Revision as of 13:33, 26 July 2010

Recycle used water

Recycle used water01. Water flow quantity improvement

General description

Urban and industrial used water can be reused for urban irrigation and cleaning, agriculture, aquiculture, or environmental uses like aquifer recharge or stream flows.

Applicability

Reuse recycled water decreases the pressure over the water resources and environmental contamination and is a sustainable alternative for water supply. Especially in countries with problems of water scarcity, the renewal of water contributes to secure the availability of the resource, and at the same time avoids the degradation of water quality and quantity. Sometimes water recycling emerges from the need to eliminate or decrease wastewater discharge to the ocean, an estuary, or a stream.

The scope of this measure starts with household re-use (for laundry, toilets…) without purifying treatments, and extents up to agricultural or environmental use at watershed scale.

The quality criteria for each use are defined by the competent organism of each country regarding to microorganisms, turbidity, suspended matter, and other pollutants. There are 5 main uses, which can be divided in different subcategories:

• Urban (irrigation of landscaped areas, ornamental landscape uses, dust control and concrete production, fire protection, toilet flushing in commercial areas, etc)
• Agrarian (agriculture, aquiculture, pastures, etc)
• Industrial (cooling water, boiler make-up water, industrial process water)
• Recreational (golf camp irrigation, recreational and aesthetic impoundments)
• Environmental:

• Groundwater recharge
• Surface water flow augmentation
• Enhance/restore wetlands and create artificial wetlands.

Reclaimed water reuse requires a conservative approach for water quality standards, at least with groundwater recharge for indirect potable reuse, where there is still some uncertainty about long-term health effects of contaminants, and chemical and microbiological safety has to be ensured. Thus, indirect potable reuse has lower social acceptance, and is necessary to improve public information, document better the benefits of water reuse, and impulse further research and innovate technology.

Expected effect of measure on (including literature citations):

• HYMO (general and specified per HYMO element)

• Increase of stream average flow at an expected rate (el volumen de descarga es conocido y controlado)
• Increase of groundwater recharge, elevation of the water table. Creation or recovery of aquifers.
• Increase of base flow of surface streams (Jiménez et al., 1998)
• Deep well injection helps to prevent saline intrusion into drinking water aquifers (RWCC, 1993)

• physico � chemical parameters
• Biota (general and specified per Biological quality elements)

Temporal and spatial response

The time of response for direct stream flow augmentation would be similar to Increase minimum flows

Pressures that can be addressed by this measure

• Discharge diversions and returns
• Interbasin flow transfers
• Groundwater abstractions
• Surface water abstraction

Cost-efficiency

The cost of water depuration and renewal depends on the final use of the water, and the quality or quantity of water subject to the process. Also on the existent technology available at each case and the need of innovate technology and technology transfers.

Water reuse provides a wide range of benefits for communities, which translates into creating immense value for the public and the environment. The benefits of water reuse, however, can be difficult to quantify and often go unrecognized (Wade 2006). Water reuse projects are often undervalued when compared to other projects due to the failure to properly quantify benefits of reuse such as watershed protection, local economic development, and improvement of public health. To date, no one has conducted a rigorous analysis in which the social and financial benefits of reuse are compared with both social and financial costs. Typically, water reuse project decisions are based on financial costs and benefits with no credit being given to non-monetizable benefits such as environmental protection (Wade 2006).

As the quality requirements for environmental uses are lower than for the other uses, their cost-efficiency is higher. Comparing the costs (energy and total costs), CO2 emission and social acceptance of different processes of water resources generation, water recycling seems to be the most suitable alternative with the highest cost-efficiency (table 1) and social acceptance due to public health risk from nonpotable reuse is minimal:

Case studies where this measure has been applied

• Tordera - Restoration of a secondary channel of the Tordera River

Useful references

Other relevant information