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Per- and poly-fluoroalkyl substances (PFAS) in wastewater solids have resulted in bans on land application of biosolids, causing utilities to explore thermal treatment options.

Wastewater sludge drying and incineration are conventional solids handling processes that are sometimes employed in water resource reclamation facilities. However, these two processes generate byproducts, sludge drying chaff and sludge incinerator ash, which are landfilled without taking advantage of their value. To gain value from these byproducts, a new synergistic catalytic pyrolysis process using chaff and ash was investigated in this study to improve energy production (i.e. generating a high yield pyrolysis gas) and generate useful products. Ash was used as a catalyst to decrease bio-oil that is corrosive and challenging for combustion in standard equipment, while increasing pyrolysis gas yield and energy for easier energy recovery. Ash increased the pyrolysis gas yield by 50% and product energy by nearly two-fold at the highest ash loading. The bio-oil volume was greatly reduced and contained fewer constituents based on GC-MS and GC-FID analyses. The product energy shifted from bio-oil to pyrolysis gas, which is relatively clean and easier for onsite energy recovery. Ca and Fe content in ash likely plays the catalytic role.

The dielectric properties of bismuth-based cubic pyrochlores strongly depend on the environment of the A-site ions, e.g. the Ni2+ ions doped into Bi1.5MgNb1.5O7 (BMN) pyrochlores for tailoring dielectric properties. Both BMN and Bi1.5NiNb1.5O7 (BNN) ceramics exhibit a cubic pyrochlore structure with preferential (222) planes. However, {442} reflections are observed in BNN pyrochlores, revealing an off-center displacement of A and O' ions. The dielectric constant of BNN pyrochlores is lower than that of BMN pyrochlores, besides BNN pyrochlores have a larger dielectric loss (0.002) than BMN pyrochlores (0.0007). Ni-doping results in a loose and flexible structure contributing positively to the dielectric tunability, besides creating a large amount of oxygen vacancies. The higher amount of oxygen vacancies increases the dielectric loss of BNN pyrochlores. However, BNN pyrochlores exhibit enhanced temperature stability, with a temperature coefficient of –57 ppm/oC, which is significantly better than that of BMN pyrochlores (–362 ppm/oC).

Triboelectric generators (TENGs) have been extensively studied as a new energy for low cost and the universally applicable prospect. Meanwhile, perovskites have been applied in TENG and show a good performance in view of high carrier mobility, long life and dielectric properties. The asymmetry structure of the orthogonal phase CsPbBr3 perovskite endows it with ferroelectric property and induces the misalignment of the positive and negative charge centers. Herein, the surface energy of halogen doped inorganic CsPbX3 (X = Cl-, Br-) perovskites are theoretically investigated by density functional theory (DFT) calculation, the crystal polarizability of pristine CsPbBr3 is improved from 0.47 Ry a.u. to 0.52 Ry a.u. (CsPbCl3), indicating the polarizability of CsPbCl3 is higher than CsPbBr3. In addition, the build-in electric field (Ebuild-in) of perovskite materials can be enhanced by the spontaneous polarization and the aligned dipoles in the Ebuild-in could further improve the tribo-electrostatic electric field by retaining more triboelectric surface charges. In the end, CsPbCl3 achieved a power of 3.06 W m-2 compared to the power of 1.34 W m-2 of CsPbBr3. This work focuses on the regulation of crystal planes using spontaneous polarization of perovskite toward achieving a high built-in electric field for enhancing triboelectric surface charge density.

Wastewater resource recovery facilities produce wastewater solids that offer potential for energy recovery. This opinion article provides a perspective on state-of-the-art technologies to recover energy from sludge (unstabilized wastewater residual solids) and biosolids (stabilized wastewater solids meeting criteria for application on land). The production of biodiesel fuel is an emerging technology for energy recovery from sludge, whereas advancements in pretreatment technologies have improved energy recovery from anaerobic digestion of sludge. Incineration is an established technology to recover energy from sludge or biosolids. Gasification, and to a greater extent, pyrolysis are emerging technologies well-suited for energy recovery from biosolids. While gasification produces high-energy gases, pyrolysis has the benefit of producing biochar in addition to pyrolysis gas. Research on the use of pyrolysis liquids, however, must proceed to advance pyrolysis implementation efforts. Future research on improvements to dewatering and drying of sewage sludge and biosolids will help advance all technologies reviewed.

