Study On Denitrification Performance Of Fermentation Liquid Of Food Waste In A/O-MBR As External Carbon Sources

This paper is about processing domestic wastewater in campus through adding the anaerobic fermentated product of food waste(fermentation liquid of food waste) as a new external carbon source into A/O-MBR to enhance nitrogen removal. The study mainly includes the following two parts: firstly, exploring the characteristics of the fermentation liquid of food waste(FLFW) as the carbon source through adding it into lab-scale A/O-MBR, and analyzing the practical application of the FLFW as the carbon source through adding it into pilot-scale A/O-MBR. The main conclusions were as follows:1 Comparing the results of addting three different carbon sources, glucose, sodium acetate and FLFW into lab-scale A/O-MBR, we find that:(1) when FLFW is external carbon source, removal rate to COD and NH4+-N of wastewater is more than 96% and the TN removal efficiencies is up to 78.5%, which means FLFW as the carbon source can remove the pollutants in the sewage efficiently.(2) the specific denitrification rate(11.28 mg NOX-N/g VSS·h) and COD utilization rate for denitrification(18.75%) of the FLFW are the best, which demonstrated that FLFW could be utilized more easily by organisms with higher denitrification rate and potential.(3) The EPS content in anoxic,oxic and membrane tank are the highest of the three carbon sources, which meant that FLFW as carbon sources might cause membrane fouling more easily.(4) the comparison of the sodium acetate with the FLFW shows that the Specific Oxygen Uptake Rate(SOUR) of the two carbon sources are almost the same. That means when the FLFW is used as the carbon source, the activity and nitrification capacity of aerobicmicrobes in the system are better.(5) The particle size of activated sludge are the smallest with FLFW as carbon source.2 Comparing the conditions before and after adding the FLFW into pilot-scale A/O-MBR, we find that:(1) with the increase of FLFW addition, the NO3--N in effluent decrease gradually to 7.92mg/L, and the TN removal efficiencies increase to 66%,which shows that the FLFW enhance nitrogen removal in A/O-MBR significantly.(2)the EEM spectral of SEPS and BEPS shows that the FI of protein is gradually reduced along with the process, and the concentration of EPS、SEPS and BEPS are also reduced along with the process, which is good for A/O-MBR device added with FLFW to control the membrane fouling. The images of membrane under Aton Force Microscope(AFM) display that the surface of virgin membrane is smooth, but it become rough when the membrane is fouled, but after chemical clean, it become smooth again. In addition, the value of TMP, R and k show the same tendencies which meant that membrane is easily fouled with FLFW as carbon sources, but it could be recovered by chemical clean.(3) as the processing time goes by, SOURN and SOURA firstly rise up and then get stable, and SOURH firstly lowers and then gets stable, which meant that adding FLFW into A/O-MBR as carbon source, the activity of sludge could be enhanced in a short period, and no negative effect occurre.(4) with the increase of FLFW addition,the particle size of sludge become smaller and the percentage of smaller particle become higher.