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Introduction to Water Recovery Systems

A water treatment investment is typically made for one of two reasons.  Most often it is due to stringent environmental standards.  Or, it may be a good corporate citizen who wants to do what's best for the environment.

Many businesses, small and large, are being required to make adjustments to their cleaning practices.  Although the Clean Water Act has existed for over 20 years, it has been only in the last 5-10 years that increased enforcement has created a growing market for point-of-use water recovery systems.

While recycling systems can remove suspended solids and FOG's (fats, oils and greases), they typically cannot eliminate contaminants such as leftover detergents, acid, alkalis and salts.  The sophistication of the state-of-the-art equipment to remove these contaminants makes such systems expensive and not user friendly.

For this reason, it is important to carefully monitor what is allowed to enter the system.  You can save yourself a lot of headaches by managing your waste streams.

Recovering water for reuse is often misunderstood.  Water is the "universal solvent".  It dissolves salt, coffee, sugar, iron, calcium, magnesium, etc.  It makes up the majority of what is in emulsions and homogenous mixtures such as milk, machine coolants, blood, perfume, Coca Cola, beer, etc.  It is used to leach out color from plants, clay, etc., for dyes.  It is used to make tea, soups from meat, beans, peas, corn, carrots, and potatoes to name a few.

So, as you can see, recovering water can be very difficult.  For example, if you wash out wheat and barley from a rusty old bin, you will get a beer-like substance with a higher-than-normal iron content.  Or if you wash an engine with hot water and use a very high-emulsifying degreaser, you can end up with a substance that looks like a machine coolant, which in itself is an emulsion (like milk).

Wash off a piece of golf course equipment and you have grass and pesticides to contend with.  If the grass stays in the water for very long, the chloroform leaches out of the grass, giving the water a green tint and the grass will mat together and ferment and create a manure-like smell.  Wash off wood chips and if they stay in the water too long, they will leach tannin creating a brownish water with a smell, and the smaller chips will become fibrous and mush-like, making them difficult to handle.

These are just a few examples of the problems challenging any water recovery system.  Unless the water is sent to a complete treatment plant, it is difficult to absolutely guarantee what quality or quantity of water that can be produced by any one type of water recovery system unless the effluent (dirty water) it has to clean, always stays the same.

There are basically three types of water recovery systems on the market today:

  • Mechanical Systems
  • Chemical Systems
  • Combination Systems

Mechanical: (This term broadly covers)

  • Cyclonic Separation
  • Straining
  • Filters of all types
  • Membrane Cleaning 
    • Reverse Osmosis 
    • Nano-Filtration 
    • Ultra
  • Coalescing
  • Diffused Air Floatation (DAF.)
  • Weirs
  • Floatation
  • Aeration
  • Carbon Adsorption
  • Media Absorption or Adsorption

Chemical: (This term loosely covers)

  • Flocculation
  • Acid Cracking
  • Masking
  • Oxidation
  • Separation
  • De-Ionization (D.I.)
  • Ozonation


No one of the water cleaning technologies offers a "silver bullet" for cleaning water.  For example, with chemical systems, a floc test can produce a vary clear sample of water, but is the sample usable?  In other words, will the residue from the floc used cause problems?  Will the effluent being flocked stay consistent?  The TDS (Total Dissolved Solids) will almost always be higher after a flocculant is used.  What are the economics (cost per gallon) to flocculate?

Mechanical Filtration also has limitations.  For example, cyclonic separation is very effective, "if" what is to be removed is a lot heavier than water.  But road film, flour, wood fiber, dust, etc., may not be heavy enough.  Using a fine filter without pre-filtration will plug (blind) the filter too quickly to be a practical solution by itself.  As an example, a 5 micron filter in front of an under-the-sink R.O. System, which gives you better drinking water, can foul as much as once a month, even when only processing five gallons per day of good clean drinking water.

The proper approach in selecting a system to apply to an application is to review the potential contaminants, decide on the quality of cleaned water required, determine the flow rates needed to meet the application and then select the filtration or chemical processes (more than one) that will provide the quality needed, at the flow rates required and be the most economical from a cost and maintenance standpoint.

The contamination removal charts in our technical section illustrate the different technologies that remove various contaminants from water.  Remember, however, that if there is more than one substance in the water, a technology aimed at removing a specific contaminant may be rendered ineffective by the added contaminant.  So, in order to design or select a water recovery system that is effective, the technologies used have to be lined up (staged) in such a way as to maximize their ability to remove a variety of contaminants in the proper order for the betterment of the entire system.  When studying a system for your needs, review the technologies used and see if they are aligned in a "common-sense" fashion.

A good, sound, generic "combination system" will typically combine 8 to 10 mechanical filtration methods with 2 or 3 uncomplicated chemical methods.  These technologies need to be properly staged in the flow sequence of the system to provide the best resulting water quality while minimizing the maintenance required.


For details contact Pan Pacific Environmental Group or email us from our Literature Request Page

Copyright 2009 Pan Pacific Environmental
Last modified: 02/10/09