Transformation characteristics of dissolved organic matter in process of wastewater treatment

Dissolved organic matter (DOM) from influent and effluent of municipal wastewater plant was concentrated using a reverse osmosis (RO) system and the humic acid (HA), fulvic acid (FA) and hydrophilic (HyI) were fractionated by the DAX-8 resin. The study showed that the removal efficiency was almost 90% but each fraction had complicated transformation after biological treatment. HA decreased 9.77% in percentage of total TOC. However, the sum of FA and HyI increased 7.94%.Moreover, the percentage of HyI decreased a little. Comparing with the influent HyI, FA and HA, fluorescence peak of the effluent fraction in III (tryptophan) and IV (tyrosine) disappeared while I (humic-like) and II (fulvic-like) fluorescence peak did not change much. The results of SUVA and acid-base titration indicated the variation of the organic matter structures and aromaticity increased comparing with influent. It can be concluded that the influent organic matter with low molecular weight could be utilized by microorganism and produce new microbial products and high molecular weight organics was relatively difficult for microorganism to use. However, the structure of the high molecular weight organics was changed to a certain extent by microorganism, biological acclimation system could achieve the transformation of organic matter structure so that molecular weight of each fraction in the effluent was affected.