Insight into oxidation and adsorption treatment of algae-laden water: Algal organic matter transformation and removal

Abstract

The efficacy of applying gas phase surface discharge non-thermal plasma (NTP) combined with anion-exchange processes for algae-laden water treatment was evaluated. The excitation-emission matrix fluorescence and parallel factor analyses coupled with two-dimensional correlation spectroscopy (2DCOS), hetero-2DCOS, and perturbation correlation moving window two-dimensional correlation spectroscopy of ATR-FTIR and synchronous fluorescence spectra were used to elucidate variation in the functional groups and algal organic matter (AOM) conformations during the NTP oxidation process. The intracellular compounds released from the lysis of algal cells could be effectively degraded and mineralized, which was accompanied by a rapid decrease in chlorophyll a, turbidity, and particle size. The organic nitrogen could be instantly converted to NH4+-N during NTP oxidation and then oxidized to NO3−-N with negligible NO2−-N accumulation, resulting in a continuous increase in NO3−-N. The final concentration of the toxin microcystin-LR was far lower than the standard for drinking water (1.0 μg/L). The chromophoric functional groups were destroyed over time, and the aromatic carbon was gradually converted to aliphatic carbon via NTP oxidation. The transition times of functional groups and fluorescent fractions were all in the range of 10–20 min. In the post-NTP treatment, the L20 resin could remove 38.4% of DOC, 83.4% of NO3−-N, 73.2% of TN, and 63.8% of TP in the treatment loading of 600 resin volume and exhibited high reusability during 10 adsorption–desorption cycles. Overall, NTP oxidation combined with resin adsorption might be a potential candidate to address algae-laden water and minimize its adverse effects thereafter.