Metal Content Of Sludge Research Articles

Analysis of Heavy Metal Contaminants and Mobility in Sewage sludge-soil Mixtures for Sustainable Agricultural Practices

This study presents a comprehensive analysis of the potential utilization of sewage sludge in agriculture, focusing on the assessment of heavy metal contaminants and their mobility in sewage sludge-soil mixtures. The innovative approach of investigating heavy metal fractions in these mixtures sheds light on their environmental implications. In this study, sludge and soil samples from three different soil categories were collected, and the mobility of heavy metals was investigated using sequential BCR analysis. A thorough assessment of the risk of environmental contamination associated with the agricultural use of sludge was also carried out. This study included the calculation of various risk indicators, such as the Geoaccumulation Index of heavy metals in soil (Igeo), the risk assessment code (RAC), and the author’s element mobility ratio (EMR), which included a comparison of the overall metal concentrations in sludge, soil, and mixtures. This study demonstrates that the key to using sludge is to know the form of mobility of the metals present in the sludge and how they behave once they are introduced into the soil.

The function of “Cambi® thermal hydrolysis + anaerobic digestion” on heavy metal behavior and risks in a full-scale sludge treatment plant based on four seasons investigation

The environmental risk of heavy metals in sewage sludge from a full-scale “Cambi® thermal hydrolysis + anaerobic digestion” sludge treatment plant was discussed based on four seasons’ data. Results showed that the order of heavy metal concentration in sludge was Zn > Cu > Cr > Ni > As > Pb > Hg > Cd, which all increased significantly due to the “enrichment effect” caused by the degradation of organics. Nevertheless, the mass of heavy metals except for Cd decreased. Chemical fractions of different heavy metals in raw sludge varied greatly. The proportion of their residual fraction all increased slightly after treatment. Thermal hydrolysis and anaerobic digestion led to the transformation of some heavy metal fractions. Deep dehydration process reduced the mass of heavy metals from sludge (less than 10%). Potential ecological risk of heavy metals was low (RI <150) when sludge is applied 0.75 kg/m2 to soil according to GB 4284–2018, in which the risk of Hg and Cd was highest. Furthermore, the accumulation amounts of heavy metals in test soil and rural soil with the annual sludge application amount of 0.75 kg/m2 for 15 years were calculated, which did not exceed GB 36600–2018 and GB 15618–2018 respectively.

Evaluating granulometry and metal content in sludge from UASB reactors treating sugarcane vinasse

Few studies have been carried out on sludge blankets in treatment systems. However, the sludge blanket in a UASB system is the area where microorganisms responsible for converting organic matter into biogas are concentrated. Considering its importance, the present research aimed to study the sludge blanket of three UASB reactors used in the treatment of sugarcane vinasse (pilot scale). The main difference between them was the applied effluent recirculation rate (100 %, 200 %, and 400 %). The research objective was to analyze the sludge blanket of these reactors: to determine the granulometry; the concentration of zinc, lead, cadmium, nickel, iron, manganese, copper, total chromium, calcium, magnesium, sodium, and potassium; and the organic and inorganic contents, aiming to identify the physical-chemical alterations in the sludge caused during the operational period. A reduction in the granular diameter was observed in all systems up to the range between 0.4 and 1 mm, provided by the increase in the hydraulic load, the organic loading rate and biogas production, and the increase in the mineral fraction in the sludge blanket, associated with the metal contribution of vinasse to the sludge blanket. Metal accumulation such as magnesium, sodium, calcium, and potassium was not detrimental to the methanogenic process due to the strategy of adapting biomass to vinasse, by gradually increasing the vinasse load, and the effects of antagonisms between magnesium and sodium and between potassium and sodium, which reduced its toxic effects.

Risk Analysis of Heavy Metals Migration from Sewage Sludge of Wastewater Treatment Plants.

