Publications2007

Journal of Water Resources Planning and Management, Vol. 133, No. 2, March 1, 2007, 126 - 136

Title: Calibration and Verification of QUAL2E Using Genetic Algorithm Optimization
Authors: Recep Kaya Göktaş, Ayşegül Aksoy
Abstract:In this study, the QUAL2E model is linked with a genetic algorithm (GA) in order to conduct the calibration and verification of the model. The efficacy of the optimization model was tested for different observation data quality represented by the perfect and noisy data assumptions. Four cases were studied. In the first (base) case, calibration was conducted for the reach-variable reaeration coefficient (K2) and the sediment oxygen demand rate (K4). In the second case, the number of sampling points was increased. The third case investigated the impact of objective function formulation itself on the optimization model performance. Finally, a high number of parameters were calibrated using the weighted and unweighted objective functions. In general, it was not possible to reach the exact values of the parameters at all reaches. However, the resulting water quality profiles were satisfactory and close to the goal. The performance of the optimization model improved for better observation data quality and increased number of sampling points. Furthermore, it was observed that the objective function formulation impacted the performance of optimization, depending on the observation data quality. Results of the fourth case suggested that weighted objective function minimized the domination of water quality constituents with higher orders of magnitude in concentration values in search for the best solution.

Fuel 86 (2007) 1430–1438

Title: Combustion of olive cake and coal in a bubbling fluidized bed with secondary air injection
Authors: Murat Varol, Aysel T. Atımtay
Abstract:Combustion performances and emission characteristics of olive cake and coal are investigated in a bubbling fluidized bed. Flue gas concentrations of O2, CO, SO2, NOx, and total hydrocarbons (CmHn) were measured during combustion experiments. Operational parameters (excess air ratio (?), secondary air injection) were changed and variation of pollutant concentrations and combustion efficiency with these operational parameters were studied. The temperature profiles measured along the combustor column was found higher in the freeboard for olive cake than coal due to combustion of hydrocarbons mostly in the freeboard. Combustion efficiencies in the range of 83.6–90.1% were obtained for olive cake with ? of 1.12–2.30. For the setup used in this study, the optimum operating conditions with respect to NOx and SO2 emissions were found as 1.2 for ?, and 50 L/min for secondary air flowrate for the combustion of olive cake. ©2006 Elsevier Ltd. All rights reserved.

Renewable Energy 32 (2007) 750–757

Title: Biogas production potential from cotton wastes
Authors: A. Isci, G.N. Demirer
Abstract:The anaerobic treatability and methane generation potential of three different cotton wastes namely, cotton stalks, cotton seed hull and cotton oil cake were determined in batch reactors. In addition, the effects of nutrient and trace metal supplementation were also investigated. To this purpose biochemical methane potential (BMP) experiments were performed for two different waste concentrations, namely 30 and 60 g/l. The results revealed that cotton wastes can be treated anaerobically and are a good source of biogas. Approximately 65, 86 and 78 ml CH4 were produced in 23 days from 1 g of cotton stalks, cotton seed hull and cotton oil cake in the presence of basal medium (BM), respectively. BM supplementation had an important positive affect on the production of biogas. ©2006 Elsevier Ltd. All rights reserved.

Journal of Environmental Management 84 (2007) 484–493

Title: Cleaner production opportunity assessment for a milk processing facility
Authors: A. Özbay, G.N. Demirer
Abstract:Possible cleaner production (CP) opportunities for a milk processing facility were examined in this study. The CP concept and its key tools of implementation were used to assess the potential CP opportunities in the facility studied. The general production process and its resulting environmental loads were investigated by taking possible CP opportunities as the basis of study. The methodology developed for CP opportunity assessment in the milk processing facility covered two major steps: preparation of checklists to assist auditing and CP opportunity assessment, and implementation of the mass-balance analysis. For mass-balance analysis, measurements and experimental analysis of the mass flows were utilized to determine the inputs and outputs. Prepared checklists were utilized to determine waste reduction options that could be implemented. Selected opportunities were evaluated considering their environmental benefits and economic feasibility. The results of the study indicated that 50% of the service water used, 9.3% of the current wastewater (WW) discharge, 65.36% of the chemical use and the discharge of 181.9 kg/day of chemical oxygen demand (COD) and 20.7 kg/day of total suspended solids (TSS) could be eliminated and 19.6% of the service water used could be recycled/reused. © 2006 Elsevier Ltd. All rights reserved.

Bioresource Technology 98 (2007) 2089–2101

Title:Use of blast furnace granulated slag as a substrate in vertical flow reed beds: Field application
Authors:E. Asuman Korkusuz, Meryem Beklioğlu, Göksel N. Demirer
Abstract:Research was conducted at Middle East Technical University (METU), Ankara, Turkey in 2000 to determine whether a reed bed filled with an economical Turkish fill media that has high phosphorus (P) sorption capacity, could be implemented and operated successfully under field conditions. In batch-scale P-sorption experiments, the P-sorption capacity of the blast furnace granulated slag (BFGS) of KARDEM_IR Iron and Steel Ltd., Co., Turkey, was found to be higher compared to other candidate filter materials due to its higher Ca content and porous structure. In this regard, a vertical subsurface flow constructed wetland (CW) (30 m2), planted with Phragmites australis was implemented at METU to treat primarily treated domestic wastewater, at a hydraulic rate of 100 mm d-1, intermittently. The layers of the filtration media constituted of sand, BFGS, and gravel. According to the first year monitoring study, average influent and effluent total phosphorus (TP) concentrations were 6.61 ± 1.78 mg L-1 and 3.18 ± 1.82 mg L-1; respectively. After 12 months, slag samples were taken from the reed bed and P-extraction experiments were performed to elucidate the dominant P-retention mechanisms. Main pools for P-retention were the loosely-bounded and Ca-bounded P due to the material’s basic conditions (average pH > 7.7) and higher Ca content. This study indicated the potential use of the slag reed bed with higher P-removal capacity for secondary and tertiary treatment under the field conditions. However, the P-sorption isotherms obtained under the laboratory conditions could not be used favorably to determine the longevity of the reed bed in terms of P-retention. © 2006 Elsevier Ltd. All rights reserved.

Journal of Biotechnology 127 (2007) 716–726

Title: Biodegradation kinetics of 2,4-dichlorophenol by acclimated mixed cultures
Authors:Erkan Şahinkaya, Filiz B. Dilek
Abstract:The biodegradation kinetics of 2,4-dichlorophenol (2,4-DCP) by culture (Culture M) acclimated to mixture of 4-chlorophenol (4-CP) and 2,4-DCP and the culture (Culture 4) acclimated to 4-CP only were investigated in aerobic batch reactors. Also, pure strains isolated from mixed cultures were searched for their ability towards the biodegradation of 2,4-DCP. Culture 4 was able to completely degrade 2,4-DCP up to 80 mg/L within 30 h and removal efficiency dropped to 21% upon increasing initial concentration to 108.8 mg/L. When the Culture M was used, complete degradation of 2,4-DCP in the range of 12.5–104.4 mg/L was attained. A linear relationship between time required for complete degradation and initial 2,4-DCP concentrations was observed for both mixed cultures. It was observed that the Haldane equation can be used to predict specific degradation rate (SDR) (R2 > 0.99) as a function of initial 2,4-DCP concentrations and it adequately describes 2,4-DCP concentration profiles. Both of the mixed cultures settled well, which is important to maintain good removal efficiency for longer periods of time for real full-scale applications. Although the pure strains isolated from mixed cultures were found to have higher SDR of 2,4-DCP compared to mixed cultures, they did not settle well under quiescent conditions. © 2006 Elsevier B.V. All rights reserved.

