Archive

indirect potable reuse


DSCF0032Curtailed water use and conservation are common topics of conversation in areas with water supplies limitations.  As drought conditions worsen, the need for action increases, so when creating a regulatory framework, or when trying to measure water use efficiency, water supply managers often look for easily applied metrics to determine where water use can be curtailed.  Unfortunately, the one-size-fits-all mentality comes with a potential price of failing to fully grasp the consequences decision-making based on such metrics.

One of the issues that water supply regulator like to use is per capita water use.  Per capital water use is often used to show where there is “wasted” water use, such as excessive irrigation.  However such a metric may not be truly applicable depending on other economic factors, and may even penalize successful communities with diverse economic bases.  A heavy industrial area or dense downtown commercial center may add to apparent per capita use, but is actually the result of vibrant economic activity. Large employment centers tend to have higher per capital use than their neighbors as a result of attracting employees to downtown, which are not included in the population.

In south Florida, a recent project I was involved with with one of my students showed that while there was significant variability among utilities, but the general trend of increased economic activity was related to increased per capita use.  Among the significant actors were health care, retail trade, food service and scientific and technical services.  It appears to be these sectors that drive water use upward.  As a result when evaluating the efficiency of a utility, an analysis should be conducted on the economic sectors to insure that water regulations do not stifle economic growth and jobs in a community.   And conversely if you do not have these sectors, you water use should be lower.  Something to think about when projecting or regulating water use.  Limited water use may in fact be limiting economic activity in the area. Of course if you are water limited, limited new withdrawals may be perfectly acceptable if you want to encourage other options, like direct or indirect potable reuse, irrigation, etc.  

It would be interesting to expand this study across the country to see what the national trends look like and how different tourism oriented South Florida might actually be.

Advertisements

In the last blog I showed what reclaimed wastewater could do for an ecosystem.  Very cool.  But what about for drinking water.  I actually was involved in an indirect potable reuse project several years ago.  The concept was to take wastewater, filter it with sand filters, filter it with microfiltration, reverse osmosis and then hydrogen peroxide and ultraviolet light.  This is what they do in Orange County California when they recharge groundwater, and have been for over 30 years.  Epidemiological studies in the 1990s indicated no increased incidence of disease when that water was withdrawn from the aquifer, and then treated in a drinking water plant before distribution.  So our project was similar – recharge to the Biscayne aquifer in south Florida.   It worked for us.  Total phosphorous was below 10 ppb, TDS was less than 3 mg/L (<1 after RO), and we were able to show 3 log removal of endocrine disruption compounds an d pharmaceuticals.  It worked well.  This is a concept in practice in California.  And will be at some point in south Florida since only the Biscayne aquifer provides sustainable water supplies.  Here is what our system looked like.

IMG_3100

sand filters

IMG_3106

microfiltration

IMG_3085

Reverse osmosis

IMG_3152

ultraviolet/peroxide

This is also the same basic concept Big Springs Texas uses for their direct potable program, demonstrating that the technology is present to treat the water.  A means for continuous monitoring is lacking, but Orange County demonstrates that for indirect potable reuse projects, a well operated plant will not risk the public health.  This is how we do it safely.

 


A past project I was involved  with involved a look at the feasibility of using wastewater to recharge the Biscayne aquifer In the vicinity of a utility’s potable water supply wells.  The utility was feeling the effects of restrictions on added water supplies, while their wastewater basically unused.  So they wanted a test to see if the wastewater could be cleaned up enough to pump it in the ground for recovery downstream, with the intent of getting added allocations of raw water.  Assuming the water quality issues could be resolved, the increased recovery would solve a number of water resource issues for them, and the cost was not nearly as high as some thought.

So we tested and using sand filters, microfiltration, reverse osmosis, peroxide and ultraviolet light, we were successful in meeting all regulatory criteria for water quality.  The water produced was basically pure water – not constituents in it, and therefore it exceeded all drinking water standards.  We demonstrated that technologically the water CAN be cleaned up.  The only issue is insurance that the treatment will always work – hence multiple barriers and the ground.  This was an indirect potable reuse project and ended because of the 2008 recession and the inability to of current water supply rules to deal with the in/out recovery issues.

The indirect reuse part was the pumping of the water into the ground for later withdrawal as raw water to feed a water treatment plant, as opposed to piping it directly to the head of their water plant.   But recovery of the water can be a challenge and there is a risk that a portion of the injected water is lost.  In severely water limited environments, loss of the supply may not be an acceptable outcome.  Places like Wichita Falls, Texas have instead pursued more aggressive projects that skip the pumping to the ground and go straight into the water plant as raw water.  Technologically the water CAN be treated so it is safe to drink.  The water plant is simply more treatment (added barriers).  So, with direct potable projects, monitoring water quality on a continuous basis maybe the greatest operational challenge, but technologically there is no problem as we demonstrated in our project.

The problem is the public.  You can hear it already – we are drinking “pee” or “poop water” or “drinking toilet water.”  The public relations tasks is a much bigger challenge because those opposed to indirect and direct potable projects can easily make scary public statements.   Overcoming the public relations issue is a problem, but what utilities often fail to convey is that many surface waters are a consolidations of a series of waste flows – agriculture, wastewater plants, etc. by the time they reach the downstream water intake.  Upstream wastewater plants discharge to downstream users.   But the public does not see the connection between upstream discharges and downstream intakes even where laws are in effect that actually require the return of wastewater to support streamflow.  So are rivers not also indirect reuse projects? In truth we have been doing indirect potable reuse for, well ever.

