Study On The Combined Recovery Of Nitrogen And Phosphorus From Residual Sludge By Ultrasonic Alkaline Hydrolysis Bipolar Membrane Electrodialysis

In denitrification and dephosphorization process of sewage treatment plant produce a large number of rich phosphorus sludge disposal difficulty effectively,easy to cause secondary pollution,and biological denitrification process the problem of carbon source,this topic proposed to the rest of the effective separation of nitrogen and phosphorus in sewage sludge and organic matter,respectively as denitrification carbon source for nitrogen and phosphorus recovery and utilization of the recycling.For this reason,the combined ultrasonic and alkaline hydrolysis processes were first used to dissolve sludge cells,and then the separation and concentration of nitrogen and phosphorus was studied by bipolar membrane electrodialysis system.The main research results are as follows:（1）Sodium hydroxide was added to adjust the p H value,and the reaction was conducted under 23℃for 4h.The higher p H value was conducive to the release of total nitrogen and total phosphorus.The ratio of ammonia nitrogen to total nitrogen and the ratio of orthophosphate to total phosphorus in the sludge supernatant was negatively correlated with the p H value.（2）When the sound energy density increases in the range of 0.0625～0.25W/m L,the release amount of nitrogen,phosphorus and organic matter in sludge will increase,but the energy consumption required to release unit nitrogen and phosphorus from sludge will also increase.Under the condition that the sound energy density is increased to 4 times,the energy consumption required to release unit ammonia nitrogen increases to 1.76 times,and the energy consumption required to release unit orthophosphate increases to 1.67times.（3）The release amounts of ammonia nitrogen,orthophosphate,total nitrogen and total phosphorus were 212.93%,151.62%,252.83%and 166.63%of the control p H（unadjusted p H,p H=6.7±0.1）at 0.0625w/m L with alkaline p H=10.The corresponding energy consumption per unit of ammonia nitrogen release was 30.17%of that of the control,and the energy consumption per unit of orthophosphate release was 33.52%of that of the control.（4）The factors affecting the release of ammonia nitrogen and orthophosphate were ranked as follows:Sound energy density>p H>ultrasonic time.The second base was added at the initial time and the reaction time of 20min.By the end of the 60min reaction,the release of ammonia nitrogen and orthophosphate increased by 8.62%and 13.68%respectively compared with that of the first base addition.（5）In the bipolar membrane electrodialysis separation system,the current density within the range of 0.5～2 m A cm^-2,the current density of the recovery of orthophosphate remained unchanged,while the recovery of ammonia nitrogen increased.After the reaction with current density of 1 m A cm^-2 for 150min,the recovery rate of ammonia nitrogen was 85.31%and that of orthophosphate was 97%.