Slag Filter Research Articles

Characterizing moisture occurrence state in coal gasification fine slag filter cake using low field nuclear magnetic resonance technology

ABSTRACT Gasification fine slag, a carbon-rich solid waste produced during coal gasification, is currently disposed of through conventional landfilling methods. Its high-water content hampers resource utilization by reducing its calorific value. This study employs low field nuclear magnetic resonance (LF-NMR) analysis to investigate the water occurrence states in a filter cake with 70.7% moisture content derived from fine gasification slag of the Ningxia coal water slurry furnace. The analysis reveals that free water constitutes a major proportion (68.28%), while combined and capillary water accounts for 2.62% and 2.33%, respectively. The removal of moisture from the coal gasification fine slag filter cake is significantly affected by the drying temperature. The drying rate initially increases and then decreases with different temperatures. For drying temperatures of 60, 70, 80, 90, and 100°C, the maximum drying rates are achieved at 1.09, 1.23, 2.18, 3.86, and 4.01%/min, respectively, with corresponding durations of 40, 40, 25, 30, and 35 min. The T22 relaxation peak area continually decreases and shifts leftward on the coordinate axis. The behavior of the T23 and T22 peaks follows a similar pattern, indicating that water with higher mobility is easily eliminated during drying, while the T21 peak exhibits a robust signal strength throughout the drying process. At a drying temperature of 100°C, the proportion of free water (A22) decreases from 87.3% to 0, the A23 fluctuates between 0 and 5.3%, and the bound water peak area (A21) increases from 10.4% to 94.7% as drying time prolongs. A relationship model is developed between the moisture content of the coal gasification fine slag filter cake and the total integral area of the LF-NMR test, enabling rapid detection and analysis of the total moisture content and distinct occurrence states in the filter cake.

Steel Slag and Limestone as a Rock Filter for Eliminating Phosphorus from Domestic Wastewater: A Pilot Study in a Warm Climate

Phosphorus input with excessive use of fertilizers and manure as one of the main sources of nutrient pollution has increased recently in the wastewater as result of intensive farming and industrialized and densely populated areas. The novelty of the current work lies in improving a Vertical Aerated Rock Filter (VARF) using steel slag and limestone media to enhance the efficiency of a rock filter (RF) to eliminate total phosphorus (TP) from domestic wastewater. RF was designed with steel slag and limestone (calcium hydroxide) as a pilot scale called vertical aerated steel slag filter (VASSF) and optimized based on hydraulic loading rates (HLR) (0.16 to 5.44 m3/m3 day) and airflow rates ranging from 3 to 10 L/min. The highest removal for the design of the laboratory scale steel slag filter (LSSSF) was achieved by approximately 58%, while for the laboratory-scale limestone filter (LSLSF), it was 64%. The VASSF achieved a removal percentage at 30% of TP, biological oxygen demand (BOD; 89%), chemical oxygen demand (COD; 75%), total suspended solids (TSS; 73%), and total coliforms (TC; 96%), recorded with 7 L/min of an airflow rate and 1.04 m3/m3.day of hydraulic loading rate (HLR) at potential of hydrogen (pH) 7.3 and 5.09 mg/L of dissolved oxygen (DO). These findings indicated that the steel slag is higher than limestone in TP removal, because of ion exchange between phosphorus hydrolysis and the adsorption process. Moreover, in the pilot study, the removal efficiency needs more investigation to determine the best conditions for TP considering the temperature, which is unstable, and presence of other pollutants, which might negatively affect the removal efficiency under unstable conditions.

