Archive

Aquifer storage and recovery


photo 2Over the holidays there were a couple articles that came out about groundwater issues in the US, mostly from the declining water level perspective.  I also read a paper that suggested that rising sea level had a contribution from groundwater extraction, and of course USGS has maps of areas where the aquifer have collapsed as a result of overpumping.  In 2009 USGS published a report that showed a large areas across the country with this issue.  The problem is that of the 50,000 community water systems in the US, 500 serve over 50% of the population, and most of them are surface water plants.  There are over 40,000 groundwater systems, but most are under 500 customers.  Hence, groundwater is under represented at with the larger water associations because the large utilities are primarily surface water, while the small systems are groundwater. AWWA has difficulty reaching the small systems while RWA and NGWA reach out to them specifically.  But the small utility seems more oriented to finding and producing water and operating/maintaining/drilling wells than the bigger impact of groundwater use.  It is simply a matter of resources.  I ran a system like that in North Carolina, and just getting things done is a huge issue.  A couple of my medium size utility clients have the same problem.

The bigger picture may contain the largest risk.  Changing water supplies is a high cost item.  We have seen a couple examples (surface water) as a result of drought.  We saw Wichita Falls and Big Springs TX go the potable reuse route due to drought.  California is looking at lots of options. Both have had rain lately (Wichita Falls discontinued the potable reuse when the reservoir got to 4% of capacity).  Great, but someone is next.  Droughts come and go, and the questions is how to deal with them.

Groundwater supposedly is a drought-proof problem, but is it?  Groundwater has been a small utility solution, as it has been for agriculture.  But aquifer require recharge and water limited areas do not have recharge.  The result is a bigger problem – overpumping.  Throughout the west/southwest, Plains states, upper Midwest (WI, MN, IA), southeast (SC, NC), we see this issue.  Most of these areas have limited surface water so never developed much historically.  Rural electrification changes that because it made is easy to put in an electric pump to pull water out of the ground in areas that never had a lot of water on the surface, and hence were not farmed much. Pumps made is easier to farm productively, which led to towns. However, our means to assess recharge are not very good, especially for confined aquifers. The lowering water levels USGS and state agencies see is an indication that recharge is normally over estimated giving a false picture of water availability.  If your aquifer declines year after year, it is not drought – it is mining of the aquifer. You are sucking it dry like the eastern Carolinas did.  But, like many negative things, there is a lack of willingness to confront the overpumping issue in many areas. There are many states with a lack of regulations on groundwater pumping.  And I still think groundwater modeling use is limited to larger utilities, when smaller, rural systems may be most in need of it due to competing interests.

Concurrently, I think there is a tendency to oversell groundwater solutions (ASR, recharge), groundwater quality and the amount of available water (St George, UT).  Easy, cheap, limited treatment should not be the only selling point.  That leads to some curious decisions like some areas of California north of LA the utilities do not treat hard groundwater – then tell residents they cannot use softeners because of the salt in the wastewater prevents it from being used for reuse.  The reason they do not treat – cost, but it makes things difficult for residents.  The fact is we do not wish to confront is the realization that for many places, groundwater should probably be the backup plan only, not the primary source.

That leads to the question – what do we do about it when every politician’s goal is for their community to grow?  For every farmer to grow more crops?  But can they really grow sustainably?  DO we not reach a point where there are no more resources to use?  Or that the costs are too high?  Or that competition become unruly?  The growth and groundwater use ship is sailing, but in to many cases they do not see the rocks ahead.

Advertisements

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.


I have co-authored a new book for our senior design class sequence.  The book will be out in the early part of 2015.  Just in time for students to pick up a copy to help them with their capstone design class.  The book is titled Practical Concepts for Capstone Design Engineering and is published by JRoss Publishing.  We hope this will be useful for students, but it is not a book solely focused on the capstone class.  As this class was developed, the original intent was to construct it around the actual design process that consultants go through to deliver projects.  So the students start out with how to get work, the site selection, site planning and building planning processes, before they ever get to the design part.  That due diligence in necessary to insure that you have sorted out all the details that might impact your design.  As a result, we think that this may be a useful reference for professional, especially young professionals who want to know about site plans, floor plans, environmental site assessments, codes, green building, floor planning and communicating your vision.  Coming soon to Amazon.com.

At some point in early 2015, the AWWA manual M63 on aquifer storage and recovery will also be out.  It is the first AWWA manual devoted to the subject. Amazon.com or AWWA bookstore for that one.

 


My apologies for being off line for a couple weeks.  We finished the summer semester the first week of August, and are now gearing up for the Fall semester.  Lots to do, and proposals and other projects to complete before the plunge.  The most interesting project this summer has been the conclusion of a national survey of aquifer storage and recovery (ASR) projects.  The concept of ASR wells is to store water underground until you need it later.  If you have a utility with limited water supplies, or if you have high demands a certain part of the year but not the rest, ASR has been touted as a solution.  Storage underground eliminates the evaporation losses, but the question has always been can you get the water back.  The survey, which will be fully published next year, shows 204 sites.  It shows only about a third are operational projects and over 50 that have been functionally abandoned.  The reasons for abandoning them include metals leaching(mostly a Florida problem), the inability to recovery the water (particularly a problem in brackish aquifers), lack of capacity and trihalomethanes (a regulatory issue in a couple states).  ASR was successful with limited injection rates (700 gpm) and where the aquifer was denuddded (South Carolina).  Growth seems to be in the west after a lot of effort in the southeast.  The road forward should prove interesting.  With completion of the study it is hoped that more data can be gleaned to indicate the factors that make ASR project successful, thereby increasing the rate of success for the future. 


I went back to Colorado last week and it’s dry again out there.  Ok, maybe not this past week when it rained a bit, but despite late snow (March to May), the forests are dry.  The bark beetle problem has not made things easier, so lightning from thunderstorms can easily create fires, like the fire down in Colorado Springs or the Big Meadows fire that is ongoing in Rocky Mountain National Park.  The latter has been ongoing (although fortunately mostly out) for over a month, and has closed some trails in the park.  I hiked through the Fern Lake fire remnants (although virtually all the fire was around Cub Lake). That fire burned for a couple months last fall, only finally burned out in the winter after snowfall. 

 

The west is dry and “drier than in the past” is the new normal it seems in Colorado.  So now water managers are faced with three new challenges:  less water, faster runoff and more difficult water to treat.  The fires cause the loss of protective vegetation, which means less water is kept in the forest.  As a result, the tiny, light ash particles easily run off in the rain.  Ash is hard to remove without activated carbon or other advanced processes.  The loss of vegetation increases runoff, which means larger sediment content in otherwise pristine water supplies.  That can make a major impact on downstream water plants that may not have planned for such events.  The cost of fire suppression for the last 60 years confounds the current water supply and quality problems.  There are also ecological effects that may impact local economies. 

 

All this said, I am unsure what the solution is.  Clearly the climate in Colorado is changing.  It is unlikely we can alter the current course any time soon.  Instead we must adapt to the changes and attempt to mitigate the impacts on water supplies.  Creativity, innovation and likely more infrastructure will be required. Concepts like aquifer storage and recovery are coming back to the fore as a result of the current condition. It will be interesting to see how this all plays out. 

 

 

%d bloggers like this: