Study On The Metabolism Of Biological Phosphorus Removal In Continuous Flow Anoxic-aerobic Denitrification System

According to the traditional mechanism of biological phosphorus removal,phosphorus release in anaerobic stage is the requirement of the phosphorus excessiveuptake in aerobic conditions in the biological phosphorus process. Moreover, when lowmolecular weight of the organic substance such as volatile fatty acids （VFAs） isscarce in bulk liquid or anaerobic condition does not exist, Phosphate AccumulatingOrganisms (PAOs) are difficult to remove phosphorus. A high phosphorus removal ratewas observed in a lab-scale sequencing batch reactor (SBR), which operated withanoxic/aerobic conditions and fed with starch as the sole carbon source by our researchgroup. Then the metabolism of organic material such as intracellularpolyhydroxyalkanoates (PHAs), glycogen, polyphosphate and extracellular carbonsource (starch) in the SBR was researched. In the past year, the continuous flowanxic-oxic nitrogen removal reactor observed successfully biological phosphorusremoval under the same influent condition with the aforemetioned SBR reactor, but itsmechanism was not analyzed claerly. In this paper, the relevant environmentalconditions of biological phosphorus removal and the mechanism of enhanced biologicalphosphorus removal (EBPR) were studied in continuous flow anoxic–oxic nitrogenremoval system with biological phosphorus removal. The purpose of the study was toprovide for the theoretical basis of developing novel biological phosphorus removaltechnology.Main results are as follows:(1) The phosphorusremoval rate of system was charged with changing influentconcentration of ammonia nitrogen. When the influent concentration of ammonianitrogen increased from10mg/l to15mg/l, the efficiency of phosphorus removalreduced. When influent concentration of nitrate was less than30mg/l, the increasing of (2) nitrate was good for phosphorus removal in the system. When influentconcentration of nitrate was more than30mg/l, denitrification occurred but phosphorusabsorption.(3) When temperature droped from25℃to15℃, phosphorus removal rateincreased, the denitrification ability was relatively stable, but the nitrification abilityobviously got worse in the system.(3) On condition that influent COD was invariable in static experiment, as theproportion of lactic acid enhanced, the highest cumulative quantity of glycogen duringanaerobic stage and highest dissipative quantity of glycogen during aerobic stage wouldincrease, which was benefit for phosphorus removal.(4) The analysis of bacterial community revealed that the the main bacteria werebelong to Proteobaceria, which included γ-proteobacteria. The bacterial community wasaffected by the concentration of nitrate, concentration of ammonia and temperature.Number4bacterium-pseudomonas (GenBank database number: JQ080684.1) wasmain phosphate accumulating bacteria. Number9bacterium-yellow bacillusgenus(GenBank database number: JF523586) and Number27bacterium-Denitratisoma(GenBank database number: HM769664) were main denitrifyingbacterium.The results show that::(1) Energies which produced by changing nitrate to nitrite reduced would lead tophosphorus removal rate reduced in system.(2) When influent COD was400mg/l, limiting concentration of nitrate nitrogenwas30mg/l. when concentration of nitrate is more than30mg/l in influent..Above theconcentration, denitrification is goning on but phosphorus absorption. Below theconcentration, relatively high concentration of nitrate is beneficial to phosphorusremoval.(3) In the continuous flow anoxic–oxic nitrogen removal system, the more lacticacid produced from fermentation of starch, the more produced glycogen. From anoxicto aerobic phase, the more decomposition of glycogen, the more energy offered byphosphorus accumulating bacteria, then enhanced biological phosphorus removal can beobtained well. (4) The studies suggest that there is conducive to biological phosphorus when highnitrate nitrogen concentration, low ammonia concentration and temperature in thissystem.So carbon source and nitrogen concentration in influent need to be controlled,then the sysytem could realize biological removal, the removal rate of phosphorus couldreach approximately70%.