Spectroscopic evidence for biochar amendment promoting humic acid synthesis and intensifying humification during composting.

Despite the many benefits of biochar amendment in composting, little information is available about its effects on organic matter humification during the process. In this study the analytical results for two in-vessel composting piles were compared, one amended with biochar (VPSB, pig manure+sawdust+biochar) and the other serving as a control (VPS, pig manure+sawdust). During the 74 days of humification, the increased content of humic acid carbon in VPSB is 16.9% more than that of the control. Spectroscopic analyses show a higher O-alkyl C/alkyl C ratio and aromaticity in VPSB at the thermophilic phase, and peak intensities of fulvic-like and humic-like substances were achieved faster in VPSB than VPS. These data inferred that biochar amendment promoted the neo-synthesis of humic acids and intensified the humification of pig manure. Increase in carboxylic groups of biochar as a result of oxidation reactions and sorption of humic substances may correspond to the faster formation of aromatic polymers in biochar-supplemented composting pile. The results suggest that biochar amendment might be a potential method to enhance humification during pig manure composting.

New insights into the structure and dynamics of actinomycetal community during manure composting.

Despite advancing knowledge about the functional role of actinomycetes in degrading lignocellulosic materials, definitive knowledge concerning the diversity and dynamics of the actinomycetal community in composting is still lacking. In this study, real-time polymerase chain reaction (PCR) coupled with denaturing gradient gel electrophoresis (DGGE) and clone library construction were applied to investigate actinomycetal diversity and dynamics in a pilot-scale composting. Quantitative real-time PCR data revealed that actinomycetes accounted for 18-86 % of bacteria and that the fraction peaked during the maturing phase, indicating that Actinobacteria were critical to the compost ecosystem. Qualitatively, actinomycetal communities displayed distinct temporal variations during composting. Fourteen distinct genera of actinomycetes and an unknown group were observed in manure composts. Redundancy analysis indicated that temperature exerted an influence over the actinomycetal communities. Specifically, pathogenic Corynebacterium species dominated in the initial phase, whereas the genera Saccharomonospora and Thermobifida were abundant in the thermophilic phase. In maturing composts, mesophilic Micrococcineae members were most prevalent. The dominant thermophiles along with Micrococcineae may jointly facilitate the degradation of lignocellulosic materials during composting. Together, our research revealed a more detailed ecological and potential functional role for actinomycetes in the compost ecology.

Effects of nanoscale zero-valent iron particles on biological nitrogen and phosphorus removal and microorganisms in activated sludge.

The use of nanoscale zero-valent iron (NZVI) particles in environmental remediation and wastewater treatment has recently increased. The effects of NZVI on nitrogen and phosphorus removal were examined under continuous aerobic/anaerobic conditions by employing activated sludge. NZVI did not display any measurable effect on nitrogen removal at the concentration of 50mg/L and below. However, 200mg/L of NZVI inhibited NH4(+)-N removal. The addition of NZVI at 20mg/L and above significantly (p<0.05) improved the phosphorous removal. The microbial activities were inhibited upon exposure to NZVI according to the ATP and reactive oxygen species (ROS) results. In comparison to control, the ATP content decreased by around 13%, 31% and 43% at the NZVI doses of 20, 50, and 200mg/L, respectively, probably due to ROS production under NZVI exposure. Lactate dehydrogenase (LDH) release assay suggested that NZVI concentration of 200mg/L cast adverse effects on microorganisms. Interestingly, lower concentrations of NZVI (20 and 50mg/L) boosted the dehydrogenase activity; however, approximately 19% depression in dehydrogenase activity was detected at 200mg/L. The high throughput 16S rDNA pyrosequencing results indicated that uncultured bacterial genera Sinobacteraceae, Xanthomonadaceae, Alcaligenaceae and Propionivibrio were sensitive to NZVI particles.