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Treatment systems for intensive


Wastewater treatment occurs at special facilities called wastewater treatment plants. Wastewater treatment is the same as what occurs naturally in aquatic systems such as wetlands, lakes and rivers. However the purpose of wastewater treatment plants is to speed up Nature’s natural cleansing process. Over time the practice of wastewater collection and treatment has been developed and improved, using a variety of biological, physical, chemical and mechanical processes to protect public health and water quality.

QUU Sandgate sewage treatment plant. Source: Queensland Government

Quick facts

Domestic households produce an average of 200–300 litres of wastewater per person every day. 99% of this wastewater is water, the other 1% is the contaminating waste[1] .

Wastewater sources

Wastewater is the flow of used water discharged from homes, businesses, industries, commercial activities and institutions which is then directed to wastewater treatment plants by carefully designed, engineered and operated networks of pipes. This wastewater can be then further categorised and defined according to its sources of origin.The sewage collection system collects wastewater from domestic and non-domestic sources and consists of thousands of kilometres of pipelines that convey the wastewater to the wastewater treatment plant. The term domestic or municipal wastewater refers to from residential sources generated by such activities as food preparation, laundry, cleaning and personal hygiene. Industrial/commercial wastewater is flow generated and discharged from manufacturing and commercial activities such as printing, food and beverage processing for example, and this industrial wastewater is typically treated partially before being discharged to sewage collection systems and ultimately treated further at wastewater treatment plants. The amount of flow handled by a wastewater treatment plant typically varies with the time of day and with the season of the year.

Wastewater process flow diagram for a typical large scale sewage treatment plant. Source: Leonard G.

Wastewater treatment objectives

The overall objectives of wastewater treatment are two fold:

  1.  Protection of public health
  2.  Protection of environmental health.

The Queensland Environmental Protection Act 1994 regulates the sewage treatment activity and ensuring that treated effluent release to receiving waters does not cause ‘environmental harm’.

Wastewater treatment processes

Wastewater treatment facilities incorporate numerous processes, which in combination, achieve certain desired water quality objectives. These processes involve the separation, reduction, removal and disposal of certain contaminants present in wastewater.

The treatment of municipal wastewater is accomplished typically by four basic methods or techniques; physical, mechanical, biological and chemical:

  • Physical methods of wastewater treatment include the use of tanks and other structures designed to contain and control the flow of municipal wastewater to promote the removal of contaminants
  • Mechanical treatment techniques involve the use of machines, both simple and complex in design and operation
  • The action of bacteria and other microorganisms are biological methods of municipal wastewater treatment, which play a vital role in the removal of contaminants which cannot be effectively achieved by other means
  • Chemical treatment methods enhance the efficiency of other process operations and provide specialised treatment as a result of their addition at various treatment stages.

Additional Information

Introduction to Wastewater Treatment Process: Why We Treat Wastewater (1 of 4)

Introduction to Wastewater Treatment Process: Headworks Treatment (2 of 4)

Introduction to Wastewater Treatment Process: Secondary Treatment (3 of 4)

Introduction to Wastewater Treatment Process: Biosolids Treatment (4 of 4)

A Drop of Knowledge – The Non-operators Guide to Wastewater Systems

U.S. Environmental Protection Agency

Water Environment Federation


  1. ^ Department of Environment and Science, (29 January 2016). Wastewater. [online] Available at: [Accessed 3 October 2018].

Last updated: 11 September 2018

This page should be cited as:

Department of Environment and Science, Queensland (2018) Treatment systems for intensive, WetlandInfo website, accessed 13 May 2021. Available at:

Queensland Government
WetlandInfo   —   Department of Environment and Science