Search

The disposal of fly ash (FA) from coal power plants polluting the air, soil, and groundwater is a major environmental concern. Phytoremediation to rehabilitate fly ash dumpsites is a promising alternative but has practical concerns about the disposal of harvested biomass. This study investigated the effect of supplementing fly ash with fresh sewage sludge (FSS), aged sewage sludge, food waste, and compost (COM) to enhance the phytoremediation potential of Napier grass and its subsequent utilization for ethanol production. The highest removal of Mn (1196.12 g ha−1) and Ni (128.06 g ha−1) from FA could be obtained when Napier is grown in the presence of FSS and inorganic fertilizer (NPK). In addition, the highest bioethanol yield (19.31 g L−1) was obtained from Napier grown in fly ash with COM + NPK, thus providing additional economic benefits aside from the remediation process. Given the significant levels of heavy metals present in the pulp and bio-slurry after ethanol production, further research is required in this area to determine the best ways to utilize this waste such as converting it into biochar. Using energy crops as a phytoremediation agent for fly ash dumpsites has the potential to remediate heavy metal contamination and provide additional economic benefits. Napier grass was able to tolerate high concentrations of heavy metals and yield high biomass in fly ash in the presence of organic amendments. The harvested biomass was successfully converted into substrate for bioethanol production using heavy metal-tolerant yeast. This is the first report on the production of ethanol from the phytoremediation biomass of Napier grass. [ABSTRACT FROM AUTHOR]

Numerous tons of hazardous wastes containing persistent organic pollutants (POPs) are stored in an unsafe manner in the petrochemical industries. The planetary ball mill causes the formation of mineral Cl compounds during the degradation of polychlorinated compounds in the presence of various reagents. In addition, the planetary ball mill has been applied for the synthesis of diverse organic-inorganic hybrid nanomaterials. In the present study, Fe-metal organic framework was prepared using a planetary ball mill, and then Fe@C nanocomposite with core/shell structure was synthesised by carbonisation. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) were utilised to study the synthesised materials. The nanocomposite was used as a reagent to degrade persistent organic pollutants in the sludge of a petrochemical wastewater treatment plant by a planetary ball mill. CaO was also used to compare the effect of nanocomposites on system performance. Ion chromatography (IC) analysis was carried out to determine chlorine mineralisation. Furthermore, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were applied to determine chemical bonds. The results illustrated a zero-valent iron nanoparticle in the core protected by carbon shell in a synthesised nanocomposite with a core/shell structure. Hence, nanocomposite was the most efficient additive, with 97% dechlorination efficiency in the first hour while the efficiency of the planetary ball mill in the presence of CaO was only 76% after 12 hours of milling. Furthermore, major changes occurred in the organic phases, carbon and chlorine bonds. Simultaneously, graphite and amorphous carbon were produced in the final products after milling. This indicates that aromatic structures and C-Cl bonds were broken down into inorganic compounds. Thus, this study presented a practical method of producing materials while degrading hazardous pollutants in petrochemical wastewater sludge through a planetary ball mill. [ABSTRACT FROM AUTHOR]

This review reports a discussion involving sources, adverse effects, and quantification of emerging contaminants that have polluted the environment, such as chemical elements employed in medicine (antimony, barium, and gadolinium), microplastics in water bodies, in addition to pharmaceutical, illicit drugs, and their metabolites in wastewater and sewage sludge. It also addresses the pollution caused by emerging contaminants in urban areas, such as gas stations and hairdressing salons. The main analytical methods recommended for determining all these contaminants are briefly reported. [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]

AbstractTo realize the safe disposal of solid waste containing heavy metals, sewage sludge jointly with slag and metakaolin was used to prepare alkali-activated materials (AAMs), and the effect mechanism of polycarboxylate acid superplasticizer (PCE), naphthalene superplasticizer (NS) and aliphatic superplasticizer (AS) in AAMs were studied. The results showed that both the fluidity and strength of AAMs decreased with the addition of sludge. For the NaOH + Na2SiO3 activated mortar specimen, the incorporation of sludge can reduce their fluidity and strength from 206 mm and 80.25 MPa to 193 mm and 42.43 MPa, respectively. However, the addition of superplasticizers into sludge-containing AAMs leads to a reduction of 3–9% of the fluidity. Interestingly, it can enhance the strength of the AAMs, especially the NS and AS, which increase the strength by approximately 25%. This is attributed to the increase of particle dispersion by superplasticizers. However, the free water released in the process is reabsorbed by the sludge, which increases the local alkali concentration and promotes the activation of the activity. The dispersed sludge particles can play the role of physical filling, making the structure denser. HIGHLIGHTSSludge is adverse effects on both the fluidity and strength of alkali-activated materials (AAMs).The addition of superplasticizers (SPs) increases the strength of AAM with sludge.SPs do not affect improving the fluidity of AAMs with sludge, even slightly bad.The dispersion effect of SPs on the sludge is beneficial to promote its activity in AAMs.Sludge is adverse effects on both the fluidity and strength of alkali-activated materials (AAMs).The addition of superplasticizers (SPs) increases the strength of AAM with sludge.SPs do not affect improving the fluidity of AAMs with sludge, even slightly bad.The dispersion effect of SPs on the sludge is beneficial to promote its activity in AAMs. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) presents a promising avenue for efficiently reducing sewage sludge and generating renewable energy. The success of AD systems largely relies upon the microbial community composition, which is associated with various process parameters. This review aims to investigate the correlations among the microbiota abundances, digestion performances, and process parameters based on 233 datasets in 69 publications. Statistical analysis of the datasets uncovers significant correlations between process parameters with dominant bacterial phyla and archaeal genera. The evolution of microbial relative abundance (RA) reveals that Chloroflexi are positively correlated with Actinobacteria, Spirochaetes, and Synergistetes, while Firmicutes exhibit negative correlations with Proteobacteria, Chloroflexi, and Spirochaetes. Methanosarcina have negative correlations with Methanothrix, Methanobacterium, and Methanomassiliicoccus. Bacteria and archaea exhibit potential competitive (between syntrophic acetate-oxidizing bacteria and acetoclastic archaea) and syntrophic (between hydrogen-producing bacteria and hydrogenotrophic archaea) relationships. Furthermore, the volatile solids reduction and methane yield are significantly correlated with microbiota RAs and the ratio of Bacteroidetes and Firmicutes. This review sheds light on microbial interactions and thus AD performance by establishing the correlations between process parameters and microbiota composition. Future research directions should emphasize the significance of rare taxa, the necessity for experimental validation, and the potential of advanced modeling approaches to optimize sludge AD systems. [ABSTRACT FROM AUTHOR]