We have relied on conventional water plants for 100+ years to treat surface waters to make the water drinkable.  The problem is we have never educated the public on what the raw waters sources were, and how effective treatment is.  Rather we let the political pundits and others discuss concerns with chemicals like fluoride and chlorine being added to the water as opposed the change in water quality created by treatment plants and the benefits gained by disinfectants.  That message is lost today.  We also ignore the fact that the number one greatest health improvement practice in the 20th century was the introduction of chlorine to water.  Greater than all other medical and vaccine advances (although penicillin and polio vaccines might be a distant second and third above others).   Somehow that fact gets lost in the clutter.

Already the Water Reuse Association and Water Research Foundations have funded 26 projects on direct potable reuse.  Communicating risk is one of the projects.  The reason is to get in front of the issues.  You see, playing defense in football is great and you can sometimes win championships with a good defense (maybe a historically great one, but even they gamble).  Defense does not work that way in public relations.  Offense usually wins. Defenses often crumble or take years to grab hold.

The failure of utilities to play offense, and the failure of elected officials particularly support playing offense is part of the reason we struggle for funds to make upgrades in infrastructure, to perform enough maintenance or to gather sufficient reserves to protect the enterprise today.  And it remains a barrier to tomorrow.   Leadership is what is missing.  It struck me that when looking at leaders, what made them leaders was their ability to facilitate change.  Hence President Obama’s campaign slogan.  But talking about change and making real changes are a little more challenging (as he has seen).  You cannot lead without a good offense, one that conveys the message to the public and one that gets buy-in.  With direct and indirect potable reuse, the water industry has not changed the perception of “toilet water.”  That needs to change.  We need to be frank with our customers.  Their water IS SAFE to drink.  They do not need filters, RO systems, softeners, etc., or buy bottled water, when connected to potable water supplies (private wells, maybe).  We CAN treat wastewater to make it safe, and the technology tis available to make it potable.  . The value they pay for water is low.  Yet in all cases, others, have made in-roads to counter to the industry.  That happened because we play defense.


The number of people that recall the Dust Bowl of the 1930s is dwindling and that may portend poorly for society (likewise the loss of Depression memories and two world wars).  The Dust Bowl was aptly names for the regular storms of windblown dust that pummeled farm fields and blew away valuable topsoil needed by farmers.  Why it occurred was more interesting and foretelling.

The amount of farming had exploded in the late 1920s as a result of  record wheat price, motorized tractors and government programs encouraging farmers to plow up the prairie and plant.  The crops replacing the native plants did not have the same root structure and were less drought tolerant as a result.  When wheat prices collapsed, the fields were left fallow exposing the topsoil to the elements.  Since the topsoil was no longer anchored to the soil by plants, the wind and lack of rain caused much of the topsoil to migrate with the wind as dust.  Topsoil was lost, rain ran off, transpiration decreased, and the cycle just go worse.   Up to 75% of he topsoil was lost.

Rains returned in the 1940s but much of the dry farming (no irrigation) practice was immediately converted to wet framing using deep wells to capture water from aquifers.  The result was healthier crops, more consistent yields and protection of the remaining topsoil as a result.  Or is it?

Visit California today.  They are in the midst of severe drought conditions. Farmers have attempted to protect themselves by drilling more wells – deeper wells which diminish water supplies to the shallower neighboring wells.  Water levels decline, land subsides, the aquifer collapses, and there is little recharge.  Some areas of the central valley have sunk over 8 feet in the past 100 years.  But we have up until this point, had healthier crops and more productive yields, which protects the valley until the rains return.  Or does it?

While the lack of rainfall is a natural cycle, there is an argument to be made that man-made impacts have exacerbated the situation.  In the Dust Bowl states, the initial error was plowing up the native grasses without understanding how they had adapted to the mostly dry conditions on the prairie.  Many of the prairie states receive under 20 inches or rain each year, and scarcely any during the summer, which limited evapotranspiration, which limits thunderstorm and regional rainfall activity.  Less ET = drier conditions.  So growing crops is not what one would immediately identify and a “normal” land use for the prairie.  We altered the environment, but the Midwestern farming thought process doesn’t work in the dry prairie.  Irrigation was needed, but the lack of surface water limited irrigation unless wells are used.  Wells were drilled which returned and improved crop yields, but the well use has caused massive decreases in aquifer levels in the prairie states. The amount of water is finite, so as long as withdrawal exceed recharge, and with only 20 inches of rain that mostly runs off the land, there is a point in time when the well runs dry.  As the well runs drier, productivity will fall.  The interim fix is drill deeper, but the bottom of the aquifer is in sight.  Then, fields will be fallow, agriculture will be impacted dramatically, and it is not inconceivable the Dust Bowl type conditions could reoccur. Policies by man exacerbate the problem because the prairie productivity is accelerated will above its natural condition.

Likewise much of the land subsidence problem in California is irrigation driven – water is pulled through wells in an ever increasing competition to maintain one’s crop yield.  Water wars and fights with one’s neighbors over wells drying up is increasing more common as irrigation needs increase and recharge to the aquifer is diminished.  Much of California is even drier than the Dust Bowl states, and more reliant or wells and irrigation.  Less water also means less ET which means less local rainfall.  So while California has done much to protect itself over the years from drought, the current experience says that declining aquifer levels means we have exceeded the productivity of that state as well.  So is the California Dust Bowl coming?

Man is an ingenious creature.  We overcome much that the Earth throws at us.  But at the same time, we rarely consider the consequences of our actions in overcoming the challenges Earth poses.  These two examples show how our efforts to solve one problem, may actually damage the long term sustainability of these areas.  Short term gain, long term problem.


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.

%d bloggers like this: