Full Description

While most water treatment facilities are most concerned with the finished water qualityproduced, reverse osmosis (RO) facilities are also concerned with the quality of theirconcentrate. The City of Vero Beach, Florida has successfully operated their RO facilityfor the past 11 years with the originally installed membrane elements. In recent years,membrane performance has decreased and feed pressures have increased significantly.Chemically cleaning the elements provided an effective short-term solution to theperformance problems; however, the membranes returned to their pre-cleaning conditionin less than three months. Based upon the rapid decline in the membrane performanceand age of the membranes, the City elected to replace the membrane elements. Threemanufacturers of 8-1/2 inch thin film composite membranes were tested side by side onthe identical feed water quality. The design of the membrane skid allows for a full-scaledemonstration of seven 8-1/2 inch membrane elements to be loaded into full-lengthpressure vessels. The full-scale test evaluated both the physical operating parameters andwater quality produced from the condition feedwater, permeate, and concentrate stream.This paper focuses on the concentrate water quality produced by the three membranestested. The City of Vero Beach currently disposes of concentrate water from the ROfacility into the Main Canal downstream of a tidal salinity barrier. The quality of theconcentrate water is critical in maintaining this method of disposal for this facility. Thecurrent regulatory permit for the National Pollutant Discharge Elimination System(NPDES) for their concentrate is discussed and compared to the data collectedduring the demonstration pilot test. Membrane performance is evaluated based uponmeeting the NPDES permit criteria. The membranes are compared based upon theresults of acute and chronic toxicity testing that were performed on the concentrate ofeach individual element.The concentrate has been analyzed for a variety of parameters ranging from acute toxicityto ion concentrations. The final membrane selection is based not only on permeatequality but also concentrate quality. Comparisons between membrane performancefocusing on permeate quality and concentrate quality is made. Includes 3 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 13File Size: 1 file , 320 KB