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