Formation Of Reaction Zone Research Articles

Degradation of LaPO4-8YSZ composite thick thermal barrier coatings by molten calcium-magnesium-aluminosilicate

The effect of LaPO4 content on the calcium-magnesium-aluminosilicates (CMAS) corrosion resistance of the plasma-sprayed LaPO4-8YSZ composite coatings at 1250 °C was investigated. The microstructure and corrosion products of the LaPO4-8YSZ composite coatings after CMAS attack was determined by using SEM/TEM/SAED. The results indicated that LaPO4 was segregated at the grain boundaries of the composite coatings and the addition of LaPO4 into 8YSZ coating increased their CMAS reactivity, which led to the formation of planar reaction zone while the CMAS infiltration depth decreased from ∼658 μm to ∼119 μm. The CMAS infiltration depth of the composite coatings firstly increased with LaPO4 addition, reaching its maximum for the composite coating with 5 wt% LaPO4, and then showed a downtrend. For the composite coating with 20 wt% LaPO4, a dense apatite layer formed in the corrosion front, which inhibited CMAS penetration and resulted in the shallowest CMAS infiltration depth among the test samples.

Biomethane production from biogas obtained in wastewater treatment plants: Process optimization and economic analysis

The methanation of the CO2 present in biogas is getting more and more interest, especially if hydrogen is obtained from renewable electricity. The biogas resulting from anaerobic digestion can be separated into CH4- and CO2-rich streams, after which the CO2 goes into the methanation section, though the biogas can also go directly into the reaction section with no separation; both alternatives were studied in this work. The two state-of-the-art methanation reactors, adiabatic and cooled fixed-bed reactors, were considered, with the latter showing a significant advantage through the formation of different reaction zones inside the reactor, allowing a simpler one-reactor approach. In this work, the use of a CH4-selective membrane was also considered to promote CO2 conversion. The results show exactly that, while the cooled reactor with no previous CO2 separation from the biogas had a CO2 conversion of 91.8 %, the adiabatic reactors showed conversions of 59.6 and 67.2 %, resulting in an overall conversion of 93.0 %. In economic terms, the scenarios studied showed negative net present worth values, considering the present conditions in Portugal and a water treatment plant as case-study, thus requiring the government to provide monetary incentives like feed-in tariffs of 0.050 € kWh−1 for the scenarios without membrane and 0.052 € kWh−1 for the scenarios with membrane.

Fluorination Reaction Control by Surface Migration of Atomic Fluorine

Fluorination with atomic fluorine seems to be a promising way to functionalize materials, since such processes occur in a wide temperature range with an activation barrier close to zero. Here we demonstrate the ability to control the fluorination of platinum with atomic fluorine using surface migration (diffusion) of adsorbed fluorine atoms (Fads). A change in the concentration of fluorine atoms in the reaction zone is achieved by a change in the direction and magnitude of the diffusion flux of Fads due to the formation of alternative reaction zones. The occurrence of diffusion fluxes is determined by the area of contact of surfaces with the main and alternative reaction zones, which provide conductivity for Fads. The developed approach made it possible to experimentally establish the achievement of equilibrium in the reaction PtF4(g) + 2F(g) = PtF6(g) and measure the equilibrium constant.

Chemical Modification of Lherzolite Xenoliths Due to Interaction with Host Basanite Melt: Evidence from Tumusun Volcano, Baikal Rift Zone

