Treatment systems for intensive land uses

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. Treatment wetlands are sometimes added as a ’polishing’ stage to further improve the quality of the treated wastewater.

Quick facts

Engineered

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[5].

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.

Intensive animal husbandry, such as piggeries, feedlots, poultry farms and dairies, also produce effluent that needs to be treated and/or reused on farms.

Wastewater treatment objectives

The overall objectives of wastewater treatment are two fold:

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

Discharge from a sewage treatment plant or industrial wastewater is often classed as a point source discharge. The Queensland Environmental Protection Act 1994 regulates these activities and ensures 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.

Wetlands can be used as a ‘polishing’ stage after conventional treatment processes. They can effectively remove additional nutrients and suspended solids[1]. Wetlands can also be used to treat sewage and other wastewaters with high levels of contaminants. Capital and operating costs of such systems are lower than mechanical treatment systems, as is energy use, but the treatment effectiveness may not be as high, depending on the design and hydraulic retention time of the system[2][3][4]. Treatment systems may also be used off site as water quality offsets for intensive land uses.

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

• Start-Up of Municipal Wastewater Treatment Facilities; Environmental Protection Agency Office of  Water Program Operations
• Process Design Manual for Upgrading Existing Wastewater Treatment Plants, Technology Transfer
• Process Control Manual for Aerobic Biological Wastewater Treatment Facilities
• Design of Wastewater· Treatment Facilities Major Systems
• Nutrient Control Design Manual
• Primer for Municipal Wastewater Treatment Systems
• Operational Control Procedures for the Activated Sludge Process-Part I Observations and Part II Control Tests
• Operational Control Procedures for the Activated Sludge Process - Part IIIA Calculation Procedures
• Updated Summary of the Operational Control Procedures for the Activated Sludge Process

Water Environment Federation

• Operation of Municipal Wastewater Treatment Plants, 6th ed.; Manual of Practice No. 11
• Clarifier Design, 2nd ed.; Manual of Practice No. FD-8
• Operation of Water Resource Recovery Facilities; Manual of Practice No. 11; 7th ed.
• Wastewater Biology: The Microlife, 3rd ed.
• Design of Municipal Wastewater Treatment Plants, 5th ed.
• Design of Water Resource Recovery Facilities, MOP 8

Piggery manure and effluent management

• Feedlot waste management guidelines
• Integrating nature-based solutions into wastewater treatment

References

1. ^ Kavehei, E, Hasan, S, Wegscheidl, C, Griffiths, M, Smart, JCR, Bueno, C, Owen, L, Akrami, K, Shepherd, M, Lowe, S & Adame, MF (22 November 2021), 'Cost-Effectiveness of Treatment Wetlands for Nitrogen Removal in Tropical and Subtropical Australia', Water. [online], vol. 13, no. 22, p. 3309. Available at: https://www.mdpi.com/2073-4441/13/22/3309 [Accessed 21 December 2021].
2. ^ Nelson, M, Odum, HT, Brown, MT & Alling, A (January 2001), '“Living off the land”: resource efficiency of wetland wastewater treatment', Advances in Space Research. [online], vol. 27, no. 9, pp. 1547-1556. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0273117701002460 [Accessed 21 April 2022].
3. ^ Song, Z, Zheng, Z, Li, J, Sun, X, Han, X, Wang, W & Xu, M (March 2006), 'Seasonal and annual performance of a full-scale constructed wetland system for sewage treatment in China', Ecological Engineering. [online], vol. 26, no. 3, pp. 272-282. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0925857405002247 [Accessed 21 April 2022].
4. ^ Toet, S, Logtestijn, RSP, Kampf, R, Schreijer, M & Verhoeven, JTA (June 2005), 'The effect of hydraulic retention time on the removal of pollutants from sewage treatment plant effluent in a surface-flow wetland system', Wetlands. [online], vol. 25, no. 2, pp. 375-391. Available at: http://link.springer.com/10.1672/13 [Accessed 21 April 2022].
5. ^ Department of Environment and Science, (29 January 2016). Wastewater. [online] Available at: https://www.ehp.qld.gov.au/water/monitoring/wastewater.html [Accessed 3 October 2018].

Last updated: 27 June 2022