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[Display omitted] • The release of Zn and Pb were mitigated by the synergistic effect. • Bioavailable fractions of HMs were reduced by SiO 2 and Al 2 O 3 from the sludge. • Bioavailable phosphorus was increased from 18.79 to 49.69 mg/g by co-pyrolysis. Phosphate tailings (PT) was used to reduce the release of heavy metals (HMs) during pyrolysis and the leachable rate of residual HMs, and simultaneously improve the bioavailability of phosphorus in the sludge-based biochar. The concentration of heavy metals and the fractions determined by BCR method was used to investigate the release and the transformation of Zn, Pb, Mn, Ni and Cu during pyrolysis involved with the effects of temperature and the addition of PT. The respective pyrolysis experiments shows that the release of Zn and Pb increases with temperature for both sewage sludge (SS) and PT, and the bioavailable fractions (F1 + F2) of Mn, Ni, and Cu increases with temperature for PT. During co-pyrolysis, blended samples released lower quantities of Zn and Pb and presented lower bioavailability of HMs than the individual SS or PT. A synergistic effect of co-pyrolysis was evident for volatile Zn and Pb. The decomposition of CaMg (CO 3) 2 from PT produced CaO, by which the volatile ZnCl 2 and PbCl 2 were transformed into ZnO and PbO with less volatility and higher reactivity with SiO 2 and Al 2 O 3 than the chlorides. Then SiO 2 and Al 2 O 3 from SS acted as the final stabilizer to immobilize the oxides. The final product combined with SiO 2 and Al 2 O 3 , such as ZnSiO 4 and ZnAl 2 O 4 , were detected. The addition of PT also introduced more Ca and P into sludge to produce biochar with higher concentration of apatite phosphorus with higher bioavailability. [ABSTRACT FROM AUTHOR]

In recent centuries, micronutrient deficiencies are considered a major challenge for human health. Biofortification of principal crops has been broadly accepted as a sustainable scenario to overcome this limitation. The experiment was carried out in a completely randomized factorial design with three replications during the 2007–2008 and 2008–2009 growing seasons. Four fertilizers and two doses of humic acid were used in the experiment. Analysis of variance indicated that humic acid, fertilizer type, and growing season caused statistically significant differences in macro and micronutrient content and heavy metal concentrations of shoot and seed in plants. Results also denoted that organic material amendment improved macro and micronutrient content of barley plants compared with IF in which SS treatment increased Ca, Mg, Mn, Fe, Zn, and Ni concentrations in shoot/seed while SM treatment enhanced N, P, and K concentration of plants. Moreover, IF-treated plants increased heavy metal accumulation in shoot and seed tissues whereas organic amendments reduced heavy metal uptake such that the lowest Pb and Cd were determined in SM-treated plants, and the lowest Ni content was measured in W-treated samples. HA application promoted Zn, Mg, and Cu accumulation in plants, however, individual or combined with fertilizers reduced other micro and macronutrient uptake. In conclusion, the amendment of 40 tons ha−1 of sheep manure and sewage sludge is an improving and beneficial practice in barley cultivation for the biofortification of crops. However, HA treatment did not form a meaningful whole in the experiment but promoted Zn, Mg, and Cu concentrations in plant tissues. [ABSTRACT FROM AUTHOR]

In this paper, we compared the sorption of copper and zinc on three adsorbents - bentonite, zeolite, and dewatered digested sludge from a wastewater treatment plant. Sorption was carried out at 27℃ and subsequently at a reduced temperature of 10℃ and the results were compared. The reduced temperature positively affected the sorption efficiency and increased the adsorption capacity of the monolayer of each sorbent. Regardless of the temperature, the sorption progression was not linear. In the initial phase, the sorption proceeded rapidly, but after about 90 min the system reached equilibrium and the concentrations of metals in solution did not change significantly. The size of the specific surface area of the sorbents did not directly correlate with the removal efficiency of Cu2+ and Zn2+. Copper sorption by bentonite reached a level of almost 100% at reduced temperature and 80% at room temperature. The efficiency of zinc removal by bentonite was found to be 40% at reduced temperature. The efficiency of copper removal using zeolite was approximately 90% at both laboratory and reduced temperature. For bentonite and zeolite, we confirmed their good sorption properties. The sludge showed low Cu2+ sorption efficiency, but Zn2+ removal efficiency was higher than bentonite and zeolite. In both cases, the reduced temperature had a positive effect on the sorption capacity of the sludge. Sludge as a waste material could be used for heavy metal removal by modifying the sorption conditions or its modifying, which should be further investigated. [ABSTRACT FROM AUTHOR]

Low‐carbon alkaline thermal hydrolysis of sewage sludge for the production of high‐quality plant‐growth‐promoting nutrients and biostimulants is a growing concern for sludge resource utilization in agriculture. Thus, this study aims to investigate functional characteristics and soil biochemical effects of sewage sludge‐derived nutrients and biostimulants (SS‐NB). The content of heavy metals in SS‐NB decreased by 47.39–100%, and an increase in soil protease, invertase, and soil nutrient utilization rates are observed in SS‐NB groups. SS‐NB substituted for chemical fertilizer increased the diversity and evenness of microbial community and reduced the abundance of the soil‐borne bacterial genus Arthrobacter. The dominant community of SS‐NB100 group is mainly enriched in Microvirga, Ensifer, Novosphingobium, Bosea and Ellin6055, which are principally beneficial symbiotic bacteria of plants and participated in C and N cycles. Moreover, SS‐NB reduced the accumulation of Ktedonobacteria and Nitrosospira, which are involved in the production of CO2 and N2O, and also enhanced the coordination of soil microorganisms with enzyme activities and nutrient utilization rate. In conclusion, the results suggest that SS‐NB exerts a positive effect on reducing greenhouse gas emissions and preventing soil‐borne diseases, and can further enhance collaboration with soil enzyme activity and soil nutrient utilization by stimulating soil microorganisms. [ABSTRACT FROM AUTHOR]

The land application of sewage sludge can cause different environmental problems due to the high content of potentially toxic elements (PTEs). The objective of this study was to compare the effect of urban biological sewage sludge (i.e. the waste of activated sludge process) and its derived biochar as the soil amendments on the bioavailability of PTEs and their bioaccumulation by corn (Zea mays L.) under two months of greenhouse conditions. The soil was treated by adding biochar samples at 0 (control), 1, 3, 5% w/w. The diethylenetriamine pentaacetic acid (DTPA)-extractable concentrations of PTEs including Zn, Pb, Cd, Cr, Ni, Fe, and Cu in soil and their accumulation by plant shoot and root were measured. Conversion of the biological sewage sludge into the biochar led to decrease the PTEs bioavailability and consequently decreased their contents in plant tissues. The DTPA extractable metal concentrations of produced biochar in comparison to the biological sewage sludge reduced 75% (Cd), 65% (Cr), 79% (Ni and Pb), 76% (Zn), 91% (Cu) and 88% (Fe). Therefore, the content of Ni, Fe, Zn and Cd in corn shoot was decreased 61, 32, 18 and 17% respectively in application of 5% biochar than of raw sewage sludge. Furthermore, the application of 5% biochar enhanced the physiological parameters of the plants including shoot dry weight (twice) and wet weight (2.25 times), stem diameter (1.70 times), chlorophyll content (1.03 times) in comparison to using 5% raw sewage sludge. The results of the study highlight that application of the biochar derived from urban biological sewage sludge in soil could decrease the risk of PTEs to the plant. [ABSTRACT FROM AUTHOR]

This article is devoted to the search for effective ways of neutralizing sewage sludge to obtain sludge-based reclamation material. It was necessary to solve the problems of deodorizing the sludge and fixing the mobile forms of heavy metals in its composition. The composition, effective for solving the assigned problems, was experimentally determined; it included quicklime, sodium hypochlorite and peat. In the presence of sodium hypochlorite in the sludge-based composition, oxidation processes occur with the chemical transformation of ammonia and hydrogen sulfide into non-toxic and odorless compounds. Lime combined with peat promotes the humification of sewage sludge and the binding of heavy metals. Based on the composition that showed the best results, a technology has been developed for the chemical treatment of sewage sludge in situ to produce reclamation material. [ABSTRACT FROM AUTHOR]

