Sewage Sludge Biochar Research Articles

Effect of raw sewage sludge and sewage sludge biochar on soil physicochemical properties and seed germination of Solanum lycopersicum

AbstractVarious experts have been concerned about the safety usage of sludge generated during wastewater treatment and its disposal in the environment. Biochar made from sewage sludge was studied for its efficiency in enhancing soil quality, reducing heavy metal uptake, and potential benefits in agriculture areas to enrich the soil. The objectives of the present study were to examine the feasibility of raw sewage sludge (RSS) and sewage sludge biochar (SSB), which were produced at 400 and 500°C, as a soil amendment, and the effect of sewage sludge biochar on seed germination of Solanum lycopersicum. Present study included seven treatments: (i) T0 (Control); (ii) T1 (RSS, 1%); (iii) T2 (RSS, 2.5%); (iv) T3 (SSB400°C, 1%); (v) T4 (SSB400°C, 2.5%); (vi) T5 (SSB500°C, 1%); and (vii) T6 (SSB500°C, 2.5%). The addition of sewage sludge and its biochar enhanced electrical conductivity (EC), total organic carbon (TOC), sodium (Na) and potassium (K), and soil enzymatic activity when compared to control. The pH value of the soil amended with RSS increased by 0.04–0.1 units as compared to control. The treatments with the higher concentration (2.5%) of RSS and SSB significantly increased the concentration of Na whereas, SSB400°C, 2.5% significantly increased the K concentration in soil in comparison to control. The TOC in soil increased in all the RSS and SSB amended treatments and ranged between 1.16 and 1.83 %. Seeds of Solanum lycopersicum treated with SSB at 500°C had shown maximum germination (90%) and germination index (103.01 ± 1.41). The increase in the alkaline phosphatase activity was significant and was maximum 25.2 μg 4‐nitrophenol g−1 soil h−1 for T2 followed by T4 which was 24.9 μg 4‐nitrophenol g−1 soil h−1. The results demonstrate that the RSS and SSB at 2.5% concentration are potential organic amendments to promote the soil nutrients.

Sewage Sludge Biochar: Physicochemical Properties and Fractionation of Zinc and Lead Metals

Sewage Sludge Biochar: Physicochemical Properties and Fractionation of Zinc and Lead Metals

Biochar and its combination with inorganic or organic amendment on growth, uptake and accumulation of cadmium on lettuce

Biochar as an environmentally friendly soil amendment, has attracted widespread attention and in combination with other amendments is considered to be more conducive to crop growth, soil fertility, and crop safety production. However, a comprehensive understanding of the differences among different biochars, biochar with inorganic amendment, and biochar with organic amendment with respect to soil health, plant growth, and Cd bioavailability or phytoavailability is necessary. Therefore, a sixty-day pot experiment was conducted to investigate the effects of five biochars derived from rice husk (RH), pig manure (PM), sewage sludge (SS), corn straw (CS), and wood chip (WC) and their respective combination with lime or compost on cadmium (Cd) immobilization and adsorption as well as physicochemical features and enzyme activities in contaminated soil. The results revealed that the sole application of PM, SS, and CS biochars had a positive impact on lettuce growth and photosynthetic pigments. In addition, mixing PM or SS biochar with compost further promoted lettuce growth due to higher soil fertility and enzyme activities. However, as compared to unamended soil, CS biochar-compost combination, RH, PM, SS, and CS biochar-lime combination highly reduced lettuce plant height and fresh weight. Furthermore, the application of amendments with biochar-lime mixtures greatly reduced Cd bioavailability. X-ray diffraction analysis and Fourier Transform Infrared spectra revealed that Cd immobilization mainly involved complexation and co-precipitation on mineral surfaces as well as hydroxyl or carboxyl functional groups in amendments. In comparison to a single application and biochar-lime combination, the biochar-compost combinations i.e RH, PM, SS, and WC were more effective in lowering Cd translocation and bioaccumulation in lettuce.

