What does the disinfectant do in water waste treatment?

Disinfection is a critical process in both drinking water and wastewater treatment. The goal of adding disinfectants is to remove or inactivate disease-causing microorganisms, including bacteria, viruses, and protozoa parasites. By destroying or neutralizing these pathogens, disinfectants help prevent the spread of waterborne infectious diseases.

In wastewater treatment specifically, disinfection serves as a final polishing step before effluent (treated wastewater) is either discharged into the environment or reused. It’s applied after primary and secondary treatment methods have removed solids and reduced organic matter and nutrients.

In this post, as a professional water treatment supplier, I will share everything about the disinfectant in water waste treatment.

Why disinfection is so important

Raw sewage contains high concentrations of pathogenic microbes from human and animal waste. Diseases caused by contamination with these pathogens include:

• Cholera
• Typhoid
• Hepatitis A and E
• Polio
• Cryptosporidiosis
• Giardiasis

Without proper disinfection, discharging untreated sewage into waterways can spread these dangerous diseases to downstream communities. Treated but not disinfected wastewater still poses risks.

Disinfection provides a chemical or physical kill-step toinactive pathogens. By law, wastewater treatment plants must meet discharge limits onindicator organisms like fecal coliform bacteria and E. coli. These guidelines match up with how effective certain disinfectant doses are at reducing parasites, bacteria, and viruses.

Meeting this level of disinfection protects public health by preventing unnecessary exposure. Releasing inadequately treated sewage, especially into recreational waters or sources of drinking water, poses unacceptable risks.

How disinfectants work

There are a variety of disinfection methods used in wastewater treatment. The most common options include:

• Chlorine
• Ozone
• Ultraviolet light (UV)

While the mechanisms differ, all three essentially damage pathogens’ cell structures and prevent them from reproducing and infecting hosts.

Chlorine works by penetrating cell walls and destroying enzymes, structures, and other essential components. A residual can linger to continue working after initial application.

Ozone kills pathogens by rupturing their cell membranes through oxidation. As it reverts back to oxygen, ozone also raises the dissolved oxygen level in treated wastewater.

UV damges the molecular bonds in pathogens’ DNA and RNA. By altering their genetic coding, cell replication stops.

Factors like contact time, dosage, and water chemistry determine how effective disinfection is with these methods. Facilities choose approaches aligned with wastewater characteristics and treatment goals.

What does the disinfectant do in water waste treatment?

Now that we’ve covered why disinfection matters and how it works, let’s dive deeper into the disinfectant’s exact purpose in wastewater treatment.

The primary role of the disinfectant chemical or process used is to inactive pathogens right before treated effluent is discharged from the facility. This kill-step prevents dangerous organisms like bacteria, viruses, and parasites from entering the environment.

Discharging treated but not disinfected wastewater still carries public health risks. Pathogens can survive treatment steps like screening, sedimentation, and secondary biological processes. Without proper disinfection, these disease-causing organisms would flow straight into rivers, lakes, or coastal areas.

By destroying nearly all pathogens incapable of causing infection in downstream users, disinfection satisfies regulatory requirements for safe wastewater discharge. Other key responsibilities include:

Preventing transmission of disease

The degree of disinfection for wastewater is based on protecting public health. Ensuring strong log removals or inactivations of pathogens prevents treated sewage from amplifying disease when released.

Often, coliform targets act as indicators for the probable presence of pathogens. Making sure coliform counts hit certain thresholds means other more dangerous microbes have likely been eliminated too.

Allowing water reuse

If treatment plants want to recycle their effluent for non-potable uses like irrigation or industrial processes, extra disinfection is required first. Direct or indirect wastewater reuse relies on advanced oxidation and filtration to guarantee safety.

The same goes for effluent discharged into recreational waters used for fishing, boating, or swimming. Here pathogens pose a more direct contact risk, so extra care must be taken.

Improving ecosystem health

Discharging treated effluent with lower pathogen levels means less contamination entering our shared environment. This keeps wildlife and their habitats healthier across the board.

Certain chemicals like chlorine can negatively impact ecosystems when dosed improperly. But new alternatives like UV neutralize threats without secondary pollution risks if applied well.

Meeting regulatory permit obligations

Wastewater treatment plants must closely monitor and report on their disinfection efficacy. Operators need to verify that sufficient pathogen log removal or inactivation is achieved to satisfy their facility’s discharge permit requirements.

Method-specific dose targets (like 99% protozoa removal for UV) align with regulations on the total coliform, fecal coliform bacteria, and other pathogen levels set for that plant’s waterways. Routine sampling ensures these safety criteria are consistently achieved.

Putting it all together

On their own, preliminary and secondary treatment processes do not reduce pathogens enough to allow for safe discharge or reuse. The disinfectant delivers the final punch to eliminate nearly all remaining threats before water exits the plant.

Carefully designed and monitored disinfection prevents health hazards from treated sewage contamination. Harmful pathogens – already significantly reduced from earlier processing – get neutralized right as they would otherwise return to the environment.

The disinfectant in wastewater treatment stops dangerous microbes like bacteria, viruses, and parasites from spreading infectious diseases. It serves as the last line of defense for both ecological and public health.

Key takeaways

• Disinfection is required by law in wastewater treatment to prevent pathogens from entering water supplies
• Popular disinfection methods include chlorine, ozone, and UV light
• Each approach damages microbes to stop them from reproducing and infecting
• The main role of disinfectants is to complete the pathogen removal process right before treated effluent discharge

By requiring disinfection as a final safeguard, regulations ensure wastewater gets cleaned without posing unnecessary health risks from improper treatment.