Nilgun Ayman Oz

Inhibition of Volatile Fatty Acid Production in Granular Sludge from a UASB Reactor

Abstract Inhibition of volatile fatty acids (VFA), namely acetate, butyrate, and propionate, on the activity of acetoclastic methanogens within a full-scale upflow anaerobic sludge blanket (UASB) reactor was investigated using specific methanogenic activity (SMA) test. SMA tests were carried out at acetate concentrations in a range of 1000–25,000 mg l−1, butyrate concentrations in a range of 3000–25,000 mg l−1 and propionate concentrations between 500–10,000 mg l−1. Maximum potential methane production (PMP) rates were obtained as 389 ml CH4 gTVS−1 .d−1 at 3000 mg l−1 acetate concentration, 432 ml CH4gTVS−1.d−1 at butyrate concentration of 5000 mg l−1, and 162 mlCH4gTVS−1.d−1 at 1000 mg l−1 propionate concentration. App. 50% and 100% inhibition occurred at acetate concentrations of 13,000 mg l−1 and 25,000 mg l−1, butyrate concentrations of 15,000 mg l−1 and 25,000 mg l−1, and propionate concentrations of 3500 mg l−1 and 5000 mg l−1, respectively.

Ultrasound pretreatment for enhanced biogas production from olive mill wastewater

This study investigates applicability of low frequency ultrasound technology to olive mill wastewaters (OMWs) as a pretreatment step prior to anaerobic batch reactors to improve biogas production and methane yield. OMWs originating from three phase processes are characterized with high organic content and complex nature. The treatment of the wastewater is problematic and alternative treatment options should be investigated. In the first part of the study, OMW samples were subjected to ultrasound at a frequency of 20kHz with applied powers varying between 50 and 100W under temperature controlled conditions for different time periods in order to determine the most effective sonication conditions. The level of organic matter solubilization at ultrasound experiments was assessed by calculating the ratio of soluble chemical oxygen demand/total chemical oxygen demand (SCOD/TCOD). The results revealed that the optimum ultrasonic condition for diluted OMW is 20kHz, 0.4W/mL for 10min. The application of ultrasound to OMW increased SCOD/TCOD ratio from 0.59 to 0.79. Statistical analysis (Friedmans tests) show that ultrasound was significantly effective on diluted OMW (p<0.05) in terms of SCOD parameter, but not for raw OMW (p>0.05). For raw OMW, this increase has been found to be limited due to high concentration of suspended solids (SS). In the second part of the study, biogas and methane production rates of anaerobic batch reactor fed with the ultrasound pretreated OMW samples were compared with the results of control reactor fed with untreated OMW in order to determine the effect of sonication. A nonparametric statistical procedure, Mann-Whitney U test, was used to compare biogas and methane production from anaerobic batch reactors for control and ultrasound pretreated samples. Results showed that application of low frequency ultrasound to OMW significantly improved both biogas and methane production in anaerobic batch reactor fed with the wastewater (p<0.05). Anaerobic batch reactor fed with ultrasound pretreated diluted OMW produced approximately 20% more biogas and methane compared with the untreated one (control reactor). The overall results indicated that low frequency ultrasound pretreatment increased soluble COD in OMW and subsequently biogas production.

Effect of wastewater composition on methanogenic activity in an anaerobic reactor.

Abstract In this study, effects of a chemical synthesis-based pharmaceutical wastewater on activity of acetoclastic methanogens within a lab-scale anaerobic completely stirred tank reactor (CSTR) were investigated. The CSTR was initially fed with glucose and loaded up to an organic loading rate of 6 kg COD m−3 d−1 at which 92% soluble COD removal efficiency was achieved. Acetoclastic methanogenic activity was found to be 336 mL CH4 gTVS−1 d−1. The CSTR was then, fed with several dilutions of preaerated wastewater with glucose at 10% wt v−1, 30% wt v−1, and 70% wt v−1 ratios and followed by 100% wt v−1 preaerated wastewater. In the latter, 71% soluble COD removal efficiency was obtained and a maximum acetoclastic methanogenic activity was 166 mL CH4 gTVS−1 d−1. Finally, raw wastewater diluted with preaerated wastewater was fed into the CSTR in increasing ratios of 10–60% wt v−1. Total failure of anaerobic reactor was observed at 60% wt v−1 raw wastewater fed. The study was, therefore, discontinued due to poor acetoclastic methanogenic activity of reactor sludge which was totally distorted.