• Microbial inoculants, (Rhizobium and two strains of AMF), were evaluated for their effectiveness in mitigating metal toxicity and reducing metal uptake in lentil plants. • Sewage sludge-amended soil adversely impacted lentil growth, leading to increased accumulation of heavy metals. • Microbial inoculants enhanced lentil growth and productivity, particularly under heavy metal stress. • Co application of microbial inoculants synergistically reduced heavy metal uptake in roots and shoots of lentil with more efficiency. • The findings suggest microbial inoculants could have practical applications for sustainable agriculture and efficient crop production. Reusing sewage sludge as a mode of nutrients and an organic amendment may be a viable choice for the appropriate treatment of organic waste. This study examined the impact of symbiotic microbes such as Rhizobium and two selected arbuscular mycorrhizal fungi (AMF), Funneliformis caledonius (Nicolson & Gerd.) and Glomus bagyarajii (Mehrotra), on the growth, photosynthetic pigments, biochemical content, microbial population, and heavy metal uptake in lentil plants grown in soil mixed with 20 % sewage sludge. Lentil seeds were inoculated with Rhizobium prior to sowing and with either of the AMF (Funneliformis caledonius or Glomus bagyarajii) in pots filled with soil-sewage sludge mixture. The results showed that the tested microbial inoculum enhanced the growth and productivity of lentil plants. Lentil plants inoculated with Rhizobium and AMF had better nodulation and root colonization, leading to an increase in the nitrogen, phosphorus and potassium (NPK) content and a decrease in the stress marker, proline, in plant parts. In addition, the inoculated microbes also improved the photosynthetic and biochemical contents of the plant. Lentil plants grown in sewage sludge-amended soil when inoculated with Rhizobium and either of AMF were found to be more effective in accumulating Cd, Cr, Pb, Ni, and Zn in the roots, while restricting their translocation to the above-ground parts of the plant, thereby improving plant health. Overall, the study outcomes provide evidence that Rhizobium and AMF have the potential to tolerate heavy metal stress caused by the addition of sewage sludge to soil, which has important implications for sustainable agriculture practices. The study also highlights the importance of microbial inoculants, such as Rhizobium and AMF in enhancing growth and yield, particularly under heavy metal stress in economically important lentil. [ABSTRACT FROM AUTHOR]

Phosphorus (P), as a crucial resource, has attracted more attention for its recycling. Products from hydrothermal reaction of sewage sludge (SS), represent promising sources for efficient P recovery. This work systematically summarizes reaction mechanisms of SS hydrothermal reactions and corresponding distribution, migration, and morphological transformation pathways of P during reactions. The formation of hydrochar is mainly attributed to the polymerization, aromatization, and condensation of remarkably reactive intermediates generated through the degradation of biopolymers in SS, as well as the solid-solid conversion of part of lignin and the precipitation of insoluble humic substances. P in SS is mostly concentrated in solid-phase products (hydrochar) after hydrothermal reaction. Orthophosphate is the dominant P species in hydrochar. The distribution and migration transformation pathways of P are notably influenced by reaction conditions (i.e., reaction temperature, reaction time, initial pH and additives). The reaction time had a small effect on P conversion. Wet chemical extraction is widely used to extract P from hydrochar. The P extraction efficiency of acid extraction is higher than that of alkaline extraction. However, the precipitation of heavy metals in hydrochar limits industrial application of acid leaching. Ultimately, some prospects for the optimization of the P recovery process are put forward. [Display omitted] [ABSTRACT FROM AUTHOR]

Heavy metal cadmium (Cd) naturally occurs in soil and is a hazardous trace contaminant for humans, animals, and plants. The main sources of Cd pollution in soil include overuse of phosphatic fertilizers, manure, sewage sludge, and aerial deposition. That's why an experiment was conducted to analyze the effect of Cd toxicity in Capsicum annuum L. by selecting its seven varieties: Hybrid, Desi, Sathra, G-916, BR-763, BG-912, and F1-9226. Cadmium was spiked in soil with four levels, i.e., (0, 3, 4, and 5 mg Cd kg− 1 of soil) for a week for homogeneous dispersion of heavy metal. Chili seeds were sown in compost-filled loamy soil, and 25-day-old seedlings were transplanted into Cd-spiked soil. Cadmium increasing concentration in soil decreased chili growth characteristics, total soluble sugars, total proteins, and amino acids. On the other hand, the activities of antioxidant enzymes were increased with the increasing concentration of Cd in almost all the varieties. Treatment 5 mg Cd/kg application caused − 197.39%, -138.78%, -60.77%, -17.84%, -16.34%, -11.82% and − 10.37% decrease of carotenoids level in chili V2 (Desi) followed by V4 (G-916), V1 (Hy7brid), V7 (F1-9226), V6 (BG-912), V5 (BR-763) and V3 (Sathra) as compared to their controls. The maximum flavonoids among varieties were in V5 (BR-763), followed by V6 (BG-912), V7 (F1-9226), V3 (Sathra) and V1 (Hybrid). Flavonoids content was decreased with − 37.63% (Sathra), -34.78% (Hybrid), -33.85% (G-916), -31.96% (F1-9226), -31.44% (Desi), -30.58% (BR-763), -22.88% (BG-912) as compared to their control at 5 mg Cd/kg soil stress. The maximum decrease in POD, SOD, and CAT was − 31.81%, -25.98%, -16.39% in chili variety V7 (F1-9226) at 5 mg Cd/kg stress compared to its control. At the same time, maximum APX content decrease was − 82.91%, followed by -80.16%, -65.19%, -40.31%, -30.14%, -10.34% and − 6.45% in V4 (G-916), V2 (Desi), V3 (Sathra), V6 (BG-912), V1 (Hybrid), V7 (F1-9226) and V5 (BR-763) at 5 mg Cd/kg treatment as compared to control chili plants. The highest CAT was found in 5 chili varieties except Desi and G-916. Desi and G-916 varieties. V5 (BR-763) and V6 (BG-912) were susceptible, while V1 (Hybrid), V3 (Sathra), and V7 (F1-9226) were with intermediate growth attributes against Cd stress. Our results suggest that Desi and G-916 chili varieties are Cd tolerant and can be grown on a large scale to mitigate Cd stress naturally. [ABSTRACT FROM AUTHOR]

Jordan has recently observed a gradual shift in vegetable production from open-fields to greenhouses with mounting consumer concerns about food quality and safety. We investigated heavy metals in soil collected from greenhouse vegetable production area in northern Jordan. Sixty-one surface soil samples were collected, of which forty-seven from plastic-covered greenhouses and fourteen were sampled from the adjacent open-field land, with both designated for vegetable production. The average concentrations of Cr, Cu, Cd, Pb, Ni, Zn were 26.1, 26.8, 0.81, 53.0, 49.3, 139.1 mg/kg, and 19.1, 19.3, 0.66, 49.7, 46.7, 104.9 mg/kg for greenhouse and open-field soils, respectively. While the accumulation of heavy metals was consistently higher in greenhouse than in open-fields, both soils revealed a similar metal ranking with a few exceptions. Greenhouse soils revealed relatively lower pH values with higher variabilities. In greenhouse cultivated soils, CaCO3 content averaged 21.4% compared to 23% measured in open-field soils. Soil salinity showed greater values for greenhouse samples (averaging 1118.6 µs/cm) than those observed in open-field agricultural soils (a mean of 503.6 µs/cm). The soil organic matter (TOM) exhibited values in the range of 1.06-3.35% relative to 0.59-2.41% found in open-field area. The spatial distribution of heavy metal concentrations for greenhouse soils revealed higher levels in the northern soils, whereas the least was found in the southern sampling points. The Enrichment results showed 23.4% of sampling sites were moderately contaminated with Pb, and 38.3% were moderately contaminated with Cd, of which 8.5% indicating moderately severe contamination. The Igeo results indicate 25.5% of greenhouse soils were moderately contaminated with Pb and 38.3% were heavily polluted with Cd. The contamination factors showed 25.5% and 38.3% of greenhouse sampling soils were considerably contaminated with Pb and Cd, respectively. 2% indicate very high contamination for Cd and 2% showed considerable contamination for Zn. PLI indicates that only two sampling sites are polluted. The ecological risk assessment showed low Ei values for all heavy metals suggesting slight risks, except for Cd which indicate strong risk. Total potential ecological risks values showed low risk to the local environment. Cd accounts for most of the total risks (72.27-82.67%) followed by Pb (11.49-14.87%). Some greenhouse soils were non-compliant with soil quality standards especially for Ni, Cd, and Pb. The observed levels of heavy metals are attributable to agricultural activities including long-term application of pesticides, phosphatic and nitrogen fertilizers, sewage sludge, wastewater irrigation and chicken manure in addition to industrial dust and traffic related emissions. [ABSTRACT FROM AUTHOR]

