Identification of Specific Organic Compounds in a Highly Anoxic Sediment by Gas Chromatographic-Mass Spectrometry and High Resolution Mass Spectrometry
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The sediment of the Charles River Basin (an exclusively anaerobic system) was analyzed by computerized gas chromatographic-mass spectrometry (GC-MS) and high resolution mass spectrometry (HRMS). The organic compounds were separated first by methylene chloride extraction followed by gradient chromatography on alumina. This analysis revealed a large number of aliphatic and olefinic hydrocarbons, elemental sulfur, various and abundant polycyclic aromatic hydrocarbons (PCAH) and their alkyl derivatives, and two phthalate esters. Since the PCAH were the most abundant single class of compounds, their identification was pursued in detail. Possible sources of these compounds in the aqueous environment are petroleum, incomplete combustion, anaerobic biosynthesis, or chemical dehydrogenation of natural products.Continuous laboratory experiments have confirmed that the construction of the USSB reactor was suitable for the combination of several biological wastewater treatment processes and that both anaerobic and denitrifying anoxic granules could be cultivated inside a compact reactor. The anoxic granules were transformed from the anaerobic granules after the shift from anaerobic to anoxic conditions in the upper compartments of the USSB reactor. The denitrification in such a system can be very intensive and efficient because of the high concentration of the sludge in anoxic compartments, and the high activity of the sludge due to a high and stable temperature. The denitrification rate of 62 mg N/l.h (at 35 degrees C) was achieved in spite of COD-limited conditions in the anoxic compartment of the USSB reactor. Maximum specific activity of anoxic granules 47 mg N/g VSS.h (at 35 degrees C, with glucose as substrate) was found in batch tests. The anoxic granules originating from the anaerobic granules have still demonstrated a significant methanogenic activity comparable with the anaerobic granules.
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GRAPHICAL ABSTRACTMass spectral studies of 1-(2-chloroethoxy)-2-[(2-chloroethyl)thio]ethane and related compounds using gas chromatography–mass spectrometry (GC-MS) and gas chromatography–triple quad mass spectrometry (GC-QQQ)All authorsFu-Lian Hsu, Mark D. Winemiller & Su Y. Baehttps://doi.org/10.1080/10426507.2015.1119145Published online:09 May 2016
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Abstract A laboratory‐scale anaerobic/anoxic/oxic reactor system was used to treat synthetic brewery wastewater for 1 year. The objectives were to enhance denitrifying phosphorus removal, improve biological nutrient removal and reduce operating costs. Three operational strategies were tested: (1) controlling nitrate recirculation to stimulate the growth of denitrifying phosphate‐accumulating organisms; (2) adjusting the volume ratio of the anaerobic/anoxic/oxic zones to enhance anoxic P uptake; (3) bypassing a part of the influent flow into the anoxic zone to maximise anoxic P uptake and denitrification. The results showed that not only was anoxic P uptake enhanced but also energy consumption for aeration could be reduced when the anoxic effluent NO 3 − ‐N concentration was controlled between 1 and 3 mg L −1 . The optimal volume ratio of the anaerobic/anoxic/aerobic zones in this system was found to be 1:1:2. The optimal bypass flow ratio was 0.32. The results indicated that the optimal strategies could improve treatment performance and reduce operational costs, but there was still a challenge to treat wastewater with low C/N ratio. Copyright © 2006 Society of Chemical Industry
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The study focuses on decarbonization and nitrification theory and parameters of Anoxic-Aerobic BAF techniques.The impact of COD,NH3-N and TN removal performance were established considering hydraulic loading.The test result indicated that anoxic section of Anoxic-Aerobic BAF was vital for COD,NH3-N and TN removal.In order to obtain the best processing effect,the anoxic section must maintain the height scope of 500-600mm.When the Anoxic-Aerobic BAF hydraulic loading was 2-3 m/h,the ratio of the anoxic section volume to the aerobic one was 1:3,and the COD,NH3-N and TN have the best removal effect.The conclusion is that the increase of the hydraulic loading of Anoxic-Aerobic BAF leads more dissolved oxygen to anoxic section with the backflow intermixture and enhances the water perturbation in filters,strengthens reaerationon in the column,destroys the anoxic section filters in the column.It is disadvantageous to the denitrification and the total nitrogen removal.
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Anoxic zones in biological nitrogen removal systems are typically open to the atmosphere and receive oxygen from the atmosphere and the recirculation flow from the aerobic zone. This raises the question of how such oxygen input might influence the stability and inducibility of the enzyme systems involved in biodegradation of aromatic compounds. To investigate this, various amounts of oxygen were added to mixed culture denitrifying chemostats receiving benzoate at 667 mg/h as chemical oxygen demand (COD), and the stability and inducibility of the culture's benzoate biodegradative capability (BBC) were tested in aerobic and anoxic fed-batch reactors (FBRs). Cultures from chemostats receiving oxygen at 0, 33, 133, 266, and 466 mg O2/h lost almost all of their anoxic BBC within one hour after being transferred to an aerobic FBR and the first three cultures did not recover it upon being returned to anoxic conditions. The last two cultures recovered their anoxic BBC between 9 and 16 h during the 16 h aerobic exposure period that preceded their return to anoxic conditions and continued to increase their anoxic BBC as they were retained under anoxic conditions. In contrast, the culture from a chemostat receiving oxygen at 67 mg O2/h retained its anoxic BBC longer, recovered it within 3 h after its return to anoxic conditions, and increased it linearly thereafter. None of the cultures developed any aerobic BBC during the 16 h aerobic exposure period in FBRs. The results suggest that higher oxygen inputs into anoxic reactors helped the mixed microbial cultures recover and/or induced anoxic BBC more easily when they were exposed to alternating aerobic/anoxic environments. The exceptional behavior of the culture from the chemostat receiving oxygen at a rate of 67 mg O2/h may have been caused by the presence of a protective mechanism against the toxic forms of oxygen.
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The nitrate nitrogen in the sludge can be removed by first anoxic district of modified A2O technology.The bio-denitrification in first anoxic district was an important way for total nitrogen(TN) removal in system.Based on modified A2O technology in Kunshan astewater Treatment Plant(WWTP),the ways and quantity of TN removal were analyzed by quantitative methods.TN removal was the most happened in the first anoxic district and traditional anoxic district,where contribution rate of NO-3 were 51% and 42%,respectively.The average quantity of NO-3 in the first anoxic district was 132kg/d,correspondingly the rate of removal was up to 81.5%.However,the rate of mixed liquid recycles was excess for bio-denitrification in the traditional anoxic district.The rate of mixed liquid recycles was suggested reducing to 150%.As an important way for TN removal in preposing denitrification,the TN removal relationship between traditional anoxic and first anoxic should be balanced in order to meet TN discharge standard.
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