Process and characteristics of carbon source release from excess sludge via high temperature digestion

doi:10.16085/j.issn.1000-6613.2019-0568

Abstract

Abstract:

Aimed to meet the requirements of biological nitrogen and phosphorus removal for those wastewaters with low C/N ratio, more and more attention has been paid to the development of internal carbon source via excess sludge. In this study, the characteristics of carbon source releasing under different digestion temperature were investigated, and the effects of sludge digestion on the molecular weight distribution of organic compounds was also studied. As the temperature was raised from 40 to 60℃, the reduction of volatile solids (VS) improved significantly, and the concentration of soluble chemical oxygen demand (SCOD) in digestion supernatant presented a significant increase. Raising the temperature can facilitate the release of internal carbon source from the sludge. For the reactor with digestion temperature of 60℃, the short chain fatty acids (SCFAs) at 120h was 8797mg/L, and the ratio of C/N (presented by SCOD/TN) and C/P (presented by SCOD/TP) were 11.7与38.2, respectively. Thus, the digestion supernatant can meet the requirement of carbon source in the process of biological nutrient removal. Digestion temperature significantly affects the molecular weight distribution of organic compounds during sludge digestion process, and those soluble microbial by-products can be transformed into other metabolic intermediate components under thermophilic digestion condition, and the macromolecules may be smoothly converted to small molecular intermediates. As digestion time exceeded 120h, the macromolecules with M _w＞100000 in the digestion substrate presented a downward trend, and the small molecules with M _w＜10000 gradually increased, but the total amount of SCFAs in the supernatant declined, which was not conducive to the accumulation of internal carbon sources.

Key words: excess sludge, internal carbon source, digestion temperature, short chain fatty acids, metabolic intermediate

摘要：

为适应低C/N废水生物脱氮除磷的需求，利用剩余污泥开发内碳源备受重视。本文研究了不同温度条件下污泥消化过程内碳源释放进程的变化特征，探讨了污泥消化过程对上清液中有机物分子量分布的影响。研究表明：消化温度由40℃升至60℃时，污泥挥发性固体物（VS）减量化效果及消化液中化学需氧量（SCOD）浓度明显增加，高温条件有利于污泥内碳源的释放。60℃消化处理120h时，污泥消化体系短链脂肪酸（SCFAs）总量为8797mg/L，C/N（以SCOD/TN表示）、C/P（以SCOD/TP表示）分别达到11.7与38.2；消化温度对污泥上清液中有机物分子量分布影响显著，并使微生物副产物、有机质大分子物质更容易转化为其他代谢中间组分和小分子中间产物。若消化时间超过120h，污泥上清液中M _w＞100000的大分子物质呈下降趋势，M _w＜10000的小分子物质所占比例逐步增加，但SCFAs总量也呈降低趋势，不利于污泥内碳源的累积。

关键词: 剩余污泥, 内碳源, 消化温度, 短链挥发性脂肪酸, 代谢中间产物

CLC Number:

X703

Fang CHEN,Shugen LIU,Qunchao WANG,Yongfeng JIA,Ping NING. Process and characteristics of carbon source release from excess sludge via high temperature digestion[J]. Chemical Industry and Engineering Progress, 2019, 38(08): 3917-3924.

陈芳,刘树根,王群超,贾永锋,宁平. 高温消化条件下污泥内碳源释放进程及特性[J]. 化工进展, 2019, 38(08): 3917-3924.

Figures/Tables 7

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理化指标	测试值	理化指标	测试值
pH	7.1	TP/mg·L^-1	18.6
TS/g·L^-1	55.5	TN/mg·L^-1	48
VS/g·L^-1	43.5	NH₄ ⁺-N/mg·L^-1	7
SCOD/mg·L^-1	269	SCFAs/mg·L^-1	未检出
Ortho-P/mg·L^-1	17.1

理化指标	测试值	理化指标	测试值
pH	7.1	TP/mg·L^-1	18.6
TS/g·L^-1	55.5	TN/mg·L^-1	48
VS/g·L^-1	43.5	NH₄ ⁺-N/mg·L^-1	7
SCOD/mg·L^-1	269	SCFAs/mg·L^-1	未检出
Ortho-P/mg·L^-1	17.1

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