Dilek Akman

Bioelectricity generation in continuously-fed microbial fuel cell: Effects of anode electrode material and hydraulic retention time

The main aim of this study is to investigate the bioelectricity production in continuously-fed dual chambered microbial fuel cell (MFC). Initially, MFC was operated with different anode electrode material at constant hydraulic retention time (HRT) of 2d to evaluate the effect of electrode material on electricity production. Pt electrode yielded about 642 mW/m(2) power density, which was 4 times higher than that of the MFC with the mixed metal oxide titanium (Ti-TiO2). Further, MFC equipped with Pt electrode was operated at varying HRT (2-0.5d). The power density generation increased with decreasing HRT, corresponding to 1313 mW/m(2) which was maximum value obtained during this study. Additionally, decreasing HRT from 2 to 0.5d resulted in increasing effluent dissolved organic carbon (DOC) concentration from 1.92 g/L to 2.23 g/L, corresponding to DOC removal efficiencies of 46% and 38%, respectively.

Treatment of azo dye-containing synthetic textile dye effluent using sulfidogenic anaerobic baffled reactor

This study aims at investigating azo dye reduction performance of a sulfidogenic anaerobic baffled reactor (ABR) for around 400 days. ABR was operated at 30 °C in a temperature-controlled room and hydraulic retention time (HRT) was kept constant at 2 days. The robustness of ABR was assessed under varying azo dye loadings and COD/sulfate ratios. Additionally, oxygen was supplied (1-2 L air/m(3)reactor min) to the last compartment to investigate the removal of azo dye breakdown products. ABR performed well in terms of COD, sulfate and azo dye removals throughout the reactor operation. Maximum azo dye, COD and sulfate removals were 98%, 98% and 93%, respectively, at COD/sulfate ratio of 0.8. Aeration created different redox conditions in last compartment, which enhanced the removal of COD and breakdown products. The adverse effects of aeration on azo dye reduction were eliminated thanks to the compartmentalized structure of the ABR.

Optimization of Combined Ozone/Fenton Process on Olive Mill Wastewater Treatment

The aim of this study was to investigate the applicability of Fenton process and combined ozone/Fenton process to remove color, soluble chemical oxygen demand (COD s ), phenol, and dissolved organic carbon (DOC) from real olive mill wastewater (OMW). The treatability of OMW was investigated in three different study parts. Initially, Fenton process was optimized under varying H 2 O 2 /Fe 2+ molar ratios ranging between 10 and 20 at the constant H 2 O 2 concentration of 0.5 mM. The H 2 O 2 /Fe 2+ molar ratio of 10 was found optimum providing high color (51.6 %), COD s (58%), DOC (27.9%) and phenol removals (93.9%). Further, combined ozone/Fenton process was applied under gradually increasing dosages of Fe 2+ and H 2 O 2 reagents at constant H 2 O 2 /Fe 2+ molar ratio of 10. The high color removal efficiency ( 51.6% color removal for Pt-Co) was obtained at the H 2 O 2 and Fe 2+ molar ratio of 0.5/0.05. Additionally, COD s , color, DOC and phenol removal efficiencies improved at increasing reagents concentrations. However, the color removal efficiency was adversely affected while no significant difference on COD s and phenol removal was observed at higher concentrations of molar concentrations above 0.5/0.05. Additionally, the results indicated that combined process enhanced treatment performance of OMW by 21%, 49% and 22% in terms of color, DOC and COD s removals, respectively, compared to only-Fenton process. In the rest of this study, combined ozone/Fenton process was optimized under varying ozonation time (60-120 min) at the optimum H 2 O 2 and Fe 2+ molar dosage of 0.5/0.05 obtained from previous parts. Ozonation time significantly affected the treatment performance, and optimum the reaction time was determined as 90 minute in terms of the high treatment productivity and low operating cost resulted from minimum ozone consumption and short reaction time.