Journal of Environmental Management 83 (2007) 427–436

Title: Effect of feeding time on the performance of a sequencing batch reactor treating a mixture of 4-CP and 2,4-DCP
Authors:Erkan Şahinkaya, Filiz B. Dilek
Abstract:This paper investigated the biodegradation kinetics of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) separately in batch reactors and mixed in sequencing batch reactors (SBRs). Batch reactor experiments showed that both 4-CP and 2,4-DCP began to inhibit their own degradation at 53 and 25 mgl-1, respectively, and that the Haldane equation gave a good fit to the experimental data because r2 values were higher than 0.98. The maximum specific degradation rates (qm) were 130.3 and 112.4 mgg-1 h for 4-CP and 2,4-DCP, respectively. The values of the half saturation (Ks) and self-inhibition constants (Ki) were 34.98 and 79.74 mgl-1 for 4-CP, and 13.77 and 44.46mg l-1 for 2,4-DCP, respectively. The SBR was fed with a mixture of 220 mg l-1 of 4-CP, 110mg l-1 of 2,4-DCP, and 300mg l-1 of peptone as biogenic substrate at varying feeding periods (0–8 h) to evaluate the effect of feeding time on the performance of the SBR. During SBR operation, in addition to self-inhibition, 4-CP degradation was strongly and competitively inhibited by 2,4-DCP. The inhibitory effects were particularly pronounced during short feeding periods because of higher chlorophenol peak concentrations in the reactor. The competitive inhibition constant (Kii) of 2,4-DCP on 4-CP degradation was 0.17 mgl-1 when the reactor was fed instantaneously (0 h feeding). During longer feedings, increased removal/loading rates led to lower chlorophenol peak concentrations at the end of feeding. Therefore, in multi-substrate systems feeding time plus reaction time should be determined based on both degradation kinetics and substrate interaction. During degradation, the meta cleavage of 4-chlorocatechol resulted in accumulation of a yellowish color because of the formation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), which was further metabolized. Isolation and enrichment of the chlorophenols-degrading culture suggested Pseudomonas sp. and Pseudomonas stutzeri to be the dominant species. © 2006 Elsevier Ltd. All rights reserved.

Biodegradation (2007) 18:427–437

Title: Modeling chlorophenols degradation in sequencing batch reactors with instantaneous feed-effect of 2,4-DCP presence on 4-CP degradation kinetics
Authors:Erkan Şahinkaya, Filiz B. Dilek
Abstract:Two instantaneously fed sequencing batch reactors (SBRs), one receiving 4-chlorophenol (4-CP) (SBR4) only and one receiving mixture of 4-CP and 2,4-dichlorophenol (2,4- DCP) (SBRM), were operated with increasing chlorophenols concentrations in the feed. Complete degradation of chlorophenols and high Chemical oxygen demand (COD) removal efficiencies were observed throughout the reactors operation. Only a fraction of biomass (competent biomass) was thought to be responsible for the degradation of chlorophenols due to required unique metabolic pathways. Haldane model developed based on competent biomass concentration fitted reasonably well to the experimental data at different feed chlorophenols concentrations. The presence of 2,4-DCP competitively inhibited 4-CP degradation and its degradation began only after complete removal of 2,4-DCP. Based on the experimental results, the 4-CP degrader’s fraction in SBRM was estimated to be higher than that in SBR4 since 2,4-DCP degraders were also capable of degrading 4-CP due to similarity in the degradation pathways of both compounds.

Journal of Hazardous Materials 142 (2007) 526–534

Title: Occurrence of disinfection by-products in low DOC surface waters in Turkey
Authors:Nuray Ateş, S. Şule Kaplan, Erkan Şahinkaya, Mehmet Kitiş, Filiz B. Dilek, Ülkü Yetiş
Abstract:A total of 29 surface waters from different regions of Turkey were sampled once a month during 2004. Filtered raw water samples were characterized, chlorinated and the concentrations of disinfection by-products (DBPs) were measured. All waters were low in DOC ranging from 0.91 to 4.42 mg/L. The range of annual average trihalomethanes (THMs) and haloacetic acids (HAAs) concentrations in all waters was 21–189 and 18–149 µg/L, respectively. Total mass contributions of halides in THMs and HAAs to absorbable organic halides (AOX) ranged between 10 and 56% in all waters on annual average basis, indicating that significant amounts of other DBPs are being formed in the majority of the tested waters. A strong linear correlation was obtained between the concentrations of THMs and HAAs. Rather poor correlations were found for THMs–AOX and HAAs–AOX levels. For both THMs and HAAs, chlorinated species dominated over brominated ones since the majority of water sources had very low bromide levels. While chloroform and trichloroacetic acid were the major THM and HAA compounds, respectively; the extent of formation and speciation of DBPs varied greatly by season and water source. No consistent general trends were observed in terms of seasonal variations in DBP levels, suggesting that the characteristics of NOM moieties and their chlorine reactivity vary by season in almost all waters tested. © 2006 Elsevier B.V. All rights reserved.

