Study On The Step-Feed A/O Process, Model And Optimization

A/O process with step-feeding has solved effectively the nitrogen and phosphorusremoval within low carbon source. This paper tries to study theoretically this technologyand the usage of carbon in the circumstance of low carbon source, including respirationperformance of activated sludge; the conversion and utilization of carbon in mixed liquor;biological concentration and related kinetic parameters; denitrification process; fitting oforganics and ammonia removal; mathematical model of activated sludge; the wastewaterproportion at feeding entries, etc. The author designed a measuring system with sealedinjection of substrate, which provided an effective research device.This paper studied the respiration performance of activated sludge in Xuzhou WWTPwhich adopted the step-feed A/O process. Since more carbon source existed in mixedliquor a synchronic denitrification takes place in secondary clarifier.Based on the relationship among the components in model ASM1, this paper studiedthe transformation and usage of carbon in mixed liquor. The research shows that the slowlybiodegradable substrate will be hydrolyzed into a readily biodegradable substrate, and thelatter will be attached to the sludge and run into the secondary clarifier in whichdenitrification process will happen.In order to determine the biomass concentration and kinetic parameters, the authordesigned a testing system to measure the oxygen uptake rate, in which the substrate isinjected into a sealed manometric respirometer bottle and thus to guarantee the testingsample is mostly similar to the real wastewater in WWTPs.A fitting is made to simulate the removal of organic and ammonia. Fitting resultshows that the kinetic parameters and autotrophic and heterotrophic biomass obtained inthis research is able to fit the variation of oxygen consumption in the removal process oforganics and ammonia.Based on the above research achievements and ASM1model, a mathematical modelof A/O process and a mathematical model of denitrification in the clarifier were established.And an optimized mathematical model was established for step-feeding proportion. Such adistribution will fully use the carbon source and raise the effectiveness of nitrogen andphosphorus removal. Finally, a modified step-feed A/O was proposed by the author.