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Sewage sludge (SS) production in China has increased rapidly, accompanying the fast expansion of its sewage treatment capacity. Heavy metals (HMs) in SS have been a great concern, hampering the utilization and disposal of SS. In this study, heavy metal (HM) contents in SS from throughout China were determined. The median values of HMs in SS decreased in the order Zn > Cu > Cr > Pb > Ni > As > Hg > Cd. The general attainment rates of HMs in SS are satisfying (> 90%). Combining the present data with those obtained from references, spatial distributions and temporal trends of HMs in SS were analyzed. Depending on the specific HM element, the spatial variation trend might be decreasing trends from south to north and from east to west of China. The element-specific hot spots of SS with relatively high HM contents were identified. Analysis of the historical data in different time intervals reviewed obvious decreasing trends in HM contents of SS in China, indicating the well implementation of more and more stringent environmental regulations. [ABSTRACT FROM AUTHOR]

Occurrence and fate of sewage- and sludge-borne total mercury (THg) and methylmercury (MeHg) have received little attention, although they might be an important component of the global Hg inventory. To address the knowledge gap, sewage and sewage sludge (SS) samples were collected from a secondary municipal sewage treatment plant (MSTP) located in Jiaozuo, China. Total Hg in the raw sewage varied between 95.3 ng/L and 1.2 × 103 ng/L, while MeHg occurred in the sewage within ranges of 2.7-21.3 ng/L. On average, 93.4% of THg and 89.1% of MeHg were removed from the raw sewage by the MSTP. Around 80% of net THg input into the MSTP was transported to the SS, while 80% of net MeHg input was decomposed during the treatment processes. Thus, MSTPs would be regarded as an important sink of sewage-borne THg and MeHg. On the other hand, MeHg widely occurred in the SS, with concentrations between 7.2 and 10.2 ng/g, accounting for 0.2% of the corresponding THg contents in the SS. Occurrence of THg and MeHg in the SS indicated that SS would be a significant source of MeHg and THg to the environment. [ABSTRACT FROM AUTHOR]

Municipal wastewater treatment plants (WWTPs) play an important role in controlling pollutant discharges to surface waters. Previous studies suggested that the removal of mercury (Hg) by WWTPs was strongly correlated with solid removal. However, conclusions regarding possible transformations of Hg species within WWTPs were not consistent across those studies. We characterized total Hg (THg) and methylmercury (MeHg) concentrations and loads in a WWTP located in Jiaozuo, China, to further understand Hg fate and transformations in WWTPs. THg and MeHg were primarily associated with wastewater solids, and removal of both were greater than 90%; concentrations in the sewage were (2.0 ± 2.7) × 10 3 ng/L and 7.5 ± 5.8 ng/L, respectively. A mass balance calculation revealed that 80% of the THg input to the WWTP ended up in the sewage sludge (SS), while more than 70% of the influent MeHg mass was degraded, indicating WWTPs are an important sink for sewage-borne Hg. THg and MeHg concentrations in SS were (3.9 ± 1.4) × 10 3 ng/g and 6.3 ± 2.3 ng/g, respectively, suggesting SS could be a significant source of THg and MeHg to the environment if not handled properly. The significance of sewage and SS in the biogeochemical cycling of THg and MeHg in China is discussed. [ABSTRACT FROM AUTHOR]

Municipal sewage has been identified to be an important source of mercury (Hg) to the environment. However, as the major sink of sewage-borne Hg, sewage sludge (SS) remains unresolved in terms of the occurrence status of Hg species. We presented here, a nation-wide survey on the speciation of Hg in SS of China. Total Hg (THg) and methylmercury (MeHg) were detected in all SS samples, within ranges of 0.4–12.4 mg/kg and 0.1–27.0 μg/kg, respectively. Sludge-borne Hg mainly occurred in the mercury sulfide and organo-chelated phases, with only tiny portions occurring as soluble Hg. The mass loadings of sludge-borne THg and MeHg in China for year 2016 were estimated to be 12.2 metric tons and 19.9 kg, respectively. Landfill was the most important sink of sludge-borne Hg, followed by incineration, land application, and building materials. Image 1 • Speciation analysis was performed for Hg in the sewage sludge of China. • Total Hg and methylmercury were detected in all the sewage sludge samples. • Hg in the sewage sludge mainly occurred as sulfide and organo-chelated fractions. • Landfill was the most important sink of sludge-borne Hg in China. [ABSTRACT FROM AUTHOR]