More and more attention in sewage sludge management is being devoted to its environmental utilization. This approach is justified both from economic and environmental points of view. However, as with any method, there are certain possibilities and limitations. The goal of the natural utilization of sewage sludge is to recover the valuable agronomic properties and fertilizing potential of the sludge. The main aspect limiting the possibility of using sludge as a fertilizer is the heavy metal content. In this paper, an analysis of the risk of environmental contamination in the case of application of sewage sludge with different forms of sludge treatment was carried out. Risk indices such as Igeo and PERI, based on the comparison of total metal content in sludge and soil, as well as RAC and ERD indices, which take into account the mobility of metals in soil, were calculated. It was shown that high levels of potential risk and geoaccumulation indicators do not necessarily disqualify the use of sewage sludge, the key aspect is the form of mobility in which the heavy metals are found in the sludge, and this should be the only aspect taken into account for the possibility of their environmental use.

Biomass production, metal and nutrient content in sorghum plants grown on soils amended with sewage sludge

Sludge generation from wastewater treatment plants in Uruguay has increased in recent years. Agricultural soils may be a final destination. A greenhouse experiment was conducted to quantify the effect of this sludge on 1) plant biomass production and nutrient concentration of sorghum (Sorghum bicolor var. vulgare); 2) the chemical properties of amended soils; and 3) assess whether heavy metal concentrations in sludge are appropriate according to environmental regulations. Two soils (S1 and S2) were amended with pure sludge (PS) and limed sludge (LS), with low dose (LD) of 16.0 and 17.3 Mg ha−1 and high dose (HD) of 32.0 and 34.6 Mg ha−1, respectively. Sludge treatments increased plants' nutrient absorption and dry matter production. The LS treatments incremented plant biomass production, depending on soil pH and nutrient availability. The effect of sludge treatments on elemental concentration in aboveground biomass depended on the element, treatments, and soil type. Mineralized nitrogen (N) and plant available phosphorus (P-Bray 1) values increased with sludge addition without exceeding Uruguay's critical soil level of P-Bray 1 for the sorghum crop. The PS did not increase metal concentration in soils. The LS slightly decreased soil Pb and slightly increased Cr and Zn soil concentration; levels were according to Uruguayan environmental guidelines. Therefore, agriculture soils are a viable final destination for PS and LS. Land applied sludge has acceptable levels of metals and promotes crop development.

Biomass Production, Metal And Nutrient Content in Sorghum Plants Grown on Soils Amended with Sewage Sludge

Sludge generation from wastewater treatment plants in Uruguay has increased in recent years. Agricultural soils may be a final destination. A greenhouse experiment was conducted to quantify the effect of this sludge on: 1) plant biomass production and nutrient concentration of sorghum plants ( Sorghum bicolor var. vulgare); 2) the chemical properties of amended soils; and 3) assess whether heavy metal concentrations in sludge are appropriate according to environmental regulations. Two soils (S1 and S2) were amended with pure sludge (PS) and limed sludge (LS), with low dose (LD) of 16.0 and 17.3 Mg ha -1 and high dose (HD) of 32.0 and 34.6 Mg ha -1 respectively. Sludge increased plants' nutrients absorption and dry matter production. Lime addition to PS favored production, its increment depended on soil pH and on its impact on nutrient availability. Sludge effect on elements concentration in aboveground biomass, depended on the element, treatments and soil type. The mineralized N and residual P-Bray 1 values increased with the addition of sludge, without exceeding the critical level of P-Bray 1 of the crop. The PS did not increase metal concentration in soils. The LS slightly decreased soil Pb and slightly increased Cr and Zn soil concentration; levels were according to Uruguayan environmental guidelines. Therefore, agriculture soils are a viable final destination for both PS and LS. Sludge has acceptable levels of metals and promotes crop development.

