Alum Sludge Research Articles

Phosphate removal using thermally regenerated Al adsorbent from drinking water treatment sludge

Alum sludge (AS) is an abundant and ubiquitous residue generated from drinking water treatment plants. AS was thermally treated to use as an adsorbent for phosphate removal from wastewater. Organic matter in the AS was a potential competitor and can deter phosphate adsorption. Pyrolysis and drying of AS were adopted to enhance phosphate removal by eliminating organic matter and enriching Al content. Adsorption kinetics showed that phosphate removal was highest with the AS pyrolyzed at 700 °C followed by 500 °C, air-dried and oven-dried (105 °C). Adsorption kinetic modelling showed that chemisorption is the operative mechanism of phosphate removal in all the AS. Adsorption isotherms also showed that the pyrolyzed AS and air-dried AS had similar adsorption capacity of 30.83–34.53 mg P/g AS. Al dissolution was less than 2 mg/g Al in all the AS samples. COD release was significant in the dried AS, up to 8.0 mg COD/g AS, whereas the pyrolyzed AS released less than 1 mg COD/g AS. FTIR and SEM-EDS analyses of the AS after phosphate adsorption showed the formation of aluminum-phosphate complex. Overall, the pyrolysis of AS at 700 °C was most effective in removing phosphate without leaving secondary pollution.

Properties of concrete incorporating alum sludge in different conditions as partial replacement of fine aggregate

Water treatment plant generates alum sludge as waste during the process of treating drinking water for human consumption. Notwithstanding the benefits of treating water, there are still problems associated with the disposal of waste generated from the water treatment plant after the treatment process. Studies have shown that the conventional disposal method is associated with environmental hazards; and there is a need to derive more sustainable method of alum sludge disposal. This study focused on investigating the properties of concrete incorporating alum sludge as a partial replacement of fine aggregate. The alum sludge used in this study as replacement of fine aggregate was prepared in two ways; oven-dried under temperature 105 °C and 300 °C heated alum sludge (heated in the furnace). Both alum sludge (oven-dried alum sludge, 300 °C heated alum sludge) was crushed/grinded to obtain a maximum particle size of 65 µm and used to replace fine aggregate in different proportions (0%, 5%, 10% and 15%). The produced concrete was tested for fresh properties; and then cured at 7, 28, 56, 90 and 180 days to test for hardened and durability properties. The results from the study showed that oven-dried alum sludge and 300 °C treated alum sludge produce a workable mix and can be used as replacement of fine aggregate with optimum replacement content of 10%. Both alum sludge improved the density of the concrete, strength properties of the concrete and concrete durability. At 15% replacement content of fine aggregate with oven dried and 300°C heated alum sludge, yield a decrease in workability and strength properties, with poor durability properties.

Sustainable production of concrete with treated alum sludge

• Incorporation of AS in concrete could be useful in protecting the environment. • The inclusion of AS tends to increase the water demand of concrete. • The mechanical properties decrease with the increase of AS substitution. • The inclusion of the AS tends to enhance the durability properties of concrete. A huge amount of unwanted sludge produced daily from water and wastewater treatment plants and disposed into landfills which cause a numerous environmental challenges. This study aims to investigate the effect of replacing cement by alum sludge (AS) on the performance of normal concrete. The replacement levels of the AS by weight of cement were: 0%, 2%, 4%, 6%, and 8%. Slump test was performed on fresh concrete to measure workability. The mechanical and durability properties were investigated on two concrete curing ages (after 7 days and 28 days). The scanning electron microscopy (SEM) test was carried out after 28 days of curing. Results showed that, the mechanical strengths and workability of concrete tend to decrease as the replacement level of cement with the AS increases. The optimal mechanical strengths were indicated at 4.0% replacement level of cement by AS with the addition of 2% superplasticizer (SP). The reduction in the optimal compressive and flexural strengths were up to 25.6% and 6.5% compared with the control mix after 28 days of curing, respectively. In addition, the treated AS enhances the durability properties of concrete at all ages. The lowest water absorption percentage (1.06%), gas permeability (1.03 × 10 −16 m 2 ) and chloride penetration (5 mm) were associated with the highest replacement level of cement with AS (8%) and addition of 2% SP, after 28 days of curing period. Overall, incorporation of treated AS in concrete production could be useful in protecting the environment by reducing the volume of alum sludge in the landfill.

Pelletized adsorbent of alum sludge and bentonite for removal of arsenic.

