Overview of Disinfection Methods

Greendex provides the expertise for design and built of disinfection system from small to large scale installation. We have installation references ranging from municipal drinking water treatment plants to sewerage treatment plants, rubber glove industries, petrochemical, aquaculture, swimming pools and etc. 


Chlorination is a common method to disinfect water by using chlorine to kill germs and prevent diseases, making water safe to drink. De Nora's chlorination systems are trusted worldwide for their high quality and reliability.


Electro-chlorination creates a mild disinfectant on-site, which is safer and easier to handle than chlorine gas. De Nora ClorTec® systems, with over 3000 installations, make this solution using just salt, water, and electricity.

Ultraviolet System

Ultraviolet (UV) disinfection uses light to kill germs in water without chemicals. Its effectiveness depends on how long the germs are exposed to UV light and other factors like water clarity and UV source strength.

Chlorine Dioxide

Chlorine Dioxide is a powerful disinfectant that works well against tough germs like cryptosporidium and doesn’t react with ammonia. De Nora's systems produce it efficiently, making it great for treating drinking water.

Ozone System

De Nora Ozone, with over 45 years of experience, uses ozone to treat water, removing pollutants and killing bacteria, viruses, and other germs. It also helps improve water taste and smell by reducing harmful substances.
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RAPID Pangerang, Johor

Sg Dua WTP, Penang

Chlorination is one of the most prevalent methods of water disinfection. Chlorine can be applied in different processes to destroy target organisms and prevent the spread of diseases to make the drinking water fit for human consumption.

The complete line of De Nora gas feed disinfection technologies include Chlorination, De-Chlorination / Sulfonation, Ammoniation and Recarbonation equipment. With more than 50 years’ experience and many thousands of installations globally, our De Nora Capital Controls chlorination system sets the benchmark for the best quality chlorinators in the market. All the equipment manufactured are ISO 9001: 2000 certified. We have the highest presence in all municipal water treatment plants.


Providing water and wastewater treatment solutions for a sustainable future. Contact our Sales and Project Team today!​


Electro-chlorination or also termed On-site hypochlorite generation system is the production of a dilute form of disinfectant compared to chlorine gas or concentrated commercial hypochlorite. As a result, handling, transportation and containment are easier and safer.

De Nora ClorTec® have a strong reputation as the leading global technology provider with a proven track record of more than 3000 global installations. The ClorTec® systems generate a 0.8% sodium hypochlorite disinfection solution, a chlorine equivalent, using three common consumables: salt, water and electricity. The patented split flow design allows for the lowest operating cost in the industry.

Mengkubau WTP, Brunei

The Mengkubau Water Treatment Plant has been operational since year 2000. Under the upgrading project managed by the Ministry of Development through the Water Services of the Public Works Department in year 2015, about 40MLD of clean water has been supplied to 4,000 housing unit at the Kampong Panchor/Mengkubau National Housing Scheme in the Brunei Muara District.

The Electro-Chlorination system supplied and installed by Greendex in the Mengkubau Water Treatment Plant has demonstrated reliable and economic operation. Greendex also provides the customer with a tailored 2 years operation and maintenance regime to ensure optimum electro-chlorination plant performance.

Bertam WTP, Malacca

The Bertam DAF II water treatment plant has been operational since 2014.

The water authority is among the first in accepting the new disinfection technology among the states of Malaysia and the first to install the largest electro-chlorination system to date.

The system has been operating for more than 3 years and have proven success in terms of savings in operation cost in addition to being a safe disinfection system with reduced hazards.

The benefits of the on-site sodium hypochlorite generation systems include:

  • A proven, cost-effective, reliable and safe alternative disinfection treatment method
  • Eliminating the bulk storage of chemicals
  • Reducing risk to plant personnel because of drastically reduced hazardous material storage and handling requirements
  • Eliminating transportation liabilities
  • Reducing the threat to public safety
  • Reducing the production of disinfection byproducts
  • Creating a consistent solution concentration and increasing water quality
  • Reducing overall disinfection costs
  • Reducing the cost of pH adjustment

Greendex is the market leader and pioneer of Electro-chlorination system in S.E.A


Providing water and wastewater treatment solutions for a sustainable future. Contact our Sales and Project Team today!​

Ultraviolet System

Ultraviolet (UV) is chosen as the advance non-chemical disinfectant option for municipal water and wastewater treatment because it is a highly effective method of destroying microorganisms.

