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Difference between home & council sewage treatment system

Residential vs Council Sewage Treatment System

Wastewater is treated either in council-operated wastewater treatment plants or home sewerage treatment plants. So, what’s the difference between the two?

In this article, we will discuss the home and council sewage treatment systems and the differences between the two.

Wastewater from households should be treated in a way that:

  • The drinking water supply is not affected
  • Direct human exposure is not possible
  • Wastewater is not accessible to rodents, insects and other disease carriers.
  • Environmental laws and regulations are met.

Home Sewage Treatment Systems

Properties not connected to the council sewage treatment systems treat and dispose of their wastewater using onsite sewerage treatment systems.

Types of home/onsite sewerage treatment systems

  • Septic Systems
  • Composting Systems
  • Holding Tanks
  • Domestic sewage treatment plants like:
  1. Activated sludge system
  2. Aerated Sand Filter System
  3. Biological Trickle Filter System
  4. Aerated Wastewater Treatment System

How do home sewage treatment systems work?

  1. The waste from the household is collected in the septic tank/chamber of the domestic sewage treatment plant.
  2. The solid waste in the water settles down as sludge and oils and lighter materials settle on the top layer as scum. This process of sedimentation works to filter out large contaminants.
  3. The wastewater is treated by microbes in the presence of oxygen (aerobic digestion) or the absence of oxygen (anaerobic digestion).
  4. Once the effluent has passed through the treatment system it is distributed in the soil using either absorption trenches, evapotranspiration absorption beds, mound systems, and surface or subsurface irrigation.
  5. The effluent can be further treated inside the system using the processes of aeration and disinfection via UV rays.
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Council Sewage Treatment Systems

The sewage treatment plants are maintained by the government and treat the wastewater collected from households.

  1. The waste from sinks, drains, and toilets goes down the sewer drain.
  2. Waste collected from households is known as sewage and flows through sewerage pipes.
  3. The pipes drain this waste to sewage treatment plants wherein it is treated in 3 stages  - primary, secondary and tertiary.
  4. Biological and physical processes are used to kill the germs in the water after which, the treated water is released into our waterways.
  5. Primary Treatment methods involve the process of sedimentation wherein the solid particles settle at the bottom of the large tanks. The heavy particles form a layer of sludge and lighter particles settle at the top forming a layer of scum.
  6. Sludge is treated further by a process called sludge digestion.
  7. In sludge digestion, bacteria are used to break down the sludge. Sludge digestion can lead to the formation of methane gas which can be utilised to generate electricity. Or it can be heated, incinerated and reused as fertilizer.
  8. In secondary treatment, waste is broken down by bacteria in the presence of oxygen.
  9. In tertiary treatment, the toxic particles are removed and the treated water is stored in lagoons to remove the remaining nutrients.
  10. When tertiary treatment is used the water can be safely released into natural waterways like the ocean, rivers, or estuaries.
  11. Prior to release the water is checked to ensure it doesn’t contain anything harmful which could destroy the flora and fauna in the area. The water quality is quite high and shouldn’t cause water pollution or affect the health of the local population.

Clean Ocean Foundation and Marine Biodiversity Hub have produced a National Outfall Database to monitor the quality of outfalls effluent throughout Australia. Wastewater discharged into natural waterways can pollute the water bodies if it is partially treated or if there are overflows from the sewage system.

According to the National Outfall Database, Queensland has 40 Estuary and River Outfalls and 14 Ocean Outfalls.

What's the difference between home and council sewage treatment plants?

  1. Domestic sewage plants need to be installed by licensed contractors who evaluate the site for its suitability. The selection of an appropriate wastewater treatment plant depends on factors such as the layout of the site, soil quality, and more. All domestic wastewater treatment systems must be approved by the local council. Local governments are responsible to build, maintain and operate council sewage treatment plants.
  2. The domestic treatment plant handles the wastewater from a single property (usually in unsewered areas) whereas the council sewage plants clean the wastewater of the entire region.
  3. The home sewage treatment plants can handle limited loads whereas the council sewage treatment plants are designed to handle the heavy loads of sewage associated with large populations.
  4. The maintenance of home treatment plants is the responsibility of the property owner. The operators of Council Sewage Treatment Plans are regulated by the Environmental Protection Act 1994. They need to adhere to the local laws and discharge treated water (to the waterways) at an acceptable standard. The Department of Natural Resources advises local governments about managing and operating sewage treatment plants.

References

  • https://environment.des.qld.gov.au/management/water/pollution/wastewater
  • https://www.cleanocean.org/national-outfall-database.html
  • https://blog.csiro.au/australias-pristine-beaches-have-a-poo-problem/
  • https://www.waternsw.com.au/__data/assets/pdf_file/0003/58251/Designing-and-Installing-On-Site-Wastewater-Systems-WaterNSW-CRP-2019.pdf
  • Wastewater and Sewage Treatment
  • https://www.waternsw.com.au/water-quality/catchment/living/wastewater/how