POTENTIAL FOR DECENTRALIZED RESIDENTIAL TREATMENT AND REUSE OF WASTEWATER IN HAWAII

Over 180,000 residences in the State of Hawaii are not provided service connections to the County-operated wastewater collection, treatment, and disposal systems. These residents must operate their own on-site, individualtreatment and disposal systems. Most of the existing systems are cesspools or septic tanks with leach fields that provide only partial treatment that can adversely impact groundwater and surface waters. In some cases, these same residences do not have connections to the County potable water supply. A study was conducted in which an onsite residential wastewater package unit was tested according to an established protocol to determine if it could produce a high-quality effluent. Additional pilot-scale sand filtration and ultraviolet (UV) disinfection units were operated for a period of time to determine the feasibility of producing reclaimed water suitable for residential reuse and which could meet local regulations. The results indicate that the package unit can produce an effluent equivalent to secondary effluent. In addition, it is possible but not highly feasible to produce the highest quality of reclaimed water recognized by Hawaii regulations. It is possible and perhaps economically feasible under certain circumstances to produce a slightly lower quality reclaimed water suitable for residential subsurface irrigation.