Manganese Sand Research Articles

Removal of Fe2+ in coastal aquaculture source water by manganese ores: Batch experiments and breakthrough curve modeling.

Excessive Fe2+ in coastal aquaculture source water will seriously affect the aquaculture development. This study used manganese sand to investigate the removal potential and mechanism of Fe2+ in coastal aquaculture source water by column experiments. The pseudo-first-order kinetic model could better describe Fe2+ removal process with R2 in the range of 0.9451-0.9911. More than 99.7% of Fe2+ could be removed within 120 min while the removal rate (k) was positively affected by low initial concentration of Fe2+, high temperature, and low pH. Logistic growth (S-shaped growth) model could better fit the concentration variation of Fe2+ in the effluent of the column (R2>0.99). The Fe2 breakthrough curve could be fitted by Bohart-Adams, Yoon-Nelson, and Thomas models (R2>0.95). Smooth slices with irregular shapes existed on the surface of manganese sand after the reaction while Fe content increased significantly on the surface of manganese sand after the column experiment. Moreover, FeO (OH) was mainly formed on the surface of manganese sand after the reaction. PRACTITIONER POINTS: Fe2+ in coastal aquaculture source water could be removed by manganese ores. The pseudo-first-order kinetic model better described the Fe2+ removal process. FeO (OH) was mainly formed on the surface of manganese sand after the reaction.

Manganese Oxide Enhanced Gravity-Driven Membrane (GDM) Filtration in Treating Iron- and Manganese-Containing Surface Water

Manganese pollution in surface water has been a new concern in decentralized drinking water treatment. The dissolved manganese cannot be effectively removed by the traditional ultrafiltration (UF) process, but will cause severe membrane fouling. To address such issues, an innovative gravity-driven membrane (GDM) coupled with a dynamic manganese oxide (MnOx) film on the membrane surface was proposed, with hopes of enhancing manganese removal and alleviating membrane fouling. The results demonstrated that pre-coating a dynamic MnOx film on the membrane surface of a GDM system would effectively reduce start-up time for removing iron and manganese pollutants, without affecting the flux stabilization of the GDM. Effective manganese removal (~80%) primarily depended on the adsorption and auto-catalytic oxidation facilitated by the pre-coating of MnOx. Furthermore, the MnOx film notably enhanced organic pollutant removal efficiency. Additionally, the MnOx coated on the membrane surface acted as a skeleton, promoting the gradual formation of a biocake layer with a heterogeneous and porous structure, which benefited the flux stabilization of the GDM. In particular, the fine and homogeneous MnOx-M derived from the backflushing water of the mature manganese sand filter exhibited precise and uniform coating on the membrane surface, effectively mitigating the irreversible pore plugging caused by organic matter penetration and thereby enhancing stable flux by ~16.3% compared to the control. This study offered a novel strategy to enhance the purification efficiency of GDM system treating manganese pollution and was expected to contribute to the technological advancement of decentralized water supply scenarios.

Maximizing pollutant removal and greenhouse gas emission reduction in vertical flow constructed wetlands: an orthogonal experimental approach.

Owing to the impact of the effluent C/N from the secondary structures of urban domestic wastewater treatment plants, the denitrification efficiency in constructed wetlands (CWs) is not satisfactory, limiting their widespread application in the deep treatment of urban domestic wastewater. To address this issue, we constructed enhanced CWs and conducted orthogonal experiments to investigate the effects of different factors (C/N, fillers, and plants) on the removal of conventional pollutants and the reduction of greenhouse gas (GHG) emission. The experimental results indicated that a C/N of 8, manganese sand, and calamus achieved the best denitrification efficiencies with removal efficiencies of 85.7%, 95.9%, and 88.6% for TN, NH4+-N, and COD, respectively. In terms of GHG emission reduction, this combination resulted in the lowest global warming potential (176.8mg/m2·day), with N2O and CH4 emissions of 0.53 and 1.25mg/m2·day, respectively. Characterization of the fillers revealed the formation of small spherical clusters of phosphates on the surfaces of manganese sand and pyrite and iron oxide crystals on the surface of pyrite. Additionally, the surface Mn (II) content of the manganese sand increased by 8.8%, and the Fe (III)/Fe (II) and SO42-/S2- on pyrite increased by 2.05 and 0.26, respectively, compared to pre-experiment levels. High-throughput sequencing indicated the presence of abundant autotrophic denitrifying bacteria (Sulfuriferula, Sulfuritalea, and Thiobacillus) in the CWs, which explains denitrification performance of the enhanced CWs. This study aimed to explore the mechanism of efficient denitrification and GHG emission reduction in the enhanced CWs, providing theoretical guidance for the deep treatment of urban domestic wastewater.

