Indirect and Potable Reuse Future?
2014 is almost over. Hard to believe. I have been attending or annual Florida Section AWWA conference, meeting up with old friends, making new ones and learning new things. Conferences and connections allow us to do our jobs more efficiently because as we learn how to solve problems or where we can find a means to solve whatever problem we encounter. It is a valuable experience that I encourage everyone to get involved with, especially young people who need to make connections to improve their careers. The technical sessions seemed to be well received and popular. That means that there are issues that people want to hear about. Things we focused on were alternative water supplies, water distribution piping issues, disinfection byproducts, ASR and reuse projects.
The reuse projects focused on Florida efforts to deal with 40 years of reuse practice and a movement toward indirect potable reuse. This is the concept where we treat wastewater to a standard whereby it can be put into a waterway upstream of a water supply intake or into the aquifer upstream of wells. The discussion was extended to a number of discussions about water shortages and solutions for water limited areas. Florida averages 50-60 inches of rain per year as opposed to the 6-10 inches in areas of the southwest or even 15-20 inches in the Rockies which makes the concept of water limitations seem a bit ludicrous for many, but we rely on groundwater that is recharged by this rainfall for most of our supplies, a lack of topography for storage and definitive wet and dry seasons that do not coincide with use.
The situation is distinctly different in much of the US that relies on surface waters or is just plain water limited. We have a severe multi-year drought going on in California and huge amounts of groundwater being used for irrigation in many rain-challenged areas. That is what all those crop-circles are as you fly over the Plains states and the wet. Where you see crop circles, think unsustainable water supplies. They are unsustainable because there is no surface water and the recharge for these aquifers is very limited. Most leakance factors in aquifers is over estimated and hence water levels decline year after year. Water limited places need answers because agriculture often out-competes water utilities, so in the worst of those areas, there are discussions about direct potable reuse (which occurs in Texas).
Direct and indirect potable reuse are offered as answers which is why this topic was popular at our conference. A recent 60 Minutes presentation included a tour and discussion of the Orange County Groundwater Replenishment program, where wastewater is treated and injected into the ground for recovery by wells nearer to the coast. They discussed the process (reverse osmosis, ultraviolet light and peroxide) and they took a drink. “Tastes like water” was Leslie Stahl’s comment – not sure what she expected it to taste like, but it provides a glimpse into the challenge faced by water utilities in expanding water supplies. Orange County has been injecting water for many years into this indirect potable reuse project. The West Coast Basin Barrier Project and several others in California have similar projects. South Florida has tested this concept 5 times, including one by my university, but no projects have yet been installed.
But until recently, there were no direct potable reuse projects where wastewater is directly connected to the water plant. But now we have two – both in Texas with a number of potential new projects in the pipeline. Drought, growth, water competition have all aligned to verify that there many are areas that really do not have water, and what water they do have is over allocated. A 50 year plan to manage an aquifer (i.e.. to drain it) is not a sustainable plan because there may not be other options. But Texas is not alone. Arizona, Nevada, New Mexico, Utah, Colorado, The Dakotas, Kansas Oklahoma and I am sure others have verified water limitations and realize that sustainable economic activity is intrinsically linked to sustainable water supplies. Conservation only goes so far and in many of these places, conservation may be hitting its limits. Where your rainfall is limited and/or your aquifer is deep, replenishable resource is not always in the quantities necessary for economic sustainability. Water supplies and economic activity are clearly linked.
So the unimaginable, has become the imaginable, and we now have direct potable reuse of wastewater. Fortunately we have the technology – it is not cheap, but we have demonstrated that the reverse osmosis/ultraviolet light/advanced oxidation (RO/UV/AOP) process will resolve the critical contaminant issues (for more information we have a paper we published on this). From an operational perspective, RO membranes, UV and chemical feeds for AOP are easy to operate, but there are questions about how we insure that the quality is maintained. The technical issues for treatment are well established. Monitoring is a bit more challenging – the question is what to monitor and how often, but even this can be overcome with redundancy and overdosing UV.
But drinking poop-water? The sell to the public is much more difficult. It is far easier to sell communities without water on the idea, but the reality we need to plan ahead. There are no rules. There are no monitoring requirements, but we MUST insure the public that the DPR water they are drinking is safe. WE are gaining data in Texas. California and Texas are talking about regulations. The University of Miami has been working of a project where they have created a portion of a dorm that makes its own water from wastewater. Results to come, but the endeavor shows promise.