By evaluating sewage sludge analysis data from a large German sewage treatment plant (>1 million population equivalents), seasonal fluctuations in the composition of the sewage sludge could be identified. These fluctuations include a periodic decrease in carbon content and an increase in ash content in the middle of the year. Various wastewater and sludge treatment processes as well as climatic influences could be identified as causes for this trend. The investigation of the contents of various heavy metals and trace elements in the sewage sludge also showed partly strong fluctuations in the course of the year, which can have an influence on the utilization possibilities of the sewage sludge. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the effects of anaerobically stabilized sewage sludge (SS) converted into 90% dryness granules at different doses of control, 3% SS, 6% SS, and 9% SS on elemental composition of Festuca arundinacea Schreb. and physicochemical properties of soil. Color measurements were made with the CIE L* a* b* method unit; the highest color (4.10) and the highest coating score (5.7) were calculated for the 6% SS treatment. The highest biomass (9.11 g) was obtained from the 3% SS and the lowest (7.67 g) from the 9% SS dose. Plant height measurements were listed as follows: 3% SS (9.5 cm) > 6% SS (8.8 cm) > control (8.7 cm) > 9% SS (8.1 cm). Average bioaccumulation factor for the present heavy metals were ordered as: Cd (0.542) > Hg (0.452) > Cr (0.448) > Ni (0.246) > Pb (0.076). The lowest geoaccumulation index (Igeo) was obtained in Cr (-1.35) and the highest value in Cd (1.69). Available P, K, Ca, Mg were analyzed with ammonium acetate extraction method, and Fe, Zn, Cu, and Mn in the soil extracted with DTPA were determined. In the soil samples, total N (0.180%) and available elements (mg kg-1) P (101.393), Ca (6502.570), Mg (609.433), Na (259.44), Fe (13.61), Cu (4.05), Zn (17.76), and B (1.00) were determined at high values in the 9% SS application. Heavy metals (mg kg-1) were extracted with aqua regia. Nickel (48.87), Pb (26.83), Cd (0.97), and Hg (153.12 µg kg-1) were determined at high values in the 9% SS application. Plant nutrients in the plant samples were extracted from acid digestion, and N (3.93%), P (0.51%), Mg (0.59%), Ca (1.77%), Zn (127 mg kg-1), and B (15 mg kg-1) were determined at high values in the 9% SS application. Heavy metals' (Ni, Cd, Cr, Pb, and Hg) content toxic effects were not observed in the plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Fe2+ pyrite /PMS conditioning method was developed with extremely low acid usage. • Fe2+ pyrite /PMS conditioning improved WAS dewaterability and released 22.75% of BWC. • Some PN in TB-EPS was decomposed into inorganic-N by Fe2+ pyrite /PMS conditioning. • The eco-toxicity of Cr in WAS was weakened by Fe2+ pyrite /PMS conditioning. • 94% pyrite was recovered after use and the recycled feasibility was verified. Wastewater activated sludge (WAS) has poor dewaterability and contains heavy metals (HMs), limiting its land application. Therefore, in this study, a novel pyrite acid eluent-activated peroxymonosulfate (Fe2+ pyrite /PMS) conditioning approach that can completely recover the residual pyrite and greatly reduce acid use was developed to improve WAS dewaterability, and the HMs chemical speciation and risks of conditioned WAS were assessed. Our results showed that under the optimized operational parameters, the capillary suction time (CST) and water content (Wc) of WAS decreased by 46.03% and 7.75%, respectively. Furthermore, during Fe2+ pyrite /PMS conditioning processing, sulfate radical (SO 4 − ) destroyed the extracellular polymeric substances (EPS) matrix, causing bound water release and the decrease of proteins/polysaccharides in outer layered EPS, even the decomposition of some protein-N in tightly bound EPS (TB-EPS) into inorganic-N. In addition, although the total concentration of HMs in the conditioned WAS matrix increased, the Ni concentration decreased in the solid fraction. Further, the risk assessment code (RAC) levels did not increase, and the eco-toxicity of Cr became weakened after Fe2+ pyrite /PMS conditioning. However, after acid extraction, the pyrite residue had worsened recycle performance because the passivation layer contained S0/S n 2− on its surface, and no additional elements were detected in the pyrite residue, which had almost no effect on its further usage. [ABSTRACT FROM AUTHOR]

In phytostabilization, heavy metal-tolerant plants (e.g.,grasses) can be used to reduce the mobility of heavy metals in soils. The most important step in phytostabilization is the selection of the suitable plant species, in which growth and development can be supported by soil amendments. Sewage sludge compost could be a suitable additive, which provides nutrients for the plant species used for phytostabilization and contributes to an alternative solution for sewage sludge utilization. The aim of the study was to examine the potential of sewage sludge compost in phytostabilization for heavy metal contaminated matrices: identify the optimal ratio of sewage sludge compost to decrease phytotoxicity of the matrices, and assessment of feasible plant species for phytostabilization based on its bioaccumulation properties. In this research, perennial ryegrass (Lolium perenne), broad-leaved sorrel sorrel (Rumex acetosa), lettuce (Lactuca sativa) and cabbage (Brassica oleracea var. capitata) were used for phytotoxicity experiments as well as for testing sewage sludge compost amended phytostabilization of polluted flotation sludge and mine tailings. Sewage sludge compost increased the pH and electric conductivity of the matrices. High salt content and low acidity, altogether with heavy metals caused harmful physiological effects on plant species grown without any compost addition. In the root development test, as in the germination test, the application of 5% sewage sludge compost proved to be optimal. The lower translocation factors of broad-leaved sorrel and perennial ryegrass showed a higher rate of heavy metal accumulation in the roots. Perennial ryegrass, cabbage, and lettuce plant species reached their maximum biomass by adding 5% of sewage sludge compost. Based on the bioaccumulation, translocation and biomass properties, application of perennial ryegrass is recommended for phytostabilization of heavy metal contaminated sites. Furthermore, composted sewage sludge also had a significant effect on the reduction of heavy metal uptake by cabbage and lettuce, which highlights their role as indicator plants in ecotoxicological measurements. The effects of sewage sludge compost added to the heavy metals contaminated flotation sludge and mine tailings (pH = 4.8) were examined. The applicability of broad-leaved sorrel and perennial ryegrass that can be found under natural conditions in the study area was assessed as a function of sewage sludge compost ratio for phytostabilization purposes. Moreover, ecotoxicological tests had been performed with cabbage and lettuce on sewage sludge compost + flotation sludge and mine tailings mixtures. Based on the results, it was proved that the phytostabilization is feasible with the investigated plant species by adding 5% of sewage sludge compost to the flotation sludge and mine tailings. [ABSTRACT FROM AUTHOR]

A widespread method of sewage sludge disposal is still simple storage in sludge lagoons. Subsequent thermal utilization is hardly possible because sludge properties change over time and energy content is reduced. Use as a soil conditioner in agriculture or landscaping is usually not possible due to high heavy metal contents. This paper describes a method in which a 10-year-old accumulated sewage sludge can be utilized as technical soil by mixing it with pyrolized fresh sewage sludge. For this purpose, physicochemical and toxicological characteristics of sewage sludge of different storage periods were identified, processes of thermal destruction of sewage sludge analyzed, toxicological characteristics of solid products of thermal sludge treatment determined, and the possibility of using the sewage sludge–pyrolysate mixture as technical soil was assessed. Results show that the gross calorific value of fresh and one-year stored sewage sludge is with approx. 15,000 kJ/kg dry basis sufficient to produce pyrolysate autothermally. It is also shown that when the pyrolysis residue is mixed with fresh or 1-year old sewage sludge, heavy metals can be immobilized and thus the leaching of heavy metals significantly reduced by up to 75%. The method described can thus be a possible option for recycling accumulated sewage sludge. [ABSTRACT FROM AUTHOR]

Cadmium is one of the most dreadful heavy metals and is becoming a major toxicant in ground water with increasing concentration above the WHO Guidelines in drinking water (0.003 mg/L). The potential sources of cadmium include sewage sludge, phosphate fertilizers and ingredients like Ni–Cd batteries, pigments, plating and plastics. Cadmium levels are increased in water owing to the use and disposal of cadmium containing ingredients. Water draining from a landfill may contain higher cadmium levels. The authors have tried to evaluate the optimized nutritional conditions for the optimal growth and Cd(II) remediation capacity for a developed Cd(II) resistant yeast strain named Candida tropicalis XTA 1874 isolated from contaminated water-body in West Bengal. By analyzing the optimization conditions, a synthetic medium was developed and the composition has been given in the main text. The strain showed much better Cd(II) adsorption capacity under the optimized nutritional conditions (Mean removal = 88.077 ± 0.097%). [ABSTRACT FROM AUTHOR]

