Reverse osmosis followed by activated carbon filtration for efficient removal of organic micropollutants from river bank filtrate

Abstract

Drinking water utilities in Europe are faced with a growing presence of organic micropollutants in their water sources. The aim of this research was to assess the robustness of a drinking water treatment plant equipped with reverse osmosis and subsequent activated carbon filtration for the removal of these pollutants. The total removal efficiency of 47 organic micropollutants was investigated. Results indicated that removal of most organic micropollutants was high for all membranes tested. Some selected micropollutants were less efficiently removed (e.g. the small and polar NDMA and glyphosate, and the more hydrophobic ethylbenzene and napthalene). Very high removal efficiencies for almost all organic micropollutants by the subsequent activated carbon, fed with the permeate stream of the RO element were observed except for the very small and polar NDMA and 1,4-dioxane. RO and subsequent activated carbon filtration are complementary and their combined application results in the removal of a large part of these emerging organic micropollutants. Based on these experiments it can be concluded that the robustness of a proposed treatment scheme for the drinking water treatment plant Engelse Werk is sufficiently guaranteed.

Online monitoring of N-nitrosodimethylamine for the removal assurance of 1,4-dioxane and other trace organic compounds by reverse osmosis

“…1a) despite their identical molecular weight (88.1 Da) ( Table 1). Our results are consistent with a previous study by Schoonenberg Kegel et al 35 who also reported higher rejection of 1,4-dioxane (96%) than that of NDMA (74%) by an RO membrane. (Fig.…”

Persistent, mobile and toxic (PMT) and very persistent and very mobile (vPvM) substances pose an equivalent level of concern to persistent, bioaccumulative and toxic (PBT) and very persistent and very bioaccumulative (vPvB) substances under REACH

“…Even expensive techniques, such as air stripping or adsorption by activated carbon, are unsuitable. Removal by membrane filtration is also ineffective; even reverse osmosis fails to reach higher than 70% rejection due to its small size and neutrality [65]. These physical removal processes, even if they are effective, simply transfer 1,4-dioxane from one phase to another, wherein it is more concentrated and requires subsequent treatment Do emissions need to be minimized?…”

Quantification and modelling of organic micropollutant removal by reverse osmosis (RO) drinking water treatment

“…Benzene (11) thereby adsorbs and permeates through the membrane, while for example, 1,4 dioxane does not [64]. According to some literature, benzene is classified as a hydrophobic solute [65]. However, in the database that was used in this study for measuring the hydrophobicity of compounds, benzene's log D was 1.97 which is very close to 2.…”

“…However, in the database that was used in this study for measuring the hydrophobicity of compounds, benzene's log D was 1.97 which is very close to 2. Schoonenberg Kegel et al [65] speculated that the high passage of benzene was probably due to the partitioning of this solute into the membranes as a result of hydrophobic-hydrophobic interactions between benzene and membrane, resulting in an increased transport through the membranes. NDMA (74 Da) showed 94.72% passage suggesting a very poor removal efficiency.…”

“…Therefore, the poor removal of NDMA is more related to its size rather than its hydrophobicity. Moreover, the very compact structure and hydrogen bonding of NDMA might be other reasons of very poor removal efficiency [59,65].…”