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91.
Say Leong Ong Suhash Kumar Sarkar Lai Yoke Lee Jiang Yong Hu How Yong Ng Mark van Loosdrecht 《Water environment research》2006,78(4):372-380
The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity. 相似文献
92.
Water-soluble aerosol and visibility degradation in Hong Kong during autumn and early winter, 1998. 总被引:7,自引:0,他引:7
During the October-December 1998 period, 30 daily samples of size-separated airborne respirable suspended particulates (RSP) were collected at the quasi-rural Kadoorie Agricultural Research Centre (KARC) in central New Territories (NT), Hong Kong, Special Administrative Region (SAR). Results of analysis indicate that sulphate is the predominant water-soluble species, and that sulphate, nitrate and ammonium together contribute to most of the total water-soluble fine aerosol mass. An interesting result obtained through principal component analysis (PCA) following varimax rotation of the bivariate correlation matrix for water-soluble species is that the first component (PCl) is made up exclusively of SO4 and NH4 ions. The stoichiometric ratio and correlation coefficient between the two ions suggest that ammoniated sulphate compounds are the probable species responsible for the PCI. Further, the use of a linear multivariate visibility model which accommodates the effect of relative humidity (RH) shows that SO4 and NH4 are the only anions important in visibility degradation. It is found that SO4 in aerosol at the KARC can be used to predict the visual range (or extinction coefficient) recorded from Kings Park, Kowloon, approximately 10 km away. This result suggests that SO4 (and possibly NH4) is, generally, likely to be of regional rather than of local origin. Further observations suggest that the model is most applicable to a moderate visual range, 10 km < R(v) < or = 20 km under a rather broad range of ambient relative humidity, 40% < RH < or = 80. However, this inference does not preclude the contributions to visibility degradation--mostly by absorption--by some of the water-insoluble aerosol constituents, including carbon, or the pollutant gas, NO2. 相似文献
93.
Simultaneous removal of nitrogen oxide/nitrogen dioxide/sulfur dioxide from gas streams by combined plasma scrubbing technology 总被引:2,自引:0,他引:2
Chang MB Lee HM Wu F Lai CR 《Journal of the Air & Waste Management Association (1995)》2004,54(8):941-949
Oxides of nitrogen (NOx) [nitrogen oxide (NO) + nitrogen dioxide (NO2)] and sulfur dioxide (SO2) are removed individually in traditional air pollution control technologies. This study proposes a combined plasma scrubbing (CPS) system for simultaneous removal of SO2 and NOx. CPS consists of a dielectric barrier discharge (DBD) and wet scrubbing in series. DBD is used to generate nonthermal plasmas for converting NO to NO2. The water-soluble NO2 then can be removed by wet scrubbing accompanied with SO2 removal. In this work, CPS was tested with simulated exhausts in the laboratory and with diesel-generator exhausts in the field. Experimental results indicate that DBD is very efficient in converting NO to NO2. More than 90% removal of NO, NOx, and SO2 can be simultaneously achieved with CPS. Both sodium sulfide (Na2S) and sodium sulfite (Na2SO3) scrubbing solutions are good for NO2 and SO2 absorption. Energy efficiencies for NOx and SO2 removal are 17 and 18 g/kWh, respectively. The technical feasibility of CPS for simultaneous removal of NO, NO2, and SO2 from gas streams is successfully demonstrated in this study. However, production of carbon monoxide as a side-product (approximately 100 ppm) is found and should be considered. 相似文献
94.
Pinjing He Min Li Suyun Xu Liming Shao 《Frontiers of Environmental Science & Engineering in China》2009,3(4):404-411
This paper describes the feasibility of fresh leachate treatment by an upflow blanket filter (UBF). Through dilution and partial
effluent recycling, the organic loading rates increased from 0.51 to 14.56 kg COD/(m3·d), meanwhile the corresponding hydraulic retention time decreased from 9.0 to 3.6 d. The reactor was able to achieve steady-state
within 80 d. Based on the distribution of COD fluxes in the process, it was concluded that anabolism was the main pathway
of COD removal in the initial phase (1–33 d), accounting for 57%–85% of total COD removed. As the anaerobic consortium of
bacteria reached steady-state (after 70–86 d), the majority of COD removed was transformed into methane, because the specific
methane yield was close to the theoretical value (0.36 L CH4/(g CODdeg)). 相似文献
95.
Enzymes play essential roles in the biological processes of sludge treatment. In this article, the ultrasound method to extract enzymes from sludge flocs was presented. Results showed that using ultrasound method at 20 kHz could extract more types of enzymes than that ultrasound at 40 kHz and ethylenediamine tetraacetic acid (EDTA) methods. The optimum parameters of ultrasound extraction at 20 kHz were duration of 10 min and power of 480 W. Under the condition, ultrasound could break the cells and extract both the extracellular and intercellular enzymes. Ultrasound power was apparently more susceptive to enzyme extraction than duration, suggesting that the control of power during ultrasound extraction was more important than that of duration. The Pearson correlation analysis between enzyme activities and cation contents revealed that the different types of enzymes had distinct cation binding characteristics. 相似文献
96.
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99.
Pinjing He Na Yang Wenjuan Fang Fan Lü Liming Shao 《Frontiers of Environmental Science & Engineering in China》2011,5(2):175-185
To understand the influence patterns and interactions of three important environmental factors, i.e. soil water content, oxygen
concentration, and ammonium addition, on methane oxidation, the soils from landfill cover layers were incubated under full
factorial parameter settings. In addition to the methane oxidation rate, the quantities and community structures of methanotrophs
were analyzed to determine the methane oxidation capacity of the soils. Canonical correspondence analysis was utilized to
distinguish the important impact factors. Water content was found to be the most important factor influencing the methane
oxidation rate and Type II methanotrophs, and the optimum value was 15% (w/w), which induced methane oxidation rates 10- and
6- times greater than those observed at 5% (w/w) and 20% (w/w), respectively. Ambient oxygen conditions were more suitable
for methane oxidation than 3% oxygen. The addition of 100 mg-N·kgdrysoil−1 of ammonium induced different effects on methane oxidation capacity when conducted at low or high water content. With regard
to the methanotrophs, Type II was sensitive to the changes of water content, while Type I was influenced by oxygen content.
Furthermore, the methanotrophic acidophile, Verrucomicrobia, was detected in soils with a pH of 4.9, which extended their known living environments. 相似文献
100.
报道了农药污染对蚯蚓的群落结构与超微结构影响的研究,结果表明:随着农药污染程度增加,蚯蚓的种类和数量则减少。超微结构在扫描电镜下可观察到重污染区壮伟环毛蚓(Pheretimarobusta)胃粘膜出现溃疡灶,并产生穿孔现象;在中污染区只有微绒毛萎缩病变;在重污染区发现肠粘膜上的纤毛发生紊乱及萎缩,纤毛顶端膨大呈球形。对精子观察可见在中污染区就出现了畸形精子。在透射电镜下观察可见重污染区壮伟环毛蚓胃肠道粘膜上皮细胞中的粗面内质网(RER)出现扩张,高尔基复合体也产生扩张状,线粒体发生肿胀,线粒体嵴消失呈空泡状。另可见细胞核膜间隙扩张、断裂,核染色质边集或减少,胞质呈大片空白。蚯蚓以上病变指标均能很灵敏反映土壤农药污染程度。 相似文献