Phosphorus (P) is abundant in wastewater sludge and can be a secondary P source that will contribute to a circular economy. Electrochemical systems are an emerging technology that can be used to release and recover P from wastewater sludge. This paper introduces and analyzes the state-of-the-art electrochemical methods for P release and recovery from wastewater sludge, both qualitatively and quantitatively. Electrochemical P release, which involves mobilizing P from the solid phase into the aqueous phase, is categorized into three major mechanisms, electro-biological release, anodic P release, and cathodic P release. Anodic P release has been most widely studied with a median P release rate of 92.4 mg d−1. Correlation analysis revealed that the type of feed sludge, sludge P contents, sludge loading rate, and current density have a significant impact on the P release performance. The released P is subsequently separated from the heavy metal laden sludge and then recovered via different electrochemical systems such as three-chamber cells, two-chamber cells, and their variations. Those systems can achieve P recovery efficiency of 50 ∼ 80% and a recovery rate of 2.0 × 102∼1.8 × 103 mg P d−1. Energy consumption of electrochemical P recovery is estimated at 50 ∼ 200 kWh kg−1 P but only 27.3% of literature reported such data. This work provides insights into the development and challenges of electrochemical P release & recovery from wastewater sludge and discusses the challenges that need to be addressed to advance the viability of electrochemical P recovery approach. [ABSTRACT FROM AUTHOR]

Soil pollution by heavy metals (HM) has become a problem in Algeria, in particular that caused by the discharge of untreated sewage sludge due to the lack of means at the level of sewage treatment plants (WWTP). The objective of our work was to study the possibility of reducing HM pollution of the soil of the WWTP site of Reghaia (Algeria) by phytoremediation. The results obtained showed the decrease in plant growth parameters (maize, rapeseed and alfalfa) grown on the polluted soil. However, on polluted soil amended with fertilizer, improved growth of these plants was noted. It has also been observed that the cultivation of plants in polluted soils (amended and unamended) made it possible to have attenuation rates for HMs (Cd, Zn and Cr) higher than those obtained in the absence of plant cultivation. However, these rates were not very high (less than 40%), and the fertilizer amendment did not increase these rates, despite the improvement in the production of plant biomass. This would be mainly due to the decrease in the bioavailability of HMs for plants. It was concluded that the tested plants do not allow the phytoextraction of HM but their phytostabilization in the polluted soil of the Reghaia WWTP site. In Algeria, studies on the treatment of polluted soils by phytoremediation are few. The novelty of our study is due to the fact that the polluted soil of the site of the Reghaia wastewater treatment plant (Algeria) has not been the subject of another study. In addition, the results obtained from studies carried out on polluted soil following human activities such as the discharge of sewage sludge cannot be extrapolated to our polluted soil because the conditions which affect the performance of phytoremediation are not the same (type of soil, age of pollution, type and content of heavy metals, temperature, pH, content of organic matter... etc.). [ABSTRACT FROM AUTHOR]

Soil pollution caused by heavy metals has emerged as one of the most significant environmental problems in the world. In soils, specific plant species are able to grow, adapt and absorb heavy metals. Phytoremediation is an emerging technology in which higher plants are used to reclaim the contaminated environment. In this study, the possibilities of removing the pollution caused by Zn, which is applied to the loamy soil together with and without sewage sludge at increasing levels (0, 75, 150, 300, 600 and 1200 μg g-1), has been researched with certain hyperaccumulator plants such as Brassica juncea, Raphanus sativus and Silene vulgaris grown in Bafra ecological conditions. In order to clean Zn added to the soil at increasing levels with or without sewage sludge by using phytoremediation technology, Silene vulgaris was found to remove the highest amount of Zn in the soil by producing the greatest amount of biomass in the ecological conditions of the region compared to Brassica juncea and Raphanus sativus, and other hyperaccumulator plants grown in the plots. Significant differences were determined in the development of plants and Zn removal between the sludge treated and untreated plots. Water-soluble Zn, which was found at high levels in the cultivation of plants at 600 and 1200 μg g-1 Zn application doses in the sewage sludge treated plots, was determined at lower levels at the end of the harvest of the plants. In the application of increasing levels of Zn with sewage sludge, the lowest organic bound Zn was determined in the plots where Silene vulgaris was grown. The highest exchangeable Zn concentration was determined in soil samples taken after the harvest of the Raphanus sativus plant among the hyperaccumulator plants grown at all Zn application doses in the trials with and without sewage sludge application. [ABSTRACT FROM AUTHOR]

Unsystematic use of city waste, sludge and sewage water in agricultural fields elevated the heavy metal load in soil warranting critical introspection. The present study aims to delineate heavy metals in polluted soils of peri-urban Kolkata, determine pollution and ecological risk, assess the heavy metal uptake and human dietary risk in commonly cultivated crops. Total 36 sampling points were selected and paired sampling of soil and crops were done. Significant available heavy metal (mg kg-1) in surface soil like Cd (0.72-3.76), Pb (28.59-87.29), Ni (3.11-8.73), and Cr (2.23-8.43) and in crops as Cd (0.55-2.73), Pb (2.82-29.85), Ni (2.45-8.27) and Cr (0.80-6.85) was observed. Use of machine learning revealed soil pH and organic carbon as the influencing factors of heavy metal contamination. Moderate to considerable environmental and ecological risk was observed. Substantial carcinogenic risk was observed as Cd (1.13x10-3 to 3.77x10-4), Pb (2.75x10-4 to 3.47x10-5), Ni (1.15x10-3 to 1.73x10-4), and Cr (2.78x10-4 to 1.18x10-4), for almost all crops, with a general trend of spinach > cabbage > radish > red amaranthus > bottle gourd > maize. The results can serve as the baseline information to enforce policy decisions for solving this conundrum of managing waste and saving human lives. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) in sewage sludge (SS) are major obstacles that limit the land application of SS. Although the removal of HMs with acid leaching and cation exchange resins (CER) adsorption has been investigated, neither process alone could meet the simultaneous demand for efficient HMs removal and good preservation of nutrients. In this report, sulfuric acid (H2SO4) and acetic acid (AC) were used to dissolve HMs from the SS, and subsequent CER adsorption was conducted to selectively extract the HMs from acid leachate. With the addition of 5 mmol/L H2SO4, the maximum leaching efficiency of Ni, Cu, Zn and Fe were 64.0%±2.7%, 29.0%±3.7%, 98.4%±4.1% and 16.4%±0.3%, respectively. No significant inhibition effect of Fe in the leachate on the HMs adsorption with CER has been observed. The CER with sulfonate groups (R-SO3H) showed higher Ni, Cu and Zn adsorption efficiency than the CER with thioureido groups (R-SH) and carboxylic groups (R-COOH) in the acid leachate. The optimal operation condition with a combined usage of H2SO4 and R-SO3H is characterized by the advantages of high HM removal efficiency, affordable cost, and low energy consumption through the evaluation with the triangulation model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phosphorus (P) recovery was investigated in a multi-stage process. • Hydrothermal carbonization (HTC) and thermochemical treatment were considered. • A pretreatment with an HTC can improve thermochemical process. • MgCl 2 as additive can increase P retention rate and reduce heavy metal content. Phosphorus (P) is a non-regenerative and finite raw material. Due to its decreasing availability, and to protect the environment, recycling methods are needed. With the focus on closing nutrient cycles, sewage sludge (SS) is a potential source for P recovery. The objective of this study was to produce a mineral P-reach fertilizer. For this purpose, the treatment of SS in a multi-stage process, consisting of a hydrothermal carbonization (HTC) and thermochemical post-treatment was examined and compared with a direct thermochemical treatment. The focus was on the transformation of P and the migration of the heavy metals during the processes. In addition, the role of MgCl 2 as an additive was examined. During the HTC, most of the P remained in the HTC-char, so that the P content increased in the HTC-char compared with the SS. The addition of MgCl 2 to the process resulted in lower transportation rates of P in the liquid phase and higher P solubilities in water, citric acid, and alkalic ammonium citrate out of the solid phase. The thermochemical treatment of SS and the HTC-chars further concentrated P in the ash. Retention rates of >97% were achieved, and P 2 O 5 contents in the ash were as high as ∼16 wt-%. The presence of the additive resulted in (i) higher retention rates of P in the ashes (ii) higher P-solubility and (iii) higher removal rates of easily volatile heavy metals such as Pb and Zn, and the treatment of HTC-char favored these effects compared with the direct treatment of SS. [ABSTRACT FROM AUTHOR]

