Characterization, Spatial Variation and Management Strategy of Sewer Sediments Collected from Combined Sewer System: A Case Study in Longgang District, Shenzhen.

Yongpeng Luo,Yang Ping,Chao Lin,Siyuan Yang,Pan Yang,Shenxu Bao,Yimin Zhang

doi:10.3390/ijerph18147687

Abstract

In the urban drainage system, the formation of sewer sediments is inevitable, and the removal of sewer sediments is necessary for system maintenance. Disposal of arisings from sewer sediment removal is becoming a serious environmental issue. The current knowledge of sewer sediments is limited, which is restrained to sewer sediments management. To better understand this municipal waste, the sewer sediments of a combined sewer system in Longgang District, Shenzhen were collected and characterized, and the spatial distribution characteristics of contaminants were analyzed. Based on the bivariate correlation analysis, it is found that many contaminants in sewer sediments have a strong relationship with spatial variables. Compared to the sewer sediments in industrial areas, those in residential areas contain higher concentrations of Hg and phosphorus. The sediments in the sewage conduit also contain more organic matter (OM), phosphorus, Cu, and Ni, and the sediments in the rainwater conduit contain a higher concentration of Cd. Moreover, the sediments produced in different catchments also show huge differences in the content of contaminants. These spatial distribution characteristics may provide help for the further classification of sewer sediments, thereby making the disposal of sediments more targeted. According to the local standards of sludge disposal, land application and incineration are not suitable for managing sewer sediments due to the low OM content and poor lower heating value (LHV). Although sanitary landfill is feasible for sewer sediments disposal, the complicated composition of sewer sediments still poses the risk of polluting the surrounding environment. The management of sewer sediments via the production of building materials is a promising technical route that can avoid the migration of hazardous contaminants and produce valuable products. This study may improve our understanding of sewer sediments and provide a reliable recommendation for sewer sediment management.

Highlights

Combined sewer systems (CSS) are widely used worldwide to collect and transfer rainwater runoff, domestic sewage, and industrial effluents generated in cities [1,2]
The pH value of sewer sediments is distributed in a narrow range of 6.54 to 7.06
Bivariate Correlation Analysis indicates that sewer sediments with higher density always contain more sand and less clay, organic matter (OM), and

Summary

Introduction

Combined sewer systems (CSS) are widely used worldwide to collect and transfer rainwater runoff, domestic sewage, and industrial effluents generated in cities [1,2]. With the rainwater runoff washing and daily municipal sweeping, the dust-and-dirt of the land surface is drained via street inlets into CSS. The domestic sewage and industrial effluents discharged into the CSS carried many suspended solids. During the long-term service of CSS, these in-sewer solids are gradually deposited on the drainage channel bottom and form the sewer sediments. In the United States, it is estimated that

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