Pyrolysis is a thermochemical decomposition process that can be used to generate pyrolysis gas (py-gas), bio-oil, and biochar as well as energy from biomass. Biomass from agricultural waste and other plant-based materials has been the predominant pyrolysis research focus. Water resource recovery facilities also produce biomass, referred to as wastewater solids, that could be a viable pyrolysis feedstock. Water resource recovery facilities are central collection and production sites for wastewater solids. While the utilization of biochar from a variety of biomass types has been extensively studied, the utilization of wastewater biochars has not been reviewed in detail. This review compares the characteristics of wastewater biochars to more conventional biochars and reviews specific applications of wastewater biochar. Wastewater biochar is a potential candidate to sorb nutrients or organic contaminants from contaminated wastewater streams. While biochar has been used as a beneficial soil amendment for agricultural applications, specific research on wastewater biochar is lacking and represents a critical knowledge gap. Based on the studies reviewed, if biochar is applied to land it will contain less organic micropollutant mass than conventional wastewater solids, and polycyclic aromatic hydrocarbons are not likely to be a concern if pyrolysis is conducted above 700 °C. Wastewater biochar is likely to serve as a better catalyst to convert bio-oil to py-gas than other conventional biochars because of the inherently higher metal (e.g., Ca and Fe) content. The use of wastewater biochar alone as a fuel is also discussed. Finally, an integrated wastewater treatment process that produces and uses wastewater biochar for a variety of food, energy, and water (FEW) applications is proposed.

Bio-oil and pyrolysis gas (py-gas) are two pyrolysis products available for potential energy recovery. Crude bio-oil, however, is typically corrosive and unstable, requiring special combustion equipment or catalytic upgrading to produce drop-in-grade fuel. In contrast, py-gas is readily useable in standard equipment for energy recovery. Previous research revealed that Ca-impregnated biochar catalyst improved bio-oil to py-gas conversion. Biochar produced from paper mill sludge (p-sludge) has very high Ca content. In this study, the catalytic ability of p-sludge biochar was systematically evaluated for the first time in pyrolysis. P-sludge biochar resulted in higher py-gas yield (40 wt% of total pyrolysis products) and py-gas energy (8400 kJ of py-gas per biosolids pyrolyzed) than other biochar catalysts (e.g. wood and corn stover biochars) and mineral catalysts (e.g. calcined dolomite). Under some conditions (e.g. high temperature and catalyst loading), catalysis completely eliminated the nonaqueous phase condensate. A lower catalyst-to-feedstock ratio was required using p-sludge biochar compared to other biochars for similar performance. P-sludge biochar also had a longer catalyst lifetime based on the effectiveness over five reuse cycles. Bio-oil catalyzed by p-sludge biochar contained fewer organic constituents based on GC-MS and GC-FID analyses (e.g. toluene, ethylbenzene, styrene, phenol, cresol, and indole were not identified after catalysis).

Two new processes for synthetic natural gas (SNG) production based on the sorption enhanced steam hydrogasification (SE-SHR) are proposed. Experimental work was conducted on the gasification of coal and biomass feedstocks with a fixed quantity of quicklime as the sorbent. Results showed that SE-SHR can significantly increase H 2 yield beyond the initial H 2 input and minimize CO 2 production. The SE-SHR parametric study was carried out by using lignite as a typical feedstock. By varying hydrogen to carbon molar ratio (H 2 /C) and steam to carbon molar ratio (Steam/C), the product gas composition and yield during SE-SHR and conventional steam hydrogasification (SHR) were obtained. The increase of H 2 /C enhanced the productions of H 2 and CH 4 and decreased the productions of CO and CO 2 . On the other hand, due to the domination of steam gasification reaction, the yields of H 2 , CO and CO 2 were increased with the increase of Steam/C. The new SNG processes include SE-SHR coupled with water gas shift (WGS) and SE-SHR coupled with methanation. The simulation of individual WGS or methanation unit based on the preliminary bench-scale data was conducted using Aspen Plus software to obtain the final SNG composition. Results showed that the SE-SHR-Methanation process results in high CH 4 production with self-sustained H 2 supply and near zero CO 2 emissions. The optimum gasification conditions for this process using lignite were H 2 /C of 1.08 and Steam/C of 2.22. Finally, a preliminary pilot-scale simulation of SE-SHR-Methanation process was conducted based on the predetermined optimum condition to evaluate the overall material and energy balance. It showed that carbon conversion efficiency to CH 4 was as high as 39.8%.

