Environment International 32 (2006) 405 ñ 411

Title: Life cycle assesment of municipal solid waste management methods: Ankara case study
Authors: ÷zeler D., Yeti˛ ‹., Demirer G.N.
Abstract:Different solid waste management system scenarios were developed and compared for the Municipal Solid Waste Management System of Ankara by using the life cycle assessment (LCA) methodology. The solid waste management methods considered in the scenarios were collection and transportation of wastes, source reduction, Material Recovery Facility (MRF)/Transfer Stations (TS), incineration, anaerobic digestion and landfilling. The goal of the study was to determine the most environmentally friendly option of MSWM system for Ankara. The functional unit of the study was the amount of solid waste generated in the system area of concern, which are the districts of Ankara. The life cycle inventory analysis was carried out by IWM Model-1. The inputs and outputs of each management stage were defined and the inventory emissions calculated by the model were classified in to impact categories; non-renewable energy sources exhausting potential, final solid waste as hazardous and nonhazardous, global warming, acidification, eutrophication and human toxicity. The impacts were quantified with the weighing factors of each category to develop the environmental profiles of each scenario. In most of the categories, Source Reduction Scenario was found to be the most feasible management method, except the global warming category. The lowest contribution to GWP was calculated for the anaerobic digestion process. In the interpretation and improvement assessment stage, the results were further evaluated and recommendations were made to improve the current solid waste management system of Ankara. © 2005 Elsevier Ltd. All rights reserved.

Journal of Hazardous Materials B128 (2006) 258 ñ 264

Title: Effect of biogenic substrate concentration on the performance of sequencing batch reactor treating 4-CP and 2,4-DCP mixtures

Authors: Erkan fiahinkaya, Filiz B. Dilek

Abstract:Effect of a biogenic substrate (peptone) concentration on the performance of sequencing batch reactor (SBR) treating 220 mg/l 4-chlorophenol (4-CP) and 110 mg/l 2,4-dichlorophenol (2,4-DCP) mixtures was investigated. In this context, peptone concentration was gradually decreased from 300 mg/l to null in which chlorophenols were fed to the reactor as sole carbon and energy sources. By this way, the effect of peptone concentration on observed yield coefficient (Y), biomass concentration, chlorophenols and COD removal performances were investigated. Decreasing peptone concentration accompanied with lower biomass concentration led to increase in peak chlorophenol and COD concentrations within the reactor during each SBR cycle. This, in turn, caused noteworthy declines in the removal rates as chlorophenol degradations followed Haldane substrate inhibition model. Also, increased peak chlorophenol concentrations led to the accumulation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), which is -meta cleavage product of 4-CP. Despite the decreased removal rates, complete chlorophenols and CHMS degradation, in addition to high COD removal efficiencies (>90%), were observed for all studied conditions, even chlorophenols were added as sole carbon and energy sources. Another significant point is that 2,4-DCP at slightly elevated concentrations (>20 mg/l) within the reactor caused a strong competitive inhibition on 4-CP degradation. In SBR, feeding the influent to the reactor within a certain period (i.e. filling period) provided dilution of coming wastewater, which decreased the chlorophenols concentrations to which microorganisms were exposed. Therefore, use of SBR may help to avoid both self and competitive inhibitions in the treatment of 4-CP and 2,4-DCP mixture especially in the presence high biogenic substrate concentrations. In addition, isolation and identification studies have indicated that Pseudomonas sp. and Pseudomonas stutzeri were dominant species in the acclimated mixed culture. © 2005 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials B136 (2006) 763 ñ 769

Title: Importance of H2O2/Fe2+ ratio in Fenton's treatment of a carpet dyeing wastewater
Authors: ›pek G¸lkaya, G¸lerman A. S¸r¸c¸, Filiz B. Dilek
Abstract:The effectiveness of the Fenton's reagent (H2O2/Fe2+) in the treatment of carpet dyeing wastewater was investigated under different operational conditions, namely, H2O2 and FeSO4 concentrations, initial pH and temperature. Up to 95% COD removal efficiency was attained using 5.5 g/l FeSO4 and 385 g/l H2O2 at a pH of 3, temperature of 50 ?C. The H2O2/Fe2+ ratio (g/g) was found to be between 95 and 290 for maximum COD removal. It was noteworthy that, keeping H2O2/Fe2+ ratio constant within the range of 95ñ290, it became possible to decrease FeSO4 concentration to 1.1 g/l and H2O2 concentration to 96.3 g/l, still achieving nearly the same COD removal efficiency. The relative efficiencies of Fenton's oxidation and coagulation stages revealed that Fenton's coagulation removed organic compounds which were not removed by Fenton's oxidation, indicating that the Fenton's coagulation acted as a polishing step. © 2006 Elsevier B.V. All rights reserved.

