scholarly journals Experimental Investigation into the Effect of Pyrolysis on Chemical Forms of Heavy Metals in Sewage Sludge Biochar (SSB), with Brief Ecological Risk Assessment

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 447
Author(s):  
Binbin Li ◽  
Songxiong Ding ◽  
Haihong Fan ◽  
Yu Ren
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Ecological Risk ◽  
Pyrolysis Temperature ◽  
Potential Ecological Risk ◽  
Experimental Investigations ◽  
Chemical Forms ◽  
Bcr Sequential Extraction ◽  
Measurement Results ◽  
Sequential Extraction Method

Experimental investigations were carried out to study the effect of pyrolysis temperature on the characteristics, structure and total heavy metal contents of sewage sludge biochar (SSB). The changes in chemical forms of the heavy metals (Zn, Cu, Cr, Ni, Pb and Cd) caused by pyrolysis were analyzed, and the potential ecological risk of heavy metals in biochar (SSB) was evaluated. The conversion of sewage sludge into biochar by pyrolysis reduced the H/C and O/C ratios considerably, resulting in stronger carbonization and a higher degree of aromatic condensation in biochar. Measurement results showed that the pH and specific surface area of biochar increased as the pyrolysis temperature increased. It was found that elements Zn, Cu, Cr and Ni were enriched and confined in biochar SSB with increasing pyrolysis temperature from 300–700 °C; however, the residual rates of Pb and Cd in biochar SSB decreased significantly when the temperature was increased from 600 °C to 700 °C. Measurement with the BCR sequential extraction method revealed that the pyrolysis of sewage sludge at a suitable temperature transferred its bioavailable/degradable heavy metals into a more stable oxidizable/residual form in biochar SSB. Toxicity of heavy metals in biochar SSB could be reduced about four times if sewage sludge was pyrolyzed at a proper temperature; heavy metals confined in sludge SSB pyrolyzed at about 600 °C could be assessed as being low in ecological toxicity.

scholarly journals Assessment of Heavy Metal Pollution and Potential Ecological Risk in Sewage Sludge from Municipal Wastewater Treatment Plant Located in the Most Industrialized Region in Poland—Case Study

2019 ◽  
Vol 16 (13) ◽  
pp. 2430 ◽  
Author(s):  
Malwina Tytła
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Wastewater Treatment ◽  
Risk Factor ◽  
Sewage Sludge ◽  
Ecological Risk ◽  
Treatment Plant ◽  
Potential Ecological Risk ◽  
Pollution Level ◽  
Chemical Forms

This study aimed to assess the pollution and potential ecological risk of seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in the sewage sludge collected from a wastewater treatment plant (WWTP), located in the most industrialized region of Poland (Silesian Voivodeship). The concentrations of heavy metals were determined using inductively coupled plasma optical spectrometry (ICP-OES) and cold vapor atomic absorption spectrometry (CVAAS). The chemical forms (chemical speciation) of heavy metals were determined using the three-step chemical sequential extraction procedure, developed by the Community Bureau of Reference (BCR). To assess the pollution level and potential ecological risk, the following indices were used: Geoaccumulation Index (Igeo), Potential Ecological Risk Factor (ER), Individual Contamination Factor (ICF), Risk Assessment Code (RAC), and Ecological Risk Factor (ERF)—the author’s index. Sludge samples were collected at successive stages of processing. The results revealed that the activated sludge process and sludge thickening have a significant impact on heavy metal distribution, while anaerobic digestion and dehydration decrease their mobility. The most dominant metals in the sludge samples were Zn and Cu. However, the content of heavy metals in sewage sludge did not exceed the permissible standards for agricultural purposes. The concentrations of heavy metals bound to the immobile fractions exhibited higher concentrations, compared to those bound to mobile fractions (except Zn). The values of the total indices indicated that sludge samples were moderately to highly contaminated with Zn, Hg, Cd, Cu, and Pb, of which only Hg, Cd, and Cu posed a potential ecological risk, while according to the speciation indices, sludge samples were moderately to very highly polluted with Zn, Cu, Cd, Cr, and Ni, of which Zn, Ni, and Cd were environmentally hazardous. The obtained results proved that assessment of the pollution level and potential ecological risk of heavy metals in sewage sludge requires knowledge on both their total concentrations and their chemical forms. Such an approach will help prevent secondary pollution of soils with heavy metals, which may influence the reduction of health risks associated with the consumption of plants characterized by a high metal content.

scholarly journals Migration and transformation of heavy metals during the microwave-assisted thermal hydrolysis of sewage sludge

2021 ◽  
Author(s):  
Chunsheng Qiu ◽  
Jinxin Zheng ◽  
Chenchen Wang ◽  
Bingbing Wang ◽  
Nannan Liu ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Ecological Risk ◽  
Risk Index ◽  
Oxygen Demand ◽  
Microwave Treatment ◽  
Potential Ecological Risk ◽  
Ammonium Nitrogen ◽  
Thermal Hydrolysis ◽  
Microwave Assisted

