Water is an essential resource for human life. We rely on it for our survival, as well as to preserve healthy ecosystems, to produce energy, and to meet agricultural and industrial demands. One way to help meet the increasing need for this vital resource is to recycle.
Reusing treated wastewater has numerous environmental benefits
Water recycling means reusing treated wastewater, which saves money and has numerous environmental benefits. Provided it has been properly treated, there is enough recycled water available to satisfy humans' needs. Water recycling is also called water reuse or water reclamation. Reclaimed water has a variety of beneficial uses, such as agricultural irrigation, industrial processes, and groundwater recharge, to name a few. The level of treatment water needs to undergo depends upon how the water will be used once recycled. Water treatment can be adjusted to meet the requirements of its planned reuse.
Recycled water is often water that has been reclaimed from a municipality's wastewater. However, water can also be reclaimed and reused on the same site.
Greywater is water that has been reclaimed from bathroom sink or shower drains, or laundry machine drains. It is typically recycled onsite for irrigation. When greywater is used for these purposes, it reduces the amount of potable water — or water that is safe for drinking — that needs to be withdrawn. In addition to saving clean water, using greywater reduces the amount of water going to wastewater treatment plants, saving energy and money. Reusing water onsite allows for a reliable water source that can be controlled locally.
|Using recycled water has several environmental benefits:|
|It prevents water from having to be diverted from other sources. Wildlife and plants depend on adequate water to survive. When water gets diverted away from an ecosystem, it can cause an otherwise healthy habitat to suffer.|
|Recycling water can help indirectly lessen the amount of wastewater that gets discharged into other bodies of water. Reducing the discharge of wastewater helps protect sensitive ecosystems.|
|Decreasing the amount of wastewater that is discharged into other bodies of water will decrease the number of pollutants that are released into those waters as well.|
|Recycled water can be used to create a new habitat. The flow of recycled water can be altered to create or enhance a wetland or riparian — or stream — habitat.|
|Recycled water often contains more nutrients than potable water, and thus it will be even more beneficial when used for irrigation. It may allow for the reduced application of synthetic fertilizers.|
|Using recycled water is much more energy-efficient than relying on your local source of water. Pumping, transporting, and treating groundwater requires a much greater amount of energy than using your own source of reclaimed water.|
Reclaiming wastewater for non-potable reuse is an effective and widely accepted way to recycle water. As demands for water continue to grow, and as wastewater treatment technology continues to advance, recycling for potable reuse may become commonplace. Recycling wastewater for potable reuse requires much less energy than using desalination technology to treat saltwater.
As our society's water demands grow, recycling water will play an increasingly important role in meeting those demands.
WATER RECLAMATION APPLICATIONS
In the United States, about 7 to 8 percent of wastewater gets reused. There are dozens of ways reclaimed water can be used across several different categories, such as agriculture, industry, and urban reuse.
Urban reuse is a major type of water reuse in the United States. There are two categories of application: those that are accessible to the public, and those that are restricted. Some common examples of urban water reuse include landscape irrigation, toilet flushing, and fire protection. Some other uses may include street sweeping, dust control, or decorative fountains.
Agricultural irrigation accounts for a large portion of freshwater use in the U.S. More severe droughts in certain parts of the country, combined with increasing water demands in urban areas, are challenging quality water availability for agricultural use. Many agricultural users rely on reclaimed water to meet their needs. Using reclaimed water is a reliable and cost-efficient method of supplementing and extending freshwater sources for agricultural practices.
Textile, pulp, and paper facilities have traditionally used reclaimed water for cooling purposes. Today, reclaimed water is in use in a variety of industries, like power plants, electronics, and oil refineries. Many are recognizing reclaimed water can be used in place of more costly potable water. Some municipalities have even started producing reclaimed water specifically for industrial uses.
Municipalities may use reclaimed water for recreational purposes to minimize the amount of potable water they use. Reclaimed water can be used to irrigate parks, recreational fields, golf courses, and outdoor areas around public schools. However, while reclaimed water is treated, it is not of the same quality as rainfall or drinking water. It is important to consider this point in the application of reclaimed water in recreational spaces. For example, certain plants in a landscape or turf on a golf course might be sensitive to the nutrients and salt in reclaimed water that is used for irrigation.
Water can be used to supplement wetlands and streams. Wetlands offer many benefits, like providing a healthy habitat for wildlife and supporting the food chain. Wetlands also help improve water quality, help with aquifer recharge, and mitigate flooding. Augmenting streams with reclaimed water has many of the same benefits, in addition to improving the aesthetics of the body of water, especially in locations where large volumes of water are drawn for potable water use.
