| Engineered nano materia ls are commo nly used in commerc ia l and industr ia l products nowadays. As a result of increasing demand and consumpt ion,a greater amount of nanopartic les(NPs) containing products event ua lly reach wastewater treatme nt pla nts, sludge and land fill. There fore, the study on the impact of N Ps on anaerobic digest ion process is necessary.The experiment invest igaed the impacts Zn O-N Ps on different stages of s ludge anaerob ic digest ion,and the effects on microbia l communit ies. The results he lp eva luat ing the inhib itory effects of na nopart icles on anaerob ic digest ion process.The results showed that Zn O-N Ps affect the anaerobic digestion of sludge hydrolyt ic acid ificat ion process in a certain extent.In this stud y, 0,2,30,60,90,120, 150 mg/ g- VSS was chosen as the investigated concentrations to assess the gas product ion, volat ile acids, organic matter degradation effic ienc y, slud ge reduction change,and to analys is the effects of Zn O-NPs on the activit ies of key enzymes.After 3 days exposes, dissolved components of carbohydrates, protein and SCO D degradat ion e ffic ienc y decreased as the concentrations of Zn O-N Ps gradually increased. The total volat ile acids concentration d id not change significant ly. When Zn O-NPs exposure concentrat ion is fro m 0 to 150mg/ g- VSS,the percent of H2 and CH4 in the total gas product io n from 4.98%,0.98% rised up to 30.63%,9.67%.The percent of CO2 fro m 95.01% declined to 58.23%.Zn O-N Ps inhibited methanoge nic stage of sludge anaerobic digest ion, relative ly. Zn O-NPs Zn O-NPs resulted in reduct ion of gas product ion, SCO D and TCO D remova l rate and R(VSS/T SS). SCO D remova l rate, TCO D remova l rate and R(VSS/T SS) va lue decreased to 3%, 36.5% and 74% of those of control.S ludge reduct ion rate was reduced from 23% to 4.8% of those of control when t he Zn O- NPs concentratio n from 2 mg/ g- VSS to 150 mg/ g- VSS.VSS reduct ion rates, proteins and polysaccharides reductio n rate decreased as Zn O-NPs concentration increased.Zn O-NPs could inhib ited the activit y o f protease, cellulase and Coenzyme F420 in a certain e xtent. Low exposure concentrat ions of Zn O-N Ps had less impact on the activit ies of key enzymes, and a relat ive greater inhib itory at the higher concentration.Zn O-NPs had greater effects on metha neproducing enzyme tha n hydro lys is enzyme.The impacts of Zn O-N Ps on microbial communit y were characterized b y using high- throughput sequenc ing.The abundance of Archaeal in order are:0<30<90<150,on the contrary, the abundance of Archaeal in order to 0>30>90>150.It can be seen that abundance of archaeal community increased,and communit ies of bacteria abundance dec lined while Zn O-NPs concentrat ion increased.Difference ana lys is of communit y Biodiversit y showed that the systems can be affected by Zn O-NPs, and appeared on the cluster ing of difference, and the difference of bacteria l and archaeal co mmunit ies increased wit h Zn O-N Ps concentrations e levated.Community str ucture ana lys is on different le vels o f samp les discovered: Met hanom icrobia were the most dominant species in Archaea community, Met hanobacteria and Therm oplasm ata were the second. Wit h the concentrations of Zn O-N Ps increased the abundance Methanom icrobia dropped 10.87%, 13.4%, 21.65%,repective ly,result ing in decrease of metha ne- production effic iency.In the control group Clostridia, Anaerolineae, Bact eroidia were the dominant bacteria l communit y, When Zn O-NPs were at the concentrat ion of 30,90,150g/g- VSS, Clost ridia was 13.11%, 20.61%,12.29%, respective ly, Bacteroidia communit ies were 9.75%, 14.92%, 16.14%, but the Anaerolineae communit ies were 18.89%,3.62% and 16.14%,respectively. These shows that Zn O-NPs can promote the activity of Clost ridia and Bact eroidia,inhabited but the Anaerolinea of A naerolineae,which can degradates macromo lecular compounds at Anaerobic digest ion syste m. |
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