Organic polyelectrolytes as the sole precipitation agent in municipal wastewater treatment

In municipal wastewater treatment, inorganic coagulants (IC), e.g. polyaluminium chloride (PAC), are normally used to remove pollutants such as dissolved and particulate nutrients, in a process called coagulation/flocculation. However, IC use has been linked to issues e.g. in effluent water post-treatment, sludge management and disposal (IC increase sludge volume and metal concentrations in sludge), etc., raising uncertainties about their overall cost-efficiency and environmental benefits. In this study, the suitability of organic coagulants (OC) as sole precipitation agents to replace IC (PAC) was investigated. A total of 10 synthetic (i.e. polyDADMACs and polyamines) and semi-natural (chitosan, starch, and tannin-based) OC products were tested in treatment of samples from primary sedimentation and secondary sedimentation stages of municipal wastewater treatment, and their performance was compared with that of PAC. The study was conducted using the jar test methodology. The coagulants were tested for their ability to remove target pollutants (e.g. BOD7, COD, SS, tot-P, PO4-P, tot-N) and form rapidly settling flocs. In general, higher (up to 60%) coagulant doses were needed in treatment of secondary wastewater samples than primary samples. In comparison with the OC doses required for effective treatment, the PAC doses were higher (up to 80%). In treatment of secondary wastewater samples, OC with high molecular weight (MW) and high charge density (CD) (e.g. pAmine1) achieved best removal of target pollutants (e.g. 72% SS, 87% PO4-P, 88% BOD7), followed by PAC. In treatment of primary wastewater, PAC performed best (removing e.g. 96% SS, 96% PO4-P), closely followed by chitosan and polyamine products. Based on these results, polyamine products with high MW and (very) high CDs have the potential to act as the sole precipitation agent in both primary and secondary stages of municipal wastewater treatment. Further research is needed to determine the effect of residual coagulant on downstream water and sludge treatment processes (e.g. activated sludge process, sludge dewatering, etc.).

Assessing the quality of sewage sludge as an agricultural soil amendment in Mediterranean habitats

PurposeMunicipal sewage sludge generated from three operational wastewater treatment plants, located in the Bekaa valley of Lebanon, was assessed for its potential use as agricultural soil amendment.MethodsSludge samples were taken from three treatment plants located in the villages of Iaat, Ablah and Joub Jannine during the summer season of 2018, from June to September, on a monthly basis. The evaluation was based on characterizing the physicochemical parameters such as the metal content, the pathogenic microorganisms (Salmonella, E.Coli, Staphylococcus aureus, Helminth eggs, Ascaris, Acinetobacter) and the phytotoxicity–stability indicators of the sludge samples.ResultsThe obtained results were compared to the Lebanese guidelines for sludge reuse in agriculture. For the physicochemical analysis, all the samples showed a possibility to be used in agriculture due to the high content of minerals and organic matter. Considering the metal content of sludge, Iaat and Ablah sludge were classified as Class A according to the Lebanese guidelines; however, sludge from Joub Janine was classified as B due to its high content of zinc that exceeded the limit of 700 ppm. Helminth eggs and Salmonella were absent in the sludge samples. Pathogenic organisms, mainly E. coli, were detected in Iaat dry sludge, Staphylococcus aureus was present in Joub Jannine sludge and Acinetobacter in Ablah station (> 100 CFU/100 g).ConclusionIt is recommended to submit the sludge which did not meet the required criteria, for further treatments, particularly the composting process to reduce the metal content and pathogenic microorganisms for a safer reuse in agriculture.

Characterization of primary and secondary wastewater treatment sludge from a pulp and board mill complex to evaluate the feasibility of utilization as a soil amendment agent and a fertilizer product

In this study, we have determined the main important physical and chemical properties as well as the heavy metal concentrations of the primary and secondary wastewater treatment sludge from a pulp and board mill complex located in Finland in order to evaluate the utilization of these by-products as a soil amendment agent or a fertilizer product. Easily soluble Ca, Mg, K, Na, P and S concentrations in the sludges were extracted by ammonium acetate (CH 3 COONH 4 ) and easily soluble Cu, Mn and Zn concentrations by CH 3 COONH 4 + Na 2 EDTA. For the determination of total nutrient and total heavy metal concentrations in sludges, they were digested using aqua regia (3 mL HCl + 9 mL HNO 3 ). The total heavy concentrations in the primary sludge were lower than the Finnish heavy metal limit values for fertilizer products. In the secondary sludge, all other total heavy metals than the total Cd concentration (4.8 mg/kg; d.w.) were lower than the heavy metal limit values for fertilizer products. Due to the low total heavy metal concentrations, which were lower than the Finnish limit values for fertilizer products, the primary sludge is a potential fertilizer. Although the total Cd concentration (4.8 mg/kg; d.w.) in the secondary sludge exceed the limit value of 1.5 mg/kg (d.w.) for fertilizer products, this residue may be used as a soil improver, a growing media or as a fertilizer product in landfill sites or in other closed industrial areas, because the Finnish limit values for fertilizer products are not applied at these sites.

