Uses for Reclaimed Water

While there are hundreds of possible usages for reclaimed water, there have been several categories of these usages created, to help simplify the information, and make it easier to generalize the information. The following seven categories will be used on this website:

  1. Agricultural Irrigation
  2. Landscape Irrigation
  3. Industrial Reuse
  4. Groundwater Recharge
  5. Recreational/Environmental
  6. Nonpotable Urban uses
  7. Potable reuse
  8. Miscellaneous

For a very short summary of a number of case studies, please read "The Environmental Benefits of Water Recycling and Reuse" by John Anderson. The paper is available for free online at http://www.iwaponline.com/ws/00304/04/default.htm through Water Science and Technology: Water Supply. There are a number of very short descriptions of reuse projects throughout the world on pages 2-6.

Agricultural Irrigation

The use of reclaimed water in agriculture is the most popular usage. Sewage farms date back as far as 1550 in Germany (Asano, 1996). Agricultural irrigation is the most popular usage for reclaimed water because crop irrigation water does not come into contact with the public very often. For this reason, water does not need to be of high quality. Crops actually benefit from some of the chemicals that are naturally found in treated wastewater such as nitrogen and phosphorus (these are the most common constituents of lawn fertilizers). Generally, different regulations are placed on agricultural irrigation, depending on how the crops are grown, and how they are going to eventually be prepared. For instance, a crop of potatoes grown for the production of French fries will not need to be irrigated with water the same quality that a crop of lettuce that is sold at the farmers market. While it is likely that someone will eat the lettuce raw (and therefore consume the reclaimed water), the potatoes are processed into French fries, and then cooked, thus eliminating the risk in someone getting sick from the reclaimed water.

Reference:

Asano, T., & Levine, A. D. (1996). Wastewater reclamation, recycling and reuse: past, present, and future. Water Science and Technology Proceedings of the 1995 IAWQ 2nd International Symposium on Wastewater Reclamation and Reuse, Oct 17-20 1995, 33(10-11TY - JOUR), 1-14.

Case Studies in Agricultural Irrigation:

Hydrogen sulfide problems in agricultural irrigation. This summary shows how a system implemented by Hydroflo, Inc. in Washington State was able to solve problems with strong odors for upwards of 3 miles around the crop fields.

Landscape Irrigation

Landscape irrigation involves the use of reclaimed water for the watering of lawns, gardens, parks, cemeteries, etc. While the use of reclaimed water for landscape irrigation is similar to agricultural irrigation, there are some key differences. For the most part, agricultural systems are generally private places, with no public access. Places in the landscape irrigation category are almost always accessible by the public. It is for this reason that quality criteria for these projects are generally much higher than for agricultural irrigation. The grass will still grow with water of lesser quality than what is required, but the risk of human interaction is much higher in these cases. Reclaimed water also contains nutrients such as phosphorus and nitrogen that will make the use of fertilizers unnecessary.

Industrial Reuse

The main purpose of an industrial reuse system is usually a saving to the industry in their water and wastewater operations costs. There have been several different methods to reuse water within industry that have optimized system performance. Usually, the reuse systems in industry are highly site specific. The major uses for reclaimed industrial water include cooling water and boiler feed. Engineers have come to realize that it is not necessary to use water of extremely high quality for these purposes, as it is not necessary. Industrial water reclamation has enormous economic benefits to companies that use a lot of water. It is a step that every company should take in improving their operations efficiency.

A general example:

Some industries, especially the food and beverage and computer industries perform treatment on the incoming drinking water to remove extremely small impurities for specific manufacturing operations. The filters used to remove these impurities create a waste stream that is of a very high quality and can still be used for other plant operations.

Convincing industries to use reclaimed water is generally difficult because of concerns about public perception and operations cost. It has been found that most companies that implement reuse systems often save enough money to cover their capital costs in the first year of operation (Postel, 1992). Public perception is the most important and at the same time most difficult problem to solve.

Groundwater Recharge

There are several uses for our groundwater systems other than their use for our drinking water supply. Groundwater aquifers act as a protective barrier against salt-water intrusion. Without this barrier, out groundwater becomes saline, destroying agricultural soil as well as our drinking water supply. The most famous groundwater recharge system currently in use is located in Orange County, California. Water is treated to extremely high quality at Water Factory 21, and directly injected into the groundwater system, preventing seawater from intruding and to supplement California’s drinking water supply.