Powder adsorbents show an excellent adsorption capacity for arsenic(As) due to the large specific surface area. However, the performance of powder adsorbents decreases significantly by channeling in the adsorption bed, and the powder is released from the bed. Pelletization of power adsorbent can solve the problems, and bentonite was proposed as a binder to improve the strength. The adsorption capacity and lifetime of pelletized adsorbent were evaluated through a batch and column study. The addition of bentonite decreased adsorption capacity by 16% of pellet without bentonite, but improved compressive strength of adsorbent up to 3.6 times. In the batch test, the maximum adsorption capacity of pelletized adsorbent is 22.2mg As/g, which is about 40% of powder adsorbent. However, in the column study, pellet adsorbent showed similar adsorption performance and lifetime to commercial and powder adsorbent. As a result, the pellet adsorbent using bentonite is a potential low-cost adsorbent to remove effectively As in the aqueous phase.

Reuse of UK alum water treatment sludge in cement-based materials

Alum salts are commonly used as coagulants in the purification of surface water for potable supplies. The resultant waste alumina-rich sludge is currently landfilled in the UK. This study aimed to valorise sludge by using heat-treated alum sludge as an additive in cement. Alum sludge was calcined at 475–1100 °C and then characterized to correlate physical and mineralogical changes with cementitious activity and engineering performance. Alum sludge calcined at 825 °C transforms to poorly crystalline η-alumina (eta) and has cementitious activity. The calcined sludge rapidly reacts with gypsum to form ettringite which leads to a shortening of the induction period and onset of alite hydration. Gypsum depletion leads to undersulfated C3A hydration which consumes ettringite to form monosulfoaluminate thereby inhibiting further alite hydration. The poorly crystalline η-alumina is metastable, transforming to highly crystalline α-alumina at 1100 °C. In pastes containing more crystalline sludges, alite hydration is enhanced because the undersulfated C3A reactions are avoided, leading to improved performance.

Improvement and characterization of alum sludge by nano-iron oxide and rice husk for removal of methylene blue dye from aqueous solution

In the present study, the adsorption characteristics of the alum sludge (AS) waste from Rod El-Farag water treatment plant was improved by treatment with acidic rice husk (RH) and Nano-Magnetite (N.M) to form Nano-Magnetite composite (ASRHNMC). This composite gained new characteristics of large surface area, mesoporous structure and magnetic properties and it was used as a low cost adsorbent for the removal of methylene blue (MB) as a cationic dye from aqueous solution. (AS) and (ASRHNMC) were characterized by FT-IR, XRD, BET N2, EDX, SEM, TEM and XRF and were compared to adsorption ability against MB dye. The pH of the solution, sorbent dose, initial dye concentration, contact time and temperature were investigated using batch sorption technique for (MB) dye. The experimental results have pointed out that the adsorption equilibrium data is fitted well to the Langmuir isotherm reflecting favor formation of monolayer of MB dye on composite surface. The value of enthalpy change indicating that the removal process is endothermic. The adsorption process follows pseudo-second order rate equation and the negative values of standard free energy (DG◦) suggested that the adsorption process is spontaneous. The repeatability and regeneration studies of (ASRHNMC) for adsorption of MB were investigated and the results indicated the ability of reuse this composite several times in removal of MB from aqueous solutions.

Impacts alum DWTPs sludge discharge and changes in flow regime of the Nile River on the quality of surface water and cultivated soils in Fayoum watershed, Egypt

Discharge of Drinking Water Treatment Plants sludge directly on surface waters without any treatment is becoming an important issue in most countries around the world, behavior is not only affecting on the water quality, but also on soil and crops. This study investigated the effect of discharge of alum sludge and the variation in the level of the Nile water (flow regime) on water and soil qualities. The water samples were analyzed for physical, chemical and microbiological parameters. In winter (closure season), the mean values of EC, TDS, major ions, pH, DO and total algae count were higher than in summer. In summer (flooding season), it was noticed that the mean values of SiO2, metals, COD, BOD, TOC, nutrients and bacteriological parameters exceed winter season values. Moreover, the concentrations of Al, Fe, Mn were above WHO permissible limits and the concentrations of aggregate organic parameters exceed the FAO permissible limits in sites near the areas of sludge discharge. Most of water samples exceed the national guidelines. For soil, our findings showed that the concentrations of metals in soil samples collected from areas irrigated from canals receiving alum sludge are more (two-three times) than their concentrations from the pure sites. However, Pb concentration in the contaminated soil reaches ten times more than in the pure one. The management of sludge disposal becomes an urgent priority to save waterways, soil and crops from pollution. Finally, the variation in water flow during the winter closure period with reduction by ≈15 BCM is similar to the same reduction in the Nile flow when the Grand Ethiopian Renaissance Dam starts operation. This indicates that the long-term reduction in water flow due to the construction of this dam may cause serious environmental changes in the Nile River in Egypt.

