城市污泥与调理剂混合堆肥过程中有机质组分的变化

Dynamic of organic matter fractions during sewage sludge and bulking agent composting

【目的】研究城市污泥堆肥过程中各项有机质组分及碳、氮在堆肥过程中的形成与转化,以期改善堆肥的生物有效性,促进其土地利用。【方法】在工厂规模化下,以城市污泥、蘑菇渣锯末以及返混料按照6∶3∶1的质量比混合形成堆肥物料,辅以强制通风措施和翻抛,进行为期18 d的高温堆肥试验。堆肥期间定期采样,测定指标包括温度、C/N值、p H、含水率、有机质降解率、水溶性组分、半纤维素、纤维素和木质素,研究堆肥期间不同阶段堆肥物料中有机质组分的动态变化。【结果】堆体温度随着发酵时间的延长呈现先升高后降低的趋势,最高温度达到71.3℃;含水率由60.7%降低到51.4%,p H呈现先升高后降低的趋势,总体处于6.0 7.5之间;总有机碳含量持续下降,氮素含量表现为高温期持续下降随后呈上升的趋势;初始阶段,堆肥物料中四种成分含量分布为:水溶性组分>纤维素>半纤维素>木质素,至堆肥结束变化为:纤维素>水溶性组分>木质素>半纤维素,经过堆肥之后水溶性组分及半纤维素含量分别由39.5%和20.1%下降为27.9%和14.4%,纤维素含量由初始的21.8%上升至29.5%,木质素含量相对稳定不变。物料经过堆肥化处理后达到腐熟标准,水溶性组分和半纤维素含量分别降低了38.6%和38.8%,纤维素和木质素含量在高温期分别降解了11.7%和18.5%;物料总量降低了9.8%。水溶性组分的主要降解阶段为高温期,期间降解部分占总降解量的65.5%;半纤维素的主要降解阶段为稳定期,稳定期降解部分占总降解量的69.1%,且有继续降解的趋势;纤维素和木质素仅在高温期有少量降解;氮素则表现为高温期铵态氮的损失及稳定期硝态氮的积累。【结论】堆肥化处理在实现污泥减量化基础上,污泥中有机质得到了稳定化,有利于城市污泥的土地利用。

【Objectives】The study for transformation of organic matters,total organic carbon,and total nitrogen in sewage sludge is of considerable importance. The objective is to improve the biological availability of compost and promote its land-application process. 【Methods】The composting experiment was conducted with forced aeration and turning in the factory,and the overall work lasted for 18 days. The pile was composed of sewage sludge,bulking agent（ mushroom and saw-dust mixture）,and compost in mass ratio of 6 ∶ 3 ∶ 1. Samples were taken at different times during the composting process. Temperature in real-time,C / N ratio,p H,moisture,and organic matter degradation were determined throughout the period. In particular,the transformations of water soluble organic matter,hemicellulose,cellulose,and lignin were monitored. 【Results 】 During the progress of theexperiment,windrow temperature rapidly reached up to 71. 3℃ and lasted for 5 days,then declined to the normal level gradually. Meanwhile,the p H of windrow showed the same trend with temperature,ranging from 6. 0 to 7. 5.In addition,moisture continuously reduced from 60. 7% to 51. 4%. Properties of the windrow were within the range of composting standard after period work. Total organic carbon content descended in the whole period,whereas total nitrogen content decreased by the end of thermophilic phase and then increased gradually. In the initial phase,four organic fractions in the windrow were distributed as follows： water-soluble fraction cellulose hemicellulose lignin. After the compost process,the distribution changed to： cellulose water-soluble fraction lignin hemicellulose. The water-soluble fraction and hemicellulose reduced from 39. 5% and 20. 1% to 27. 9% and14. 4%,respectively. Cellulose content reached 29. 5% from 21. 8%,and lignin content was stable in the period.According to the results,compost experiment reached the standard requirement. This result indicated that watersoluble organic matter and hemicellulose were the main energy and material sources to microbe. Contents of water soluble organic matter,hemicellulose reduced by 38. 6% and 38. 8%,respectively. The reduction of cellulose and lignin were 11. 7% and 18. 5%,respectively. Finally,the mass decrement of the pile was 9. 8%. Water-soluble organic matter was mainly degraded in the thermophilic phase,and 65. 5% of reduction occurred in this phase.However,hemicellulose was mainly degraded in the stable phase,and 69. 1% of reduction occurred in this phase.At the same time,a small amount of cellulose and lignin were degraded in thermophilic phase because of their complex structure. Organic carbon was transformed to inorganic carbon in the whole period. Ammonia nitrogen was lost in the thermophilic phase,whereas nitrate nitrogen accumulated in the stable phase. 【Conclusions 】The composting process rendered the sewage sludge,stabilized and reduced. Moreover,the process increased the biological availability of sludge,which promotes the feasibility of the land application of sludge.