Examining the residual radiological footprint of a former colliery: An industrial nuclear archaeology investigation.

Nuclear industrial archaeology utilises radiation mapping and characterisation technologies to gain an insight into the radiological footprint of industrial heritage sites. Increased concentrations of naturally occurring radioactive materials at legacy mine sites are the result of elemental enrichment during coal mining and subsequent combustion. Public safety is of concern around these sites, and therefore, an increased understanding of their associated hazard is essential. Using coincident laser scanning and gamma detection technologies, this study sought to assess the radiological legacy of a coal mine located in Bristol, UK. From this, we can increase our understanding of the residual footprints associated with the local coal mining industry. Samples taken from inside the site were characterised using high resolution gamma spectrometry, wherein the radionuclide content and activities of samples were then quantified. An area of elevated low-level radioactivity was observed at and around buildings believed to belong to the colliery, while Th, U, and K are confirmed at the site from photopeak's of daughter radionuclides. Activities of the radionuclides K-40, U-238, and Th-232 were further quantified during subsequent laboratory analysis. Results highlight an enrichment of naturally occurring radionuclides when compared with global averages for unburned coal. Employing these techniques at further legacy sites would enable an increased understanding of the lasting traces of the coal mining industry, with a focus on NORM enrichment in residual fly ash.

Coal fly ash application as an eco-friendly approach for modulating the growth, yield, and biochemical constituents of Withania somnifera L. plants.

The solid waste known as fly ash, which is produced when coal is burned in thermal power plants, is sustainably used in agriculture. It is an excellent soil supplement for plant growth and development since it contains some desired nutrients (macro and micro), as well as being porous. The present study was done to evaluate the effect of different fly ash levels on Withania somnifera. The present study aimed to assess the impact of various fly ash (FA) concentrations on growth, yield, photosynthetic pigments, biochemical parameters, and cell viability of W. somnifera. The results showed that FA enhanced physical and chemical properties of soil like pH, electric conductivity, porosity, water-holding capacity, and nutrients. The low doses of FA-amended soil (15%) significantly increased the shoot length (36%), root length (24.5%), fresh weight of shoots and roots (107.8 and 50.6%), dry weight of shoots and roots (61.9 and 47.1%), number of fruits (70.4%), carotenoid (43%), total chlorophyll (44.3%), relative water content (109.3%), protein content (20.4%), proline content (110.3%), total phenols (116.1%), nitrogen (20.3%), phosphorus (16.9%), and potassium (26.4%). On the other hand, the higher doses, i.e., 25% of fly ash showed a negative effect on all the above parameters and induced oxidative stress by increasing lipid peroxidation (33.1%) and hydrogen peroxide (102.0%) and improving the activities of antioxidant enzymes and osmolytes. Compared to the control plants, the plants growing in soil enriched with 15 and 25% fly ash had larger stomata pores when examined using a scanning electron microscope. In addition, according to a confocal microscopic analysis of the roots of W. somnifera, higher fly ash concentrations caused membrane damage, as evidenced by an increase in the number of stained nuclei. Moreover, several functional groups and peaks of the biomolecules represented in the control and 15% of fly ash were alcohols, phenols, allenes, ketenes, isocynates, and hydrocarbons. Gas chromatography-mass spectrometry analysis of the methanol extract of W. somnifera leaves cultivated in soil amended with 15% fly ash shows the presence of 47 bioactive compounds. The most abundant compounds in the methanol extract were cis-9-hexadecenal (22.33%), n-hexadecanoic acid (9.68%), cinnamic acid (6.37%), glycidyl oleate (3.88%), nonanoic acid (3.48%), and pyranone (3.57%). The lower concentrations of FA (15%) can be used to enhance plant growth and lower the accumulation of FA that results in environmental pollution.

Dissolution characteristics of uranium and lead in simulated lung fluid using fly ash samples from coal-fired power plants in the Czech Republic.

Samples of fly ash, slag and boiler scale containing elevated amounts of uranium or lead (210Pb) from several coal-fired power stations in the Czech Republic were collected for an assessment of their dissolution parameters - the dissolution rates and their respective fractions in vitro. The dissolution data were fitted either by a biexponential model or by a triexponential model. The uranium 234U and 238U in the fly ash sample are classified as M-type. Similarly, type M could be attributed for most of the materials containing 210Pb. A complementary measurement of the activity concentrations of 210Pb in relation to the grain size confirmed that the radionuclide is deposited mainly in fine particles (<25 µm).