Enhancement of heavy metal immobilization in sewage sludge biochar by combining alkaline hydrothermal treatment and pyrolysis

Heavy metals, including Cd, As, Ni, Cu, Pb, Cr, Zn, and Mn in sewage sludge (SS) are among the greatest impediments to SS application because of their potential toxicity to living organisms and latent environmental pollution risks. In this study, hydrothermal treatment (HT)/alkaline HT combined with pyrolysis was used to treat SS for heavy metal immobilization. The heavy metal characteristics, including total, fraction, and leaching concentrations and potential ecological risks, were comprehensively investigated to ensure the safe application of biochar. The results showed that the heavy metals mainly remained in the hydrochar and biochar. Additionally, both HT and alkaline HT promoted the residual fractions of Cr, Zn, Ni, and Cu in biochar. Furthermore, alkaline HT-aided pyrolysis was more effective for immobilizing Zn and Ni with their residual fractions increasing by 100% and 60% respectively, compared with direct sludge pyrolysis. Moreover, the ecological risk of heavy metals in SS significantly decreased from 57.27 to 30.05 after alkaline HT-combined pyrolysis treatment, contributing to the low potential ecological risk of SS-based biochar. This study provides a promising strategy for converting SS to biochar with improved heavy metal immobilization.

Removal of Cr(VI) from aqueous solution by a novel ZnO-sludge biochar composite.

The incorporation of ZnO into biochar has become a promising way to obtain adsorbents with enhanced adsorption capacity. In this study, a low-cost ZnO-sludge biochar composite (ZBC) was prepared by a simply in situ method using sewage sludge biochar (SBC) and zinc acetate, as well as employed for Cr(VI) adsorption in water. The results of XPS and FT-IR suggested that the ZBC surface had more functional groups such as -COOH, -OH, -C-O, ZnO, etc. Compared with SBC, the BET-specific surface area of the ZBC increased from 8.82 to 41.24 m2·g-1, which provides potential advantages for Cr(VI) uptake. Benefiting from ZnO incorporation, about an 18% increase in Cr(VI) removal efficiency was obtained. The maximum removal efficiency and equilibrium adsorption amount of ZBC for Cr(VI) reached 98.4% and 33.87 mg·g-1, respectively. The adsorption was spontaneous and endothermic nature, and coincided nicely with pseudo-second-order kinetics and Langmuir isotherm. The analyses indicated that Cr(VI) removal by ZBC was predominantly via electrostatic attraction, surface complexation, ion exchange, and reduction. This study provided valuable insights into the problem of sludge disposal and provided a new and effective method for Cr(VI) removal.

Efficient substrates based on anaerobic sewage sludge biochar for tobacco seedlings in floating systems

ABSTRACT The objective was to develop efficient substrates, with increasing proportions of biochar derived from anaerobic sewage sludge (ASS-biochar) and regionally available raw materials, to produce tobacco seedlings (Nicotiana tabacum) in floating systems. Physical, hydraulic and chemical variables and the effects on tobacco plants were evaluated through an indoor experiment with seedling production. The experiment was conducted on trays in a floating hydroponic system in a randomized block design with four replications and eight plants per plot. The ASS-biochar showed environmental safety and agronomic efficiency in substrate composition, in particular with 50% to 90% ASS-biochar in the formulation. The best formulations positively affected the growth-related variables, showing similar or superior performance to the three commercial substrates (references). The ideal ranges of the substrate characteristics were: dry density: 420–520 kg m−3; total porosity: 60–75%; aeration space: 25–35%; easily available water: 9–12%; water buffering capacity: 3–5%; available water: 12–15%; remaining water: 20–25%; pH: 6.0–6.5; electrical conductivity: 1.4–2.3 mS cm−1. The development of substrates considering ASS-biochar, regional raw materials and ideal physical-chemical properties would prevent environmental pollution by generating value-added products to improve tobacco seedlings and expand the productivity and quality of tobacco worldwide.

Impact of Pyrolysis Temperature and Application Amount of Sewage Sludge Biochar on the Speciation and Bioavailability of Cd and Pb in Paddy Soil

Impact of Pyrolysis Temperature and Application Amount of Sewage Sludge Biochar on the Speciation and Bioavailability of Cd and Pb in Paddy Soil

Immobilization of Cd and Pb in soil facilitated by magnetic biochar: metal speciation and microbial community evolution.