Biochemical Engineering Journal 31 (2006) 141 – 147

Title: Biodegradation of 4-CP and 2,4-DCP mixture in a rotating biological contactor (RBC)
Authors: Erkan Şahinkaya, Filiz B. Dilek
Abstract:In this study, the performance of a two stage rotating biological contactor (RBC)was evaluated for the treatment of syntheticwastewater containing peptone, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) at 5 rpm. Also, the effect of biogenic substrate (peptone) concentration on the reactor performance was investigated. High chlorophenols (>98%) and COD (>94%) removals were achieved throughout the reactor operation in the first stage and the second stage behaved as a polishing step. The observed maximum 4-CP and 2,4-DCP removal rates in the first stage were 2305 mg/L day (18.3 g/m3 day) and 1202 mg/L day (9.5 g/m3 day), respectively. Deacclimation of biomass was carried out for 3.5 months after 260 days of operation with the reactor feed turning on to contain peptone only. Upon addition of 4-CP (200 mg/L) and 2,4-DCP (100 mg/L), a rapid reacclimation of biomass was observed within 16 days. Shock loading experiments with 4-CP (822.7±1.4) and 2,4-DCP (424.6±1.9 mg/L) resulted in around four times higher effluent 4-CP concentrations than 2,4-DCP in both stages, which may be due to strong competitive inhibition of 2,4-DCP on 4-CP degradation. © 2006 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials B137 (2006) 282 – 287

Title: Effect of biogenic substrate concentration on 4-chlorophenol degradation kinetics in sequencing batch reactors with instantaneous feed
Authors: Erkan Şahinkaya, Filiz B. Dilek
Abstract:Two sequencing batch reactors (SBRs) instantaneously fed with 200 mg/l 4-chlorophenol (4-CP) were operated at different feed peptone concentrations to investigate the effect of biogenic substrate (peptone) concentrations on reactor performance, yield coefficient (Y) and 4-CP degradation kinetics. One of the reactors was operated at 10 days of sludge retention time (SRT) and the other was operated at 20 days of SRT. High chemical oxygen demand (COD) removal efficiencies (90–95%) and complete 4-CP removals (detection limit was 0.05 mg/l) were observed even in the absence of peptone. Accumulation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), meta cleavage product of 4-CP, was observed, which was completely removed at the end of the reactor cycle. It was concluded that decreasing peptone concentrations did not affect 4-CP degradation profiles and Haldane equation can be satisfactorily used to predict time course variation of 4-CP concentrations. It was assumed that specialists (competent biomass) are only responsible for 4-CP degradation and its concentration was constant although peptone concentration in the feed was varied, as competent biomass grows on 4-CP only. Model developed using this assumption well tracked the experimental data. The kinetic coefficients obtained for the reactor operated at 10 days of SRT were also valid for the reactor operated at 20 days of SRT although higher degradation rates were observed due to higher steady state biomass concentrations. © 2006 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials B136 (2006) 258 – 265

