[Nitrification and Bioaugmentation of Biological Treatment System of Sewage Treatment Plant at High Temperature in Summer].

The influence of temperature (30-45℃) and ammonia-nitrogen volume load on the nitrification function and microbial community of activated sludge in an aerobic tank of a sewage treatment plant were investigated under simulated high-temperature stress in the summer. Meanwhile, the bioaugmentation effectiveness of the middle-temperature-enriched nitrifying sludge (with or without acclimation) was evaluated in two biological treatment systems under high-temperature shock. The results showed that the ammonium-nitrogen (NH-N) removal efficiency and the nitrifying bacteria content of the aerobic activated sludge at 30-40℃ were above 90% and up to 4.

[Pollution Characteristics and Emission Coefficients of Volatile Organic Compounds from the Packaging and Printing Industry in Zhejiang Province].

This paper presents the raw material composition and VOC treatment status of the packaging and printing industry in Zhejiang Province based on the survey data obtained in 2015 of 254 packaging and printing enterprises. To analyze the emission characteristics and calculate the emission coefficients of the packaging and printing industry, 100 typical enterprises were further screened according to different printing processes. The results showed that about two-thirds of packaging and printing enterprises failed to effectively dispose of VOCs; meanwhile, solvent-based materials were still commonly used in the packaging and printing industry.

[Pilot-scale Experiment on Enrichment of Nitrifying Activated Sludge and Its Application in Enhancing a Wastewater Biological Treatment System Against Ammonia Shocking Loads].

Nitrifying activated sludge (NAS) was enriched in a membrane bioreactor (MBR) with pre-treated municipal wastewater and additional ammonium sulfate as the culture medium. The influences of temperature, dissolved oxygen (DO), ammonia nitrogen volumetric load, free ammonia (FA), and free nitrite (FNA) on the enrichment of NAS were investigated, the cost of the process was evaluated, and then NAS's application in enhancing a wastewater biological treatment system against ammonia shocking loads was attempted. The results showed that after 182 days of cultivation in an MBR, NAS had a nitrification activity of 98.

[Removal of Mixed Waste Gases by a Biotrickling Filter Packed with a Novel Combined Packing Material].

A pilot biotrickling filter (BTF) was set up for removal of a mixed waste gas containing toluene and ethanol. The packing material was composed of polyhedral sphere and polyhedral hollow column previously designed by our group. The results showed this BTF could successfully start up within only 8 d and the average eliminate capacities for toluene and ethanol were 97.

[Treatment of organic waste gas by adsorption rotor].

The adsorption rotor is applicable to treating organic waste gases with low concentration and high air volume. The performance of adsorption rotor for purifying organic waste gases was investigated in this paper. Toluene was selected as the simulative gaseous pollutant and the adsorption rotor was packed with honeycomb modified 13X molecular sieves (M-13X).

[Removal of toluene from waste gas by honeycomb adsorption rotor with modified 13X molecular sieves].

The removal of toluene from waste gas by Honeycomb Adsorption Rotor with modified 13X molecular sieves was systematically investigated. The effects of the rotor operating parameters and the feed gas parameters on the adsorption efficiency were clarified. The experimental results indicated that the honeycomb adsorption rotor had a good humidity resistance.

[Performance evaluation of three novel biotrickling packings].

Packing is the support medium for microbial adhesion and water retention, and its characteristics are directly related to the removal of pollutants. In the present study, three novel biotrickling packings were developed: polyhedral sphere, burr sphere and polyhedral hollow column. The results showed that the structural characteristics of polyhedral sphere and polyhedral hollow column, with the specific surface area of 200 m2 x m(-3), were better than those of traditional biotrickling packings.

[Preparation and electro-catalytic characterization on La/Ce doped Ti-base lead dioxide electrodes].

Ti-base lead dioxide electrodes (Ti/PbO2) doped with rare earth La, Ce were prepared by the electrode position. The surface morphology and crystal structure of the electrodes was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), the results showed that, microstructure and crystal orientation of electrode surface changed after doping rare earth La, Ce, which made the electrode surface more dense and uniform. The electrochemical properties of the electrodes were tested by linear sweeping (LS) and cyclic voltammogram (CV), the experimental results show that, La, Ce doping improved the electrode overpotential of oxygen evolution and the peak current density, promoted the catalytic performance of the electrode.

