RESUMEN
This study aimed to treat real wastewater from the desulfuration and denitration process in a petrochemical plant with high-strength nitrogen (TN≈200 mg/L, > 90% nitrate), sulfate (2.7%) and extremely low-strength organics (CODCr < 30 mg/L). Heterotrophic denitrification of multistage anoxic and oxic biofilm (MAOB) process in three tanks using facultative denitrifying bacteria inoculum was developed to simultaneously achieve desirable effluent nitrogen and organics at different hydraulic retention time (HRT) and carbon to nitrogen (C/N) mass ratios. The optimum condition was recommended as a C/N ratio of 1.5 and a HRT of A (24 h)/O (12-24 h) to achieve > 90% of nitrogen and organics removal as well as no significant variation of sulfate. The denitrifying biofilm in various tanks was dominant by Hyphomicrobium (8.9%-25.7%), Methylophaga (18.6%-25.8%) and Azoarcus (3.3%-19.6%), etc., containing > 20% aerobic denitrifiers. This explained that oxic zone in MAOB process also exhibited simultaneous nitrogen and organics removal.
Asunto(s)
Desnitrificación , Aguas Residuales , Reactores Biológicos/microbiología , Bacterias , Sulfatos , Biopelículas , Nitrógeno , Óxidos de Azufre , Carbono , NitrificaciónRESUMEN
This study focused on the application of salt-tolerant denitrifying bacteria (DBA) in an optimized biofilm process to treat high sulfate-nitrate wastewater from lab-scale to pilot-scale. Lab-scale results demonstrated the salinity, DBA inoculum, supplementary carbon and phosphorus source significantly varied the startup periods at the range of 36-74 d, and the optimum initial start-up conditions were as follows: >0.6 g/L of DBA, 2-4 of C/N ratio, 0.3-0.6 mg/L of phosphorus and a salinity-gradient domestication method. A pilot scale of biofilm technology with DBA was further developed for treating real wastewater from the desulfuration and denitration with both high nitrate (≈200 mg/L) and sulfate (2.7%). The denitrification efficiency reached above 90% after one-month gradient-salinity of 0.5%-2.7%. Mature biofilm had dominant genera Hyphomicrobium (31.80%-61.35%), Methylotenera (0.85%-20.21%) and Thauera (1.42%-8.40%), etc. Notably, the largest genera Hyphomicrobium covered the complete denitrification genes.
Asunto(s)
Nitratos , Aguas Residuales , Sulfatos , Desnitrificación , Biopelículas , Fósforo , Óxidos de Azufre , Tecnología , BacteriasRESUMEN
PURPOSE: To analyze the accuracy of implant position in simple cases by freehand. METHODS: Ninety-seven implants of 68 patients from 3 surgeons were selected.After operation,the deviations of implant position at shoulder apex and angle were measured using cone-beam CT(CBCT).The mean of three parameters were calculated with SPSS 22.0 software package, and the differences were analyzed between three surgeons,three operation areas,free-end missing and non free-end missing. RESULTS: The deviations of 97 implants were (0.76±0.57)mmï¼(1.41±0.90)mmï¼(4.76±3.68)° at shoulder, apex and angle.The deviation of shoulder apex and angle between three surgeons was significantly different(P<0.05). The deviations between left and right group were not significantly different (P>0.05); the deviations between anterior group and left group were significantly different(P<0.05); the deviations between anterior group and right group were not significantly different(P>0.05). The deviation of shoulder between free-end missing area and non free-end missing area was significantly different(P<0.05),other parameters between the two groups were not significantly different(P>0.05). CONCLUSIONS: The deviation of implant placement between surgical guide and mental guide were similar in simple cases. The experience of surgeon was important during freehand implant placement. The deviations were lower when missing tooth is in anterior area than in posterior area, whereas the same at shoulder in non free-end missing area than in free-end missing area.
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Implantes Dentales , Cirugía Asistida por Computador , Algoritmos , Tomografía Computarizada de Haz Cónico , Implantación Dental Endoósea , HumanosRESUMEN
This article reports a clinical case of an 8-year-old boy who sustained avulsion of the maxillary right central incisor and the maxillary left lateral incisor. The avulsed teeth were kept in adverse extraoral dry conditions for 1â¯h from the moment of trauma until their replantation. The prognosis of tooth replantation is dependent on multiple factors such as methods of teeth storage in vitro, endodontic intervention, extra-oral time, and type of retention employed. The main reasons for root resorption in this case may be the extra-oral time, the initial replantation, or the delayed endodontic treatment.
Asunto(s)
Incisivo , Conservación de Tejido/normas , Avulsión de Diente/cirugía , Reimplante Dental/normas , Niño , Desecación , Humanos , Masculino , Factores de Tiempo , Reimplante Dental/métodosRESUMEN
PURPOSE: To evaluate the influence of the time of deep caries on eruption of premolars. METHODS: Children in kindergarten in 2010 was selected to check caries of deciduous molars, then baseline data of population and personal oral health records were established. After data collection, from 2010 to 2017, according to the age of deep caries in deciduous molars, they were divided into 4 groups: four-year, five-year, six-year and seven-year. SPSS 20.0 software package was applied to analyze the results. RESULTS: Between 2010 and 2017, 994 children were investigated, including 528 boys and 466 girls. A total of 1220 maxillary first deciduous molars, 1307 maxillary second deciduous molars ,1244 mandibular first deciduous molars and 1253 mandibular second deciduous molars were investigated. At the age of 4 to 7, when the maxillary and mandibular deciduous molars suffered from deep caries, the replacement time of the premolars was earlier than cases with no caries. The difference was statistically significant (P<0.05); When deciduous molar decay occurred in young children, premolars had a tendency to erupt earlier, especially deciduous molars developed deep caries before 5 years, the difference was statistically significant (P<0.05). CONCLUSIONS: Prevention and intervention of dental caries in children is very important. Especially for children under 5 years old, caries in children's molars need early treatment, in order to decrease the impact on normal replacement of permanent teeth.
Asunto(s)
Diente Premolar , Caries Dental , Erupción Dental , Niño , Preescolar , Femenino , Humanos , Masculino , Diente Molar , Diente PrimarioRESUMEN
The formation and characterization of the aerobic 4-chloroaniline-degrading granules in the three column-type sequencing batch reactors were investigated in this paper. The granular sludge was observed since 15 days after start-up in R2 and R3 which had the high ratio of height to diameter (H/D). Since then and within the subsequent 75 days, the granulation of aerobic sludge was apparently developed by the decreased settling time and gradually increased 4-chloroaniline (4-ClA) concentration to above 400 mg.L(-1) in R1 to R3. The aerobic granules tended to be mature in all reactors continuously operated with 4-ClA loading rates of around 800 g.m(-3).d(-1), and the removal efficiencies of chemical oxygen demand, total nitrogen, and 4-ClA were maintained above 93%, 70%, and 99.9%, respectively. Mature aerobic granules in R1 to R3 featured with the average diameter of 0.78, 1.68, and 1.25 mm, minimal settling velocity of 20.5, 70.1 and 66.6 m.h(-1), specific 4-ClA degradation rates of 0.14, 0.21, and 0.27 g.gVSS(-1).d(-1), and the ratio of proteins to polysaccharides of 8.2, 10.8, and 13.7 mg.mg(-1), respectively. This study demonstrates that the reactor with a high H/D ratio and internal circulation favors the granulation and stabilization of aerobic sludge.