Sewage Treatment

What is sewage?

All the water within our Region, once used, is referred to as sewage.  Sewage is 99.97% water as the majority of it comes from showers, baths and washing machines. The rest is dissolved and suspended matter.

Sewage comes from domestic, commercial and industrial sources.  The collection, treatment, disposal and reuse of sewage throughout our Region forms an integral part of the water cycle.

Where does our sewage go?

All of our used water that is flushed down the toilet or let go down the drain doesn't just disappear, it travels through our sewage system to a sewage treatment plant. 

It's important to remember that whatever goes down the drain must be taken out again. It's pretty amazing to see what gets poured down the drain or flushed down the toilet upon a closer look - medicines, food colouring and flavours, coffee grounds, personal care products, detergents, dyes, paints, plastics and even toys.

Our sewage treatment plant also has to deal with the chemicals and waste produced by agriculture and heavy industries.  Some of these materials can easily break down, but others don't degrade that easily.  Simple things like baby wipes are pretty good at blocking up sewers.  Many people are unaware that these types of things shouldn't be going down the toilet. "Flushable Wipes" may be flishable but they do not disintegrate and they have caused major blockage in sewers.

Everything we pour down the sink or flush down the toilet passes through the sewerage system and must be dealt with by pumps and treatment equipment.  Disposing of household waste in the correct manner can help overcome problems with the collection and treatment of sewage, and at the same time protect the environment.

How is sewage treated?

At the sewage treatment plant the sewage goes through a series of physical and iological processes that remove the pollutant materials from the water, such as solids, oils and greases, detergents, nutrients, heavy metals and bacteria.

Once the treatment process is over there are two end products - treated sewage and biosolids.  The treated wastewater is returned back to the environment.  Modern treatment processes can remove over 99.99% of contaminants from the water, and this treated water can be reused as irrigation on golf courses and sporting fields, or for industrial use.

Inflow and Infiltration into the Sewerage System

Stormwater can enter the sewerage system through crakced pipes, leaky manholes on public roads, low overflow relief gullies or improperly nd sometimes illegally onnected stormwater drains and downpipes on private properties.

The sewerage system is not designed to carry stormwater, and excess flow into the system can cause drains to back up and even overflow raw sewage, compromising public health and the environment.

The house drain from each property connects to a sewer pipe or sewer manhole. The sewer and sewer manholes are the Council's responsibility.

House drains are the responsibility of each property owner and they need to be maintained to ensure that stormwater and groundwater don't enter the sewerage system.  It is an offence for residents to drain any stormwater from their property into sewerage manholes or the sewerage system.

Sewerage Infrastructure

Residents may have a sewerage manhole inside their property.  From time to time Council requires access to the sewerage manhole for maintenance purposes.  Areas surrounding the manhole hould be kept clean and clear of any obstructions which would hinder access by Council employees or contractors.  Wherever possible, Council notifies the owner/occupier in advance of works required to be undertaken.

Charters Towers Regional Council will, from time to time, carry out inspections including smoke testing of the sewerage system, focusing on house drains, overflow relief gullies and plumbing within properties throughout Charters Towers connected to the sewer system.

Smoke testing involves the injection of a non-toxic smoke into sewers and house drains to identify how and where smoke escapes into the atmosphere. For example, smoke emitted from a downpipe during a smoke test will indicate an illegal stormwater connection.

Sewage Overflows

How to prevent this problem

Check your property for illegal stormwater connections to the sewer. Downpipes that are connected directly to the sewer create an excess load on the system, which it is not designed for. This can cause sewage to overflow into homes and the environment.

Check your overflow relief gully to reduce the risk of an overflow in your home.

What is an overflow relief gully (ORG)?

An ORG is a drain-like fitting located outside the home. Should the sewerage main or property service drain become blocked, sewage will discharge from the ORG outside, rather than from another point inside the home.

How does it work?

If the sewerage system becomes blocked causing the flow to back up, the loosely fitted grate on the top of the ORG is designed to pop off completely (if installed correctly) allowing the sewage to escape outside, rather than from another point inside your home.

Your ORG responsibilities

It is the home owner's responsibility to make sure their home is fitted with a properly designed and operational ORG. When an ORG is not functioning correctly the property damage and health risks associated with sewage spilling inside or under a property are greatly increased.