The preparation of magnetic biochar from sewage sludge and rice straw for heavy metal contaminated soil remediation has greater application prospects, but its remediation mechanism was rarely considered by combining soil physicochemical properties with microbial community. In this study, the effects of magnetic sewage sludge biochar (SSB) and rice straw biochar (RSB) on Cd and Pb immobilization in paddy soil were compared and analyzed by 60-day soil incubation experiments. The results illustrated that DTPA-Cd and DTPA-Pb were reduced by 51.53% (43.07%) and 53.57% (50.47%), while the percentage of residual fraction of the BCR procedure was enhanced by 31.27% (30.78%) of Cd and 27.25% (23.22%) of Pb in the SSB (RSB) treatment, respectively. Fe was detected on both SSB and RSB surfaces, but SSB had rougher and a larger specific surface area compared to RSB. The addition of SSB and RSB in paddy soil increased soil pH and TOC content, and affected the diversity and species of soil microbial community. Compared with the CK group, the relative abundance of Proteobacteria, Bacteroidota, and Lysobacter decreased, and the relative abundance of Actinobacteriota, Pontibacter, and Alkaliphilus increased with SSB and RSB treatments, all of which reflected the bioavailability of Cd and Pb reduction.

Co-pyrolysis biochar derived from sewage sludge and lignin: Synergetic effect and adsorption properties

Co-pyrolysis of sewage sludge (SS) and biomass is expected to improve the biochar quality. Lignin as a major component of biomass was selected for co-pyrolysis with SS. The characteristics and kinetics of co-pyrolysis were studied by thermogravimetric analyzer/differential scanning calorimetry (TGA/DSC) and Coats-Redfern method; the effects of pyrolysis temperature and mixing proportion on the biochar yield were investigated via muffle furnace experiment, and the porosity and methylene blue (MB) adsorption capacity of the obtained co-pyrolysis biochar were evaluated. The results showed that co-pyrolysis promoted the decomposition of mixture and reduced the reaction temperature. The reaction order model was the primary mechanism model for co-pyrolysis, and both promotion and inhibition effects were observed based on the obtained activation energy. At 400 ℃ and 600 ℃, the co-pyrolysis synergetic effect on biochar yield was weak, and synergy effect of inhibition on the porosity of biochar was caused by tar and ash adhesion. When temperature was elevated to 800 ℃, catalytic effect of alkali and alkaline earth metals (AAEMs) dominated the synergetic effect, promoted char decomposition, meanwhile, pores were dramatically developed. Co-pyrolysis of SS and lignin improved MB adsorption capacity of SS biochar from 14.04 mg g−1 to 180.36 mg g−1, indicating it to be a prospective method for waste to valuable biochar production.

Speciation Evolution of Phosphorus and Sulfur Derived from Sewage Sludge Biochar in Soil: Ageing Effects.

Phosphorus (P) and sulfur (S) are usually involved simultaneously in the immobilization of heavy metals in sewage sludge during pyrolysis, and thus their speciation in sewage sludge-derived biochar (SSB) profoundly affects the recycling of the nutrients and the environmental risks of sewage sludge. Here, we investigated the speciation evolution of P and S in SSB induced by ageing processes in soil using X-ray absorption near edge structure spectroscopy. Results showed that Ca-bound compounds like hydroxyapatite dominated the P forms, while over 60% of S existed as reduced inorganic sulfides in the SSB. The stable Ca-associated P species in SSB tended to be transformed gradually into relatively soluble species during ageing in soil. The speciation composition of S in SSB remained almost unaffected when aged in pot soils, whereas about 33.6% of reduced sulfides were transformed into oxidized species after 1-year ageing in field soils. SSB significantly increased the proportion of sulfides and the contents of available P and S in the amended soil but showed relatively weak effects on the speciation distribution of P in the soil because of their similar compositions. These findings provide insights into biogeochemistry of nutrients and behaviors of heavy metals in SSB after its application to the soil environments.