Ultrasound assisted biogas production from landfill leachate

The aim of this study is to increase biogas production and methane yield from landfill leachate in anaerobic batch reactors by using low frequency ultrasound as a pretreatment step. In the first part of the study, optimum conditions for solubilization of organic matter in leachate samples were investigated using various sonication durations at an ultrasound frequency of 20 kHz. The level of organic matter solubilization during ultrasonic pretreatment experiments was determined by calculating the ratio of soluble chemical oxygen demand (sCOD) to total chemical oxygen demand (tCOD). The sCOD/tCOD ratio was increased from 47% in raw leachate to 63% after 45 min sonication at 600 W/l. Non-parametric Friedmans test indicated that ultrasonic pretreatment has a significant effect on sCOD parameter for leachate (p<0.05). In the second part of the study, anaerobic batch reactors were operated for both ultrasonically pretreated and untreated landfill leachate samples in order to assess the effect of sonication on biogas and methane production rate. In anaerobic batch reactor feed with ultrasonically pretreated leachate, 40% more biogas was obtained compared to the control reactor. For statistical analysis, Mann-Whitney U test was performed to compare biogas and methane production rates for raw and pretreated leachate samples and it has been found that ultrasonic pretreatment significantly enhanced biogas and methane production rates from leachate (p<0.05) in anaerobic batch reactors. The overall results showed that low frequency ultrasound pretreatment can be potentially used for wastewater management especially with integration of anaerobic processes.

Microbial Population Dynamics in an Anaerobic CSTR Treating a Chemical Synthesis-Based Pharmaceutical Wastewater

Abstract Effects of a chemical synthesis based pharmaceutical wastewater on performance of an anaerobic completely stirred tank reactor (CSTR), activity of acetoclastic methanogens and microbial composition were evaluated under various influent compositions. Initially, the CSTR was fed with glucose up to an organic loading rate (OLR) of 6 kg COD/m3 · d corresponding to an F/M ratio of 0.43 with a hydraulic retention time (HRT) of 2.5 days. A COD removal efficiency of 92% and a methane yield of 0.32 m3 CH4/kg CODremoved were achieved whilst specific methanogenic activity (SMA) was found to be 336 mL CH4/gTVS · d. After the CSTR was fed with pre-aerated wastewater diluted by glucose in different dilution ratios of 10% (w/v), 30% (w/v), 70% (w/v), and 100% (w/v) pre-aerated wastewater, gradual decreases in COD removal efficiency to 71%, methane yield to 0.28 m3CH4/kg CODremoved and SMA to 166 mL CH4/gTVS · d occurred whilst volatile fatty acid concentration reached to 1474 mg/L. After the raw wastewater diluted with the pre-aerated wastewater was fed into the CSTR in increasing ratios of 10% (w/v), 30% (w/v), and 60% (w/v), there was a proportional deterioration in performance in terms of COD removal efficiency, methane yield and acetoclastic methanogenic activity. Epifluorescence microscopy of the seed sludge revealed that Methanococcus-like species, short, and medium rods were found to be equally dominant. The short and medium rod species remained equally dominant groups in the CSTR throughout the feeding regime whilst Methanococcus-like species and long rods were found to be in insignificant numbers at the end of the study. Changes in archael diversity were determined using molecular analyses such as polymerase chain reaction (PCR), and denaturent gradient gel electrophoresis (DGGE). Results showed that overall archeal diversity did not change much whereas changes in composition of eubacterial population occurred.

Inhibition effect of isopropanol on acetyl-CoA synthetase expression level of acetoclastic methanogen, Methanosaeta concilii.

Isopropanol is a widely found solvent in industrial wastewaters, which have commonly been treated using anaerobic systems. In this study, inhibitory effect of isopropanol on the key microbial group in anaerobic bioreactors, acetoclastic methanogens, was investigated. Anaerobic sludges in serum bottles were repeatedly fed with acetate and isopropanol; and quantitative real-time PCR was used for determining effect of isopropanol on the expression level of a key enzyme in acetoclastic methane production, acetyl-CoA synthetase of Methanosaeta concilii. Active Methanosaeta spp. cells were also quantified using Fluorescent in situ hybridization (FISH). Transcript abundance of acetyl-CoA synthetase was 1.23±0.62×10(6) mRNAs/mL in the uninhibited reactors with 222 mL cumulative methane production. First exposure to isopropanol resulted in 71.2%, 84.7%, 89.2% and 94.6% decrease in mRNA level and 35.0%, 65.0%, 91.5% and 100.0% reduction in methane production for isopropanol concentrations of 0.1 M, 0.5 M, 1.0 M and 2.0 M, respectively. Repeated exposures resulted in higher inhibitions; and at the end of test, fluorescent intensities of active Methanosaeta cells were significantly decreased due to isopropanol. The overall results indicated that isopropanol has an inhibitory effect on acetoclastic methanogenesis; and the inhibition can be detected by monitoring level of acetyl-CoA transcripts and rRNA level.

Analysis of Methanogenic Archaeal and Sulphate Reducing Bacterial Populations in Deep Sediments of the Black Sea

In this study, the distribution, morphology and relative abundance of Sulfate Reducing Bacterial (SRB) and Methanogenic Archaeal (MA) populations in the Black Sea sediments were investigated by using in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes. Results were discussed with respect to the characteristics of sampling points. MA and SRB showed a great diversity in all sediment samples. Higher abundance of MA (20–30%) and SRB (30–35%) populations were observed within the sediments from deeper parts of the Black Sea than the shallower parts (10–11% MA and 13–14% SRB). Desulfobotulus, Desulfosarcina and Desulfococcus groups were the most commonly detected SRB groups in the Black Sea sediments. Relative percentage of these SRB groups within sediments from deeper parts of the Black Sea was in a range of 17–21% whereas that of was in a range of 4–5% within the sediments from the shallower parts. Order Methanococcales were the dominant methanogenic group in all samples. Relative percentages of order Methanococcales were in a range of 8–12% and 4–5% within sediments from deeper parts and the coastal parts of the Black Sea, respectively.

