Drinking Water Treatment Sludge Research Articles

Removal of methylene blue from aqueous solutions using alum Sludge: Sorption optimization by response surface methodology

A sorption process on low cost sorbents is one the promising methods for removing of these pollutants from aqueous solutions. This report describes use of drinking water treatment sludge which is abundantly available from drinking water treatment plants, to remove methylene blue (MB) dye from aqueous solutions. The main objective of this work is to determine the optimum conditions for removal of MB dye, a common compound that is used as a model for organic chemicals. Response surface methodology (RSM) is used in the optimization of the sorption process. Six independent important factors which are temperature of treatment, pH of solution, dosage of sorbent, initial dye concentration, contact period and temperature of sorption were investigated using batch sorption technique with a 26 half factorial faced centered central composite design

Performance of waste-based amendments to reduce metal release from mine tailings: One-year leaching behaviour

A one-year leaching experiment has been conducted in order to assess the effectiveness of several amendments on metal immobilization in mine tailings from an old Pb/Zn mining area of Central Spain (San Quintín mine). Demineralized water was used as leaching solution, selecting doses equivalent to the annual rainfall conditions of the studied area. Columns with mine tailings without any amendment and others treated with 10% of sugar foam (SF), 15% of drinking water treatment sludge (DWS), 30% of paper mill sludge (PMS) and 15% of olive mill waste (OMW) were used. SF, DWS and PMS amendments increased the pH of leachates from values of approximately 4 to around neutrality. Additionally, the release of sulfate ions from the oxidation of pyritic residues was decreased in some extent by SF and DWS amendments. Metal leaching was effectively reduced by the amendments reaching overall decreases with respect to the unamended columns of 79–96% for Pb, 36–100% for Zn, 50–99% for Cu and 44–100% for Cd. The effect of the amendments in leachate pH, sulfate concentration and metal release from mine tailings was kept throughout the whole experimental period. Our results showed that the application of different organic and inorganic amendments based on by-products and waste materials may be a feasible alternative for the restoration of soils around abandoned metal mines.

Eco-efficient recycling of drinking water treatment sludge and glass waste: development of ceramic bricks

Current management for drinking water treatment sludge and glass waste is insufficient, and a new method is needed. We sought to develop a new approach for effective management. This work analyses the application possibilities of drinking water treatment sludge (DWTS) and windows glass waste (GW) to be used for the production of ceramic products. DWTS and GW are renewable, ecological and economical waste additives which save raw materials. Ceramic body with (40–60) of DWTS and (10–40) of GW additives have been burnt at 900 and 1000 °C temperatures. It is determined that DWTS and GW have an impact on physical–mechanical properties of ceramic body (density, compressive strength, water absorption, porosity) and change macro- and microstructure. DWTS additive also acts as natural colouring pigment. The work proposes eco-efficient application way of drinking water treatment sludge and windows glass waste, it solves exportation of DWTS and GW to landfills problems and positively affects regional ecological balance.

Utilisation of drinking water treatment sludge for the manufacturing of ceramic products

The influence of the additive of drinking water treatment sludge on the physical and mechanical properties, structural parameters, microstructure of the ceramic products is analysed in the research. Drinking water treatment sludge is renewable, environmentally-friendly, economical additive saving expensive natural raw materials when introduced into the ceramic products. The main drinking water treatment sludge component is amorphous Fe2O3 (70%). Formation masses are prepared by incorporating from 5 % to 60 % of drinking water treatment additive and by burning out at the temperature 1000 °C. Investigation showed that the physical and mechanical properties, microstructure of the ceramic bodies vary depending on the amount of drinking water treatment additive incorporated. In addition, drinking water treatment additive affects the ceramic body as a pigment that dyes the ceramic body in darker red colour.

BOX-BEHNKEN EXPERIMENTAL DESIGN FOR ELECTROKINETIC REMOVAL OF ALUMINUM FROM DRINKING WATER TREATMENT SLUDGE

Electrokinetic remediation is an emerging technology that can be used to remove contaminants from soils or sludge by application of an electric field. Here, we investigated the effects of potential apllied, electrolysis time and electrolyte content upon electrokinetic removal of aluminum from drinking water treatment sludge using the statistical Box-Behnken Design. The analysis gave a significant model, in which the quadratic part in particular was significant, thus justifying the optimization experiments. Since there was no apparent lack of fit, the model could be considered valid and its results interpreted more thoroughly. The values of the β coefficients, and their significance indicates that the most significant coefficients are the quadratic effects of potential applied and electrolysis time. The response surface showed an optimum predicted yield of 60.5% for a potential applied of 25 V, an electrolysis time of 72 h and 90% electrolyte content.

