River Revival

Restoring a once-vital waterway with recycled wastewater

Laura_Sanchez_Blog

The Santa Cruz River once flowed year-round in Tucson, AZ, supporting one of the largest mesquite forests in the world.  But urban development and extensive groundwater withdrawals in recent years caused the river’s volume to dwindle. Today, city administrators hope to use recycled effluent to restore the river’s flow to historic levels and revive riparian habitats.

The water—up to 3.5 million gallons a day—will come from Pima County’s Agua Nueva Water Reclamation Facility. Pending permits, the city plans to utilize existing pipes, currently conveying recycled water for irrigation, and build a small treatment facility near the river to extract chlorine from the water prior to its release.

In addition to replenishing the river, the water will also augment groundwater by feeding the aquifer. The City of Tucson may then receive a 50% “recharge credit” from the state for every gallon it releases to the river. In the future, it can then withdraw half of what it has released into the aquifer to use in its drinking water system.

“We don’t have to do this. We could be putting it into our recharge basin where we get 100% credit,” Maya Teyechea, a hydrologist with Tucson Water, told Water Deeply. “But the intent is to have nice areas where people can enjoy the river—hopefully a nice riparian area.”

As recycled water gains acceptance as a means of boosting water supplies, more communities are finding ways to benefit from reuse. What are your thoughts on using recycled effluent for restoration projects such as this? WE_bug_web

Comments
  • tony biggens.

    will all traces of pharmaceuticals and other nano toxins be removed or will it bioaccumulate ?

    Reply
    • Edo McGowan.

      Tony, depending on soil type and a lot of other factors, xenobiotics can take a long time to break down. Archer, et al, looking at washwater from the decontamination of pesticide containers noted that degradation took months see: https://pubs.acs.org/doi/abs/10.1021/es60068a009?journalCode=esthag). Also, what else in the drainage is reaching the area? Arizona uses a lot of biosolids in its agriculture and this may represent a problem from being in the same drainage (see: https://www.ncbi.nlm.nih.gov/pubmed/15467791)
      With constant addition, some xenobiotics could build. One must also consider the development of biofilms which could be protective of microbes. Thus, it seems to come down to how much one wishes to spend on the technology and operational costs needed for removal of xenobiotics, whether or not the controlling governmental system considers the difference between “legal” vs “safe”, and if adequate lab analyses are done (keeping in mind that most current official tests don’t really tell you much) and above all, how well your immune system works.
      Consequently, an assumption that shifting into the use of recycled water, especially as a source of drinking water, will some how be buffered by a robust body of surveillance seems unrealistic.

      Example: At the 2006 at the Environmental Law Conference in Yosemite, various papers were delivered. Session # 27 was to contain some interesting insight into this area of non-action by regulators. The topic was pharmaceuticals in groundwater. Of particular interest was the analysis of the Safe Drinking Water Act by one of the US/ EPA drinking water toxicologists. His delivered paper ended with the following: ——–“ Bottom line on almost all of the “emerging” contaminants that have attracted attention: It will be a long time, if ever, before they are regulated under the SDWA.”
      See also generally Kenny and Furlong (ttps://www.ncbi.nlm.nih.gov/pubmed/16519291)

      Reply
  • Dr Edo McGowan.

    Laura, it is hoped that due consideration is given to the possibility that, unless extensively treated (not just tertiary) the effluent will be carrying copious amounts of antibiotic resistant bacteria and their genes as well as other pathogens. To the extent that this water makes an artificial wetlands, the migratory wild life can act as pathogen carriers, (see: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4323292/)

    Using previously vetted studies on what is in recycled and the failure of standardized lab tests to indicate contamination with pathogens, see Harwood and separately Fahrenfeld (https://www.ncbi.nlm.nih.gov/pubmed/15933017 and https://www.ncbi.nlm.nih.gov/pubmed/23755046)

    In its discussion on the uses of recycle water as a source for conversion to drinking water, the California expert panel noted:

    “Every community using reclaimed waters as drinking water should implement well-coordinated public health surveillance systems to document and possibly provide early warning of any adverse health events associated with the ingestion of reclaimed water….”

    The subject, as suggested by the expert panel, is taken yet further to broaden the scope beyond just the citizen’s community—-it is broadened to include the regulatory community.

    “Regulators approving IPR projects need also to implement a well-coordinated public health
    surveillance system to document possible warning signs of any adverse health events associated with the ingestion of recycled water.”

    “Existing surveillance systems, such as those for notifiable communicable diseases, should be used and/or enhanced to meet these needs. Surveillance systems must be jointly planned and operated by health departments, water utilities, and other relevant agencies. Key individuals in each agency need to be appointed to coordinate planning and rehearse emergency procedures. The surveillance plan, its purpose, the monitoring results, and the system process performance should be available to the community and interested stakeholders.”

    The discussion continues:

    “Surveillance systems may indicate whether an epidemiological study is required. However, epidemiological surveillance is considered relatively slow and is reactive as it is based on disease outcomes.”

    It would be interesting to see if Arizona’s proponents had developed any kind of public health surveillance system.
    Dr Edo McGowan

    Reply
  • jeff radics.

    I can only wonder when these water starved western cities will realize that they do not have enough water to sustain themselves and simply put a halt to building permits, Water is essential to life, human and otherwise. in a desert climate it is scarce so human inhabitation should be too.

    Reply

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