Huge amounts of unwanted sewage sludge are generated in the process of wastewater treatment, calling for methods to recycle sewage sludges into value-added materials and fuels. Here, we review the use of sewage sludge to produce glass and porous ceramics, with focus on sewage sludge production, properties, dewatering mechanism and solidification. We present the process parameters that control the formation of sewage sludge porous ceramics. The effect of heavy metals on solidification is discussed. [ABSTRACT FROM AUTHOR]

The huge amounts of sewage sludge produced by municipal wastewater treatment plants induce major environmental and economical issues, calling for advanced disposal methods. Traditional methods for sewage sludge disposal increase greenhouse gas emissions and pollution. Moreover, biochar created from sewage sludge often cannot be used directly in soil applications due to elevated levels of heavy metals and other toxic compounds, which alter soil biota and earthworms. This has limited the application of sewage sludge-derived biochar as a fertilizer. Here, we review biomass and sewage sludge co-pyrolysis with a focus on the stabilization of heavy metals and toxicity reduction of the sludge-derived biochar. We observed that co-pyrolyzing sewage sludge with biomass materials reduced heavy metal concentrations and decreased the environmental risk of sludge-derived biochar by up to 93%. Biochar produced from sewage sludge and biomass co-pyrolysis could enhance the reproduction stimulation of soil biota by 20‒98%. Heavy metals immobilization and transformation are controlled by the co-feed material mixing ratio, pyrolysis temperature, and pyrolysis atmosphere. [ABSTRACT FROM AUTHOR]

Much of Ukraine's soil has been and is still being degraded by military operations. Its revival will need a lot of organic matter, much of which can be provided by municipal sewage sludge. Any associated environmental risks may be minimised by applying the sludge to energy crops, in particular, Miscanthus x giganteus. The introduction of municipal sewage sludge at the rate of 20-40t/ha, or composted with straw, increases the content of total and mobile forms of heavy metals in the soil. But, the resulting concentrations of heavy metals remain well within permissible limits. The integral indicator of soil cover pollution for applications of various kinds of fertiliser applied at a rate equivalent to N90P90K90 fluctuates within insignificant limits (20–23) with a tendency to increase in treatments with the highest rate of application of sewage sludge. [ABSTRACT FROM AUTHOR]

In this study, the potential use of sewage sludge (SS) as a fertilizer source for cultivated Dhaincha (Sesbania bispinosa (Jacq.) W.Wight) crops was investigated. Field experiments were conducted using different doses of SS such as 0% (T0), 5% (T1), 10% (T2), and 15% (T3) to amend the soil (w/w). The findings showed that soil amended with SS significantly (p < 0.05) improved the response parameters of S. bispinosa with an increase in the dose of SS from 0% to 15%. In particular, the T3 treatment gave the best results (mean values) for plant growth and yield parameters such as plant height (380.59 cm), fresh weight (1.47 kg/plant), dry weight (0.27 kg/plant), base diameter (3.19 cm), seed yield (44.71 g/plant), total chlorophyll (3.15 mg/g fwt), carotenoids (0.88 mg/g fwt), carbohydrates (9.40 mg/g), and phenol (0.13 mg/g) contents. Moreover, the selected proximate and fiber characteristics of the S. bispinosa crop were significantly (p < 0.05) improved by the same treatment (T3); such as ash (7.25%), crude fiber (32.70%), crude protein (15.94%), lignin (24.60%), cellulose (37.25%), fiber weight (3.06 g/plant), stick weight (32.08 g/plant), fiber: stick ratio (0.10), fiber diameter (26.97 µm), ultimate tensile strength (855.98 MPa), strength (58.92 g/tex), density (1.54 g/cm3), and luster (45.65%) compared with the control treatment (T0). The bioaccumulation factor (BAF) studies showed that the S. bispinosa plant was capable of accumulating selected heavy metals from the soil following the order: Fe > Mn > Zn > Cu > Cd > Cr. The study suggested a sustainable approach for efficient soil fertilization and high-quality S. bispinosa fiber production that could minimize the environmental pollution caused by the unsafe disposal of SS. [ABSTRACT FROM AUTHOR]

To expand the utilization of solid wastes, this study aimed to construct Technosols using aggregates from domestic sludge, vermicompost, straw, fly ash, and coal cinder, post a three-month constant-temperature incubation, and to elucidate the physicochemical properties of the constructed Technosols of various sizes. The results showed that the pH of the Technosols ranged from 7.08-7.69; the total amount of water-stable aggregates was 49.83%-86.44%; the percentage of aggregate destruction was 13.10%-32.20%; and the mean weight diameter and the geometric mean diameter was 0.54-1.04 mm and 0.54-0.89 mm, respectively. After incubation, soil nitrogen, phosphorus, and potassium availability decreased by 11.03%-38.08%, 5.79%-25.06%, and 0.11%–10.52%, respectively; soil total organic carbon was 5.26%-8.74%, and the overall nutrient content was at a relatively high level. The DTPA-extractable content for Zn and Cd increased and decreased by 15.74%-102.40% and 17.39%-65.02%, respectively. Biotoxicity experiments revealed that nine treatments had no effect on plant growth, and three treatments required adjustment of the aggregation. In general, the characteristics of the Technosols was comparable to that of natural soil relative to soil pH, the total amount and stability of aggregates, and soil nutrients, suggests that the Technosols can be used to reclaim and remediate contaminated soils, and to replace part of natural soils. However, the Technosols should not be used for growing crops such as vegetables and grains, because the sewage sludge leads to a high content of the heavy metal Zn in treatments. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effects of boron and sewage sludge applications on the changes in micro element and heavy metal contents of the cowpea (Vigna unguiculata L.) plant. The experiment was carried out in the climatic chamber, in complete randomized plots, according to the factorial design with 3 replications. In the study where the Karagöz cowpea variety was used, four doses of boron (0 mg/kg, 50 mg/kg, 100 mg/kg, and 200 mg/kg boron) and four doses of sewage sludge (0%, 2.5%, 5%, and 10%) were applied as factors. As a result of the study, micro element contents of cowpea have both increased and decreased with sewage sludge applications, while heavy metal contents except aluminum have increased. The highest values were reached with 5% and 10% sewage sludge applications. Micro element contents generally increased with boron applications. With increasing boron applications, heavy metal contents such as Al, Cd, Co, Cr and Pb increased, while As and Ni contents decreased. It was observed that boron applications tolerated the negativities caused by the sewage sludge in the boron x sewage sludge interaction. Therefore, it can be said that the variable heavy metal contents caused by sewage sludge applications in cowpea plant can be balanced with boron applications. [ABSTRACT FROM AUTHOR]

The unsustainable management of sewage sludge induces environmental and economic issues, yet sewage sludge is a promising feedstock for the production of biofuels by pyrolysis. Actual challenges include poor chemical stability, high water content, high viscosity, high concentrations of nitrogen, and the presence of oxygen in the produced biofuels. Moreover the produced biochars contain elevated amounts of toxic metals and, as a consequence, may not be used in agricultural soils. Here we review the co-pyrolysis of sewage sludge with other materials to enhance bio-oil quality. Several studies show that co-pyrolysis of sewage sludge with non-biomass materials reduces water, oxygen and nitrogen contents, activation energy, and enthalpy; and increases the calorific value. [ABSTRACT FROM AUTHOR]

Hyperthermophilic composting (HTC) is regarded as an effective method for processing sewage sludge. The aim of the study was to investigate effects of using biochar as an amendment on the preservation of nitrogen and passivation of heavy metal during the HTC process of sewage sludge. Results showed that HTC improved the fermentation efficiency and the compost maturity by increases in the temperature and germination index (GI) value, and decreases in the moisture and C/N ratio compared to conventional thermophilic composting. HTC process and the biochar addition resulted in a decrease of the nitrogen loss compared with the control pile during composting by promoting transforming ammonium into nitrite nitrogen. Adding biochar to composting inhibited the transformation of Cu, Zn and Pb into more mobile speciation compared to the control pile although their contents increased during composting, which lead to reduction in availability of heavy metals. Thus, HTC process with the addition of biochar is viable for the reduction of the nitrogen losses and mobility of heavy metal in compost. Implications: The treatment of sewage sludge is imminent due to its threat to general health and ecosystems. This work represents the effects of adding biochar on the preservation of nitrogen and passivation of heavy metal during hyperthermophilic composting of sewage sludge. Our results indicate that the additions of biochar and hyperthermophilic composting engendered the several of positive effects on the preservation of nitrogen and passivation of heavy metal. Thus, HTC process with the addition of biochar is viable for the reduction of the nitrogen losses and mobility of heavy metal in compost. [ABSTRACT FROM AUTHOR]

