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This study aims to assess the impact of using different fuels in Egyptian Titan Alexandria Portland Cement Company on emissions and concentrations of pollutants (Total suspended particles (TSP), nitrogen dioxide (NO2‎), and sulfur dioxide (SO2)) and their influence on ambient air quality during the period 2014–2020 using AERMOD dispersion model. The results showed that changing the fuel from natural gas in 2014 to coal mixed with alternative fuels (Tire-Derived Fuel (TDF), Dried Sewage Sludge (DSS), and Refuse Derived Fuels (RDF)) in 2015–2020 caused fluctuating variations in pollutant emissions and concentrations. The highest and lowest maximum concentrations of TSP occurred in 2017 and 2014 respectively, where the TSP is positively correlated with coal, RDF, and DSS and negatively correlated with natural gas, diesel, and TDF. Also, the lowest and highest maximum NO2 concentrations were detected in 2020 and 2016 followed by 2017 respectively, where NO2 is positively correlated with DSS and negatively correlated with TDF and varies with diesel, coal, and RDF. Moreover, the maximum concentrations of SO2 were the lowest in 2018 and highest in 2016 followed by 2017 because of its considerable positive correlation with natural gas and DSS and negative correlation with RDF, TDF, and coal. Generally, it was found that increasing the percentage of TDF and RDF with decreasing the percentage of DSS, diesel, and coal will reduce pollutant emissions and concentrations and enhance ambient air quality. [ABSTRACT FROM AUTHOR]

Due to the large volume of sewage generated every day, there is a high demand for its treatment. The by-product (called sludge) generated after the treatment process has caused problems in terms of its final disposal. Since the typical end off for this waste is landfills, it is mandatory reducing the landfill amount and the risk of soil contamination. The present work explored an adequate final disposal of the sludge as a sustainable alternative. For this purpose, briquettes were produced using dry sludge from the Sewage Treatment Plant of the Minas Gerais (Brazil) Sanitation Company and vegetable oil used to thicken the briquettes. These briquettes were compared to eucalyptus charcoal in terms of their calorific potential, through immediate analysis, since Brazil has a high demand for primary energy, especially in the industrial sphere. The calorific potential of charcoal reached 16.66 MJ/kg, while that of briquette reached 12.94 MJ/kg. However, briquettes had a density much higher than charcoal, so it takes a smaller volume of briquettes to achieve the same burning capacity as a large volume of charcoal. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of various pyrolysis temperatures and application amount on the remediation of Cd–Pb contaminated soil, dried sewage sludge was pyrolyzed at 300 °C (SSB300) and 500 °C (SSB500), and soil incubation experiments were conducted for 60 days with two biochars (SSB300 and SSB500) and three different application amounts (1%, 3%, and 5%). The chemical speciation and bioavailability of Cd and Pb in paddy soil were determined by BCR and DTPA. Results showed that sewage sludge-based biochar (SSB) slightly increased the soil pH, due to the neutral SSB. The specific surface area of SSB500 was increased by 40.06 m2/g compared to SSB300. FTIR showed a decrease in the hydroxyl vibrational peak of SSB500 compared to SSB300; in addition, the intensity of the aliphatic-CH2 peak decreased with increasing pyrolysis temperature, indicating a decrease in non-polar aliphatic functional groups on the surface of SSB. The incubation experiments showed that the addition of 5% SSB500 had the best performance for DTPA-extractable Cd (48 mg.kg−1 to 12.81 mg.kg−1) and Pb (90.23 mg.kg−1 to 15.91 mg.kg−1). And 5% SSB500 amendment more remarkably transformed Cd and Pb from the acid-soluble state to the residual state than other treatments, demonstrating that the high pyrolysis temperature and application amount had great influence for transformation of Cd and Pb. In addition, the microbial community in the soil was significantly changed by 5% SSB500 application. At the phylum level, Chloroflexi is the dominant species, due to its strong tolerance in Cd-contaminated soil. At the genus level, the relative abundance of Thiobacillus and Defluviicoccus increased, which would enhance inorganic ion transport and metabolism functions to promote passivation and stabilization of heavy metals throughout the remediation process. [ABSTRACT FROM AUTHOR]