Abstract The migration, transformation and ecological risk of heavy metals (Cr, As, Ni, Cu, Zn, Cd and Pb) in the sewage sludge during the microwave-assisted thermal hydrolysis process were investigated under different temperatures (80 °C, 100 °C, 120 °C, 140 °C, and 160 °C). The potential relationship between the bio-availability of heavy metals and the variables of microwave treatment, including pH, ammonium-nitrogen, soluble chemical oxygen demand, pH, soluble protein, soluble polysaccharide and volatile solid, was also explored. The results showed that the migration of heavy metals between solid-liquid phase mainly depended on the temperature. The percentage of all heavy metals (except Cu) in mobile (acid-soluble/exchangeable and reducible) forms decreased after microwave-assisted thermal hydrolysis treatment. The solubilization of compounds with C = O and O-H accompanied with the generation of organic and inorganic metal halides were also observed in the treated sludge through fourier transform infrared spectroscopy analysis. NH4+-N showed the highest negative correlation to the bio-availability of most heavy metals (except Cu and Cr) with coefficients (absolute value) over 0.87 (P < 0.05). VS showed a positive correlation to the bio-availability of most heavy metals (except Cu). The total potential ecological risk index (RI) decreased by 46.65% after microwave treatment at 160 °C.

scholarly journals Identification of the Chemical Forms of Heavy Metals in Municipal Sewage Sludge as a Critical Element of Ecological Risk Assessment in Terms of Its Agricultural or Natural Use

2020 ◽  
Vol 17 (13) ◽  
pp. 4640 ◽  
Author(s):  
Malwina Tytła
Keyword(s):  
Heavy Metals ◽  
Risk Assessment ◽  
Sewage Sludge ◽  
Ecological Risk ◽  
Ecological Risk Assessment ◽  
Municipal Wastewater ◽  
Risk Index ◽  
Municipal Sewage Sludge ◽  
Critical Element ◽  
Chemical Forms

The present study aimed to demonstrate that identification of the chemical forms of heavy metals in sewage sludge produced in municipal Wastewater Treatment Plants (WWTPs) is a critical element of ecological risk assessment, especially in terms of its agricultural or natural use. The concentrations of seven heavy metals (Cd, Cr, Cu, Ni, Pb, Zn and Hg) were determined using inductively coupled plasma optical spectrometry (ICP-OES) and cold vapor atomic absorption spectrometry (CV-AAS). The chemical forms of heavy metals were analyzed in accordance with the sequential extraction method proposed by the Community Bureau of Reference (BCR). Sludge samples were collected at the five municipal WWTPs located in the largest industrial area in the country, i.e., the Upper Silesian Industrial Region (southern Poland, central Europe). The ecological risk was assessed by calculating the Potential Ecological Risk Factor (ER), Risk Index (RI), Risk Assessment Code (RAC), Individual Contamination Factor (ICF), Global Risk Index (GRI) as well as the author’s indices, i.e., Individual Ecological Risk (IER) and Global Ecological Risk (GER). To demonstrate the differences between the level of ecological risk posed by the different heavy metals, sludge samples were collected at two specific points of the processing line. Considering the chemical forms of heavy metals, the highest ecological risk was posed by Zn, Cd and Ni, while in the case of their total concentrations, by Cd and Hg. The obtained results confirm that quantitative determination of the total content of heavy metals in sewage sludge is not a sufficient criterion in assessment of the ecological risk that these elements pose to the natural environment and living organisms. Moreover, multivariate statistical analysis revealed a significant correlation between the concentrations of heavy metals, which indicates that they plausibly originate from the same source of pollution.

scholarly journals Influence of Temperature on Characteristics of Particulate Matter and Ecological Risk Assessment of Heavy Metals during Sewage Sludge Pyrolysis

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5838
Author(s):  
Binbin Li ◽  
Haihong Fan ◽  
Songxiong Ding ◽  
Yixuan Luan ◽  
Yiming Sun
Keyword(s):  
Heavy Metals ◽  
Risk Assessment ◽  
Particulate Matter ◽  
Sewage Sludge ◽  
Ecological Risk ◽  
Ecological Risk Assessment ◽  
Pyrolysis Temperature ◽  
Inorganic Particles ◽  
Different Temperatures ◽  
Influence Of Temperature On

The formation process of Particulate Matter (PM) during sludge pyrolysis at different temperatures (300–700 °C) and the ecological risks of heavy metals were studied. The results showed that the particulate matter is mainly condensed on the quartz film in a carbon-based organic matter when the pyrolysis temperature was between 200–500 °C in a volatilization process. Inorganic particles was found in the particulate matter when the temperature was raised to 500–700 °C in a decomposition stage. Heavy metals were enriched in particulate matter with increase in pyrolysis temperature. When the temperature reached 700 °C, the concentration of Pb and Cd in the particulate matter significantly increased. The ecological risk assessment showed that heavy metals in the sewage sludge had considerable ecological toxicity. When the pyrolysis temperature reached 700 °C, the ecological toxicity of those heavy metals enriched in the particulate matter decreased considerably.

scholarly journals Induced changes of pyrolysis temperature on the physicochemical traits of sewage sludge and on the potential ecological risks