Drinking water treatment sludge as an efficient adsorbent for heavy metals removal

Green chemists paid much more attention towards the alternative ways to reutilize waste materials instead of its disposal in a non-ecofriendly manner. In this study, drinking-water treatment sludge (DWTS), which is a by-product resulted from drinking water treatment plants, was successfully applied as an adsorbent for Pb(II), Cd(II) and Ni(II) removal from wastewater. The physicochemical characteristics of DWTS were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms.The XRD analysis revealed that the DWTS under study consists of quartz and illite phases which had been reported for their adsorption efficiency. Firing of DWTS at 500°C causes the appearance of albite phase in addition to previous ones which enhances the adsorption capacity of these materials. The influence of different parameters such as firing temperature of DWTS, contact time, pH, DWTS dose and initial metal ions concentration on the adsorption of heavy metal ions and, consequently, on their removal were investigated. DWTS exhibit an adsorption efficiency towards Pb(II)>Cd(II)>Ni(II). The extremely high efficiency of DWTS towards Pb(II) adsorption can nominate it as a specific low-cost adsorbent for Pb ions.

Evaluation of alternative environmentally friendly matrix solid phase dispersion solid supports for the simultaneous extraction of 15 pesticides of different chemical classes from drinking water treatment sludge

This study describes the development, optimization and validation of a method for the extraction of 15 pesticides of different chemical classes in drinking water treatment sludge (DWTS) by vortex-assisted Matrix Solid Phase Dispersion (MSPD) with determination by gas chromatography coupled to mass spectrometry. It focused on the application of alternative and different solid supports to the extraction step of the MSPD. The main parameters that influenced the extraction were studied in order to obtain better recovery responses. Recoveries ranged from 70 to 120% with RSD below 20% for all analytes. Limits of quantification (LOQ) of the method ranged from 5 to 500 μg kg−1 whereas the analytical curves showed correlation coefficients above 0.997. The method under investigation used low volume of solvent (5 mL), low sample mass (1.5 g) and low mass of chitin (0.5 g), an environmentally friendly support. It has advantages, such as speed, simplicity and low cost material, over other methods. When the method was applied, 4 out of 15 pesticides were detected in the DWTS samples in concentrations below the LOQ.

Removal of aluminum from drinking water treatment sludge using vacuum electrokinetic technology

A vacuum electrokinetic apparatus was operated at a municipal water supply plant in Wuxi, China to study the removal of aluminum from the plant's drinking water treatment sludge, high in trivalent aluminum content. The effect of several experimental variables (initial pH, potential gradient, and zone in the sludge tank) and the trivalent aluminum removal mechanism were analyzed. The speciation of trivalent aluminum mainly depends on the initial pH of drinking water treatment sludge, and more fractions of trivalent aluminum were migrated at pH 4 than at higher or lower pH. The application of high voltage can enhance the removal efficiency of aluminum. A three-dimensional electric field analysis explained the difference in the removal efficiency at different zones in the sludge tank. In view of energy consumption, when the initial pH was 4 and a potential gradient of 2 V cm−1 was applied, achieving a final aluminum concentration of 30 g kg−1 after 120 h. The specific energy consumption was 11.7 kWh kg−1 of Al removed.

Middle Eocene clay from Goset Abu Khashier: Geological assessment and utilization with drinking water treatment sludge in brick manufacture

This investigation aims to study the physico-ceramic properties of bricks that were made from the Goset Abu Khashier clay (Qarara Formation, Middle Eocene deposits, El-Minia, Egypt) replaced with 15–60wt% drinking water treatment sludge (DWTS). The Qarara Formation deposits located in the east bank of the Nile River between Beni Suef and El-Minia Governorates, belong to the Middle Eocene deposits. The Qarara Formation deposits in the Goset Abu Khashier area contain several million tons of clay deposits. The Qarara Formation is composed of a grey to green shale (silty clay) grading upward to marl and limestone. The clay contains kaolinite (29wt%), montmorillonite (20wt%), albite (27wt%) and quartz (23wt%). The clay contains a high content of silica (49.41wt%) and a low content of alumina (19.77wt%) with considerable amounts of Fe2O3 (11.37wt%) and fluxing oxides (3.7wt%). Clay bricks containing 15–60wt% DWTS were fired at a temperature of 700–1000°C. The ceramic properties of bricks were determined according to the ASTM specifications. The phase composition of bricks was determined by XRD, FTIR and SEM techniques. It was investigated that the incorporation of DWTS in the body of clay bricks moderates the ceramic properties of fired bricks to be in agreement with the limiting values that were recommended for traditional bricks. XRD results illustrated that dehydration of kaolinite and the formation of metakaolinite facilitates vitrification and contributes to brick densification. FTIR results showed the formation of a wollastonite phase and indicated that increasing DWTS content facilitates the persistence of a vitrified phase. SEM micrographs illustrated that the porosity and densification of brick matrix was affected by the formation of amorphous vitreous phases and decreased with DWTS contents. It is recommended that the replacement of examined clay by 15–30wt% of DWTS is considered as the appropriate percentage for building bricks production and minimizes environmental impacts due to DWTS disposal into water bodies.