To investigate the process and chemistry of mineral reaction zone formation, we conducted detailed petrographic observations and chemical analysis of rocks and minerals of spinel lherzolite xenoliths from basanites of Tumusun volcano (Baikal Rift Zone). The reaction zones gradually disappear from contact toward the center of the xenoliths. The influence of basanite melt on major and trace element composition of secondary minerals of reaction zones is notable only at a distance up to 100–200 μm from the contact. At a distance of 0.3–1.0 mm from the contact, the major and trace composition of secondary clinopyroxenes from the orthopyroxene reaction zone indicates their formation from a melt formed by dissolution of orthopyroxene and influenced by the element diffusion from basanite melt. Inside xenoliths, the secondary minerals have Mg# values equal to or higher than Mg# of primary minerals, and secondary clinopyroxenes inherit their depleted or enriched REE pattern from primary pyroxenes. The compositional variations in secondary clinopyroxenes testify melt heterogeneity. Clinopyroxene rims have slightly higher LILE and similar abundances of other trace elements compared to clinopyroxene cores. This is consistent with the model developed from experimental studies: due to the interaction with basanite, incongruent dissolution of orthopyroxene occurs to form a melt which circulates in lherzolite and leads to pyroxenes and spinel dissolution. Diffusion of elements from basanite results in lherzolite enrichment in K, Na, Rb, Ba, La, and Ce, which are incorporated in feldspars and clinopyroxene of reaction zones as well as in feldspar veinlets. Non-dissolved mineral cores are homogenous and similar in major and trace element composition to primary minerals without reaction rims.

Formation of carbon-bearing silicate melts by melt-metacarbonate interaction at convergent plate margins

The incorporation of carbon into slab-derived silicate melts is a vital process that boosts carbon release and transfer at convergent plate margins. The available models mostly suppose the generation of carbonated silicate melts through partial melting of carbon-rich rocks. Here we show that the carbon-bearing silicate melts can also form by the interaction of slab-derived, carbon-free, silicate melts with eclogite-facies metacarbonate rocks in a subduction-collision environment. We examine the marble – reaction zone – migmatite systems from the Sulu ultra-high pressure (UHP) terrane (China). Field, petrological, geochemical, and Sr-O-C isotopic studies demonstrate that carbon-free silicate melts produced by the anatexis of gneisses infiltrate the marbles, leading to the formation of silicate reaction zones around the melt channels and the synchronous release of CO2 at ∼820–860°C. The occurrence and textural characteristics of calcite-bearing leucosomes in the reaction zones indicate an enrichment of CO2 in silicate melts after the melt-marble interaction. Compositional analyses and mapping of carbonates indicate that these carbonated silicate melts contain >0.8–1.6 wt.% CO2, in accordance with the solubility of carbon in silicate melts at similar conditions. In addition to the variation in carbon contents, the interaction causes a decrease in SiO2 (from 72–73 to 58–63 wt.%) and an increase of CaO (from 0.6–0.8 to 3–8 wt.%) contents in the infiltrating melts. Estimation of carbon budget suggests that less than 14% of released carbon was retained in the carbonated rocks in the form of calcite, whereas the rest was removed from the system through the long-distance transport of the melts or other processes.This study presents compelling evidence for the petrological transition from carbon-free to carbon-bearing silicate melts by melt-marble interaction and therefore provides a new mechanism for the enrichment of carbon in slab-derived melts and an important pathway for the massive extraction of carbon from subducted slabs. Addition of CO2 and reduction of SiO2 as the interaction progress results in a lower viscosity and larger buoyancy of the reacted melts compared to the unreacted felsic melts, which facilitates the rapid transport and rising of these carbonated melts and thus helps a more efficient cycling of carbon in Earth's interior.

Fluid‐Mediated Mass Transfer Between Mafic and Ultramafic Rocks in Subduction Zones

AbstractMetasomatic reaction zones between mafic and ultramafic rocks exhumed from subduction zones provide a window into mass‐transfer processes at high pressure. However, accurate interpretation of the rock record requires distinguishing high‐pressure metasomatic processes from inherited oceanic signatures prior to subduction. We integrated constraints from bulk‐rock geochemical compositions and petrophysical properties, mineral chemistry, and thermodynamic modeling to understand the formation of reaction zones between juxtaposed metagabbro and serpentinite as exemplified by the Voltri Massif (Ligurian Alps, Italy). Distinct zones of variably metasomatized metagabbro are dominated by chlorite, amphibole, clinopyroxene, epidote, rutile, ilmenite, and titanite between serpentinite and eclogitic metagabbro. Whereas the precursor serpentinite and oxide gabbro formed and were likely already in contact in an oceanic setting, the reaction zones formed by diffusional Mg‐metasomatism between the two rocks from prograde to peak, to retrograde conditions in a subduction zone. Metasomatism of mafic rocks by Mg‐rich fluids that previously equilibrated with serpentinite could be widespread along the subduction interface, within the subducted slab, and the mantle wedge. Furthermore, the models predict that talc formation by Si‐metasomatism of serpentinite in subduction zones is limited by pressure‐dependent increase in the silica activity buffered by the serpentine‐talc equilibrium. Elevated activities of aqueous Ca and Al species would also favor the formation of chlorite and garnet. Accordingly, unusual conditions or processes would be required to stabilize abundant talc at high P‐T conditions. Alternatively, a different set of mineral assemblages, such as serpentine‐ or chlorite‐rich rocks, may be controlling the coupling‐decoupling transition of the plate interface.