Current knowledge about the transformation of total mercury and methylmercury (MeHg) in aerobic composting process is limited. In this study, the composition and transformation of mercury and dissovled organic matter (DOM) in aerobic composting process of municipal sewage sludge were were comprehensively characterized, and the differences among the three C/N ratio (20, 26 and 30) were investigated. The main form of mercury in C/N 20 and 26 was organo-chelated Hg (F3, 46%-60%); while the main form of mercury in C/N 30 was mercuric sulfide (F5, 64%-70%). The main component of DOM in C/N 20 and 26 were tyrosine-like substance (C1, 53%-76%) while the main fractions in C/N 30 were tyrosine-like substance (C1, 28%-37%) and fulvic-like substance (C2, 17%-39%). The mercury and DOM varied significantly during the 9 days composting process. Compared to C/N 20 and 26, C/N 30 produced the less MeHg after aerobic composting process, with values of 658% (C/N 20), 1400% (C/N 26) and 139% (C/N 30) of the initial, respectively. Meanwhile, C/N 30 produced the best compost showed greater degree of DOM molecular condensation and humification. Hg fraction had been altered by DOM, as indicated by a significant correlation between mercury species and DOM components. Notably, C/N 30 should be used as an appropriate C/N ratio to control the methylation processes of mercury and degration of DOM. [ABSTRACT FROM AUTHOR]

• Seven key androgens (i.e., testosterone and testosterone isocaproate) were identified in high-risk sludges. • Testosterone cypionate was reported, for the first time, in sewage sludge. • Twenty out of thirty sludges revealed androgenic activity, raising pivotal concerns on potential hazards. • Androgenic compounds together accounted for 52 % – 87 % of activity in the most polluted sludges. The safety of municipal sewage sludge has raised great concerns because of the accumulation of large-scale endocrine disrupting chemicals in the sludge during wastewater treatment. The presence of contaminants in sludge can cause secondary pollution owing to inappropriate disposal mechanisms, posing potential risks to the environment and human health. Effect-directed analysis (EDA), involving an androgen receptor (AR) reporter gene bioassay, fractionation, and suspect and nontarget chemical analysis, were applied to identify causal AR agonists in sludge; 20 of the 30 sludge extracts exhibited significant androgenic activity. Among these, the extracts from Yinchuan, Kunming, and Shijiazhuang, which held the most polluted AR agonistic activities were prepared for extensive EDA, with the dihydrotestosterone (DHT)-equivalency of 2.5 – 4.5 ng DHT/g of sludge. Seven androgens, namely boldione, androstenedione, testosterone, megestrol, progesterone, and testosterone isocaproate, were identified in these strongest sludges together, along with testosterone cypionate, first reported in sludge media. These identified androgens together accounted for 55 %, 87 %, and 52 % of the effects on the sludge from Yinchuan, Shijiazhuang, and Kunming, respectively. This study elucidates the causative androgenic compounds in sewage sludge and provides a valuable reference for monitoring and managing androgens in wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Mercury (Hg) that leaches from municipal sewage sludge (MSS) landfill under natural rain is of increasing concern. The column leaching experiments were conducted to investigate the leaching characteristics of total mercury (THg) and methylmercury (MeHg) as well as pH, total organic carbon (TOC), and total suspended solids (TSS) in the raw sludge (RS) and lime-conditioned sludge (LCS) under simulated rain with different acidities (pH 6.5 and 2.9). Results showed the release of MeHg in the leachates presented different patterns from THg. And the final amounts of MeHg in the MSS columns were 1.49 (RS at pH = 6.5), 1.88 (RS at 2.9), 1.97 (LCS at pH = 6.5), and 2.06 times (LCS at pH = 2.9) higher than the initial amounts, suggesting methylation of inorganic Hg (IHg) occurred in the leaching process. The leaching efficiencies of THg and MeHg in RS was lower than that in LCS, indicating lime was more favorable for the release of THg and MeHg. And lower values of pH of the simulated rain promoted the release of THg and MeHg from RS while the opposite was true for LCS. This study provides a better understanding of the release and biogeochemical transformations of Hg in MSS. • Leaching characteristic of MeHg was different from THg in the landfill. • The effects of simulated rain on the release of MeHg and THg differed in raw sludge and lime-conditioned sludge. • Lime treatment was more favorable for the release of MeHg. • Methylation of inorganic mercury in a column leaching experiment was observed. [ABSTRACT FROM AUTHOR]