Adsorption Kinects and Isotherms for Removal of Rhodamine B (dye) using Adsorbents prepared from drinking water treatment sludge

The present work aims to investigate the removal of Rhodamine B dye (RB) from aqueous solution by using adsorbents prepared from alum sludge (AS) and Mud sludge (MS) of drinking water treatment plant. The effect of dye concentration, contact time, pH, temperature and adsorbent dose on the dye removal was studied. The equilibrium adsorption data of RB dye on the developed adsorbents were analyzed by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) Isotherms. The sorption data fitted well to Langmuir isotherm model. The maximum dye removal efficiency was observed at pH 7, contact time 90 min,and 0.1-0.25 gm dosage for both (AS) and (MS) adsorbents . Also, four kinetic models such as Pseudo-first order, Pseudo-second order, Intraparticle diffusion and Elovich models were tested to interpret the experimental data. The kinetic experimental data were fitted well to Pseudo-second order model.The thermodynamics parameters of adsorption system indicated spontaneous and endothermic process. Results indicate the effectiveness of the developed adsorbents for removing RB dye.

Adsorption of methylene blue from aqueous solutions using water treatment sludge modified with sodium alginate as a low cost adsorbent.

In this research, aluminum-based drinking water treatment sludge is used as a starting material and immobilized by sodium alginate to develop low cost adsorbent for the removal of methylene blue (MB) from aqueous solutions. The studied variables included pH, adsorbent dose, initial MB concentration and contact time. Characteristics of the adsorbent were also studied using scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR). It was revealed from kinetic tests that removal efficiency of MB was 88.5% under the optimum conditions of pH 8, initial MB concentration of 50 mg/L, contact time of 60 min, and adsorbent dose of 0.3 g/L. The oxygen functional groups such as -OH, C-O-C and C=O were found on the surface of developed adsorbent by FTIR. In addition, the adsorption data fitted well the Langmuir adsorption model with the maximum sorption capacity of 909.1 mg/g, and followed the pseudo-second-order kinetics. Findings of this study indicate that the prepared adsorbent is promising for further development of an effective and economical adsorbent material in the near future.

Dewatering of drinking water treatment sludge by vacuum electro-osmosis

ABSTRACTThe objective of this research was to evaluate the dewatering of drinking water treatment sludge (DWTS) by vacuum electro-osmosis dewatering (VEOD) technology. DWTS has a high moisture content, with the water existing as free water, pore water, surface adhesion water and internal combined water. Vacuum filtration of 0.05 MPa can quickly dewater sludge and has low energy consumption, but can only remove free water and some pore water. The moisture content of the DWTS was reduced to below 79% by vacuum filtration technique alone. At this moisture content, all free water had been expelled by vacuum filtration. Electro-osmosis optimized for the experimental conditions (0.05 MPa, 2.5 V/cm) began after vacuum filtration ceased, and drew pore water and surface adhesion water to the cathode, where it was expelled through vacuum filtration. The VEOD process removed all free water. In addition, pore water and surface adhesion water were reduced by 60.2% and 15.9%, respectively.

Adsorption of methylene blue using modified adsorbents from drinking water treatment sludge.

This study aims to explore the preparation and application of alum sludge (AS) and mud sludge (MS) from a drinking water treatment plant to remove methylene blue (MB) dye from aqueous solution. The sludge (MS and AS) was treated by chemical and physical activation to obtain new adsorbents. The adsorption experiments were carried out under different conditions of initial dye concentration (50-100 mg/L) adsorbent dosage (0.05-0.25 g), solution pH (3-9), temperature (20-60 °C) and contact time (20-90 min). Scanning electron microscopy (SEM) and X-ray diffraction instruments were used for characterization of the developed adsorbents. The results show that sludge activated by nitric acid (0.25 M HNO3) and pyrolysis at 700 °C were the best chemically and physically activated adsorbents. The optimum adsorption conditions for the adsorption of MB are 100 ppm initial dye concentration, 1 hour contact time, 250 °C solution temperature, pH 7 and 0.25 g adsorbent dosage. Application of the Langmuir and Freundlich Isotherm models showed that adsorbents fitted the Langmuir model well. SEM studies indicated the porous structural aspects of sludge suitable for removing MB dye.