Numerical investigation of particle size distribution, particle transport and deposition in a modified chemical vapor deposition process

Modified chemical vapor deposition (MCVD) process in a rotating tube reactor is an important technology for manufacturing fiber optic preforms, whose performance strongly depends on the uniformity of the deposited particles on the tube wall. In this study, the Eulerian–Eulerian model with Population Balance Model (PBM) is applied to predict particle size distribution (PSD) of SiO2 particles in the reaction zone, and subsequently Discrete Particle Model (DPM) is used to represent typical particles and investigate trajectories and deposition locations of the SiO2 particles. The temperature, reaction components, and particle size distribution along the axial and radial directions within the tube are predicted reasonably. The deposition distances of the particles with size of 10 nm, 200 nm and 10 μm are mostly smaller than 120 mm for the condition with the peak wall temperature of 2000 K. The deposition distance and flight time of the particles increase with the increase of particle size. With increase of the wall temperature, the reaction zone and particle formation zone become larger, which promotes the growth of the SiO2 particles. The competing effects between the thermophoretic force and inertial force caused by the increase of the wall temperature lead to firstly an increase and then a decrease in the deposition distance and flight time of the particles.

Chemical interactions between ZrO2/α-Zr structured Zircaloy-4 and 316 stainless steel-B4C melt at 1300 °C

• During re-heating of pre-oxidized Zircaloy-4 under oxygen starvation, initial ZrO 2 layer was partially dissolved, forming a new α-Zr layer at the external surface. • When pre-oxidized and then re-heated Zircaloy-4 contacted with 316SS-B 4 C melt, the reaction zone consisting of multiple sublayers grew approximately linearly with time. • Due to the presence of external α-Zr layer, pre-oxidized and then re-heated Zircaloy-4 showed no significant improvement in delaying ZrO 2 dissolution and reaction zone formation under the current experimental conditions. To deeply understand chemical interactions among nuclear materials during core meltdown, pre-oxidized Zircaloy-4 was re-heated under oxygen starvation to form thermodynamically stable ZrO 2 /α-Zr structure and then brought into contact with 316SS-B 4 C melt at 1300 °C. During re-heating, initial ZrO 2 layer was partially dissolved due to thermodynamic instability, forming a new α-Zr layer at the external surface. Dissolution of ZrO 2 layer could be linearly fitted with fourth root of re-heating time. When pre-oxidized and then re-heated Zircaloy-4 contacted with 316SS-B 4 C melt, the external α-Zr layer became oxygen-unsaturated and was dissolved first by 316SS-B 4 C melt. Initial ZrO 2 layer was divided into two sublayers from the position where Zr 5 Sn 3 phase was located. Due to direct contact with oxygen-unsaturated α-Zr layer, outer ZrO 2 sublayer became thermodynamically unstable and was dissolved more rapidly than inner sublayer. The reaction zone consisting of multiple sublayers grew approximately linearly with time. Consequently, pre-oxidized and then re-heated Zircaloy-4 showed no significant improvement in delaying ZrO 2 dissolution and reaction zone formation under the current experimental conditions, compared with only pre-oxidized Zircaloy-4.