As demand for water grows, the use of reclaimed water to increase the supply of drinking water has potential to help meet society's water needs in the future. Currently, the planned reuse of water as potable water only accounts for a small fraction of water reuse. However, de facto — or unplanned — reuse of water as potable water is more common. For example, many water treatment plants rely on water sources that contain large amounts of wastewater discharged from communities upstream.
THE WATER RECYCLING PROCESS
Regulations about the reuse of recycled water differ from state to state. Most states regulate the quality of recycled water that is reclaimed from centralized wastewater treatment facilities. About 30 states have regulations regarding the recycling of greywater.
The process of recycling water uses the following basic principles to remove contaminants from wastewater. It involves three steps: primary treatment, secondary treatment, and advanced treatment.
This step uses mechanical or physical processes to treat water, which removes about half the wastewater's contaminants. There are three stages of primary treatment.
|Bar Screens||Grit Chamber||Primary Clarification|
|First, wastewater is routed through a screen made up of vertical bars, which captures any large debris that might be contaminating the water. A mechanical rake combs the bars and moves the solids into a dumpster to be taken to a landfill.||Next, the wastewater flows into aerated grit chambers. In the grit chambers, air bubbles are introduced to the water, which causes fine grit particles to settle.||In this final step of primary treatment, water is moved into primary clarifiers, where it is slowed down to encourage remaining solids to settle. In this step, biosolids are captured for reuse. They are digested and dewatered and used for things like composting or soil conditioning.|
There are no recommended suggestions for water reuse at this level of treatment. For greywater reuse within an onsite system, the greywater may be able to be used for landscape irrigation after undergoing primary treatment. The greywater is required to be used with nontoxic or low-sodium personal care products. Greywater should be discharged below the surface, and it should be kept away from areas where it could come in contact with humans or drinking water.
With the exception of decentralized onsite greywater systems that meet specific requirements, most water in the U.S. must undergo primary and secondary treatment to be deemed acceptable for reuse.
In this step, biological processes further treatment. It is also called "bug farming" because it entails growing and harvesting populations of microorganisms. Secondary treatment eliminates most of the remaining water contaminants.
|Aeration Basins||Final Clarifiers|
|Water flows into the aeration basin, where it mixes with oxygen. Bacterial microorganisms consume organic material in the water. Non-settleable solids are converted into settleable solids, which are later captured in the final clarifiers.||The majority of the solids that settle in the final clarifiers are digested. The rest return to the aeration basin to provide more hungry microorganisms for the incoming water.|
There are several scenarios for reusing water that has undergone secondary treatment.
Suggestions for reuse include:
- surface irrigation of some agricultural fields, such as vineyards, orchards, and irrigation of some non-food crops
- landscape impoundment — an aesthetically pleasing body of water
- industrial processes, such as cooling purposes
- groundwater recharge for a non-potable water aquifer
- supporting and enhancing streams and wetlands
Advanced treatment is a chemical approach to water treatment that uses additional purification processes to disinfect the water after it has undergone primary and secondary treatment.
|After leaving the final clarifiers, water gets filtered through sand to remove any remaining particles. Sand filtering is a type of gravity filtration, and it usually occurs after final clarifiers and before disinfection.||Water undergoes chlorination for 20 minutes to destroy any pathogenic organisms. Then, the water is dechlorinated with sulfur dioxide or sodium bisulfite.||After the water has been fully treated, it is released into the environment. The point at which treated water is discharged into a body of water is called an outfall.|
After wastewater has undergone advanced treatment, there are more ways to reuse it.
Suggested uses for advanced treated water include:
- an unrestricted impoundment in a landscape or recreational space
- irrigation of golf courses or other landscapes
- irrigation of food crops
- toilet flushing, vehicle washing
With each level of treatment, the water becomes more acceptable for human exposure. Depending on the regulations governing a specific site, water that has undergone advanced treatment can be suitable for indirect potable reuse. Indirect potable reuse refers to reclaimed water being used for groundwater recharge of a potable aquifer or augmentation of a surface water reservoir.
Title XVI Water Reclamation and Reuse Program & WaterSMART Grants
The U.S. Bureau of Reclamation identifies opportunities to reclaim and reuse wastewater through its Title XVI Water Reclamation and Reuse Program. The program focuses on the Western states and Hawaii, and it provides funding for the planning, design, and construction of water recycling projects. Organizations complete reclamation and reuse projects in partnership with local government. The U.S. Bureau of Reclamation estimates that, in 2014, 378,000 acre-feet of water was recycled through projects funded by the Title XVI program.