Fabrication of Humidity Control Ceramics from Drinking-Water Treatment Sludge and Onggi Soil

In this study, humidity control ceramics with good adsorption/desorption capabilities and high strength were fabricated from drinking-water treatment sludge (DWTS) and Onggi soil. The DWTS powder heat-treated at 800°C and Onggi soil were mixed at weight ratios of 40:60, 50:50, 60:40, and 70:30 and fired at 800–1000°C. With increasing DWTS content, density and flexural strength increased. For the sample with a DWTS:Onggi soil weight ratio of 70:30, porosity and specific surface area decreased with increasing firing temperature, attributed to densification and grain growth at high firing temperatures. From the results obtained, a firing temperature of 800°C is the optimum condition for fabricating humidity control ceramics with good adsorption/desorption capabilities and strength. The maximum adsorbed amount for the sample fired at 800°C was 439 g/㎡.

Influence of vacuum pressure, pH, and potential gradient on the vacuum electro-osmosis dewatering of drinking water treatment sludge

ABSTRACTThis paper describes research that evaluated the influence of vacuum pressure, pH, and potential gradient on the vacuum electro-osmosis dewatering (VEOD) of drinking water treatment sludge (DWTS). In the first phase of the VEOD process, a vacuum pressure of −0.05 MPa was applied alone to DWTS for 30 min, removing almost all free water and part of pore water. In phase two, electro-osmosis was applied in combination with intermittent vacuum filtration, further reducing pore water and surface adhesion water in DWTS. However, statistical analysis indicated that the optimum dewatering parameter values were vacuum pressure at −0.06 MPa, pH at 6.2, and potential gradient at 2.5 V/cm, which resulted in a relevant energy consumption of 0.35 kW.h/kg removed water.

Dewatering of drinking water treatment sludge using the Fenton-like process induced by electro-osmosis

In the present study, the benefits of a Fenton-like treatment process in enhancing the dewaterability of drinking water treatment sludge have been investigated. It is found that using a vacuum electro-osmosis dewatering reactor often results in a low dewatering efficiency, while it can be improved significantly (by about 63% under the optimal condition) by adding the Fenton-like process in combination with acidification. The results based on the three-dimensional (3D) excitation–emission matrix fluorescence spectroscopy and Fourier-transformed infrared spectroscopy indicated that the sludge treated by the Fenton-like process could make fulvic acid-like substances disappear such that the extracellular polymeric substances (EPS) is broken and the dewaterability efficiency is improved. Furthermore, the scanning electronic microscopy analysis and particle size distribution analysis showed that the Fenton-like process and acidification destroyed the stable sludge flocs such that the water trapped in the flocs could be released easily and the dewaterability efficiency was enhanced. The 3D response surface of the water removal efficiency evidenced that the optimal operating parameters were Fe3+ dosage of 54 mg g−1 sludge, H2O2 dosage of 87mgg−1 sludge and pH of 6.3. The results obtained in this study are expected to provide guidance and support for using the Fenton-like treatment process together with acidification to dewater drinking water treatment sludge.

Recycling of iron and silicon from drinking water treatment sludge for synthesis of magnetic iron oxide@SiO₂ composites.

More attention has been paid to the deterioration of water bodies polluted by drinking water treatment sludge (DWTS) in recent years. It is important to develop methods to effectively treat DWTS by avoiding secondary pollution. We report herein a novel investigation for recovery of Si and Fe from DWTS, which are used for the synthesis of two iron oxide@SiO2 composites for adsorption of reactive red X-3B (RRX-3B) and NaNO2. The results show that Fe(3+) (acid-leaching) and Si(4+) (basic-leaching) can be successfully recovered from roasted DWTS. Whether to dissolve Fe(OH)3 precipitation is the key point for obtaining Fe3O4 or γ-Fe2O3 particles using the solvothermal method. The magnetic characteristics of Fe3O4@SiO2 (390.0 m(2) g(-1)) or Fe2O3@SiO2 (220.9 m(2) g(-1)) are slightly influenced by the coated porous SiO2 layer. Peaks of Fe-O stretching vibration (580 cm(-1)) and asymmetric Si-O-Si stretching vibrations (1080 cm(-1)) of Fe3O4@SiO2 indicate the successful coating of a thin silica layer (20-150 nm). The adsorption capacity of RRX-3B and NaNO2 by Fe3O4@SiO2 is better than that of Fe2O3@SiO2, and both composites can be recycled through an external magnetic field. This method is an efficient and environmentally friendly method for recycling DWTS.