As increasing soil organic matter is considered one of the main strategies for reducing desertification in Europe, the production and use of high-quality composts has gained importance during the last decade. It is undisputed that the quantity and quality of humic substances (HS) and their fractions, i.e. fulvic acids (FA) and humic acids (HA) in compost are considered important indicators of compost maturity and chemical stability. Other important aspects are concentrations of macro- and micronutrients and heavy metals (HMs) that are introduced to the soil with mature compost. In this light, this study assessed the detailed characteristic of compost from municipal sewage sludge. Moreover, kinetic of organic matter (OM), and nitrogen transformations, therein nitrogen loss, were analysed. OM degradation proceeded according to first-order kinetics. In the bioreactor, the rate constant of OM removal and the rate of OM removal were 0.134 d−1 and 12.6 mg/(g d.m.d), respectively. In the windrow, these constants were 5.2-fold and 16.7-fold lower, respectively. In mature compost, the concentration of HS equaled 240.3 mg C/g OM (1.65-fold higher than in the feedstock) and the concentrations of HA and FA were 120.7 mg C/g OM and 119.6 mg C/g OM, respectively. In FA predominated those with a molecular weight in the range of 10–30 kDa (47.2%), FA with a molecular weight >100 kDa accounted for only 14.4%. In HA, however, fraction with the highest molecular weight (>100 kDa) accounted for more than half (51.2%), while the share of HA with a molecular weight <10 kDa was only 6.8%. During composting, nitrogen loss was observed, which resulted from NH3 rather than N2O emission. In mature compost, organic nitrogen predominated (17.82 g/kg d.m.; ca. 92% of the overall nitrogen). The final concentrations of ammonia nitrogen and nitrate nitrogen were 0.23 and 1.12 g/kg d.m., respectively. The compost met the Polish requirements for the content of HMs (the HMs concentrations were as follows: Cd 1.85 mg/kg d.m., Pb 12.16 mg/kg d.m., Ni 11.05 mg/kg d.m., Cr 24.14 mg/kg d.m., Cu 104.24 mg/kg d.m., Zn 854 mg/kg d.m., Hg 0.12 g/kg d.m.). [ABSTRACT FROM AUTHOR]

The results of a study of the pyrolysis of dried sewage sludge taken from a fixed-bed reactor of urban wastewater treatment plants are presented. The obtained experimental data made it possible to estimate the migration activity of heavy metals entering into the composition of the sewage sludge. Measurements were carried out for vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), strontium (Sr), lead (Pb), rubidium (Rb), barium (Ba), zirconium (Zr), and arsenic (As). It is shown that the emission of heavy metals upon release of volatile substances during pyrolysis is characteristic for almost all of the studied elements, among which As, Rb, Co, and Ba are the elements having the highest migration activity. [ABSTRACT FROM AUTHOR]

The modified sludge derived biochar BC-Fe, BC-RM and BC-Ca was prepared by co-pyrolysis of metal oxide add让ives (Fe2O3, red mud and CaO) and sewage sludge at a mass ratio of 1 ： The influence of additives on the characteristics of the sludgebiochar, as well as the speciation distribution of heavy metals (Pb, Zn, Cu, Cr, Mn) were investigated ・ The ecological risk of the biochar was assessed based on the risk assessment code (RAC)・ The results showed that compared with unmodified biochar (BC), the specific surface area of the three modified sludge derived biochar increased by 58.08%, 189. 58% and 122.99%, respectively, and the microstructure performance of the sludge derived biochar was improved in the meantime・ The study also revealed that Fe2O3 prevented Zn escaping from sludge derived biochar during pyrolysis process・ In addition, compared with BC, the fraction of residual state (F4) of Zn, Pb, Cr, Mn and Cu in BC-Ca increased by 1L76%,13. 03%, 26. 96%, 5. 55% and 2. 11 %, respectively. Heavy metals investigated in the BC-Ca were all in a low risk cond让ion according to the RAC risk assessment standard. [ABSTRACT FROM AUTHOR]

The present study investigates how the original sewage sludge characteristics influence the composition of sewage sludge-based chars for land applications. Sewage sludge from two different wastewater treatment plants in Sweden was pyrolyzed at 500, 700, and 900 °C, and the resulting chars were analyzed. Thermodynamic equilibrium calculations (TEC), together with chemical fractionation, were implemented to simulate the char after the pyrolysis process at different temperatures. The results showed that, in general, for both the municipal sewage sludge (MSS), phosphorus (P) was significantly retained in the char at various temperatures. However, no specific correlation could be found between the pyrolysis temperature and the amount of P remaining. With regard to the heavy metals removed from the char after the pyrolysis reaction, the concentrations of copper, chromium, lead, nickel, zinc, and cadmium were below the limits of the Swedish regulations for farmland application. [ABSTRACT FROM AUTHOR]

Since phosphorus (P) is a nonrenewable element essential for life, it is extremely important to understand its potential supply sources. This paper describes the behavior of P during the ozonation of waste activated sludge (WAS) as it is an important pool of P. Also, we investigated whether ozonation of WAS could be an effective method for both P recovery in solution and its bio- and plant-availability in solid residues based on the analysis by the Standards, Measurements, and Testing Program. The results showed that P was enriched in WAS at concentrations above 23 mg/g. Phosphorus transferred from the solid phase to the liquid phase, and the total P content in the liquid phase increased from 1.67 to 40.68 mg/L as the ozone dosage increased from 0 to 0.20 g O3/g MLSS. PO43–P was the main form of P in the liquid phase after ozonation, which is beneficial for P recovery. The P fraction analysis revealed that the released P mainly came from apatite P (AP) during ozonation. Additionally, P was more available in solid residues as the proportion of bio-available P (non-apatite inorganic P (NAIP) + organic P (OP)) improved from 73.6% in the raw WAS to 91.7% at an ozone dosage of 0.20 O3/g MLSS. In addition, the solid residues were suitable for plant availability at a moderate Fe/P ratio (0.91) after ozonation. Thus, ozonation is recommended as the preferable solution to achieve an advanced P supply in both the liquid phase and solid residues. [ABSTRACT FROM AUTHOR]

The application of sewage sludge to agricultural land is an increasingly popular disposal route and it can be a valuable source of nutrients for crops. Soil properties such as texture, pH value, and ion exchange capacity, strongly influence the availability of trace metals to plants. This paper aims to determine the concentrations of heavy metals (Cd, Cr, Cu, Mn, Pb, and Zn) from wheat, grown in controlled conditions, using two analytical methods as Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The analyzes were carried out at various stages of wheat grain growth and at different concentrations of sewage sludge/soil (0/100, 25/75, 50/50, 75/25, 100/0). The purpose of this paper is to present a method for valorizing sludge from sewage treatment plants, as well as the benefits that this method can have for the growth of cereals, while also looking at the influence and possible accumulation of heavy metals in this plant. [ABSTRACT FROM AUTHOR]

[Display omitted] • BOF slag is an environmental friendly alkalinizing agent for sludge stabilization. • Class A biosolid from sludge was achieved for doses of 4.50gBOF/gTSS 0. • Low C, N and P solubilizations, thus cheapening management cost of liquid fraction. • Low heavy metal mobilizations from sludge and BOF slag during the treatment. This study assessed, for the first time ever, the use of basic oxygen furnace (BOF) slag as alkalinizing material during the sludge conditioning, as an environmentally-friendly alternative to CaO and other conventional alkalis. Its effects on the dewatering, solubilisation and stabilization of sewage sludge were studied, testing increasing dosages of BOF from 0 to 6 gBOF/gTSS 0 at room temperature and under constant mechanical agitation was evaluated. Results revealed that the addition of BOF slag to sewage sludge produced similar degrees of solubilisation to those obtained using lime, reaching a maximum of 34% of total COD for 3.00 gBOF/gTSS 0. The use of BOF slag also involved a low solubilisation of either nitrogen, carbon or phosphorous, a negligible mobilization of heavy metals and a positive effect on its biological hygienisation. A Class A biosolid for doses of 4.50gBOF/gTSS 0 or higher was achieved, which can be applied directly to the soil for agricultural purposes in accordance with current legislation. [ABSTRACT FROM AUTHOR]