Growth, biochemical, and antioxidant response of pot marigold (Calendula officinalis L.) grown in fly ash amended soil.

The present study was carried out to determine the impact of FA application on growth performance, biochemical parameters, and antioxidant defense activity of Calendula officinalis. The results revealed that under a low dose of FA (40%) amended soil, the plant growth performance and metal tolerance index (MTI) were increased compared to control plants and further decreased with increased FA application (60%, 80%, and 100% FA). In addition, the incorporation of 40% FA in soil not only improved the physicochemical properties of soil but also increased the biochemical parameters in the Calendula plant, however, these parameters declined under high FA applications. It was also observed that antioxidant enzyme activity (SOD, CAT, POD, and APX) in leaves of Calendula officinalis increased at high FA application (100% FA) to combat heavy metal stress from FA. The overall study suggests that 40% FA amended soil is the best suitable dose for growing Calendula officinalis and can be considered as metal tolerant species for phytoremediation of 40% FA amended soil.Novelty statement: Fly ash (FA) management is a major problem nowadays. The present study was carried out for FA utilization and to determine the impact of FA amended soil on growth performance, antioxidant properties, and biochemical attributes of Calendula officinalis. This is a sustainable approach in which waste (FA) utilization was done simultaneously with the enhancement in response of the medicinally potent Calendula species. The novelty of this study also suggests that Calendula has phytoremediation potential for remediation of heavy metal polluted soil. Further, the relationship between the growth, biochemical parameters, and antioxidant defense mechanism of Calendula grown on FA amended soil was studied which has not been studied so far. It was found that Calendula is a hyperaccumulator that can adapt to heavy metal stress from FA due to its ability to mitigate oxidative damage. Statistical analysis (ANOVA, Duncan's multiple range test, and PCA) was done for the results obtained using SPSS (11.5) and Origin 8 Pro software.

Does exposure to weathered coal ash with an enhanced content of uranium-series radionuclides affect flora? Changes in the physiological indicators of five referent plant species.

Coal ash deposited in open landfills is a potential source of environmental pollutants due to the contained toxic element content. The weathered coal ash used in this study additionally contains enhanced activity concentrations of 238U series radionuclides. This study aimed to determine the physiological effects of enhanced ionizing radiation and toxic elements on five plant species (smilo grass, sticky fleabane, blackberry, mastic and pine tree) inhabiting the coal ash disposal site. Among the potentially toxic measured elements, contents of Sb, As and especially V significantly exceeded their respective levels at the control site, as well as the content of 238U and its progenies. Significant changes in photosynthetic pigments were recorded following chronic exposure to the plants growing on the coal ash site. Different responses were also observed in the plant species regarding the activity of catalase and glutathione-S-transferase (GST). The level of lipid peroxidation markedly increased in plants from the disposal site, except in blackberry, wherein GST activity was the strongest, indicating an important role of that enzyme in the adaptation to coal ash pollutants. The results of this study suggest that the modulation of the studied biochemical parameters in plants growing on coal ash is primarily species-dependent.

Immobilization of Pb and Zn in Contaminated Soil Using Alumina-Silica Nano-Amendments Synthesized from Coal Fly Ash.

To apply coal fly ash to the remediation of heavy-metal-contaminated soil, an alumina-silica nano-amendment (ASNA) was synthesized from coal fly ash and was used for the immobilization of lead and zinc in contaminated soil. The investigation on the synthesis of the ASNA shows that the ASNA can be obtained under a roasting temperature of 700 °C, a ratio of alkali to coal fly ash of 1.2:1, and a molar ratio of silicon to aluminum of 1:1. The ASNA could increase the soil pH and cation exchange capacity (CEC) and decrease the bioavailability of Pb and Zn. When the ASNA addition increased from 0 to 2%, the bioavailability (extracted by CaCl2) of Pb and Zn decreased by 47% and 72%, respectively. Moreover, the addition of the ASNA facilitated the transformation of Pb from a reducible fraction to oxidizable and residual fractions and Zn from an exchangeable fraction to a residual fraction. The correlation analysis and cluster analysis verify that the ASNA modulates the chemical speciation of heavy metals by increasing the soil's CEC and pH, thereby immobilizing heavy metals. It is expected that this study can provide a new method for the remediation of Pb- and Zn-contaminated soil.

