The disinfection process in urban water treatment plants aims to inactivate pathogenic microorganisms in the water (such as bacteria, viruses, and parasites) through physical or chemical methods. This ensures that drinking water meets health standards and prevents the spread of waterborne infectious diseases. Disinfection not only directly kills harmful microorganisms in the water but also maintains a certain residual amount of disinfectant (such as residual chlorine) in the water supply network to inhibit the regrowth of microorganisms and ensure the safety of water quality from the treatment plant to the user's end.
Process Flow Example
Urban Water Supply Treatment Process Flow Description
(1) Raw Water Intake and Pre-treatment
Raw water: sourced from surface water (rivers, lakes, reservoirs) or groundwater.
Pre-treatment:
Pre-chlorination (Pre-chlorine addition): A small amount of chlorine (Cl2 or sodium hypochlorite) is added to inhibit the growth of algae and microorganisms, reducing the load on subsequent processes.
Pre-ozone (Pre-ozone addition): Ozone (O3) is added to oxidize and decompose organic matter, remove color and taste, and enhance coagulation effects.
(2) Coagulation - Sedimentation - Filtration
Coagulation: Coagulants (such as PAC, aluminum sulfate) are added to destabilize colloidal particles.
Sedimentation: Flocs are removed in sedimentation tanks (such as horizontal flow tanks, lamellar tanks).
Filtration: Suspended solids and some microorganisms are further removed through sand filters or activated carbon filters.
(3) Advanced Oxidation Treatment
Primary ozone oxidation (Post-ozone): O3 is added in the ozone contact tank to efficiently degrade refractory organic substances such as pesticides and antibiotics and inactivate viruses. This is usually accompanied by a biological activated carbon (BAC) filter to utilize microorganisms to degrade ozone by-products (such as small molecular organic substances).
UV/H2O2 advanced oxidation: Ultraviolet light (UV) activates H2O2 to generate hydroxyl radicals (·OH), oxidizing pollutants non-selectively. This is suitable for the removal of trace pollutants (such as 2-methylisoborneol, geosmin, etc.).
UV/O3 advanced oxidation: UV and O3 work synergistically to generate ·OH, with higher oxidation efficiency than ozone alone. This is suitable for the removal of trace pollutants (such as 2-methylisoborneol, geosmin, etc.).
(4) Disinfection (Post-chlorination)
Chlorine disinfection: Liquid chlorine or sodium hypochlorite is added to ensure a residual chlorine level of 0.05∼0.3mg/L at the end of the distribution network, preventing secondary pollution.
(5) Clear Water Tank and Water Supply
Clear water tank: Stores disinfected water to regulate water supply flow.
Secondary chlorination: Chlorine is added before leaving the plant to ensure the residual chlorine level in the distribution network meets the standard.
Distribution network: Water is supplied to users, with continuous monitoring of residual chlorine and microbial indicators during this period.
Core Technologies
Ozone Generation System
A unique plate-type structure design with a discharge gap of ≤0.2mm helps increase ozone yield and concentration. The ozone energy consumption is ≤5.5kw·h/kgO3, and the ozone concentration is ≥350g/Nm3. Pre-ozone can control the formation of disinfection by-products and partially degrade natural organic matter and non-viable pathogenic microorganisms. Post-ozone, combined with UV advanced oxidation, can effectively inactivate pathogenic protozoa such as Cryptosporidium and Giardia, which are not easily inactivated by chlorine.
UV Disinfection and Sterilization Technology
High-efficiency high-intensity low-pressure (medium-pressure) UV lamps are used, along with high-performance electronic ballast technology. This technology is highly integrated and automated, suitable for UV disinfection in municipal sewage, drinking water, reclaimed water, and oilfield reinjection water, as well as advanced oxidation processes combined with O3 and H2O2. It can effectively remove trace pollutants in urban drinking water (such as 2-methylisoborneol, geosmin, etc.).
Sodium Hypochlorite Generation System
High-efficiency electrolysis technology reduces operating costs and increases current efficiency (≥85%). An intelligent frequency converter power supply is used, saving 10% to 15% energy compared to fixed-power machines. The optimized electrolysis cell flow channel structure ensures a saltwater utilization rate of ≥95%, and the production cost of sodium hypochlorite per ton of water is 0.2 to 0.3 yuan lower than the industry average. Intelligent control ensures precise dosing, real-time monitoring of residual chlorine, pH, and flow, and automatic adjustment of dosing amounts. No chlorine gas by-products are produced, and compared to chlorine gas disinfection, no carcinogenic substances such as trihalomethanes (THMs) are generated, meeting the GB 5749-2022 drinking water standard.
Chlorine gas disinfection alternative: Suitable for small and medium-sized water treatment plants (10,000 to 200,000 tons/day), avoiding the safety management challenges of chlorine gas. Pre-chlorination (sodium hypochlorite) + post-ozone: Inhibits algae growth while reducing disinfection by-products. UV/sodium hypochlorite combined disinfection: UV light activates sodium hypochlorite, enhancing disinfection efficiency (especially against chlorine-resistant pathogens).
