Let’s start this discussion by going over the two primary types of reuse. The first and most common is indirect reuse. Indirect reuse occurs when wastewater (in the US this is typically treated to a high level) is discharged to a stream or lake. The mixed water then flows downstream where someone pulls is back out for drinking water. What is different today is that indirect reuse now includes now includes injecting treated wastewater into groundwater sources and removing mixed wastewater and river water from the stream and pumping back upstream to a lake where it eventually becomes the raw water for a water treatment system. Direct Reuse is when treated wastewater is used for a beneficial use without first mixing with natural waters. This commonly used for irrigation of golf courses, playing fields, cooling towers, hydraulic fracturing and other creative uses. This is the most cost-effective reuse method since it does not need the extra pumping and treatment needed for indirect reuse. This article will focus on some of the issues associated with indirect reuse since it often the method that raises the most concern since the wastewater becomes part of the potable water source water.
If your source water is from a lake or river, you have probably already been drinking some reclaimed water. Many water intakes are downstream of at least one wastewater treatment plant discharge point. This type of indirect reuse has been occurring for hundreds of years. Natural surface waters already contain large amounts of bacteria and virus originating from wildlife, domesticated animals, birds and humans. In areas with good wastewater treatment, pathogens originating from humans is typically low with the main source being wildlife, birds and pets.
One study you may want to look at is the Final Draft Technical Support Document Segments 0806, 0841, 0822, and 0805 of the Trinity River Bacteria TMDL, January 2008. TMDL is Total Maximum Daily Load and represents the maximum amount of a pollutant that the stream can receive without exceeding a given water quality standard. As part of this study, Bacterial Source Tracking (BST) was performed on E. coli strains to identify the source of bacteria in the stream segments. The BST process considers genetic and biochemical tests to identify the host animal. A summary of the results for Segment 0806 are shown in the following table. This data is taken from Table 3–3 of the TMDL report.
This data shows just how efficient water treatment systems in the US are in removing pathogens. Most pathogens are naturally occurring in source waters and would be around even if we humans were not around. Pathogen reduction was the primary goal of the early water treatment systems, and the process has become highly advanced and reliable over the last 150 years. Except for pristine waters, the relatively small amount of pathogens added to water supplies from wastewater is a minor concern.
Another concern is the accumulation of chemicals in the water supply. Chemicals washed into the streams from urban and agricultural storm water runoff as well as discharges from industrial and municipal wastewater plants can accumulate in water supplies and bio-accumulate in aquatic animals. Pharmaceuticals and personal care products are also a growing concern. These enter the water cycle by passing through the body or being disposed down sinks and toilets. With indirect reuse, a portion of the wastewater is recycled back into the water supply, which could lead to higher concentrations of these contaminants. For more information, visit EPA’s website Pharmaceuticals and Personal Care Products (PPCPs) in Water.
Many, but not all, of these chemicals are regulated by the EPA and states in the drinking water; therefore, there is typically little concern these regulated chemicals will become a problem. For those chemicals that are not regulated, the water utility will often perform broad spectrum analytical tests to check whether there are other chemicals present that may pose concern.
Typically, wastewater has a higher salt content than the lakes and streams. As the percentage of water in a lake that originates from wastewater increases the salt content can rise. This is easily monitored in both the treated wastewater and the lakes. High salt levels are more difficult to treat and can change the taste of the water. Water utilities typically watch this carefully and will limit the recycling of the wastewater if the salt levels begin to rise.
Another practice the water utilities typically use to treat the wastewater that is recycled is nutrient removal. High ammonia and phosphorus levels can lead to algal blooms in lakes and slow-moving streams. Algal blooms can kill aquatic life and create significant taste and odor problems in the drinking water. Recycled water is often treated to a higher level to reduce these nutrients since algal blooms are hard to control in the lakes.
If recycled water is coming to your town, get involved, ask questions, go to public meetings and educate yourself. As you consider the prudence of using recycled water in your area, consider the following issues.
- Why does your community need to recycle the water? Typically, this is due to drought and other water resource limitations. Maybe the same people fighting reuse are also fighting construction of that new lake. If a community does not have abundant water, it will not grow.
- Executives for the water utilities often live in the service area. They will be drinking the same water and using it in their homes. They are having to do the best they can with limited resources and money.
- Conservation can help to some extent. Make sure the utility has a good conservation plan and become a champion in your neighborhood. If the lakes stay full, there will be no need to recycle the water.
- Ask the water utility for informational material. Visit the Sustainable Solutions for a Thirsty Planet website and find out more.
- Attend the public meetings and volunteer to be a part of steering committees.
- Ask the water utility public relations person to come present to your church, group or organization. They are passionate about water and typically enjoy the invitations.
No matter if your community uses recycled water, we typically recommend each home have a water filter. See our post What type of water filter do should I get for my home? for information on these systems.