Desalination 215 (2007) 29–36

Title: Reuse of lagoon effluents in agriculture by post-treatment in a step feed dual treatment process
Authors:Devrim Kaya, Filiz B. Dilek, Celal F. Gökçay
Abstract:The main constraint in lagoon treatment is the high suspended solids (SS) in the effluents, which is primarily due to high concentrations of algal cells in the finished effluent. The objective of this study was to remove turbidity originating from algae present in oxidation pond effluents by an easy and inexpensive method. For this reason, a novel lab-scale step feed dual treatment (SFDT) process was developed and the effectiveness of the trickling filter (TF) unit within the system in removing algae and organic matter was investigated. The SFDT process developed in this study is a unique and inexpensive way to scavenge algae from oxidation pond effluents. As opposed to earlier and somewhat unsuccessful studies where pond effluent post treatment was tested on oncethrough trickling filters, in this study pond effluents were directed to a step fed TF, so as to provide a dual treatment. Step feeding provided the necessary substrate to maintain a biofilm in TF, thereby affecting organic particles interception. The stabilization pond was not simulated in the study since the main focus was on the behaviour of the TF unit. The hydraulic loading rate (HLR) (0.5–2–4 m3/m2 day), influent COD (150–550 mg/L) and influent Chl-a concentrations (250–600 µg/L) were selected as operational variables. It was observed that, in general, removal percentages for turbidity, Chl-a, SS and COD increased considerably with the decreasing HLR, such as the removal efficiency of Chl-a was increased from 89.4% to about 97% when HLR was decreased from 4 m3/m2 day to 2 m3/m2 day. As a result, trickling filter produced clear effluents, with less than 2 NTU and the removal efficiency of turbidity being higher than 88%, and also removal percentages for Chl-a were higher than 95% for most of the cases.

Desalination 215 (2007) 22–28

Title: Vacuum membrane applications in domestic wastewater reuse
Authors:Okan Tarik Komesli, Katharina Teschner, Werner Hegemann, Celal F. Gokcay
Abstract:A flat type membrane bioreactor (MBR) with a pore size of 0.038 µm and having a total surface area of 540 m2 was operated intermittently for over a year in METU campus at Ankara to treat domestic effluents from dormitories and academic village. At the first stage the MBR plant was operated continuously for 140 days with hydraulic retention times ranging between 18 and 22 h. During this period, sludge concentration increased from an initial 2.4 g/L to 21 g/L. The plant consistently produced fully nitrified effluents when DO was kept over 2.0 mg/L. Over 99.99% BOD5 removal and 95% COD removals were achieved in the system. When DO concentration was 2 mg/L and mixed liquor suspended solids, MLSS, concentration was 16 g/L, simultaneous nitrification and denitrification was observed in the system. The effluent turbidity, was always below 1 NTU, equal to or below that of tap water, and around 6–7 log coliform removals with close to zero/100 mL effluent counts were achieved.

Journal of Residuals Science & Technology, Vol. 4, No. 1—January 2007

Title: Use of a NaturalMineral for the Removal of Copper and Nickel from Aqueous Solutions to Reduce Heavy Metal Content of Precipitation Sludges
Authors:Volkan Çağın, Nihan Moralı and İpek İmamoğlu
Abstract:A major disadvantage of precipitation removal of heavy metals is the disposal of sludge having a high concentration of heavy metals, sometimes requiring disposal in hazardous waste landfills. A sorption based polishing step using natural sorbents following precipitation may be feasible to avoid costly disposal of hazardous sludge. This study investigates the applicability of the use of a natural zeolite, namely clinoptilolite, obtained from aWestern Anatolian deposit, in removing copper and nickel from aqueous solutions. Maximum achievable capacities were found as 0.31 meq Cu2+/g and 0.32meq Ni2+/g for as-received, and 0.55 meq Cu2+/g and 0.43meq Ni2+/g for conditioned clinoptilolite samples, respectively.Use of clinoptilolite for the removal of Cu2+ from precipitation effluents holds more potential for the purpose of meeting discharge standards. Metal removal mechanisms are also investigated via examination of exchangeable cations (Na+, K+, Mg2+, Ca2+) in the aqueous phase.

