| The aerobic granular sludge technology has made great progress in recent years.AGS can remove carbon,nitrogen and phosphorus at the same time,and has multiple advantages in saving investment cost and floor area.In order to realize the comprehensive operation of this technology in the sewage treatment plant and ensure the sludge stability and pollutant removal performance,it is the focus and hot spot of laboratory research at present.The sludge inoculated in this experiment was mature aerobic granular sludge,which was cultured in SBR reactors R1 and R2 for a long time.In this study,low concentration organic synthetic wastewater was used as the substrate to cultivate a kind of rich-mineral sludge.The physical and chemical properties,pollutant removal pathway and microbial community of granular sludge were systematically studied,and the key factors and control parameters affecting the stable operation and removal performance were also studied.The details are as follows:（1）Analysis of sludge aging and disintegration and culture of rich-mineral AGS.After 42 days,the mature sludge in R1 reactor did not change its original particle size for cultivation.The main characteristics of sludge aging were as follows:the particle size increased（>3 mm）,the EPS content decreased,the black anaerobic area appeared in the sludge,and finally the granular sludge was broken and disintegrated,and the pollutant removal efficiency decreased significantly.Through analysis,it is concluded that the main reason for aging is too large particle size and long sludge age.Finally,the sludge aging can be quickly controlled by reducing the influent organic matter concentration（500-400 mg/L）and shortening the sludge age for 30 days.By cultivating a kind of rich ore sludge,the average removal rates of carbon,nitrogen and phosphorus are 93%,70.24%and 71.5%respectively in the stable operation stage.（2）Culture and stability analysis of rich-mineral AGS.By reducing the influent organic matter concentration（500-400 mg/L）and COD/P（50:1-40:1）,SRT was set for 40 days,and the mature sludge in R2 reactor was cultured after artificial crushing to change the particle size.After 139 days,the rich-mineral AGS with calcium phosphate precipitation as the core appeared and kept stable operation.The particle size of the rich-mineral AGS increased significantly,which was 3-6 mm.XRD analysis confirmed that the mineral precipitation was mainly hydroxyapatite.Due to the accumulation of sediment,the combination of minerals and EPS improves the three-dimensional structure of sludge,and the physicochemical properties changed significantly:the mass ratio of Ca/P in sludge increased（from 1.12 to 2.12）,the settling rate increased（146 m/h for rich-mineral sludge and 76 m/h for non-mineral sludge）,and the ratio of MLVSS/MLSS decreased（0.56 for rich-mineral sludge sludge and 0.71 for non-mineral sludge）,The value of SOUR decreased（35 mgO2/（gMLVSS·h）for SOUR mineral-rich and 57 mgO2/（gMLVSS·h）for SOUR non-mineral）,and the total content of EPS increased（77.28 mg/gMLSS for EPS mineral-rich and 53.91 mg/gMLSS for EPS non-mineral）.（3）The recovery experiment and stability analysis of activity in rich-mineral AGS.The activity recovery was carried out by adjusting the organic load of water（0.81-0.61-1.35 kgCOD/m3d）,and the cycle time（6-8-6 h）.EPS content gradually increased during the culture process,which improved the three-dimensional structure stability of sludge,and rich-mineral AGS could quickly recover and stable operation in a short period,and the average removal rate of carbon,nitrogen and phosphorus was 96%,80.1%and 89.24%respectively.（4）Study on the way of denitrification and phosphorus removal in the sludge system of rich-mineral AGS.The average removal rates of nitrogen and phosphorus were increased by 29.17%and 34.68%respectively.In the stable stage,the removal rates of carbon,nitrogen and phosphorus were 94%,81.62%and 91%,respectively.COD was mainly removed by GAO,TN was mainly removed by SND pathway,and the SND efficiency was 72.78%.Part of TP was removed by chemical phosphorus removal（66%）,and the rest was removed by biological phosphorus removal（34%）.（5）Batch experiment of the activity of poly-phosphate bacteria in different size sludge.The results of the batch experiment showed that the activity of PAO in small-sized sludge was strong,the phosphorus release in anaerobic section was 32.49 mg/L,the phosphorus absorption was 29.3 mg/L,the activity of the PAO in the large-sized ore rich sludge（3-6 mm）was poor,the phosphorus release was only 12.77 mg/L and the phosphorus absorption was 12.19 mg/L,The results show that the phosphorus removal pathway in the system of ore rich sludge is:biological phosphorus removal led by small particle sludge and chemical phosphorus removal led by large-scale rich sludge,which jointly promote the phosphorus removal efficiency of AGS system.（6）Comparative analysis of microbial flora and mechanism analysis.The abundance of bacteria with biodegradation and hydrolysis of macromolecular substances increased to 17.34%,and non functional bacteria increased to 32.39%,which led to the aging and disintegration of sludge in R1 reactor;The function bacteria Acinetobacte can improve the stability of rich-mineral sludge by secreting EPS and combining with minerals;The nitrogen and phosphorus removal bacteria with adaptability to anaerobic environment are the main bacteria for rapid recovery of pollutant removal performance of granular sludge in activity recovery experiment.（7）The AGS of mineral-rich was analyzed from the point of view of flora and sludge age.High throughput sequencing analysis confirmed that 52.3%of Acinetobacte in the inoculated sludge of R2 reactor had denitrification function,The pH value of the system was increased and the formation of AGS was stimulated;in mineral-rich AGS system of norankofenv.OPS17 is the main phosphorus removal bacteria,which combined with the enrichment of nitrogen removal bacteria and mineral precipitation promote the high nitrogen and phosphorus removal efficiency of R2 reactor;Long sludge age makes a stable mineral precipitation in sludge:Hydroxyapatite. |
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