professor China Institute of Water Resources and Hydropower Research
The amount of sewage increases rapidly with the development of rural water supply, therefore it is imperative to conduct research on sewage treatment technology suitable for rural areas. Taking rural domestic sewage in Daxing district of Beijing as an object, this paper studied the effect of biological aerated filters (BAF) on the efficiency of rural domestic sewage treatment and microbial community under different filling structures and gas water ratio in an attempt to provide scientific basis for optimal design. Three filling structures and two gas water ratios were designed and a total of four reaction columns were used to study removal effects of pollutants on each reaction column. The #1 column is filled with gravel, which was divided into 3 layers from top to bottom and the particle size is 8-10mm, 10-20mm and 20-30mm respectively. The #2 column is filled with zeolite and gravel, the particle size is 8-10mm, filled after evenly mixed on 1:1 ratio. The #3 column is filled with zeolite and gravel, the particle size is 8-10mm, filled on 1:1 ratio by layered, and the upper layer is zeolite and the lower layer is gravel. The bottom layer of each reaction column is supported by pebbles. As a contrast, the filling structure of #4 column is the same as that of #2 column, the gas water ratio is 3:1, while the gas water ratio of other columns is 5:1.The microorganisms were detected with high-throughput sequencing technology, and microbial population classification, quantity and distribution characteristics were differentiated and analyzed through microbial OUT clustering, community structure analysis and component analysis. The results showed that: ①The removal rate of BOD5, CODcr and ammonia nitrogen in #1, #2and #3 column reached 84.51%-96.49%, the average effluent concentration reached level A in the "Discharge standard of pollutants for municipal wastewater treatment plant"(GB18918-2002), which implied that the designs of these 3 reaction columns are reasonable; #4 column and #2 column have the same filling structure, but the gas water ratio is small, and the treatment effect of BOD5 and CODcr is very poor, which showed that high gas water ratio is beneficial to improving the removal rate of organic matter; however, all the removal rate of TP are low, which is between 29.62%-65.81%, so phosphorus removal measures need to be strengthened. ②The difference of OTU in #1, #2 and #3 columns were very small, which are 1533, 1550 and 1530 respectively, indicating that the number of microbial species was basically the same; the specific OTU number of #2 column is much larger than that of #4 column, indicating that high gas water ratio is favorable to increasing microbial species under the same filling structure; the microbial richness of these four reaction columns was very high, and the variety was not much different. ③There are 6 dominant bacteria groups in #1, # 2 and #3 columns, Protebacteria, Gemmatimonadetes, Chloroflexi, Bacteroidetes, Acfinobacteria, Acidobacteria were sorted by quantity; the dominant species of each reaction column are basically the same at different heights, but the quantity is different; Only Proteobacteria may contain polyP bacteria in these 3 reaction columns, which was also one of the reasons for poor phosphorus removal.