Soil application of treated sewage sludge is considered a beneficial management option for agriculture and environment. Sludge treated with clay minerals or biochar was evaluated as soil amendment, in comparison with limed or untreated sludge. Bentonite, vermiculite, biochar or lime was added to dewatered sewage sludge at 0 and 15% rates, in three replications and air-dried. Then, the treated and untreated sludge were added to two soils, one acid and one alkaline, at 0 (control), 1 and 3% rates, in three replications. The results showed that the pH of acid soil significantly increased compared to control upon addition of treated and untreated sludge at both rates, but remained acidic (<6.0) in all cases except for limed sludge. Upon addition of 3% treated or untreated sludge to both soils, organic carbon (OC) significantly increased compared to control. The same stands for soil available ammonium nitrogen (NH4-N), phosphorus (P), potassium (K), copper (Cu), zinc (Zn) and boron (B) for both soils and rates. Soil total heavy metals, which regulate sludge's agronomic use, were below the legislative limits. However, the 3% addition rate of all kinds of sludge, especially of untreated, to both soils increased the electrical conductivity of saturation extract (ECse >2 dS m−1) at unacceptable levels for sensitive crops and available P, B and Zn 2–3, 2–4 and 6–12 times above the initial, respectively. Consequently, sewage sludge treated with bentonite, vermiculite or biochar could be used as a soil amendment but at rates lower than 3% (≈120 Mg ha−1). [ABSTRACT FROM AUTHOR]

The demand for food is increasing and the use of soil organic amendments in agricultural management practices has been instructed to increase crop yield and reduce dependence on synthetic inorganic fertilizers at low cost to limited resource farmers. However, the effect of organic amendments on the quality and nutritional composition of edible plants has received little attention. Locally available organic amendments (sewage sludge SS, chicken manure CM, cow manure Cow, vermicompost Vermi, and biochar Bio) were chosen to test their impact on field-grown sweet potato, Ipomoea batatas L. yield, root quality, and root nutritional composition. The results indicated that utilizing Cow manure in growing sweet potatoes significantly promoted root yield and root nutritional composition. Cow treatment produced the greatest number of roots compared to Bio, CM, SS, and the control treatments. The results also revealed that the concentrations of vitamin C (260. 3 µg g−1), β-carotene (45.4 µg g−1), soluble sugars (16.7 mg g−1), and total phenols (196.3 3 µg g−1 fresh roots) were greater in the roots of plants grown in Cow compared to the roots of the control treatment. The results indicated the low impact of biochar whereas Cow is recommended for enhancing sweet potato yield and nutritional composition. [ABSTRACT FROM AUTHOR]

This paper highlights an innovative approach to address the environmental challenges associated with waste management and construction materials. The study presents a new technique for utilising treated sewage sludge in the production of eco-friendly geopolymer mortar. Sewage sludge is a byproduct generated from wastewater treatment plants that poses significant environmental issues due to its disposal problems. Geopolymer mortar, on the other hand, is a sustainable construction material that can be produced by activating industrial waste materials, such as fly ash, using alkaline activators. By integrating machine learning algorithms and data visualisation techniques, this study optimises the mix parameters of geopolymer mortar while simultaneously reducing the negative impact of sewage sludge disposal. The experimental results show that sewage sludge ash can replace fly ash and fine aggregate in 1:3 geopolymer mortar by up to 30% and 20%, respectively, without any toxic or heavy metal residues. The compressive and flexural strength of the sludge-based mortar were comparable to ordinary geopolymer mortar, while water absorption and drying shrinkage were similar to control specimens. This research offers a unique solution to promote sustainability in waste management and construction industry by utilising waste materials, including fly ash and treated sewage sludge, for geopolymer production. [ABSTRACT FROM AUTHOR]

