Study On The Characteristics Of Dissolved Organic Matter In Leachate Treatment Process

Dissolved organic matter (DOM) is the major pollutants of landfill leachate,which come from organic decomposition.DOM can be accounted for about 85% of the total organic matter in the leachate, which is the main reason causing, the higher effluent COD.Dissolved organic nitrogen is a relatively important portion of the dissolved organic matter(DOM) in landfill leachate,more attention should be focused on that DON,which may act as a nutrient and a disinfection by-product precursor(NDMA), these substance show more serious threat to human health;thus, how to effectively control DON in wastewater process is becoming a new research hot point. However, DON which is due to the highly complex nature is difficulty to be understanded and which the content of DON is accuratly measured is the key factor to furtherly study its characteristics.The content of DON was determined by selecting pre-treatment method; Characteristic variation of DON in different stages of two combination processes including two-pass RO (process A) and anaeration +aeration +MBR+ NF+ RO (process B) was analyzed ,Characteristics variation of COD and NH3-N was studied in different stages of that, and UV-VIS absorbance, synchronous fluorescence spectroscopy and three-dimensional excitation emission matrix fluorescence spectroscopy (3DEEM) were selected to characterize DOM, FA and HA in different stages of process A and process B in this paper. The main results as follows:(1)Through the comparative test of dialysis bag, NF-90 and NF-270 pretreatment,we found that pretreatment effect followed by NF-270,dialysis bag, NF-90;Although pretreatment effect of NF-270 ,dialysis is approaching, however,not only due to the dialysis bag cost large time and ultra-pure water,but also the dialysis bag is expensive; Therefore pretreatment of NF-270 is selected to test in this paper finally.(2)The removal rate of COD,NH3-N,DON in two combination processes including two-pass RO (process A) and anaeration+aeration +MBR+NF+RO (process B) was analyzed separately, The results indicated that the removal rate of COD ,NH3-N,DON were respectively 98.7%、99.0%、91% for process A, and 87%、99.0%、91% for process B. Process B is superior to process A clearly.(3)These results were confirmed by the values of SUVA254 and E253/E203 decreasing from 0.74 and 0.33 to 0.015 and 0.014 in process A, and from 0.46 and 0.12 to 0.010 and 0.012 in process B. Also, the 3DEEM of DOM indicated that the concentrations of fulvic-like and protein-like compounds decreased and the degree of aromatization was reduced. The further analysis suggested that a good removal efficiency of fulvic-like compounds by two-pass RO system was achieved in process A. Tyrosine-like compounds were mainly removed by microbial degradation, and a good retention effect of fulvic-like compounds and humic-like compounds could be obtained by NF-RO in process B.(4)UV-VIS absorbance, synchronous fluorescence spectroscopy and three dimensional excitation emission matrix fluorescence spectroscopy (3DEEM) were selected to characterize of FA and HA in different stages of process A and aprocess B show that process B is superior to process A clearly.