Reclaimed water
Water reclamation is the process of converting municipal wastewater or sewage and industrial wastewater into water that can be reused for a variety of purposes. It is also called wastewater reuse, water reuse or water recycling. There are many types of reuse. It is possible to reuse water in this way in cities or for irrigation in agriculture. Other types of reuse are environmental reuse, industrial reuse, and reuse for drinking water, whether planned or not. Reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater. This latter is also known as groundwater recharge. Reused water also serve various needs in residences such as toilet flushing, businesses, and industry. It is possible to treat wastewater to reach drinking water standards. Injecting reclaimed water into the water supply distribution system is known as direct potable reuse. Drinking reclaimed water is not typical. Reusing treated municipal wastewater for irrigation is a long-established practice. This is especially so in arid countries. Reusing wastewater as part of sustainable water management allows water to remain an alternative water source for human activities. This can reduce scarcity. It also eases pressures on groundwater and other natural water bodies.
There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from pathogens. The following are some of the typical technologies: Ozonation, ultrafiltration, aerobic treatment, forward osmosis, reverse osmosis, and advanced oxidation, or activated carbon. Some water-demanding activities do not require high grade water. In this case, wastewater can be reused with little or no treatment.
The cost of reclaimed water exceeds that of potable water in many regions of the world, where fresh water is plentiful. The costs of water reclamation options might be compared to the costs of alternative options which also achieve similar effects of freshwater savings, namely greywater reuse systems, rainwater harvesting and stormwater recovery, or seawater desalination.
Water recycling and reuse is of increasing importance, not only in arid regions but also in cities and contaminated environments. Municipal wastewater reuse is particularly high in the Middle East and North Africa region, in countries such as the UAE, Qatar, Kuwait and Israel.
Definition
The term "water reuse" is generally used interchangeably with terms such as wastewater reuse, water reclamation, and water recycling. A definition by the USEPA states: "Water reuse is the method of recycling treated wastewater for beneficial purposes, such as agricultural and landscape irrigation, industrial processes, toilet flushing, and groundwater replenishing." A similar description is: "Water Reuse, the use of reclaimed water from treated wastewater, has been a long-established reality in many arid countries and regions. It helps to alleviate water scarcity by supplementing limited freshwater resources."The water that is used as an input to the treatment and reuse processes can be from a variety of sources. Usually it is wastewater but it could also come from urban runoff.
Overview
Reclaimed water is water that is used more than one time before it passes back into the natural water cycle. Advances in municipal wastewater treatment technology allow communities to reuse water for many different purposes. The water is treated differently depending upon the source and use of the water as well as how it gets delivered.Driving forces
The World Health Organization has recognized the following principal driving forces for municipal wastewater reuse:- increasing water scarcity and stress,
- increasing populations and related food security issues,
- increasing environmental pollution from improper wastewater disposal, and
- increasing recognition of the resource value of wastewater, excreta and greywater.
Water recycling and reuse is of increasing importance, not only in arid regions but also in cities and contaminated environments.
Already, the groundwater aquifers that are used by over half of the world population are being over-drafted. Reuse will continue to increase as the world's population becomes increasingly urbanized and concentrated near coastlines, where local freshwater supplies are limited or are available only with large capital expenditure. Large quantities of freshwater can be saved by municipal wastewater reuse and recycling, reducing environmental pollution and improving carbon footprint. Reuse can be an alternative water supply option.
Achieving more sustainable sanitation and wastewater management will require emphasis on actions linked to resource management, such as wastewater reuse or excreta reuse that will keep valuable resources available for productive uses. This in turn supports human wellbeing and broader sustainability.
Potential benefits
Water/wastewater reuse, as an alternative water source, can provide significant economic, social and environmental benefits, which are key motivators for implementing such reuse programs. These benefits include:- For cities and households: Increased water availability.
- For the environment: Reduced nutrient loads to receiving waters ; reduced over-abstraction of surface and groundwater; enhanced environmental protection by restoration of streams, wetlands and ponds; reduced energy consumption associated with production, treatment, and distribution of water compared to using deep groundwater resources, water importation or desalination
- Reduced manufacturing costs of using high quality reclaimed water
- In agriculture: Irrigation with treated wastewater may contribute to improve production yields, reduce the ecological footprint and promote socioeconomic benefits. It may also lead to reduced application of fertilizers.
Scale
Global treated wastewater reuse is estimated at 40.7 billion m3 per year, representing approximately 11% of the total domestic and manufacturing wastewater produced. Municipal wastewater reuse is particularly high in the Middle East and North Africa region, in countries such as the UAE, Qatar, Kuwait and Israel.For the Sustainable Development Goal 6 by the United Nations, Target 6.3 states "Halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally by 2030".
Types and applications
Treated wastewater can be reused in industry, in artificial recharge of aquifers, in agriculture, and in the rehabilitation of natural ecosystems. The main reclaimed water applications in the world are shown below:| Categories of use | Uses |
| Urban uses | Irrigation of public parks, sporting facilities, private gardens, roadsides; Street cleaning; Fire protection systems; Vehicle washing; Toilet flushing; Air conditioners; Dust control. |
| Agricultural uses | Food crops not commercially processed; Food crops commercially processed; Pasture for milking animals; Fodder; Fibre; Seed crops; Ornamental flowers; Orchards; Hydroponic culture; Aquaculture; Greenhouses; Viticulture. |
| Industrial uses | Processing water; Cooling water; Recirculating cooling towers; Washdown water; Washing aggregate; Making concrete; Soil compaction; Dust control. |
| Recreational uses | Golf course irrigation; Recreational impoundments with/without public access ; Aesthetic impoundments without public access; Snowmaking. |
| Environmental uses | Aquifer recharge; Wetlands; Marshes; Stream augmentation; Wildlife habitat; Silviculture. |
| Potable uses | Aquifer recharge for drinking water use; Augmentation of surface drinking water supplies; Treatment until drinking water quality. |
Urban reuse
In rarer cases reclaimed water is also used to augment drinking water supplies. Most of the uses of water reclamation are non-potable uses such as washing cars, flushing toilets, cooling water for power plants, concrete mixing, artificial lakes, irrigation for golf courses and public parks, and for hydraulic fracturing. Where applicable, systems run a dual piping system to keep the recycled water separate from the potable water.Usage types are distinguished as follows:
- Unrestricted: The use of reclaimed water for non-potable applications in municipal settings, where public access is not restricted.
- Restricted: The use of reclaimed water for non-potable applications in municipal settings, where public access is controlled or restricted by physical or institutional barriers, such as fencing, advisory signage, or temporal access restriction.
Agricultural reuse
The irrigation water can be used in different ways on different crops, such as for food crops to be eaten raw or for crops which are intended for human consumption to be eaten raw or unprocessed. For processed food crops: crops which are intended for human consumption not to be eaten raw but after food processing. It can also be used on crops which are not intended for human consumption.