In the guide below, we discuss water recycling, reuse and reclamation.
We outline what it is, the different technologies and processes/methods used, examples of where & how it’s used in the world, and more.
What Is Water Recycling? (A Definition)
Water recycling refers to the man made process that converts different types of waste water into water that can be re-used for both potable, or non potable purposes.
Waste water treatment plants do this by removing pathogens, nutrients, organic matter and other pollutants, contaminants, and unwanted substances and chemicals from waste water.
Waste water such as municipal waste water and sewage water (from households as one example), stormwater, industrial waste water and cooling water (from different industrial processes), agricultural runoff, and other types of waste water are filtered and treated (including disinfection) to certain standards, and then re-used for a specific end use, such as irrigation in agriculture, different industrial processes, home uses, groundwater recharge, and even drinking water.
This is in comparison to the water that naturally gets recycled and reused as a part of the hydrologic cycle (where water naturally flows/circulates through Earth’s systems, via precipitation, transportation, and condensation)
Water recycling is also referred to as ‘Water Reuse’, ‘Water Reclamation’, ‘Wastewater Recycling’, or ‘Reclaimed Wastewater’.
For the purposes of this guide, we refer to it as ‘Water Recycling’
Water Reclamation vs Reuse – Is There A Difference?
Some reports delineate between reclamation and reuse, with reclamation being the ‘treatment’ process of ‘reclaiming’ waste water by bringing it back to a quality which is ‘fit for purpose’, and reuse being using that water again after treatment.
However, many reports simply use these terms interchangeably to describe water recycling as a whole
Main Types Of Water Recycling
There might be a few key ways to categorise the different types of water recycling.
Potable vs Nonpotable Water Reuse
The first way is potable reuse (for drinking water), and nonpotable reuse (water other than drinking water).
Some examples of potable and nonpotable water reuse might include:
– Direct Potable Reuse
– Indirect Potable Reuse
– Nonpotable Reuse
*There’s also a specific type of practice that can be used in water reuse called ‘Resource Recovery’, where there’s a focus on recovering nutrients like nitrogen and phosphorus, as well as other resources.
fluencecorp.com explains resource recovery in more detail, but, it can in some instances be a part of waste water recycling in addition to the above forms of reuse.
The Different Sources Of Water
The second way might be by the type of water being treated and recycled.
Some examples of the different types of water that might be recycled might include:
– Municipal wastewater (grey water, sewage waste, etc)
– Industrial wastewater, and cooling water
– Agricultural runoff
Other Water Recycling Technology
In their report, sswm.info lists and describes what they call the different technologies available for direct reuse as well as decentralised wastewater treatment for wastewater recycling for businesses.
Those are ‘Direct Re-Use Within Business’, ‘Direct Re-Use Between Businesses’, and ‘Treat & Re-Use (Recycling)’
Direct vs Indirect Potable Water Reuse
The main difference between these two forms of potable water that is reused is:
– Direct potable water reuse refers to directly treating waste water at a wastewater treatment facility or plant (without releasing it into the environment first as waste water), and then directly using it as drinking water (either with, or without further treatment)
– Indirect potable water reuse refers to discharging treated waste water into the environment first, such as into lakes, rivers, or aquifers.
Here, it is diluted or purified naturally, and may sometimes be treated again before being reused
Some forms of indirect potable water reuse are part of managed programs
Planned vs Unplanned Water Reuse
A paraphrased summary from an epa.gov explanation of the differences of the two is:
– Unplanned water reuse involve using water from a water source where that water contains previously used water e.g. using water from a river or lake that receives treated water water discharge
– Planned water reuse involves using water that comes directly from water systems designed specifically to reuse that water
The Different End Uses For Treated Wastewater & Recycled Water
We’ve listed some potential end uses for reclaimed wastewater elsewhere in this guide
However, usgs.gov also provides an extensive list of the urban, agricultural, recreational, environmental, and potable uses for reclaimed wastewater
Water Recycling Technologies, Processes & Methods
There’s a range of water recycling technologies, processes and methods, and the ones that are used can be influenced by the type of water being treated, what it will be used for, the desired treated water quality, recycled water regulations in the area, and other factors.
nationalacademies.org (paraphrased) lists different types of technologies used for water recycling, as well as both engineered/man made and natural processes that can be used for water treatment
They also list and explain the different steps and processes used for preliminary, primary, secondary and advanced treatment of waste water, as well as for natural treatment
Some of the different processes and steps in wastewater recycling they identify are sedimentation, disinfection, and a range of other steps and processes
They have a good diagram showing the different steps and processes used for different types of waste water treatment, as well as going into detail with more information in their guide
fluencecorp.com mentions some of the technology and processes being used for a direct potable reuse system in Texas in 2014 as ‘… traditional wastewater treatment, microfiltration, reverse osmosis (RO), and ultraviolet disinfection’
wikipedia.org lists some of the other technologies as ‘Ozonation, ultrafiltration, aerobic treatment (membrane bioreactor), forward osmosis, reverse osmosis, [and] advanced oxidation’
Different Levels Of Treatment For Water
Factors That Can Impact How Water Is Treated
There’s different levels of treatment for water, depending on:
– The initial quality of the water, and what minerals, particles or contaminants the water has in it
– What the water is going to be used for for it’s end use, and what quality the water has to reach for it’s end use
– The regulations and legislation around water recycling/water reuse in the region the water is being reused
Examples Of The Levels Of Water Treatment
Some examples of the different levels of treatment in some countries are:
– Preliminary treatment
– Primary treatment
– Secondary treatment
– Tertiary treatment
– Advanced treatment
Separate Pipes For Non potable Recycled Water
Some municipalities around the world have separate/dedicated water pipe networks for non potable recycled water in order to both keep it separate from, and to prevent it from being mistaken as regular potable water (drinking water)
These non potable recycled water pipes are often color coded in a certain color.