Effects of pyrolysis temperature on biochar’s characteristics and speciation and environmental risks of heavy metals in sewage sludge biochars

Sewage sludge pyrolysis into biochar is an effective way to realize sludge harmless and resourceful utilization. The study aimed to investigate the relationship between pyrolysis temperatures (300 °C, 500 °C and 700 °C) and biochar properties and environmental risks associated with heavy metals (Cu, Zn, Pb, Cd, Ni and Cr) and to discuss possible mechanisms of heavy metal immobilization. The results showed that the biochar pH value increased from 5.87 to 10.50 and the specific area grew from 5.26 m 2 /g to a maximum of 15.23 m 2 /g with pyrolysis temperature rose. Pyrolysis enhanced aromatization and increased stability of biochar, and part of oxygen-containing functional groups decomposed. Although heavy metals enriched in pyrolysis, high temperatures promoted the bioavailable fractions converted to more stable ones, and the heavy metals leaching rate was reduced by 5.5% on average. This may be related to the functional group decomposition, pore collapse and wrapping, and the new crystalline phases formation. The environmental risk was significantly reduced ( RI value below 51.00), indicating the relatively safe and reliable performance of sludge biochar. The study can provide a theoretical basis for sludge management and the biochar safe use in soil. • The pyrolysis temperature had a significant effect on the sludge biochar properties. • Heavy metal immobilization related to biochar surface structure and functional group. • Pyrolysis significantly reduced the heavy metals environmental risk in biochar. • Sludge biochar can be used as a potential improver for poor soil.

Evaluation of the Use of Sewage Sludge Biochar as a Soil Amendment—A Review

In recent decades, minimization and recycling/reuse policies were introduced to reduce the quantities of generated waste and for alternative waste recovery. Organic wastes represent 46% of total global solid waste. Possible uses of organic wastes include using it as fertilizer and amendment for soil, for energy recovery and for the production of chemical substances. Sewage sludge disposal and reuse are identified as future problems concerning waste. The total amount of sludge generated in the entire world has increased dramatically, and this tendency is expected to increase significantly in the years to come. In most developed countries, special attention is given to sewage sludge treatment in order to improve the quality and safety of using it on the ground surface. Sewage sludge pyrolysis is considered an acceptable method, from an economic and ecological perspective, for the beneficial reuse of sewage sludge. This method has many advantages because, during the pyrolysis process, the sludge volume is reduced by 80%, pathogenic agents and hazardous compounds from sewage sludge are eliminated, metals are immobilized in solid residue and organic and inorganic fractions are immobilized in a stabilized form of pyrolytic residues (biochar). The biochar generated by sewage sludge pyrolysis does not contain pathogenic agents and is rich in carbon and nutrients.

Nutritional Evaluation by the DRIS Method of Corn Plants Fertilized with Sewage Sludge Biochar

ABSTRACT Through pyrolysis it is possible to transform sewage sludge (SS) into a product called biochar, which can be used safely in agriculture as a soil amendment. Among the advantages of using SS biochar (SSB) are the supply of nutrients and carbon sequestration in the soil. However, there is still a lack of information on the supply of nutrients and the nutritional balance provided by SSB application. The objective of this study was to evaluate the nutritional status of corn plants fertilized with SS biochar by the DRIS method. Soil and plant data from a three-year field experiment were assessed. The field experiment, with four replications, consisted of the following treatments: 1) control, no biochar and no mineral fertilization; 2) mineral fertilization; 3) biochar produced at 300°C; 4) BC300 associated with mineral fertilization; 5) biochar produced at 500°C; 6) BC500 associated with mineral fertilization. In the present study, leaf samples of corn cultivated for three consecutive harvests were used. From the DRIS indexes, it was concluded that potassium is the most limiting nutrient for SSB. Despite that, according to outputs from DRIS, SSB has a good potential as a fertilizer, especially if supplemented with K.