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Claudineia de Souza Souza ◽  
Marcela Rebouças Bomfim ◽  
Maria da Conceição de Almeida ◽  
Lucas de Souza Alves ◽  
Welder Neves de Santana ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Ecological Risk ◽  
Pyrolysis Temperature ◽  
Low Cost ◽  
Risk Index ◽  
Physicochemical Characteristics ◽  
Potential Ecological Risk ◽  
Metal Mobility ◽  
Ecological Risk Index ◽  
Potential Ecological Risk Index

AbstractBiochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS and SSB450 were in the moderate and considerable contamination ranges, respectively. For all pyrolysis temperature biochar Cd was the highest metal contributor to the PERI. Despite this, the potential ecological risk index of the SS and SSBs was graded as low.

scholarly journals Pollution level and risk assessment of heavy metals in sewage sludge from eight wastewater treatment plants in Wuhu City, China

2020 ◽  
Vol 18 (2) ◽  
pp. e1103
Author(s):  
Hanwen Zhang ◽  
Yuee Huang ◽  
Shu Zhou ◽  
Liangchen Wei ◽  
Zhiyuan Guo ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Wastewater Treatment ◽  
Sewage Sludge ◽  
Correlation Analysis ◽  
Ecological Risk ◽  
Wastewater Treatment Plants ◽  
Pollution Index ◽  
Potential Ecological Risk ◽  
Potential Sources

Aim of study: To investigate the content, contamination levels and potential sources of five heavy metals (Hg, Pb, Cd, Cr, As) in sewage sludge from eight wastewater treatment plants (W1 to W8).Area of study: Wuhu, located in southeastern Anhui Province, southeastern China.Material and methods: The sewage sludge pollution assessment employed the single-factor pollution index, Nemerow’s synthetic pollution index, monomial potential ecological risk coefficient and potential ecological risk index. The potential sources among the five heavy metals were determined using the Pearson’s correlation analysis and principal component analysis (PCA).Main results: The mean concentrations of the heavy metals were 0.27 mg/kg (Hg), 70.78 mg/kg (Pb), 3.48 mg/kg (Cd), 143.65 mg/kg (Cr) and 22.17 mg/kg (As). W1, W5 and W6 sewage sludge samples showed the highest levels of heavy metal contamination, and cadmium had the highest contamination level in the study area. Pearson’s correlation analysis and PCA revealed that Pb and Cd mainly derived from traffic emissions and the manufacturing industry and that As and Cr originated from agricultural discharges.Research highlights: The pollution of cadmium in Wuhu should be controlled preferentially. The heavy metal pollution of W1, W5 and W6 sewage treatment plants is relatively high, they should be key prevention targets.

scholarly journals Ecological Risk Assessment and Contamination History of Heavy Metals in the Sediments of Chagan Lake, Northeast China

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 894
Author(s):  
Panfeng Liu ◽  
Chaojie Zheng ◽  
Meilan Wen ◽  
Xianrong Luo ◽  
Zhiqiang Wu ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Principal Component Analysis ◽  
Ecological Risk ◽  
Surface Sediment ◽  
Northeast China ◽  
Principal Component ◽  
Potential Ecological Risk ◽  
210Pb Dating ◽  
History Of ◽  
Chagan Lake

The study deals with the spatio-temporal distribution of heavy metals in the sediments of Chagan lake, Northeast China. The pollution history of heavy metals is studied simultaneously through the 210Pb dating method by analyzing the characteristic of As, Hg, Cd, Cr, Ni, Cu, Pb, and Zn concentration-depth profiles. The potential ecological risk index (RI) and geo-accumulation index (Igeo) were used to evaluate the contamination degree. Principal component analysis (PCA), based on the logarithmic transformation and isometric log-ratio (ilr) transformed data, was applied with the aim of identifying the sources of heavy metals. The element concentrations show that the heavy metals are enriched in the surface sediment and sediment core with a varying degree, which is higher in the surficial residue. The results of Igeo indicate that the Cd and Hg in the surface sediment have reached a slightly contaminated level while other elements, uncontaminated. The results of RI show that the study area can be classified as an area with moderate ecological risk in which Cd and Hg mostly contribute to the overall risk. For the sediment core, the 210Pb dating results accurately reflect the sedimentary history over 153 years. From two evaluation indices (RI and Igeo) calculated by element concentration, there is no contamination, and the potential ecological risk is low during this period. The comparative study between raw and ilr transformed data shows that the closure effect of the raw data can be eliminated by ilr transformation. After that, the components obtained by robust principal component analysis (RPCA) are more representative than those obtained by PCA, both based on ilr transformed dataset, after eliminating the influence of outliers. Based on ilr transformed data with RPCA, three primary sources could be inferred: Cr, Ni, As, Zn, and Cu are mainly derived from natural sources; the main source of Cd and Hg are associated with agricultural activities and energy development; as for Pb, it originated from traffic and coal-burning activities, which is consistent with the fact that the development of tourism, fishery, and agriculture industries has led to the continuous increasing levels of anthropogenic Pb in Chagan Lake. The summarized results and conclusions will undoubtedly enhance the governmental awareness of heavy metal pollution and facilitate appropriate pollution control measures in Chagan Lake.

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