Bismuth based cubic pyrochlore materials have the attractive dielectric properties, especially the dielectric tunable property. The Bi1.5MgNb1.5O7 (BMN) and Bi1.5Mg1-xNixNb1.5O7 (BMN-xNi) (x = 0.1–0.5) ceramics were prepared by solid state reaction method. XPS spectra of probing evidence for displacive disorder in BMN-xNi by compared with pristine BMN, which confirms the presence of two types of oxygen in the structure. The relative Ni content is the fundamental factor affects the disorder degree in the BMN-xNi structure. It demonstrated that Ni2+ ions prior to substitute onto the A-site of BMN-xNi ceramics when x

Municipal solid waste incineration fly ash is directly landfilled after solidification in the industry. The rapid evaluation of contaminant leaching is required before the landfill of fly ash. In order to reduce the time to evaluate the effect of solidification, a set of rapid evaluation method was developed through the determination of characteristic index, heavy metal leaching analysis, principal component analysis, and mathematical model construction. It was found that f-CaO, acid neutralizing capacity, pH and soluble calcium were negatively correlated with heavy metal leaching. The soluble chlorine was positively correlated with heavy metal leaching. The effect of each feature indicators on heavy metal leaching was evaluated using principal component analysis and mathematical analysis software R.3.4.4. Furthermore, R.3.4.4 was used to detect the optimal model and the excess probability formula by stepwise linear regression and logistic regression analysis method. By introducing the measured value of feature indicator into the excess probability formula, the rate of excess-standard of heavy metals leaching can be preliminarily determined. Based on the above ideas, a rapid detection and evaluation system could be developed according to the local leaching standards and the components of fly ash selected locally.

Improving onsite energy generation and recovering value-added products are common goals for sustainable used water reclamation. A new process called autocatalytic pyrolysis was developed at bench scale in our previous work by using biochar produced from the biosolids pyrolysis process itself as the catalyst to enhance energy recovery from wastewater biosolids. The large-scale investigation of this process was used to increase the technical readiness level. A sub-pilot-scale catalytic pyrolytic system was constructed for this scaled-up study. The effects of configuration changes in both pyrolytic and catalytic reactors were investigated as well as the effect of vapor-catalyst contact types (i.e., downstream, in-situ) on product yield and quality. The sub-pilot-scale test with downstream catalysis resulted in higher py-gas yields and lower bio-oil yields when compared to results from a previous batch, bench-scale process. In particular, the py-gas yields increased 2.5-fold and the energy contained in the py-gas approximately quadrupled compared to the control test without autocatalysis. Biochar addition to the feed biosolids before pyrolysis (in-situ catalysis) resulted in increased py-gas production, but the increase was limited. It was expected that using a higher input pyrolyzer with a better mixing condition would further improve the py-gas yield.

The main goals for sustainable water resource recovery include maximizing energy generation, minimizing adverse environmental impacts, and recovering beneficial resources. Wastewater biosolids pyrolysis is a promising technology that could help facilities reach these goals because it produces biochar that is a valuable soil amendment as well as bio-oil and pyrolysis gas (py-gas) that can be used for energy. The raw bio-oil, however, is corrosive; therefore, employing it as fuel is challenging using standard equipment. A novel pyrolysis process using wastewater biosolids-derived biochar (WB-biochar) as a catalyst was investigated to decrease bio-oil and increase py-gas yield for easier energy recovery. WB-biochar catalyst increased the py-gas yield nearly 2-fold, while decreasing bio-oil production. The catalyzed bio-oil also contained fewer constituents based on GC-MS and GC-FID analyses. The energy shifted from bio-oil to py-gas, indicating the potential for easier on-site energy recovery using the relatively clean py-gas. The metals contained in wastewater biosolids played an important role in upgrading pyrolysis products. The Ca and Fe in WB-biochar reduced bio-oil yield and increased py-gas yield. The py-gas energy increase may be especially useful at water resource recovery facilities that already combust anaerobic digester biogas for energy since it may be possible to blend biogas and py-gas for combined use.

The in-situ removal of CO 2 and the increase of the energetic gas yield, including hydrogen and methane, by sorption enhanced steam hydrogasification (SE-SHR) process were investigated. Lignite was used in this study as the feedstock to the steam hydrogasification reaction (SHR) with the addition of calcined dolomite as a sorbent. CO 2 was reduced dramatically with the introduction of the sorbent into the reactor. The production of hydrogen and methane was increased simultaneously. The hydrogen yield was increased by 60% when the calcium oxide to carbon molar ratio was increased to 0.86 as compared to the results without the sorbent. The hydrogen in the product gas was sufficient to maintain a self-sustained supply back to the SHR when the calcium oxide to carbon molar ratio was over 0.29. The performance of the SE-SHR was determined at different temperatures ranging from 650 °C to 800 °C and at different steam to carbon molar ratios. Additionally, the char conversion was also enhanced in all cases with the sorbent introduction. The synthesis gas production using SE-SHR coupled with steam methane reforming was also modeled by Aspen Plus. The simulation results showed that the H 2 /CO ratio of the synthesis gas generated based on SE-SHR process was 6 with higher overall energy efficiency of 74.5%. Summarily, the main findings of this study were that the overall performance of the SE-SHR was substantially improved compared to the conventional operation of the SHR and the quality of synthesis gas produced based on SE-SHR process was more flexible for the downstream processing.

