Person: SEMERCİ, NESLİHAN
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SEMERCİ
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NESLİHAN
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Publication Metadata only Quantitative analysis of candidatus accumilibacter phosphatis on lab scale denitrifying phosphorus removal sequencing batch reactors(2012-08-19) KOCAMEMİ, BİLGE; SEMERCİ, NESLİHAN; Esen E., DİTYAPAK D., KURT H., Kumru M., KOCAMEMİ B., SEMERCİ N., AKARSUBAŞI A. T.Publication Metadata only Evaluation of oxic and anoxic phosphate removal in a post-denitrification system(CURRENT BIOLOGY LTD, 2011) KOCAMEMİ, BİLGE; Semerci, Neslihan; Bakici, Nevin; Kocamemi, Bilge AlpaslanPublication Metadata only Modelling the relative toxicity of metals on respiration of nitrifiers using ion characteristics(TAYLOR & FRANCIS LTD, 2009) SEMERCİ, NESLİHAN; Sacan, M. T.; Cecen, F.; Erturk, M. D.; Semerci, N.The effects of eight transition metals were studied in a nitrifying system to investigate the relationship between the ionic characteristics of metals and their toxicity to nitrifiers. The cumulative oxygen consumption and the cumulative carbon dioxide production were monitored throughout each respirometric batch run to determine the toxicity of metals to nitrifiers. Several quantitative cationic-activity relationship (QCAR) models were developed on the basis of these different toxicity endpoints using quantum chemical descriptors. Descriptors were calculated with density functional theory (DFT) at the B3LYP/LANL2DZ level using the Gaussian 03W software. Additionally, the same descriptors were recalculated using another basis set, B3LYP/SDD, to test the impact of the basis set on prediction of toxicity. Of the calculated descriptors, mainly the gaseous phase descriptors explained significant variances in both toxicity endpoints. However, the energy of the polarized solute-solvent (EPSS) was the most important common descriptors in modelling labile toxicity. A combination of the aqueous phase energy of the highest occupied molecular orbital (EHOMO(aq)) and the maximum value for the energy of the lowest unoccupied molecular orbital of the most important metal species (ELUMOCmax) produced the best two-descriptor model for both pTO2 and pTCO2. The electron donor/acceptor ability of metals and the electron acceptor ability of metal species (ELUMOCmax) seemed to be important in explaining toxicity in aqueous media regardless of the measured endpoints for nitrifiers.Publication Metadata only Combined and individual applications of ozonation and microwave treatment for waste activated sludge solubilization and nutrient release(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2019) SEMERCİ, NESLİHAN; Cosgun, Sevil; Semerci, NeslihanThis study focused on the separate and combined applications of ozonation and microwave treatment to enhance the phosphorus and ammonia release from waste activated sludge. Twenty-six batch experiments were run with or without acidic (pH 2) and alkaline (pH 10) pretreatments and different ozone dosages. Also, microwave post treatments were applied to enhance phosphorus release efficiency. Results showed that ozonation is an effective technology for solubilization and release without any pre or post-treatment, reactive phosphorus content increased from 1.9 to 3.6 mg PO4-P/g MLSSin (89.5% increase) with 19.4% COD release. Alkaline pretreatment enhanced sludge solubilization and phosphorus release at most (23.9% COD release and 152.6% PO4-P increase); however, decreases in ammonia, calcium and magnesium concentrations pointed out a loss of a part of released phosphorus, due to struvite or apatite precipitation. Acidic pretreatment reduced the sludge solubilization during ozonation (10% COD release) but prevented the uncontrolled precipitation and enhanced the phosphorus release (115.8% PO4-P increase). For microwave treatment, acid pretreated sludge showed higher release than alkaline pretreated or neutral sludge. Among different process combinations, acid pretreatment/ozonation/microwave experiments have shown the highest sludge solubilization and nutrient release (48% COD release and 579% PO4-P increase); however, the difference between acid pretreatment/microwave and acid pretreatment/ozonation/microwave was not significant in terms of phosphorus release (479% PO4-P increase, p = 0.082). Thus, pH 2/microwave may be a cost-effective and feasible alternative for nutrient recovery from waste sludge. For struvite precipitation, pH 8.5 were determined as optimum level. Also using fine struvite particles as seed increased struvite precipitation efficiency.Publication Metadata only Monitoring of population shifts in an enriched nitrifying system under gradually increased cadmium loading(ELSEVIER SCIENCE BV, 2008) ÇALLI, BARIŞ; Mertoglu, Bulent; Semerci, Neslihan; Guler, Nuray; Calli, Baris; Cecen, Ferhan; Saatc, Ahmet MeteThe changes in nitrifying bacterial population under cadmium loading were monitored and evaluated in a laboratory scale continuous-flow enriched nitrification system. For this purpose, the following molecular microbiological methods were used: slot-blot hybridization, denaturing gradient gel electrophoresis (DGGE), real-time PCR followed by melting curve analysis, cloning and sequence analysis. The initial cadmium concentration was incrementally increased from 1 to 10mg/l which led to a drop in ammonia removal efficiency from 99 to 10%. inhibition was recovered when cadmium loading was stopped. During the second application of cadmium. nitrifying population became more tolerant. Even