They may also come with signage on pipes and taps warning that they are not for drinking
Water Recycling Regulations, Standards & Guidelines
There’s regulations, standards and guidelines in most developed countries which ensure recycled water is safe for it’s end use.
And, the quality and/or safety of the end recycled water product might be measured in various ways.
Examples of Regulations & Guidelines For Wastewater Treatment & Recycled Water
Some examples of recycled water regulations might include:
– In The US
According to EPA.gov:
[In the US … the] States maintain regulatory authority in allocating and developing water resources … [with some States establishing] programs to specifically address reuse, and some have incorporated water reuse into their existing programs.
EPA, states, tribes, and local governments implement programs under the Safe Drinking Water Act and the Clean Water Act to protect the quality of drinking water source waters, community drinking water, and waterbodies like rivers and lakes.
Together, the Safe Drinking Water Act and the Clean Water Act provide a foundation from which states can enable, regulate, and oversee water reuse as they deem appropriate.
– In Australia
… in Australia, recycled water quality has to meet the ‘Australian Guidelines For Water Recycling’ (sydneywater.com.au)
Internationally, WHO, FAO and UNEP have developed guidelines for the safe use of waste water (wikipedia.org).
– Other Regulations & Guidelines
More regulations and guidelines for different regions in the world can be found at wikipedia.org
Other Notes About Wastewater Quality & Safety
Different Ways To Measure Safety & Quality Of End Recycled Water Product
Some of the different ways water may have to met certain quality and safety guidelines might include:
– Being safe for consumption by humans, or safe for contact with humans (i.e. safe for public health)
– Being safe for the environment, plants, and soils
– Maintaining food safety when used as irrigation on crops for example
What Other Reports Say About Wastewater Quality
sswm.info indicates the following about wastewater quality in their report on wastewater treatment and reuse for businesses:
To ensure that the quality of the (pre-treated) wastewater or grey water is appropriate for reuse, the water quality should be tested for chemical composition, including pH, nutrient concentrations, pathogens, etc.
How Much Does Water Recycling Cost?
The cost of recycled water can vary between different regions within different countries, and with different variables.
And, over time, improvements or development with water recycling may lead to lower costs.
However, right now, one report indicates that both potable and non potable water reuse might be the second and third most costly water sources to produce behind seawater desalination.
Water recycling may be even more expensive if it requires it’s own infrastructure in the form of dedicated pipes (like it does in some regions), and, if water recycling facilities are further away from where the water is supplied from
Variables That May Impact The Cost Of Water Recycling
The cost to recycle water can be dependent on different variables.
Some examples of these variables might include:
The costs of water reuse vary greatly from place to place depending on location, water quality requirements, treatment methods, distribution system needs, energy costs, interest rates, subsidies, and many other factors (nas-sites.org).
Cost To Produce Recycled Water vs Other Types Of Water
One report by mercurynews.com indicates that (paraphrased from a graphic/table), the price to produce water from different water sources is as follows:
Seawater Desalination – $2200 to $4300
Indirect Potable Reuse – $1600 to $2700
Nonpotable Reuse – $1500 to $2100
Brackish Desalination – $950 to $1800
Stormwater Capture – $570 to $1600
Surface Water – $386 to $1884
Groundwater – $90 to $960
From nas-sites.org: “Generally, water reuse is … less expensive than seawater desalination”
Some Locations Produce Recycled Water At A Cheaper Cost
Some locations may be cheaper to set up and operate water recycling plants at than others, according to abc.net.au: ‘It is the cheapest to operate waste water plants and water recycling plants close to where water is traditionally supplied from’
Separate Water Recycling Pipe Networks – Potential Added Cost
From nas-sites.org: “Generally, water reuse is more expensive than drawing water from a natural freshwater source …” [and non potable waste water treatment can be most expensive if it requires separate and dedicated water pipes]
Examples Of Water Recycling Worldwide
There appears to be many countries across the world currently using some form of wastewater recycling
Number Of Waste Water Treatment Plants Currently Used Around The World
A 2022 waternewseurope.com report references data in the global database HydroWASTE, and indicates there’s currently 58,502 wastewater treatment plants in operation worldwide
Regions With The Most Water Recycling
From Blanca Elena Jiménez Cisneros, via fluencecorp.com:
In total volume, China, Mexico and the United States are the countries with the largest quantity of wastewater reuse, but in the first two cases non-treated wastewater is involved, and for China the value reported is certainly underestimated.
[Water reuse in Arab nations since 2011 has increased dramatically, whilst Europe is lagging in adoption of treated wastewater reuse]
Singapore is leading the world’s technology for water recycling (awa.asn.au)
Other Regions That Currently Recycle Wastewater
Some examples of cities or regions that currently recycle wastewater include:
California, where ‘… the state recycles about 728,000 acre feet of water per year [but have the potential to recycle much more, and officials are …] shifting away from construction of new dams and reservoirs … (watereducation.org)
According to fluencecorp.com, both Sydney and Perth in Australia currently use forms of ‘Indirect Potable Water Reuse’
wikipedia.org gives other examples of water recycling being used in Australia, Israel, Namibia, Singapore and also South Africa
Potential Pros & Cons Of Water Recycling
Read more about the potential pros and cons of water recycling in this guide.
Desalination vs Water Recycling Comparison
13. Various ‘Better Meets Reality’ guides