Migration behavior and leaching ability of radioactive uranium during incineration of uranium-containing strippable coating wastes.

It is currently thought that the incineration approach is an effective method to minimize the volume of radioactive wastes. In this paper, we used an incinerator to burn uranium-containing strippable coating waste. The migration behavior of radioactive uranium during the incineration process were investigated based on hierarchical sampling and mass spectrometry. Results shows that the radioactive uranium is more easily to adhere to the particles with smaller size. The leaching abilities of radioactive uranium in the bottom ash and the fly ash were analyzed. The leaching rate of the uranium from the fly ash and bottom ash were 1% and 6%, respectively, indicating that most of the radioactive uranium was fixed in the ash and the same storage/disposal methods can be used for both the fly ash and bottom ash. According to x-ray spectrometry and SEM-EDS, mineral compositions of the original uranium ore and the bottom ash were mostly the same. Calcium plays an important role in uranium fixation during incineration. The potential mechanism of the uranium special transformation during uranium-containing strippable coating waste combustion was revealed. Our research results can provide technical support for nuclear emergency waste treatment and disposal.

Preparation and related properties of geopolymer solidified uranium tailings bodies with various fibers and fiber content.

Uranium tailing ponds are a potential major source of radioactive pollution. Solidification treatment can control the diffusion and migration of radioactive elements in uranium tailings to safeguard the surrounding ecological environment. A literature review and field investigation were conducted in this study prior to fabricating 11 solidified uranium tailing samples with different proportions of PVA fiber, basalt fiber, metakaolin, and fly ash, and the weight percentage of uranium tailings in the solidified body is 61.11%. The pore structure, volume resistivity, compressive strength, radon exhalation rate variations, and U(VI) leaching performance of the samples were analyzed. The pore size of the solidified samples is mainly between 1 and 50 nm, the pore volume is between 2.461 and 5.852 × 10-2 cm3/g, the volume resistivity is between 1020.00 and 1937.33 Ω·m, and the compressive strength is between 20.61 and 36.91 MPa. The radon exhalation rate is between 0.0397 and 0.0853 Bq·m-2·s-1. The cumulative leaching fraction of U(VI) is between 2.095 and 2.869 × 10-2 cm, and the uranium immobilization rate is between 83.46 and 85.97%. Based on a comprehensive analysis of the physical and mechanical properties, radon exhalation rates, and U(VI) leaching performance of the solidified samples, the basalt fiber is found to outperform PVA fiber overall. The solidification effect is optimal when 0.6% basalt fiber is added.

Variation in chemical composition of MSWI fly ash and dry scrubber residues.

Our society generates extensive amounts of municipal solid waste (MSW), which are mainly incinerated for volume reduction and energy recovery. Though, MSW incineration generates hazardous air pollution control (APC) residues that must be treated and deposited in appropriate landfills. An alternative to landfilling is material recovery, leading to regeneration of valuable products and reducing hazardous waste amounts. The chemical composition of APC residues, stemming from MSW, makes the waste attractive for metal and salt recovery, but its variation makes the development of material recovery processes challenging. This study investigates results from 895 X-ray fluorescence analyses of fly ash and dry scrubber residue samples originating from Norway and Sweden between 2006 and 2020 to explore variation in chemical composition within and between different incineration plants. The average relative standard deviation of elemental concentration in APC residue was estimated to 30% within plants. The variation in elemental concentration between grate fired incineration plants is about half of the average variation within the plants. The study also clarifies compositional differences from APC residues originating from fluidized bed incinerators and grate incinerators. Also, reported concentrations of APC residues from other countries than Sweden and Norway showed significant differences in chemical composition. The presented variations clarifies the importance of holistic approaches for waste valorization processes which can substitute stabilization processes for landfilling.

The Anthropogenic Impact on Indoor Radon Concentrations for Secunda, Mpumalanga Province, South Africa.

