Leachate Recycle Research Articles

Two-stage leaching of calcium and vanadium from high-calcium steelmaking slag

ABSTRACT Vanadium (V) is a critically important element in many industries. A widely used recovery process is a combination of roasting and leaching. However, roasting is an energy-intensive stage. Generally, basic oxygen furnace (BOF) slag is high in calcium (Ca) but low in V. Ca content and its chemical nature can prevent V leaching. This study presents a potential two-stage leaching process for Ca and V from BOF slag. The method is environmentally friendly using low temperatures and enabling leachate recycling. Furthermore, the utilisation rate of the slag can be higher due to Ca recovery. Ca is first leached using ammonium nitrate and nitric acid solution. The V-containing residue is directed to the second stage, where V is leached using ammonium carbonate ((NH4)2CO3). Ca leaching efficiency was 71% achieved with a low temperature (40°C) and in 20 min. > 99% of the dissolved element was Ca. Increasing the total nitrate concentration increased the leaching efficiency. Reducing the L/S ratio improved selectivity. The solid material was analysed after the leaching stages and a clear change was observed after the Ca-stage. The V leaching efficiency was 50%. > 88% of dissolved element was V (L/S 8, [(NH4)2CO3] 200 g/L, 60°C, and 60 min). Increasing [(NH4)2CO3] and L/S ratio slightly improved the leaching efficiency but decreased selectivity. The studied process implements circular economy principles and has been developed for side streams with low V concentrations. However, further optimisation and developments are required regarding the effectiveness of the process.

Assessing moisture contributions from precipitation, waste, and leachate for active municipal solid waste landfills

Precipitation, evapotranspiration (ET), waste tonnage, landfill gas (LFG), and leachate data were aggregated from public sources to perform a 5–10 year water balance and estimate the contributions of three water sources (precipitation, incoming waste, and leachate recycling) for 36 active municipal solid waste (MSW) landfills in Ohio, USA. Uniquely, the water balance incorporated waste decomposition, using gas collection data to inform mass loss from biodegradation. Moisture contents of 20–30% for incoming waste indicate that entrained water is the largest source of landfill moisture. Infiltration of precipitation into the landfill after ET was the second largest source. Even at facilities where a majority of the leachate generated was recirculated, it did not significantly affect the moisture content in that year. Using the water balance approach, it appears leachate recirculation is unlikely to increase moisture content above 40% by mass, a regulatory threshold in the US, which would impose stricter air pollution control requirements. However, poor stormwater management could easily allow for “bioreactor” conditions to develop. The calculated landfill moisture content was significantly affected by the assumed runoff coefficient (CRO) parameter. CRO values below 20% and above 50% produced unrealistically high or low moisture contents, respectively. This approach can assist operators and regulators in understanding the contribution of different sources to a landfill's moisture profile and avoid future operational problems.

Effective Recovery Process of Copper from Waste Printed Circuit Boards Utilizing Recycling of Leachate

This study presents an optimized leaching and electrowinning process for the recovery of copper from waste printed circuit boards including studies of chemical consumption and recirculation of leachate. Optimization of leaching was performed using response surface methodology in diluted sulfuric acid and hydrogen peroxide media. Optimum leaching conditions for copper were found by using 3.6 mol L−1 sulfuric acid, 6 vol.% hydrogen peroxide, pulp density of 75 g L−1 with 186 min leaching time at 20°C resulting in complete leaching of copper followed by over 92% recovery and purity of 99.9% in the electrowinning. Study of chemical consumption showed total decomposition of hydrogen peroxide during leaching, while changes in sulfuric acid concentration were minor. During recirculation of the leachate with up to 5 cycles, copper recovery and product purity remained at high levels while acid consumption was reduced by 60%.

