AWWA QTC98311

This paper discusses the results of two flushing studies conducted by Cleveland Water Division (CWD). The first is a dead-end flushing program conducted independently by CWD, while the second is an AWWARF Field Study in which CWD participated. The objectives of the dead-end flushing program were to: draw dissolved phosphate into the dead-ends or low flow areas of the distribution system; prevent the build up of phosphate in these areas; and, monitor chlorine residuals. Flushing time at each site varied depending on the area's ability to supply the target velocity of 2.5 ft/sec while maintaining pressure. Another factor influencing the time spent at each site was the ability to dispose of the flushed water into the sewer system without causing property damage. During each flushing event, the following data was recorded: date, street, municipality, flush time, flush volume, main size, starting PO4 level; ending PO4 level; ending C12 level. Heterotrophic plate count (HPC) levels were checked in areas of concern, but not all sites were tested. The phosphate and chlorine levels were determined using HACH colorimeter field test kits. The objective of the AWWARF field study was to evaluate the impact of focused flushing events on water quality in selected dead-end areas, specifically with respect to phosphate levels, coliform, and chlorine residuals. Water quality monitoring was conducted before, during, and after focused flushing events scheduled at two mid-point locations and five selected dead-end areas in the distribution system. Sampling occurred during four separate flushing events. The parameters selected for sampling before, during, and after flushing include: pH, total and fecal coliform, chlorine residual, turbidity, phosphate (particulate and dissolved), temperature, coliform, HPC, and visual observations. Particulate and dissolved phosphate were measured by filtering the sample through a 0.45 um membrane filter. HPC bacteria were analyzed using R2A agar by an independent contracted laboratory. Total and Fecal coliform were analyzed using the MMO-MUG method (Colilert[R]) since the Colilert method is used during routine regulatory monitoring. Temperature was field measured with a laboratory thermometer checked against the Lab NBS unit, and chlorine residual was measured by a HACH DPD colorimeter. Visual observations were made by laboratory personnel and experienced distribution system personnel.

Product Details

Published:

01/01/1998

ISBN(s):

0898679796

Number of Pages:

9

File Size:

1 file , 62 KB