Improving the dewatering performance of sludge is a necessary advancement for collaborative sludge disposal and energy-efficient utilization in power plants. Herein, the effects of temperature changes and the addition of drying accelerators derived from agricultural and industrial waste on the drying characteristics of sewage sludge (SS) were investigated from the perspectives of drying kinetics and micromorphology. According to the results, the drying time for sludge significantly showed a clear downward trend via medium–low temperature (160 °C) thermal drying, which subsequently reduced the energy input substantially. When the drying temperature was 160 °C, the ideal addition proportions of rice husk (RH), sludge ash (SA), and coal ash (CA) comprised 15%. The addition of SA prominently boosted the drying rate constant of the original sludge by 48%. Additionally, SEM images along with the spectral dimension obtained via fractal theory explicitly clearly demonstrated that SS + SA had more loose pore channels than other mixed samples. This provided a convenient approach to ensure the evaporation and migration of moisture and thereby shorten the drying time effectively. Consequently, the addition of sludge ash as a drying accelerator can promote the deep dewatering of sludge. [ABSTRACT FROM AUTHOR]

The issue of sustainable management of biosolids (excess sludge) from wastewater treatment is an important issue in the entire developed world. Residual sludge disposal costs and environmental impact may be significant, and reducing such costs, as well as the energy consumption for dewatering and drying, is a key issue for safe and sustainable sludge disposal, considering the recent ban of some disposal options, such as landfilling, in many European countries. An alternative to thermal technologies is solar drying (not to be confused with bio-drying, very close to the concept of composting). Solar greenhouse drying technology is characterized by reduced land requirements compared with traditional outdoor drying beds, as well as by low-energy requirements compared with other thermal drying methods. Process operation is cost-efficient, with close to no maintenance, and observed specific evaporation rates up to threefold higher than conventional drying beds. Many applications of this technology exist in Poland, Germany and Austria: more than 10,000 t of wet sludge per year is treated in this way in Germany alone and almost as many (9000 t/year) in Poland. This paper examines current biosolids treatment technologies applicable to small wastewater treatment plants (2000–9999 population equivalents served) and opportunities for possible solids reuse in Poland in view of sustainable circular economy schemes. In particular, a purely solar-driven greenhouse facility for sewage sludge drying was investigated under different conditions (season, temperature, environmental humidity) and possible improvements for its efficiency evaluated. Sludge processed by solar drying could have different final disposal pathways, according to season, in accordance with the prescriptions of the new National Waste Management Plan of Poland. [ABSTRACT FROM AUTHOR]

The present study is aimed at assessing the effectiveness of solar drying process in terms of helminth egg reduction in sewage sludge (SS) generated from an activated sludge wastewater treatment plant (WWTP) in Marrakesh city (Morocco). It is also engaged to highlight a synergic effect of liming (1% CaO) and solar drying on helminth egg reduction. The solar drying process was conducted for 45 days, in summer under a semi-arid climate in a pilot scale polycarbonate-based tunnel (2 m3). Before undergoing solar drying process, data showed an important load of helminth eggs including Ascaris sp., Schistosoma spp., Capillaria spp., Trichuris spp., Ankylostome spp., Toxocara spp., and Taenia spp. in limed sludge (LS) and non-limed sludge (NLS) (15.2 and 17.9 eggs/g, respectively). Ascaris eggs were the most abundant (11.2 and 13.5 eggs/g in LS and NLS, respectively). By the end of the solar drying process, a considerable removal of the total helminth eggs was recorded in LS and NLS (92.8% and 91.6%, respectively). A complete removal of Schistosoma spp., Capillaria spp., Trichuris spp., Toxocara spp. and Taenia spp. was noted in LS and NLS. In the case of Ankylostome spp., data showed a total removal in LS and 81% in NLS; however, the final load is in agreement with the standards (0.4 egg/g). As for Ascaris spp., neither liming nor solar drying process allowed a complete removal (91% and 90% in NLS and LS, respectively) and the final load (1.1 egg/g) does not fulfill the WHO requirements for an agricultural use. Principal component analysis (PCA) demonstrated a negative correlation between dry matter (DM) content (hence temperature) and helminth egg concentration. No significant synergic effect of liming and solar drying process was showed by statistical analysis. This is substantiating that temperature is the key parameter involved in helminth egg removal while undergoing solar drying of SS. [ABSTRACT FROM AUTHOR]

The aim of this study has been to evaluate the effect of sewage sludge and composted sewage sludge and municipal waste on the content of various forms of P in soil. The experiment scheme: C, control; NPK; FYM; DGSS, dried and granulated sewage sludge; CSS, composed sewage sludge; CSSS, composted sewage sludge and straw; CMMW, composted mixed municipal waste; CMGW, composted municipal green waste. The content of bound P was determined in the fractions: F1, easily soluble; F2, exchangeable; F3, organic; F4, carbonate; F5, stable organic-mineral and mineral bonds; and F6, residual. The NPK fertilisation as well as the soil fertilisation with organic substances raised the P-total content and of P bound in the fractions: F3, F4, F5 and F6. The highest amount of phosphorus in the studied soil was in fraction F3 (phosphorus in organic compounds) and the lowest in fraction F1 (phosphorus in the ionic form as H2PO4− and HPO42−). Composted sludge and straw introduced into the soil increased the content of readily soluble P (F1), while the NPK effect was reversed. NPK fertilisation and enhancement of soil organic matter (except CSSS, CMGW) led to a reduction of the P content in F2 fraction. The content of available P determined by the Egner-Riehm method depended on the content of C-organic, P-total and CEC soil. Among the determined phosphorus fractions, the content of available P was most strongly correlated with the content of P bound in the carbonate fraction (F4) and residual fraction (F6) and, less strongly, with the organic phosphorus fraction. [ABSTRACT FROM AUTHOR]