Global mines of phosphates, which are a main source for the manufacturing of phosphorus (P)-fertilizers, are running out. To solve this problem, the recovery of P by struvite (NH4MgPO4·6H2O) precipitation as a slow-release P-fertilizer (SRPF) has been a growing interest of recent research. This study aimed to assess the effect of struvite/biochar composites as SRPFs on the growth yield, nutrient uptake responses of maize in two soils (with different amounts of calcium carbonate equivalent), and calculation of P use efficiency indices. The greenhouse experiment was designed with six P fertilizer treatments, i.e. triple super-phosphate (TSP), four types of struvite/biochar composites (S/G0, S/G25, S/G50, and S/G75), and control (no P fertilizer applied) with three replication. Results showed that struvite/biochar composite with high amounts of biochar i.e. S/G75 is the best treatment for improving biomass's of maize (63 and 39%), plant height (25 and 16%), SPAD value (31 and 26%) compared to control and TSP in soil-1 with the low amount of calcium carbonate equivalent, respectively. Applying S/G75, S/G50, S/G25, and S/G0 composites, and TSP concentration of P increased by 2, 1.85, 1.76, 1.73, and 1.34 times over control in soils, respectively. Using of composites significantly influenced P uptake, and recovery efficiency of P by plants, while the S/G75 composite was showed superior to other P-fertilizers. Overall, the struvite/biochar composites showed great potential as efficient SRPF for enhanced maize growth, and the presence of biochar in struvite composite with high amount (S/G75) increased the efficiency of fertilization in calcareous soil. [ABSTRACT FROM AUTHOR]

Sewage sludge is a promising fertiliser for sweet sorghum growing on marginal land. We investigate the effects of different doses of sludge on the characteristics of chlorophyll fluorescence. Two types of sewage sludge were used: without flocculant and treated with flocculant. Sludge application helps to reduce the amount of inactive chlorophyll in the reaction centres, increases photosynthetic activity, and reduces the sensitivity of the photosynthetic apparatus to adverse environmental factors. Flocculated sludge had the more beneficial effect, particularly at the early stages of development; the optimal dose was 40-60t/ha. [ABSTRACT FROM AUTHOR]

Miscanthus yields well on raw subsoil where organic matter and nutrients are supplied by sewage sludge; the yield is directly dependent on the amount of sludge applied; the greatest productivity (12.9t/ha) was achieved by adding 60t/ha of flocculated sludge. Among the macronutrients, nitrogen is most actively absorbed, the intensity of biomass accumulation of phosphorus and potassium is much lower; other essential elements can be ranked as Fe → Zn → Mn → Cu. Cobalt, nickel and cadmium do not accumulate in biomass but chromium does. The introduction of sewage sludge affects the thermal characteristics of the miscanthus biomass. The proportion of incombustible residue increases when sludge is applied at high doses. Application of 20t/ha flocculated sludge appears to be optimal for ensuring environmental safety and suitability as a fuel. [ABSTRACT FROM AUTHOR]

The volume of sewage sludge generated continues to increase, leading to harmful secondary pollution and highlighting the pressing need for sewage sludge reduction. Sewage sludge drying is a well-established method for treating municipal sewage sludge. This study systematically reviews the latest research on the formation and control of gaseous pollutants during sewage sludge thermal drying. First, this paper comprehensively introduces sewage sludge drying, covering its principles, heat sources, and the inevitable generation of waste gas during the drying process of sewage sludge rich in organic matter. Subsequently, it summarizes the methods for detecting sewage sludge drying exhaust gas and outlines the emission characteristics of such exhaust gas. The three main types of dry exhaust gases discussed include volatile nitrogen-containing compounds, represented by ammonia (NH3); volatile sulfur-containing compounds, represented by hydrogen sulfide (H2S); and the benzene series (BTEX). Finally, based on current technical capabilities, this paper proposes two methods for controlling pollution from sewage sludge drying exhaust gas: suppressing pollutant release during the drying process and treating exhaust gas at the end of drying. Inhibition of pollutant release during the drying process primarily involves reducing the types and quantities of pollutants released by adjusting the sewage sludge drying temperature and time, employing sewage sludge conditioning, and implementing others. Drying back-end exhaust gas treatment removes contaminants from the drying exhaust gas through processes like condensation, adsorption, absorption, biodegradation and other methods. This work offers a fresh perspective on understanding how various factors in the sewage sludge drying process influence the characteristics of dried exhaust gas emissions and the overall control of sewage sludge exhaust gas emissions. [ABSTRACT FROM AUTHOR]

Convective sewage sludge drying is often carried out in belt dryers, where the air flow is directed through the layer. In such a configuration, drying air properties, as well as the structure of the layer and its homogeneity are key factors affecting the drying process. In the present work, these factors were investigated using laboratory experiments on relatively large sludge samples with a mass of several kilograms. Drying was performed at relatively low drying air parameters (time-averaged temperatures of 65 to 80 °C and velocities of 0.44 to 0.78 m/s). The inhomogeneity of the sludge layer drying was observed by measuring the layer surface temperature with an IR camera. The reduction in layer thickness during drying was measured using an optical laser-based method. Analysis of the data included regression and fitting of the data to parametric drying curves, with the modified Nadhari drying law providing the best fit. The standard deviation of the layer surface thermograms (S) was used as a parameter that accounted for the layer homogeneity and consequently drying evenness. Higher values of S corresponded to lower drying rates and consequently longer drying times, highlighting the importance of producing layers with a homogenous structure. The measured layer thickness reduction rate indicated the overall drying intensity almost from the beginning of drying. Both the surface temperature unevenness and the layer height reduction measurement methods were demonstrated as viable approaches for real-time monitoring of the drying process with potential for application in real-scale dryers. [ABSTRACT FROM AUTHOR]

The stabilized sewage sludge, biosolid, has been widely investigated but despite numerous studies few ones have monitored the retention potential of metal ions of this material. This study aimed to investigate the zinc retention in biosolid-soil mixtures with different biosolid contents. The potential of zinc retention was evaluated using a physical model in a geotechnical centrifuge. The physical model was designed to represent a waste barrier of 3.75 m and to simulate a 1-year zinc percolation through the biosolid-soil layer. During the percolation, the zinc effluent was collected to monitoring its concentration over the time. Results show that the addition of 50% of biosolid in the soil, among other investigated proportions provided reductions up to 95% of the initial zinc concentration, considering a 300 days zinc percolation, while the natural soil, for the same period, provided reduction of 33%. The results clearly demonstrate that the incorporation of biosolid in the soil improved the zinc retention capacity. Chemical analysis suggested that the retention behavior of the biosolid is associated with the presence of organic matter and the pH value. The results are promising regarding the use of biosolid-soil mixtures in waste landfill barriers. [ABSTRACT FROM AUTHOR]