Title: Use of Fenton oxidation to improve the biodegradability of a pharmaceutical wastewater
Authors: Hüseyin Tekin, Okan Bilkay, Selale S. Ataberk, Tolga H. Balta, I. Haluk Çeribaşı, F. Dilek Sanin, Filiz B. Dilek, Ülkü Yetiş
Abstract:The applicability of Fenton's oxidation to improve the biodegradability of a pharmaceuticalwastewater to be treated biologicallywas investigated. Thewastewaterwas originated from a factory producing a variety of pharmaceutical chemicals. Treatability studies were conducted under laboratory conditions with all chemicals (having COD varying from 900 to 7000 mg/L) produced in the factory in order to determine the operational conditions to utilize in the full-scale treatment plant. Optimum pH was determined as 3.5 and 7.0 for the first (oxidation) and second stage (coagulation) of the Fenton process, respectively. For all chemicals, COD removal efficiency was highest when the molar ratio of H2O2/Fe2+ was 150–250. At H2O2/Fe2+ ratio of 155, 0.3M H2O2 and 0.002M Fe2+, provided 45–65% COD removal. The wastewater treatment plant that employs Fenton oxidation followed by aerobic degradation in sequencing batch reactors (SBR), built after these treatability studies provided an overall COD removal efficiency of 98%, and compliance with the discharge limits. The efficiency of the Fenton's oxidation was around 45–50% and the efficiency in the SBR system which has two reactors each having a volume of 8m3 and operated with a total cycle time of 1 day, was around 98%, regarding the COD removal. © 2005 Elsevier B.V. All rights reserved.

Bull. Environ. Contam. Toxicol. (2006) 76:481–489

Title: Degradation of Low and High Molecular Weight Fractions of Softwood Bleachery Effluents by Penicillium camemberti in Up-flow Column Reactor
Authors: B. K. Taşeli, C. F. Gökçay

Environmental Technology, Vol. 27. pp 613-621

Abstract: Separation by settling is one of the most troublesome stages of an activated sludge process. A decrease in the efficiency of separation of microbial biomass from the treated effluent causes a decrease in the overall efficiency of the treatment plant. One of the most common problems in activated sludge systems to negatively influence the settleability is sludge bulking which can be defined as non-settling situation of microbial mass. The main objective of this study is to find out the effect of phosphorus deficiency on bulking of activated sludge. In order to achieve this aim, the effects of a strictly phosphorus limited environment was investigated by running 6 semi-continuous activated sludge reactors. Since the specific aim of the study is to identify the effects of magnesium and calcium ions on sludge bulking in a phosphorus deficient medium, 3 different magnesium and calcium concentrations (5, 10, 20 meq l-1) were studied. Laboratory scale reactors were fed with synthetic wastewater and operated at a sludge age of 8 days. Results showed that, phosphorus deficiency caused sludge bulking. Sludge samples examined under microscope showed that the floc structures from reactors fed with different cations are significantly different. To identify the differences, a series of chemical analyses were conducted on the sludge samples. In addition to that, sludge volume index (SVI) values were monitored on a daily basis. Next, the concentration of phosphorus in the feed medium was increased in two separate steps and the possibility to cure the sludge bulking problem was investigated. It was found that bulking of activated sludges due to phosphorus deficiency could be cured by the addition of phosphorus. For phosphorus deficient bulking in relation to the cations present in the system some mechanisms are suggested.

Water Research 40 (2006) 1359 – 1366

Title: Enzymatic extraction of activated sludge extracellular polymers and implications on bioflocculation
Authors: Mohamed Lamin Sesaya, Gülay Özcengiz, F. Dilek Sanin
Abstract: This study examines enzyme hydrolysis, a mild, effective, but a rarely used method of extracellular polymer extraction, in removing polymers from mixed culture activated sludge flocs. Two carbohydrate specific enzymes (a-amylase and cellulase) and a protein specific enzyme (proteinase) are used during the study. First, the kinetic aspect is investigated, then enzyme dose optimization is carried out on laboratory grown activated sludge samples cultured at solids retention times (SRT) of 4 and 20 days. A more commonly used cation exchange resin (CER) extraction technique is also employed for comparison purposes. Results indicate that the extraction of extracellular polymers by enzymes is a rather quick process reaching equilibrium within only a few hours. As the doses of enzymes are increased, the extracted polymer quantities increase up to a certain dose, beyond which not much extraction is observed. The method does not cause any significant cell lysis as measured by the viable cell counts. Carbohydrate-hydrolyzing enzymes extract small amount of proteins along with the carbohydrates and protein-hydrolyzing enzyme extracts some carbohydrates together with the proteins, indicating that proteins and carbohydrates exist bound to each other in the extracellular polymer network of sludge. Enzyme extraction generally gives a lower estimate of polymers compared to the CER method, but correctly detects the trends in the polymer quantity. © 2006 Elsevier Ltd. All rights reserved.

