100 years of pheromone research

Dedicated to Prof. H. Autrum on the occasion of his 85th birthday.     

Enhanced degradation of benzo[a]pyrene by Mycobacterium sp. in conjunction with green alga

Previous work in this laboratory has confirmed that the bacteria Mycobacterium sp. strain RJGII.135 and Sphingomonas yanoikuyae strain B1 and the green alga Selanastrum capricornutum strain UTEX 1648 degrade benzo[a]pyrene (BaP) to various BaP intermediates. S. capricornutum was first grown with BaP for 4 days. The organic extract of this media was then introduced into separate cultures of strain RJGII.135 and strain B1; separate cultures were grown with BaP for comparison. Cultures grown with BaP and those grown with the algal/BaP extract showed similar mineralization patterns. The quantity of total metabolites formed was greater in bacterial cultures grown with the algal/BaP extract than those grown with BaP alone. For strain RJGII.135, only 27% of the original BaP remained in cultures grown with the algal/BaP extract; 59% remained in cultures grown with BaP. For strain B1, only 6% of the original BaP remained in cultures grown with the algal/BaP extract; 38% remained in cultures grown with BaP. These results indicate that strategies utilizing organisms together may be necessary in being able to degrade large, recalcitrant polycyclic aromatic hydrocarbons (PAHs) such as BaP.     

Influence of operating conditions on nitrous oxide formation during nitritation and nitrification

Nitrous oxide (N₂O), a strong greenhouse gas, can be produced by ammonium-oxidizing bacteria (AOB) as a by-product of ammonium oxidation and can potentially be formed in all types of nitrification processes. However, partial nitritation has been reported to cause significantly higher N₂O emissions than complete nitrification. In the study presented here, the mechanisms and factors that drive N₂O formation by AOB were investigated with respect to different operational strategies to achieve nitrite accumulation base on combined evaluation of oxygen uptake rate (OUR) and N₂O formation rate. On the one hand, N₂O formation during partial nitritation and nitrification in a continuously stirred tank reactor (CSTR) with continuous aerobic conditions was observed. On the other hand, the effect of intermittent aeration on N₂O formation during nitrification was investigated. The presence of nitrite, the extend of sludge-specific ammonium loading, low oxygen concentration, and transition from aerobic to anoxic conditions significantly increased N₂O formation in this reactor independently from each other, indicating that different formation pathways, supposedly via nitrite or hydroxylamine, were active.     

Determination of the nitrous oxide emission potential of deammonification under anoxic conditions

Various studies have been performed to determine nitrous oxide (N2O) emissions from conventional biological nitrogen removal processes in wastewater treatment like nitrification and denitrification in the main stream. However, with respect to the overall emissions of a wastewater treatment plant, part-stream treatment for high-strength wastewater (e.g., sludge liquor) is also expected to hold a significant emission potential because of high concentrations and extreme boundary conditions. This paper presents results from a laboratory-scale study on nitrous oxide production by biomass from a deammonification process (nitritation + anammox) under anoxic conditions. It was discovered that N2O formation results from incomplete endogenous denitrification rather than anammox and is dependent on substrate availability. Based on direct measurements of the dissolved N2O concentrations in a sequencing batch reactor, the dynamic behavior of N2O production is characterized in more detail. The results show that, during anoxic conditions, the N2O emission potential of deammonification is significantly lower than from conventional denitrification.     

Growth dynamics of Chinese wingnut (Pterocarya stenoptera) seedlings and its effects on soil chemical properties under simulated water change in the Three Gorges Reservoir Region of Yangtze River

Pterocarya stenoptera is a native deciduous tree species and a candidate for reforestation in the riparian zones of the Three Gorges Reservoir Region of Yangtze River in China. Water treatments of continuous flooding (CF) and periodic flooding–drought (PF) were applied to examine the growth dynamics of 4-month-old P. stenoptera seedlings and its effects on soil chemical properties. Results showed that P. stenoptera seedlings in both CF and PF significantly decreased leaf biomass accumulation and the height and diameter growth as compared to that in control (CK; treatment with well-watered, well-drained soil), respectively. There was no significant difference in stem biomass among the three groups, but root biomass in PF showed severe reduction compared to that in both CK and CF. Total biomass in PF was significantly decreased compared to that in CK, but comparable to that in CF. Furthermore, no significant difference was found between CF and CK in total biomass. Water treatments in the unplanted soil pots significantly influenced soil pH, soil organic matter (OM), total nitrogen (TN), and alkali hydrolysable nitrogen (AN) contents, in contrast to no significant effects in total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available potassium (AK) contents. In P. stenoptera soils, there were significant effects by water treatment, time, and treatment × time in the eight tested soil chemical properties, except treatment in TK and time effect in OM content. Compared to unplanted soils, the growth of P. stenoptera seedlings significantly increased soil pH value and OM, TN, TP, and TK contents, while decreasing AN, AP, and AK contents in CK group, augmented the mean value of each of the tested soil chemical properties with an exception of AK content in CF group, and increased soil pH value and TN, AN, TP, and AP contents with no significant differences in OM, TK, and AK contents in PF group. Given the fact that TN and TP contents significantly increased in P. stenoptera soils as compared to those in unplanted soils, growth of P. stenoptera seedlings should be a successful candidate for restoration within the highly dynamic hydrologic zone of the riparian zones of the Three Gorges Reservoir Region.     

Engineering,Operation and Maintenance of Electrostatic Precipitators on Open Hearth Furnaces

The photochemical reaction of various olefins and nitrogen dioxide was studied under conditions of controlled temperature, pressure, and humidity in a 200 liter stirred glass reactor. The hydrocarbon concentration in the reactor during four and five hour irradiation periods was monitored with a flame ionization chromatograph. Reaction rate constants, based on three consecutive first order reactions, were calculated for reactor temperatures of 20, 25, 30, and 35 degrees centigrade. Activation energies for the three consecutive reactions were calculated from the Arrhenius equation. Branched and straight chain olefins were studied at initial concentrations of 5.0 to 10.0 parts per million.s