The main sources of environmental pollution with heavy (ecotoxic) metals include industry, including utility and municipal power engineering, but also waste incineration plants. Fuel shortages and their constantly growing prices raise concerns that energy will be commonly obtained from waste outside of installations intended for this purpose (i.e., outside waste incineration plants). The greatest concern stems from the risk of burning waste in low-power boilers—domestic boilers. Waste incineration plants and utility power plants are equipped with flue gas cleaning installations (FGD), but low-power boilers are not. The exhaust gases are directly introduced into the atmosphere, which results in the introduction into the air of, inter alia, toxic heavy metals. Therefore, it is necessary to conduct activities aimed at retaining ecotoxic metals in the solid–slag residue. The paper presents the results of laboratory tests of the emission capacity of Cd, Cu, Zn bound in various chemical forms—nitrates (V), chlorides and sulphates (VI). The tests were carried out at 1073 K, 1173 K and 1273 K. It was found that the emissivity of metals increased with increasing temperature. This is innovative as there are no reports of experiments with pure forms of metal salts. The advantage of this type of research is the lack of influence from other factors, apart from temperature, on metal emissions. To check the possibility of reducing metal emissions, additives (bauxite, dolomite, V2O5) immobilized in a solid residue were tested. The mechanism of action of each of the additives to limit the mobility of metals was different. The use of V2O5 for this purpose is new. The additives kept the metals solid in the residue, but their effect was different for each of the metals. The effectiveness of the tested additives was checked in the same temperature conditions, burning waste such as: rubber, sewage sludge and SRF fuel from waste. The effect of the additives depended on the type of waste, type of metal and the furnace temperature. If the additive effectively retained metals, then their amounts in the ashes were higher by several to several dozen percent in relation to the amount in the ashes remaining after waste incineration without additives. The results of the experiment with waste are open to research on the influence of other factors (except temperature) on the emissivity of Cd, Cu, Zn and the possibility of its reduction. The next step will be to verify the effects of laboratory tests in real conditions. [ABSTRACT FROM AUTHOR]

Considering that worldwide the amount of sludge from sewage treatment plants has increased, which through storage pollutes the environment, solutions must be found for its management. In this paper, through an analysis of studies from the literature, we present an ecological method of recovery of sewage sludge (SS) in agriculture through vermicomposting with Eisenia etida, Eisenia andrei, Eudrilus eugeniae and Perionyx excavatus earthworms, thus we analyzed the possibility that sewage sludge can be transformed from waste into quality fertilizer that benefits the soil, plants, and people, thus being able to replace chemical fertilizers which, if applied to the soil, can acidify and pollute the soil and agricultural crops. We observed that the total nitrogen content of the phosphorus increased. Through the vermicomposting process, organic substances are rapidly decomposed and nitrogen mineralization is accelerated. We studied the impact of dewatered sewage sludge vermicomposting on pH value, electrical conductivity, porosity, moisture content, nitrogen content, water retention capacity, metal content, and the development of agricultural crops, highlighting the positive impact of vermicompost application on the soil. Adding vermicompost to the soil has been observed to improve plant development. [ABSTRACT FROM AUTHOR]

• Co-incineration delays polymer and fixed carbon incineration. • High Cl content in MSW promotes volatilization of heavy metals. • P in sludge stabilizes Cu form stable Cu 3 (PO 4) 2 during co-incineration. The effects of sewage sludge phosphorus (P) content on heavy metal behavior during co-incineration of sewage sludge and municipal solid waste (MSW) were evaluated. Thermogravimetric differential thermal analysis revealed that MSW incineration was mainly caused by organic matter and fixed carbon, while sewage sludge incineration was caused by volatile matter. During co-incineration, the peak weight loss at 460 °C shifted to slightly higher temperatures and the sludge ratio increased, indicating that interaction effects during co-incineration delayed pyrolysis and polymer/fixed carbon incineration. The residual heavy metal ratios after mono-incineration of sewage sludge were higher than those after MSW mono-incineration. The Cl content of MSW (0.757%) was much higher than that of sewage sludge (0.068%), which resulted in the conversion of heavy metals into metal chlorides and then volatilized during MSW mono-incineration. A synergistic effect of co-incineration was evident for Cu, but not for lead (Pb) or cadmium (Cd). X-ray absorption fine structure (XAFS) measurement revealed that Cu in MSW ash was in the form of CuO(s), but was Cu 3 (PO 4) 2 in sewage sludge and co-incineration ashes. CuO(s) is relatively unstable and may be transformed to CuO(g) or CuCl(s) before volatilizing at high temperature or in the presence of Cl. Phosphorus has the effect of stabilizing Cu in sewage sludge during co-incineration. [ABSTRACT FROM AUTHOR]

• HTC treatment sanitizes sewage sludge and greatly facilitates P recovery. • HTC temperature and extraction time largely influenced efficiency of P extraction. • Oxalate ions achieved the highest rate of P release at pH > 0. • Ca, Zn, Cu and Pb release with oxalate ions was notably reduced at pH > 1. • Ca and Fe oxalate precipitate was confirmed by XRD. Hydrothermal carbonization (HTC) is a treatment technique with great potential for sanitizing digested sewage sludge (SS) and converting it into valuable products. In particular, phosphorus (P) recovery from hydrothermally carbonized SS has attracted special attention in recent years. This work aims to examine the leaching efficiency of P and the consequent release of metals and heavy metals from SS hydrochars (at 180, 215 and 250 °C) using organic acids (oxalate and citrate) over a range of pH values (0–4) and extraction times (5 min-24 h). Both organic acids triggered P extraction efficiencies exceeding 75 % at the lowest pH, but only oxalate reached a nearly complete P release from hydrochars at pH > 0 and for all carbonization temperatures. Low HTC temperature (180 °C) and short extraction time (5 min) were the optimal conditions treatment for P recovery when reacted in oxalate solutions of maximal pH buffering capacity (pH = 1.4). However, oxalate leaching also transferred metals/heavy metals into the P-leachate, with the exception of Ca being retained in the solid residue from HTC as Ca-oxalate precipitate. Different characterization methods confirmed the presence of this precipitate, and provided information about the surface and morphological changes of the SS hydrochars following acid treatment. The results suggest that HTC not only a promising technique to sanitize and reduce the volume of SS, but also an efficient means for P recovery using oxalic acid, thus contributing to the circular economy of P. [ABSTRACT FROM AUTHOR]

The results of a greenhouse experiment with the humus horizon of a sandy loamy soddy-podzolic soil are presented. It was contaminated with heavy metals added with sewage sludge before 1990, then fodder grasses were grown for 20 years, after that the soil was left for 10 years under fallow. In the experiment, the influence of rhizosphere bacteria of the Pseudomonas genus on the mobility and fractional composition of the compounds of heavy metals: Cu, Zn, Cd, Ni, and Pb in the soil and their entering into the vegetative organs and root system of spring wheat were studied. Under the influence of inoculation with bacteria, the content and ratio of heavy metals compounds in the experimental soil changed with an increase in the contents of mobile Cd and Cd bound with organic matter; and Cu, Ni, Pb, also Zn to a lesser extent, bound with organic matter and iron compounds. At the same time, the contents of Cd and Zn d in the vegetative mass of wheat decreased, and the ratios between the contents of the elements in roots and vegetative mass became wider, which indicated an increase in the plant tolerance towards toxic effect of heavy metals and in the barrier function of the roots. [ABSTRACT FROM AUTHOR]

