Detecting the Changes of Water Qualities and Fluorescent DOM in a Constructed Rapid Infiltration System

Dissolved organic matter (DOM), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) collected from a water intake and a water outlet in a constructed rapid infiltration (CRI) system were investigated. The results indicated a relatively high microbially derived DOM and an increasing humification degree of DOM in the CRI treatment process. The removal rates of dissolved organic carbon (DOC), COD and TN ranged from 15.2 to 74.6%, 58.9 to 80.4% and 44.8 to 73.8%, respectively. TP concentrations showed a marked increase from inflow to outflow. Fluorescence regional integration (FRI) analysis showed that tyrosine-like materials (PI, n) were easily biodegraded, compared to humic- and fulvic-like substances, whose removal rates ranged from 78.4–90.6%. The tryptophan-like materials (PII, n) showed a marked decrease, in the range of 56.1–79.3%. The humic-like substances (PV, n) had relatively low removal rates in the range of 0.3 to 50.9%. The COD, TN, and DOC were positively correlated with the various Pi, n values and negatively correlated with the humification degree, indicating that the COD, TN and DOC decreased with the degradation of DOM and the increase of DOM humification degree.