Characteristics of Biochars Derived from the Pyrolysis and Co-Pyrolysis of Rubberwood Sawdust and Sewage Sludge for Further Applications

This study investigated the characteristics of biochars derived from the pyrolysis of rubberwood sawdust (RWS) and sewage sludge (SS) and their co-pyrolysis at mixing ratios of 50:50 and 75:25. Biochars were produced at 550 °C through slow pyrolysis in a moving bed reactor and then characterized. Results showed that the rubberwood sawdust biochar (RWSB) had high carbon content (86.70 wt%) and low oxygen content (7.89 wt%). By contrast, the sewage sludge biochar (SSB) had high ash content (65.61 wt%) and low carbon content (24.27 wt%). The blending of RWS with SS at the mentioned ratios helped enhance the gross and element contents of the biochar samples. The elemental analysis of the biochars was also reported in the form of atomic ratios (H/C and O/C). The functional groups of biochars were observed by Fourier-transform infrared spectroscopy (FTIR). X-ray fluorescence spectroscopy (XRF) revealed that the biochar from SS contained a high content of inorganic elements, such as Si, Ca, Fe, K, Mg, P, and Zn. The pH of the biochars ranged from 8.41 to 10.02. Brunauer, Emmett, and Teller (BET) and scanning electron microscopy (SEM) showed that RWSB had a lower surface area and larger pore diameter than the other biochars. The water holding capacity (WHC) and water releasing ability (WRA) of the biochars were in the range of 1.01–3.08 mL/g and 1.19–52.42 wt%, respectively. These results will be the guideline for further application and study of biochar from RWS, SS, and blended samples.

Removal of phosphate by a novel activated sewage sludge biochar: Equilibrium, kinetic and mechanism studies

In this study, a novel biochar adsorbent (Mg-SB) modified by magnesium oxide particles is synthesized via pyrolysis of activated sewage sludge. Its phosphate removal performance is explored in aqueous environment under various conditions. It is found that Mg-SB could effectively remove phosphate with the maximum capacity of 97,450 mg kg−1 PO43−. The values are favorable compared to other adsorbents in the literatures. The pH and ionic strength can obviously affect the adsorption of phosphate onto Mg-SB. The adsorption data are best fitted by the pseudo-first-order model and the Langmuir model. Characterization of adsorbents with SEM-EDS, XRD and FTIR showed magnesium oxide on Mg-SB surface was the main phosphate adsorption site. Furthermore, the high phosphate adsorption efficiency and bioavailability makes the P-load-Mg-SB possible to directly apply to agricultural fields as a slow release fertilizer to improve soil fertility or to restore the contaminate soil.

Production of magnetic sewage sludge biochar: investigation of the activation mechanism and effect of the activating agent and temperature

Sewage sludge-based porous materials were prepared through an integrated and energy-saving procedure that combines chemical activation with an alkali (NaOH or K2CO3) and physical activation with CO2 in a single step. The study was conducted in a wide temperature range (600–1000 °C), using higher temperatures than those commonly used. From the standpoint of textural properties, the impregnation results in a decrease in the optimum activation temperature: 800 °C for untreated samples, and 600–700 °C for impregnated samples. The impregnation increases the amount of –OH and –NH functional groups, and it also leads to the generation of new oxygen- and/or nitrogen-containing functionalities (above 800 °C for the impregnation with K2CO3 and in the whole temperature range for the impregnation with NaOH). The chemical treatment favors the development of magnetic properties on biochars, which is an advantage for its reuse in wastewater treatment, since it favors the removal of anionic surfactants and heavy metals such as lead, copper, zinc, and manganese. The uptake of phenol and methylene blue (MB) is maximized with the combination of the impregnation (with NaOH for phenol and K2CO3 for MB) and the use of a moderate temperature (600–700 °C). The optimum uptake values represent an increase of 87% and 152% for MB and phenol, respectively, compared to the highest value of non-impregnated samples (activated at 800 °C), with the advantage of the lower temperature required.Graphical abstract

Arsenic immobilization in calcareous soils amended with native and chemically modified sewage sludge biochar: kinetics and equilibrium studies

Arsenic immobilization in calcareous soils amended with native and chemically modified sewage sludge biochar: kinetics and equilibrium studies

Potential of biochar derived from three biomass wastes as an electrode catalyzing oxygen reduction reaction