Valorization of food waste and economical treatment: Effect of inoculation methods

We evaluated cost-effective food waste (FW) treatment and synthesis of volatile fatty acids (VFA) using a leach bed reactor (LBR) operated at neutral pH and room temperature to maximize the profit from recovered products. Three inoculation strategies that include (1) inoculum pretreatment, (2) pretreatment plus leachate recycle, and (3) sole leachate recycle were examined and LBR performance was compared in these inoculation conditions. The inoculation method influenced the hydrolysis of FW in the LBR. Hydrolysis yield was as high as 771 ± 4 g cum.sCOD/kg VSadded with the second inoculation method only in a short reaction time of 6 d. Butyric and acetic acids consistently dominated VFA, and the LBR achieved the highest VFA yield of 649 ± 13 g COD/kg VSadded in the second inoculation. Bacterial community dynamics targeting 16S rRNA gene suggested that Roseburia would be the key player to fermentation of slowly biodegradable FW (e.g., fibers), while multiple types of bacteria affiliated with Enterobacteriaceae, Lactococcus, and Bacteroides mainly fermented FW to butyric and acetic acids at initial phase. The operating cost for FW treatment was calculated $88.1-$126.8 per ton of VSadded in the LBR. This study suggests that LBRs can economically stabilize FW only in 6 d without regular inoculation of exogenous microorganisms, along with high VFA recovery.

Constructed wetlands as a treatment method for landfill leachate

On-site treatment of landfill leachate may soon be recommended by the Swedish Environmental Protection Agency. Various methods and concepts are currently used or have been proposed to this end. This paper describes a treatment system for landfill leachate using a constructed wetland as a tool for; water volume reduction, leachate recycling, bioremoval of organics and nutrients, precipitation and adsorption of metals, gas production enhancement, gaseous emissions minimisation and as pre-treatment before a polishing step using other methods, for example, reverse osmosis. Assuming precipitation values corresponding to Southern Sweden a wetland covering 25 % of the drained area will reduce the annual leachate flow by 30%. If 80 % is covered by wetland all precipitation will be lost as evapotranspiration. A test plant has been established at the Swedish waste company ASSY:s landfill in Hedeskoga, both a constructed wetland and the reverse osmosis pilot plant, to test the effectiveness of these methods

Leaching and concentration of P and K from P-K associated ore by using a sequential leaching process with leachate recycling

The concentrations of P and K in leaching solution are relatively low and the consumption of acid is relatively large, which are the existing problems in the leaching of P and K from P-K associated ore by using the low-temperature acid leaching process. In this work, a sequential leaching process with leachate recycling was developed, in which P and K were sequentially leached out from P-K associated ore and the obtained P- and K-containing leachates were recycled into the next leaching process. In this sequential process with leachate recycled two times the concentrations of K and P2O5 in leachate were increased from 20.18 and 15.79 g/L to 53.26 and 45.97 g/L, respectively. In comparison, in the simultaneous leaching process with leachate recycling both the leaching efficiencies of K and P and the concentrations of K and P2O5 were significantly lower than those in the sequential leaching process, which can be mainly attributed to the fact that Ca in the ore, which could react with PO43− to generate Ca-containing sediments, was precipitated first in the sequential leaching process. The sequential leaching process with leachate recycling will provide an efficient method for leaching and concentrating P and K from P-K associated ore.

Mass balance analysis on the behavior of major elements disposed at a waste landfill site

Understanding the behavior of major elements in landfill is necessary for effective landfill site management. However, there have been no established methods to study the mass balance of major landfill elements, excluding some studies focused on specific target materials. In this study, different landfill management methodologies were used to conduct mass balance analysis of three major elements at Sudokwon Landfill Site 2 (LS2) in South Korea during 2001–2014. The results indicated that biochemically decomposable carbon accounted for 38.2% of the total landfill organic carbon content. Further, 51.3% of this decomposable fraction underwent decomposition during the research period, 99.0% of which was emitted in landfill gas as CO2 and CH4. In terms of sulfur, 6.1% of the total decomposed sulfur was emitted as H2S (97.0%), and almost all of the total decomposed nitrogen was emitted (5.7%) in leachate as NH4+-N. LS2 had a low decomposition rate due to the dryness of the landfill site and the increasing ratio of demolition waste, which does not decompose easily. Therefore, thermochemical energy recovery before waste disposal and leachate recycling seem to be necessary. In terms of leachate recycling, economic measures to prevent nitrogen accumulation may be required in the long term. Additionally, for suppressing H2S generation, separate disposal of waste soil produced throughout the course of mechanical pretreatment of demolition waste should be conducted.

