• The SRAO phenomena tended to occur only under certain conditions.• High amount of biomass and non-anaerobic condition is requirement for SRAO.• Anammox bacteria cannot oxidize ammonium with sulfate as electron acceptor.• AOB and AnAOB are mainly responsible for ammonium conversion.• Heterotrophic sulfate reduction mainly contributed to sulfate conversion. For over two decades, sulfate reduction with ammonium oxidation (SRAO) had been reported from laboratory experiments. SRAO was considered an autotrophic process mediated by anammox bacteria, in which ammonium as electron donor was oxidized by the electron acceptor sulfate. This process had been attributed to observed transformations of nitrogenous and sulfurous compounds in natural environments. Results obtained differed largely for the conversion mole ratios (ammonium/sulfate), and even the intermediate and final products of sulfate reduction. Thus, the hypothesis of biological conversion pathways of ammonium and sulfate in anammox consortia is implausible. In this study, continuous reactor experiments (with working volume of 3.8L) and batch tests were conducted under normal anaerobic (0.2≤DO<0.5 mg/L) / strict anaerobic (DO<0.2 mg/L) conditions with different biomass proportions to verify the SRAO phenomena and identify possible pathways behind substrate conversion. Key findings were that SRAO occurred only in cases of high amounts of inoculant biomass under normal anaerobic condition, while absent under strict anaerobic conditions for same anammox consortia. Mass balance and stoichiometry were checked based on experimental results and the thermodynamics proposed by previous studies were critically discussed. Thus anammox bacteria do not possess the ability to oxidize ammonium with sulfate as electron acceptor and the assumed SRAO could, in fact, be a combination of aerobic ammonium oxidation, anammox and heterotrophic sulfate reduction processes. 相似文献
Some metal etching operations emit limited flow rates of waste gases with reddish-brown NO2 fume, which may cause visual and acidic-odor complaints, as well as negative health effects. In this study, tests were performed by passing caustic-treated waste gases vented from Al-etching operations through columns packed either with virgin or regenerated granular activated carbon (GAC) to test their adsorptive conversion performance of NO2 in the gases. The gases contained 5–55 ppm NO2 and acetic and nitric acids of below 3 ppm. Exhausted carbon was regenerated by scrubbing it with caustic solution and water, and dried for further adsorption tests. Results indicate that with an (empty bed residence time (EBRT) of 0.15 sec for the gas through the GAC-packed space, around 60% of the influent NO2 of 54 ppm could be removed, and 47% of the removed NO2 was converted by and desorbed from the carbon as NO. GAC used in the present study could be regenerated at least twice to restore its capacity for NO2 adsorption. Within EBRTs of 0.076–0.18 sec, the adsorptive conversion capacity was linearly varied with EBRT. In practice, with an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)?1 with an influent NO2 of 40 ppm can be used as a basis for system design.Implications: Some metal etching operations emit waste gases with reddish-brown (yellow when diluted) NO2 fume which may cause visual and acidic-odor complaints, as well as negative health effects. This study provides a simple process for the adsorptive conversion of NO2 in caustic-treated waste gases vented from metal-etching operations through a GAC column. With an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)?1 with an influent NO2 of 40 ppm can be used as a basis for system design. Saturated GAC can be regenerated at least twice by simply scrubbing it with aqueous caustic solution. 相似文献
Journal of Material Cycles and Waste Management - Efforts to improve the performance of hydrothermal treatment (HT) in producing high-quality solid fuel from sewage sludge were carried out by... 相似文献
The purposes of this research are to quantify the concentration of heavy metals (Zn, Cu, As, Pb, Cd, and Hg) in the water and fish tissues of common carp (Cyprinus carpio) in the upper Mekong River and to thereby elucidate the potential dietary health risks from fish consumption of local residents. Surface water and fish tissues (gill, muscle, liver, and intestine) from four representative sample areas (influence by a cascade of four dams) along the river were analyzed for heavy metal concentrations. Results revealed that the levels of heavy metals in fish were tissue-dependent. The highest Cu and As levels were found in the liver; the highest Zn and Pb levels occurred in the intestine, and the highest Hg level was found in the muscle. The total target hazard quotient (THQ) value for residents is > 1 for long-term fish consumption, and local residents are, therefore, exposed to a significant health risk. Results from the current study provide an overall understanding of the spatial and tissue distribution of heavy metals in water and fish body along the upper Mekong River under the influence of cascade dams and highlight the potential health risk of As for the local residents of long-term fish consumption.
T-2 toxin (T-2), one of the naturally occurring mycotoxins, often accumulates in aquatic animals from contaminated feed. Shrimp (n?=?30 per group) were fed with different concentrations (0, 0.5, 1.5, 4.5 and 13.5?mg kg?1) of T-2 for 20?days. Changes in histopathology, fatty acid and water distribution of shrimp muscle were analyzed. Histopathology of shrimp muscle showed dose-dependent marked degenerative and necrotic changes on exposure to dietary T-2. The T-2 significantly (P?<?0.05) affected the muscle fatty acid composition. ∑SFA, ∑MUFA and ∑PUFA initially decreased and then increased slowly in the high-dosed groups. C16:0, C18:1n-9 and C18:2n-6 were the main saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively. Also, T-2 significantly affected water distribution in shrimp muscle. High doses of T-2 reduced free water content, resulting in a reduction in the water holding capacity and hence changes to the shrimp muscle quality. Collectively, these results illustrated that T-2 significantly affects the fatty acid and water distribution, and also muscle histopathology, all of which would result in a reduction in the quality and nutritional value of shrimp. 相似文献