Full Description

In 1989, the adoption of a more stringent maximum contaminant level for dibromochloropropane (DBCP) suddenly put many wells operated by California drinking water utilities out of compliance. This case study describes the technical aspects of several utilities' response. Granular activated carbon filters were used to treat the groundwater. GAC pressure filters may be operated in series or parallel; each configuration has advantages and disadvantages. Fifteen of the eighteen treatment units installed in California use the parallel layout. The carbon vessels typically contain 20,000 pounds of carbon and measure 10 to 12 feet in diameter. Most were installed with no advance pilot testing. Most of the units were constructed without competitive bidding. The total cost for a 1,500 gpm well varies from $230,000 to $250,000. Two to three months was needed to fabricate the vessels, and a month required for installation and start up. Headloss is considerably less than anticipated, ranging from 2-5 psi. The need for backwashing is also less than anticipated; some units have run three years without backwashing. While little of the carbon has needed to be replaced, the spent carbon that has been produced was declared nonhazardous. The treatment units are equipped with rupture disks; however, one water company experienced several ruptures that resulted in the loss of water. Bacterial growth in the vessels is a potential problem; some utilities disinfection, others don't. One utility is conducting tests to evaluate the performance of different types of carbon and flow rates.

Product Details

Published: 01/01/1993 ISBN(s): 0898677149 Number of Pages: 5File Size: 1 file , 160 KB