Biosorption an innovative tool for bioremediation of metal-contaminated municipal solid waste leachate: optimization and mechanisms exploration

Municipal solid waste poses a risk on surrounding environment and public health, mainly because of unscientific disposal and shortage of facilities for proper handling and recycling of leachate. This research article objective is to pinpoint the indigenous fungal isolates of waste leachate samples. Therefore, we carried out biosorption of Cd2+ tested the applicability by applying indigenous fungal isolates. The limited number of fungal isolates was found based on their ability for biosorption of Cd2+ metal. The fungal strains Trichoderma sp., Aspergillus niger and Aspergillus flavus were reported as potential strains for metal exclusion ability from the leachate. Among them, the Trichoderma sp. was found as excellent fungal agent for Cd2+ absorption. The optimum pH was 5.5 ± 1, temperature 45 °C, and spore concentration 10−5 to achieve the maximum biosorption, and 35 days of incubation period were required by three strains. The maximum metal biosorption achieved was comparable for the three isolates: 56.34% by Trichoderma sp., 44.74 and 42.04% by A. niger and A. flavus, respectively. Concluding, the further intending application to identified potentially fungal isolates is able to improve the efficiency of metal biosorption. These strains are recommended for development of consortia could become a best technique for MSW leachate treatment if its reliability and applicability should be verified prior to technology acceptance.

마이크로버블을 이용한 음폐수의 외부탄소원으로서의 재활용 가능성 연구

The purpose of this research was to examine the possibility on the recycling of foodwaste leachate as external carbon sources using microbubble. The following operating conditions were selected: pressurizing tank 3 bar, circulation flow rate 3.65 LPM, and air flow rate 0.3 LPM with batch type. Microbubble contact time of 18 hours is optimal time to satisfy the recycling of foodwaste leachate as external carbon sources with batch type. HRT 18 hours came up to standard for external carbon sources, except for T-P concentration with continuous type. Coagulants need to be used for removal of dissolved phosphorus concentration by more than 88.5% of the total phosphorus concentration. The VFA was influenced by the organic decomposition rate and the concentration in the aerobic condition. It was considered that the VFA was needed for selection the optimal HRT or the addition of acid fermentation process in order to meet recycling standard of foodwaste leachate.

Current Status and Future Perspective of Recycling Copper by Hydrometallurgy from Waste Printed Circuit Boards

The current replacement of electronic products is speeding up, resulting in a growing number of e-waste. Electronic waste, especially waste print circuit boards contain large amounts of copper, which not only bring greater ecological threat, but also cause a serious waste of copper resources. Therefore, the study on clean, effective copper leaching technology has a very important practical significance to reduce environmental hazards of waste print circuit board and resources recycling. Hydrometallurgical is a better technology for recycling copper from waste print circuit boards. In this article, hydrometallurgical copper recovery system is divided into four categories: acid leaching, ammonia - ammonium leaching, chloride leaching, as well as other ways of leaching. The advantages and disadvantages of leaching of copper system are analyzed in the process of copper resource utilization. Studies abound on recycling copper from copper-containing waste with citric acid and other complexing agents as the leaching reagent, but studies on recycling copper from waste print circuit boards are rarely reported, which can be used for reference. The trends of the research are using environmentally friendly reagent as leaching agent, selecting the appropriate leaching solution at a certain temperature and pressure and optimizing the subsequent separation procedure. Recycling of waste gas and waste leachate generated in the hydrometallurgical processcan further reduce chemical costs and meet increasingly exacting environmental requirements.

Anaerobic fermentation of organic solid wastes: volatile fatty acid production and separation.