Determination of Phosphorus Removal Mechanism in Aerated and Unaerated Steel Slag Filter System as Secondary Treatment System for Textile Industrial Wastewater

Phosphorus is the element that promotes growth in plant. However, over loading of phosphorus into surfaces water leads to severe environmental problems known as eutrophication. Improper treatments of phosphorus removal prior discharges from industrial effluent are one of the contributions to eutrophication. Textile effluent is one of the sources of phosphorus loading in surface water with concentration of 1-9 mg/L P. Since attentions are given in removing the color from the effluent, phosphorus is commonly ignored in wastewater treatment system. Thus, the study of phosphorus removal in textile wastewater is conducted using steel slag system filter under aerated (ASSF) and unaerated (USSF) condition. The systemwas set up for influent pHrange of 5.30-7.00 at primary treated wastewaterfor textile wastewaterunder aerated and unaerated condition. Sampling was done twice a week for 12 weeksand analyzed for Total phosphorus concentration. The Activated Carbon(ACF)filterin the existing treatment system is also sampled to compare the removal efficiency The USSFfilter shows better removal than ASSFfilter with46% to 70%of efficiency removal.Meanwhile, the removal efficiency of ASSF is 37% to 66%.The adsorbate formed in ASSF is analyzed using SEM-EDX and the precipitation formed in USSF is analyzed using XRD.This shows that steel slag filter provides promising result in phosphorus removal.

Retention of phosphorus in soils receiving bunker silo effluent

The eutrophication of freshwater systems is a pervasive issue in North America and elsewhere, which has been linked to elevated phosphorus (P) loading from watersheds. Most excess P is thought to originate from non-point agricultural sources, and less attention has been given to small rural point sources, such as bunker silos on livestock farms. Sophisticated management practices are rarely used to attenuate nutrients from bunker silo effluent, leaving simple vegetated buffer strips or riparian zones to protect surface water; however, the efficacy of these systems or larger constructed treatment systems is unclear. This study compared two systems receiving bunker silo effluent, one a natural riparian system with a vegetated buffer strip that is the most common practice and the other a constructed treatment system with a forebay, slag filter, and swale. The study quantified P retention within various subsections of each system and characterized the forms of stored P to infer the potential for remobilization. Results indicate that soils receiving bunker silo effluent represent considerable stores of legacy P in the landscape (750 and 3400 kg ha−1), the majority of which is stored in labile forms that may be vulnerable to remobilization under the waterlogged conditions that often occur in management practices and riparian zones. Some areas of the systems were able to store considerably more P than others, with the slag filter showing the greatest treatment efficacy. Spatial variability in stored P was apparent, where sections of the systems that directly received effluent retained more P than sections located farther away from bunker silos (indirect inputs). Results indicate that passive treatment systems become P saturated over time, limiting their longterm P removal efficacy. The efficacy of these systems may be improved with the inclusion of sorptive materials as a slag filter within the constructed treatment system significantly increased the life expectancy of that system. Greater understanding of both quantity and forms of P retained in systems and soils receiving bunker silo effluent will help develop management strategies that are more effective and longer-lasting for reducing excess P losses to surface water bodies.

Removal of Phosphorus from Domestic Wastewater by Using L-shape Semi Aerated Steel Slag Filter System

Excessive amount of phosphorus in wastewater prior discharged are one of the major cause of eutrophication in lakes and rivers making phosphorus removals are essentials. However, removing phosphorus from wastewaters required a high cost treatment system to be installed at treatment facilities. To provide alternative solutions, this study was conducted to investigate the effectiveness of L-shape semi aerated filter with steel slag as filter media to provide a cost effective treatment system using natural media as a solution to remove phosphorus from domestic wastewater. The L-shaped semi aerated filter was constructed and installed onsite at Sewage Treatment Plant (STP) UTHM. Then, the laboratory test was conducted twice a week to analyse five parameters including pH, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), and total phosphorus (TP). The results showed that the effluent from the L-shape steel slag filter was alkaline with a pH value range of 7.22 to 9.71 due to alkaline properties of steel slag. Turbidity value of effluent at vertical section was higher than horizontal section as it may affect the COD removal of the filter. In the vertical system, the DO value range was higher (1.5 to 6.9 mg/L) than the horizontal system (1.27 to 5.5 mg/L) since oxygen was introduced by aeration process. Furthermore, this system showed good COD removal efficiencies with values ranged from 10% to 76%. Lastly, total phosphorus removal efficiencies also showed great removals with range of 29% to 68%. From the results obtained, steel slag with high-Ca content showed excellent potential in removing phosphorus from domestic wastewater.