Nitrohumic acids (NHAs) are considered as promising slow-release N fertilizers. In this study, NHA was produced from six organic feedstocks, including coal, leonardite, municipal waste compost, sewage sludge, and apple and beech biochars via nitration using nitric acid. The nitration process was conducted in two ways: (i) after humic acid (HA) extraction (NHAD), and (ii) before HA extraction (NHAID). The prepared NHAs were then characterized using FT-IR and CHNS analysis. Additionally, N mineralization of NHAs was investigated in a sandy loam soil sample. The FT-IR spectra showed that both methods of nitration loaded nitro (NO2) groups into the HA structure. However, the CHNS analysis indicated the highest rate of N increase for NHAD (106%) and NHAID (113%) extracted from leonardite. Moreover, on average, the total acidity and carboxylic groups of the HAs increased by 7.5% and 14.5% after the nitration processes, respectively. The highest extraction yields of NHAD (26.1%) and NHAID (42.1%) were also obtained from leonardite. Although the extraction yield of NHAID was on average two times higher than that of NHAD, NHAD indicated a higher soil N availability (1.4 times). We concluded that the NHAD extracted from leonardite could be considered as an alternative slow-release N fertilizer. [ABSTRACT FROM AUTHOR]

The atomization of sewage sludge is a key step in its drying process. This study conducts an industrial-scale experimental study to investigate the performance of a self-developed internal-mixing air-blast nozzle for atomizing sewage sludge. The size of atomized droplets is calculated using image processing technology. Using the specific size and characteristic size of the droplets, the droplet distribution and the droplet motion behavior in spray field are investigated at various air-to-liquid mass flow rate ratio (ALR). The larger the ALR, the smaller the atomization droplets. By installing outlet diffusers and impaction pins, the atomization angle can be increased and the distribution of droplets in the spray field can be improved. The outlet diffuser with an outlet angle of 90° and the square impaction pin exhibit optimal effect. Experiments with real scale and industrial grade have a significant reference value for industrial applications of sludge atomization. [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]

The acidification and loss of nutrients and organic matter in tropical soils are indicators of chemical degradation. In such a scenario, alkalized sewage sludge (SS) for fertilization and reclamation of soils is a promising alternative. Here, we evaluate the impact of SS on soil fertility, sugarcane nutrition and yield in three successive crops. The treatments consisted of five rates of SS (0, 10, 20, 30, and 40 t ha−1) and one treatment with mineral fertilizers. The soil characteristics, plant nutrition, and sugarcane yield were assessed. The results showed that SS increased the pH and the sum of bases, reducing exchangeable aluminum and improving chemical soil conditions. SS also increased soil organic matter (SOM), but SOM decreased over time. Likewise, the N and P contents in the soil were decreased with the successive crops. Sugarcane yield increased following SS rates and reduced with each crop cycle. The yields for plant cane, first ratoon, and second ratoon were 174, 94, and 74 t ha−1 at a rate of 40 t ha−1; these values were 75, 19, and 61% higher, respectively, than the mineral fertilization. SS can aid the reclamation of the chemically degraded soil, contributing to sugarcane nutrition and increased yields. [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]

Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system. [ABSTRACT FROM AUTHOR]

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. [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]

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]

The widespread presence of microplastics (MPs) in water raises serious concerns on a global scale due to the negative effects on human health and ecosystems. Wastewater and sludge from preliminary plants of recycled plastic pellets are a significant continuous source of MP discharged into the environment. Wastewater and sludge samples were collected from three plastic recycling plants and analyzed for MPs (size from 0.15–5 mm). The average rate of MP emission was approximately 5.8–6.6% of the total investigations. The MP in water ranged from 14.3410 to 19.3395 g/l, of which 40% with size 2–5 mm, 32% (1–2 mm), 5% (0.5–1 mm), 14% (0.15–0.5 mm), and 9% with size less than 0.15 mm in average. MP in sludge varied from 472.2031 to 644.7620 g/kg, of which, 37% with size 2–5 mm, 24% (1–2 mm), 9% (0.5–1 mm), 12% (0.15–0.5 mm) and 18% less than 0.15 mm. In average, 2,695 particles/l and 287,600 particles/kg of MP size 0.15–5 mm was found in wastewater and sludge, which may have a potential risk to aquatic fauna and humans. Therefore, control microplastic emission from those sources will contribute significantly to reducing microplastics entering the surrounding environment. [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]

Real-time measurement of sewage sludge moisture content renders it possible to optimize the consumption of auxiliary fuel and the thermal treatment. Thus, we explored whether a dielectric soil moisture sensor could be used to measure real-time changes in sludge moisture content. This was possible with the aid of a unified calibration curve. The explanatory variable was the third-order sensor output voltage. The calibration curve well-fitted the data; the mean measurement error was 6.14 wt.%. The use of individual calibration curves for each sludge batch reduced the mean measurement error to 3.09 wt.%. The mean measurement error improves when multiple sensors are simultaneously used. The sensor operates very well when the moisture content is low; the results are minimally affected by the bulk density and Fe level. Considering feed-back to the process, it is ideal to measure sludge moisture content near the outlet of the thermal treatment. [ABSTRACT FROM AUTHOR]

