ADDITION OF UV DISINFECTION FOR KAILUA REGIONAL WASTEWATER TREATMENT PLANT, HAWAII

摘要

The Kailua regional wastewater treatment plant near Honolulu, Hawaii, treats flows of56,818 m3/d (15 mgd) and discharges to Kailua Bay. Concern over the discharge of undisinfectedeffluent to a bay where humans have direct contact with the water led to design of a disinfectionfacility.The city and county of Honolulu, Hawaii, chose ultraviolet disinfection, a less commonly usedtechnology for wastewater treatment. Because few operating UV systems for wastewaterdisinfection exist in Hawaii, a pilot study was conducted to characterize treated wastewater fromthe Kailua plant and determine if UV disinfection would be effective.The pilot study indicated that UV disinfection would meet the effluent criteria for Enterococci.Several types and configurations of UV systems were evaluated. Based on technical and costevaluations, the engineers designed a low-pressure system with a vertical lamp configuration.Performance of the UV system indicates that it is effective on a secondary effluent with as muchas 20 mg/L suspended solids. However, experience has also shown that oil and grease caninterfere with the disinfection process. At Kailua Regional WWTP, therefore, operators havelearned that continued vigilance and daily equipment inspections are essential to maintainingperformance of the UV disinfection system.