Powdered Waste Sludge Research Articles

Removal of Pb(II) from wastewater by biosorption using powdered waste sludge

Lead is a highly toxic heavy metal that causes serious health problems. Nonetheless, it is increasingly being used for industrial applications and is often discharged into the environment without adequate purification. In this study, Pb(II) was removed by powdered waste sludge (PWS) based on the biosorption mechanism. Different PWSs were collected from a submerged moving media intermittent aeration reactor (SMMIAR) and modified Ludzack-Ettinger (MLE) processes. The contents of extracellular polymeric substances were similar, but the surface area of MLE-PWS (2.07 m2/g) was higher than that of SMMIAR-PWS (0.82 m2/g); this is expected to be the main parameter determining Pb(II) biosorption capacity. The Bacillaceae family was dominant in both PWSs and may serve as the major responsible bacterial group for Pb(II) biosorption. Pb(II) biosorption using PWS was evaluated for reaction time, salinity effect, and isotherm equilibrium. For all experiments, MLE-PWS showed higher removal efficiency. At a fixed initial Pb(II) concentration of 20 mg/L and a reaction time of 180 minutes, the biosorption capacities (qe) for SMMIAR- and MLE-PWSs were 2.86 and 3.07 mg/g, respectively. Pb(II) biosorption using PWS was rapid; over 80% of the maximum biosorption capacity was achieved within 10 minutes. Interestingly, MLE-PWS showed enhanced Pb(II) biosorption with salinity values of up to 30 g NaCl/L. Linear regression of the Freundlich isotherm revealed high regression coefficients (R2 > 0.968). The fundamental Pb(II) biosorption capacity, represented by the KF value, was consistently higher for MLE-PWS than SMMIAR-PWS.

Removal of thorium(IV) from aqueous solution by biosorption onto modified powdered waste sludge: experimental design approach

The biosorption of radioactive Th(IV) ions in the aqueous solutions onto the modified powdered waste sludge (MPWS) has been examined. In this context, the parameters affecting biosorption of Th(IV) from aqueous solutions has been examined by using MPWS biosorbent in Box Behnken statistical experimental design. The structure of MPWS biosorbent was characterized by using SEM and BET techniques. According to the experimental design results, MPWS and Th(IV) concentrations should be kept high to achieve the maximum efficiency in Th(IV) biosorption. On the other hand, MPWS, which is also used as a biosorbent, is an economical, effective and natural biosorbent.

Waste Material Adsorbents for Zinc Removal from Wastewater: A Comprehensive Review

This review examines a variety of adsorbents and discusses mechanisms, modification methods, recovery and regeneration, and commercial applications. A summary of available researches has been composed by a wide range of potentially low-cost modified adsorbents including activated carbon, natural source adsorbents (clay, bentonite, zeolite, etc.), biosorbents (black gram husk, sugar-beet pectin gels, citrus peels, banana and orange peels, carrot residues, cassava waste, algae, algal, marine green macroalgae, etc.), and byproduct adsorbents (sawdust, lignin, rice husk, rice husk ash, coal fly ash, etc.). From the literature survey, different adsorbents were compared in terms of Zn2+adsorption capacity; also Zn2+adsorption capacity was compared with other metals adsorption. Thus, some of the highest adsorption capacities reported for Zn2+are 168 mg/g powdered waste sludge, 128.8 mg/g dried marine green macroalgae, 73.2 mg/g lignin, 55.82 mg/g cassava waste, and 52.91 mg/g bentonite. Furthermore, modification of adsorbents can improve adsorption capacity. Regeneration cost is important, but if consumption of virgin adsorbent is reduced, then multiple economic, industrial, and environmental benefits can be gained. Finally, the main drawback of the already published Zn2+adsorption researches is that their use is still in the laboratory stage mostly without scale-up, pilot studies, or commercialization.

