Powdered activated carbon added biological treatment of pre-treated landfill leachate in a fed-batch reactor

Biological treatment of landfill leachate usually results in low treatment efficiencies because of high chemical oxygen demand (COD), high ammonium-N content and also presence of toxic compounds such as heavy metals. A landfill leachate with high COD content was pre-treated by coagulation-flocculation followed by air stripping of ammonia at pH = 12. Pre-treated leachate was biologically treated in an aeration tank operated in fed-batch mode with and without addition of powdered activated carbon (PAC). PAC at 2 g l(-1) improved COD and ammonium-N removals resulting in nearly 86% COD and 26% NH4-N removal

Simultaneous adsorption and biological treatment of pre-treated landfill leachate by fed-batch operation

Due to high chemical oxygen demand (COD), ammonium-N content and presence of toxic compounds such as heavy metals, direct biological treatment of landfill leachate results in low removal efficiencies. In order to improve biological treatability of the leachate, coagulation-flocculation and air stripping of ammonia were used as pre-treatment. Pre-treated leachate was treated biologically using an aeration tank operated in fed-batch mode in the absence and presence of powdered activated carbon (PAC) as adsorbent. PAC addition improved COD removal significantly especially at concentrations above 0.5 gl(-1). However, improvements in COD removals were marginal for PAC concentrations above 2 gl(-1). Nearly 86% COD removal was achieved with 2 gl(-1) PAC added biological treatment whereas, COD removals by only biological oxidation and only PAC adsorption were nearly 74 and 38%, respectively at the end of 30 h of fed-batch operation. An empirical equation was developed to describe the contribution of adsorption over biological treatment as a function of PAC concentration. (C) 2003 Elsevier Science Ltd. All rights reserved

Repeated fed-batch biological treatment of pre-treated landfill leachate by powdered activated carbon addition

High chemical oxygen demand (COD), high ammonium-N content and presence of toxic compounds such as heavy metals result in low removal efficiencies in direct biological treatment of landfill leachate. Raw landfill leachate was subjected to pre-treatment by coagulation-flocculation and air stripping of ammonia before biological treatment. Pre-treated leachate was subjected to biological treatment in an aeration tank operated in repeated fed-batch mode in the absence and presence of powdered activated carbon (PAC) as adsorbent. Three different cycles of I x 30 h, 3 x 10 h, and 5 x 6 h were used in the absence and presence of 2 g l(-1) PAC. The results clearly indicated that PAC addition has improved COD removal significantly as compared to PAC-free biological treatment. Repeated fed-batch treatment also resulted in lower effluent COD and higher COD removal efficiencies as compared to single-cycle operation. The feed COD of 7000 mg l(-1) was reduced to final COD values of 365 mg l(-1) and 875 mg l(-1) in repeated fed-batch experiments with 5 x 6 h cycles in the presence (2 g l(-1) PAC) and absence of PAC, respectively. Repeated fed-batch operation with 3 x 30 It cycle length resulted in percent COD removal and final COD content of 94% and 285 mg l(-1), respectively, with 2 g l(-1) PAC addition. (C) 2003 Elsevier Inc. All rights reserved

Aerobic biological treatment of pre-treated landfill leachate by fed-batch operation

Landfill leachate obtained from the solid waste landfill area contained high chemical oxygen demand (COD) and ammonium ions which resulted in low COD and ammonium removals by direct biological treatment. COD and ammonium ion contents of the leachate were reduced to reasonable levels by chemical precipitation with lime and air stripping of ammonia. The pre-treated leachate was subjected to aerobic biological treatment in an aeration tank by fed-batch operation. The effects of the feed wastewater COD content and flow rate on COD and ammonium ions removal were investigated. Nearly 76% COD and 23% NH4-N removals were obtained after 30 h of operation with a flow rate of 0.211 h(-1) and the feed COD content of 7000 mg COD l(-1). COD removal efficiency decreased with increasing COD loading rates. A kinetic model for COD removal was developed and the kinetic constants were determined by using the experimental data. (C) 2003 Elsevier Inc. All rights reserved

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 C2+ 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 Cu2+ g PWS-1 when PWS concentration was 0.25 g l(-1) with an average particle size of 64 mu m. 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 mu m) tested. Optimal pH resulting in maximum biosorption was 5 with a minimum zeta potential (-15.6 mV) on the surface of the PWS particles. (c) 2005 Elsevier Ltd. All rights reserved

Adsorbent supplemented biological treatment of pre-treated landfill leachate by fed-batch operation

Biological treatment of landfill leachate usually results in low COD removals because of high chemical oxygen demand (COD), high ammonium-N content and presence of toxic compounds. Coagulation-flocculation with lime addition and air stripping of ammonia were used as pre-treatment in this study in order to improve biological treatability of the leachate. Pre-treated leachate was subjected to adsorbent supplemented biological treatment in an aeration tank operated in fed-batch mode. COD and NH4-N removal performances of powdered activated carbon (PAC) and powdered zeolite (PZ) were compared during biological treatment. Adsorbent concentrations varied between 0 and 5 g l(-1). Percent COD and ammonium-N removals increased with increasing adsorbent concentrations. Percent COD removals with PAC addition were significantly higher than those obtained with the zeolite. However, zeolite performed better than the PAC in ammonium-N removal from the leachate. Nearly 87% and 77% COD removals were achieved with PAC and zeolite concentrations of 2 g l(-1), respectively. Ammonium-N removals were 30% and 40% with PAC and zeolite concentrations of 5 g l(-1), respectively at the end of 30 h of fed-batch operation. (C) 2004 Elsevier Ltd. All rights reserved