ABSTRACT: Secunda is a town built amid the coalfields of the Mpumalanga province of South Africa. Surrounding the town are 11 coal-fired plants (CFPs) contributing around 59% of the country's energy needs. It is also home to Sasol Synfuels, which produces synthetic gas through coal gasification and natural gas reforming. Coal, like most materials found in nature, contains trace elements of the naturally occurring primordial radionuclides 40K, 238U, 232Th, and their decay products. The milling and combustion of coal in a CFP increases the mass concentration of these trace elements, and the residuals end up on ash heaps as fly ash, bottom ash, and boiler slag. A small percentage of fly ash also ends up in the atmosphere. This paper sets out to determine the anthropogenic impact of the industrial activity on indoor radon in the town of Secunda in the Mpumalanga region of South Africa. Measurements were done in 37 homes during July when higher indoor radon levels are expected due to homes typically being closed due to the low temperatures. The average indoor radon concentration was found to be 76.4 Bq m-3. This indicates that the fallout from the industrial activity surrounding Secunda does not enhance the emanation of radon. This may be due to the type of activity or the climate and prevailing winds mitigating its indoor build-up. Measurements during the warmer months and in neighboring towns with different industrial activities are required to confirm the trends established by this research.

Impact of the low and high concentrations of fly ash amended soil on growth, physiological response, and yield of pumpkin (Cucurbita moschata Duch. Ex Poiret L.).

Fly ash, a result of coal burning in thermal power plants, is sustainably used in agriculture and has been regarded as a problematic solid waste worldwide. The presence of some desired nutrients (macro and micro) and its porosity makes it a marvelous soil amendment for plant growth and development. The present study was done to evaluate the effect of different fly ash levels on pumpkin crop (Cucurbita moschata). Pot experiment in randomized block design was conducted with different fly ash supplement treatments to analyze the impact of fly ash on growth, chlorophyll, carotenoid, biochemical parameters, and pumpkin crop yield. The results show variation in soil's physical and chemical properties after the application of fly ash (30 and 50%). Also, the lower levels (10-30%) of fly ash amended soil significantly (P ≤ 0.05) enhanced the growth (plant height, plant fresh and dry biomass, no. of leaves, and average area of the leaf), chlorophyll content, and biochemical contents (protein, carbohydrate, mineral, and leaf water content) in pumpkin crop. The proline content was also observed to enhance by the increasing levels of fly ash to soil. The yield parameters in terms of a number of flowers and fruits, fruits' length and diameter, and fresh and dry weight of fruits were also significantly increased in amended soil with 10-30% fly ash. On the other hand, the higher doses, i.e., 40% and 50% of fly ash showed a negative effect and reduced the growth, chlorophyll, carotenoid, biochemical content, proline, and yield in pumpkin crop. We concluded that the lower level of fly ash (up to 30%) could be used as fertilizer in agricultural fields for the improvement of vegetable as well as other food crops in a sustainable manner but the higher level of fly ash (40 and 50%) is toxic to the plant.

Isothermal drying kinetics of sewage sludge using weathered coal fly ash as adjuvant for agronomic application.

This study aims to evaluate the effect of weathered coal fly ash (CFA) as a drying adjuvant of sewage sludge (SS) to produce a soil amendment. The high amount of SS and CFA creates a complex waste management problem in many countries, requiring more research efforts. Towards a circular economy, CFA can be viewed as an anthropogenic inorganic by-product with valuable nutrients (e.g. K), which can be recovered in combination with SS (rich in organic matter, N, and P). Different temperatures (70, 85, 100, 115, and 130 °C) are tested to dry small SS cylinders, without and with 0.15 g CFA g-1 of SSwet basis (wb). By fitting appropriate models to the experimental drying curves, it is possible to observe an improvement of 1-17% in the diffusion coefficient and 7-19% in the kinetic constants, using CFA. The best drying conditions are achieved with CFA as an adjuvant at 130 °C, where the drying rate is 31.61 gH2O kg-1 SSwb min-1. Phytotoxicity and growth assays are performed to evaluate the effect of the produced materials in the soil. The product with SS and CFA shows the potential to improve soil condition due to (i) the organic matter, N, P, and K content, (ii) the lower phytotoxic effect when compared to raw SS; (iii) the soil pH correction. Thus, not only the addition of weathered CFA facilitates the drying of SS but also the final product has benefits to soil conditions.