Pyrolysis is a thermal process that converts biosolids into biochar (a soil amendment), py-oil and py-gas, which can be energy sources. The objectives of this research were to determine the product yield of dried biosolids during pyrolysis and the energy requirements of pyrolysis. Bench-scale experiments revealed that temperature increases up to 500 °C substantially decreased the fraction of biochar and increased the fraction of py-oil. Py-gas yield increased above 500 °C. The energy required for pyrolysis was approximately 5-fold less than the energy required to dry biosolids (depending on biosolids moisture content), indicating that, if a utility already uses energy to dry biosolids, then pyrolysis does not require a substantial amount of energy. However, if a utility produces wet biosolids, then implementing pyrolysis may be costly because of the energy required to dry the biosolids. The energy content of py-gas and py-oil was always greater than the energy required for pyrolysis.

With the growing application of sludge incineration, the thermal behavior of heavy metals during this process is increasingly a concern. This work was conducted to determine the speciation evolutio...

In this paper, ferrite process of electroplating sludge and enrichment of copper by hydrothermal reaction was investigated. By the hydrothermal treatment, Zn, Ni, Cu, Cr-bearing electroplating sludge can be transformed into high value-added Ni–Zn–Cr ferrite by adding iron source (FeCl 3 ·6H 2 O) and precipitator. The most optimum reaction conditions were explored: 1.57 g/g dry sludge as the dosage of FeCl 3 ·6H 2 O, pH 8.5 of the slurry adjusted by ammonia, 4 h as the reaction time, and 200 °C as the reaction temperature. Under these conditions, the purer Ni–Zn–Cr ferrite could be prepared, and Cu was extracted to the range from 76 wt% to nearly 84 wt%, when ammonia was selected as the precipitator. Leaching toxicity of heavy metals from Ni–Zn–Cr ferrite prepared with additional iron source and precipitator, was much lower than the regulated limit of Toxicity Characteristic Leaching Procedure (TCLP), indicating that Ni–Zn–Cr ferrite synthesized hydrothermally from electroplating sludge had a better chemical stability. Therefore, the ferrite process by hydrothermal reaction is a feasible method with respect to the reuse and self-purification of electroplating sludge.

This paper investigated the effectiveness of (ground granulated blast furnace slag) GGBFS-added chemically bonded phosphate ceramic (CBPC) matrix on the stabilization/solidification (S/S) of mercury chloride and simulated mercury-bearing light bulbs (SMLB). The results showed that the maximal compressive strength was achieved when 15% and 10% ground GGBFS was added for HgCl(2)-doped and SMLB-doped CBPC matrices, respectively. The S/S performances of GGBFS-added matrices were significantly better than non-additive matrices. As pore size was reduced, the leaching concentration of Hg(2+) from GGBFS-added CBPC matrix could be reduced from 697 microg/L to about 3 microg/L when treating HgCl(2). Meanwhile, the main hydrating product of GGBFS-added matrices was still MgKPO(4).6H(2)O. The improvement of S/S effectiveness was mainly due to physical filling of fine GGBFS particles and microencapsulation of chemical cementing gel.

A newly designed inverted batch reactor equipped with a pressure-driven feeding system was built for investigating the kinetics of syngas during the steam hydrogasification (SHR) of biomass. The system could instantly load the feedstock into the reactor at high temperature and pressure, which simulated the way to transport the feedstock into a hot and pressurized gasifier. Experiments were conducted from 600°C to 700°C. The inverted reactor showed very high heating rate by enhancing the carbon conversion and syngas production. The kinetic study showed that the rates of CH4, CO and CO2 formation during SHR were increased when the gasification temperature went up. SHR had comparatively lower activation energy for CH4 production. The activation energies of CH4, CO and CO2 during SHR were 42.8, 51.8 and 14kJ/mol, respectively.

A composite inorganic polymer coagulant, polyferric aluminum chloride (PFAC) was prepared by using hydrochloric pickle liquor and calcium aluminate as main materials. The optimum conditions for preparing PFAC with the hydrochloric pickle liquor and the calcium aluminate were studied. The coagulation performance of PFAC was investigated by studying the turbidity, COD, total phosphate (TP) and NH3N removal efficiency in municipal sewage treatment. Results indicated that the effective composition, basicity (simplified as B, B = [OH]/(3[FeT +A lT]) × 100%), coagulation performance and stability of PFAC were affected by calcium aluminate dosage, reaction time, reaction temperature and stabilizing agents. The COD and turbidity removal efficiency of PFAC was better than that of PFS and FeCl3, and the TP and NH3-N removal efficiency of PFAC was much better than that of PFS, FeCl3 and PAC. PFAC not only possessed a good coagulation performance, but also had good stability when stored. © 2008 Elsevier B.V. All rights reserved.