The humic compost obtained from the treatment of tobacco from smuggled cigarettes (SCT) and industrial sewage sludge (ISS) was evaluated as adsorbent for Cd (II) in aqueous solution, for possible decontamination of water resources. Optimum conditions were found at pH 5 and a 3 g/L adsorbent concentration, which presented 92% Cd (II) removal and maximum adsorption capacity of 28.546mg/g. The pseudo-second-order kinetic model presented the best fit, pointing 120 min as the time needed to attain a steady state. FTIR and EDX results suggest the formation of coordinated Cd (II) bonds by functional groups between the compost and the solution. The results obtained in real samples showed that, even under different environmental conditions, the Cd (II) adsorption varied between 80.05 and 91.61%. The results indicated that the compost evaluated can be used for remediation of Cd (II)-contaminated water resources. [ABSTRACT FROM AUTHOR]

The occurrence of antibiotic-resistant bacteria (ARB) in wastewater treatment plants (WWTPs) has become an occupational and environmental concern. WWTPs are engineered systems that treat wastewater to meet public health standards before release into the environment. The residuals, as either effluent or solids, are then discharged or beneficially recycled into the environment. Since these wastes contain a diverse array of microorganisms, some of which are resistant to commonly used antibiotics, there is a potential for these organisms to spread in the environment via residual recycling and effluent discharge. Human infections with ARB are increasing, and it is not well known how the interaction between humans and the environment plays a role in this process. WWTP workers, who are on the front lines, may come into direct contact with materials containing these microbes. This study aimed to determine the number of ARB present in both air and sewage sludges in a WWTP using nonselective media supplemented with two antibiotics (ciprofloxacin and azithromycin). The densities of total heterotrophic bacteria, ciprofloxacin-resistant bacteria, and azithromycin-resistant bacteria were 7.82 × 105 − 4.7 × 109, 7.87 × 103 − 1.05 × 108, and 2.27 × 105 − 1.16 × 109 CFU/g, respectively. The prevalence [(concentration on medium with antibiotics/concentration on medium without antibiotics) × 100] of ciprofloxacin-resistant bacteria in treated sludge was twice as low as in digested sludge and approximately three times lower than in raw sludge. For azithromycin, the prevalence of resistant bacteria in treated sludge was about the same in digested and nearly twice lower than in raw sludge. Despite a marked reduction in the mean prevalence of resistant bacteria in dewatered treated sludge for both antibiotics, these differences were not significant. The highest prevalence of antibiotic resistance was observed for azithromycin. Similarly, the prevalence of airborne azithromycin-resistant bacteria inside the belt filter press room (BFPR) was nearly seven times higher than the prevalence of airborne ciprofloxacin-resistant bacteria. These concentrations of ARB were not negligible and may represent an exposure pathway for some workers in WWTPs. [ABSTRACT FROM AUTHOR]

Boilers are combustion devices that provide process heat and are integral to many industrial facilities. Historically, outside of the pulp and paper industry, most boilers burned fossil fuels, although interest in decarbonization has been leading to an increased use of renewable fuels in boilers. These boilers, including those in the biorefineries, are often large sources of air pollutant emissions, and the characterization of these emissions is critical to obtaining air permits and ensuring protection of the surrounding air quality. Several industrial boilers and new biorefineries allow utilization of biomass-derived fuels (e.g. wastewater sludge, lignin, etc.) produced during their operation as a fuel for the boiler to meet process energy needs. However, there is limited empirical data on emission factors for the burning of unconventional fuels, such as solid-gas mixtures containing biomass residues. To fill this gap, we carry out a comprehensive data survey, collecting information on emission factors for boilers burning either a single or a mixture of solid and gaseous biomass-derived fuels. We review multiple hard-to-obtain and unconventional data sources, such as air permit applications, stack test data, and industry-sponsored data collection efforts, to compile emission factors for biomass-derived fuels. We then compare this data with wood residue emission factors from the U.S. Environmental Protection Agency's AP-42 emission factor database. Our results indicate that the emission factors for boilers burning unconventional fuels vary widely depending on the fuel composition, boiler type, and fuel characteristics. Overall, we find that median emission factors of selected biomass-derived fuels are typically lower than those of wood residue boilers in AP-42. The information collected herein could be useful to permitting agencies and industries utilizing boilers who may want to reduce the carbon impact of their facilities by combusting biomass-derived wastes for process energy needs, for more accurate emission estimation for permitting. Implications: Emission factors are often used for air permitting, specifically for emission estimation purposes. This study carries out a comprehensive data survey of emission factors burning unconventional biomass-derived fuels from underutilized sources such as air permits, stack test data, and industry-led efforts, and compare the results to EPA's wood residue emission factor database. The results from this study can be used can be used by multiple stakeholders such as air permitting agencies, industries burning biomass-derived fuels, and biorefineries, that utilize more advanced boiler technologies. The findings can help mitigate risks to industry owners and operators and helps to avoid delays in obtaining the required air permits that arise due to inappropriate emission estimates in permit applications. [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]