Preparation and Enhanced Isothermal Oxidation Resistance of a Low Diffusivity NiRePtAl Single-Phase Coating

A low diffusivity NiRePtAl single-phase coating was formed on a Ni3Al-based SC superalloy by electroplating and aluminizing treatments, in which the electroplating consisted of depositing Ni-Re and Pt layer. The isothermal oxidation test of the sample was evaluated at 1100 and 1200 °C; the results indicated that the low diffusivity NiRePtAl single-phase sample promoted the oxidation resistance due to a greater β-NiAl phases-enriched outer layer. The Re-base diffusion barrier could effectively refrain the outward diffusion of Mo. Low diffusivity NiRePtAl single-phase coating has a lower inter-diffusion rate to the superalloy, where the thickness of the secondary reaction zone decreased by 35%. Mechanisms responsible for improved oxidation resistance and decreased extent for the formation of secondary reaction zones are discussed in the present study.

Impact of CVD-synthesis parameters and film thickness on growth rate of single-crystal diamond

The widespread use of CVD-reactors of various constructions and the influence of many factors on the formation of energy-saturated reaction zone has led to the fact of significant difference of technological parameters optimal for each reactor even of one brand. An economically important parameter, in addition to the quality of the obtained single-crystal diamond layer, is the growth rate, which depends on many factors: the flow rate and chemical composition of gases, pressure in the reaction chamber, substrate temperature, the shape of the formed plasma cloud, dimensions and shape of molybdenum substrate holders and et al. This work is devoted to the experimental determination of the single-crystal CVD-diamonds growth rate across various synthesis conditions on Ardis 300. In research, we shown the effect of the thickness of the synthesized diamond layer on the rate of formation of subsequent diamond layers, which is associated with a change in the degree of misorientation between the crystallographic plane (100) and direction [100]. Also, this can be associated with an increase in the roughness of the growing surface, leading to an increase in the specific number of active centers thermodynamically favorable for carbon deposition during the formation of the crystal structure of diamond.

Native copper formation associated with serpentinization in the Cheshmeh-Bid ophiolite massif (Southern Iran)

In the Cheshmeh-Bid district of the Khajeh-Jamali ophiolitic massifs (Southern Iran), mantle peridotites are intruded by abundant pyroxenite dykes. A few of these dykes are remarkable for the occurrence of native copper associated with the development of a metasomatic reaction zone. The dykes are progressively reacted, from their margins towards the center, with an amphibole + antigorite selvage, followed by a centimeter-thick clinopyroxene + antigorite assemblage and, finally, by the native copper-bearing zone consisting of clinopyroxene + chlorite + antigorite. Native Cu occurs along cleavages and partially healed fractures in clinopyroxene, and as massive grains intergrown with antigorite. Copper isotope signatures and thermodynamic calculations show that the main driver for reaction zone formation is Ca-metasomatism. Native copper forms at the expense of chalcocite in the reaction zone. Such a reaction can only occur in reducing conditions, in agreement with the analysis of fluid inclusions composition displaying H2 and CH4. Such fluids presumably originated from the hydration of mantle rocks. The observed reaction zone and native copper mineralization are thus interpreted as the result of Ca-metasomatism during hydrothermal alteration of the oceanic lithosphere. This is consistent with U/Pb dating of titanite, suggesting formation during the Albian when the dykes were exposed on the seafloor in a supra-subduction setting. The source for copper mineralization, as revealed by Cu isotopes, is probably mantle-like.

Effects of preheating temperature and dilution level of oxidizer, fuel composition and strain rate on NO emission characteristics in the syngas moderate or intense low oxygen dilution (MILD) combustion

The aims of present study are to investigate the effective parameters in syngas MILD combustion, including preheating temperature and dilution level of oxidizer, syngas composition and flow structure on NO emission characteristics. For this purpose, counterflow syngas flame simulations are employed at the oxidizer preheating temperatures 1100–2100 K, oxygen mole fractions 2–12%, three syngas mixtures (10%H2/90%CO, 50%H2/50%CO, and 90%H2/10%CO) and the strain rate ranges 25–4000 s−1. Moreover, the effect of methane in the syngas composition as a diluent is studied on NO emission index. For the independence of the results from other parameters, simulations are performed at the equivalence ratio 1 and for the formation of reaction zone on the middle plane of fuel and oxidizer nozzles. The results show that NO emission is minimum at lower H2/CO ratios, oxidizer preheating temperature and O2 mole fraction. NNH mechanism by the reaction NNH + O ⇔ NH + NO plays the most important role in the NO emission in low temperature conditions while the thermal mechanism is responsible for NO formation in high temperature flames. The use of pure H2/CO mixture as fuel indicates that prompt mechanism has the minimum contribution to the NO release from MILD syngas combustion. However, the small values of methane in the syngas composition changes the reaction pathways and makes the prompt mechanism as dominant route in the NO emission at low and moderate temperatures.

