Pilot Study On The Treatment Of Sludge Biogas Slurry By Two-stage Anaerobic Ammonia Oxidation Process

With the continuous expansion of the scale of municipal sewage treatment in China,a large amount of municipal sludge comes along,which needs to be properly treated to avoid causing harm to the environment.Among various kinds of technology,thermal hydrolysis?THP?of sludge anaerobic digestion?AD?technology has to speed up the hydrolysis of organic matter,improve the reaction rate,reduce the sludge viscosity etc,but along with the process also produced a large number of containing high concentration of ammonia nitrogen and low carbon nitrogen ratio of anaerobic digestive juices,must be treated before emissions to the environment,the efficient of high concentration of ammonia nitrogen removal is one of the bottleneck problem of biogas slurry treatment sludge.Anaerobic ammonia oxidation process compared to traditional biological technology has save aeration,without additional carbon source,the advantages of small volume of reactor,is now in its application in the traditional sludge biogas slurry denitrification,but by anaerobic ammonia oxidation process for high concentration of ammonia nitrogen and low carbon nitrogen ratio of biogas slurry thermal hydrolysis anaerobic digestion sludge denitrification of related research is less.This paper through two stages nitrosation-anaerobic ammonia oxidation process thermal hydrolysis anaerobic digestion sludge of biogas slurry?THPAD-RW?test and pilot experiment,the working condition of the system,process parameters and microbial community structure research,explore the application feasibility of the technology efficient nitrogen for anaerobic ammonia oxidation process THPAD-RW of high nitrogen treatment to provide theoretical and technical support.Main contents and conclusions are:1.Pilot nitrosationIn this experiment,the effective pool capacity of nitrification was 64 m3,and the substrate concentration of THPAD-RW was gradually increased,with NH₄⁺at1212.02-2178.11 mg/L and COD at 1282-3504 mg/L,which was typical wastewater with high ammonia nitrogen and low carbon nitrogen ratio.The nitrosation operation is divided into two stages:1-150d for stable operation and 150-302d for optimized operation.The stable operation stage is only to provide a suitable ratio of ammonia nitrogen and nitrite nitrogen in the water for anaerobic ammonia oxidation,and the denitrification and removal of organic matter in the nitrification process is not fully utilized.Therefore,nitrification is optimized.The highest nitrogen load?NLR?in nitrite stable operation was 0.322 kgN/m3·d,the average removal rate of total nitrogen was20.17%,and the average removal rate of COD was 34.90%.In the optimal operation phase of nitrosation,the highest nitrogen load?NLR?was 0.482 kgN/m3·d,and the average removal rate of total nitrogen was 42.97%,while the average removal rate of COD was 50.29%.The total nitrogen removal rate in the optimized operation stage was113.04%higher than that in the stable operation stage,and the COD removal rate was44.10%higher than that in the stable operation stage.This study analyzed the causes of nitrite and found that the temperature was33±1?,the dissolved oxygen?DO?was 0.5-1.5mg/L,and the free ammonia?FN?was5.46-7.88mg/L,all within the range conducive to the accumulation of nitrite,which constituted the factors of nitrite accumulation.pH 6.0-7.8 is not conducive to the accumulation of nitrite nitrogen within the scope,not constitute the nitrite nitrogen accumulation factor.High throughput sequencing was used to analyze the characteristics of microbial community structure in nitrification reactor.Alpha diversity analysis showed that nitrification sludge samples contained a particularly large number of species and high diversity.This is because the concentration of organic matter in THPAD-RW is relatively high,a lot of bacteria grow in the tank.Analysis of community structure components showed that,at the phylum level,the proportion of Proteobacteria in nitrosation sludge samples was 46.24%,and most nobs and all aobs were known to belong to Proteobacteria,from which it could be inferred that nitrosation bacteria had been enriched in the reactor.At the genus level,only Nitrosomonas belongs to ammonia oxidizing bacteria?AOB?,with an abundance of 7.07%in the reactor.Although AOB only accounts for a small part of the total number of bacteria,it has the ability to efficiently oxidize ammonia nitrogen into nitrous nitrogen.At the same time,no nitrite oxidizing bacteria?NOB?was detected in the reactor,indicating that NOB was well inhibited and eliminated from the system.2.Pilot anaerobic ammonia oxidationIn this experiment,the effective tank capacity of anaerobic ammonia oxidation was34 m3,and the SBR operation mode was adopted.The outlet water from the nitrosation section was used as the inlet water of the anaerobic ammonia oxidation section.The inlet NH₄⁺concentration was about 585.96mg/L,and the inlet water NO₂^-concentration was about 628.57mg/L.The