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随着城市化的快速发展,污泥作为废水生物处理工艺中不可避免的副产物[1-2],污泥产量也急速增加[3];另一方面,生物脱氮过程中存在碳源不足的问题,需要在脱氮工艺中外加碳源(甲醇和醋酸等)[4],这种做法可加剧废弃污泥的产率,不经济且不可持续。因此,寻求高效稳定的污泥预处理技术,将污泥胞内优质可生物降解有机物质充分释放[5],以胞内碳源代替外加碳源,实现污泥减量化及资源化利用,具有极其重要的意义。
近年来,国内外学者利用不同污泥预处理方法进行各种尝试和优化[6-11],其中热碱联合处理是最常用方法之一,不仅可提高污泥破解率,还可显著提高破解有机质的生物降解性[12]。代勤等[13]的研究表明,在同等条件下污泥热碱处理后的溶解性化学需氧量(SCOD)是热处理的2.18倍,而且经热碱处理污泥中的溶解性有机物相对分子质量显著减小,明显提高破解液中碳源的生物可利用性。徐慧敏等[14]尝试超声联合热碱技术破解污泥的研究中发现在最佳反应条件(温度 73.06 ℃,加碱量 0.085 g(以1 g湿污泥计),超声能量为9 551 kJ·kg−1)下,污泥破解率可达到60.411%,相较于单一碱处理、超声处理污泥破解效果明显改善,而且使得甲烷产量提高了94%。王开乐等[15]探究了将污泥碱解液用作补充碳源的可行性,发现碱解液代替外加碳源时,NO3−-N去除率达到86%以上。但在现阶段,虽然热碱法回收碳源率有所提升,但回收碳源多为溶解性有机质,污泥中其他大部分大分子非溶解性有机质(如微生物细胞膜、细胞组分和胞外聚合物(EPS)碎片等),仍然得不到充分利用。因此,尝试在热碱破解污泥将溶解性有机质充分释放的基础上,耦合机械破解将污泥中剩余非溶解性有机质碎片全部破解成超细有机颗粒悬浮于上浊液中,实现污泥碳源的高效回收和深度减量化。
基于此,本文主要利用价格低廉的CaO配合少量NaOH(pH约12±0.25),通过球磨热碱耦合法破解污泥,研究了污泥深度减量化、破解液碳源的可生化性以及代替外加碳源的反硝化脱氮效果,以期为污泥的减量化及资源化利用提供参考。
球磨热碱耦合法破解污泥-释放碳源及污泥减量化的效率
Efficiency of sludge cracking-carbon source release and sludge reduction by a ball milling-thermo-alkali coupling method
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摘要: 研究了球磨热碱耦合法破解污泥释放碳源的效率,进一步探索了直接以破解液代替外加碳源用于反硝化脱氮的可行性,并研究了该方法对污泥减量化的效果。结果表明,在水浴温度80 ℃,复合碱投加量为154 mg·g −1(以污泥VS干重计),反应24 h后,对于浓缩后含水率为93.8%的污泥,破解液中SCOD达到2.013×104 mg·L−1,COD达到4.725×104 mg·L−1。三维荧光光谱显示,污泥破解液中荧光性有机物质以易生物降解的色氨酸类和微生物代谢副产物类占据主导地位。污泥处理前后,TS由61.7 g۰L−1下降至15.6 g۰L−1,其中部分超细颗粒随上浊液回收利用,污泥减量化程度达到74.7%;VS由30.4 g۰L−1下降到4.6 g۰L−1,挥发性有机质的去除率达到84.7%。粒径分析结果表明,原始污泥中值粒径由预处理前28.1 μm降为12.6 μm,粒径显著减小,并产生2.5 μm左右的细颗粒悬浮于破解液。随后以破解污泥沉淀后的上浊液直接作为替代碳源,在模拟的反硝化实验中(外加硝酸钾作为氮源),反应器持续运行稳定后,NO3−-N的去除率均高于97.0%。以上结果表明球磨热碱耦合法是一种非常高效污泥减量化方法,破解液可有效作为反硝化碳源使用,污泥资源化和减量化效果好,是一种非常有前途的污泥处理处置方法。Abstract: In this study, the efficiency of carbon source released from sludge by a ball milling-thermal alkali coupling method was investigated, and the feasibility of directly replacing the external carbon source with the cracking solution for denitrification was further explored, as well as the effect of this method on sludge reduction. The results showed that, for the sludge with concentrated water content of 93.8%, at the water bath temperature of 80 ℃, the compound alkali dosage of 154 mg·g−1(calculated by sludge VS dry weight), SCOD and COD in the cracking solution reached 2.013×104 mg·L−1 and 4.725×104 mg·L−1 after reaction for 24 h, respectively. As indicated by three-dimensional fluorescence spectra, the fluorescent organic substances in the sludge cracking solution were dominated by easily biodegradable tryptophan and microbial metabolic byproducts. Before and after sludge treatment, the TS decreased from 61.7 g·L−1 to 15.6 g·L−1, and some ultra-fine particles were recycled with the upper turbidity solution, and the sludge reduction degree reached 74.7%. VS decreased from 30.4 g·L−1 to 4.6 g·L−1, and the removal rate of volatile organic matter reached 84.7%. As suggested by the particle size analysis results, the median particle size of the original sludge decreased from 28.1 μm ( before pretreatment) to 12.6 μm, and fine particles with a particle size of about 2.5 μm were produced and suspended in the cracking solution. Subsequently, the upper turbidity solution after sludge cracking sedimentation was directly used as the carbon source. In the simulated denitrification experiment (with the potassium nitrate added externally as the nitrogen source). Moreover, the removal rate of NO3−-N was higher than 97.0% after continuous and stable operation of the reactor. As demonstrated by the above experimental results, the ball milling-thermal alkali coupling method is a tremendously efficient sludge reduction method. Aside from that, the cracking solution can be effectively used as the denitrification carbon source owing to the satisfactory effects of sludge reclamation and reduction. Altogether, it is a considerably promising sludge treatment and disposal method.
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表 1 模拟废水营养物质组成
Table 1. Simulated nutrient composition of wastewater
指标名称 投加量/(mg·L−1) 投加药品名称 COD 200~400 葡萄糖或污泥破解液 NO3−-N 50 KNO3 TP 12 KH2PO4 碳酸氢钠 59 NaHCO3 Mg 8 MgSO4·7H2O -
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