Effects of different industrial waste materials as partial replacement of fine aggregate on strength and microstructure properties of concrete

This study aimed at investigating the effect of different industrial waste material as partial replacement of fine aggregate on strength properties of normal concrete. For economical and sustainability of natural resources, use of some industrial waste can demonstrate numerous benefits for the construction industry. Nevertheless, there is limited study on the use of industrial waste as replacement of fine aggregate in normal strength concrete especially, using alum sludge from water treatment plant as replacement of fine aggregate. The material used in this study as replacement of fine aggregate (river sand) was oven-dried alum sludge. While quarry dust and limestone dust were also employed as non-reactive industrial waste material, to identify the specific effect of oven-dried alum sludge in concrete. All the materials were crushed to obtain smaller particle size and then used as replacement of fine aggregate in different percentages (5, 10 and 15%). The results from the experiments shows that addition of industrial waste material improved the concrete density, compressive, flexural, and splitting tensile strengths. The result also shows that optimum replacement content of fine aggregate with industrial waste were 10% for oven-dried alum sludge, whereas 15% for quarry and limestone dust content that improved all strength properties investigated in this study. All industrial waste employed in this study as fine aggregate have proven to be a good filler material by filling the concrete internal void and improving the strength properties for a normal strength concrete.

Displacement dewatering of sludge with supercritical CO2

Supercritical CO2 (sCO2) displaces water from wastewater, alum, and papermill sludge. The sCO2 appears to enter the sludge matrix through viscous fingering through the entrained water. Because the water removed far exceeds the solubility of water in sCO2, it must be displaced by the sCO2 rather than dissolved out. Adding a small amount of soap to the sludge converts some of the bound water into free water, which can then be displaced by sCO2. Application of the sCO2 in multiple stages greatly enhances dewatering as compared to a single stage process. Approximately 70, 70 and 85% of the initial water can be removed from alum, wastewater and paper sludges, respectively, through a five-stage process. Staged application of sCO2 doubles the efficiency of water removal over a single-stage process of the same duration. It is proposed that when the sCO2 entrained in the sludge is decompressed between stages some of the water is explosively displaced by the expanding CO2.

A Study of fluoride and arsenic adsorption from aqueous solution using alum sludge based adsorbent

A Study of fluoride and arsenic adsorption from aqueous solution using alum sludge based adsorbent

Synthesis of high-quality zeolite LTA from alum sludge generated in drinking water treatment plants

This study demonstrated the conversion of alum sludge produced at water treatment plants to high quality zeolite LTA. Thus, problems with sludge landfilling costs and environmental contamination may be avoided. The methodology involved alkali fusion pre-treatment of alum sludge followed by hydrothermal synthesis to improve the quantity and quality of zeolite LTA made. Alum sludge activation using fusion facilitated formation of high-quality zeolite LTA (97 wt%) which was comparable to commercial material (98 wt%) and superior to samples made using hydrothermal synthesis without fusion pre-treatment (81 wt%). Notably, the alum sludge derived samples contained greater amounts of impurities such as iron, calcium, and magnesium. Preferred synthesis conditions using fusion-pre-treatment were: SiO2/Al2O3 = 2.5; Na2O/SiO2 = 3; H2O/Na2O = 40; reaction time =5 h: reaction temperature = 80 °C. The average zeolite LTA particle size ranged from 0.7 (hydrothermal) to 1.1 (fusion pre-treated) to 3.0 (commercial) microns. Kinetic studies indicated that the exchange of calcium ions with all zeolite samples reached equilibrium within 60 min. Equilibrium ion exchange data revealed the maximum loading of calcium ions was 106.6, 83.9, and 64.6 mg Ca2+/g for fusion pre-treated, hydrothermally treated, and commercial LTA, respectively. However, on a “dry basis” the cation capacity of the commercial and fusion pre-treated samples was similar.

