Nitrous oxide and methane emissions from different treatment processes in full-scale municipal wastewater treatment plants.

Nitrous oxide (N2O) and methane (CH4) are two important greenhouse gases (GHG) emitted from biological nutrient removal (BNR) processes in municipal wastewater treatment plants (WWTP). In this study, three typical biological wastewater treatment processes were studied in WWTP of Northern China: pre-anaerobic carrousel oxidation ditch (A+OD) process, pre-anoxic anaerobic-anoxic-oxic (A-A/ A/O) process and reverse anaerobic-anoxic-oxic (r-A/ A/O) process. The N2O and CH4 emissions from these three different processes were measured in every processing unit of each WWTP. Results showed that N2O and CH4 were mainly discharged during the nitrification/denitrification process and the anaerobic/anoxic treatment process, respectively and the amounts of their formation and release were significantly influenced by different BNR processes implemented in these WWTP. The N2O conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 10.9% and 18.6% lower than that of A-A/A/O process and A+OD process, respectively. Similarly, the CH4 conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 89. I% and 80.8% lower than that of A-A/ A/O process and A+OD process, respectively. The factors influencing N2O and CH4 formation and emission in the three WWTP were investigated to explain the difference between these processes. The nitrite concentration and oxidation-reduction potential (ORP) value were found to be the dominant influencing factors affecting N2O and CH4 production, respectively. The flow-based emission factors of N2O and CH4 of the WWTP were figured out for better quantification of GHG emissions and further technical assessments of mitigation options.

[Study on the degradation kinetics of spiramycin in acid and alkaline solutions].

Physical and chemical characteristics of spiramycin (SPM) were reviewed in this paper. The degradation rule and kinetics of SPM in acid and alkaline solutions were studied, and the kinetic parameters were calculated. The experimental results showed that the stable range of SPM in water is at pH 4.0~10.0 Degradation occurred seriously at pH<4.0 and pH> 10.0, especially at pH< 2.8 and pH> 12.8. For this reason, the yield of SPM is greatly affected. The solubility in water was also studied by using reference data. The thermodynamical parameters were calculated. The results showed that the solution of SPM in water is exothermic. The solubility decreases as temperature rises.