-pure water by removing dissolved salts and regenerating the resin without the need for acid or alkaline chemicals.

Explanation of the Basic Process of Pure Water Treatment

➣Coarse Filtration

Coarse filtration refers to mechanical filtration designed to remove suspended solids, colloids, turbidity, color, and odors from water. Common methods include clarification tanks, rapid sand filters, multi-media filters, activated carbon filters, disc filters, and high-efficiency fiber filters.

➣Fine Filtration

Fine filtration uses specialized filter membranes with higher precision. Common types include microfiltration membranes and filter cartridges.

➣Ultrafiltration

Ultrafiltration is a membrane filtration process that removes large molecules, colloids, bacteria, and other contaminants. It is highly effective at filtering out particles, but it does not remove ions from water, making it unsuitable for desalination. 

Ultrafiltration is typically used as a pre-treatment for reverse osmosis or for post-treatment in some systems. It operates using tangential flow and pressure-driven filtration, separating particles based on molecular size. 

The pore size of ultrafiltration membranes ranges from 0.002 to 0.1 microns. It removes colloids, suspended solids, macromolecular organic compounds, bacteria, viruses, and protozoa, while allowing smaller molecules and dissolved substances to pass through.

➣Reverse Osmosis (RO)

Reverse Osmosis (RO) is a membrane separation technology developed in the 1960s. It operates by applying high pressure to raw water, forcing it through a semi-permeable membrane, which separates the solvent from solutes, with water moving from a high concentration to a low concentration. 

RO removes bacteria, viruses, colloids, organic compounds, and over 98% of dissolved salts. It is known for its low operating costs, ease of operation, high automation, and stable water quality. Compared to other water treatment methods, RO offers several distinct advantages and is widely used across various industries.

Key Benefits of RO:

• Operates at room temperature using a physical method without phase changes to desalinate and purify water.
• The latest ultra-thin composite membranes can achieve desalination rates over 99.5% and also remove colloids, organic compounds, bacteria, and viruses.
• Water treatment relies on pressure, making it one of the most energy-efficient methods.
• Does not require large amounts of chemicals or acid/base regeneration treatments, resulting in no chemical waste discharge or environmental pollution.
• RO systems can operate continuously, are simple to maintain, and provide stable product water quality.
• High automation reduces operational labor and maintenance efforts.
• Space-efficient with a small footprint.
• Versatile in handling various water qualities, including brackish water, seawater, and low-salinity fresh water.

➣Ion Exchange

Ion exchange involves the replacement of ions in water with those from ion-exchange resins. In the cation exchange process, cations in the water are replaced by hydrogen ions, while in the anion exchange process, anions are replaced by hydroxide ions. 

A mixed-bed ion exchange system combines cation and anion resins in the same column, offering superior water quality compared to separate cation and anion beds. The mixed-bed system produces high-purity water by immediately neutralizing exchanged ions, resulting in very low conductivity and extremely pure water.

➣Electrodeionization (EDI)

EDI is an advanced water treatment technology that combines electrodialysis and ion exchange to achieve deionization without the use of chemicals for regeneration. The system utilizes electric fields to drive ion migration through ion-exchange membranes, continuously producing high-purity water. EDI has the following advantages:

• It can continuously produce ultrapure water meeting specific quality standards.
• No chemical regeneration is required, making it environmentally friendly with no chemical waste.
• Compact design, requiring less space, with low operational and maintenance costs.
• EDI systems are pre-commissioned before shipment, making installation and startup easy.
• Operation is simple with low labor intensity and minimal training requirements.

Manufacturers of Common Water Treatment Membranes

-Ultrafiltration (UF) Membranes

• KOCH (USA)
• Norit (Netherlands)
• Shanghai Huaneng Membrane (China)

-Reverse Osmosis (RO) Membranes

• Hydranautics (USA)
• Dow (USA)
• KOCH (USA)
• General Electric (GE) (USA)
• Toray (Japan)
• Sepro (South Korea)

-Electrodeionization (EDI)

• General Electric (GE) – E-CELL (USA)
• IONPURE (USA)
• Electropure (USA)
• CANPURE (Canada)
• Zhejiang Dongda (China)

NEWater, as a professional manufacturer, supplier, and solutions provider for water treatment equipment, is committed to ensuring the quality of our products and maintaining a strong reputation in the industry. We collaborate with internationally renowned brands to further enhance our offerings.

With our own manufacturing advantages, coupled with China’s strong position as a leading manufacturing hub, we are able to provide not only top-tier membranes from well-known global suppliers but also high-quality, cost-effective membrane accessories made in China. For more information and pricing inquiries, feel free to contact us.

Common Water Treatment Processes

💧Groundwater as Raw Water

Sand Filter + Precision Filter + Reverse Osmosis (RO) + Mixed Bed or EDI

💧Municipal Tap Water as Raw Water

Sand Filter + Activated Carbon Filter + Precision Filter + RO + Mixed Bed or EDI

💧Surface Water as Raw Water

• Option 1: Multi-media Filter + Activated Carbon Filter + Precision Filter + RO + Mixed Bed or EDI
• Option 2: Multi-media Filter (or other filtration methods) + Ultrafiltration + Precision Filter + RO + Mixed Bed or EDI
• Option 3: Disc Filter + Ultrafiltration + Precision Filter + RO + Mixed Bed or EDI