Selective sulfur removal from semi-dry flue gas desulfurization coal fly ash for concrete and carbon dioxide capture applications.

High-sulfur mixed fly ash residues from semi-dry flue gas desulfurization units in coal-fired power plants are unsuitable for use as supplementary cementitious material (SCM) for concrete production or carbon dioxide utilization. In this work, we explore the potential for upcycling a representative spray dry absorber ash (10.44 wt% SO3) into concrete-SCM by selective sulfur removal via weak acid dissolution while simultaneously exploring the possibility for CO2 capture. Towards this effort, parametric studies varying liquid-to-solid ratio, acidity, and CO2 pressure were conducted in a batch reactor to establish the sulfur removal characteristics in de-ionized water, nitric acid, and carbonic acid, respectively. The dissolution studies show that the leaching of sulfur from calcium sulfite hemihydrate, which is the predominant S phase, is rapid and achieves a concentration plateau within 5 min, and subsequently, appears to be controlled by the primary mineral solubility. Preferential S removal was sufficient to meet SCM standards (e.g., 5.0 wt% as per ASTM C618) using all three washing solutions with 0.62-0.72 selectivity (S^), defined as the molar ratio of S to Ca in the leachate, for a raw fly ash with bulk S^ = 0.3. Acid dissolution with 1.43 meq/g of ash or under 5 atm CO2 retained > 18 wt% CaO and other Si-, Al-rich phases in the fly ash. Based on the experimental findings, two sulfur removal schemes were suggested for either integration with CO2 capture and utilization processes using flue gas or to produce fly ash for use as a SCM.

Utilisation of ultrasonic treatment to improve the soil amelioration property of coal fly ash.

Environment-friendly disposal of coal fly ash (CFA) is essential for sustainable development and cleaner production of electricity in thermal power plants. Although CFA has been employed for soil amelioration, direct application of CFA to soil may pose risks such as heavy metal contamination. This study investigated recycling of CFA through a novel method, which employs the ultrasonic treatment of CFA before its application. Physico-chemical properties of refuse dump soil and CFA were analysed. Subsequently, the effect of ultrasonic treatment on the physico-chemical properties of CFA was investigated. Different ultrasonic parameters (ultrasonic frequency, time interval, and temperature) were studied using response surface methodology. Finally, plant growth experiments were conducted to verify the feasibility of using ultrasonically treated CFA (UTCFA) for soil amelioration. The results show that untreated CFA cannot be used for soil amelioration due to its unsuitable high pH (10.20) and threatening concentrations of trace elements (6.80 mg/kg for Cadmium and 109.75 mg/kg for Arsenic). Ultrasonic treatment increases the soil amelioration properties of CFA by decreasing pH (to 8.50-9.20), decreasing concentrations of Cadmium and Arsenic (satisfying GB 15618-2018), and improving the water-holding capacity of CFA (reducing water loss). Plant indicators confirm the feasibility of using UTCFA for soil amelioration and suggest that the optimum UTCFA proportion is 20%. This study is a benchmark for the utilisation of ultrasonic treatment to improve the soil amelioration properties of CFA.

Quantification of U, Th and specific radionuclides in coal from selected coal fired power plants in South Africa.

Most of South Africa's energy is derived from the combustion of coal in pulverized coal-fired power plants (CFPP). However, when compared with the rest of the world, limited information regarding the main radioactive elements (U and Th) and specific radionuclides of interest (K40, Ra226 and Th232) from South African CFPP is available in the public domain. This paper aims to quantify the U, Th and specific radionuclides found in the coal used in selected South African CFPP in comparison to world averages found in literature. The U and Th concentrations were obtained by ICP-MS. The main radionuclides, K40, Ra226 and Th238, were quantified using gamma spectrometry. The U concentration and Th concentrations for the coal used in all the power plants was above the world average of 1.9 mg/kg and 3.2 mg/kg respectively. The coals with the highest Th content originated from the Mpumalanga power plant, while the U content in the Freestate power plant samples was the highest of the three. The concentrations of the K40 were between 88.43±10.75-110.76±8.92 Bq/kg, which are in-line with world averages of 4-785 Bq/kg. Similarly, the Ra226 and Th232 values were between 21.69±2.83-52.63±4.04 Bq/kg and 19.91±1.24-22.97±1.75 Bq/kg respectively, which are also in line with the world averages of 1-206 Bq/kg and 1-170 Bq/kg respectively. Radiological hazard indices such as radium equivalent (Raeq); external hazard index (Hex) and internal hazard index (Hin), that were estimated from these average radionuclide concentrations were less than the prescribed values found in literature. This indicated that no significant health risk was posed by the coal being used from these coal fields.

