Improvement in biodegradability of wastewater quality in urban sewer system

Improvement in biodegradability and hence enhancement of wastewater quality in the urban sewer system was studied via a simulated urban sewer system totaling 1 200 m. TCOD, NO₃^--N and NH₃-N content were changed during the process of sewage transportation. TCOD and NO₃-N content were reduced from (292 to 420)mg·L^-1 to (205 to 315)mg·L^-1 and from (0.26 to 0.6)mg·L^-1 to (0.13 to 0.29)mg·L^-1, respectively. NH₃-N content however increased from (31 to 50)mg·L^-1 to (35 to 66)mg·L^-1. Transformation of organic matter was analyzed by three-dimensional fluorescence spectroscopy, showing a reduction in the content of protein and humic substances. We observed a blue shift occurring for proteins and a red shift occurring for humic substances, indicating a potential change in chemical structure. Molecular weight(MW) analysis showed conversion of high MW(proteins, etc.) and some medium MW organics(humic substances) into low MW organics(acetic acid, etc.). Further studies showed that microorganisms possibly changed the composition of organics, such that unsaturated organics were transformed into saturated substances that could be easily utilized by microorganisms. Consequently, the biodegradability of the wastewater was improved.