Water Reuse From Wastewater Using RO

Often we are asked to help with water re-use project.  From their research, prospective customers are often interested in using an RO system.  They want to take advantage of the key features which make RO a great technology for treating water entering their plant for process applications:

• The RO membrane is barrier between the treated and untreated water
• Reverse osmosis reduces the TDS (Total Dissolved Solids)
• RO systems and membranes are a robust, proven technology

These advantages have been quantified and defined when an RO system is desalinating water and treating municipal/well water.  More information is required before any RO is placed on a process waste stream.  Often a pilot is required.  Our parent company, Ecolab, has extensive experience with water treatment and reuse applications, but more information than a standard water test is needed to determine whether RO has a chance of working.

When looking at a water re-use project from wastewater, regardless of where the water re-use potential location is, it is essential that the water quality is considered both from a physical /chemical perspective but also from a biological perspective. What that means is analysis for parameters such as BOD / COD,( Biological Oxygen Demand / Chemical Oxygen Demand), turbidity , FOG ( Fats, Oils & Grease), NH3 /TKN ,( ammonia /total Kjeldahl nitrogen), NO3 and Total P as well as TSS ( Total Suspended Solids ) and conductivity or TDS( Total Dissolved Solids) should be added to the more typical water analysis list.  If your facility is a food and beverage plant, a microbiological assay should be done.

NOTE- most of these tests require special sampling methods and handling.  The WHO (World Health Organization) has an excellent paper on the subject "Water Quality Monitoring - A Practical Guide to the Design and Implementation of Freshwater Quality Studies and Monitoring Programmes".  Look at pages 17-18.

Additional Information:
Definition of Waste water quality parameters
The Kjeldahl test method used to determine the nitrogen concentration in a waste stream
Standard Methods For the Examination Of Water and Wastewater

I Can't Believe It's Not A Water Sample!

Holy Moses! It wasn't 1 week after my last blog on October 28th 2011 about receiving water sample in old pickle jars when I get a water sample in an used margarine container!

Water Sample Container Received by Res-Kem

P-L-E-A-S-E!. My disclaimer: "results not guaranteed for accuracy due to improper sampling container" Ok, the courtesy testing we do is of the non-critical, aesthetics only variety, however, I'm sure the old butter will skew my results. Now that the blue is leaving my face, please help a friend out and read my October 28th 2011 blog. Matter of fact, print it out and keep it in your shirt pocket or maybe tape it to the back door of your work van. Amen.

"Toxic Waters" Article From The New York Times

An excellent article on water quality in the United States entitled "Toxic Waters" , was published by the NY Times on December 16, 2009. The premise of the article is that just because a water is "legal" it may not be "healthy". Our policy is not to be a fear monger, but the article was very concerning.

A very interesting part of this article was the water quality data for each State. The amount of data is mind boggling! The data was collected and analysed by the Environmental Working Group who shared it with The New York Times.

Water Analysis Article

I came across an excellent article in an old issue of Water Conditioning & Purification magazine entitled "Making Sense of an Incomplete Water Analysis" by Frank DeSilva of ResinTech Inc. This article defines what the minimum required water analyses are for:

Cationic Applications (hardness removal, metals removal, radium removal)

Anionic Applications (sulfate removal, nitrate removal, chromate removal, uranium removal, organics removal, perchlorate removal, fluoride removal, dealkalizers, boron removal)

Deionizer Applications

Prior to quoting a residential, industrial, commercial, or municipal water treatment system, the first question we ask at Res-Kem is an inlet water analysis. Often we need to work with incomplete or missing information. The main thrust of the article explains how an educated water treatment person can deduce a missing cation/anion value when there are other known water test values available. As a result, you will be able to properly size the water treatment system.

One great piece of information was the following chart. This chart makes it extremely easy to calculate the cation-anion balance and how to size the system. The conversion factor takes the concentration of an ion in mg/liter to ppm as CaCO3