What is Reuse of Wastewater for Indirect Drinking Water Use?

The scarcity of available drinking (potable) water has forced water agencies to look for innovated ways of finding new sources of drinking water for its customers. Because new water can’t be created, the concept of using recycled water is quickly becoming more common place. The California Agricultural Water Stewardship Initiative notes that recycled water projects have more than doubled since 1987 and continues to follow an upward trend. Identified and delivered by purple pipes, recycled water is often labeled with warnings of, “Do Not Drink” and “Non-Potable Water.” But if recycled water isn’t supposed to be for drinking, then how can recycled water be a source of clean drinking water?

Purple Pipe on Grass Horizontal

Let’s start with the question of, “What exactly is recycled water and what purpose does it serve?” The answer comes from years of innovative thinking in hopes to find solutions for water-stressed regions. The California Association of Sanitation Agencies (CASA) defines recycled water as “municipal wastewater which, as a result of specified treatment, is suitable for a beneficial use.” Essentially, wastewater enters a treatment process that allows for it to be used again without going through the natural water cycle. Therefore, the volume of the treated wastewater is more predictable and available during a more immediate timeframe. According to CASA recycled water is, “One of the only reliable, sustainable and drought-proof sources of new water to meet California’s needs.” Recycled water essentially creates a new source of water. Can this water be used for drinking?

Implementing recycled water systems in service areas has had many challenges, including the public perceptions of its uses in relation to drinking water. One negative perception includes the idea that customers would be drinking recycled wastewater from their faucets. Although recycled water is used to benefit the population for outdoor irrigation uses, regulations in California do not permit  direct consumption for potable use This means we can’t drink recycled water  right after it leaves the treatment plant. More simply put, it cannot be used to for drinking, cooking, or showering purposes. Instead, it is currently approved for ‘non-potable’ uses, non-drinking/ human uses. But even for these uses, a high degree of treatment is conducted by local wastewater treatment agencies that must meet accepted state and federal water quality standards before delivery and use of recycled water.

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The difference between potable and non-potable water is potable water has been designated for safe direct consumption by the Occupational Safety and Health Administration, among other agencies and requirements. However, the specifications do not exclude non-potable water (not intended for drinking) from serving water districts and its consumers in a positive manner. Instead, recycled water not intended for direct consumption can be used for “irrigation, such as turf and landscaping, agricultural uses, dust control and industrial cooling.” Crops using recycled water provide the much needed water resources to help harvests grow. Many of those crops are then used at some point for either animal or human consumptions, which are a  byproduct of recycled waters use.

Another use of recycled water is to recharge groundwater aquifers and to prevent seawater intrusion into underground drinking supplies. Treatment levels of the recycled water vary from primary, secondary, and tertiary treatment methods. Recycled water that is used to supplement or recharge groundwater aquifers must employ greater levels of treatment to ensure its quality and safety. The indirect potable reuse of wastewater isn’t directly consumed by people. Instead, it is pumped to groundwater basins for recharge where it passes through yet another natural filtering process of treatment. That water will eventually make it’s way to wells used to deliver water  for consumption. According to the California State Water Board, “regulations specify the percentage of recycled water that can be added, how long it must reside in a basin and the distance from adjoining potable well supplies before it can be merged with other natural groundwater sources used for  drinking water.” Due to the nature of the process, this type of use of recycled water is considered indirect water consumption.

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A large focus of many Southern California water agencies is to increase local water supply and to decrease its reliance on imported sources. Pursing these projects helps alleviate some of the challenges that California has experienced over the last years, The California Agricultural Water Stewardship Initiative outlines the benefits as:

  1. Reducing water pollutions
  2. Augmenting water supply
  3. Supporting healthy ecosystems; and
  4. Reducing water energy requirements and costs

Innovative solutions, such as using recycled water for indirect consumption, will continue to strengthen California’s water districts ability to deliver consistent, reliable, and safe water for its consumers.

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