Removal of Cu(II) ions by biosorption onto powdered waste sludge (PWS) prior to biological treatment in an activated sludge unit: A statistical design approach

Biological treatment of synthetic wastewater containing Cu(II) ions was realized in an activated sludge unit with pre-adsorption of Cu(II) onto powdered waste sludge (PWS). Box-Behnken experimental design method was used to investigate Cu(II), chemical oxygen demand (COD) and toxicity removal performance of the activated sludge unit under different operating conditions. The independent variables were the solids retention time (SRT, 5–30 d), hydraulic residence time (HRT, 5–25 h), feed Cu(II) concentration (0–50 mg L −1) and PWS loading rate (0–4 g h −1) while percent Cu(II), COD, toxicity (TOX) removals and the sludge volume index (SVI) were the objective functions. The data were correlated with a quadratic response function ( R 2 = 0.99). Cu(II), COD and toxicity removals increased with increasing PWS loading rate and SRT while decreasing with the increasing feed Cu(II) concentration and HRT. Optimum conditions resulting in maximum Cu(II), COD, toxicity removals and SVI values were found to be SRT of 30 d, HRT 15 h, PWS loading rate 3 g h −1 and feed Cu(II) concentration of less than 30 mg L −1.

Effects of operating parameters on kinetics of copper(II) ion biosorption onto pre-treated powdered waste sludge (PWS)

Effects of operating parameters such as pH, temperature, Cu(II) ion and the adsorbent concentrations and particle size on batch biosorption kinetics of copper(II) ions onto pre-treated powdered waste sludge (PWS) were investigated. Pseudo-first and second order kinetics were used for correlation of pre-equilibrium biosorption data and the rate constants were determined. The pseudo-second order kinetics was found to be more suitable for representation of the kinetic data for almost all cases. Kinetic constants increased with increasing pH, temperature and PWS concentration, but decreased with increasing Cu(II) concentrations and the particle size of PWS. The highest rate constants for the pseudo-first and second order kinetics were 0.808 h −1 and 0.0309 (mg/g) −1 h −1, respectively for the smallest particle size of 53 μm. The highest Cu(II) biosorption capacity of 156 mg g −1 was obtained with PWS and Cu(II) concentrations of 0.25 g l −1 and 100 mg l −1 with the smallest particle size ( D p < 53 μm).

Kinetics of Zinc(II) Ion Biosorption onto Powdered Waste Sludge (PWS) at Different Operating Conditions

Batch biosorption kinetics of zinc(II) ions onto powdered waste sludge (PWS) were investigated under different experimental conditions such as variable pH (3–6), temperature (30–50°C), Zinc ion (50–350 mg L−1) and PWS (0.25–3 g L−1) concentrations and PWS particle size (53–231 μm). The rate and the extent of zinc(II) biosorption increased with pH yielding pH 5 (qm = 60 mg g−1) as the optimal value without Zn(OH)2 precipitation. Increases in temperature also resulted in increases in biosorption rate with an activation energy of 6 kcal mol−1 according to the second-order kinetics. Maximum biosorbed Zn(II) concentration was 72 mg g−1 at 50°C. Biosorbed zinc(II) concentration at the end of 6 h of incubation increased with increasing zinc(II) concentration (qm = 95 mg g−1 at 300 mg L−1 Zn), but with decreasing particle size (qm = 70 mg g−1 with Dp = 53 μm) and concentration of PWS (qm = 168 mg g−1 with PWS of 0.25 g L−1). Pseudofirst- and second-order kinetics were used for correlation of biosorption data and for determination of the rate constants. The pseudosecond-order kinetics was found to be more suitable for representation of the kinetic data for almost all cases due to similarity between the adsorption kinetics and bimolecular reactions. Kinetic constants increased with increasing pH, temperature, and PWS concentration, but decreased with increasing zinc(II) concentrations and the particle size of PWS. The highest rate constants for the pseudofirst- and second-order kinetics were 0.71 h−1 and 0.024 (mg/g)−1 h−1 , respectively, for the smallest particle size of 53 μm. The highest Zn(II) biosorption capacity of 168 mg g−1 was obtained with PWS and Zn(II) concentrations of 0.25 g L−1 and 100 mg L−1at the end of 6 h biosorption period.