New insights for simultaneous nutrient removal enhancement and greenhouse gas emissions reduction of constructed wetland by optimizing its redox environment through manganese oxide addition

Manganese oxide (MnOx) is receiving increased interest in the nutrient removal of constructed wetlands (CWs); however, its service effectiveness for simultaneous greenhouse gas (GHG) emissions reduction is still vague. In this study, three vertical flow CWs, i.e., volcanics (CCW), manganese sand uniformly mixing with volcanics (Mn-CW) and MnOx doped volcanics (MnV-CW), were constructed to investigate the underlying mechanisms of MnOx on nutrient removal enhancement and greenhouse gas (GHG) emissions reduction. The results showed that the MnOx doped volcanics optimized the oxidation–reduction potential surrounding the substrate (-164.0 ∼ +141.1 mv), and resulted in the lowest GHG emissions (CO2-equivalent) from MnV-CW, 16.8–36.5 % lower than that of Mn-CW and CCW. This was mainly ascribed to mitigation of N2O produced during the NO3−-N reduction process, according to results of 15N stable isotope labeling. Analysis of the microbial community structure revealed that due to the optimized redox conditions through chemical doping of MnOx on volcanics, the abundance of microbe involved in denitrification and Mn-oxidizing process in the MnV-CW was significantly increased at genus level, which led to a higher Mn cycling efficiency between biogenic MnOx and Mn2+, and enhanced denitrification efficiency and N2O emission reduction. This study would help to understand and provide a preferable reference for future applications for manganese-based CW.

Study on the transformation of nitrate nitrogen by manganese-catalyzed iron-carbon micro-electrolysis and microbial coupling.