In this work, an efficient and hydrophobic bamboo pulp cellulose-graft-sodium silicate-polyacrylamide (BPC-g-Si-PAM) flocculant was designed and synthesized to improve its flocculation performance as well as the dewatering efficiency of coagulation sludge. The optimal synthesis process of BPC-g-Si-PAM and its optimal flocculation conditions on wastewater treatment were investigated in detail. Compared with unmodified BPC-g-PAM and commercial PAM, hydrophobic BPC-g-Si-PAM flocculant exhibited better flocculation performance with SV30 of 5.8%. Moreover, TSS, COD and turbidity reduction for machining wastewater reached upto 98.1, 86.8 and 97.6%, respectively. Compared with commercial PAM, removal rate increased by 2.69, 7.68 and 2.68%, respectively. And also BPC-g-Si-PAM exhibited higher removal efficiency for ammonia nitrogen (77.7%), total iron (99.3%), total phosphorus (93.6%) and total zinc (96.7%) than PAM. All the results demonstrated that hydrophobic BPC-g-Si-PAM has a potential application prospect in industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

The influences of five typical additives (coal fly ash, lignite, quick lime, potassium permanganate, dry sewage sludge), freeze-thaw pretreatment and temperatures (100-180 °C) on isothermal drying behavior of municipal sewage sludge were evaluated using a thermal analysis technique. The drying kinetics of the samples was addressed based on two falling rate stages. At the same adding dosage of 10%, the average drying rates for sewage sludge blending with coal fly ash, lignite, lime, dry sludge and potassium permanganate increased by 3.57, 2.81, 2.65, 3.05, 4.80% in comparison with the raw sewage sludge. The average drying rates for the sewage sludge after freeze-thaw pretreatment increased by 7.08%. Apparent activation energies for all sludge/additive blends and freeze-thaw sludge sample were less than those of the raw sewage sludge. Apparent activation energies of sludge/lime in two falling rate periods decreased with increasing the lime dosage from 10% up to 30%. Apparent activation energies of freeze-thaw sludge sample in two falling rate periods were the lowest in comparison with all sludge/additive blends. Coal fly ash, lignite, lime, potassium permanganate and back-mixing additives as well as freeze-thaw pretreatment were available for improving the thermal drying kinetics of the sewage sludge. [ABSTRACT FROM AUTHOR]

Previous studies found that thermally dried biosolids contained more mineralisable organic nitrogen (N) than the raw or anaerobically digested (AD) biosolids they were derived from. However, the effect of thermal drying temperature on biosolid N availability is not well understood. This will be of importance for the value of the biosolids when used to fertilise crops. We sourced AD biosolids from a Danish waste water treatment plant (WWTP) and dried it in the laboratory at 70, 130, 190 or 250 °C to >95 % dry matter content. Also, we sourced biosolids from the WWTP dried using its in-house thermal drying process (input temperature 95 °C, thermal fluid circuit temperature 200 °C, 95 % dry matter content). The drying process reduced the ammonium content of the biosolids and reduced it further at higher drying temperatures. These findings were attributed to ammonia volatilisation. The percentage of mineralisable organic N fraction (min-N) in the biosolids, and nitrous oxide (NO) and carbon dioxide (CO) production were analysed 120 days after addition to soil. When incubated at soil field capacity (pF 2), none of the dried biosolids had a greater min-N than the AD biosolids (46.4 %). Min-N was lowest in biosolids dried at higher temperatures (e.g. 19.3 % at 250 °C vs 35.4 % at 70 °C). Considering only the dried biosolids, min-N was greater in WWTP-dried biosolids (50.5 %) than all of the laboratory-dried biosolids with the exception of the 70 °C-dried biosolids. Biosolid carbon mineralisation (CO release) and NO production was also the lowest in treatments of the highest drying temperature, suggesting that this material was more recalcitrant. Overall, thermal drying temperature had a significant influence on N availability from the AD biosolids, but drying did not improve the N availability of these biosolids in any case. [ABSTRACT FROM AUTHOR]