Granulation and calcination of alum sludge for the development of a phosphorus adsorbent: From lab scale to pilot scale

Alum sludge, an Al-oxyhydroxide rich waste product from water treatment practices, has the potential to be valorized as a P adsorbent material. However, several challenges currently prevent its application as an adsorbent in industrial setting, i.e. a limited P adsorption capacity due to saturation by organic matter and a fine nature resulting in percolation problems in adsorption bed setups. In this study, granulation and subsequent calcination of alum sludge were proposed to overcome these issues and to improve the P adsorption properties of alum-based adsorbent (ABA) materials. The effect of calcination temperature on the physicochemical properties of granular material was examined using X-ray diffraction, mass-spectroscopy coupled thermogravimetric analysis, Fourier-transform infrared spectrometry and specific surface area analysis, combined with density and crushing strength measurements. The ABA material obtained at 550 °C showed superior P adsorption properties and, therefore, this material was selected for further P adsorption testing and characterization (scanning electron microscopy and sieving). Batch P adsorption tests showed that this material had a maximum P adsorption capacity of 7.27 mg-P g−1. Kinetic adsorption tests determined the effect of the solid-to-liquid ratio and the granule particle size on the P removal. Finally, the performance of the ABA-550 material was tested in a pilot-scale adsorption setup, using a surface water stream (0.47 mg-P L−1) at a flow rate of 200 L h−1. During the test, the P removal efficiency always exceeded 86%, while the material maintained its structural stability. The results of this study illustrate the potential of granulated/calcined ABA materials for P adsorption, paving the way for the industrial application of this novel, sustainable P removal technology.

Recycling Building Wastes and Dewatered Alum Sludge in Permeable Reactive Barriers (PRBs) to treat the Heavy Metals of the Ground Water Contaminated by Landfill-Leachate

Recycling Building Wastes and Dewatered Alum Sludge in Permeable Reactive Barriers (PRBs) to treat the Heavy Metals of the Ground Water Contaminated by Landfill-Leachate

Enhanced Primary Treatment of Sewage by Sand and Alum Sludge Ballasted Flocculation

Enhanced Primary Treatment of Sewage by Sand and Alum Sludge Ballasted Flocculation

Electrolysis using Pt/SS electrodes for aluminum recovery from drinking water treatment sludge

Alum sludge from the drinking water treatment plant (DWTP) of Surabaya City, Indonesia, potentially contains high aluminum and organic pollutant contents. Aluminum is sourced from the use of aluminum sulfate as a coagulant during the water treatment process. Whereas, the organic pollutant is from domestic and industrial wastewater discharges into the raw water source. Aims of this study were to characterize the alum sludge of the Surabaya DWTP, to determine suitable electrode materials and optimum electrical current for aluminum recovery using electrolysis. The sludge was characterized according to metal concentrations and chemical oxygen demand (COD). Cyclic voltammetry, a common method for determining appropriate electrode materials for electrolysis, was conducted to confirm platinum (Pt) and stainless steel A304 (SS A304) as suitable electrodes. A polarization test was applied to determine the current for electrolysis. Electrolysis using these electrodes was conducted in one compartment reactor for 6 h. The results showed that the sludge had high concentrations of aluminum and organic substance. The suitable anode and cathode in the electrolysis of acidified alum sludge at pH 3 were Pt and SS A304, respectively. Aluminum recovery efficiency was achieved at 300 mA (52.10%), in which metal impurities were low, and COD removal was 24%.

Optimisation for enhancing sludge dewaterability using different conditioners

Dewatering of alum sludge from drinking-water plants is proving to be a major challenge because of the large amounts of residual sludges produced annually. In the last few years, most studies have focused on improving the dewatering process to reduce costs of alum sludge management and transport. In the present study, three different types of conditioners were tested. Lime was used as an example of an inorganic conditioner, ferric chloride (FeCl3) was used as an example of a chemical conditioner and chitosan was used as an example of a biopolymer. The performance of a conditioner was evaluated with respect to its effect in reducing the resistance of the conditioned sludge to filtration, namely the specific resistance to filtration (SRF). Tests are run using different concentrations of the conditioners, different speeds of rotation and different pH values to investigate the maximum value of percentage reduction in SRF. The response surface methodology was chosen from the Design-Expert program (version 12), and the Box–Behnken design was employed to find factor settings that optimise the output response – that was, percentage reduction in SRF (Red. %). The model obtained proved to be significant enough but with varying degrees. Chitosan showed to be the most favourable conditioner with a maximum percentage reduction in SRF of 98.57%. This was followed by ferric chloride, which gave a value of 89.2% for percentage reduction in SRF, and lastly came lime with a percentage reduction of 79.81%. Besides, a lower concentration of the conditioner and a lower speed of rotation are required when using chitosan as a conditioner.