Elimination of Cu(II) toxicity by powdered waste sludge (PWS) addition to an activated sludge unit treating Cu(II) containing synthetic wastewater

Copper(II) ion toxicity onto activated sludge organisms was eliminated by addition of powdered waste sludge (PWS) to the feed wastewater for removal of Cu(II) ions by biosorption before biological treatment. The synthetic feed wastewater containing 14 or 22 mg l −1 Cu(II) was mixed with PWS in a mixing tank where Cu(II) ions were adsorbed onto PWS and the mixture was fed to a sedimentation tank to separate Cu(II) containing PWS from the feed wastewater. The activated sludge unit fed with the effluent of the sedimentation tank was operated at a hydraulic residence time (HRT) of 10 h and sludge age (SRT) of 10 days. To investigate Cu(II), COD and toxicity removal performance of the activated sludge unit at different PWS loadings, the system was operated at different PWS loading rates (0.1–1 g PWS h −1) while the Cu(II) loading rate was constant throughout the operation. Percent copper, COD and toxicity removals increased with increasing PWS loading rate due to increased adsorption of Cu(II) onto PWS yielding low Cu(II) contents in the feed. Biomass concentration in the aeration tank increased and the sludge volume index (SVI) decreased with increasing PWS loading rate due to elimination of Cu(II) from the feed wastewater by PWS addition. PWS addition to the Cu(II) containing wastewater was proven to be effective for removal of Cu(II) by biosorption before biological treatment. Approximately, 1 g PWS h −1 should be added for 28 mg Cu h −1 loading rate for complete removal of Cu(II) from the feed wastewater to obtain high COD removals in the activated sludge unit.

Cu(II) Ion Recovery by Biosorption onto Powdered Waste Sludge (PWS) in a Fed‐Batch Reactor: Particle Size Effects

Biosorption of Cu(II) ions onto pre‐treated powdered waste sludge (PWS) was investigated using a completely mixed reactor operating in fed‐batch mode. Experiments were performed with PWS of different particle sizes between 53 and 231 µm while the feed flow rate (0.25 l h−1), feed copper ion concentrations (200 mg l−1) and the amount of adsorbent (2 g PWS) were constant. Breakthrough curves describing variations of the aqueous phase copper ion concentrations with time were determined for different particle sizes of the adsorbent. Percent copper removal from the aqueous phase and the biosorbed copper ion concentrations increased with decreasing particle size or increasing surface area of the PWS. A modified Bohart‐Adams equation was used to determine the biosorption capacity of PWS and the rate constant for Cu(II) ion biosorption. The biosorption capacity of PWS based on per unit mass of PWS (g Cu gPWS−1) increased with decreasing particle size due to increased external surface area of PWS. The biosorption capacity of PWS for Cu(II) ions in completely mixed fed‐batch reactor was found to be comparable with the powdered activated (PAC) adsorption columns However, the adsorption rate constant in a completely mixed fed‐batch reactor was an order of magnitude larger than those obtained in adsorption columns because of the elimination of mass transfer limitations encountered in the column operations. Therefore, it was proven that the adsorption capacity and the rate of adsorption can be improved by reducing the particle size of the adsorbent (PWS) and using a completely mixed fed‐batch reactor due to a larger adsorbent surface area and better contact between the phases.

Determination of model parameters for zinc (II) ion biosorption onto powdered waste sludge (PWS) in a fed–batch system

Biosorption of zinc (II) ions onto pre-treated powdered waste sludge (PWS) was investigated using a completely mixed tank operating in fed–batch mode instead of an adsorption column. Experiments with variable feed flow rate (0.05–0.5 L h −1), feed Zn(II) ion concentrations (37.5–275 mg L −1) and amount of adsorbent (1–6 g PWS) were performed using fed–batch operation at pH 5 and room temperature (20–25 °C). Break-through curves describing variations of aqueous (effluent) zinc ion concentrations with time were determined for different operating conditions. Percent zinc removal from the aqueous phase decreased, but the biosorbed (solid phase) zinc ion concentration increased with increasing feed flow rate and zinc concentration. A modified Bohart–Adams equation was used to determine the biosorption capacity of PWS ( q′ s) and the rate constant ( K) for zinc ion biosorption. Biosorption capacity ( q′ s=57.7 g Zn kg −1 PWS) of PWS in fed–batch operation was found to be comparable with powdered activated carbon (PAC) in column operations. However, the adsorption rate constant ( K=9.17 m 3 kg −1 h −1) in fed–batch operation was an order of magnitude larger than those obtained in adsorption columns because of elimination of mass transfer limitations encountered in the column operations. Therefore, a completely mixed tank operated in fed–batch mode was proven to be more advantageous as compared to adsorption columns due to better contact between the phases yielding faster adsorption rates.