Physiochemical and molecular features of the necrotic lesion in the Heterobasidion-Norway spruce pathosystem.

In the forest of Northern Hemisphere, the fungi Heterobasidion annosum (Fr.) Bref. s.l. causes severe root and stem rot diseases, dramatically reducing the wood quality of conifer trees. The hallmark of the host response during the infection process is the formation of necrotic lesions and reaction zones. To characterize physiochemical and molecular features of the necrotic lesion, we conducted artificial inoculations on Norway spruce plants at different developmental stages: seedlings, young and mature trees. The results were further compared against data available on the formation of reaction zones. Strong necrosis browning or enlarged necrotic lesions were observed in infected tissues. This was accompanied by elevated pH. However, the increased pH, around 6.0 in necrotic lesions, was not as high as that documented in reaction zones, above 7.0 as marked by the intensity of the blue colour in response to 2,6-dichlorophenol indophenol dye. Peroxidase activity increased in infected plants and RNA-seq analysis of necrotic lesions showed marked upregulation of defence-related genes. Our findings highlight similarities and differences between the reaction zone and necrotic lesion formation in response of conifer trees to biotic stress.

Combustion characteristics of syngas laminar microjet diffusion flames

Two-dimensional numerical investigations of laminar microjet syngas (H2 - CO) diffusion flames are carried out in the present study. A detailed parametric study on the effects of fuel jet velocity and fuel composition on global flame characteristics is analyzed. Results show that the flame height increases with an increase in fuel jet velocity, and it decreases with an increase in hydrogen content in the fuel mixture. The dependence of fuel composition and jet velocity on the rate of tube wall heat recirculation is explored. The radial extent of flame increases with increase in hydrogen content in the fuel mixture. The analysis of key reactions in the standoff region revealed the significant contribution of HO2 radical in the formation of high-temperature reaction zone. Flame extinction is observed at lower fuel jet velocities, as the composition of hydrogen in fuel mixture increases from 10 to 90%. Near extinction, the combined effect of axial and radial diffusion results in the formation of spherically shaped flames.

Microstructural evolution and mechanical properties of NiCrAlYSi+NiAl/cBN abrasive coating coated superalloy during cyclic oxidation

Cyclic oxidation behavior of NiCrAlYSi + NiAl/cBN abrasive coating at 900 °C and the mechanical properties of the coating-substrate system were investigated. Results indicated that elemental interdiffusion occurred between the coating and substrate, which caused the formation of interdiffusion zone (IDZ) and secondary reaction zone (SRZ) during aluminization, while their compositions and structures changed with oxidation. AlN interfacial layer formed at cBN/metallic matrix interface during aluminization, while it transformed into multilayer oxides during oxidation. Due to the microstructural evolution of these interfaces, the fracture behavior and bending toughness of the system changed greatly during three-point bending tests. Besides, the damage mechanisms were discussed.

Investigation of Fluid-driven Carbonation of a Hydrated, Forearc Mantle Wedge using Serpentinite Cores in High-pressure Experiments

AbstractHigh-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1·5–2·5 GPa and 375–700 °C. This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2–H2O–CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within ∼96 h at 2 GPa and 600 °C. With decreasing CO2,aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.