The aim of the study was to evaluate the content, uptake, and utilization of Al, Mn, Fe, Co, and Mo from municipal sewage sludge by the reed canary grass (RCG) and the giant miscanthus (MG). The impact of sewage sludge on the mass ratios between microelements contained in the plant biomass was analyzed as well. The long-term field experiment consisted in application of four levels of fertilization with sewage sludge: 10, 20, 40, and 60 Mg DM·ha−1. A non-fertilized control object (0 Mg DM·ha−1) was used as well. The miscanthus biomass was characterized by higher content of Al and Mn, whereas higher levels of Fe, Co, and Mo were determined in the reed canary grass biomass. As in the case of the element content, the giant miscanthus was characterized by highest level of Al and Mn uptake, while the highest uptake of Fe, Co, and Mo was exhibited by the reed canary grass. In the group of the analyzed microelements, the giant miscanthus showed the highest the recovery of Mo (47%) followed by Mn (39%), Fe (35%), and Co (15%), and the lowest uptake was determined in the case of Al (5%). In addition to the use of their biomass for the production of renewable energy, energy crops (reed canary grass, giant miscanthus) can be used to recover microelements from municipal sewage sludge. Energy crop biomass can therefore be a potential source of microelements in animal feed. Attention was paid to the mass ratios of Fe:Mn, Fe:Al, Fe:Co, Fe:Mo, Mn:Al, Mn:Co, Mn:Mo, and Co:Mo in the biomass yield of the species used. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic that may degrade human health. Organic solvents are commonly used for the extraction of PAHs from solid samples and the analytes are determined chromatographically. This study describes the ultra-high performance iquid chromatography-diode array detection (UHPLC-DAD) determination of PAHs in sewage sludge and compost used as agricultural fertilizer. The PAHS may be transmitted to humans through the food chain. Analytes in the fertilizer were quantitatively extracted into the organic phase in water-dichloromethane-acetonitrile and determined liquid chromatographically. 16 PAHs were selectively extracted in a single clean-up step. For method development, the type and volume of organic solvent, pH of the water, and ultrasonic extraction time were optimized. For method validation, analytical figures of merit were obtained for the linearity, limit of detection (LOD), limit of quantification (LOQ), stability, intra- and inter-day precision, and accuracy. The developed and validated method was used for PAH determination in the fertilizers. Sample analyses were performed with 89–102% recovery values and 0.7–4.1% relative standard deviations. [ABSTRACT FROM AUTHOR]

Banana crops require large amounts of fertilizers to maintain nutrients levels and achieve satisfactory yields. The use of biological fertilizers combined with organic waste is an efficient and sustainable option for agricultural production. Therefore, this study evaluated the use of a biological fertilizer combined with sewage sludge to make nutrients available in banana crops. We conducted a field experiment in a randomized block design, with four blocks and five repetitions per block in a subdivided plot scheme. The experiment lasted two years. We performed the soil and plant chemical analysis and we also assessed the plant biometric data. The lowest dose of biological fertilizer combined with sewage sludge increased P content in the soil in the first and second collections, but decreased in the third collection. The highest nutrient levels in the soil and plant were attained when biological fertilizer was applied with sewage sludge; however, high Ca content caused an imbalance of exchangeable bases in the soil solution. [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]

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]

Oxygen consumption (OC) for the combustion of dried sewage sludge was determined by an equipped YSZ oxygen sensor. Probably due to the good combustion of the sludge, it was not affected by the temperature and oxygen concentration. However, it increased directly proportional to the rise of sludge amount. The mole ratio of OC/TOC agreed well with each entry and almost equalled 1, which indicated the feasibility of directly using OC to assess the organic burden in the wastes. As a result, OC in this study can be potentially applied to replace the chemical oxygen demand (COD) for the evaluation of samples involving solid-containing wastes (e.g., sewage sludge). Additionally, the easy determination of OC also promotes its advantage over COD because of the unavoidable drawbacks for the conventional COD determination. [ABSTRACT FROM AUTHOR]

The spreading of sewage sludge from wastewater treatment plants and various industries arouses the growing interest due to the contamination by trace elements. Sludges were collected from one sewage treatment plant and two industries in Dhaka City, Bangladesh to assess physicochemical parameters and total and fraction content of trace elements like Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn in sludges. We evaluated the bioavailability of theses metals by determining their speciation by sequential extraction, each metal being distributed among five fractions: exchangeable fraction, bound to carbonate fraction, Fe-Mn oxide bound fraction, organic matter bound fraction and residual fractions. We found that all the analyzed sludges had satisfactory properties from an agronomic quality point of view. The average concentration (mg/kg) of trace metals in sludge samples were in the following decreasing order Fe (12807) > Cr (200) > Mn (158) > Zn (132) > Cu (68.2) > Ni (42.5) > Pb (36.4) > As (35.1) > Cd (3.7). The results of the sequential extraction showed that Cr, Ni, Cu, Fe and Mn were largely associated with the residual fraction where As, Cd and Pb was dominantly associated with the exchangeable and carbonate bound fractions and Zn showed a considerable proportion in carbonate bound fraction. These results showed that regulations must take into account the bioavailability with regard to the characteristics of the agricultural soils on which sludge will be spread. [ABSTRACT FROM AUTHOR]

Sewage sludge is an inevitable by-product of biological wastewater treatment process and contains various toxic substances such as pathogens, heavy metals and organic contaminants, which may cause serious pollution risks without appropriate disposals. Dewatering and drying technology play significant roles in minimizing sludge volume, facilitating transportation, increasing calorific value and reducing the leachate production in landfill sites. Various new technologies are emerging and existing ones are always evolving because of sharp growth of sewage sludge in the last decade. This paper presents a comprehensive review on recent advances in related to dewatering and drying of sewage sludge. The influencing factors of sludge dewatering are addressed out firstly. And then the conditioning methods to improve sludge dewatering performance are summarized and compared in terms of applicable occasions, material consumption, energy and environmental impacts etc. The dewatering technology is classified into common, deep and high-dry dewatering based on the degree of moisture content, and the drying method is divided into convective drying, conduction drying, radiation drying and other new drying. The present dewatering and drying technologies are reviewed and compared in order to provide useful guidelines for sludge disposal. The future demands and opportunities for sludge dewatering and drying are pointed out from industrial perspective. [ABSTRACT FROM AUTHOR]

