Study On Nitrogen Removal From Black Odorous Water With Low Carbon Nitrogen Ratio By Iron-Carbon Microelectrolysis

The phenomenon of black odorous water is a serious aquatic system problem in the process of urbanization,and the "Water Pollution Prevention and Control Action Plan" issued by the State Council also requires that black odorous water bodies in urban built-up areas be eliminated by 2030.However,the causes of black and odorous water are more complex,and there are many influencing factors,and the treatment task is very severe.Ammonia nitrogen concentration is one of the indicators to evaluate black and odorous water,so ammonia nitrogen is mainly used as the main research object.Iron-carbon microelectrolysis(IC-ME)process has gradually entered people’s field of vision in recent years,and it has the characteristics of high efficiency,strong universality,and can improve the biochemistry of wastewater.In order to find out the nitrogen removal effect of black and odorous water with high ammonia nitrogen and low carbon nitrogen ratio,the actual black odor water and water distribution were used as samples,and the indoor simulated nitrogen removal experiment was carried out,starting from the preparation and comparison of iron-carbon materials.The microbial reactor was built to determine the environmental factors(temperature,DO,C/N)required by microorganisms and the influence of iron-carbon dosage on the nitrogen removal effect based on single-factor experiments,so as to provide support for increasing the reactor load;Secondly,the abundance,species and function of microorganisms were discussed through the analysis of 16Sr DNA microbial diversity.The main research contents and achievements are as follows:(1)When the iron-carbon ratio was 1.5:1,the calcination temperature was 600℃ and the calcination time was 2 h,the nitrate concentration was only 3.65 1 mg/L,the removal rate reached 96.02%,the COD co ncentration was 54.23 mg/L,the removal rate was 71.1 7%,and the ammonia nitrogen concentration was 6.231 mg/L;SEM and XPS characterization were carried out on ironcarbon materials,and after SEM characterization,it was observed that the outer surface of ironcarbon materials before and after reaction was clearly different,and the materials before the reaction showed roughness and pores,and the surface voids of the materials disappeared and were relatively smooth after the reaction.After XPS characterization,it was observed that Cls had two peaks corresponding to C=C and C-C,O1s had two peaks corresponding to Fe-O and CC=O,and Fe2p had three peaks corresponding to Fe2+(2p3/2)and Fe3+(2p3/2),where C=C was converted to C-C,indicating that its chemical energy was utilized.Increased Fe2+ and Fe3+ content indicates that FeO is oxidized.(2)According to the single-factor experiment,it was determined that when the reactor temperature was 30℃,C/N=3,DO=3 mg/L and the iron-carbon dosage was 150 g/L,the overall nitrogen removal effect was the best:ammonia nitrogen removal rate was 68.91%～71.64%,COD removal rate was 85.14%～90.13%,nitrate nitrogen removal rate was 81.78%～91.17%,and TN removal rate was 68.41%.In addition,the performance of the process in treating high ammonia nitrogen wastewater was tested,and the maximum load of ammonia nitrogen was increased to 0.1928 kg/(m3·d).The maximum load of COD was increased to 1.7732 kg/(m3·d),and the maximum removal load of nitrogen was 0.2691 kg/(m3·d).(3)Microbial community analysis showed that Proteobacteria at the phylum level were the dominant taxa in all assessed samples;In addition,Gammaproteobacteria and Bacteroidia dominate at the class level;At the genus level,the relative abundance of bacteria unclassified-fEnterobacteriaceae in the denitrification system and Pseudomonas and Nitrobacter and Nitiosomonas in the nitrification system were at a high level.The abundance of Proteobacteria decreased significantly at the phylum level,while the abundance of Bacteroidota and Firmicutes increased significantly.At the class level,the abundance of Gammaproteobacteria decreased,and the abundance of Bacteroidia and Bacilli increased slightly,which indicated that the addition of microelectrolytic materials affected the microbial community structure,thereby further confirming the promotion effect of microelectrolysis on denitrification,thereby confirming its effectiveness,in addition,according to the microbiota function prediction with PICRUST2 software,the proportion of functional genes predicted by nine microbial samples A～I was similar.Among them,the highest proportion is the transport and transport of amino acids,reaching 8.87%～10.32%,and the lowest proportion is nucleotide transport and metabolism,which is 2.74%～3.78%.