Nitrate-nitrogen pertains to the nitrogen component of the overall nitrate present in a given sample in order to reduce nitrate nitrogen pollution in water, nitrate nitrogen removal methods based on iron-carbon micro-electrolysis have become a key research focus. The process and mechanism of nitrate nitrogen removal by microbial coupling was comprehensively explored in a novel iron-carbon micro-electrolysis (ICME) system. In order to establish the transformation pathway of nitrate nitrogen in water, the transformation paths of nitrate nitrogen in water before and after coupling microorganisms in three groups of continuous flow reaction devices, namely sponge iron (s-Fe0), sponge iron + biochar (s-Fe0/BC) and sponge iron + biochar + manganese sand (s-Fe0/BC/MS), were studied. The morphology and composition changes of sponge iron were analyzed by means of characterization, and the microbial population changes in the three groups were analyzed by high-throughput sequencing. Results showed that the nitrate conversion rate in the s-Fe0, s-Fe0/BC and s-Fe0/BC/MS systems reached 99.48%, 99.57% and 99.36%, respectively, with corresponding ammonia nitrogen generation, rates of 3.77%, 9.34% and 11.24% and nitrogen generation rates of 95.71%, 90.23% and 88.12%. Scanning electron microscopy imaging showed that in the s-Fe0/BC and s-Fe0/BC/MS systems the surface of sponge iron was highly corroded, with granular substances in the corrosion product clusters. X-ray photoelectron spectroscopy analysis found that the relative contents of Fe2O3 in the surface oxides of sponge iron after microbial coupling were 38.02% and 71.27% in the s-Fe0/BC and s-Fe0/BC/MS systems, while the relative Fe3O4 contents were 61.98% and 28.72%, respectively. Microbial high-throughput sequencing analysis revealed that the Chao and Ace index values in the s-Fe0 system were 871.89 and 880.78, while in the s-Fe0/BC system they were 1012.05 and 1017.29, and in the s-Fe0/BC/MS system were 1241.09 and 1198.29, respectively. The relative proportion of Thauera in the s-Fe0, s-Fe0/BC, and s-Fe0/BC/MS systems was 16.76%,14.25% and 10.01%, while the proportion of Acetoanaerobium was 15.36%, 13.27% and 11.11%, and the proportion of Chloroflexi was 0%, 1.11% and 2.18%, respectively. Furthermore, FAPROTAX function annotation found that the expression levels of chemoheterotrophs in the s-Fe0, s-Fe0/BC and s-Fe0/BC/MS systems were 43 316 OTU, 37 289 OTU and 34 205 OTU, while nitrate respiration expression levels were 16 230 OTU, 15 483 OTU and 9149 OTU, with nitrogen respiration expression levels of 16 328 OTU, 15 493 OTU and 9154 OTU, respectively. These findings suggest that nitrate is converted into nitrogen gas and ammonia nitrogen through the actions of the coupled system of sponge iron/biochar/manganese sand and microorganisms. The catalytic effect of MnO2 promotes the conversion of Fe2+ to Fe3+, generating more electrons, allowing denitrifying bacteria to reduce more nitrate nitrogen, effectively coupling the manganese-catalyzed ICME reaction and microbial denitrification. The micro-electrolysis system and the addition of manganese sand enhanced biodiversity within the s-Fe0/BC/MS system. The heterotrophic bacteria Thauera and Acetoanaerobium were the dominant microorganisms in all three systems, although the micro-electrolysis system with added manganese sand significantly reduced the proportion of facultative bacteria Thauera and Acetoanaerobium and promoted the growth of autotrophic Chloroflexi bacteria. The ecological functions of the three systems were mainly nitrate respiration and nitrogen respiration. By comparing the expression levels of nitrate respiration and nitrogen respiration in s-Fe0/BC and s-Fe0/BC/MS systems, it can be seen that the addition of manganese sand reduced microbial activity.

Treatment of wastewater containing thallium(I) by long-term operated manganese sand filter: Synergistic action of MnOx and MnOM

The long-term and stable removal of thallium (Tl) from industrial wastewater generated by mining and smelting operations remains challenging. While sand filters are commonly applied for the simultaneous removal of Mn(II) and other heavy metals, they have limited efficacy in treating Tl-contaminated wastewater. To address this gap, we operated a lab-scale Mn sand filter (MF) without added microorganisms to investigate the efficiency and mechanisms of Mn(II) and Tl(I) removal. Trends in effluent Mn(II) and Tl(I) concentrations indicated three operational stages: start-up, developing and maturation. Over time, the removal efficiency of Tl(I) gradually improved, plateauing at approximately 80 % eventually. Throughout operation, Tl(I) was sequestrated via surface complexation and ion exchange. Besides, enrichment of Sphingobium and other typical manganese oxidizing microorganisms (MnOM) during operation facilitated Mn(II) and Tl(I) oxidation and sequestration by generating biogenic manganese oxides (BioMnOx). Additionally, the accurate control of water quality and operating conditions during operation could also enhance removal efficiency. In summary, physicochemical actions of Mn oxides and biochemical actions of microorganisms synergistically contributed to the sequestration of Mn(II) and Tl(I). These findings provided a novel and sustainable method for the long-term and stable treatment of industrial wastewater containing thallium.

