INTRODUCTION
Water recycling is a critical element for conservation of world’s water resource. Recycled water or reclaimed water is the wastewater, which is being treated to remove solids and certain impurities. This treated water is then used for extensive irrigation purposes, landscape irrigation, toilet flushing, industrial purposes and replenishing ground water. All water on Earth is recycled, but “recycled water” or “reclaimed water” means the wastewater, which is sent from homes and industries through pipelines to treatment plants. The process of treating wastewater or gray water is called Water Recycling. Sometimes recycled water is used to benefit ecosystem and improve aesthetics. On treating gray water, it is treated to meet the quality of water requirements for irrigation and other purposes. In other words, they are not treated enough to meet the quality standards for drinking water. Natural water cycle has facilitated water recycling on Earth for millions of years. Water recycling process may be characterized into two categories as planned or unplanned. One classic example of unplanned water recycling system is water from Colorado River and Mississippi river. Wastewater is collected upstream in these rivers and they undergo treatment several times, before the last downstream user withdraws water from pipelines. Planned water recycling projects are those that are designed with the specific goal to benefit through recycled water.
Water harvesting is different from water recycling because, water harvesting involves simple methods like building storage tanks to collect rain and storm water. Whereas in water recycling, a complex mechanism is involved to ensure that, any hazardous material and highly degraded material are removed.
NATURAL WATER CYCLE
Natural water cycle has been the base for the evolution of water recycling technique. It is otherwise called as the hydrologic cycle or H2O cycle. This cycle describes the continuous movement of water on, above and below the surface of Earth. Many cities and countries recycle sewage water for irrigation and landscaping. However, they have been treated to the standards of drinking water, some of the communities are resistant towards use of recycled water. So indirect potable technique is widely used, since people feel more comfortable if river is a water source.
WORKING MECHANISM OF WATER RECYCLING SYSTEMS:
Water recycling treatment involves a series of water treatments in order to put them to use. Each level of treatment makes the water suitable for use for various purposes. However, recycled water is not used for drinking purposes. Following is the flow chart of a basic water recycling system.
Indirect potable reuse is a system, which discharges water into a water body before reuse. Direct potable system discharges water for drinking directly after treatment. Direct potable system is generally not used in America but used safely in Namibia (Africa). The US Environmental Protection Agency regulated many aspects of drinking water quality and wastewater treatment. In 1992, EPA has released a technical document entitled “Guidelines for Water Reuse” which has information like summary of state requirements and guidelines for treatment and use of recycled water.
Although most of the water recycling projects is designed to meet nonpotable water demands, there are some projects, which use recycled water for indirect potable uses. These projects involve recharging ground water aquifers and surface reservoir augmentations with recycled water. In ground water recharge projects, recycled water is used to inject into ground water aquifers and to augment ground water supplies and prevent intrusion of salt water in coastal areas.
New technologies subject wastewater through three more stages namely: micro filtration, reverse osmosis and ultraviolet. By this way, impurities in the order of micron and nanometers can also be removed, thereby making it eligible for drinking water purpose. In future, if regulations are changed and recycled water proved to be purified to drinking water standards, they can be pumped directly into homes and industries.
ENVIRONMENTAL BENEFITS OF WATER RECYCLING
- Water recycling helps in decreasing diversion of fresh water from ecosystems
- Decreases or eliminates discharge of wastewater into sensitive water bodies like lakes, estuaries or oceans.
- Recycled water helps in enhancement or creating wetlands.
- Water recycling can reduce and prevent pollution
DISADVANTAGES OF WATER RECYCLING
- Cost of recycling water is more, but still industries provide them at lower cost to promote the use of recycled water for nonpotable uses.
- Perception of people regarding recycled water is negative. It is assumed that all recycled water is hazardous and dangerous to use, since its tagged nonpotable
- One of the key disadvantages of recycled water is the health hazards it can cause due to the bacteria it may contain. Recycled water may contain E. coli or other bacteria, which can travel to wherever water is directed. On using for food irrigation, it can cause food-borne illness.
DIFFERENT WATER RECYCLING SYSTEMS
There are different ways to recycle wastewater. Recycling is possible in homes also. It should be noticed that, use of recycled water is illegal in some states like North Carolina. Even water from sinks and showers are considered as sewage water. Following are some of the simple and common methods for recycling water.
- Waste Water Filtration System: This system uses a series of filters in a reservoir, to separate all solid and suspended matter in wastewater. They are most commonly used in association with rain barrel systems where sticks, leaves, stones, mud get collected. They can also be used in conjunction with sinks and showers, in order to monitor the use of this recycled water for purposes other than flushing toilets.
- Unfiltered Waste Water Pump Systems: Unfiltered pump system is the most commonly used setup for water recycling in homes. This method cannot be used with rain barrels, because it may get clogged with sediments. It can be connected to bathroom sinks and showers, to reuse water in toilets and gardens. In this method, water enters a reservoir with a pump, which will send water to toilet. Suggested only if organic soaps are used.
