Self-recycling of sewage sludge as a coagulant and mechanism in sewage sludge dewatering
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ORIGINAL ARTICLE
Self‑recycling of sewage sludge as a coagulant and mechanism in sewage sludge dewatering Jiahuan Wu1,2,3,4,5 · Tao Lu1,2,3 · Guang Yang5 · Wei Meng5 · Haoran Yuan1,2,3 · Yong Chen1,2,3 Received: 19 February 2019 / Accepted: 24 June 2020 / Published online: 22 September 2020 © Springer Japan KK, part of Springer Nature 2020
Abstract The properties of sewage sludge-derived biochar (BC) pyrolyzed at 300–900 °C were characterized, and which exhibited the basic properties of coagulant. When 1 g BC500 was added to 100 mL waste-activated sludge (WAS), the maximum mean settlement rate reached 8.20 mL min−1 within 10 min, and the volume of the settlement with settling time decreased to 13 mL. The capillary suction time of BC500 (12 s) was superior to those of municipal solid waste incineration (MSWI) fly ash (13.40 s), coal fly ash (14.20 s), and activated carbon (12.20 s). In addition, added BC may reduce the moisture content of sludge cake, especially for BC500. It can be that soluble cations and organic functional groups neutralize the negative charge of WAS which is helpful to shorten settling time. Meanwhile, the pore structure is beneficial for reducing moisture content of sludge cake. As results shown, BC was feasible to improve sewage sludge dewatering used as a coagulant. Keywords Biochar · Characteristics · Coagulant · Pyrolysis · Sewage sludge Abbreviation V Volume of the settlement with settling time
Introduction Sewage sludge is highly heterogeneous, and contains both organic and inorganic matters [1]. Because of the high organic matter content (38.40 ± 12.70%), sewage sludge Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10163-020-01083-6) contains supplementary material, which is available to authorized users. * Haoran Yuan [email protected] 1
Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, People’s Republic of China
2
CAS Key Laboratory of Renewable Energy, Guangzhou 510640, People’s Republic of China
3
Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development, Guangzhou 510640, People’s Republic of China
4
University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
5
Shenzhen Gas Corporation Ltd., Shenzhen 518049, People’s Republic of China
should not be reconsidered as waste, but rather as a raw energy resources or other biodegradable materials [2–6]. Dewatering is a key step for sludge resource disposal, further energy and resource utilization [7]. Flocculants or coagulants are widely used to treat wastewater and enhance sludge dewaterability for a long time [8, 9]. However, traditional inorganic flocculants and synthetic polymeric flocculants produced from oil-based products may cause potential secondary pollution. For instance, some coagulant aids (e.g., fly ash, rice husk, lignite, and coal fly ash) have recently been investigated in detail. Hwa and Jeyaseelan [6] adopted fly ash as a skeleton builder, and foun
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