Study on the efficiency of manganese oxide-bearing manganese sand for removing Mn2+ from aqueous solution

To obtain efficient and rapid manganese removal performance of NMS (natural manganese sand), MOBMs (manganese oxide-bearing manganese sand) were prepared and loaded with manganese oxide formed by forced oxidation of manganese sulfate with sodium hypochlorite onto the surface of NMS. The results of SEM, EDS, BET, XPS, XRD and Zeta potential analyses showed that manganese oxides were successfully loaded on the surface of NMS, with the main components being MnO2 and Mn2O3. The surface of MOBMs is covered by needle-shaped flocculent manganese oxides, with a large number of mesopores. The isothermal adsorption and kinetic adsorption model indicated that the adsorption of Mn2+ by MOBMs occurred through monolayer adsorption and chemical adsorption. The intraparticle diffusion model showed that the adsorption process is dominated by mesoporous and microporous diffusion, which is controlled by adsorption, membrane diffusion, particle diffusion and catalytic oxidation. Under the conditions of the static test, the best adsorption conditions were determined as follows: Df = 2 g/100 ml (q = 0.149 mg/g), pH = 7.5–8.5. Under these conditions, the removal rate of Mn2+ by MOBMs was 84.47%. The presence of competing cations NH4+ and Fe2+ had a negative effect on the removal of Mn2+. The dynamic test shows that the MOBM maturation cycle takes only 7 days. MOBMs can realize the efficient utilization of low-quality NMS, shorten the maturity period of manganese removal filter material, improve the adsorption performance, and ensure the efficient removal of Mn2+.

Facile preparation of manganese sand-based monolithic catalysts with excellent catalytic performance and reusability for activation of peroxymonosulfate: The key role of pre-calcination

The construction of monolithic catalysts for peroxymonosulfate (PMS) activation with excellent performance and reusability holds great promise in environmental remediation. In this work, manganese‑cobalt bimetallic oxide (MC) loaded manganese sand (MS) monolithic catalysts (0.5MC/800MS) with enhanced catalytic performance were obtained by modulating the interaction between manganese‑cobalt bimetallic oxides and manganese sand. The calcination of MS results in a partial reduction of the manganese and iron fractions, in particular in the decomposition of MnO2 to form Mn2O3. The changes in the chemical properties of Mn in MS greatly enhance the activity of Co in MC. 0.5MC/800MS exhibited a remarkably higher efficacy for PMS activation than 0.5MC/MS. The effects of several reaction parameters (i.e., PMS dosage, catalyst dosage, reaction temperature, initial pH value, and inorganic ions) on tetracycline (TC) removal were comprehensively investigated by batch catalytic experiments. 0.5MC/800MS can effectively activate PMS in the pH range of 3–9 to generate sulfate radical (SO4−) for TC degradation. In continuous catalytic experiments, the instantaneous and delayed removal of TC was 71.3 % and 84.9 %, respectively, after 21 L of simulated wastewater flowed through the fixed-bed reactor. Especially, when 6 L of actual industrial cleaning wastewater was treated, the TOC removal ratio of about 85 % could be maintained. This study provides new insights into optimizing the interaction of manganese sands with surface spinel for the development of novel macroscopic Fenton-like catalysts.

The treatment of As(III)-contaminated water by using granular Fe-Mn-Cu composite oxide: Removing As(III) via the oxidation-adsorption process and handling the release of manganese ions

It is a challenge to obtain an outstanding removal performance for the treatment of As(III)-contaminated water without the risk of secondary pollution. In this study, a novel granular adsorbent of Fe-Mn-Cu composite oxide (GFMCO) was fabricated by the redox-precipitation method. Batch adsorption experiments were conducted to investigate the adsorption behavior of As(III) onto GFMCO, including adsorption isotherms, adsorption kinetics, the influences of pH and competing anions, and reuse performance. The adsorption equilibrium of As by GFMCO could be achieved within 12 h. As(III) can be effectively oxidized to As(V) and adsorbed by GFMCO with a theoretical maximum As adsorption capacity of 72.88 mg/g. The As removal performance remained stable within a wide pH range of 3–9. Phosphate and silicate anions inhibited As removal, whereas chloride ions, sulfate anions, calcium ions, and magnesium ions had little effect. In addition, GFMCO could be successfully regenerated and reused with almost no loss in adsorption capacity during four consecutive cycles. Moreover, the GFMCO-packed column used as an adsorption reactor could produce approximately 969 bed volumes of treated water with the effluent arsenic concentration below 10 μg/l. Although divalent manganese ions (Mn(II)) were released from the GFMCO-packed column, efficient Mn(II) removal could be achieved with the combination of sodium hypochlorite dosing and the manganese sand filtration. Overall, this work provides a promising adsorbent for As(III) removal with satisfactory efficiency and good security.

