Full Description

Waters produced from five different treatment systems (aeration (G1), NF (G4), CSF-O3-GAC (S1), IMS (CSF-NF or S2) and high pressure RO are blended and distributed to 18different pilot distribution systems (PDS) to determine the effect of blending on distributionwater quality. PVC, lined iron, cast iron and galvanized steel pipes taken from actual distributionsystems were used in the construction of the PDSs. A HRT of five days was utilized for thestudy. Models for free chlorine and chloramines dissipation were developed using non-linearregression from the PDS data. The model parameters are pipe material, chlorine dose (mg/L Cl),temperature (oC), time (hr), and UV254 (cm-1). The models follow first-order kinetics with respect to chlorine dose. The model for freechlorine includes an overall rate constant whereas the chloramines model was further developedto separate the effect of bulk reactions from the wall reactions. The results for the models showthat chlorine decay is highly affected by the pipe material. The rate of chlorine dissipation forPVC and lined iron is less than that for cast iron and galvanized steel. In general PVC pipes havethe capacity to keep chlorine residual longer than the other materials. The iron-based pipes showa rapid decline in the chlorine concentration due to the reaction of chlorine with the corrosionproducts of iron.The models show that the rate of chlorine dissipation increases with an increase of eithertemperature or organic content. TOC reduction increases PDS residual. Fifty percent TOCremoval corresponded to doubling the residual presence. Residuals are difficult to maintain inwaters above 25 degrees C. Pipe material was the most significant factor affecting residual presence.The free chlorine and chloramines models were verified using independent data. Includes 11 references, tables, figures.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 13File Size: 1 file , 2.4 MB