Journal of Hazardous Materials B137 (2006) 990–997

Title: An investigation of heavy metal biosorption in relation to C/N ratio of activated sludge
Authors: Bilgen Yüncü, F. Dilek Sanin, Ülkü Yetiş
Abstract:The effect of C/N ratio of activated sludge on heavy metal biosorption was investigated. Three sets of semi-continuous reactors with different feed C/N ratios (9, 21 and 43 mg COD/mg TKN) were set up. Sorption equilibrium tests have indicated that the biosorptive capacity of activated sludge was highly dependent on metal species and the C/N ratio. The increase in C/N ratio resulted in an increase in the Cd(II) sorption capacity of activated sludge whereas it decreased the Cu(II) sorption capacity. As for Zn(II), a different behavior was observed such that, the highest and lowest capacities have occurred at C/N ratio of 21 and 43, respectively. For Ni(II) biosorption, isotherm tests produced greatly scattered data; so, it was not possible to obtain any plausible result to indicate the relationship between maximum adsorptive capacity and C/N ratio. The accompanying release of Ca(II) and Mg(II) ions and also carbohydrates into the solution during biosorption have indicated that ion exchange mechanism was involved however, was not the only mechanism during the sorption process. © 2006 Elsevier B.V. All rights reserved.

Journal of Membrane Science 281 (2006) 560–569

Title: Reclamation of acid dye bath wastewater: Effect of pH on nanofiltration performance
Authors: Göksen Çapar, Levent Yılmaz, Ülkü Yetiş
Abstract:This paper describes the effect of pH on the selection of the best treatment scheme for the reclamation of acid dye bath wastewaters (ADBW) of carpet manufacturing industry. ADBW, having acidic pH (5.0–5.9) originally, was subjected to pre-filtration through 1.0 µm microfiltration (MF) media prior to nanofiltration (NF). Three treatment alternatives were adopted: (1) single NF without pH neutralization; (2) sequential NF without pH neutralization; (3) single NF with pH neutralization. Color was removed completely and turbidity was rejected by 79–92% in all alternatives. However, COD, total solids, total hardness and conductivity were partially removed in single NF without pH neutralization. The inadequate rejection of pollutants lead to the implementation of sequential NF consisting of three stages, where COD rejection increased from 55%–77% to 94% at the end of the third stage. Finally, the wastewater pH was neutralized by adjusting to 7.0, which provided COD rejection efficiency as high as 97% in single NF. The flux decline in single NF at acidic pH was 14–23%. In sequential NF, the flux decline decreased from 21% to 9% in three stages. The flux declines increased up to 25% due to pH neutralization, however chemical cleaning was found to be effective in restoring the fluxes. Besides, the main cause of flux decline, which was fouling at acidic pH became concentration polarization at neutral pH. Therefore, the best treatment scheme for the recovery of ADBW came out to be single NF with pH neutralization preceded by 1.0 µm MF. These results revealed that pH is an important operational parameter affecting the selection of the best treatment scheme for ADBW. © 2006 Elsevier B.V. All rights reserved.

Separation Science and Technology, 41: 2771–2784, 2006

Title: Effect of Color and Surfactants on Nanofiltration for the Recovery of Carpet Printing Wastewaters
Authors: Göksen Çapar, Levent Yılmaz, Ülkü Yetiş
Abstract:Carpet printing wastewater (CPW) was spiked with metal-complex dyes at concentrations of 10 and 30 mg/L to investigate the effect of feed color on separation performance of nanofiltration (NF). The rejection was excellent; 98–100% for color and COD under all spiking conditions. Although the flux decline increased with increasing dye concentration, the concentration polarization was the main cause of the flux decline. The effect of surfactants on NF separation performance was also investigated by preparing synthetic wastewaters with dyes and auxiliary chemicals. The presence of a non-ionic penetrant did not adversely affect the color rejection whereas the COD rejection was reduced from 100% to 91%. Furthermore, fouling became dominant when surfactants were used.