Most sludges are dewatered using mechanical dewatering systems that can bring the weight percentage of the sludge solids up to a maximum of about 40 TS%. This study examined a new way to enhance pressure-filter dewatering by adding ultrasound and electrokinetics. The ultrasound adds a "stripping action" to free up bound water, and the electrokinetics adds a "pumping action" to push the freed-up water out of the sludge. This new enhanced dewatering process specifically targets bio and sewage sludges. The development work reported here, however, makes use of a sludge surrogate to determine (1) how to best optimize the enhanced dewatering process, and (2) just how much more water can be economically removed. The results demonstrated a substantial dewatering improvement to 55 TS%. A follow-up paper will demonstrate how this optimized ultrasound- and electrokinetics-enhanced dewatering process performs with bio and sewage sludges. [ABSTRACT FROM AUTHOR]

The feasibility of using hyperthermophilic biodrying (HB) technology for sewage sludge biodrying was investigated in this study. Compared with conventional biodrying (CB), HB has significantly enhanced water removal rate. It was found that proteins and lipids were degraded rapidly in the early stage of HB, while hemicellulose and cellulose became the dominant source of nutrition for microorganisms after the thermophilic phase. HB degraded more organic matters than CB and expedited the volatile solids (VS) convert to dissolved organic matters (DOM) during the 21-day biodrying. The protease activity of HB increased quickly in the first three days. In addition, the bacterial community structure of HB changed dramatically in the thermophilic phase, and diversity of bacterial community decreased. These results not only indicated that HB was a promising biodrying technology, but also revealed the potential microbial degradation mechanism of organic matters in HB process. [ABSTRACT FROM AUTHOR]

Biological vermicomposting is an economic and eco-friendly method to remove PCBs from contaminated soils. This study aimed to investigate the effects of biological sewage sludge on contaminated soil in the presence of Eisenia fetida earthworms for the removal of PCBs. For this purpose, different mixtures of contaminated soil and biological sludge were prepared at various mixing ratios in sample containers, followed by the addition of earthworms. The degradation period was 80 days. During the degradation process, the PCBs concentrations, C/N ratio, temperature, and number of earthworms were measured. The highest reduction in PCBs (47.4%) was found in vermicompost pilot D at a contaminated soil-to-biological sludge volume ratio of 1:4, where the PCBs concentration decreased from 18 mg/kg to 9.5 mg/kg. In the control pilot D, which was identical to the vermicompost pilot D, but lacked the earthworms, the removal rate was 34%. This means that earthworms have played an effective role in increasing the removal rate. Degradation mainly occurred by microorganisms; the earthworms increased the degradation efficiency by increasing contact between microorganisms and contaminants. Overall, the vermicomposting process, in which biological sewage sludge is used for feeding E. fetida earthworms to reduce the amount of PCBs in contaminated soil, can be introduced as an innovative approach. The present study proposed a practical method to manage soil PCB contamination, using available and cost-effective raw materials that can be used in a large scale in situ. The present results indicated that the use of biological sludge, in the presence of E. fetida earthworms, could reduce highly chlorinated PCB contamination in soils. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A method of waste heat recovery and utilization was explored by incorporating a heat recovery system into an existing industrial-scale sludge drying system with handling capacity of 440 kg dry solid (DS) per hour. The recovered heat was used to preheat sewage sludge (and carrier gas) to lower sludge viscosity and flowing resistance during sludge transportation in pipeline, as well as the heat consumption during drying. 5.3% decrease of heat consumption in drying, 48% decrease of sludge flowing resistance, and 15% decrease of spraying water consumption in spray tower were fulfilled. Theoretical modeling of heating and flowing behavior of sewage sludge in pipeline, and cooling behavior of hot wet air in a type-III spiral plate heat exchanger were also conducted. The results showed that wall slip phenomenon occurred between sludge and inner surface of sludge pipe during sludge flowing process, which had marked influence on sludge preheating in pipeline. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the possibility of reclamation and management of mine dump material in degraded and devastated areas containing hazardous substances. In this study, we focused on the determination of changes in electrical conductivity (EC) coefficients and physicochemical parameters of mine soils for biological reclamation needs. The waste substrate material studied here showed significantly lower EC over time in tests, with a value of 6.54 dS m−1 decreased to 0.54 dS m−1. Increasing mine soil quality index corresponded with an increased concentration of exchangeable calcium ions. The cation ratio of soil structural stability indicator was positively correlated with increasing EC. Estimating the changes in physicochemical parameters of deposited reclamation material and its gradual transformation provides new knowledge that can be used for the management of mine waste for ecological purposes. In this investigation, we showed that technical activities connected with the management of opencast mining, which may involve removal of contamination from exploited areas, purification of exploited ground or pedogenesis process on waste dump, may be evaluated using the above indicators, artificial neural networks and principal component analysis. [ABSTRACT FROM AUTHOR]

