August 2011, Vol. 23, No.8

Operator Essentials

What every operator should know about water reclamation and reuse

Craig Riley

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Knowledge

Principle

A practical consideration

Reclaimed or recycled water

Wastewater that has gone through specific treatment processes to meet specific water quality criteria with the intent of being used in a beneficial manner as a water supply

Water reclamation projects often start as a means to reduce wastewater flows and loads discharged to the environment. Reclaimed or recycled water is a water supply that should be considered as an integral component of water resources management in water-scarce areas.

Graywater

Wastewater, excluding toilet/urinal wastewater — and in most cases — dishwasher and kitchen sink wastewaters

Graywater use generally is limited to onsite, subsurface irrigation; if treatment is provided in accordance with state and local codes for other uses, the water can become reclaimed or recycled water.

Beneficial uses

The many ways reclaimed water can be used

Examples of beneficial uses include irrigation, industrial applications, toilet and urinal flushing, wildlife enhancement, aesthetic and recreational impoundments, and municipal water supply.

End user

The final customer, either wholesale or retail

End users can range from public entities such as cities purchasing reclaimed water wholesale to industry purchasing reclaimed water commercially to individual homeowners buying water for lawn irrigation.

Use area

An area of reclaimed water use with defined boundaries or limits, such as a building or site permitted to use reclaimed water

Use areas range from large sites, such as golf courses and parks, to residential lawns or city median strips. Permits may be required for individual sites or sites grouped by different types of use.

End-user agreement

A legally binding agreement between the supplier and reclaimed water user that (among other things) establishes terms and conditions of service; describes reclaimed water supply availability, quality, and cost; and lists responsibilities of both parties for signage, use control, and compliance monitoring

Agreements define the responsibilities of both the supplier and user of the reclaimed water. They are intended to ensure that water users are aware of and trained in the proper use of reclaimed water and that utilities are protected from permit violations that are beyond their control.

Dual distribution system

The system of pipes used to distribute reclaimed water to end users

Dual distribution systems utilize separate piping systems for reclaimed and potable water. Special pipe separation standards are often required for construction.

Purple pipe

The color code specifically designated for reclaimed water distribution systems and appurtenances

Color shade Pantone 522 or 512 is required in several states. Pipes, valves, or hydrants can be colored or painted purple; marked with purple identification tags; or wrapped in purple polyethylene wrap or identification tape.

Reclaimed water storage

A reclaimed water impoundment or conventional steel/concrete storage tank to facilitate the distribution and use of the water

Storage of reclaimed water may be needed for several uses, including fire protection equivalent to potable water distribution systems, landscape or crop irrigation, recreation, and industrial process water.

Cross connection control

Preventing a physical connection between a potable water system and any potential source of contamination through a physical connection in a plumbing system through which a potable water supply could be contaminated by nonpotable water

Cross connection protection for water reclamation projects involves the protection of potable water systems from cross contamination from reclaimed water. It also includes protection of reclaimed water systems from contamination by lower-quality water.

Nonpotable reuse

Use of reclaimed water for nonpotable uses in buildings, industries, lawn and turf irrigation, and nonpotable municipal needs

Nonpotable water use within communities constitutes the majority of the water system demand. Uses include toilet and urinal flushing, cooling and heating, street cleaning, sewer flushing, ship ballast, fountains, and watering residential lawns and gardens as well as cemeteries, parks, and golf courses.

Indirect potable reuse

Augmentation of a drinking water source (surface water or groundwater) with reclaimed water followed by an environmental buffer that precedes normal drinking water treatment

Indirect potable reuse can occur via groundwater recharge, discharge to a raw water reservoir, or discharge to a watercourse where water is subsequently withdrawn for treatment and potable use.

Direct potable reuse

The introduction of highly treated reclaimed water either directly into the potable water supply distribution system downstream of a water treatment plant, or into the raw water supply immediately upstream of a water treatment plant

Direct potable reuse does not include passage of reclaimed water through an environmental buffer.

Environmental buffer

For surface water discharge, a natural waterbody, such as a reservoir, river, or lake, that physically separates reclaimed water from the intake to a drinking water plant

 

For groundwater recharge, the soil and aquifer that physically separate the reclaimed water recharge site from a potable water extraction well

An environmental buffer may or may not improve the quality of the reclaimed water. In fact, the reclaimed water is almost always of a higher quality than the water it mixes with in an environmental buffer.

 

The main advantage of an environmental buffer is that it provides time to respond to situations where the reclaimed water introduced into the environmental buffer is found to not meet all appropriate standards.

Aquifer storage and recovery (ASR)

Use of reclaimed water to recharge local aquifers through either surface spreading or direct injection

Reclaimed water ASR can function exactly like potable water ASR, storing reclaimed water underground for use during peak demand periods.

Environmental uses

Reclaimed water use to enhance the environment

Environmental uses include wetland creation, replacement, or augmentation, as well as stream augmentation to maintain or supplement minimum streamflows.

Reliability

The ability of a treatment system or component(s) to perform a required function under stated conditions for a stated period of time

Reclaimed water systems must produce reclaimed water of defined quality at all times. Unless reclaimed water continuously meets all water quality limits while all required treatment processes are on-line and functioning properly, the water cannot be sent to the end user. Reliability is based on applying multiple protective barriers for microbial and chemical contaminants.

  

Craig Riley is reuse program lead at the Washington State Department of Health and chairman of the Water Environment Federation (Alexandria, Va.) Water Reuse Committee.

The author would like to thank Water Reuse Committee members Jim Crook, Alan Rimer, and Don Vandertulip for their assistance with this article.

 

©2011 Water Environment Federation. All rights reserved.