Reduction of Phosphorus Using Electric Arc Furnace Slag Filters in the Macatawa Watershed (Michigan)

Eutrophication is a major problem in lakes and rivers throughout the world. One such system is Lake Macatawa, located in West Michigan, which hydrologically connects to Lake Michigan. Lake Macatawa and its watershed suffer from excess phosphorus and sediment loads. The total maximum daily load for the lake calls for a total phosphorus (TP) reduction of 75%, which would reduce the water column total phosphorus concentration from 125 μg/L to 50 μg/L. Understanding how P moves through this landscape, into Lake Macatawa, and ultimately to Lake Michigan and the St. Lawrence Seaway, is critical to managing and controlling P runoff. A potentially significant source of P to Lake Macatawa occurs through agricultural tile drainage. Various best management practices (BMPs) have been implemented in the Macatawa watershed to reduce P loading, especially surface runoff, but their overall effectiveness has been limited. Electric arc furnace (EAF) slag, a waste product from the steel industry, can chemically bind P and has been used previously in agricultural settings. Three iron slag filters were installed at the end of agricultural tile lines in the Macatawa watershed and evaluated to assess their effectiveness in removing P, while also monitoring for the presence of potentially toxic chemicals leaching from the slag. After 1 year of slag filter performance, both SRP (soluble reactive phosphorus) and TP decreased in the tile drain effluent: percent reductions of soluble reactive phosphorus and TP ranged from 7.4% to 57.3% and 59.5–76.5%, respectively. Absolute concentrations of TP were reduced to between 100 and 329 μg/L, which still exceeds the 50 μg/L goal for Lake Macatawa. Concentrations of toxic metals, polycyclic aromatic hydrocarbons compounds, and cyanide all were at levels below drinking water standards. Our preliminary conclusions are that the installation of these filters should be targeted to areas where tile drain effluent P levels are very high (SRP > 250 μg/L) to obtain an optimal cost/benefit ratio. While they are not a panacea, when installed in combination with other BMPs (Best Management Practices), EAF slag filters may play an important localized role in reducing P to Lake Macatawa and farther downstream.

Study of Steel Slag Filter Unit as a Secondary Treatment System for Removing Total Phosphorus from Textile Industry Wastewater

Eutrophication is one of the global concerned due to algae bloom in the natural surface water such as lakes and swamp area. Industrial effluent with incomplete treatment discharged has become one of the main culprits to this phenomenon. Approximately, 0.3 – 13 mg/L of total phosphorus can be found in the final discharge of industrial effluent showing that the existing treatment including an activated carbon filter (ACF) has limitation in polishing the phosphorus. Therefore, this 16 week of study has been designed to study the alternative treatment phosphorus removal at secondary stage to replace the tertiary treatment by using steel manufacturing by-product as filter media for effective phosphorus removal from the textile industry wastewater. Two units of lab-scale vertical steel slag filter (SSF) systems under aerated and unaerated conditions have been developed for this study. The samples were collected and analysed biweekly for selected parameters including pH, alkalinity, DO and TP. The results obtained from this study show that the unaerated steel slag filter has a high efficiency of TP removal which ranged from 46% to 70% compared to the aerated SSF with removal efficiency ranged from 37% to 66%. Besides, the existing ACF removal efficiency was ranged from 36% to 54%. Thus, the use of steel slag in removing phosphorus from textile wastewater is possible with the used of both aerated and unaerated steel slag filter systems. Furthermore, the removal mechanism involved was likely to be precipitation and adsorption.