ABSTRACT Biochar is a porous carbonaceous material containing abundant redox functional groups and inorganic minerals, making it a potential electrode material. Nine electrodes were prepared with biochar produced from three different feedstocks at three pyrolysis temperatures, and their oxygen reduction reaction (ORR) activity and electrochemical impedance spectroscopy (EIS) were investigated. The results showed that all biochar electrodes had certain electrocatalytic activity as their current density ranged from 0.26 to 2.17 mA cm−2, half-wave potential at 0.24–0.41 V, electron transfer number at 2.1–3.9, Rct at 9.2–61.2 Ω, and Cdl at 1.1 × 10−6 – 2.2 × 10−4 F. For most biochar electrodes, the current density and half-wave potential increased as the pyrolysis temperature increased from 500°C to 700°C, which was closely related to the increase in aromatization degree (H/C) of biochar. Dairy manure biochar showed much lower current density and half-wave potential than sewage sludge biochar and wood chip biochar, probably due to its relatively smaller surface area. This study indicated that biochars could be converted to carbon electrodes, and both feedstock and pyrolysis temperature could influence the ORR activity of biochar electrodes.

Aging features of metal(loid)s in biochar-amended soil: Effects of biochar type and aging method

Soil contamination with toxic metals and metalloids has become a major threat to global food security. Among various immobilization agents that can stabilize toxic metal(loid)s effectively, biochar is promising due to its ability to restore soil health. Yet the aging characteristics of biochar following its amendment in soil remain poorly explored. Therefore, this study used standard biochars to depict their aging effects on remediation of metal(loid)-contaminated soil. A total of 2304 observations were made, including 6 biochar feedstocks (rice husk, soft wood, oilseed rape straw, miscanthus straw, sewage sludge and wheat straw), 2 pyrolysis temperatures (550 °C, 700 °C), 8 metal(loid)s (Mn, Ni, Cu, Zn, As, Cd, Sb, Pb), 4 aging methods (natural aging, freeze-thaw cycling, wet-dry cycling, chemical oxidation with H2O2), and 6 sampling intervals. Sewage sludge biochars exhibited the highest resistance to both artificial and natural aging, which may be related to the abundant oxygen-containing functional groups that favor metal complexation, and poorly-developed pore structures that limit the access of natural aging forces. A distinct relationship between ash and temperature was observed, where for high-ash biochars, an increase in pyrolysis temperature indicated lower resistance to aging, while for low-ash biochars, elevated pyrolysis temperature led to higher resistance. The aging behaviors of Cu and Sb were quite similar, which were both highly susceptible to chemical oxidation-induced dissolved organic carbon (DOC) release. Wet-dry cycling and freeze-thaw cycling revealed aging patterns that were similar to those of naturally aged soils as confirmed by cluster analysis. Lab aging data were then compared with existing biochar field aging results. Contrasting long-term immobilization performances were found in different studies, which were attributed to various causes associated with both biochar property and climate. The results of this study provide fresh insights into the long-term risks in the management of metal(loid)-contaminated agricultural soils.

Petrochemical Wastewater Treatment by Eggshell Modified Biochar as Adsorbent: Atechno-Economic and Sustainable Approach

Petrochemical industrial wastewater (PIW)contains toluene and xylene (TX), and various organic and inorganic pollutants, causing severe risks to human health if improperly released into the environmental matrices. For the long-term reliability of environmental conservation, this study illustrates the interlinkage between PIW treatment and the three pillars of sustainable development. Sewage sludge biochar was modified with eggshell, showing a relatively high fixed C content (increase in carbonization degree), and small O/C and N/C ratios. The prepared biochar was employed for TX adsorption in mono-component solutions, giving removal efficiencies of 79.1% (T) and 86.6% (X), at pH =10, adsorbent dosage =2 g/L, and Co =40 mg/L within 60 min. The main adsorption mechanism was physisorption, including precipitation/pore-filling, π- π dispersive interaction, and van der Waals force. The modified biochar also treated real PIW under five adsorption/regeneration cycles, providing essential steps toward large-scale applications. According to an economic feasibility estimation, the biochar application for treating 1 m3 of PIW would offer a payback period of 6.9 yr. The study outputs could be linked to the restoration of water-related ecosystems, biochar modification for industrial applications, and climate change mitigation, adopting the 2030 agenda and its sustainable development goals (SDGs).