Anaerobic fermentation of organic municipal solid waste was investigated using a leach-bed reactor (LBR) to assess the volatile fatty acid (VFA) production efficiency. The leachate recycle rate in the LBR affected the VFA composition of the leachate. A six-fold increase in the recycle rate resulted in an increase of the acetic acid fraction of leachate from 24.7 to 43.0%. The separation of VFAs via leachate replacement resulted in higher total VFA production. VFA separation from synthetic VFA mix and leachate of a fermented organic waste was assessed via a counter-current flow polytetrafluoroethylene (PTFE) membrane contactor. Acetic and propionic acid permeation fluxes of 13.12 and 14.21 g/m(2).h were obtained at low feed pH values when a synthetic VFA mix was used as a feed solution. The highest selectivity was obtained for caproic acid compared to that of other VFAs when synthetic VFA mix or leachate was used as a feed solution. High pH values and the presence of suspended solids in the leachate adversely affected the permeation rate.

Enhancement of the anaerobic hydrolysis and fermentation of municipal solid waste in leachbed reactors by varying flow direction during water addition and leachate recycle

Poor performance of leachbed reactors (LBRs) is attributed to channelling, compaction from waste loading, unidirectional water addition and leachate flow causing reduced hydraulic conductivity and leachate flow blockage. Performance enhancement was evaluated in three LBRs M, D and U at 22±3°C using three water addition and leachate recycle strategies; water addition was downflow in D throughout, intermittently upflow and downflow in M and U with 77% volume downflow in M, 54% volume downflow in U while the rest were upflow. Leachate recycle was downflow in D, alternately downflow and upflow in M and upflow in U. The strategy adopted in U led to more water addition (30.3%), leachate production (33%) and chemical oxygen demand (COD) solubilisation (33%; 1609g against 1210g) compared to D (control). The total and volatile solids (TS and VS) reductions were similar but the highest COD yield (g-COD/g-TS and g-COD/g-VS removed) was in U (1.6 and 1.9); the values were 1.33 and 1.57 for M, and 1.18 and 1.41 for D respectively. The strategy adopted in U showed superior performance with more COD and leachate production compared to reactors M and D.

In Vitro Oxidative Damage Induced in Livers, Hearts and Kidneys of Rat Treated with Water Extract (Leachate) from Municipal Battery Recycling Site: Evidence as Environmental Pollution and Tissue Damage

Abstract The health effects of the Municipal Auto-Battery Dust Leachate (MABDL) and Elewi Odo Municipal Auto- Battery Recycling Site Leachate (EOMABRL) on levels of Thiobarbituric Acid Reactive Substances (TBARS) were investigated in livers, kidneys and hearts of male albino rat-in vitro. The two varieties of leachates significantly (p<0.05) increased MDA level in the liver, kidney and heart in a dose-dependent manner with Municipal Auto-Battery Dust Leachate (MABDL) having stronger induction ability than Elewi Odo Municipal Auto-Battery Recycling Site Leachate (EOMABRL). MDA levels of EOMABRL were significantly (p<0.05) elevated in the liver, kidney and heart by 55.56%, 41.3% and 39.13% respectively compared to the corresponding control at the highest dose. Similarly, MDA contents of MABDL were significantly (p<0.05) elevated in the kidney, heart and liver by 195.65%, 115.2% and 83.33% respectively compared to the corresponding control at the highest dose. However, the liver is highly sensitive to EOMABRL exposure than kidney and heart. In contrast, the kidney is more susceptible to MABDL exposure than heart and liver. Collectively, the possible mechanisms by which varieties of battery leachates exert nephritis, hepatitis and cardiovascular malfunctioning is through high induction of lipid peroxidation and heavy metal (Cu2+ ,Fe2+ ,Pb2+ etc) catalyzed hydrogen peroxide decomposition to produced OH• via Fenton reaction.