Insights on water temporal-spatial migration laws of coal gasification fine slag filter cake during water removal process and its enlightenment for efficient dewatering

Coal gasification fine slag is a kind of industrial waste produced from coal gasification process, and high-moisture coal gasification fine slag filter cake has brought challenges to environment and coal energy suatainable development. It is an important prerequisite for the development of fine slag efficient dewatering technology to investigate the water migration laws during the water removal process. In this study, the volume of water was ~56.95% of the filter cake according to the advanced micro-CT analysis which shows the spatial distribution information of water. The non-freezable water in the gasification fine slag filter cake occupied ~13 wt% which requires more energy to achieve the removal of this part of water. The larger water pore in the filter cake evolved into smaller pores in the drying process was confirmed which provides information for water migration behavior among pores. During the heating process, the change of weak hydrogen bonds intensity is more obvious than that of strong hydrogen bonds at the initial stage, implying that the different types of water have differences in the removal process. The hydrogen bond energy at 85 °C exceeds 40 kJ/mol, which is twice of that at 80 °C, indicating that more effective dewatering energy would be required in the future to remove water with strong hydrogen bonds. The investigations of water migration behavior and dewatering energy consumption provide potential guidance for efficient dewatering of gasification fine slag, which benefits to the environment and energy security.

Optimizing vertical flow aerated steel slag filter system with nitrifiers bacteria for nutrients' removal from domestic wastewater: a pilot study

AbstractBACKGROUNDThe present study aimed to optimize the removal efficiency of ammonia nitrogen (NH3‐N) and total kjeldhal nitrogen (TKN) from domestic wastewater as a function of hydraulic loading rates (HLRs) (0.16–5.44 m3 m–3 day–1) and the aeration rate (3, 5 and 10 L min–1) in a vertical flow aerated steel slag filter (VFASSF) system with nitrifier bacteria. The nitrifier bacterial cell morphology was determined using scanning electron microscopy (SEM) analysis.RESULTSThe HLRs affected the performance of the VFASSF in removing TKN and NH3‐N from domestic wastewater. The optimal air flow rate for removing NH3‐N and TKN was recorded with 10 L min–1 and HLR 2.72 m3 m–3 day–1, at which the removal efficiency was >91% compared to 90% and 88% with 3 L min–1 and 5 L min–1 air flow rate, respectively. The high removal was a consequence of the high aeration which enhances the nitrification process performed by the nitrifying bacteria in the VFASSF.CONCLUSIONSThese findings reflected the applicability of VFASSF in the treatment and removal of nutrients from domestic wastewater. © 2020 Society of Chemical Industry

Occurrence modes of water in gasification fine slag filter cake and drying behavior analysis——A case study

Coal gasification fine slag is one of the major industrial wastes produced from coal gasification technology and its landfill disposal of the high-moisture product has brought harmful environmental impacts. The characteristic of water occurrence modes in gasification slag filter cake has positive effects on guiding high-efficiency dewatering processes which benefits to the environment. Gasification fine slag particles and water exist simultaneously in the gasification fine slag filter cake, and the physicochemical properties of the gasification fine slag have significant influences on the water occurrence mode and the effective dewatering process. The hydrophilic components and abundant macropores in the gasification slag are favorable for water occurrence. The water in the gasification fine slag filter cake was classified according to the freezing types and size distribution by low-temperature DSC and LF-NMR, respectively. ∼86 wt% of total water corresponding to the free water form which would be removed first during drying process. The visualization of water was determined by three-dimensional reconstruction technology, there are distinct water channels in the gasification fine slag filter cake from the direction in which the filter cake is formed, and the volume of water was estimated at ∼56 %. The drying behaviors were tested by TGA with the heating rates of 2, 7, and 15 K/min, and the maximum drying rate and critical water content increased as the increasing heating rates. The two-dimensional growth kinetic model was applied for describing the drying kinetic process, and the activation energy decreased as the increasing heating rate, and the drying rate reduction stage has higher activation energy compare to the increasing and constant drying stage.