Recovery of Alum Sludge by using Membrane-Based Electrochemical Process

Recovery of Alum Sludge by using Membrane-Based Electrochemical Process

Anaerobic Filter Treatment of Landfill-Leachate Using Low-Cost Filter Materials

Anaerobic-filters are quite expensive due to the high-cost of artificial filtration media. Hence, introducing alternative low-cost filtration media will make anaerobic-filters more economical. The aim of this study was to investigate the performances of several low-cost/waste materials as filtration media in anaerobic-filters to treat organic compounds, nutrients and heavy metals found in landfill-leachate. The experimental set-up consisted of four down-flow anaerobic-filter columns, two of which were control columns while the others were experimental columns. The control columns were filled with Granular Activated Carbon (GAC) and Plastic Pall Rings (PPR) as single medium. The experimental columns were filled with a mixture of Dewatered Alum Sludge (DAS), Washed Sea Sand (WSS), Firewood Charcoal (FWC), while the other with the same materials as layers. During the application of 10% diluted landfill-leachate within a period of 115 days, the overall removal efficiencies of the filter bed with layered-media were 73%, 84%, 61%, 55%, 76% and 79% for COD, BOD5, TN, Ammonia-N (NH3-N), TP and Orthophosphate-P (PO43- -P), respectively. The filter bed with mixed-media gave the overall removal efficiencies of 59%, 87%, 49%, 26%, 71% and 78% for COD, BOD5, TN, NH3-N, TP and PO43- -P, respectively. The experimental columns showed significant removal efficiencies for heavy metals, namely Pb (40%), Cd (48%), Cu (41%) and Mn (52%) in the mixed-media column and (54%), Cd (37%), Cu (54%) and Mn (57%) in the layered-media column.

Optimisation of zeolite LTA synthesis from alum sludge and the influence of the sludge source

Generation of alum sludge (AS) at drinking water treatment plants represents an environmental liability and adds to the cost of water purification. Consequently, this study explored the feasibility of using low and high carbon containing alum sludge from two water treatment plants to synthesize zeolite LTA. The hypothesis was that zeolite LTA synthesis was dependant upon alum sludge source and that a range of strategies may be required to optimize zeolite crystallinity. Zeolite characteristics such as morphology, phase composition, crystallinity, and particle size distribution were recorded. “One pot” hydrothermal synthesis of precursor gel with molar composition 4.2Na2O:Al2O3:1.2SiO2:168H2O at 80°C for 3 hr resulted in 25 and 46 wt.% zeolite LTA from high and low carbonaceous sludge, respectively. Prior to hydrothermal reaction stage it was discovered that ageing of the gel, addition of zeolite LTA seeds, ultrasonic treatment and calcination all promoted zeolite LTA formation. Calcination of the alum sludge at 700°C for 2 hr before hydrothermal synthesis resulted in particle size reduction and the highest amount of crystalline zeolite LTA: 79 wt.% from low carbon sludge and 65 wt.% from high carbon sludge. Notably, the zeolite crystallinity reported in this study was the higher than previous studies on this topic. The outlined approach may allow value adding of alum waste and produce a commodity which could be used locally by the water treatment plant as a water softener.

Granulation of Drinking Water Treatment Residues: Recent Advances and Prospects

Beneficial reuse of drinking water treatment plant residues (WTRs) has been intensively studied worldwide in the last decades, but few engineering applications can be found. The majority of WTRs were directly reused in cake form (after dewatering), e.g., alum sludge cake as main substrate used in constructed wetlands (CWs), or oven dried and ground powdery form, e.g., sorbent for pollutant removal. However, WTRs reuse in such forms has several drawbacks, i.e., difficulty of recovering and easy clogging (in CWs), which result in limited WTRs engineering applications. Granulation or pelleting could widen and be a wiser WTRs reuse route and also seems to be a promising strategy to overcome the “application bottleneck” issues. In the literature, a number of trials of WTRs granulation have been reported since 2008, including sintering ceramsite, gel entrapment and newly emerged techniques. Hence, there is a need to overlook these studies and promote WTRs granulation for further development. To this end, this review firstly provides a piece of updated comprehensive information and critical analysis regarding WTRs granulation/pelleting technology. It aims to enhance WTRs granulation studies in the developing stage and thus enlarge WTRs engineering applications.