Changes in Acetoclastic Methanogenic Activity and Microbial Composition in an Upflow Anaerobic Filter

Changes in the acetoclastic methanogenic activity in the effluentfrom an upflow anaerobic filter (UFAF) were studied throughout a 36 week operating period. The UFAF formed the second phase of a two-phase laboratory-scale anaerobic treatment system. TheSpecific Methanogenic Activity (SMA) test was used to measurethe acetoclastic methanogenic activity of the biomass washed outfrom the UFAF. Throughout the operating period, the SMA testswere carried out at different organic loading rates (OLR) up to6.7 kg COD m-3 d-1 and upflow velocities (UV), 5 m d-1 and 15 m d-1. The results showed that thebiomass washed out from the UFAF consisted of up to 55%(considered as a draft value) acetoclastic methanogens producing550 mI CH4 g-1 VSS d-1. This high acetoclasticmethanogenic activity measured in the effluent might have beendue to the existence of Methanosaeta (formerly Methanothrix) species. Towards the end of operation,Epifluorescence Microscopic examinations in the effluent revealedthat Methanococcus species were the most dominant groupfollowed by medium rods and short rods, filaments and long rodsand the least dominant Methanosarcina species. Theperformance of the UFAF was not adversely affected by the loss ofthe active biomass and changes in their composition. The UFAFsystem achieved over 85% COD removal efficiency at thehighest OLR of 6.7 kg COD m-3 d-1 and UV of 15 m d-1. Throughout most of the operation, methane yield rangedfrom 0.28–035 m3 CH4 kg-1 CODremoved.

Volatile fatty acid production dynamics during the acidification of pretreated olive mill wastewater

This study focuses on the dynamics of VFA production from pretreated olive mill wastewater (OMW). Acidogenic anaerobic sequencing batch reactors (AcASBR) were operated with the pretreated OMW at hydraulic retention time (HRT) of 2days and pH of 5,5 for different organic loading rates (OLRs) ranging from 5gCOD/L.d to 40gCOD/L.d. VFA production reached to the highest value of about 27,000mg/L with the increase in the organic load applied (20gCOD/L.d). The highest acidification rate was calculated as 68%. Acetic acid was found to be as the dominant VFA compound for all stage of the study. At steady state, VFA production during a day-cycle period (24th hour) in AcASBR is also monitored, VFA production gradually increased after the 3rd and 6th hours (about 20%) and a rapid increase (about 40%) was observed reaching the maximum at the end of the cycle (24th hour).

Zeytin Karasuyunun Elektrokoagulasyon Ön Arıtımlı Tek Fazlı Anaerobik Arıtımı

Bu calisma kapsaminda Canakkale ili ve cevresi icin onemli bir cevre sorunu teskil eden zeytin karasuyunun tek fazli ardisik kesikli anaerobik reaktorler ile aritilabilirligi elektrokoagulasyon on aritimi kullanilarak incelenmistir. Elektrokoagulasyon on islemi sayesinde, karasudaki kirletici konsantrasyonlari, askida kati madde miktari basta olmak uzere cesitli kirletici parametreleri bazinda onemli bir giderim saglanmistir. On aritilmis karasu numuneleri tek fazli anaerobik reaktore beslenerek, anaerobik aritim verimliligi; cKOI giderimi, biyogaz olusumu ve metan icerigi acisindan incelenmistir. Hidrolik bekletme suresi 1 gun; camur bekletme suresi 20 gun; organik yukleme orani 1 gr KOI/gr UAKM-gun olarak 30 gun boyunca isletilen ardisik kesikli anaerobik reaktorde; ortalama %70 organik madde giderimi elde edilmistir. Es zamanli olarak gunluk ortalama %80 metan icerikli 1000 mL biyogaz olusumu saglanmistir. Isletme suresince metan uretim hizi ortalama 0,27 mL CH 4 /gr KOIgiderilen ve kumulatif metan gazi olusumu 19981 mL olarak tespit edilmistir. On aritimli tek fazli anaerobik aritim ile; karasuyun organik madde iceriginde buyuk oranda giderim elde edilmis, es zamanli olarak da temiz bir enerji kaynagi olan metan icerigi yuksek biyogaz eldesi saglanmistir. Bu calismanin bulgulari; elektrokoagulasyon gibi kisa sureli bir on aritim ile; karasuyun tek fazli anaerobik reaktore dogrudan beslenebildigini ayni zamanda bu sistemlerden yuksek verimi alinabilecegini gostermektedir.