Improving Organic Micropollutant Removal of Activated Carbon by Pre-treatment with Zeolite Adsorbent

Abstract

Activated carbon (AC) is commonly used in drinking water treatment plants (DWTPs) to remove organic micro-pollutants (OMPs), and it is effective in adsorbing a wide range of OMPs. However, its adsorption efficiency can be affected by natural organic matter (NOM). NOM is a complex matrix and widely exists in water bodies. During the drinking water treatment process, the large size fraction of NOM may block the pore of the granular activated carbon (GAC), and the small size fraction of NOM can compete with OMPs and occupy the sites. The goal of this study is to increase the OMP adsorption efficiency of AC filtration in the drinking water treatment process. The objective was to investigate the feasibility of the competitive NOM removal by zeolite adsorption prior to powdered activated carbon (PAC). Meanwhile, the filtration performance and advantages of nanofiltration (NF) with 1000 Da membranes were found out. Zeolite - AC and NF- Zeolite - AC combined treatments were exterminated. In this study, the properties of zeolites were reviewed and the zeolite with FAU framework was selected as the hydrophobic adsorbent. Batch experiments with FAU and PAC were conducted to examine the adsorption performance of 10 common OMPs in different water samples. Comparative batch tests on UV effluent and NF permeate were carried out with two stages, zeolite pre-treatment and PAC treatment. Ultrapure water and demineralized water were involved as the reference to prove the influence of NOM from adsorption isotherms. Dissolved organic carbon (DOC) measurements were provided by the DWTP. NOM is confirmed to hinder the OMP adsorption on AC according to DOC measurements and adsorption isotherms. NOM smaller than 1000 Da is proved to cause the competition with OMPs. FAU-type zeolite pretreatment was failed to remove the competitive NOM removal.