Implications of iron nanoparticles in spontaneous coal combustion and the effects on climatic variables.

Atmosphere, water, and soil contamination with toxic compounds is a recurrent issue due to environmental disasters, coal burning, urbanization, and industrialization, allf of which have contributed to soil contamination over the decades. Consequently, understanding of the nanomineralogy and potential hazardous elements (PHEs) in coal area soil are always a vital topic since contaminated soil can affect the environment, agricultural safety, and human health. Colombian coal mining in the La Guajira zone has been usually been related with important health and ecological effects. Coalmine rejects from active and/or abandoned operations are causes of high intensities of potential hazardous elements (PHEs) and nanoparticles (NPs, minerals and/or amorphous compounds). Although these pollutants can be reduced by sorption to NPs, in this study was recognized an analytical procedure for understand distribution of PHEs and their relationship to iron NPs(Fe-NPs) was recognized. Non and poorrly crystalline Fe-NPs performances as the major PHEs association. This complex interaction is constant and efficient in resolving PHEs in proportions above monitoring quantities. The indefinite basis of PHEs in Colombian (La Guajira area) coalmine rejects sources results in years-long leaching of PHEs into rivers and drainages. The iron-clays and their great geomobility interfere the mitigating character that Fe hydr/oxides alone show through adsorption of PHEs and their control in spontaneous coal combustion (SCC) zones. This can have significant consequences to the probable availability of several pollutants (e.g. drinking water). The new results presented in this study add novel viewpoints into the description of Fe-NPs and its incidence in SCC areas. The methodology utilized in this work can be applied as a supplementary technique to evaluate the influence of coalmining actions on ecological and human health.

Accelerated screening of arsenic and selenium fractions and bioavailability in fly ash by microwave assistance.

Huge amounts of fly ash (FA) can be annually produced in power plants. Fly ash always contains high levels of arsenic (As) and selenium (Se) due to the preconcentration of these two elements during coal combustion process. It would be much concerned to screen their fractions and potential environmental behaviors in fly ash for beneficial use and treatment. Fast and practical methods for this purpose are urgently needed. Two fast and effective microwave-assisted sequential extraction schemes (MASE) were developed for fast screening As and Se fractions in fly ash for the first time. The extraction parameters including microwave irradiation time, temperature and power energy were optimized by comparing the results from MASE and the conventional scheme (Wenzel method). The results indicate that the extraction efficiency of As and Se in various fractions can be significantly accelerated by microwave irradiation. The whole procedure operation time can be significantly reduced from 24.5 h to 44 min by microwave assistance compared with the conventional shaking schemes. The recoveries of As and Se in the various extracted fractions were all above 80% with relative standard deviations (RSDs) below 8%. The developed methods were further confirmed by the validation of the certified reference material GBW08401 and fly ash samples from six power plants. The developed MASE methods are practical and effective for fast screening arsenic and selenium fractions in fly ash samples.

Effects of electrostatic precipitators ash leachate (EPAL) from recovery boilers on the biological treatment of effluent of kraft pulp mills.