The moisture distribution and thermal drying characteristics of dewatered sludge in anaerobic digestion were investigated by a thermo-gravimetric analyzer (TG) and the isothermal kinetic characteristics during the drying were developed by an unreacted core model. The TG results showed that the bound water was partly converted to the free water with the invariant interstitial water and surface water after anaerobic digestion, which enhanced the drying performance of sludge. The time required for the complete drying of digestate was less than that of the raw sludge in the same temperature. The moisture evaporative efficiency of digestate was related to the vapor diffusion rate of the outer surface, and the drying efficiency of digested sludge cannot be enhanced by increased temperatures. [ABSTRACT FROM AUTHOR]

A lot of energy is required for drying the sewage sludge produced during the wastewater treatment process in China; however, on the other hand, the thermal energy in flue gas from power plants is usually wasted as it discharges into the atmosphere. In this study, a new technique for sludge drying is introduced. The key component of the new technique is equipment of a two-stage drying and granulation that utilizes thermal energy contained in the flue gas from power plants and extends sludge contact time with flue gas during the constant-rate evaporation stage. The primary results of the implementation in the Kangshun sludge treatment plant (daily treatment capacity of 100 tons of wet sludge) show that the new drying technique is very effective economically and environmentally. The water content in the sludge was reduced from 78% to less than 30%. The resulted sludge could be used either to co-incinerate with coal in a circulating fluidized bed or to mix with clay to make better bricks. Besides the saving in the direct heating cost in the sludge drying processes by 80%, the saving in fossil fuel consumption due to reuse of the dried sludge is also significant. As a result of the implementation of the new technique in a sludge treatment plant at the scale of the Kangshun plant, about 16,440 tons of CO emission could also be reduced every year. [ABSTRACT FROM AUTHOR]

The effective control of the odor pollutants of benzene series (BTEX) is critical for cleaner production in the sewage sludge drying process. Based on the determination of BTEX emission and its contents in four types of sludge (dyeing, leather-tanning, paper mill and municipal), its release characteristics are investigated under drying conditions in the lab and their potential effects on exposed individuals are also evaluated. Results show that in the range of 50-300°C, the total BTEX release from the four types of sludge varies from 4.20 to 161.90 μg m, suggesting that the emission rate of BTEX is in control of the drying temperature. The emission rate accelerates significantly after drying temperature exceeds 150°C, whereas only 5.09% of the total emission is collected below 100°C. A significant positive correlation between BTEX emission and its total contents in sludge at different drying temperatures is observed. Therefore, BTEX content of sludge also determines its release. The sludge drying process under 150-300°C conditions would pose a benzene-related carcinogenic risk to exposed individuals, especially to females. Application of low-temperature drying techniques in sludge disposal is necessary to control BTEX emission and thereby reduces the carcinogenic risks. [ABSTRACT FROM AUTHOR]

This paper analyzes dewatered sludge drying using the multifractal theory. The drying rates of cylindrical sludge with equal masses but different cross-sectional diameters was studied, from which multifractal parameters such as partition function and quality exponent were obtained. The parameters acquired were used to calculate the multifractal singularity spectrum and indicate the presence of multifractal characteristics. The smaller cross-sectional diameters of the sludge were found to be non-homogeneous, and required quantitative methods to analyze. [ABSTRACT FROM AUTHOR]

High concentrations of N and P in biosolids are one of the strongest appeals for their agronomic use. However, it is essential to understand the fate of N in soils treated with biosolids for both plant nutrition and managing the environmental risk of NO-N leaching. This work aims to evaluate the risk of nitrate leaching from a sandy Podosol soil and from a clay Ferrosol soil, each one amended at the range 0.5–8.0 dry Mg/ha rates of freshly tertiary sewage sludge, composted sludge, limed sludge, heating-dried sludge and solar-irradiated sludge. Results showed that for similar biosolids application rates NO-N accumulated up to 3 times as much in the Ferrosol than in Podosol soil. However, there was a fixed 20% NO-N loss from the 20 cm amended-Ferrosol topsoil, whilst the N-nitrified expected to leach down from 20 cm amended-Podosol topsoil layer ranged from 42% to 76% of the accumulated NO-N, depending on the biosolid type. After all, NO-N expected to leach from Podosol soil ranged from 0.6 (heating-dried sludge) to 3.9 times (limed sludge) relative to Ferrosol soil at similar biosolid application rates. Nevertheless, the risk of NO-N groundwater contamination caused by biosolids applied at 0.5−8.0 dry Mg/ha rates could be considered very low. [ABSTRACT FROM AUTHOR]