Journal of Hazardous Materials B135 (2006) 423–430

Title: Membrane based strategies for the pre-treatment of acid dye bath wastewaters
Authors: Göksen Çapar, Levent Yılmaz, Ülkü Yetiş
Abstract:This paper, as part of a study carried out for the recovery of the acid dye bath wastewaters of a carpet manufacturing industry by membrane processes, describes the evaluation of alternative strategies for the pre-treatment of acid dye bath wastewaters. Dead-end microfiltration (MF) simulating sand filtration with MF media having pore sizes of 2.5, 1.0, 0.45 and 0.2 µm and ultrafiltration (UF) with an UF membrane having a molecular weight cut off (MWCO) of 50,000 Da were tested in single and sequential stages in order to achieve the best treatment efficiency. Four alternative process trains were tested; single MF, sequential MF, single UF, and MF followed by UF. For both MF and UF, application of sequential filtration did not provide any significant benefit over single processes. In addition, chemical oxygen demand (COD) removal performance of all the alternative processes was similar where the highest removal was only 5%. On the other hand, color removals were much better; ranging from 15 to 100%, even with single MF. Comparison of all the process alternatives revealed that, single MF (0.45 ·m), as the simplest process, is the most suitable pre-treatment method for the acid dye bath wastewaters. © 2005 Elsevier B.V. All rights reserved.

Journal of Membrane Science 277 (2006) 120–128

Title: Reclamation of printing effluents of a carpet manufacturing industry by membrane processes
Authors: Göksen Çapar, Levent Yılmaz, Ülkü Yetiş
Abstract:The effluent from the print dying process of a carpet manufacturing industrywas subjected to nanofiltration (NF) and ultrafiltration (UF) processes aiming at water reuse. Three alternatives were adopted; (i) NF, (ii) loose UF (MWCO 20,000 Da) followed by NF and (iii) tight UF (MWCO 1000 Da) followed by NF. The separation performances and flux decline levels were compared for the detemination of the best process. Printing effluent was chemically precipitated using alum and fed to a lab-scale plate-and-frame membrane module under a trans-membrane pressure of 1.75×105 and 5.90×105 Pa (1.75 and 5.90 bar) for UF and NF processes, respectively. All the alternatives were tested in concentration mode of filtration where a volume reduction factor of up to 28.5 was achieved. The NF process provided very high separation performance for COD, color, turbidity, total solids and total hardness. The flux decline started at 16% and reached up to 31% at a volume reduction factor of 11.8. The loose and tight UF processes applied before NF to reduce this flux decline were not effective with a very severe flux decline of about 60% in both processes. The comparison resulted in a recommendation with single stage NF with adequate effluent characteristics. © 2005 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials B137 (2006) 1674–1680

Title: Pb(II) biosorption using anaerobically digested sludge
Authors: Emre Tokçaer, Ülkü Yetiş
Abstract:Removal of Pb(II) by using resting cells of anaerobically digested sludge (ADS) obtained from a nearbywastewater treatment plantwas examined. Firstly, sorption kinetic and equilibrium experiments were conducted using agitated, thermostated (25 °C) batch reactors. The maximum Pb(II) sorption capacity was found to be very high (1750 mg/g dry ADS or 8.45 mmol/g dry ADS). At all initial Pb(II) concentrations tested, sorption resulted in neutralization with an increase in the solution pH from an initial value of 4.0–5.5 to an equilibrium value of 7.0–8.0, at which Pb(II) can precipitate as hydroxide. The removal of Pb(II) by ADSwas found to involve bioprecipitation as well as biosorption. FTIR spectrometry highlighted carboxyl groups present on the surface of ADS as the major functional groups responsible for biosorption. Secondly, a three-stage semi-continuous pseudo-counter current reactor system was tested to reduce ADS requirement in comparison to a conventional single-stage batch reactor. At an initial Pb(II) concentration of about 200 mg/L, an effluent Pb(II) concentration of 1.3 mg/L was achieved in the three stage reactor, corresponding to a metal removal capacity of 682.7 mg/g dry ADS (3.30 mmol/g), in comparison to 1.9 mg/L and 644.0 mg/g dry ADS (3.10 mmol/g) for the single-stage batch reactor. © 2006 Elsevier B.V. All rights reserved.

Desalination 199 (2006) 515–517

Title: Microfiltration: a pretreatment alternative for indigo dyeing textile wastewater
Authors: Niğmet Uzal, Levent Yılmaz, Ülkü Yetiş