Environ Geol

Title: The effect of aquifer heterogeneity on natural attenuation rate of BTEX
Authors:Tuba Uçankuş¸ Kahraman Ünlü
Abstract:Monitored natural attenuation can be a viable option for remediation of groundwater contamination by BTEX compounds. Under the field conditions, the rate of contaminant mass attenuation through natural processes, such as biodegradation, to a large extent affected by the groundwater flow regime, which is primarily controlled by the aquifer heterogeneity. Numerical simulation techniques were used to describe quantitatively the relationship between biodegradation rate of BTEX and aquifer heterogeneity. Different levels of aquifer heterogeneity were described by random hydraulic conductivity fields (K) having different statistical parameters, the coefficient of variation (CV) and the correlation length (h). The Turning Bands Algorithm was used to generate such K fields. Visual MODFLOW/RT3D was used to simulate the fate and transport of dissolved BTEX plume within heterogeneous aquifers. The multispecies reactive transport approach described BTEX degradation using multiple terminal electron-accepting processes. First-order biodegradation rate constants were calculated from simulated BTEX plumes in heterogeneous flow fields. The results showed that aquifer heterogeneity significantly affected biodegradation rate; it decreased with increasing CV when h was in the range of up to 12 m, whereas it increased with increasing CV when h was greater than about 12 m. For well characterized aquifers, this finding could be of great value in assessing the effectiveness of natural attenuation during feasibility studies at BTEX contaminated sites.

Journal of Membrane Science 303 (2007) 72–79

Title: A new approach in assessing slurry filterability
Authors:Hande Yükseler,'İsmail Tosun, Ülkü Yetiş
Abstract:Up to date, sludge filterability has been characterized by the Ruth’s classical filtration theory and quantified by the well-known parameter specific cake resistance (SCR). However, the complexity of the actual phenomenon is clearly underestimated by the classical filtration theory and SCR is often not satisfactory in describing filterability. Although many scientific studies were conducted for a better analysis and understanding of the filtration theory, still a practically applicable solution to replace the classical theory for a better description of filterability has not been proposed yet. In the present study, filtration laws proposed by Hermans and Bredée, dating back to 1936, which have been extensively used in the membrane literature for the analysis of fouling phenomenon has been adopted for the analysis of filterability of sludge systems. The results clearly show that this approach is superior to the classical approach in terms of characterizing the filterability of sludge systems and provides a slurry specific characterization parameter to replace the commonly used SCR. © 2007 Elsevier B.V. All rights reserved.

Journal of Environmental Engineering, Vol. 133, No. 10, October 1, 2007, 947–954

Title: Effects of Bromide Ion and Natural Organic Matter Fractions on the Formation and Speciation of Chlorination By-Products
Authors:Nuray Ateş, Mehmet Kitiş, Ülkü Yetiş
Abstract:The impacts of bromide concentration and natural organic matter (NOM) characteristics on the formation and speciation of disinfection by-products (DBPs) in chlorinated NOM fractions were investigated. A total of 20 bulk water NOM fractions with a wide range of specific ultraviolet (UV) absorbance (SUVA254) values were obtained from a source water employing XAD-8 or XAD-4 resin adsorption in completely mixed batch reactors. SUVA was not a good predictor of DBP [trihalomethanes (THMs), haloacetic acids (HAAs), and adsorbable organic halogens (AOX)] formation and speciation. The destruction in the UV254 absorbance from chlorination did not correlate with DBP formation at any bromide level. NOM moieties which do not absorb UV light at 254 nm significantly contributed to DBP formation. Mass balance calculations on halogens using THMs, HAAs, and AOX data indicated that significant amounts of DBPs (>54% of AOX) other than THMs and HAAs were formed in NOM fractions with 60–110 µg/L bromide concentration. The relative occurrence of such other halogenated by-products decreased with increasing bromide concentrations up to 500 µg/L level. NOM in the studied water was more susceptible to the formation of brominated THM species as opposed to brominated HAAs. At constant dissolved organic carbon concentration, chlorine dose and pH, increasing bromide concentrations in NOM fractions increased the total concentrations of DBPs and resulted in a shift toward the formation of brominated species. Further, increasing bromide concentrations increased the spectrum of detected species (i.e., occurrence of all nine HAAs) and provided a competitive advantage to THM and HAA precursors in NOM over precursors of other DBPs.