Oxygen vacancies enhanced natural manganese sand activation by PMS for CBZ degradation: Intermediate toxicity and DFT calculations

The preparation of sulfate-based advanced oxidation catalysts is usually both complex and expensive. In this study, natural manganese sand enriched with oxygen vacancies was prepared by NaBH4 reduction of natural manganese sand for activating peroxymonosulfate (PMS) to remove carbamazepine (CBZ). 70% of carbamazepine was degraded at 120 min when natural manganese sand enriched with oxygen vacancies and PMS were dosed at 0.4 g/L and 0.3 g/L respectively, and the reaction rate constant of the natural manganese sand system with rich oxygen vacancies was 7 times that of the common system. The mineralization of total organic carbon (TOC) reached 41.9%. Combined EPR and radical quenching assays revealed that degradation of pollutants relied on the involvement of free radicals and non-free radicals, in which singlet oxygen was dominant. The XPS results showed that the redox cycles of Fe3+/Fe2+ and Mn4+/Mn3+/Mn2+ promoted the generation of free radicals. Density functional theory results also showed that the energy required for PMS to adsorb on natural manganese sand with many oxygen vacancies was decreased, and the OO bond was elongated, which was beneficial to the catalytic reaction. According to LC-MS and Fukui function, the degradation route of CBZ was predicted, and the toxicity of the breakdown products was calculated. The research provides a reference for introducing oxygen vacancies in natural catalysts to improve degradation performance for “green (source) to green (application)”.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks.

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Enhancement of micropollutant biotransformation by adding manganese sand in constructed wetlands

Recent investigations have shown that the addition of manganese (Mn) sand to constructed wetlands (i.e., Mn-amended CWs) can improve the performance of organic micropollutants (MPs) removal. In addition to the direct oxidation and adsorption of Mn oxides, the indirect role of Mn oxides in MP biotransformation is crucial to the removal of MPs but has seldom been referred to. Herein, we constructed lab-scale CWs with or without the addition of natural Mn sand (∼35% Mn oxides) to decipher the influence of Mn oxides on the biotransformation of the six selected MPs which commonly existed in the wastewater. The experimental results showed that the addition of Mn sand to CWs can improve the removal of MPs (8.48% atrazine, 13.16% atenolol, and 6.27% sulfamethoxazole [pairwise Wilcoxon test p < 0.05]). Combining the detection of transformation products and metagenomic sequencing, we found that the enhanced removal of atrazine in the Mn-amended CWs was mainly due to the bioaugmented hydroxylation process. The enrichment of biotransformation-related genes and associated microbes of atenolol and sulfamethoxazole in Mn-amended CWs indicated that the addition of Mn sand to CWs can strengthen the biotransformation of MPs. Furthermore, we found that these MP-biodegrading microbes were widely present in the full-scale CWs. Overall, our research provides fundamental information and insights for further application of Mn-amended CWs in MP removal.

Natural manganese sand activates sodium hypochlorite to enhance ionic organic contaminants removal: Optimization, modeling, and mechanism

Although sodium hypochlorite acting as an oxidant has been investigated for the role it plays in the degradation of organic contaminants, little attention has been paid to its activation and efficient utilization. In this study, natural manganese sand (NMS) was verified to be effective for activation of sodium hypochlorite (NaClO). Due to the generation of O2−, the removal efficiency of ionic organic contaminants in NMS/NaClO system was 1.9–4.1 times higher than that in NMS or NaClO alone. Hence, NMS activated NaClO system performed ~96.6 % contaminants removal efficiency at a wide pH range (pH 5–9). Kinetic modeling yielded that the NMS dosage was more important than NaClO dosage. Long-term stability was observed in the presence of various salts (bicarbonate, sulfate, phosphate, and chloride). Characterization results revealed that electron transfer among NMS, NaClO, and organic contaminants was responsible for NaClO activation. Then NaClO-based Fenton-like process was proposed by tracing the degradation intermediates of methyl orange (MO) and generations of reactive oxygen species in the MO/NMS/NaClO system. This study presents the potential of NMS to activate NaClO and enhance ionic organic contaminants removal from aquatic environments.