[Bacterial biofilm on the apical external root surfaces of human teeth associated with chronic periradicular lesions].

Objective: To investigate the patterns of microbial infection on the apical external root surfaces of treated and untreated teeth associated with chronic apical periodontitis and to study bacteria in the biofilm in order to find out the species, constitution and origination of bacteria in periapical biofilm.

Methods: Ten teeth with chronic apical periodontitis from patients of the Department of Stomatology of People's Hospital, Peking University: 5 untreated teeth with a radiographically visible chronic periradicular lesions and 5 teeth with extensive carious lesions, radiolucent lesions of varying sizes and attached periradicular tissues were selected for study. Using aseptic techniques and sterile instruments, bacterial samples of the root canals were taken, inoculated and separated according to usual practice.

[Prevalence of dental erosion and associated drinks in 12-year-old population of Beijing].

Objective: To investigate the prevalence of dental erosion and associated drinks in 12-year-old adolescence of Beijing.

Methods: A random sample of 12-year-old adolescence of Beijing (n=844) was examined for dental erosion and required to fill a questionnaire of acidic drink intake. The grade criteria suitable for the survey of the dental erosion was used in the study.

[Clinical effects of calcium hydroxide-based sealer on chronic apical periodontitis].

Objective: To evaluate the results of calcium hydroxide-based sealer Sealapex in the treatment of chronic apical periodontitis.

Methods: A total of 100 cases with chronic apical periodontitis were included and divided into two groups, calcium hydroxide sealer (Sealapex) group and ZOE sealer group, and Sealapex and ZOE sealer were respectively used. All cases were followed up for two years after treatment and the clinical results compared between the two groups.

[A three-dimensional finite element analysis of 0.02 taper 20# stainless steel K files during root canal instrumentation].

Objective: To investigate the stress distribution of stainless steel K (SSK)files during root canal instrumentation.

Methods: A three-dimensional finite element model was established and analyzed under curved and torsional conditions by ANSYS 9.0.

[Clinical effect of the restoration for pathological tooth wear].

Objective: To investigate the effect of the restoration for pathological tooth wear.

Methods: A total of 48 pathological weared premolars and molars with restorable space in occlusal surface in 10 patients were restored by composite resins. The patients' masticatory function (biting force, masticatory efficiency, the surface electromyographic (EMG) activity of masseter muscles and anterior temporalis) were compared before and after the treatment.

[The correlation between the enlargement of root canal diameter and the fracture strength and the stress distribution of root].

Objective: To investigate the correlation between the extent of cutting of the root canal wall and the root fracture strength and the stress distribution.

Methods: Fifteen pairs of root sections were into 3 groups with canal wall thickness of 1.00 mm, 0.

Removal of dichloromethane from waste gases by a biotrickling filter.

Dichloromethane is harmful to human health and hazardous to atmospheric environment. In this study, two strains were isolated which were identified as Pseudomonas sp. and Mycobacterium sp.

[Establishment of the three-dimensional finite element model of the first permanent mandibular molar and its stress analysis].

Objective: To establish more rational three dimensional finite element model (FEM) of the first permanent mandibular molar and to study the internal stress distribution.

Methods: The FEM was applied to analyze the stress distribution of the first permanent mandibular molar under various loading conditions.

Results: Under all five loading conditions, the maximum von-Mises stress and compressive stress in enamel were larger than that in dentin, and the tensile stress in enamel was smaller than that in dentin.

[Preliminary study of tooth measured by a noncontact 3D image survey system].

Objective: To perform the quantitative study of tooth occlusal surface wear by a noncontact 3D image survey system.

Methods: Thirty-two old people's complete dental casts in five years which had normal occlusion were studied. The same way was used to determine the individual reference surface, and the range of the maxillary first molar occlusal surface was delimited by the unite regulation.

[Enamelin transcriptional expression in developing postnatal rat tooth germ].

Objective: To observe the transcriptional expression of enamelin in developing postnatal rat first mandibular molar germs, for further studies of functions of enamelin in enamel development and mineralization.

Methods: Tissue slices of first mandibular molar germ of rat 1, 3, 7, 10, 14 days after birth were prepared. The enamelin mRNA expression was identified by in situ hybridization.