Quantification of Element Fluxes in Wastewaters: A Nationwide Survey in Switzerland.

The number and quantities of trace elements used in industry, (high-tech) consumer products, and medicine are rapidly increasing, but the resulting emissions and waste streams are largely unknown. We assessed the concentrations of 69 elements in digested sewage sludge and effluent samples from 64 municipal wastewater treatment plants as well as in major rivers in Switzerland. This data set, representative of an entire industrialized country, presents a reference point for current element concentrations, average per-capita fluxes, loads discharged to surface waters, and economic waste-stream values. The spatial distribution of many individual elements could be attributed either to predominant geogenic or to anthropogenic inputs. Per-capita element fluxes ranged from <10 μg day-1 (e.g., Au, In, and Lu) to >1 mg day-1 (e.g., Zn, Sc, Y, Nb, and Gd) and >1 g day-1 (e.g., for P, Fe, and S). Effluent loads of some elements contributed significantly to riverine budgets (e.g., 24% for Zn, 50% for P, and 83% for Gd), indicating large anthropogenic inputs via the wastewater stream. At various locations, precious metal concentrations in sludge were similar to those in profitable mining ores, with total flux values of up to 6.8 USD per capita per year or 15 USD per metric ton of dry sludge.

Heavy metals in the industrial sludge and their ecological risk: A case study for a developing country

Heavy metals in the industrial sludges were investigated to assess ecological risk using inductively coupled plasma mass spectrometer (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd, and Pb in the samples were 1.4–9469.7, 4.8–993.8, 12.8–444.4, 2.2–223.8, 1.9–46.0 and 1.3–87.0mg/kg, respectively. Statistically significant difference (P<0.05) was observed for metal concentration in sludge of the studied industries. As a whole, the average concentrations of heavy metals were in the decreasing order of Cr>Ni>Cu>As>Pb>Cd. The results of the Community Bureau of Reference (BCR) sequential extraction showed that the studied metals were predominantly associated with the residual fraction followed by the oxidizable fraction. The values of pollution load index (PLI) were higher than one (>1), indicating progressive deterioration of sludge due to metal contamination. The contamination factor (Cfi) of Cd ranged from 11.2 to 28.9 revealed that the examined sludges were strongly impacted by Cd. The Cfi value demonstrated that sludges from tannery, dye, metal processing and battery manufacturing industries were moderately to very high contamination by Cr, Ni, Cu and As. In view of the potential ecological risk (PER), sludges from all industries showed very high ecological risk.

Metal concentrations in lime stabilised, thermally dried and anaerobically digested sewage sludges

Cognisant of the negative debate and public sentiment about the land application of treated sewage sludges (‘biosolids’), it is important to characterise such wastes beyond current regulated parameters. Concerns may be warranted, as many priority metal pollutants may be present in biosolids. This study represents the first time that extensive use was made of a handheld X-ray fluorescence (XRF) analyser to characterise metals in sludges, having undergone treatment by thermal drying, lime stabilisation, or anaerobic digestion, in 16 wastewater treatment plants (WWTPs) in Ireland. The concentrations of metals, expressed as mgkg−1 dry solids (DS), which are currently regulated in the European Union, ranged from 11 (cadmium, anaerobically digested (AD) biosolids) to 1273mgkg−1 (zinc, AD biosolids), and with the exception of lead in one WWTP (which had a concentration of 3696mgkg−1), all metals were within EU regulatory limits. Two potentially hazardous metals, antimony (Sb) and tin (Sn), for which no legislation currently exists, were much higher than their baseline concentrations in soils (17–20mgSbkg−1 and 23–55mgSnkg−1), meaning that potentially large amounts of these elements may be applied to the soil without regulation. This study recommends that the regulations governing the values for metal concentrations in sludges for reuse in agriculture are extended to include Sb and Sn.