anammox operation is divided into two parts,the stable operation part and the unstable recovery part of the system due to abnormal conditions.In the stable operation part,the highest nitrogen load?NLR?was0.447 kgN/m3·d,and the total nitrogen removal rate was more than 80%.COD has been removed in the pool,and the removal rate is about 18.40%.Due to the high concentration of organic matter in the water,a large number of heterotrophic bacteria have grown in the pool.Moreover,with the longer and longer running time,the removal rate of COD has become higher and more heterotrophic bacteria have increased.In the instable recovery part,due to the suppression of high pH9.6 for 12d,the inlet nitrogen load?NLR?was as low as 0.042 kgN/m3·d,and resumed operation after 16d.The high concentration of NO₂^-in the tank inhibited the activity of anaerobic ammonia-oxidizing bacteria due to repeated water outage,and the nitrogen load?NLR?was as low as 0.103 kgN/m3·d.Because the drainage siphon was not damaged,the NO₂^-concentration in the tank was too high to inhibit the activity of anammox,and the nitrogen load?NLR?was as low as 0.090 kgN/m3·d.When the anaerobic ammonia-oxidation process runs at the highest load,the environmental conditions change,and the anaerobic ammonia-oxidizing bacteria are easily affected,resulting in the decrease of activity.Therefore,if stable operation is desired,the anaerobic ammonia-oxidation process should be kept below the maximum load,and the load should be steadily increased as the activity of the bacteria increases.The analysis of each instable recovery stage shows that the whole anammox system is stable and can be recovered in a certain period of time,although the activity of the system will be affected in extreme cases.High throughput sequencing technology was used to analyze the changes of microbial community structure during operation,and the anaerobic ammonia-oxidized activated sludge at 29d?A1?,145d?A2?and 292d?A3?were selected for Illumina high-throughput sequencing.Alpha diversity index analysis and OUTs Venn analysis showed that during the operation of anaerobic ammonia oxidation,the richness and diversity of sludge flora increased gradually.Three samples of anaerobic ammonia oxidation sludge community structure component analysis showed that on the level of the door,floating mold gate?Planctomycetes?with relative abundance of reactor run first increase then decrease,that anaerobic ammonia oxidation bacteria concentration in the beginning and middle and late as the number of heterotrophic bacteria is becoming more and more serious loss of anaerobic ammonia oxidation bacteria accounted.At the genus level,the presence of Candidatus Brocadia and Candidatus Kuenenia anammox bacteria in the three samples decreased with the operation of the reactor and was consistent with the analysis at the gate level.3.Comparative analysis of the activity and community structure of anammox granule in different particle size rangeIn the whole operation process of all reactors,the activity of the pellet bacteria was the best at the beginning,and the activity was increased to the highest for 3 days,and the highest was NLR 0.213 kgN/m3·d.Then the activity was stable and the operation was stable.At the beginning,the activity of the pellet was slightly worse than that of the pellet with the particle size above 0.425mm.It took 9 days to increase the activity to the highest level,and the highest level was NLR 0.320 kgN/m3·d.Then the activity was stable and the operation was stable.In the range of particle size below 0.25mm,the activity of the pellet was the worst at the beginning,and it took 24 days to increase the activity to the highest,the highest was NLR 0.213 kgN/m3·d,then the activity was stable and the operation was stable.The nitrogen load and nitrogen removal load were the highest and the nitrogen removal performance was the best.The microbial community structure above 0.425mm?A1?,0.25-0.425mm?B1?and below 0.25mm?C1?was analyzed by high throughput sequencing technology.Alpha diversity analysis index indicated that the smaller the particle size,the smaller the microbial population richness and diversity.Venn analysis of OTUs shows that large and medium particle sizes have higher similarity and smaller difference than small particle sizes.Community structural component analysis showed that the relative richness of Planctomycetes was 15.2%,17.19%and 37.47%,respectively,in A1,B1and C1 at the phylum level.However,this contradicted the results of the analysis at the genus level,which indicated the presence of anammox Candidatus Brocadia and Candidatus Kuenenia in the three samples,and the proportion of both decreased with the decrease of particle size range.The proportion of bacteria of Planctomycetales?unclassified in different particle size ranges A1?8.01%?<B1?11.95%?<C1?33.61%?,the increase in size range with the decrease in size is consistent with the analysis at the gate level,indicating that bacteria of the Planctomycetales?unclassified genus are likely to contain anammox.