Dispersion Stability of Drinking Water Treatment Sludge

The objective of this study is to improve the particle suspension stability of drinking water treatment sludge (DWTS) and comparable to other silicate powder which are bentonite, micro silica (micro-SiO2), and nano-silica (nano-SiO2). The main dispersion characteristic are related to particle size, and dispersion force. The representative samples of bentonite, micro-SiO2, nano-SiO2, and DWTS were dispersed at the same solid content in water. The particle size distribution and chemical composition of samples were analyzed. The suspended samples were measured for Zeta potential at the controlled pH value. Furthermore, turbidity of suspended samples were investigated at various sedimenting time. The results indicated that nano-SiO2 has the highest Zeta potential value at pH 8-12. The stability of particle dispersion could be implied from turbidity of suspension at various sedimenting time. Bentonite suspension performed more stability than other samples for longer time. However, stability of DWTS particles can be improved by particle size controlling and treatment with dispersion agent to create repulsive force from the charge on the particle surface.

The removal characteristics of natural organic matter in the recycling of drinking water treatment sludge: Role of solubilized organics

To clarify the role of solubilized organics derived from drinking water treatment sludge (DWTS) in the elimination of natural organic matter (NOM) in the DWTS recycling process, a probe sonoreactor at a frequency of 25kHz was used to solubilize the organics at varied specific energies. The coagulation behavior related to NOM removal in recycling the sonicated DWTS with and without solubilized organics was evaluated, and the effect on organic fractionations in coagulated water was determined. The study results could provide useful implications in designing DWTS recycling processes that avoid the enrichment of organic matter. Our results indicate that DWTS was disrupted through a low release of soluble chemical oxygen demand (SCOD) and proteins, which could deteriorate the coagulated water quality under the specific energy of 37.87–1212.1kWh/kgTS. The optimal coagulation behavior for NOM removal was achieved by recycling the sonicated DWTS without solubilized organics at 151.5kWh/kgTS specific energy. Recycling the sonicated DWTS could increase the enrichment potential of weakly hydrophobic acid, hydrophilic matter, and <3kDa fractions; the enrichment risks could be reduced by discharging the solubilized organics. Fluorescent characteristic analysis indicated that when recycling the sonicated DWTS without solubilized organics, the removal of humic-like substances was limited, whereas removal of protein-like substances was enhanced, lowering the enrichment potential of protein-like substances.

Effects of ultrasound pretreatment on the characteristic evolutions of drinking water treatment sludge and its impact on coagulation property of sludge recycling process

Large amounts of drinking water treatment sludge (DWTS) are produced during the flocculation or flotation process. The recycling of DWTS is important for reducing and reclaiming the waste residues from drinking water treatment. To improve the coagulation step of the DWTS recycling process, power ultrasound was used as a pretreatment to disintegrate the DWTS and degrade or inactivate the constituents that are difficult to remove by coagulation. The effects of ultrasound pretreatment on the characteristics of DWTS, including the extent of disintegration, variation in DWTS floc characteristics, and DWTS dewaterability, were investigated. The capacity of the recycling process to remove particulates and organic matter from low-turbidity surface water compared to a control treatment process without DWTS was subsequently evaluated. The coagulation mechanism was further investigated by analyzing the formation, breakage, and re-growth of re-coagulated flocs. Our results indicated that under the low energy density applied (0.03–0.033W/mL) for less than 15min at a frequency of 160kHz, the level of organic solubilization was less elevated, which was evidenced by the lower release of proteins and polysaccharides and lower fluorescence intensities of humic- and protein-like substances. The applied ultrasound conditions had an adverse effect on the dewaterability of the DWTS. Ultrasound pretreatment had no significant impact on the pH or surface charge of the DWTS flocs, whereas particle size decreased slightly and the specific surface area was moderately increased. The pollution removal capacity decreased somewhat for the recycled sonicated DWTS treatment, which was primarily ascribed to organic solubilization rather than variability in the floc characteristics of sonicated DWTS. The main coagulation mechanism was floc sweeping and physical adsorption. The breakage process of the flocs formed by the recycling process displayed distinct irreversibility, and the flocs were stronger and more resistant to breakage compared to those from the control treatment.