Study on the Removal of Iron and Manganese from Groundwater Using Modified Manganese Sand Based on Response Surface Methodology

This study used modified manganese sand as an adsorbent to explore its adsorption effect on iron and manganese ions from groundwater. The effects of pH, manganese sand dosage, and the initial concentration of Fe/Mn on the removal rate of iron and manganese ions were studied through single-factor experiments. Based on the above three factors, a quadratic polynomial model between the adsorption rate and the above factors was established to determine the optimal adsorption conditions. The response surface analysis showed that pH had the most significant effect on the adsorption process. The optimum conditions for the adsorption of iron and manganese ions by modified manganese sand were pH = 7.20, the dosage of manganese sand = 3.54 g/L, and the initial concentration ratio of Fe/Mn = 3.80. The analysis of variance showed that the RSM model could accurately reflect the adsorption process of manganese sand. In addition, we confirmed that the relative error between model predictions and experimental values was close to 1%, proving that the response surface model was reliable. The kinetic data of the manganese sand were described well with the pseudo-second-order model. The isothermal adsorption of iron and manganese ions by modified manganese sand was fitted well using the Langmuir equation.

Degradation of chlortetracycline hydrochloride by peroxymonosulfate activation on natural manganese sand through response surface methodology

This work studies the degradation of chlortetracycline hydrochloride (CTC) by activated peroxymonosulfate (PMS) with natural manganese sand (NMS). Meanwhile, the NMS was characterized and analyzed by isothermal nitrogen adsorption (BET), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscope (SEM). It can be induced that NMS material may contain C, O, Al, Si, Fe, Mn, and K, and the proportion of each is 6%, 9%, 13%, 34%, 27%, 5%, and 6%. Critical parameters, including initial pH value, catalyst dosage, and PMS amount, were optimized through response surface methodology. One of the essential significances of response surface methodology (RSM) is the establishment and optimization of the mathematical model to reduce the complexity of the experimental process. It can provide the degree of mutual influence between various factors and optimize the response based on the investigated factors. Results indicated that 81.65% of CTC could be degraded under the optimized conditions of PMS amount 2.02g/L, the NMS dosage 0.29g/L and pH 3.87. Also, it shows that NMS is the most powerful of each factor on the degradation efficiency. We proposed the degradation pathways of CTC from the liquid chromatograph-mass spectrometer (LC-MS) results. Therefore, NMS could be applied as an efficient activator of peroxymonosulfate to purify the water and wastewater.

Enhanced nitrate removal and nitrogen-selective conversion mechanism of a combined sponge iron/biochar/manganese sand system

To find a method for efficient removal and conversion of inorganic nitrogen compounds in three reduction systems, which are the sponge iron (s-Fe0)，the sponge iron + biochar (s-Fe0/BC) micro-electrolysis system and the sponge iron + biochar + manganese sand (s-Fe0/BC/MS)-enhanced micro-electrolysis system, the studies have been completed on the conditions of different material ratios and initial pH. When the initial pH is 7, the nitrate removals reached to 7.6%, 61.5% and 80.3%, the nitrogen ratio of products reached to 5.8%, 22.4% and 38.3% respectively in s-Fe0, s-Fe0/BC (3:1) and s-Fe0/BC/MS (6:2:1) systems. The s-Fe0/BC/MS system was the best at nitrate removal over a wide pH range (2−12). At the same time, the nitrogen selectivity in the s-Fe0/BC/MS system was always better than that in other two systems. The X-ray photoelectron spectroscopy (XPS) results showed that the addition of manganese sand could enhance the ratio of Fe3O4 in the sponge iron surface oxide, reduce the passivation of the sponge iron surface and accelerate the electron transfer rate. As a catalyst for the corrosion of sponge iron, manganese sand can increase the corrosion of sponge iron and enhance the micro-electrolysis role between iron and carbon.

