Reclaimed water facts for kids

Sequence of reclamation from left: raw sewage, plant effluent, and finally reclaimed water (after several treatment steps)

Reclaimed or recycled water (also called wastewater reuse or water reclamation) is the process of converting wastewater into water that can be reused for other purposes. Reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater (i.e., groundwater recharge). Reused water may also be directed toward fulfilling certain needs in residences (e.g. toilet flushing), businesses, and industry, and could even be treated to reach drinking water standards. This last option is called either "direct potable reuse" or "indirect potable" reuse, depending on the approach used.

Reclaiming water for reuse applications instead of using freshwater supplies can be a water-saving measure. When used water is eventually discharged back into natural water sources, it can still have benefits to ecosystems, improving streamflow, nourishing plant life and recharging aquifers, as part of the natural water cycle.

Wastewater reuse is a long-established practice used for irrigation, especially in arid countries. Reusing wastewater as part of sustainable water management allows water to remain as an alternative water source for human activities. This can reduce scarcity and alleviate pressures on groundwater and other natural water bodies.

Overview
- Driving forces
Potential benefits
Health aspects
Environmental aspects
Images for kids
See also

Overview

Irrigation water is pumped from this tank which stores effluent received from a constructed wetland in Haran-Al-Awamied, Syria.

Reclaimed water sign in Dunedin, United States

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 and 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.

Potential benefits

Water/wastewater reuse, as an alternative water source, can provide significant economic, social and environmental benefits. These benefits include:

For cities and households: Increased water availability (drinking water substitution – keep drinking water for drinking and reclaimed water for non-drinking use (i.e. industry, cleaning, irrigation, domestic uses, toilet flushing, etc.)
For the environment: Reduced nutrient loads to receiving waters (i.e. rivers, canals and other surface water resources); 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 (1.2 to 2.1 kWh/m³) 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 (i.e. conservation of nutrients and reducing the need for artificial fertilizer (e.g. soil nutrition by the nutrients existing in the treated effluents).

Health aspects

Reclaimed water is considered safe when appropriately used. Reclaimed water planned for use in recharging aquifers or augmenting surface water receives adequate and reliable treatment before mixing with naturally occurring water and undergoing natural restoration processes. Some of this water eventually becomes part of drinking water supplies.

A study published in 2009 compared the water quality differences of reclaimed/recycled water, surface water, and groundwater. Results indicate that reclaimed water, surface water, and groundwater are more similar than dissimilar with regard to constituents. The researchers tested for 244 representative constituents typically found in water. When detected, most constituents were in the parts per billion and parts per trillion range. DEET (an insect repellant) and caffeine were found in all water types and virtually in all samples. Triclosan (in antibacterial soap and toothpaste) was found in all water types, but detected in higher levels (parts per trillion) in reclaimed water than in surface or groundwater. Very few hormones/steroids were detected in samples, and when detected were at very low levels. Haloacetic acids (a disinfection by-product) were found in all types of samples, even groundwater. The largest difference between reclaimed water and the other waters appears to be that reclaimed water has been disinfected and thus has disinfection by-products (due to chlorine use).

A 2005 study found that there had been no incidences of illness or disease from either microbial pathogens or chemicals, and the risks of using reclaimed water for irrigation are not measurably different from irrigation using potable water.

A 2012 study conducted by the National Research Council in the United States of America found that the risk of exposure to certain microbial and chemical contaminants from drinking reclaimed water does not appear to be any higher than the risk experienced in at least some current drinking water treatment systems.

Environmental aspects

Uses of recycled water in California, 2011

Using reclaimed water for non-potable uses saves potable water for drinking, since less potable water will be used for non-potable uses.

It sometimes contains higher levels of nutrients such as nitrogen, phosphorus and oxygen which may somewhat help fertilize garden and agricultural plants when used for irrigation.

Fresh water makes up less than 3% of the world's water resources, and just 1% of that is readily available. Even though fresh water is scarce, just 3% of it is extracted for human consumption. The remaining water is mostly used for agriculture, which uses roughly two thirds of all fresh water.

Reclaimed water can offer a viable and effective alternative where freshwater supplies are scarce. Reclaimed water is utilized to maintain or increase lake levels, restore wetlands, and restore river flows during hot weather and droughts, protecting biodiversity. Additionally, reclaimed water is utilized for street cleaning, irrigation of urban green spaces, and industrial processes. Reclaimed water has the advantage of being a consistent source of water supply that is unaffected by seasonal droughts and weather changes.

The usage of water reclamation decreases the pollution sent to sensitive environments. It can also enhance wetlands, which benefits the wildlife depending on that ecosystem. It also helps to stop the chances of drought as recycling of water reduces the use of fresh water supply from underground sources. For instance, the San Jose/Santa Clara Water Pollution Control Plant instituted a water recycling program to protect the San Francisco Bay area's natural salt water marshes.

The main potential risks that are associated with reclaimed wastewater reuse for irrigation purposes, when the treatment is not adequate are the following:

contamination of the food chain with microcontaminants, pathogens (i.e. bacteria, viruses, protozoa, helminths), or antibiotic resistance determinants;
soil salinization and accumulation of various unknown constituents that might adversely affect agricultural production;
distribution of the indigenous soil microbial communities;
alteration of the physicochemical and microbiological properties of the soil and contribution to the accumulation of chemical/biological contaminants (e.g. heavy metals, chemicals (i.e. boron, nitrogen, phosphorus, chloride, sodium, pesticides/herbicides), natural chemicals (i.e. hormones), contaminants of emerging concern (CECs) (i.e. pharmaceuticals and their metabolites, personal care products, household chemicals and food additives and their transformation products), etc.) in it and subsequent uptake by plants and crops;
excessive growth of algae and vegetation in canals carrying wastewater (i.e. eutrophication);
groundwater quality degradation by the various reclaimed water contaminants, migrating and accumulating in the soil and aquifers.

Images for kids

A lavender-colored pipeline carrying non-potable water in a dual piping system in Mountain View, California, U.S.