[Display omitted] Improper disposal of sludge will release heavy metals contained in sludge into soils or waters which could further move through the food chain, posing a risk to human health. Understanding the transformation and stabilization of heavy metals (HMs) during pyrolysis is of great value for safe disposal of sludge. Herein, municipal sewage sludge (MSS, organic-dominated) and pharmacy sludge (PS, inorganic-dominated) were pyrolyzed to investigate the effects of organic and inorganic components and temperature on the stabilization of HMs in sludges. The results showed that pyrolysis can promote the transition of HMs from mobile fractions to stable fractions. Compared to MSS and PS, the potential ecological risk index of biochar derived from MSS and PS decreased by 95.51% and 85.05%, respectively, after pyrolysis at 800 °C. The stabilization of HMs in MSS was mainly due to the complexation reactions between metals and amide functional groups (-CO-NH-) during pyrolysis. Moreover, the mechanism of HMs stabilization in PS lied in the formation of a stable crystal-structure such as copper iron oxide (Cu 6 Fe 3 O 7) and copper iron phosphate (Cu 2 Fe 5 (PO 4) 6 , Cu 3 Fe 4 (PO 4) 6) with iron-containing minerals after high-temperature pyrolysis. The results of this study indicated that the organic and inorganic components of sludge play different roles in the stabilization and transformation of HMs during pyrolysis, which provided a scientific basis for the ecotoxicity reduction of HMs and safe disposal of sludge. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the heavy metal (HM: Cd, Cr, Cu, Ni, Pb, Zn, and Hg) content in particular chemical fractions (forms) of sewage sludge with different characteristics (primary and dewatered sludge) using conventional (CSE) and ultrasound-assisted (USE) BCR sequential extraction methods (Community Bureau of Reference, now the Standards, Measurements and Testing Programme). The concentrations of HMs were determined using inductively coupled plasma optical spectrometry (ICP-OES). Only mercury was assayed with cold vapor atomic absorption spectrometry (CVAAS). Ultrasound treatment was conducted in the ultrasonic bath (Sonic 5, Polsonic). The optimal sonication time (30 min) was determined using ERM-CC144 (Joint Research Center; JCR) certified reference material. The conducted experiment revealed that the use of ultrasound waves shortened the extraction time to 4 h and 30 min (Stages I to III). The recoveries (RM) of heavy metals ranged from 62.8% to 130.2% (CSE) and from 79.8% to 135.7% (USE) for primary sludge, and from 87.2% to 113.2% (CSE) and from 87.8% to 112.0% (USE) for dewatered sludge. The only exception was Hg in dewatered sludge. The conducted research revealed minor differences in the concentrations and fractionation patterns for Cd, Ni, and Zn extracted from sludge samples by the tested methods. However, it was confirmed that the above findings do not significantly affect the results of a potential ecological risk assessment (with minor exceptions for Cd and Zn in the primary sludge), which is extremely essential for the natural use of sludge, and especially dewatered sludge (the final sludge). The shorter extraction time and lower energy consumption prove that ultrasound-assisted extraction is a fast and simple method for HM fractionation, and that it provides an alternative to the conventional procedure. Therefore, it can be considered a "green method" for the assessment of the bioavailability and mobility of heavy metals in solid samples. [ABSTRACT FROM AUTHOR]

Sewage sludge (SS) is derived from wastewater treatment plants and can be used as a biofertilizer when properly stabilized. This work aimed to evaluate SS application for agricultural production improvement. SS was tested on Porto Santo Island (Portugal). The experiment was randomly designed with three 25 m2 plots for each treatment (2 SS concentrations + control without SS) and performed in two consecutive cycles. For the first cycle, dehydrated sludge was mixed with soil, obtaining final concentrations of 0.8 kg/m2 (C1) and 1.6 kg/m2 (C2). Half of the concentration was used for the second cycle. Fifty-eight sweet potato plants were used in each plot. SS application boosted the agronomic parameters of biomass, productivity, and shoot biomass. Furthermore, improvements in soil properties were observed, mainly for pH, CEC, and NO3-N, with no significant increase in heavy metals. For the edible parts, heavy metal concentrations decreased, and Pb was the only one that still exceeded the maximum limits. The results demonstrated that SS application to low-fertility soil is effective in improving the agronomic parameters of sweet potato and enhancing soil features. Further studies considering other variables, i.e., SS origin, soil properties, and the crop, must be carried out to propose custom applications. [ABSTRACT FROM AUTHOR]

This research is concerned with the adsorption and desorption of Cu and As(V) on/from different soils and by-products. Both contaminants may reach soils by the spreading of manure/slurries, wastewater, sewage sludge, or pesticides, and also due to pollution caused by mining and industrial activities. Different crop soils were sampled in A Limia (AL) and Sarria (S) (Galicia, NW Spain). Three low-cost by-products were selected to evaluate their bio-adsorbent potential: pine bark, oak ash, and mussel shell. The adsorption/desorption studies were carried out by means of batch-type experiments, adding increasing and individual concentrations of Cu and As(V). The fit of the adsorption data to the Langmuir, Freundlich, and Temkin models was assessed, with good results in some cases, but with high estimation errors in others. Cu retention was higher in soils with high organic matter and/or pH, reaching almost 100%, while the desorption was less than 15%. The As(V) adsorption percentage clearly decreased for higher As doses, especially in S soils, from 60–100% to 10–40%. The As(V) desorption was closely related to soil acidity, being higher for soils with higher pH values (S soils), in which up to 66% of the As(V) previously adsorbed can be desorbed. The three by-products showed high Cu adsorption, especially oak ash, which adsorbed all the Cu added in a rather irreversible manner. Oak ash also adsorbed a high amount of As(V) (>80%) in a rather non-reversible way, while mussel shell adsorbed between 7 and 33% of the added As(V), and pine bark adsorbed less than 12%, with both by-products reaching 35% desorption. Based on the adsorption and desorption data, oak ash performed as an excellent adsorbent for both Cu and As(V), a fact favored by its high pH and the presence of non-crystalline minerals and different oxides and carbonates. Overall, the results of this research can be relevant when designing strategies to prevent Cu and As(V) pollution affecting soils, waterbodies, and plants, and therefore have repercussions on public health and the environment. [ABSTRACT FROM AUTHOR]

This study assessed the effect of different lignocellulosic amendments and bulking agents on compost stability (based on a 4 day respiration activity test, AT4, and self-heating factor, SHF) and maturity (based on the nitrification index Initr and the ratio of C in humic acids, HA, to total organic carbon, TOC, in compost, CHA/TOC). With all feedstock compositions (FCs), the share of sewage sludge was 79% (wet mass). For FC1, wood chips (13.5%) and wheat straw (7.5%) were used as bulking agents and amendments; for FC2, instead of wood chips, energy willow was added; for FC3, pine bark (13.5%) and conifer sawdust (7.5%) were used. All FCs produced stable and mature compost; however, with FC2, the thermophilic phase last 3 days longer than with the other FCs. Moreover, an AT4 value below 10 g O2/kg dry mass (d.m.) was obtained the earliest with FC2 (after 45 days, ca. 15–20 days earlier than with other FCs). With FC2, Initr below 0.5 was obtained in ca. 60 days, 10 days earlier than with FC3 and 30 days earlier than with FC1. The highest net increases in HS (86.0 mg C/g organic matter (OM)) and HA (56.3 mg C/g OM) were also noted with FC2; with other FCs, the concentrations of these compounds were from 1.3- to 1.5-fold (HS) and from 1.4- to 1.9-fold (HA) lower. With FC2, the highest CHA/TOC (15.5%) was also noted, indicating that this compost contained the largest share of the most stable form of organic carbon. The rates of OM removal in the bioreactor ranged from 7.8 to 10.1 g/(kg d.m.·day). The rates of SH and HA formation ranged from 1.63 to 4.83 mg C/(g OM·day) and from 1.23 to 1.80 mg C/(g OM·day), respectively. This means that, through the choice of the amendments and bulking agents, the length of the composting time needed to obtain a stable and mature product can be controlled. [ABSTRACT FROM AUTHOR]

Concrete is currently the most widely used man-made composite material and second only to water in the entire range of materials used. It is a material with a high potential to adapt to specific operating conditions and can be made from local raw materials (aggregate, cement, water, and mineral additives), which can be selected to minimize the carbon footprint. The use of fly ash from the thermal conversion of sewage sludge in concrete is in accord with the advice on waste management proposed in the European Union. This paper presents the results of research on the effect of the partial replacement of Portland cement with this material on the strength parameters, frost resistance, and carbonation of concrete compared to reference concrete and to concrete containing a conventional additive - siliceous fly ash. In addition, the potential environmental impact of the use of sewage sludge ash was investigated by determining the leachability of heavy metals. Concrete mixtures of C20/25 ordinary concrete, based on CEM I 42.5R Portland cement, with varying ash contents comprising 0-20% of the cement mass, were produced for the experimental work. The obtained test results confirmed the possibility of producing plain concrete modified with fly ash from the thermal treatment of sewage sludge and the concrete's compliance with the environmental requirements relating to the leaching of heavy metals. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants are facilities where wastewater is treated by technological processes. A byproduct of a wastewater treatment plant is sewage sludge, which can be both a good soil conditioner and a source of nutrients for the crops to which it is applied. Energy crops are non-food plants that can cleanse the soil of heavy metals through their ability to phytoremediate. The purpose of this study is to determine the effects of different amounts of sewage sludge on soil and plants. In the experiment Virginia mallow (Sida hermaphrodita L.) was used and the influence of stabilized sewage sludge in the amounts of 1.66, 3.32 and 6.64 t/ha dry matter on the energy composition and biomass yield was observed.The obtained results showed a yield of 8.85 t/ha at the maximum amount of sewage sludge used. Hemicellulose content was 20.20% in the application of 6.64 t/ha of sewage sludge and 19.70% in the control, while lignin content was 17.97% in the control and 16.77% in the maximum amount of sewage sludge. The heavy metals molybdenum and nickel did not differ significantly under the influence of larger amounts of sewage sludge, while manganese increased from 23.66 to 35.82 mg/kg. [ABSTRACT FROM AUTHOR]