Use of slag-media filter for treating drinking water

Filtration is a very important process for all domestic water supply systems. Prior to filtration, screening and sedimentation processes will remove large proportion of suspended matter, but they do not effectively remove fine floc particles, colour, dissolved minerals and microorganisms. Often river sand is used as a filter media for domestic water treatment. As river sand is getting depleted, it is apt to have an alternative or substitute material (in place of sand) for treatment of domestic water supply. With this motivation some of the feasible and economical solutions that have emerged in recent years are to reuse the industrial process wastes. Among the various alternatives considered, the materials which are close to meeting the quantity demand of the filter media aggregates are slag, from ferrous industries. In this study, the filtration efficiencies of conventional sand and granulated slag filter media are compared by passing three known concentration of synthetic solutions having a total suspended solids concentration i.e. TSS= 160 mg/L, 210 mg/L and 370 mg/L respectively at a known infiltration rate i.e. 4l/hr. The filters were backwashed periodically. The efficiency of conventional sand filter and granulated slag filter were studied by measuring outflow water flux and head loss occurring in both the filter columns.

Efficiencies and mechanisms of steel slag with ferric oxides for removing phosphate from wastewater using a column filter system.

The current study aimed to investigate the efficiencies and mechanisms of slag filter media for removing phosphorus from synthetic wastewater. The steel slag with high ferric oxides (Fe2O3) was subjected for the electric arc furnace (EAF) and selected as the filter media (HFe). The chemical characteristics of HFe were determined using pH, point of zero charge (PZC) and XRF. The phosphorus removal efficiency was studied in a designed vertical steel slag column rock filters in unaerated HFe (UEF) and aerated HFe (AEF) system. The microstructure of HFe was analyzed by FTIR, XRD and SEM-EDX analysis. The results of XRF revealed that ferric oxide (Fe2O3) ranged from 26.1 to 38.2%. PZC for Filter HFe was recorded at pH 10.55 ± 0.27. The highest efficiencies were recorded by UEF and AEF systems at pH 3 and pH 5 (89.97 ± 4.02% and 79.95 ± 6.25% at pH 3 and 72.97 ± 8.38% and 66.00 ± 12.85% at pH 5 for UEF and AEF, respectively). These findings indicated that AEF exhibiting higher removal than UEF systems might be due to presence high Fe concentration in AEF which play important role in the phosphorus removal. The main elements available on the surface of HFe included carbon, oxygen, iron, calcium, magnesium, silicon, platinum, sulphur, manganese, titanium and aluminium. The XRD analysis indicated that the precipitation of orthophosphate as calcium and iron-phosphates was the removal mechanism as confirmed using FT-IR analysis. These findings demonstrated the efficiency of HFe in removing of phosphorus from wastewater.

Chemical Clogging and Evolution of Head Losses in Steel Slag Filters Used for Phosphorus Removal

The objective of this study was to propose a conceptual model of clogging in alkaline granular filters. Two slag columns were operated for 600 days and monitored using piezometers and tracer tested at regular intervals. The type of influent (organic or inorganic) affected the loss of effective porosity in the filters. Well organized and loose crystal structures were observed by scanning electron microscopy in columns with inorganic and organic influents, respectively. It was postulated that the formation of crystals in unorganized structures results in confined voids that are not accessible for water flow, thus accelerating porosity loss. The effect of the combination of chemical clogging and biofilm on the porosity loss is higher than the effect of these two factors separately. The Kozeny-Carman equation for hydraulic conductivity could not efficiently predict the evolution of head losses in the column fed with an inorganic influent. The crystal structure and connectivity in the presence of homogeneous or heterogeneous precipitation are concepts that could improve predictions of hydraulic conductivity. The results of this study highlighted the importance of the inlet zone on the development of pressure head in alkaline granular filters. Future research on clogging should focus on precipitation mechanisms in the inlet zone and on the design of the feeding system.

Phosphorus Removal and Carbon Dioxide Capture in a Pilot Conventional Septic System Upgraded with a Sidestream Steel Slag Filter