Zinc (II) ion recovery by biosorption onto powdered waste sludge (PWS): effects of operating conditions

AbstractPowdered waste sludge (PWS) obtained from a paint industry wastewater treatment plant and pretreated with 1% H2O2 was used for biosorption of Zn(II) ions from aqueous solution. The effects of operating conditions, pH, temperature, agitation speed, PWS particle size, Zn ion and PWS concentrations on the extent of Zn ion biosorption were investigated in batch experiments. The optimum pH resulting in maximum Zn ion biosorption was found to be pH = 5, since Zn ions precipitated in the form of Zn(OH)2 at pH levels above 5. The rate and extent of Zn ion biosorption increased with temperature between 25 and 50 °C, although biosorption was not strongly sensitive to temperature variations since the activation energy was low at 4.5 kcal mol−1. Biosorbent particle size had a significant effect on Zn ion biosorption, yielding high percentage Zn removals at small particle sizes (Dp &lt; 100 µm) or large surface areas of PWS. Agitation speed also considerably affected the extent of Zn ion removal, and should be above 150 rpm in order to obtain a high rate. The extent of Zn ion biosorption was also affected by the initial Zn ion and PWS concentrations. At constant biosorbent (PWS) concentration, percentage Zn ion removal decreased, but the biosorbed Zn concentration increased with increasing initial Zn ion concentrations. However, at constant initial Zn concentrations, percentage Zn removal increased, but the biosorbed Zn ion concentration decreased with increasing adsorbent (PWS) concentration. With a maximum Zn ion biosorption capacity of 168 mg g−1 powdered waste sludge was proven to be an effective biosorbent compared to other biosorbents. Copyright © 2006 Society of Chemical Industry

Utilization of powdered waste sludge (PWS) for removal of textile dyestuffs from wastewater by adsorption

Acid pre-treated powdered waste sludge (PWS) was used for removal of textile dyestuffs from aqueous medium by adsorption as an alternative to the use of powdered activated carbon (PAC). The rate and extent of dysetuff removals were determined for four different dyestuffs at different PWS concentrations varying between 1 and 6 g l –1. Biosorbed dyestuff concentrations at equilibrium decreased with increasing PWS concentration for all dyestuffs tested. PWS was more effective for adsorption of Remazol red RR and Chrisofonia direct yellow 12 as compared to the other dyestuffs tested. More than 80% percent dyestuff removal was obtained for all dyestuffs at PWS concentrations above 4 g l −1 after 6 h of incubation. Similar to percent dyestuff removal, the rate of adsorption was maximum at a PWS concentration of 4 g l −1. Kinetics of adsorption of dyestuffs was investigated by using the first- and second-order kinetic models and the kinetic constants were determined. Second-order kinetics was found to fit the experimental data better than the first-order model for all dyestuffs tested. Adsorption isotherms were established for all dyestuffs used and the isotherm constants were determined by using the experimental data. Langmuir and the generalized adsorption isotherms were found to be more suitable than the Freundlich isotherm for correlation of equilibrium adsorption data. Acid pre-treated PWS was proven to be an effective adsorbent for dyestuff removal as compared to the other adsorbents reported in literature studies.

Biosorption of copper(II) ions onto powdered waste sludge in a completely mixed fed-batch reactor: Estimation of design parameters

Biosorption of Cu(II) ions onto pre-treated powdered waste sludge (PWS) was investigated using a fed-batch operated completely mixed reactor. Fed-batch adsorption experiments were performed by varying the feed flow rate ( 0.075–0.325 l h −1), feed copper (II) ion concentrations (50–300 mg l −1) and the amount of adsorbent (1–6 g PWS) using fed-batch operation. Breakthrough curves describing the variations of effluent copper ion concentrations with time were determined for different operating conditions. Percent copper ion removals from the aqueous phase decreased, but the biosorbed (solid phase) copper ion concentrations increased with increasing the feed flow rate and Cu(II) concentration. A modified Bohart–Adams equation was used to determine the biosorption capacity of PWS and the rate constant for Cu(II) ion biosorption. Adsorption rate constant in fed-batch operation was an order of magnitude larger than those obtained in adsorption columns because of elimination of mass transfer limitations encountered in the column operations while the biosorption capacity of PWS was comparable with powdered activated (PAC) in column operations. Therefore, a completely mixed reactor operated in fed-batch mode was proven to be more advantageous as compared to adsorption columns due to better contact between the phases yielding faster adsorption rates.

