Low Energy Consumption Fixed-bed Bioreactor Based On Zeolite Particle Carrier

At present,the municipal sewage treatment process is dominated by biochemical methods,which account for about 80%,including suspended activated sludge methods（such as A/O,SBR,etc.）and fixed biofilm methods（such as MBBR,Biological contact oxidation method,etc.）.A common feature of these processes is that the oxygen required for microbial degradation of pollutants is achieved by aeration into the water body,but this method is less efficient and consumes extensive energy.Therefore,it is necessary to develop a new type of sewage treatment process with low energy consumption.This paper proposes a new idea for low-energy wastewater treatment,that is,Glycogen accumulating organisms（GAOs）are used to convert organic carbon into intracellular polyhydroxyalkanoates（PHAs）under anaerobic conditions,and zeolite particles are used to convert organic carbon into intracellular polyhydroxyalkanoates（PHAs）.Ammonia nitrogen is adsorbed and removed from the water body to achieve sewage treatment;the biofilm is directly exposed to the air by means of drainage,and the free circulation of air inside the filler provides the biofilm with oxygen required for the degradation of pollutants,avoiding high consumption The energy-efficient aeration process achieves the goal of reducing the energy consumption of sewage treatment,so as to develop a new type of fixed-bed biofilm sewage treatment technology based on zeolite particle carriers.The main research contents are as follows:（1）Research on wastewater treatment of zeolite particle packing fixed-bed biofilm single reactor.A fixed-bed reactor using zeolite particles as a biofilm carrier was designed and constructed,and an aerobic pool activated sludge was used as inoculation sludge.The results show that after nearly two weeks of short-term domestication,the COD removal rate can be increased to more than88%.Under the influent（anaerobic）-drainage（aerobic）cycle,the removal effect of ammonia nitrogen and total nitrogen can reach 80%.During the domestication process,the periodic changes of PHAs and glycogen content in the microbial membrane at the anaerobic stage and aerobic stage proved the effective enrichment of GAOs,and the enhancement of the denitrification process was observed at the same time.Using 16S r RNA to analyze the biofilm flora shows that the enriched biofilms are mainly three bacterial genera,Thaurea,Candidatus Competibacter（GAOs）,and Nitrospira,which are the key microorganisms for COD and nitrogen removal.（2）Research on wastewater treatment in a fixed-bed biofilm dual reactor with zeolite particle packing.A double（series）system based on a fixed biofilm reactor with zeolite particle packing was designed and constructed.The results show that the system further improves the removal rate of ammonia nitrogen and total nitrogen.The operating results showed that the removal rates of COD,NH₄⁺-N,and total nitrogen were 92%,97%,and 96%,respectively,and the effluent could reach GB1891-2002 standard level A（ammonia nitrogen and total nitrogen requirements）.With the shortening of the hydraulic retention time（12h→6h）,the removal rate of COD and ammonia nitrogen decreased slightly to 8%and 0.8%,respectively,and the total nitrogen removal rate increased by 5%.The processing load of the system is further increased by approximately 2 times.The study further found that the composition of the biofilm in the A column and the B column of the dual reactor changed significantly with the change of the variable hydraulic residence time.With the shortening of the hydraulic retention time and the increase of COD load,the abundance of GAOs in column A increased by 3.17 times（8.01%→25.39%）.The high-load carbon source is more conducive to the enrichment of Candidatus Competibacter,among which Defluviicoccus（DGAOs）are transformed into Candidatus Competibacter.The total abundance of bacteria with denitrification ability is 6.91%,which is 4.5 times that of the original sludge.In the B column,due to the increase of the influent COD,GAOs were significantly enriched（0.05%to 5.52%）,and the NOB abundance（1.75%）was slightly higher than that of the A column（1.41%）.（3）Research on sewage treatment of mixed-packed fixed-bed biofilm single reactor.Due to the low porosity of the pure zeolite particle packing reactor,the effective volume of the unit reactor is low.In order to further increase the effective volume of the unit reactor,the traditional plastic suspension packing（HDPE）and zeolite packing are configured in a volume ratio of 1:1 to prepare a mixed packing reactor.Using the activated sludge from the aerobic tank as the inoculation sludge,the system’s long-term operation experiment results showed a stable sewage treatment efficiency:the removal rate of COD reached 89%,and the removal rate of ammonia nitrogen and total nitrogen reached about 57%.Biofilm community analysis showed that the abundance of GAOs in the system was increased by about 10 times（0.46%→4.60%）compared with the initial activated sludge.At the same time,the bacterial species on different fillers are different.The relative abundance of GAOs on HDPE plastic fillers is better than that of zeolite particles,which is twice as high.Candidatus Competibacter accounts for the majority,and the relative abundance of Pseudomonas on the surface of zeolite particles is Better than HDPE filler.Due to the use of mixed packing,the effective volume of the system is greatly increased,which greatly increases the sewage treatment load of the system.