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Coliform Treatment in Wastewater

What is coliform?

Coliform is a group of bacteria that live in the intestinal tracts of warm-blooded animals and humans. They are widely found in the environment and feces. The presence of coliform in water indicates that there has been contamination of animal or human feces. Therefore, treating coliform in wastewater is important to prevent the spread of infections.

Treatment of coliform in wastewater is urgent:

  • Contamination of water sources: The presence of coliform indicates that the water source has been contaminated by feces and pathogenic microorganisms. This increases the risk of waterborne disease transmission.
  • Diarrhea: Some coliform strains such as E. coli can cause diarrhea and vomiting in consumers if they use contaminated water.
  • Hepatitis: Coliform bacteria can cause acute or chronic hepatitis A in humans due to exposure to contaminated water.
  • Sediment pollution: Coliform in wastewater when discharged into rivers and lakes will be deposited to the bottom, polluting sediment and aquatic resources.
  • Aquatic habitat effects: The presence of coliform reduces dissolved oxygen in water, causing pollution and affecting the growth of aquatic life.
  • Air pollution: The stench from waste water containing coliform causes air pollution and an unpleasant odor.
  • Aesthetic influence of the living environment landscape.
Therefore, the thorough treatment of coliform in wastewater before discharge to the environment is extremely necessary to protect health and habitat. Modern treatment technologies are becoming more and more popular to help completely eliminate coliform and pathogens in wastewater.
Xử lý coliform trong nước thải

Methods for treating coliform in wastewater:

Chemical disinfection
Disinfection chemicals such as chlorine, ozone, or chloramine can be used to kill coliform bacteria in wastewater. These chemicals break down bacterial cell walls, killing them. This is a simple and effective method, often used as the final treatment step before discharging water into the environment.
UV sterilization
UV rays can destroy the DNA / RNA of bacteria, preventing them from multiplying. Wastewater is passed through UV light at a specific wave length and a certain dosage to kill bacteria. This is also an effective, convenient method.
Membrane filter
Membrane filtration processes such as reverse osmosis filtration, ultrafiltration can completely remove bacteria from wastewater. The vents on the membrane only allow water through, retaining bacteria and solids.
Treatment by electrochemical
Iron and aluminum electrodes can be used to generate hydrogen ions, strong disinfectants. The wastewater that passes through these electrodes will be disinfected. However, this method can produce toxic by-products so strict control is required.
Treatment with ozone
Ozone is a powerful disinfectant, which can effectively destroy bacterial cells. Ozone is generated from oxygen by electric discharge and then put into wastewater at certain dosage. After treatment, ozone needs to be converted into oxygen before discharging water into the environment.
Treatment with gamma rays or electron rays
Radioactivity can destroy the DNA / RNA of bacteria, causing them to lose their ability to multiply. This is a modern technology but requires special equipment and high cost.
Biological treatment
Biological treatment processes such as pond sedimentation, biofiltration, natural reactions can remove large amounts of coliform. Bacteria will be killed in harsh environments or eaten by other microorganisms. However, the efficiency is lower than that of disinfection methods.
Treatment by electrolysis
Electrolysis splits water into hydrogen ions, strong disinfecting oxygen can destroy coliform. However, the process requires a lot of energy and can produce toxic by products.
Coordinate multiple technologies
Often wastewater treatment plants will combine many technologies such as bioremediation, membrane filtration, chemical / UV disinfection to ensure complete removal of coliform before it is released into the environment.
Factors to consider when choosing a coliform treatment method include: treatment efficiency, investment and operation costs, technology complexity, feasibility, environmental impact. Local wastewater quality standards will also greatly influence the choice.

Coliform in wastewater standard

According to the Vietnam Standard for Wastewater Quality (TCVN), the regulations on coliform content in wastewater are as follows:
  • TCVN 7222-2002 – Water quality – Test and determination of coliform, Heat-resistant Coliform, E.Coli membrane analysis: Specify methods for sampling, identification and counting Coliform colonies, Heat-resistant coliform and E.Coli in water.
  • TCVN 5945-2005 – Water quality – General requirements for wastewater quality: The maximum allowable coliform content in domestic and industrial wastewater is 3000 MPN / 100ml.
  • QCVN 14: 2008 / BTNMT – National technical regulation on industrial wastewater: The maximum allowable coliform content in industrial wastewater is 5000 MPN/100ml.
  • TCVN 6772-2000 – Water quality – Requirement of coliform, E.Coli and Salmonella in wastewater for irrigation: Regulation of coliform content for membrane analysis up to 1000 MPN / 100ml.
  • QCVN 40: 2011 / BTNMT – Surface water quality regulation: Coliform content of membrane analysis does not exceed 2500 MPN / 100ml for water used for domestic water supply purposes.
Thus, depending on the purpose of using wastewater after treatment, there are specific regulations on the maximum coliform content in wastewater. Compliance with these standards is necessary to ensure wastewater quality and environmental protection.
Coliform control and treatment should be conducted regularly to ensure that wastewater is always up to standard before being discharged into the environment. Periodic coliform tests should also be performed to assess treatment efficiency.
In general, with the development of technology, the treatment and removal of coliform in wastewater is becoming easier and more efficient. It is important for wastewater treatment facilities to choose the right technology, operate and maintain the system well to ensure the supply of clean and safe water for the community.

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