AWWA WQTC58970

The objective of this research was to evaluate the effect of two waterquality parameters, chloride and orthophosphate, on the release of iron from an old cast iron pipesection removed from a drinking water distribution system and on the properties of the resultingsuspensions. Experiments were conducted using a section of cast iron pipe (approximately 90 yearsold) removed from the drinking water distribution system of the City of Cincinnati, Ohio. The pipe was approximately 8 cm (3.15 inches) in height and 10.2 cm (4 inches) indiameter. Approximately 1.3 centimeters (0.5 inches) of the original effective inside diameterwas lost to corrosion deposits. One end of the pipe was closed with a rubber seal and hoseclamp fastener.Cincinnati tap water served as the base water for the experiments. The pipe section was "conditioned" with Cincinnati tap water for one year prior to thestart of data collection.All chemicals used in this study were Analytical Reagent(AR) grade. The amount of ultrapure nitric acid, HNO3, used to preserve samples for metals analysis, and sodium chlorideand sodium phosphate (Na3PO4C12H2O) were used to adjust water chemistry. The paper names various instruments for measuring: pH; dissolved oxygen; reduction-oxidation potential; metals content; color, total iron, orthophosphate, and free chlorine; total iron; and, turbidity. Syringe filters (0.45, 0.2:m) were used to separate colloidal iron during color and ironmeasurements. Two liters of Cincinnati tap water were collected in glass beakers after flushing thelaboratory faucet for 5 minutes. If applicable, sodium chloride and sodium phosphate wereadded at this time and the water was mixed. The pH, reduction-oxidation (REDOX) potential,orthophosphate, and free chlorine in the tap water were immediately measured, and watersamples were collected for metals analysis. The remaining volume of test water was then pumpedthrough 6.4 mm (0.25 inch) plastic tubing into the pipe section (standing vertically) at a slowrate of 50 mL/min from the bottom of the pipe. Excess water was allowed to overflow from thepipe section. Dissolved oxygen (DO) was measured with a dissolved oxygen probe suspendedat the center of the pipe during flushing. The pipe section was loosely covered with a glass plateto reduce interaction with the outside environment and allowed to sit undisturbed forapproximately 23.5 hours during weekdays and 72 or 96 hours over weekends. The glass coverwas carefully removed at the end of stagnation. The dissolved oxygen was first measured asbefore. Samples were then carefully drawn for pH, REDOX potential, turbidity, color, total iron,orthophosphate, and free chlorine and measured immediately, and a sample was taken forICAPS analysis.Statistical comparisons between means of treatment groups were made using unpaired testwhen data sets passed normality test or the Mann-Whitney Rank Sum Test when data setsfailed normality test ("=0.05). Normality was tested using theKolmogorov-Smirnov test. All statistical calculations were made using Sigmastat£ (version2.0). Includes 22 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/02/2003

Number of Pages:

15

File Size:

1 file , 1.4 MB