Water treatment
Water treatment
1. Definition and Purpose
Water treatment is a process that uses physical, chemical, biological or other methods to purify, soften, disinfect water quality or remove harmful substances, so that it meets specific water use standards such as drinking water, industrial water, wastewater treatment and reuse, etc.
2. Main Treatment Methods
Physical Treatment Methods
Sedimentation and Filtration: Large particles of impurities are removed by gravity, or suspended matter and some organic matter are removed by sand filtration or activated carbon adsorption. For example, water plants use quartz sand filters to remove turbidity.
Membrane Separation Technologies: Technologies such as reverse osmosis (RO), ultrafiltration (UF), and microfiltration (MF) utilize semipermeable membranes to intercept bacteria, viruses, and heavy metal ions. They are commonly used in pure water production and wastewater treatment and reuse.
Chemical Treatment Methods
Coagulation and Flocculation: The addition of coagulants (e.g., polyaluminum chloride) causes small particles to aggregate into large flocs, facilitating their removal by sedimentation. They are commonly used for surface water purification.
Disinfection: The addition of chlorine, ozone, ultraviolet light, and other agents kills microorganisms in water to ensure drinking water safety. For example, water plants use liquid chlorine for disinfection, and swimming pools often use sodium hypochlorite.
Neutralization and Redox: Adjusting the pH of water (e.g., using lime to neutralize acidic wastewater) or using oxidants (e.g., potassium permanganate) to decompose organic matter and heavy metals.
Biological Treatment:
Activated sludge: Utilizes microbial communities to degrade organic matter in wastewater and is the core process of municipal wastewater treatment plants.
Biofilm: Microorganisms attach to the surface of media to form a biofilm, removing pollutants through adsorption and metabolism, as in biofilters and biological contact oxidation tanks.
3. Application Scenarios
Drinking Water Treatment: Removes suspended solids, colloids, microorganisms, and harmful ions from natural water to meet the "Standard for Drinking Water Quality" (GB 5749).
Industrial Water Treatment: For example, boiler water requires softening and desalination to prevent scaling, while the electronics industry requires ultrapure water (removing nearly all ions and organic matter).
Wastewater Treatment and Reuse: Treats domestic and industrial wastewater to meet standards for discharge or reuse. For example, treated municipal wastewater can be used for landscaping and toilet flushing.
4. Main detection indicators and instrument types
| Detection indicators | Typical instruments | Detection principle | Application scenarios |
| Physical indicators | |||
| Turbidity | Turbidity meter | Light scattering method | Drinking water and monitoring of influent water at sewage treatment plants |
| Temperature, conductivity | Multi-parameter water quality detector | Monitoring of hardness in industrial water and boiler water | |
| Chemical indicators | |||
| pH value | pH meter | Glass electrode method: | Control of neutralization process in wastewater treatment |
| Dissolved Oxygen (DO) | Dissolved oxygen analyzer | Electrochemical method: | Ecological monitoring of surface water, aeration control in wastewater treatment |
| Chemical Oxygen Demand (COD) | COD rapid tester | UVsense | Monitoring of pollutant concentration in industrial wastewater |
| Ammonia Nitrogen (NH₃-N) | Ammonia nitrogen detector | ion-selective electrode method | Monitoring of eutrophication of domestic sewage and surface water |
Case Studies
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