Heavy metal speciation and acid treatment of activated sludge developed in a membrane bioreactor

The aim of this study was to identify the heavy metals forms (exchangeable and bound to carbonate, Fe/Mn oxides, bound to organic matter and sulphide, and residual) associated with different fractions of excess sludge produced by a membrane bioreactor (MBR). Furthermore, the release of metals from the sludge to the liquid was investigated by applying acid treatment using 10% (v/v) H2SO4 (T=25°C, solid-liquid ratio 1:5 w/v) for contact time ranging from 15 min to 4 h. Metal partitioning in sludge, as determined by the sequential chemical extraction showed that the dominant form of both Ni and Zn was bound to the exchangeable and carbonate fraction; the latter were very unstable and sensitive to environmental conditions. The dominant Cu fraction was bound to organic matter and sulphide, while Pb was found to be mainly in the residual fraction which is very stable. Metal speciation after acidification with H2SO4 indicates changes of metal content in sludge and an increase of the exchangeable and bound to carbonate fraction for all metals except Cu. Acidification resulted in removal of 82% for Ni, 78% for Zn, 47% for Cu and 45% for Pb.

Some Properties and Detection Methods of Paper Sludge

Some properties of paper sludge were analyzed, including water content, organic material content, pH value, fiber content, ash content ,C, H, S, N content and metal content of sludge in three sedimentation tanks.Besides,COD,SS, sludge concentration were analyzed and optical microscope photoes of sludge were got.The results showed that water content was high, organic material content was high, pH value of three sludges was alkalescent, metal elements were varied, lots of bacteria in wet sludge. From the first tank to the third one,COD and SS are gradually diminishing The research of sludge’s properties may be helpful to sludge treatment.

Leaching characteristics of heavy metals from sewage sludge by Acidithiobacillus thiooxidans MET.

An acidophilic, sulfur-oxidizing Acidithiobacillus thiooxidans MET bacterium was isolated from anaerobically digested, dewatered sewage sludge. This bacterium showed sulfur-oxidizing ability at both acidic and neutral conditions, and allowed metal leaching even at a high (130 g L(-1)) sludge solids concentration. We found that low metal leaching efficiency at high solids concentration was mainly due to an increase in buffering capacity resulting in retardation of pH reduction. Therefore, metal leaching was mainly influenced not by sludge solids concentration, but by the pH (or sulfate concentration per unit sludge mass) of the sludge solutions. The relationship between the pH of the sludge solution and the efficiency of metal leaching was obtained by quantitatively investigating the effect of pH reduction or the amount of sulfate produced per unit sludge mass on leaching of each metal. Furthermore, the relationship between total metal content in the sludge and metal leached to the solution was obtained for each metal. Such a relationship allowed estimation of leachable metal at various amounts of total metal content in sludge.

Leaching Characteristics of Heavy Metals from Sewage Sludge by MET

An acidophilic, sulfur-oxidizing Acidithiobacillus thiooxidans MET bacterium was isolated from anaerobically digested, dewatered sewage sludge. This bacterium showed sulfur-oxidizing ability at both acidic and neutral conditions, and allowed metal leaching even at a high (130 g L−1) sludge solids concentration. We found that low metal leaching efficiency at high solids concentration was mainly due to an increase in buffering capacity resulting in retardation of pH reduction. Therefore, metal leaching was mainly influenced not by sludge solids concentration, but by the pH (or sulfate concentration per unit sludge mass) of the sludge solutions. The relationship between the pH of the sludge solution and the efficiency of metal leaching was obtained by quantitatively investigating the effect of pH reduction or the amount of sulfate produced per unit sludge mass on leaching of each metal. Furthermore, the relationship between total metal content in the sludge and metal leached to the solution was obtained for each metal. Such a relationship allowed estimation of leachable metal at various amounts of total metal content in sludge.