There are different ways to recharge groundwater aquifers. While Water Factory 21 has built a pipe into the ground to send the water directly into the aquifer, many places have surface spreading basins that basically consist of man-made ponds that are filled up and allowed to drain into the ground. Surface spreading systems generally require less stringent regulation on water quality than direct injection systems; they lose a lot more water because of evaporation.

By recharging our groundwater, we are also allowing water levels in our lakes to stay the same. It is important to realize that everything is connected to everything else in terms of our water resources. Therefore, if our groundwater resources are being reduced, our lakes are soon to follow.

Recreational/Environmental

Reclaimed water can be used for environmental purposes by replenishing streams and wetlands whose water table has fallen. Lakes and ponds can also be created with reclaimed water for swimming, fishing and other boating activities. Ski resorts that make their own snow can use reclaimed water at a smaller price.

We have actually been augmenting our environment with reclaimed water already, as all wastewater treatment plants need to discharge their effluents into the environment after treatment. This water forms the basis for many of our streams, creeks and rivers. While we in Canada do not consider this water reuse, there are actually places in Japan that have rebuilt dried up streams and rivers by discharging to their former river beds.

Nonpotable Urban uses

There are several things that could use reclaimed water within our cities and homes. Toilet and urinal flushing, fire fighting, air conditioning, and street cleaning are other nonpotable urban uses for reclaimed water. These systems do not need water of high quality for obvious reasons. The main constraint in terms of the implementation of reuse systems in this area is the fear of cross-contamination between drinking water and reclaimed water distribution lines. Even so, many places have found ways to make dual distribution systems work.

Toilet and urinal flushing seems to be one of the main uses for reclaimed water recently, especially in small-scale systems. The main problem with implementing urban reuse systems is that distribution systems are not easy to install throughout a city. The only way to put these systems in is to include them in the city planning process.

Case Studies in Nonpotable Urban Reuse:

The Shinjuku Project (Japan) - Nineteen high rise buildings in Japan have been retrofitted with a dual distribution system for toilet flushing.

Potable Reuse

The use of treated wastewater for the augmentation of our drinking water supplies requires the most advanced technologies to complete. There are several different options in reusing our wastewater, some of which we have been doing for decades without really giving it a potable reuse definition. When one city discharges their treated wastewater into a river, it is likely that another city downstream is going to pump this water out of the river, treat it, and use it for it’s drinking water supply. This is known as indirect potable reuse. Another example of indirect potable reuse is groundwater recharge. In this process, the wastewater is treated to a very high quality, and then sent through the ground into already existing groundwater aquifers. The water then flows through the soil, and is usually under ground for at least a year before it is pumped up and into the drinking water supply.

Direct potable reuse is by far the most advanced usage for reclaimed water. In these systems, water is treated to extremely high quality and then sent to the drinking water distribution system, and thus ‘completing the loop’ on our water distribution and collection systems. The only system that is currently operation directly using reclaimed water for potable uses is located in Windhoek, Namibia. Denver, Colorado created a direct potable reuse system for scientific research that is currently not in full operation because of the high costs associated with the amount of treatment necessary.

Case Studies in Direct Potable Reuse:

Windhoek, Namibia - The first direct potable reuse system in the world, and the only system currently being used. Namibia uses this reuse option to augment it's water supply in times of need.

Case Studies in Indirect Potable Reuse:

Water Factory 21 - Located in Orange County, California, this project is seen as the future of water reclamation technology by many. Started in 1976, the Orange County Water District has sent highly treated water into the ground, replenishing their groundwater supply and preventing seawater intrusion. Water that is not needed in the seawater barrier travels inland to water supply aquifers.

Please see the CMHC website for more case studies at:

http://www.cmhc-schl.gc.ca/en/imquaf/himu/wacon/wacon_012.cfm

Miscellaneous

The miscellaneous category involves all things that do not really fit into the other categories. These include construction uses such as concrete making, soil compaction and dust control, manufacture of ice for ice rinks, etc.

 

 

August 20, 2004

 

 

 



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