at 15 mg/l Cd, only a minor inhibition was observed. To investigate the variations in ammonia and nitrite oxidizing bacteria populations in a period of 483 days, ammonia monooxygenase (amoA) and 16S rRNA genes-based molecular techniques were used. An obvious shift was experienced in the diversity of ammonia oxidizers after the first application of 10mg/l Cd. Metal-tolerant ammonia oxidizing species became dominant and the microbial diversity sharply shifted from Nitrosomonas and Nitrosococcus sp. to Nitrosospira sp. which were observed to tolerate higher cadmium loadings. This result indicated that the extent of nitrification inhibition was not only related to the metal concentration and quantity of microorganisms but also depended on the type of species. (C) 2008 Elsevier B.V. All rights reserved.Publication Metadata only Importance of cadmium speciation in nitrification inhibition(ELSEVIER, 2007) SEMERCİ, NESLİHAN; Semerci, Neslihan; Cecen, FerhanIn this study, the influence of Cd speciation on nitrification inhibition was investigated in batch suspended growth activated sludge systems which contain biomass enriched in terms of nitrifiers. For this purpose, parallel measurements of specific oxygen uptake rates (SOUR), ammonium utilization rates (q(NH4)-N) and Cd uptake were carried out. Cd speciation was adjusted with a strong complexing agent, ethylenediaminetetraacetic acid (EDTA). Free and biosorbed Cd concentrations were theoretically determined by using the MINEQL+ program and the Cd adsorption constant, whereas labile Cd was determined by voltammetric measurements. The presence of EDTA decreased nitrification inhibition by lowering the available Cd species and by preventing biosorption of Cd. Almost complete recovery from inhibition was attained by EDTA addition to nitrifying bacteria which were inhibited by Cd for a certain time. These results suggested that the sites sensitive to Cd were rather located on the surface of bacterial cell than inside. Nitrification inhibition depended on equilibrium concentrations of free (Cd2+), labile (Cd-volt) and biosorbed Cd (Cd-volt) and did not correlate with the total Cd. The measurement of labile metal by voltammetry in inhibition studies is a promising approach since it is easy to apply in practice. (C) 2007 Elsevier B.V. All rights reserved.Publication Metadata only Inhibition of respiration and distribution of Cd, Pb, Hg, Ag and Cr species in a nitrifying sludge(ELSEVIER, 2010) SEMERCİ, NESLİHAN; Cecen, Ferhan; Semerci, Neslihan; Geyik, Ayse GuelThe study investigated the inhibitory effects of the heavy metals Cd, Pb, Hg, Ag and Cr (as Cr3+ and Cr6+) on a nitrifying sludge. The aim was to assess the IC50 concentrations leading to 50% inhibition. The method is based on respiration of nitrifying sludge in the presence of these metals. Both O-2 consumption and CO2 production were taken into account. The order of the inhibitory effect was Ag > Hg > Cd > Cr3+ = Cr6+. Metal speciation was calculated in terms of free metal, inorganic metal complexes and bound metal. Pb largely precipitated and 50% inhibition was never reached. Ag was always in the form of the free ion or labile complexes. Hg had apparently a lower toxicity than Ag, since most of it was initially highly complexed with ammonia. Cd was present in the form of free ion and complexes which caused inhibition although a large part of them were precipitated. The inhibitory effects of trivalent chromium (Cr3+) and hexavalent chromium (Cr6+) were similar. The latter was present in the form of the anion CrO42- and was not taken up by biomass. The study highlighted that IC50 values alone do not have an explanatory power of inhibition unless speciation is also considered. (C) 2010 Elsevier B.V. All rights reserved.Publication Metadata only Effect of continuous Cd feeding on the performance of a nitrification reactor(SPRINGER, 2009) SEMERCİ, NESLİHAN; Semerci, Neslihan; Cecen, FerhanThe inhibitory effect of Cd on nitrification was investigated in a continuous-flow system with enriched nitrifying bacteria. The maximum specific ammonium utilization rate and the half-saturation constant were found as 671 mg NH4-N/g VSS day and 0.48 mg/l, respectively. In the case of continuous Cd input at 1 and 2.5 mg/l, nitrification was inhibited by 30% and 47%, respectively. Inhibition ranged from 20% to 40% and no further increase in inhibition was exhibited in new runs except at 10 mg/l influent Cd. At 10 mg/l influent Cd, specific ammonium utilization and nitrate production rates were inhibited by 90%. On the contrary, a serious nitrite accumulation was not observed during this period. When Cd feeding was stopped, recovery from inhibition was observed after 37 day which was seen by the improvement in ammonium utilization and nitrate production rates. A shift in microbial population from the initial Nitrosomonas sp. to the Cd-tolerant Nitrosospira sp. was observed in the recovery period from severe Cd inhibition. After the domination of Nitrosospira species, redosing at 10 mg/l and then at 15 mg/l did not affect the performance as before.Publication Metadata only Quantitative analysis of candidatus accumilibacter phosphatis on lab scale denitrifying phosphorus removal sequencing batch reactors(2012-08-19) SEMERCİ, NESLİHAN; KOCAMEMİ, BİLGE; Ergal İ., SEMERCİ N., KOCAMEMİ B., Kurt H., AKARSUBAŞI A. T.Publication Metadata only Effects of nitrite, oxygen and initial pH on biological phosphorus removal in a post-denitrification system(ELSEVIER SCIENCE BV, 2010) SEMERCİ, NESLİHAN; Semerci, Neslihan; Bakici, Nevin; Kocamemi, B. Alpaslan