Evaluation of Thiosulfate-Based Autotrophic and Mixotrophic Denitrification Performances under Different Operational Conditions

The aim of this study was to investigate the factors affecting the autotrophic and mixotrophic denitrification performances in sequencing batch reactor (SBR). Findings obtained from this study will shed light on the full-scale applicability of the autotrophic and mixotrophic denitrification processes in carbon deficient wastewaters. In this study, the effect of cycle time, varying concentrations of electron donor source and the addition of external organic carbon source was evaluated by sulfate, nitrate, nitrite, ORP and inorganic carbon parameters. Firstly, SBR was operated with thiosulfate (S2O3) based autotrophic denitrification process at different cycle times (8h-4h-2h). Further, autotrophic denitrification process was optimized the under varying S2O3NO3 ratios (1.5-1.25-1.0) at the optimum cycle time of 2h. The maximum nitrate removal efficiency of 84% was accomplished at operational conditions containing 2h cycle time and 1.5 S2O3/NO3 ratio. In the rest of the study,the impact of increasing C/N ratio by methanol supplementation (0.35-0.71.05)was evaluated on mixotrophic denitrification performance. It was observed that nitrate was completely consumed at the C/N ratio of 1.05 and nitrate removal rate improved with increasing methanol supplementation as organic carbon source.

Anaerobik Membran Biyoreaktörde TMP-Akı Değerlendirmesi

Membran biyoreaktor teknolojisi, yuksek aritma performansi, dusuk cevresel etkisi, aritilmis suyun tekrar kullanilabilmesi gibi avantajlarindan dolayi atiksu aritimi alaninda siklikla tercih edilmektedir. Membran biyoreaktor uygulamasinda membran performansinin degerlendirilebilmesi, surdurulebilir ve yuksek performansta aritim performansinin elde edilebilmesi icin en onemli faktorlerden biri membranin kirlenme egiliminin belirlenmesidir. Bu calismada cop sizinti suyu ve cesme suyu kullanilarak farkli mikroorganizma konsantrasyonlarinda transmembran basinci (TMP)-aki iliskisi ortaya koyulmustur. Membranin kirlenme egilimi, aki ve TMP davranisi incelenerek belirlenmistir. Calisma sonuclarina gore, suyun kirlilik seviyesi arttikca kritik aki azalmistir. Kritik aki; cesme suyu, mikroorganizma+cesme suyu iceren calisma kosullarinda, cop sizinti suyu+mikroorganizma iceren isletme kosullarinda, sirasiyla 78LMH, 40LMH, 15LMH olarak belirlenmistir. En yuksek membran tikanma hizi ise 12mbar/dk olarak belirlenmistir.

Various oxygen loadings for oxidation of methane as electron donor source in membrane biofilm reactor for wastewater treatment

The aim of this study is to investigate the aerobic methane oxidation (AME), a process potentially useful for wastewaters treatment using methane as external electron donor in membrane biofilm reactor (MBfR). MBfR was operated at different O2:CH4 ratios (0.25-1) to provide optimum reactor conditions for denitrification which will be held in subsequent studies. According to our results, none of the dissolved organic metabolites or methanol was detected by analytical techniques during methane oxidation studies. However, study findings played a key role in selecting the suitable environmental conditions for denitrification. The O2:CH4 ratio of 0.35 was found optimum reactor conditions providing safety gas mixtures and non-methane containing gas outlet hence without methane losses to the atmosphere.

Biocathode application in microbial fuel cells: Organic matter removal and denitrification

The aim of this study is to investigate bioelectricity generation using a dual chambered biocathode microbial fuel cell (MFC). In this study, the effect of cathode influent nitrate concentration was investigated on power generation and wastewater treatment performance. Acetate was used as readily biodegradable carbon and electron donor source for microorganisms into anodic chamber, corresponding to 1000 mg/L influent COD. The biocathode MFC performance was evaluated for around 75 days following 360 days microorganism adaptation period. COD removal efficiency was 75% and slightly affected from the varying influent nitrate concentrations. However, autotrophic denitrification efficiency was adversely affected by increasing influent nitrate concentration and the maximum nitrate removal efficiency of around 70% was observed at the influent nitrate concentration of 50 mgNO-3/L. Additionally, the increasing nitrate concentration from 25 to 50 mg/L resulted in increasing the power density which approached to around 4 W/m2.