Changes in the bioavailability of nitrogen (N) and phosphorus (P) due to biochar have been frequently reported, raising concerns about the management and effectivity of biochar as soil amendment. We investigated the availability of N and P to maize plants cultivated in soil amended with 20 t ha−1 and 30 t ha−1 of biochar from sewage sludge (SSB20, SSB30) and coconut husk (CHB20, CHB30), in a greenhouse experiment. Plant biomass and concentration of N and P in plant tissue and in the rhizosphere and bulk soil were evaluated. All biochar treatments reduced the concentration of NH4+-N by 22–88% in the soil. CHB20, CHB30 and SSB20 increased NO3–N by 17–40% in the bulk soil and reduced it by 21–38% in the rhizosphere, whereas SSB30 increased NO3− -N by 17–25% in both compartments, but decreased plant N and P uptake efficiency. Biochar increased shoot biomass and P availability by 12% and 12–50%, respectively, except the CHB30, which reduced P availability and N and P uptake efficiency. Biochar improved plant growth during the first 60 days of cultivation in the Ultisol, being suitable as soil amendment at lower rate of application. [ABSTRACT FROM AUTHOR]

The existence of risk factors of wastewaters to high organic materials, phenol compound, chlorinated compound and other complex providing a discharge of receptive waters could be serious hazards created for life in the water. In this study activated sludge/trickling filter (AS/TF) two-step integrated with upflow suspended growth denitrification (USGD) processes operation evaluated for inert chemical matter removal to conventional treatment. From the wastewater activated sludge system of Isfahan with trickling filter used to sequentially. The media from polypropylene, 240 m2/m3 specific area, 1.8 m diameter and 6 m height applied to TF tank instal. Half industrial pilot part of this two-step system operated from 90 days with flow minimum equivalent to 3.6 m3/h until reached steady state. From AS/TF effluent used to feed four reactors in batch condition and lab scale. These reactors along with two reactors to glucose substrate and equivalent COD with other reactors performance from 504 h in the aerobic condition and room temperature (23–26°C). Each of which of soluble inert materials,total soluble COD, degradable suspended materials, degradable COD, refractory suspended materials and degradable soluble materials parameters calculated for single activated sludge (SAS), AS/TF and USGD effluent that mg/l reached for SAS 32, 180, 86, 234, 220 and 148 respectively. These parameters calculated for a two-step system 16, 180, 195,359,111 and 164 and the USGD process as 8, 180, 201, 373, 105 and 172 respectively. The calculations showed when AS integrated to TF in compare with when one applies single is capable inert COD removed two times and for USGD removed four times. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) entering into soils via sewage sludge could be posing arresting environmental risks. Photocatalytic remediation has been considered as a powerful tool of degrading PAHs in soils. In the present study, a synthesized nanometer mixed-crystal TiO2 was employed to investigate its effects on PAHs degradation in soils by Ultra Violet (UV).Two typical substances of PAHs widely detected in sewage sludge (phenanthrene and pyrene), were added into soils from farmland to provide polluted soil for a series of simulated experiments. These polluted soil samples were mixed with five different levels of the synthesized TiO2 (0, 1%, 2%, 3%, and 4%, wet weights) and the decreases of PAHs under different conditions were compared. The results showed that among the five treatments, the activities of the synthesized photocatalysts followed the order of 0<1%<2%<4%<3%, and the 3% of TiO2 addition was determined as the optimum condition. Moreover, it was found that the degradation of PAHs could increase with the increasements of H2O2, photon flux, and humic substances in treated soils. Our findings supports the perspective of using nanometer synthesized mixed-crystal TiO2 in the degradation of PAHs in contaminated soils by sewage sludge addition and provides hints on understanding the mechanism of developing photocatalytic remediation in PAHs-contaminated soils. [ABSTRACT FROM AUTHOR]

Barley cultivation in salt-affected mudflat can alleviate the growing domestic barley demand and land use conflict. However, the coincidence of barley growing season and salt accumulation period of mudflat limits barley production despite of some natural tolerance to salt stress of barley plant. Sewage sludge can be used as organic modifier for mudflat amendment. In this study, a field experiment was conducted with one-time different sludge input rates to assess the responses of soil fertility factors, barley growth, and accumulation and uptake of metals in soil and barley plant to sewage sludge addition (SSA). The results showed that SSA improved soil physicochemical properties. The biomass and yield of barley grown in sludge-amended mudflat were elevated and the maximum increments were associated with 250 t ha−1 SSA rate. The concentrations of total and available cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) increased in sludge-amended mudflat soil, and SSA rate was the major factor influencing metal concentrations. Sludge addition increased metal concentrations in barley plant, and metals uptake by barley plant were mainly accumulated in barley root. In summary, barley cultivation with relatively high yield and controllable metals risk in salt-affected mudflat can be achieved under one-time sludge addition even in salt accumulation period. [ABSTRACT FROM AUTHOR]

Soil organic matter has vital role in maintaining important soil functions. Consequently, using sewage sludge as soil organic amendment is considered one of the agricultural practices for improving soil fertility, which is also a safe approach for its disposal. The present research was carried out to analyze the different microbial activities and functional diversity of agricultural soil with regard to sewage sludge application. A laboratory experiment was set up by taking the agricultural soil from Haryana Agricultural University fields and amended with 5, 10, 20, 30 and 50 t ha−1 of sewage sludge. It was observed that soil microbial biomass increased upto 60% and potential activities of dehydrogenase, alkaline phosphatase and urease enzymes increased upto 50–55% with increasing application rates of sewage sludge. In addition the community-level physiological profiling technique (CLPP) based on carbon source utilization was used to determine the microbial functional diversity of soil. The results indicated higher functional diversity of microbial population capable of exploiting different carbon substrates with sewage sludge application. These results are imperative for improving the approach of sewage sludge application to the agricultural soil in consideration of increasing soil fertility with reducing the use of chemical fertilizers. [ABSTRACT FROM AUTHOR]