The electrostatic precipitators ash leachate (EPAL) from recovery boilers of kraft pulp mills is generated in processes dedicated to the removal of potassium and chloride salts seeking to avoid fouling and corrosion in pipes and equipment. However, the EPAL is rich in salts and has high electrical conductivity. Whenever it is sent to the effluent treatment plant (ETP), it can cause negative impacts to the biological process. It may jeopardize particularly the microbial community and the sludge bio-flocculation, causing sludge losses in the secondary clarifiers, reducing the overall efficiency of the effluent treatment plant. The objective of this research was to evaluate the influence of EPAL from the recovery boilers added to a typical effluent from a bleached eucalyptus kraft pulp mill in gradually increased doses and in sudden doses (shock loads) in the efficiency of the biological treatment. Three biological sequential batch reactors (R1, R2, R3) with a volume of 1000 ml each were tested. The Reactor R1 was operated as a reference and fed only with typical effluent from the pulp mill; Reactor R2 was fed with mill effluent with gradually increased doses of EPAL in fixed proportions until reaching a real industrial condition; Reactor R3 was fed with mill effluent and with sudden doses of EPAL. The reactors were operated in similar conditions, i.e., the concentration of dissolved oxygen (DO) was always kept higher than 2 mg L-1, COD:N:P ratio equal to 250:5:1 and hydraulic retention time of 12 h. Depending on the dose which was applied, the EPAL inhibited microbiological activity, reduced the efficiency of COD removal of the biological treatment (10% when EPAL was gradually applied and 15% in sudden doses) and increased the sludge carryover in the sedimentation phase (148% when EPAL was gradually applied and 170% in sudden dosages). Furthermore, the reduced efficiency and suspended solid carryover were more significant when sudden doses were applied compared to the application of gradual doses of the EPAL.

Experimental study and simulation of phosphorus purification effects of bioretention systems on urban surface runoff.

Excessive phosphorus (P) contributes to eutrophication by degrading water quality and limiting human use of water resources. Identifying economic and convenient methods to control soluble reactive phosphorus (SRP) pollution in urban runoff is the key point of rainwater management strategies. Through three series of different tests involving influencing factors, continuous operation and intermittent operation, this study explored the purification effects of bioretention tanks under different experimental conditions, it included nine intermittent tests, single field continuous test with three groups of different fillers (Fly ash mixed with sand, Blast furnace slag, and Soil), and eight intermittent tests with single filler (Blast furnace slag mixed with sand). Among the three filler combinations studied, the filler with fly ash mixed with sand achieved the best pollution reduction efficiency. The setting of the submerged zone exerted minimal influence on the P removal of the three filler combinations. An extension of the dry period slightly promoted the P purification effect. The combination of fly ash mixed with sand demonstrated a positive purification effect on SRP during short- or long-term simulated rainfall duration. Blast furnace slag also presented a positive purification effect in the short term, although its continuous purification effect on SRP was poor in the long term. The purification abilities of soil in the short and long terms were weak. Under intermittent operations across different seasons, SRP removal was unstable, and effluent concentration processes were different. The purification effect of the bioretention system on SRP was predicted through partial least squares regression (PLS) modeling analysis. The event mean concentration removal of SRP was positively related to the adsorption capacity of filler and rainfall interval time and negatively related to submerged zones, influent concentration and volume.

Potential application of pre-treated municipal solid waste incineration fly ash as cement supplement.

Pre-treatment process carried out on raw municipal solid waste incineration (MSWI) fly ash (FA) sample that did not comply initially with the USEPA method 1311 toxicity characteristic leaching procedure (TCLP) regulatory limits of 2011 reduced its chloride and heavy metal content appreciably, thereby making it compliant with the aforementioned regulatory requirement. More than 98% of each heavy metal was successfully removed. The process was excellent in removing cadmium (Cd) (99.99%) and very good at removing the rest. About 99.96% of Cu was eliminated, 99.96% of cobalt (Co), 99.95% of Zn, 98.61% of Cr, and 98.12% of nickel (Ni). Also, the leachate resulting from these pre-treatment steps met the China (GB 16889-2008) and USEPA method 1311 regulatory standards for safe discharge. The density and compressive strength of all the samples prepared increased as the FA content decreased. The compressive strength of all the samples passed the 1989 USEPA-recommended value of 0.34 MPa (50 psi), thereby making them suitable for industrial application. The sample that attained the highest compressive strength (2.08 MPa) after 28 days of curing incorporated 55% fly ash (FACS55), while the one with the least compressive strength (0.65 MPa) after the same period was made from only fly ash (FACS100). Moreover, the concentration of heavy metals in all the samples generally decreased with the FA content. Chromium was not detected in all the samples, thereby making this an excellent method for its immobilization. From the leachability test results, all the samples prepared met the USEPA method 1311 TCLP regulatory limits.