Potential Impact of Draft Proposals to Revise the EC Directive Controlling Sewage‐Sludge Applications to Land

AbstractThe EC Directive which controls the application of sewage sludge to agricultural land, in particular, the reduction in permitted concentrations of heavy metals in sludge and sludge‐amended soils, is being reviewed by the European Commission. The implications for sludge recycling in Scotland are examined, and it is estimated that the available land bank would be reduced to about 50% of its present area. In addition, the land area which is required would have to significantly increase because of the proposed lower application rates. These scenarios cast doubt on the long‐term viability of the sludge‐recycling option in Scotland.

Heavy metal removal from wastewater and leachate co-treatment sludge by sulfur oxidizing bacteria

Heavy metal concentration in sludge is one of the major obstacles for the application of sludge on land. There are various methods for the removal of heavy metals in sludge. Using sulfur oxidizing bacteria for microbiological removal of heavy metals from sludges is an outstanding option because of high metal solubilization rates and the low cost. In this study, bioleaching by indigenous sulfur oxidizing bacteria was applied to sludges generated from the co-treatment of municipal wastewater and leachate for the removal of selected heavy metals. Sulfur oxidizing bacteria were acclimated to activated sludge. The effect of the high organic content of leachate on the bioleaching process was investigated in four sets of sludges having different concentrations of leachate. Sludges in Sets A, B, C and D were obtained from co-treatment of wastewater and 3%, 5%, 7% and 10% (v/v) leachate respectively. The highest Cr, Ni and Fe solubilization was obtained from Set A. Sulfur oxidizing bacteria were totally inhibited in Set D that received the highest volume of leachate.

Land application of sewage sludge: scientific perspectives of heavy metal loading limits in Europe and the United States

Heavy metals in sewage sludges accumulate in soils after successive sludge applications and can be toxic to plants, soil organisms, as well as humans and animals along the food chain. Because of this potential threat, many countries have set limits to the additions of metals in sludges to agricultural land, based on (i) the concentrations of metals in sludge itself, (ii) the loading, or total amount, of metal that can be added and often how quickly this can be applied, and (iii) the maximum concentrations of metals in soil which are allowed to build up after sludge applications. This review, based on regulations in the United States and some west European countries, shows that at present three basic approaches to setting limits can be distinguished: (i) a comprehensive analysis of the pathways of pollutant transfer to selected target organisms and an assessment of the likely harmful effects that metals may have on the target; (ii) setting limits consistent with the lowest observed adverse effect concentrations, which are actual cases of effects due to metals, but not necessarily derived from studies that involved land application of sewage sludge; and (iii) attempting to match the metal inputs to soil to the small losses of metals due to crop removal, soil erosion, and leaching ("metal balance approach"). These approaches are shown to result in widely different numerical limits being set for the same constituent, which is creating unease among the regulatory authorities worldwide. These differences appear to arise from at least two main sources. The first is whether, by a policy decision, zero impact is desired. This leads to very low limits, and is the philosophy behind the metal balance approach. The second is that those approaches that allow some increase in metal concentrations in soils often adopt different target organisms and these models suffer from the limited supply of relevant toxicity data, particularly information obtained from metals applied in sewage sludge. Differences in the philosophy behind environmental protection and in the choices of which organisms to protect explain the different metal limits for sewage sludge which have been adopted in the countries examined.Key words: zinc, cadmium, copper, chromium, nickel, lead, mercury, soil microbes, ecotoxicology, soil protection.

Sludge quality benefits realized from drinking water stabilization

Concerns about sludge quality continue to increase as emphasis shifts from disposal to use. A frequently asked question is what effect a drinking water stabilization program will have on the metal content of wastewater sludge. Data presented in this paper clearly show that there is a direct correlation between drinking water corrosivity and some metal contents of sludge