The Bureau of Reclamation established WaterSMART in February 2010 as a way to implement the SECURE Water Act, which allows federal science and water agencies to work with water managers at the state and local level to secure water supplies. Congress passed the legislation as a way to address the threats to our water supplies, namely the potential impacts of climate change, as well as society's increasing water demands.
WaterSMART authorizes the Department of the Interior to work with state and local government, tribes, and non-government organizations to assists these organizations with efficient water use. The Bureau of Reclamation is the primary water management agency within the Department of the Interior. It functions to help those who manage water and resources make better decisions regarding water use.
WaterSMART Grants are available through the Bureau of Reclamation. Through the grant, the Bureau of Reclamation provides half the cost of water conservation projects to water districts or any other entities that deliver water or power. The bureau gives preference to projects that will help water supplies in the Western U.S. and can be completed within two years.
The projects should focus on:
- conserving water and using it more efficiently
- increasing the use of renewable resources
- protecting endangered species
- facilitating the buying and selling of water
GUIDELINES AND REGULATIONS WORLDWIDE
As population increases and water scarcity, drought, and the impacts of climate change become larger issues, water reuse is becoming an increasingly important topic worldwide.
In the U.S., the Environmental Protection Agency does not regulate reclaimed water use. However, the EPA did develop standards known as Guidelines for Water Reuse that offer best practices for water reuse. The document, most recently updated in 2012, is meant to set forth a standard for best practices worldwide, and serve as a guideline for states creating their own regulations governing water use.
Just as in the U.S., countries around the world use reclaimed water for many different purposes across industries, agriculture, and urban centers. Most of the reclaimed water in use today is for irrigating crops. Countries worldwide generate 180 to 250 billion gallons of domestic wastewater each day. Currently, we possess the capacity to treat to advanced levels a total of 8 billion gallons of water globally per day — or just 4 percent of the total amount of wastewater. However, the amount of water treated to advanced levels has been on the rise, which will, in turn, increase the amount of water that is acceptable for reuse.
The European Union acknowledges the benefits of reusing water, and regards water reuse as a priority. Currently, the amount of treated urban wastewater reused annually accounts for 2.4 percent of treated urban wastewater effluents and less than 0.5 percent of EU freshwater withdrawals. However, the EU estimates its member countries have the potential to reuse six times that amount.
Several European countries have initiatives in place regarding water reuse. Those that have taken steps toward regulating water reuse include Spain, Italy, Greece, Malta, Cyprus, Belgium, Germany, and the United Kingdom. The initiatives pertain to water reuse for industrial purposes, irrigation, and aquifer recharge.
There are many benefits to water reuse, and globally, there is ample capacity for expanding reuse. However, there are still several obstacles standing in the way of progress in this area. Some of the barriers include things like lack of financial resources or lack of social acceptance. Another obstacle may be the driving force behind current wastewater reuse in a specific country. For example, wastewater may be reused intentionally for its many benefits, or due to a lack of treatment facilities. These factors, as well as an individual country's economic priorities and local climate issues, may all play a role in whether it reaches its water reuse potential.
WATER RECLAMATION AND REUSE CAN CREATE A SUSTAINABLE FUTURE
As the global population continues to rise and we continue to see the effects of climate change, like drought and water scarcity, many are turning their attention toward water recycling as a way to extend the use of this precious resource. Those in industry and agriculture are seeking ways to use reclaimed water in their own operations, for purposes like cooling for plants and mills or irrigating crops. Reclaimed water has many suggested uses, such landscape irrigation, toilet flushing, fire protection, and augmentation of wetlands and streams, to name just a few.
There are costs and environmental benefits to using reclaimed water. Reusing water when applicable reduces the amount of potable water that is withdrawn and reduces the amount of wastewater discharge. It also lessens the amount of freshwater that gets diverted from sensitive wildlife habitats.
The more treatment wastewater undergoes, the more acceptable it becomes for human exposure. How water can be reused depends upon which level of treatment the water has received. In some cases, greywater can be recycled onsite and used for irrigation. As our global water needs continue to rise, potable reuse of recycled water is likely to become commonplace, especially because it is more affordable than water desalination.
In the meantime, there are many effective and widely accepted options for non-potable reuse of reclaimed water, and water users around the world are turning to water reclamation to aid sustainability.
Water Solutions for a Better way of life
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