- Passive Grey water System: This is just a simple technique to reuse wastewater. If you carry a bucket to the shower, it will collect lot of water after bath. This collected water can then be used to flush toilet without any further treatments.
- Custom Grey water Systems: As the name suggests, water-recycling system can be customized as per requirement. It can specify where wastewater goes and use it for irrigation at timed intervals. It can also monitor how much water is recycled.
These are just a few examples of wastewater recycling techniques. A large variety of recycling systems are prevalent now.
ADVANCEMENTS IN WATER RECYCLING SYSTEMS
Large leaps have been taken in advancing water-recycling technologies.
Recycling Water from Shower: In space, astronauts use same recycled water repeatedly throughout their course of time in space. This is possible with the use of water recycling as we shower. It works as a closed loop system. As water falls from the shower and goes into the drain, it is instantly purified to drinking water standards and again pumped back through the shower. Since water is hot already, it needs to get slightly heated. This system, which is used in space, can also be used on Earth.
Membrane Separation System: This system offers the merits of space and energy savings, direct control of water purity, relatively low operating cost and no toxic chemical processing. This method is effective and efficient. It can recycle and purify water at considerably faster rates compared to conventional methods.
Microfiltration: Here, water is purified through microfiltration technology, which can remove impurities up to 0.5 microns. It saves up to one fourth of the space occupied by a conventional water-recycling device.
Reverse Osmosis: Reverse Osmosis or popularly known as RO is a widely used technique to purify water and use for drinking purposes. It detoxifies water and removes impurities up to 0.1 nanometers, which is not possible with other methods.
Grey water recycling is still an undeveloped technology. Water treatment technologies in future may be developed to purify heavily contaminated water to suitable standards, but still its impact on environment will be high and justifiable on industrial scale.
WATER REUSE IN COLORADO
Reclaimed water has been used for landscape irrigation in Colorado in places like Colorado Springs and Aurora since 1950s and early 1960s respectively. Reuse has become common in cities like Colorado Springs, Aurora, Denver and Westminster. Reused water makes up about 40% of Las Vegas Valley water resource. Of the remaining water resource, the Colorado River provides 90% and groundwater provides 10%. Majority of water is used outdoors at residences.
Policy Regarding Recycled Water in Colorado:
- Expand return flow to Colorado River to increase Nevada’s credit for subsequent withdrawal.
- Expand the use of recycle water in the Las Vegas Valley where large turf and industrial demands exist.
- Maximize the use of Recycled Water in areas of Southern Nevada where return flow to the Colorado River System is not practical, including the testing of aquifer storage and recovery.
- Develop a salt management strategy to address the accumulation of salts that are detrimental in Recycled water.
- Continue to advance the research of the health and safety implications of Recycled water
- Prohibit the use of treated or untreated Gray water in the Las Vegas Valley and prohibit its use outside the valley where there is reasonable potential for return flow to the Colorado River system or other Water Recycling programs.
- Educate the public about our local water cycle and the benefits of Recycled Water.
Denver Water supplies water for the city and country of Denver, Colorado and 70 suburban cities. As the largest water recycling facility of Colorado, treats up to 30 million gallons of effluent a day coming from the nearby metro waste water reclamation facility. This water is used for nonpotable demands. To supply drinking water, Denver Water treats water taken from South Platte River and Colorado’s Western slope of the Rockies. The water recycling plant diverts effluents from wastewater treatment plant, treats water from municipal sewage and industrial sources to a standard, which is safe to discharge into streams and rivers. For high-level treatment, water is tested for p H, turbidity, chlorine content and organics.
CONCLUSION:
Water recycling may not eliminate water scarcity across the world but it is definitely an effective solution for conservation of water for our future generations. In spite of the disadvantages of water recycling, its advantages takeover the necessity to develop this technique. Even if reused water cannot be put to use for drinking purposes, they serve a great deal as a source for non-potable utilities like cooling in industries, irrigation purposes, landscaping, betterment of ecological system, for recharging ground water aquifers, toilet flushing, etc., It is important to educate the public about the water recycling technique and remove the perception that, recycled water is hazardous.
REFERENCES
- Guidelines for Water Reuse. US EPA Office of Technology Transfer and Regulatory Support. EPA/625/R-92/004. September 1992
- Municipal Wastewater Reuse: Selected Readings on Water Reuse. Office of Water (WH-595) EPA 430/09-91-002. September 199.
- Layperson’s Guide to Water Recycling and Reuse, published in 1992 by the Water Education Foundation, Sacramento, California.
- Water from Water: Recycling, produced in 1995 by National Water Research Institute, Fountain Valley, California.
- Water in an Endless Loop, produced in 1997 by WateReuse Foundation, Sacramento, California.
- http://www.epa.gov/region09/water/recycling/
- www.denverwater.org/recycle/project_overview.html
- Water Recycling Comes of Age in Silicon Valley, audio report by Amy Standen for Quest Northern California on July 19, 2013.
- http://greenliving.lovetoknow.com/Household_Waste_Water_Recycling_Systems
- http://www.nasa.gov/home/hqnews/2004//HQ_04372_water_recycling.html