Batch kinetics and isotherms for biosorption of copper(II) ions onto pre-treated powdered waste sludge (PWS)

Waste sludge samples from different plants were tested for Cu(II) ion biosorption capacities with and without pre-treatment. Waste sludge from a paint industry wastewater treatment plant was found to perform better than the others after pre-treatment with 1% H 2O 2. Powdered waste sludge (PWS) from the paint industry wastewater treatment plant was used for recovery of Cu(II) ions from aqueous solution by biosorption after pre-treatment with 1% H 2O 2. Batch kinetics and isotherms of biosorption of Cu(II) ions were investigated at variable initial Cu(II) concentrations between 50 and 400 mg l −1 with a PWS particle size of 64 μm. The pseudo-first and -second order kinetic models were used to correlate the experimental data. The kinetic constants were determined for both models and the second order kinetic model was found to be more suitable. The Langmuir, Freundlich and the generalized isotherm models were used to correlate the equilibrium biosorption data and the isotherm constants were determined. The Langmuir isotherm was found to fit the experimental data better than the other isotherms tested. The maximum biosorption capacity (116 mg g −1) of the pre-treated powdered waste sludge for Cu(II) ions was found to be superior as compared to the other biosorbents reported in literature

Removal of copper(II) ions from aqueous medium by biosorption onto powdered waste sludge

Powdered waste sludge (PWS) was used for removal of copper(II) ions from aqueous solution by biosorption. Waste activated sludge obtained from a paint industry wastewater treatment plant was pre-treated with 1% hydrogen peroxide solution dried, ground and sieved to a number of fractions with different particle sizes. Biosorption capacity of pre-treated PWS for Cu(II) ion removal was investigated as function of particle sizes (external surface area), copper(II) and PWS concentrations and also pH using batch biosorption experiments. Biosorbed copper ion concentrations increased with increasing specific external surface area of PWS, initial Cu 2+ concentration and pH, but decreased with increasing PWS concentration. Percent copper removal from the solution also increased with increasing external surface area or decreasing particle size of the adsorbent, PWS concentration and pH, but decreased with increasing initial copper ion concentration. The maximum biosorption capacity was 156 mg Cu 2+ g PWS −1 when PWS concentration was 0.25 g l −1 with an average particle size of 64 μm. The initial volumetric rate of biosorption also increased with increasing specific external surface area of PWS resulting in nearly 70 mg Cu l −1 h −1 at a specific external surface area of 943 cm 2 g −1 with the smallest particle size (53 μm) tested. Optimal pH resulting in maximum biosorption was 5 with a minimum zeta potential (−15.6 mV) on the surface of the PWS particles.

Biosorption of zinc(II) ions onto powdered waste sludge (PWS): Kinetics and isotherms

Waste sludge samples obtained from a paint industry wastewater treatment plant was dried, ground and pre-treated with 1% H 2O 2 to improve the biosorption capacity. The powdered waste sludge (PWS) was sieved to different mesh sizes and used for biosorption of zinc(II) ions from aqueous solution. Kinetics of zinc biosorption onto PWS was investigated by using the PWS samples with particle size of 64 μm. The pseudo-first and -second order rate expressions were used to correlate the experimental data. The kinetic constants were determined for both models and the second order rate expression was found to be more suitable. Three different biosorption isotherms were used to correlate the equilibrium biosorption data and the isotherm constants were determined. The Langmuir isotherm was found to fit the experimental data better than the other isotherms tested. Maximum biosorption capacity was found to be 82 mg Zn g PAS −1. High biosorption capacity and low saturation constant of pre-treated PWS used for zinc ion biosorption makes the adsorbent more attractive as compared to other alternatives.