Check your ORG to ensure:

  • it is not covered by landscaping or garden beds;
  • it is not covered by bricks or pot plants;
  • the grate is able to pop off easily and isn't stuck due to corrosion, or permanently fixed in concrete;
  • it is not underneath the property as a result of not being moved when a house extension was built;
  • it is not blocked with concrete as a result of a driveway or paving construction; and,
  • your ORG has a clear drainage path (so spills drain away quickly without causing damage).

Septic Tank Maintenance

There are three components to a conventional septic tank system:

  • sanitary plumbing fixtures which include the toilet, kitchen sink, dishwasher, laundry trough, washing machine, shower, hand basin and any other unit connected to a drain that carries waste to the septic tank;
  • the septic tank; and,
  • the effluent disposal system.

The Septic Tank

A septic tank consists of a watertight receptacle, designed and constructed to receive sewage from plumbing fixtures in the building. Its main role is to separate different wastes through sedimentation, and it also provides digestion of the refined organic matter by bacterial activity.

Three distinct zones exist in the septic tank:

  • the sludge zone, where the heavier solid material settles on the bottom of the tank;
  • the scum zone, where the lighter residues of grease and soap float to the top of the tank; and
  • the detention zone, the middle layer containing mainly liquid.


The septic tank functions correctly when the contents are alkaline.  This can be achieved initially by mixing 5kg of hydrated lime (Calcium hydroxide) with sufficient water and flushing this slurry into the septic tank through the toilet pan. Lime treatment can be utilised at other times when acidic conditions occur inside the tank.
Note: avoid lime coming into contact with the skin and eyes, wear eye protection and rubber gloves when handling this material.

Offensive odours will also result from the use of strong chemical cleaning agents which will kill the bacteria inside the tank, and thus cause the system to malfunction.  Always use cleaning agents that are labelled as suitable for use with septic systems.

Maintenance Tips


  • Use only soapy water or biodegradable cleaners to clean toilet and sanitary fixtures;
  • Check sludge levels in the septic tank every two years;
  • Have excess sludge removed from the tank every 3 - 4 years (more often if a food waste disposal unit is connected to the system);
  • Use toilet paper that breaks down readily;
  • Restrict food scraps entering the system;
  • Minimise the amount of water entering the system.


  • Attempt to disinfect the septic tank after excess sludge has been removed;
  • Dispose of sanitary napkins, coffee grounds, tea leaves, cooking fats or oils, bones, disposable nappies or cigarette butts into the septic system;
  • Subject the system to hydraulic shocks, eg the simultaneous use of washing machines, dishwashers, baths and showers.


  • Using strong caustic alkalis, oils, acids, bleaches and disinfectants.

Prohibited Discharges

No person shall permit or cause any of the following discharges to enter a septic tank system:

  • stormwater, including roof and rainwater overflow and surface drainage waters;
  • back-flush waters from a swimming pool or water softener;
  • discharge/back-flush from a spa bath/pool in excess of 120 litres, unless the system has been specifically designed to accommodate such loading;
  • disposable napkins, clothing or plastic sheeting;
  • trade waste;
  • petrol or other flammable or explosive substance whether solid, liquid or gaseous; and
  • disinfectants or deodorants, antiseptic or germicide powders or liquids unless specified as being suitable for disposal into a septic tank.

Guidelines for the care of the sub-surface disposal system

Reduce the amount of water discharging into the system by:

  • spending less time in the shower;
  • using less water in the bath;
  • using a suds-saving/eco cycle on the washing machine;
  • minimising water use when washing hands and cleaning teeth;
  • installing dual flush systems in toilets;
  • minimising water usage in the kitchen, eg hand wash dishes instead of using a dishwasher;
  • avoiding the use of food waste disposal units; and 
  • ensuring leaking taps are repaired immediately.

Protect the sub-surface effluent disposal system from migrating surface and sub-surface waters by:

  • Diverting roof, tank overflow and storm waters to the street, water table or an area beyond the soakage system;
  • Avoiding washing cars or watering lawns or gardens adjacent to or above the disposal system; and
  • Installing a diversion trench on the high side of the disposal system to arrest and divert surface and sub-surface waters away from the disposal area.

Sub-surface soakage relies upon evaporisation of the effluent from the surface. It is therefore important to keep the area free of buildings, structures or other impervious coverings such as concrete paths or driveways.