Impacts on the Environment
The environmental impacts of water reuse are complex, and very dependent on the type of system that is being employed. While some cases of water reclamation are clear cut, being obvious that water quality is actually benefiting from the practice, some are not as easy to justify.
The implementation of water reuse in the City of Guelph is different in many respects from many of the projects that already exist. There are major differences that make the reuse of water in the city difficult to implement. This does not by any means make the water reuse practices unnecessary, since water is a not a fully renewable resource. Reusing our water is a key step in working towards sustainable living, and working towards the most efficient means of using water.
The key differences between the City of Guelph and most water reusers are as follows. First of all, Guelph is located in a place that is by no means running out of water. Canada has plenty of water resources, and for this reason, has not made a very strong effort at reusing its water. In fact, in researching water reuse in Canada, the only website that contains any information about water reuse in Canada is the Canada Mortgage and Housing Corporation, which has funded a bunch of projects that can be looked at in the Canada section of this website. The reuse of water is extremely political, and this comes back to the issue of choice (see CSIRO public perception summary). Most places that are reusing water have no other choice. They are either completely out of water, or realize that if the right steps aren’t taken, they will be soon (California is a prime example).
The second unique quality of the City of Guelph is that it does not discharge its existing wastewater effluent to the ocean. While other inland cities are slowly beginning to regard water reuse as a needed practice, it seems as though cities near the oceans seem to be the first to reuse their water. This does make sense, since groundwater is so much more sensitive in these areas. A major motivation to reuse water is that it drastically reduces the amount of water needed to be extracted from the environment. California has recognized this, and has saved its groundwater supply in doing so. If the State of California had waited much longer to implement these reuse practices, it is quite likely (depending on how long they had waited) that seawater would have intruded into existing potable aquifers. At this point, desalination would be the only option available. For more information on California, please see the Recyled Water Task Force Final Report.
In looking at the impact on groundwater quality, there is no doubt that water reuse in coastal regions is likely to drastically improve what would have been if normal extraction and disposal into the ocean would have continued. Once seawater intrusion barriers are broken, groundwater goes saline, and can no longer be used for drinking without expensive desalination practices. Another problem with this is the detrimental effect of salt on the soil.
While salt contamination can come through over-extraction of groundwater resources, in inland places such as Guelph, this contamination can come through possible water reuse systems, and should be investigated. Salt is difficult to remove in wastewater processes because of its relative particle size (extremely small). If there salt in water that is being used to irrigate crops, it is possible that over time this salt can accumulate and contaminate the soil.
While water reuse limits the amount of water taken from certain locations, it is also important to note that in many locations, these supply sources are no longer being replenished by treatment plant effluents. This can be a good thing, since treated wastewater is not generally of as high a quality as the water already in the river (or other discharge location). It is also important to realize that some places (such as the City of Guelph) extract their water from a groundwater source, and discharge to a surface water source. This surface water source may depend on this treated effluent to sustain itself. In fact, one reuse project in Japan sent treated wastewater into a stream that had dried up because of over-extraction for drinking water supplies. (Ogoshi, Suzuki, & Asano, 2001) It is therefore important to determine how much water can be extracted from the water without causing it to dry up.
The environmental impacts of water reuse in Guelph are currently being studied by the Grand River Conservation Authority.
Anderson, M. Information on environmental impacts of guelph reuse.(Personal Communication)
A nderson, J. (2003). The environmental benefits of water recycling and reuse. Water Science and Technology: Water Supply, 3(4), 1-10.
Beltrán, J. M. (1999). Irrigation with saline water: benefits and environmental impact. Agricultural Water Management, 40(2-3), 183-194.
Ogoshi, M., Suzuki, Y., & Asano, T. (2001). Water reuse in japan. Water Science and Technology, 43(10), 17-23.
US EPA. (2001). Water recycling and reuse: the environmental benefits. US EPA.