Treatment of Landfill Leachate Using Ganoderma Australe Mycelia Immobilized on Ecomat

Biological processes have been proven to be efficient in treating landfill leachates. In this study, treatment of landfill leachate by Ecomat-immobilized mycelia of Ganoderma australe packed in a column was investigated. Continuous recycling of leachate at a constant flow (20 ml/min) was operated for 10 cycles to facilitate biological reactions. Diluted leachate (50%) and raw leachate (100%) were tested for comparison of efficiency of treatment. The results showed that biological oxygen demand (BOD 5 ) was not removed for diluted leachate and a slight removal of 0.14 and 1.72% for raw leachate after cycles 4 and 10, respectively. Chemical oxygen demand (COD) removal occurred after each cycle with diluted leachate demonstrating higher removal compared to raw leachate. The highest percentage of COD removal of 51.62% for diluted leachate and 22.79% for raw leachate were achieved after the tenth cycle. Ecomat-immobilized mycelium of Ganoderma australe could also reduce ammoniacal nitrogen (NH 3 -N) exhibiting highest reduction of 45.95% and 30.90% after cycle 8 for diluted and raw leachate, respectively. These findings suggested that a white rot fungus, G. australe has the ability to be considered as potential candidate in landfill leachate treatment.

Factors influencing the release rate of uranium, thorium, yttrium and rare earth elements from a low grade ore

This paper presents data from laboratory leaching of a mineralogically complex low grade ore containing uranium (U), thorium (Th), yttrium (Y), rare earth elements (REEs) and accessory pyrite. The study examines the influence of varying the leaching protocol on the rate of release of U, Th, Y and REEs. Leaching protocols were designed to simulate a range of heap/in situ stope leaching scenarios. Protocol variants included flushing frequency, leachate recycle, nutrient (9K salts) addition and ferric sulphate addition to cells. Maximum extractions over 52weeks were: 58% U, 50% Th, 36% Y and 45% of the REEs; observed in cells flushed fortnightly with a ferric sulphate lixiviant (0.5g/l, pH 3.5). Flushing with tap water once monthly resulted in second highest observed extractions (57% U, 6% Th, 27% Y, 37% REEs) with the exception of Th, where the lower release was due to insufficiently low pH for Th mobilisation. Pourbaix plots indicate that redox potentials within the leaching system were buffered by coffinite dissolution. The high redox potentials, acidic pH and elevated sulphate concentrations required for metals dissolution were found to be a consequence of (a) direct addition of ferric sulphate as a lixiviant or (b) in situ generation of acidity and ferric sulphate via microbially-mediated oxidation of accessory pyrite. Generation and maintenance of acidic sulphate-rich interstitial water appear to control the dissolution of Th, Y and REEs in addition to U. The presented data highlight that significant U, Th, Y and REEs can be mobilised from rock materials by the addition of a ferric sulphate lixiviant, furthermore periodic flushing with water alone is sufficient to achieve similar release of U, Y and REEs where accessory pyrite is available in the reacting system. These findings have significant implications for recovery of valuable elements from low grade and marginal ores or materials previously considered as wastes.

ESTIMATION OF SOLID WASTE BIOMETHANIZATION: DEVELOPMENT OF NOVEL METHODOLOGY AND ANFIS MODELS

This article presents the application of a technique of artificial intelligence (AI) that explores the possibility of using a model to estimate the biomethanization of municipal solid waste (MSW). The model uses data from an experiment in which MSW is anaerobically digested under three different moisture regimes by leachate recycling. A method utilizing a neurofuzzy inference system is used because AI systems have a high capacity for empiric learning. Considering the importance of finding an effective selection of the most valuable variables for the model, this methodology includes the following techniques: Exhaustive Search (or brute-force search); Stepwise, a step-by-step regression method; and the use of Expert Knowledge. With the use of the fuzzy logic toolbox (MATLAB®), nine models were generated. However, when a case study is used to detail the method, the proposed methodology can also be used with any other system with a set of input and output data.

