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How does our nitrate removal system differ from reverse osmosis (RO) systems?

March 23, 2019

Reverse osmosis (RO) systems are the workhorse of the drinking water purification market.  They are extremely effective in separating water impurities above a certain size (molecules or particles slightly large than a water molecule are filtered or removed).  So,  does RO eliminate or reduce nitrate?  The answer is no.  Some RO membranes will remove the nitrate molecule from the incoming water and release it in the waste stream  or concentrate flow.   This means that if you had 50 gallons per minute of incoming flow at 50 mg/L of nitrate-nitrogen in your drinking water,  your RO system would produce about 25 gallons per minute of potable water with very low nitrate but also 25 gallons of per minute of concentrate with a nitrate concentration of nearly 2X or 100 mg/L of nitrate.  This concentrate would be 10X the legal limit of 10 mg/L.  

 

Some installations of RO system will be permitted to send this concentrated nitrate waste to a sewer line,  where it eventually ends up a water treatment plant.  However, in more rural and agricultural areas this concentrated waste stream presents a major regulatory issue.  Water regulators in California will not give you a permit to just dump this nitrate concentrate on the ground or apply it to fallow ground.

 

This means that if your drinking water well supplying your community or ranch becomes contaminated with high levels of nitrate, it is very likely that you will not get a permit to use and RO based solution unless you are willing to pay to haul away the RO nitrate rich concentrate.  

 

RO systems require very high water pressure to operate.  This comes at a price of substantial energy costs.  By contrast,  our design only requires enough energy to pump the water up approximate 10 feet of static head or static discharge head. See the excellent article in Pumps and Systems magazine for an explanation of static head- https://www.pumpsandsystems.com/topics/pumps/characteristics-centrifugal-pumps-0912.  This low pressure advantage has other benefits for Tailwater.  The low pressure allows us to use much lower cost materials and fittings to move the waste water.  Installation and maintenance costs are also much lower and simpler.

 

RO systems cannot tolerate high levels of salts and carbonate, always found in agriculture runoff or drainage.  These materials will foul the pores of the membrane quickly,  dramatically lowering throughput.  For this reason,  RO systems generally require a very substantial investment in pre-treatment to eliminate these scalants and other chemicals,  dramatically increase the cost and complexity of the RO installation.  By comparison,  Tailwater's nitrate removal system is immune to salt, carbonate,  dirt, silt, and any number of other waste water contaminants.  In most installations- no pretreatment is required.

 

Using this simple comparison one can see that there are possible benefits to using a Tailwater nitrate removal systems and an RO system for drinking water applications.  If you have one or more nitrate contaminated wells supporting your ranch,  you can use the Tailwater system to denitrify the well water at the source and then send the denitrified water onto your RO system for drinking water use for the property, process, and your workers.

 

An alternative implementation is to use our nitrate removal system to treat the RO concentrate system.  Using the example from the first paragraph,  we can quickly see that treating RO concentrate would require system 1/2 the size of treating water at the source.  Since the concentrate stream exiting the RO system is at very high pressure and flow,  this energy can be used to move the water to our nitrate removal system, saving money and reducing complexity.

 

To learn more abut how Tailwater can solve your drinking water nitrate problems,  contact us.

 

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