Removal of Mn 2+ in geothermal water by manganese sand: process and mechanisms

Geothermal water resources are being exploited widely in many areas to relieve pressure on water resources generally. Excessive Mn 2+ concentration in geothermal water will seriously reduce its utilization rate. Therefore, this study investigated the removal of Mn 2+ from simulated geothermal water by manganese sand. The Mn 2+ removal rate from simulated water with a concentration of 10 mg l −1 by 2 g manganese sand at 298, 323, 343 and 363 K was more than 90%. The removal efficiency of Mn 2+ is influenced by adsorbent dosage, adsorbent particle size, initial Mn 2+ concentration and competing ions, and less so by a pH of 5–9. A pseudo-first-order kinetic model fits the adsorption data better than a pseudo-second-order model. The pseudo-first-order adsorption rate constants (K 1 ) ranged from 0.14 to 0.5 h −1 as the temperature increased from 298 to 363 K. The Langmuir isotherm model fits the adsorption data better than the Freundlich and Temkin isotherm models. The maximum monolayer adsorption capacities ( q m ) obtained by the Langmuir isotherm model fitting were 0.91/1.02/1.22/1.23 mg g –1 at 298/323/343/363 K. Thermodynamic studies revealed that the adsorption was endothermic and physical in nature. These findings suggest that the potential of manganese sand for removing Mn 2+ in geothermal water is considerable. Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues

The microbial diversity of groundwater and manganese sand filtered water in rural water supply project

The microbial diversity of groundwater and manganese sand filtered water in rural water supply project

Technical and economical viability of a graywater recycling system employing an integrated preliminary settlement and filtration process

AbstractThe collection and reuse of graywater has become an important strategy for achieving the goal of sustainable development. In this work, an integrated preliminary settlement and filtration process was developed for treating shower water which was obtained from a college bathroom toilet. The system's pollutant removal efficiency was examined for three different filter media: manganese sand, quartz sand and ceramsite. The results showed that for ceramsite, the average removal of turbidity, CODcr, NH3-N, and anionic surfactant was 93.3%, 68.6%, 78.9, and 83.5% respectively. For manganese sand, the values were 84.6%, 61.5%, 57.8 and 59%, while for quartz, they were 88.9%, 47.9%, 39.5% and 51.9%. A cost–benefit analysis revealed that the payback period of graywater recycling systems ranges from 3.16–5.30 years and benefit–cost ratios are in the range of 1.23–1.67, depending on tank size. The proposed system provides a new strategy for enhancing water-use efficiency in buildings in a more decentralized way.

Enhanced Nitrogen Removal of Steel Rolling Wastewater by Constructed Wetland Combined with Sulfur Autotrophic Denitrification

Constructed wetlands (CWs), an ecological treatment technology, is suitable for advanced treatment, but has an unsatisfying denitrification performance for steel rolling wastewater with low C/N ratio. This study combined sulfur autotrophic denitrification (SAD) with conventional constructed horizontal subsurface flow wetlands to treat steel rolling wastewater, exploring the feasibility of applying SAD to enhance the denitrification performance of CWs. The reactor consists of two sections, one filled with manganese sand and gravel (HFC) and another filled with ceramic, sulfur, and lime (HFSAD). Results showed that HFC had a good performance on removing turbidity, DO, COD, and TP, while the average removal efficiency of total nitrogen (TN) in HFC was just 25.6%. On this basis, HFSAD could remove 45.6% of TN subsequently, whose denitrification rate was 4–6 times as high as that of HFC. Increasing hydraulic retention time could improve removal efficiency of contaminants in HFC and HFSAD in different degrees. The analysis of microbial community structure, observation results of fillers and monitored sulfate all provided proofs for the occurrence of SAD. CWs combined with SAD can be applied in the treatment of steel rolling wastewater with low carbon, which can provide reference for ecological wastewater treatment, water saving, and recycling in iron and steel enterprises.