Study On The Efficiency Of Modified Expanded Granular Sludge Blanket Reactor In Treating Papermaking Wastewater

With the increase in the use of domestic boxboard paper and the promotion of water saving and emission reduction policies in the paper industry,a large amount of Ca²⁺and refractory organic pollutants in the papermaking wastewater have accumulated,resulting in calcification of particulate sludge in the anaerobic section of the wastewater treatment process and reduction of COD removal capacity of anaerobic reactor,which reduce the operating efficiency and life of traditional anaerobic reactor in papermaking wastewater treatment.Improving the traditional anaerobic reactor,delaying the calcification of anaerobic granular sludge,and improving the pollutant removal capacity of the anaerobic reactor has become an urgent problem to be solved.In this study,an modified anaerobic expanded granular sludge bed reactor was used,and compared with the traditional anaerobic granular sludge expanded bed,the modified anaerobic granular was analyzed through the operation process of the two reactors for treating papermaking wastewater.The applicability of the modified anaerobic granular sludge expanded bed to treat papermaking wastewater and its improvement on sludge calcification were analyzed,and the following conclusions were drawn:(1)Reactor operation effectThe volume load of the modified anaerobic granular sludge expanded bed was increased from 8 kg COD/(m³·d)to 16 kg COD/(m³·d),and the volume load was stable at 16 kg COD/(m³·d),the COD removal rate was about 65%,and the p H,VFA,SS of effluent were normal,and the average calcium retention rate was 43.42%;the volume load of the traditional anaerobic granular sludge expanded bed was reduced from the initial 8 kg COD/(m³·d)to 4 kg COD/(m³·d),the COD removal rate decreased from about 60%to only 8.72%,and the VFA was as high as 20 mmol/L.The calcium retention rate was as high as 41.63%on average.The system of reactor was in a state of paralysis with the internal acidification in the reactor was serious,the effluent quality was unstable,and mud running occurred.The improved anaerobic granular sludge expanded bed had higher volume load,higher COD removal rate and stable operation than the traditional anaerobic granular sludge expanded bed.(2)Activity and degree of calcification of granular sludge in the reactorAt the end of operation,the VSS/TSS,calcium content,and hydrochloric acid insoluble content of the granular sludge at each sampling port of the modified anaerobic granular sludge expanded bed were:1#sampling port 26.81%,60.61%,8.57%,2#sampling port 46.92%,45.89%,4.58%,3#sampling port 49.01%,41.8%,4.7%;the VSS/TSS,calcium content,and hydrochloric acid insoluble content of the granular sludge at each sampling port of the traditional anaerobic reactor were:1#sampling port 3.9%,81.53%,10.57%,2#sampling port 8.76%,76.18%,11.06%,3#sampling port 15.77%,70.76%,8.45%,4#sampling port 18.75%,71.03%,7.47%.During the same operation time,the granular sludge in the modified anaerobic granular sludge expanded bed had high volatile solid content and low calcification,indicating that the modified anaerobic granular sludge expanded bed could improve the severe calcification of granular sludge in the traditional anaerobic granular sludge expanded bed and extend the life cycle of granular sludge to treat papermaking wastewater.(3)Analysis of microbial communityAfter the operation,the sludge in the inoculated sludge,the modified anaerobic granular sludge expanded bed and the traditional anaerobic granular sludge expanded bed(respectively marked as Z0,ZN,ZT)were subjected to microbial high-throughput sequencing.The 7 dominant bacteria phylum and its compositions were Chloroflexi(48.36%,55.61%,43.39%),Bacteroidetes(16.08%,11.31%,27.74%),Euryarchaeota(5.19%,6.01%),respectively.%,3.83%),Proteobacteria(4.72%,5.23%,4.09%),Firmicutes(5.50%,3.74%,4.29%),Actinobacteria(1.93%,1.45%,1.99)%),and Planctomycetes(1.91%,2.81%,0.00%),respectively.The most genera in Z0,ZN and ZT was Anaerolineaceae,which accounted for 44.20%,52.06%,and 43.72%,respectively.The other most bacterial genera were Methanothrix,Levilinea,Pelolinea,Desulfovibrio,Leptolinea,Thermogutta,Sulfurovum.Methanothrix increased a lot in modified anaerobic granular sludge expanded bed.The abundance,diversity and species distribution uniformity of the granular sludge microbial community in the modified anaerobic granular sludge expanded bed were better than those of the traditional anaerobic granular sludge expanded bed from the?diversity index analysis.From the microbiological point of view,it showed that the modified anaerobic granular sludge expanded bed could improve the calcification of granular sludge,increase the activity of granular sludge,extend the life cycle of granular sludge,and provide a theoretical basis for the higher COD removal rate of modified anaerobic granular sludge expanded bed.