The objective of this work was to demonstrate the removal of the phosphorus and carbon dioxide capture potential of a conventional septic system upgraded with a sidestream steel slag filter used in recirculation mode. A pilot scale sidestream experiment was conducted with two septic tank and drainfield systems, one with and one without a sidestream slag filter. The experimental system was fed with real domestic wastewater. Recirculation ratios of 25%, 50% and 75% were tested. Limestone soils and non-calcareous soils were used as drainfield media. The tested system achieved a satisfactory compromise between phosphorus removal and pH at the effluent of the septic tank, thus eliminating the need for a neutralization step. The phosphorus removal efficiency observed in the second compartment of the septic tank was 30% in the slag filter upgraded system, compared to −3% in the control system. The slag filter reached a phosphorus retention of 105 mg/kg. The drainfield of non-calcareous soils achieved very high phosphorus removal in both control and upgraded systems. In the drainfield of limestone soil, the slag filtration reduced the groundwater phosphorus contamination load by up to 75%. The removal of chemical oxygen demand of the drainfields was not affected by the pH rise induced by the slag filter. Phosphorus removal in the septic tank with a slag filter was attributed to either sorption on newly precipitated calcium carbonate, or the precipitation of phosphate minerals, or both. Recirculation ratio design criteria were proposed based on simulations. Simulations showed that the steel slag filter partly inhibited the biological production of carbon dioxide in the septic tank. The influent alkalinity strongly influenced the recirculation ratio needed to raise the pH in the septic tank. The recirculation mode allowed clogging mitigation compared to a mainstream configuration, because an important part of chemical precipitation occurred in the septic tank. The control septic tank produced carbon dioxide, whereas the slag filter-upgraded septic tank was a carbon dioxide sink.

Aerated and unaerated steel slag filter systems as polishing unit for phosphorus removal from textile industrial effluent

Improper tertiary treatment of industrial effluent discharged causes an excessive phosphorus input which leads to eutrophication. Excessive growth of algae will degrade the natural ecosystem of surface waters. Conventional treatment such as activated carbon filter used as a polishing unit in the tertiary treatment is unable to eliminate the phosphorus completely. Approximately, 0.3–15 mg/l of phosphorus still presents in the final discharge of industrial effluent. Therefore, this study is conducted to provide alternative solutions using natural treatment with cost saving materials to further remove phosphorus from the textile industrial effluent. Aerated and unaerated lab-scale steel slag filters systems were run for 12 weeks at water treatment plant. The sample collected was analyzed twice a week for the parameters of pH, alkalinity, temperature, dissolved oxygen, total phosphorus, chemical oxygen demand, and total suspended solid. The results of this study showed that the unaerated steel slag filter (USSF) has a high percentage of phosphorus removal compared to aerated steel slag filter (ASSF) which is 55% to 86% while ASSF have removal efficiency of 52% to 71%. However, the removal efficiency of activated carbon filter (ACF) used in treatment plant is slightly better than ASSF which is 52% to 81%. The mechanism of removal involved is likely to be through adsorption.

Phosphorus Removal from Textile Industrial Wastewater using Aerated High Calcium Steel Slag Filter System

Phosphorus in wastewater accelerates eutrophication in water body. Textile wastewater is one of contributors to the phosphorus loading into water body which promotes the growth of algae, reducing the oxygen content and detrimental to surface water ecosystem. Myriad existing treatments for phosphorus removal have been developed but it requires a high cost treatment and maintenance. Rock filter system emerged as one of the alternative method for phosphorus removal from wastewater with steel slag as the filter media. However, application of the system in treating industrial wastewater is still unclear especially in big scale application and requires extensive study. This study is done to provide solution of phosphorus loading from textile wastewater using steel slag as filter material and to investigate the removal capacity of steel slag with high calcium and low ferum content. The steel slag was analyzed using XRF for its composition and to ensure the steel slag has high Ca content. Then, the aerated steel slag filter system was set-up on the site of textile industry for a month and analyzed according to parameter of pH, alkalinity, COD, DO, temperature and TSS. The result from this study showed that the aerated high calcium low ferum steel slag filter has a high efficiency of phosphorus removal rates varied from 35% to 67% in treating textile wastewater. It was found that aerated steel slag system was efficient in phosphorus removal by using industrial wastewater.