Effect of Ta on microstructural evolution of NiCrAlYSi coated Ni-base single crystal superalloys

The effect of Ta on microstructural evolution of NiCrAlYSi coated Ni-base single crystal superalloys at 1000 °C and 1100 °C has been investigated. Interdiffusion occurs between the NiCrAlYSi coating and the substrate, leading to the formation of inter-diffusion zone (IDZ) and secondary reaction zone (SRZ). After exposure at 1000 °C for 100 h, the initial γ/γ′ transforms to γ′ phases in the IDZ, and SRZ with σ and μ topologically close-packed (TCP) phases is formed primarily due to the inward diffusion of Al. Different behavior of SRZ formation in the alloys with various Ta content can be observed after exposure at 1000 °C, which highlights the potency of Ta addition in promoting SRZ formation. This may be ascribed to the fact that Ta promotes the precipitation of TCP phases. After exposure at 1100 °C for 100 h, the initial γ/γ′ transforms to γ layer and coarse γ′ phases in the IDZ, and no SRZ can be found. The formation of IDZ is significantly suppressed by Ta addition, which may be related to the retardation of interdiffusion between the coating and the substrate due to the increased γ′ volume fraction. Furthermore, γ′ rafting parallel to and/or perpendicular to the coating/substrate interface in the substrate beneath IDZ are found in the alloys after exposure at 1000 °C and 1100 °C. Microstructural observation shows that Ta has a potent influence on the development of perpendicular γ′ rafting. The mechanism of parallel γ′ rafting and perpendicular γ′ rafting has been discussed, respectively.

Microstructure and composition evolution of a single-crystal superalloy caused by elements interdiffusion with an overlay NiCrAlY coating on oxidation

MCrAlY (M=Ni and/or Co) overlay coating is widely used as a protective coating against high temperature oxidation and corrosion. However, due to its big difference in chemical composition with the underlying superalloy, elements interdiffusion occurs inevitably. One of the direct results is the formation of interdiffusion zone (IDZ) and secondary reaction zone (SRZ) with a high density of fine topological closed-packed phases (TCPs), weakening dramatically the mechanical properties of the alloy substrate. It is by now the main problem of modern high-temperature metallic coatings, but there are still hardly any reports studying the formation, growth and transformation of IDZ and SRZ in deep, as well as the precipitation of TCPs. In this work, a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5. Elements interdiffusion between them and its relationship on microstructure were clarified. Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface, contributing largely to the formation of IDZ. Simultaneously, diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.

地殻-メルト吸水反応帯における水・元素移動と反応帯形成プロセス：東南極セールロンダーネ山地の例

地殻-メルト吸水反応帯における水・元素移動と反応帯形成プロセス：東南極セールロンダーネ山地の例

Dynamics of nitrate degradation along an alternative latrine improved by a sawdust permeable reactive barrier (PRB) installed in an irregular settlement in the municipality of São Paulo (Brazil)

Nutrients, like nitrate and phosphate, and pathogens are the primary contaminants released into groundwater by on-site sanitation systems, which are an effluent disposal outcome for regions not covered by sanitation infrastructure, as periurban communities in developing countries. As appropriate setback distances between pit latrines and supply wells often cannot be met to avoid groundwater contamination, especially in a densely-populated situation, efficient, low-cost and accessible technologies are extremely necessary to protect water resources and surpass critical and persistent public health problems. This paper presents 1-year field-testing of an alternative latrine (AL) that incorporates two waste materials as permeable reactive barriers (PRB) in an irregular settlement at the municipality of São Paulo (Brazil). Basic oxygen furnace (BOF) slag in contact with wastewater effluent increases its pH level, which causes pathogens inactivation and phosphate adsorption. Sawdust under water saturation creates reducing conditions that encourage the growth of denitrifying bacteria that remove nitrate. A control latrine (CL) was constructed 90 m apart from AL with similar hydraulic characteristics and nonreactive materials for hydrochemical comparison. It was evident for AL the formation of well-defined nitrification and denitrification reaction zones, whereas CL overall presented nitrogen in its ammoniacal form, with incipient nitrate production at CL bottom, indicating that nitrification is probably boosted below that. BOF slag had attenuated microorganisms and phosphate almost completely, but nitrate removal average efficiency was 42%. The high pH effluent generated in BOF media may have also affected in the short-term the denitrifying bacteria in sawdust barrier 1 m below. The inverted position of the reactive barriers, i.e., sawdust PRB overlying BOF slag PRB, should be a more suitable design to achieve nitrate and pathogens removal. This kind of sanitation solution employing cheap and accessible waste materials have never been applied in the design proposed in this paper and also was a novelty for Brazilian context, proving to be a suitable technology to meet local needs.