Aeration as a pretreatment alternative to extend the life of granular activated carbon at the Mililani plant : a laboratory study

Abstract

Since actual carbon usage is much greater than predicted at the Granular Activated Carbon (GAC) plant in Mililani, operational costs are higher than estimated. Therefore, diffused aeration and mechanical mixing were examined as possible pretreatment alternatives for removing TCP and DBCP from Mililani groundwater before it enters the GAC plant. Various batch and continuous flow aeration configurations were examined by altering the water heights, air flows, and water flows. The amounts of TCP and DBCP in the Mililani water decreased after aeration pretreatment. Minicolumn experimental results show that the throughput volume before the breakthrough was increased and carbon usage rates were decreased. Therefore, the effective life of the GAC increased. The carbon capacity, i.e. the amount of pesticide adsorbed by the GAC, did not increase after aeration. Therefore, unknown background material not affected by aeration may be utilizing adsorption sites.