Integration of coagulation and adsorption for removal of N-nitrosodimethylamine (NDMA) precursors from biologically treated municipal wastewater

Abstract

This study investigated the N-nitrosodimethylamine (NDMA) formation potential of various dissolved organic matter (DOM) fractions in biologically treated municipal wastewater by UF fractionation, XAD-8 resin adsorption isolation, and excitation and emission matrix (EEM) fluorescence spectroscopy. Removal of various NDMA precursor fractions was also analyzed to evaluate the efficiency of traditional water treatment processes (coagulation, adsorption, and coagulation-adsorption). Results showed that NDMA were mainly formed by low molecular weight (MW) fractions (<30 kDa) and hydrophilic fractions (HiS) in biologically treated municipal wastewater. Integrated coagulation-adsorption treatments showed the highest reduction capacity for NDMA formation potential (57%), followed by isolated adsorption treatment (50%) and isolated coagulation treatment (28%). The powdered activated carbon (PAC) adsorption process could reduce the high MW precursors (>30 kDa) by 48%, which was higher than other treatments. In contrast, the highest uptake (66%) of low MW precursors (<30 kDa) was achieved by the coagulation-adsorption process. All treatments preferentially removed the hydrophobic acids (HoA) fraction compared to other fractions. Coagulation could remove more fulvic acid-like substances and adsorption could remove more microbial by-products and aromatic proteins.

Identification, Formation, and Predicted Toxicity of Halogenated DBPs Derived from Tannic Acid and Its Biodegradation Products

“…Excitation–Emission matrix analysis was conducted to characterize the changes of dissolved organic matter (DOM) from biodegradation of tannic acid in water and, thus, to better understand the variation of tannic-derived DBP precursors during biodegradation. On the basis of previous studies, fluorescence peaks of respective substances with corresponding Ex and Em ranges are as follows: Region I (Ex 230–300 /Em 250–390 , soluble microbial byproduct-like materials); Region II (Ex 230–300 /Em 390–550 , fulvic acid-like materials); Region III (Ex 300–480 /Em 300–550 , humic acid-like organics). The characteristic peak of tannic acid was centered at Ex/Em = 300/385 nm (Figure S19).…”

Removal Characteristics of N-Nitrosamines and Their Precursors by Pilot-Scale Integrated Membrane Systems for Water Reuse

“…The relatively high reduction rates by the MF and SF processes could be attributed to the effect of coagulant added upstream. Wang et al reported that coagulation preferentially removed NDMA precursors with molecular weight >30 kDa and hydrophobic fraction of a biologically treated wastewater [ 45 ]. Charge neutralization of negatively charged colloids by coagulant might be attributed to adsorption of the NDMA precursors onto some colloids or particulate compounds, which could be the reason for the reduction of NDMA FP due to the addition of coagulant.…”