The effectiveness of germicidal UV in such an environment depends on a number of factors: the length of time a micro-organism is exposed to UV, power fluctuations of the UV source that impact the EM wavelength, the presence of particles that can protect the micro-organisms from UV, and a microorganism’s ability to withstand UV during its exposure.

Gadong stp, Brunei

Sentosa Cove, Singapore

Theory of UV Disinfection

DNA adsorbs UV energy between 250 and 265 nm

  • UV energy alters genetic structure of microorganism
  • UV energy stops the reproductive process
  • Microorganism is considered inactivated, non-infective or microbiologically dead

Greendex has the experience of supplying small UV installation for irrigation applications to large UV installation in sewerage treatment plants. Closed vessel and open channel types are both available.


Providing water and wastewater treatment solutions for a sustainable future. Contact our Sales and Project Team today!​

Chlorine Dioxide

Chlorine Dioxide is a very effective disinfectant against cryptosporidium and has no reaction with ammonia.

Our system produce chlorine dioxide and consistently maintain a product yield greater than 95%, making it ideal for drinking water treatment.

Chlorine Dioxide Generators


  1. ClO2 is 2.5 times more effective than CL2. A CT of 0.25 ppm @ 20 secs = 99.99% kill of all pathogens
  2. Dissolves easily in water
    • ClO2 gas remains dissolved in water
    • Generated on-site
    • No transportation of Chlorine gas
  3. ClO2 is a good oxidant for iron and manganese removal. It also improves sedimentation and lowers turbidity.

Providing water and wastewater treatment solutions for a sustainable future. Contact our Sales and Project Team today!​

Ozone System

With more than 45 years’ of dedication to solving some of the toughest problems and treating some of the most difficult pollutants such as hydrocarbons, surfactants and phenols, De Nora Ozone is one of the original pioneers of ozone treatment solutions for industrial applications.

Ozone can eliminate a wide variety of inorganic, organic and microbiological problems and taste and odor problems. The microbiological agents include bacteria, viruses, and protozoans. (such as Giardia and Cryptosporidium) In addition, the oxidizing properties can also reduce the concentration of iron, manganese, sulfur and reduce or eliminate taste and odor problems.

Singapore WTP

China WTP

Changsha WTP, China

  • Plant capacity: 500,000 m3/day
  • Ozone production: 4 generators with a capacity of 12 kg/h @ 10% each (total 48 kg/h)
  • Application: Municipal drinking water treatment

Changsha WTP, China

  • Plant capacity: 2,000,000 m3/day
  • Ozone production: 6 generators with a capacity of 26 kg/h @ 10% each (total 156 kg/h)
  • Application: Municipal drinking water treatment

Ozone offers a range of advantages:

  • No residuals creating biological sub-products
  • Quick reaction time
  • No chemical compounds required – generated by air or pure oxygen
  • Can be produced on-site as required
  • The strongest natural oxidants


Because of its excellent disinfection and oxidation qualities, ozone is widely used for drinking water treatment. At municipal plants ozone can be added at several points throughout the treatment system, such as during pre-oxidation, intermediate oxidation or final disinfection. Usually, it is recommended to use ozone for pre-oxidation, before sand filters or with active carbon filters (GAC).

Ozone is a very active form of oxygen. It is formed when oxygen is exposed to a high-energy field causing some oxygen molecules(O2) to break down to oxygen atoms(O). The oxygen atoms (O) then react with the oxygen molecules (O2) to form ozone (O3). Notice that this is a reversible reaction meaning that ozone can decompose back to oxygen.


Providing water and wastewater treatment solutions for a sustainable future. Contact our Sales and Project Team today!​

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