A domestic sewage treatment plant is a self-contained system that processes wastewater from a single household or small community to remove contaminants and pollutants before discharging the treated water back into the environment.

A Domestic sewage treatment plant is a smaller and simpler version of a larger sewage treatment plant. It uses similar physical, chemical, and biological processes to treat wastewater and remove contaminants before the treated water gets discharged into the environment. Here are some of the basics of a typical domestic sewage treatment plant:

Inlet screening: The first stage of treatment involves removing large objects and debris from the raw sewage by passing it through a screen or filter.
Primary treatment: During immediate treatment, the wastewater can settle in a tank, and solids settle to the bottom to form sludge. Eventually, the clarified water will then move for further treatment.

Secondary treatment: In the secondary treatment stage, biological processes are used to break down and remove organic matter and other pollutants. It will process through an aeration chamber, which involves adding air and microorganisms to the wastewater to encourage the growth of bacteria that break down pollutants.
Tertiary treatment: Tertiary treatment is the final stage of treatment that involves additional processes to remove nutrients, such as nitrogen and phosphorus, and other residual contaminants from the water. It will also include the use of chemical treatments, filtration, and disinfection.
Disinfection: Once the water has been treated, it is disinfected to kill any remaining bacteria and pathogens before discharging it into the environment. Usually, chemicals like chlorine or other substances are used, or alternative techniques like ultraviolet radiation.
Sludge handling: In most cases, the sludge that is extracted during primary treatment is treated separately and can either be applied to the land or processed further to create biosolids that can be utilised as fertiliser.

How to Maintain a Sewage Treatment Plant?

Maintaining a sewage treatment plant is crucial to ensure its efficient and reliable operation. Additionally, here are some steps and practices for maintaining a sewage treatment plant:

Regular Inspections: Conduct routine inspections of the treatment plant to identify any signs of damage, leaks, or equipment malfunctions. It also includes checking pumps, motors, valves, pipes, and other components.
Preventive Maintenance: Implement a preventive maintenance program that includes regular servicing and cleaning of equipment. It helps prevent breakdowns and extends the lifespan of the plant. Follow manufacturer recommendations for maintenance intervals and procedures.
Monitoring and Testing: Continuously monitor the plant's performance by regularly testing influent and effluent samples. It helps identify deviations from desired parameters and allows for timely adjustments or troubleshooting.
Sludge Management: Proper management of sludge is essential. Regularly remove accumulated sludge from settling tanks, digesters, and other treatment units to maintain efficiency. Hence, consider implementing a sludge dewatering system to reduce volume and facilitate disposal.
Grease Trap Maintenance: If the plant receives wastewater from restaurants or food establishments, ensure that grease traps are installed and maintained properly. Therefore, regularly clean and empty grease traps to prevent blockages and maintain the flow of wastewater.
Odour Control: Implement measures to control odours generated by the treatment process. This may include installing odour control systems such as activated carbon filters or chemical dosing systems. Regularly inspect and maintain these systems to ensure their effectiveness.
Staff Training: Provide training & education to the plant operators and maintenance personnel. Ensure they are knowledgeable about the plant's processes, safety procedures, and maintenance requirements. Also, they regularly update their skills to keep up with advancements in wastewater treatment technology.
Document and Record-Keeping: Maintain detailed records of maintenance activities, inspections, repairs, and any operational issues. This documentation helps track the plant's performance, identify recurring problems, and plan future maintenance activities.
Compliance with Regulations: Stay updated with local regulations and environmental standards for wastewater treatment. Ensure the plant meets all necessary permits and requirements. Moreover, regularly monitor and report the plant's compliance with regulatory agencies.
Emergency Preparedness: Develop an emergency response plan that outlines procedures for handling equipment failures, power outages, or other unforeseen incidents. Hence, conduct regular drills and train staff on emergency protocols.

Troubleshooting Common Issues with Sewage Treatment Plants

Domestic Sewage treatment plants can encounter various issues that may affect their performance and efficiency. So, here are some common problems that can occur in sewage treatment plants and potential troubleshooting steps:

High Influent Flow or Hydraulic Overload:

Check for any inflow and infiltration sources like leaks in pipes or manholes.
Hence, evaluate the capacity of the plant and compare it to the actual flow rate.
Always consider implementing flow equalization or diversion systems to handle peak flow periods.

Low Influent Flow or Organic Overload:

Inspect influent pumps and ensure they are functioning properly.
Also, check for any blockages or clogging in the influent lines.
Assess the organic load and consider adjusting the feed rate or dosing of chemicals accordingly.

Excessive Foam or Scum Formation:

Inspect and clean scum collectors or skimmers in the clarifiers.
Adjust the chemical dosing for foam control, such as anti-foaming agents.
Check for high levels of fats, oils, and grease in the influent and implement effective grease trap maintenance if necessary.

Sludge Settling Issues:

Monitor the sludge blanket depth in clarifiers and adjust the sludge withdrawal rate accordingly.
Check the sludge density and consider optimizing the polymer dosage for better settling.
Assess the aeration system in activated sludge processes to ensure proper mixing and settling conditions.

Odour Problems:

Inspect and maintain odour control systems such as activated carbon filters or chemical dosing systems.
Check for any potential sources of odour, such as sludge handling areas or anaerobic zones, and implement appropriate measures for containment or treatment.
Review the ventilation system and ensure proper air circulation within the plant.

Equipment Failures:

Regularly inspect and maintain all equipment, including pumps, motors, blowers, valves, and instrumentation.
Follow manufacturer guidelines for maintenance and operating equipment within design specifications.
Keep spare parts on hand for critical equipment to minimise downtime in case of failures.

How Much Does a Domestic Sewage Treatment Plant Cost?

The cost of a domestic sewage treatment plant can vary widely depending on various factors such as its capacity, location, technology used, and local regulations. The size of the plant is usually determined by the population it needs to serve or the volume of wastewater it needs to treat. On average, a basic domestic sewage treatment plant can cost between $5,000 and $15,000. These systems typically use simple technologies such as septic tanks or aerobic treatment units (ATUs) and are suitable for smaller households.

For more advanced domestic sewage treatment plants that employ technologies like extended aeration or membrane bioreactors, the cost can range from $10,000 to $30,000 or more. Innovative industrial effluent techniques aid in maintaining increasingly valuable standard resources. Moreover, these systems offer higher treatment efficiency & are preferred in areas with stricter environmental regulations.