중온혐기성소화조에서 외부 CO2Stripping을 이용한 In-situ 고순도 메탄회수 공정 개발

Abstract : A simple in-situ methane enrichment system in mesophilic anaerobic digestion was developed to take advantage of the differing solubilities of CO 2 and methane. The methane enhancement systems consisted of low solids plug-flow maize digester coupled with a leachate recycle loop to an external CO 2 stripper. The effects of leachate recycle rate (LRR) and reactor alkalinity on the re-sulting offgas CH 4 contents, biogas productivity and TVS removal efficiency were quantitively evaluated. The results showed that offgas CH 4 contents of over 94% was achieved at 3 volume of leachate recycle per volume of reactor per day (3 v/v-d) and at the reactor alkalinity of 4 g/L as CaCO 3 , as the optimum operating conditions. The TVS removal efficiency of the methane enhancement system was 79% which corresponds to 94% of the control reactor and the methane productivity appeared to be 0.71 v/v-d. Offgas me-thane contents correlated well with LRR. However excessively high LRR led to the decrease in TVS removal efficiency.

Bed mixing and leachate recycling strategies to overcome pressure drop buildup in the biofiltration of hydrogen sulfide

The effects of leachate recycling and bed mixing on the removal rate of H2S from waste gas stream were investigated. The experimental setup consisted of an epoxy-coated three-section biofilter with an ID of 8cm and effective bed height of 120cm. Bed material consisted of municipal solid waste compost and PVC bits with an overall porosity of 54% and dry bulk density of 0.456gcm−3. Leachate recycling had a positive effect of increasing elimination capacity (EC) up to 21gSm−3 bedh−1 at recycling rates of 75mld−1, but in the bed mixing period EC declined to 8g Sm−3bedh−1. Pressure drop had a range of zero to 18mm H2Om−1 in the course of leachate recycling. Accumulation of sulfur reduced removal efficiency and increased pressure drop up to 110mm H2Om−1 filter during the bed mixing stage.

Influence of Recycling Different Leachate Volumes on Refuse Anaerobic Degradation

The aim of this work was to determine the appropriate moisture regime, attained by leachate recycling, to achieve the highest municipal solid waste (MSW) biodegradation rate. To this end, leachate characteristics, methane production rate and changes in degraded refuse were studied. Twenty laboratory-scale bioreactors were loaded with MSW from the landfill of Patzcuaro (Mexico), four were used as controls and sixteen were operated under leachate recycling to achieve moisture content regimes (%MC) of 50, 60, 70 and 80%, bioreactors operated for 264 days. Hydrolysis, acidogenic and methanogenic phases were determined and studied. ANOVA and Tukey's HDS tests revealed significant differences in leachate concentration characteristics when using different recycling volumes. Maximum methane production rate was found in the 70% MC regime, whereas the highest volume was found to produce a wash out effect in the refuse matrix. Also, the highest total volatile solids removal was found in the solid phase of the 70% MC regime.

Secondary Compression of Municipal Solid Wastes and a Compression Model for Predicting Settlement of Municipal Solid Waste Landfills

The estimation of the capacity and settlement of landfills is critical to successful site operation and future development of a landfill. This paper reports the results of a study on biodegradation behavior and the compression of municipal solid wastes. An experimental apparatus was developed which had a temperature-control system, a leachate recycling system, a loading system, and a gas and liquid collection system. Experiments were performed both with and without optimal biodegradation for comparative purposes. Test results indicated that settlement resulting from creep was relatively insignificant when the biodegradation process was inhibited. Compression due to decomposition under optimal biodegradation conditions was found to be much larger than compression associated with creep. The biodegradation process was significantly influenced by the operational temperature. A one-dimensional model is proposed for calculating settlement and estimating the capacity of the landfill under relatively optimal biodegradation conditions. The model was developed to accommodate the calculation of settlement in landfills when a multistep filling procedure was used. The calculation method is relatively simple and convenient for design purposes. Simulations of the physical processes showed that enhancing solid waste biodegradation during the filling stage can considerably increase the capacity of the landfill and reduce postclosure settlements.