Experimental studies of slag filter for drinking water treatment

Abstract The study examined the use of granulated blast furnace slag, an industrial by-product from ferrous industries for drinking water treatment. A laboratory scale filter, 9 cm diameter and 40 cm with iron slag media supported on a gravel bed could completely remove turbidity, total suspended solids and colour for an average influent loading of 28.26 NTU, 128.85 mg/L and 177.05 PCU respectively at a filtration rate of 0.32 m3hr−1m−2. The average removal of hardness, sulphate, nitrate, chloride and iron were 35%, 83%, 71%, 28% and 94% for an average influent loading of 579.79 mgL−1, 367.72 mgL−1, 120.52 mgL−1, 355.67 mgL−1 and 1.49 mgL−1respectively. Doubling the filtration rate with slight increase in loading rate showed 100% removal for turbidity, suspended solids and colour whereas hardness, sulphate, nitrate, chloride and iron removals were 27%, 73%, 86%, 28% and 95% respectively. The maximum head loss for continuous operation without backwash was only 75 mm. Intermittent washing helped to improve the filtered water quality for various filtration and loading rates. An increase in the rate of filtration up to 1.28 m3hr−1m−2 did not have any impact on the quality of treated water except sulphate and nitrate. After backwashing, there was considerable improvement in chloride removal. The removal of physicochemical parameters was due to precipitation, adsorption and ion exchange with the formation of products both at the surface and within the slag media. FTIR and XRD results also confirmed the behaviour of slag as an anion exchange resin. The maximum head loss observed in slag filter was 190 mm at the highest loading level and filtration rate.

Performance of carbon nanotube-coated steel slag filter media for the removal of phosphorus and heavy metal in stormwater

Performance of carbon nanotube-coated steel slag filter media for the removal of phosphorus and heavy metal in stormwater

The Effect of Dissolved Oxygen Distribution on Ammonium Nitrogen Removal in a Pilot-Scale of Vertical Upward-Flow of Aerated Electric Arc Furnace Slag Filter Systems At Various Hydraulic Loading Rates

The performance of an aerated vertical upward-flow electric arc furnace slag filter (VFEAFS) system in treating domestic wastewater was examined in a warm-climate country temperature. Two pilot scale column experiments were conducted at high (2.72 m3/m3.day) and low (1.04 m3/m3.day) hydraulic loading rate (HLR) set-up and the effect of different hydraulic loading levels on pollutant removal efficiency were studied. Aeration was introduced in the filter system at 10 L/min to observe oxygen distribution concentration towards ammonium nitrogen removal. The results demonstrated that both HLR set-up were capable to achieve more than 90% ammonium nitrogen (AN) removal; however, in terms of individual efficiency of the filter system, the VFEAFS of lower HLR performed better in comparison to the higher HLR set-up. The average effluent concentration of AN by both systems were found far below standard A of Malaysian sewage discharge limit (10 mg NH4-N/L). The results achieved in this pilot scale study indicate that removal of ammonium nitrogen in the aerated VFEAFS was explained by nitrification process, and this treatment system could be implemented to the other industry-environmental, municipal or residential wastewater.

Investigation of PO43- Removal in Aerated and Unaerated High Fe EAF-Slag Filter System

Phosphorus in wastewater is one the main culprit which accelerates eutrophication in waterbody if it is not being treated properly. Steel slag filter emerged as one alternative treatment for wastewater. However, the variousness of metal oxides including Fe in steel slag will affect the phosphorus removal efficiency. Thus, this study was conducted to investigate the ability of a series of lab-scale high Fe electric arc furnace (EAF- slag) column filters in removing PO43- from synthetic wastewater. The systems were operated under aerated and unaerated within acidic and alkaline conditions. Synthetic wastewater contained 25 mg/L was prepared as the feed and monitored weekly basis for the PO43- removal efficiency and the total metals (Ca, Fe, and Mg) concentrations in the effluents. The results show that both aerated and unaerated high Fe EAF-slag filter systems have high PO43- removal efficiency under acidic condition, which unaerated system performed slightly better. It can be observed that unaerated systems performed better in removing PO43- at acidic and neutral pH values but not at extremely high pH. As for the PO43- removal mechanism was achieved by adsorption and precipitation at acidic pH and the concentration of Ca, Mg and Fe in effluents was related to the PO43- removal efficiency at different pH values.