双氰胺对污泥堆肥过程中酶活性和细菌群落演变的影响

鉴于氮肥增效剂在农田中的保氮经验，研究其对堆肥中氮素的保持具有重要意义.因此，本研究以氮肥增效剂-双氰胺（Dicyandiamide， DCD）为添加剂，脱水污泥为堆肥原料，进行了20 d的堆肥试验，探讨DCD对堆肥过程中氮素转化和酶活性变化及其细菌群落演变的影响.结果表明，DCD的添加降低了堆肥高温期的温度，延长了高温期的持续天数；DCD组显著降低了高温期NH₄-N的含量和整个时期NO₃-N的含量.堆肥结束时，总氮含量与对照相比提高了14.8%.此外，DCD的添加抑制了高温期纤维素分解酶和蛋白酶的活性，抑制了整个过程的硝酸还原酶的活性，而且高温期时，DCD组中厚壁菌门和绿弯菌门的丰度显著低于对照.冗余分析表明，NH₄-N、pH和温度主要影响高温期时酶的活性，NO₃-N和总氮主要影响稳定期时酶的活性.综上所述，DCD通过降低高温期的微生物丰度和相关酶活性，减缓了高温期的氨化作用和后期的硝化作用，减少了氮素损失，是一种可行的污泥堆肥添加剂.

Effects of dicyandiamide on enzyme activity and the structure of bacterial community during sewage sludge composting

Considering nitrogen fertilizer synergist for reducing nitrogen loss in farmland, it is of great significance to explore the nitrogen conservation during composting process. Therefore, a 20 d composting experiments of sewage sludge, including control and dicyandiamide (DCD) addition, were established to investigate the influences of DCD on nitrogen conversion, enzyme activity and the succession of bacterial community during composting process. The results show that DCD decreased the temperature and prolonged the duration of the thermophilic stage. The DCD treatment significantly decreased the NH₄-N content during thermophilic stage and NO₃-N content during the whole composting process. At the end of composting, the total nitrogen content increased by 14.8% compared to the control. In addition, the addition of DCD inhibited the activity of cellulase and protease, and decreased the abundances of Firmicutes and Chloroflexi during thermophilic stage relative to control. The activity of nitrate reductase during the whole composting process was also inhibited due to the DCD addition. Redundancy analysis results showed that NH₄-N, pH and temperature significantly affected the enzyme activity during the thermophilic stage, while NO₃-N and total nitrogen mainly affected the enzyme activity during maturation stage. In conclusion, DCD could slow down ammonification during thermophilic stage and nitrification during the cooling and maturation stages, and reduce nitrogen loss through decreasing microbial abundance and related enzyme activities during thermophilic stage. Thus, DCD is a feasible additive for the sewage sludge composting.