WATER RESEARCH 41 (2007) 4139 – 4148

Title: Formation of chlorination by-products in waters with low SUVA—correlations with SUVA and differential UV spectroscopy
Authors:Nuray Ateş, Mehmet Kitiş, Ülkü Yetiş
Abstract:The formation of THMs and HAAs after chlorination of bulk water fractions of low-SUVA (specific UVabsorbance) surface waters was investigated, and the applicability of SUVA and differential UV spectroscopy for monitoring THMs and HAAs in such waters was evaluated. Samples from two reservoirs were fractionated employing XAD-8, XAD-4, MIEX® resin and granular activated carbon adsorption. A total of 83 bulk water NOM fractions (i.e., the remaining solutions after contact with the adsorbent or resin at various doses) were obtained and chlorinated.

Journal of Hazardous Materials 142 (2007) 526–534

Title: Occurrence of disinfection by-products in low DOC surface waters in Turkey
Authors:Nuray Ateş, S. Şule Kaplan, Erkan Şahinkaya, Mehmet Kitiş, Filiz B. Dilek, Ülkü Yetiş
Abstract:A total of 29 surface waters from different regions of Turkey were sampled once a month during 2004. Filtered raw water samples were characterized, chlorinated and the concentrations of disinfection by-products (DBPs) were measured. All waters were low in DOC ranging from 0.91 to 4.42 mg/L. The range of annual average trihalomethanes (THMs) and haloacetic acids (HAAs) concentrations in all waters was 21–189 and 18–149 µg/L, respectively. Total mass contributions of halides in THMs and HAAs to absorbable organic halides (AOX) ranged between 10 and 56% in all waters on annual average basis, indicating that significant amounts of other DBPs are being formed in the majority of the tested waters. A strong linear correlation was obtained between the concentrations of THMs and HAAs. Rather poor correlations were found for THMs–AOX and HAAs–AOX levels. For both THMs and HAAs, chlorinated species dominated over brominated ones since the majority of water sources had very low bromide levels. While chloroform and trichloroacetic acid were the major THM and HAA compounds, respectively; the extent of formation and speciation of DBPs varied greatly by season and water source. No consistent general trends were observed in terms of seasonal variations in DBP levels, suggesting that the characteristics of NOM moieties and their chlorine reactivity vary by season in almost all waters tested. © 2006 Elsevier B.V. All rights reserved.

Desalination 212 (2007) 103–113

Title: The most effective pre-treatment to nanofiltration for the recovery of print dyeing wastewaters
Authors:Göksen Çapar, Levent Yılmaz, Ülkü Yetiş
Abstract:This paper presents the determination of the best pre-treatment method to nanofiltration (NF) for the recovery of print dyeing wastewaters (PDW) of the carpet manufacturing industry. Chemical precipitation (CP) with optimum alum (Al2SO4.18H2O) dose was chosen among five alternatives; 1) Dead-end microfiltration (MF), 2) CP with optimum coagulant dose, 3) CP with low coagulant dose and polyelectrolyte aid, 4) CP with low coagulant dose followed by MF, 5) CP with high coagulant dose followed by ultrafiltration (UF). In the selected process, an optimum alum dose of 150 mg/L provided color and turbidity removal efficiencies of >90%. The effectiveness of the selected pre-treatment method for flux control in post NF was also tested. Perfect rejection of COD, color and turbidity was achieved in NF, accompanied by a stable flux decline of around 22%. Moreover, the flux decline was mainly due to concentration polarization rather than fouling, indicating reversible flux decline.