Bulent Mertoglu

Community Changes During Start-up in Methanogenic Bioreactors Exposed to Increasing Levels of Ammonia

To investigate the methanogenic population dynamics during the start-up under gradually increasing free ammonia levels, five mesophilic UASB reactors seeded with different sludges were operated for 140 days. Changes in the methanogenic community investigated by using 16S rDNA/rRNA based molecular methods such as denaturing gradient gel electrophoresis (DGGE), fluorescent in-situ hybridization (FISH), cloning and DNA sequencing. Free ammonia nitrogen (FAN) in the reactors was gradually increased from 50 to 130 mg l-1 by increasing total ammonia nitrogen (TAN) from 1000 to 2500 mg l-1 in the feed and keeping reactor pH at 7.7 in the active zone. Even at highest FAN level, COD and VFA removal efficiencies above 90 and 98% were obtained, respectively. However, Methanosaeta-related species mainly prevailing in seed sludges were substituted for Methanosarcina as the abundant methanogens although reactor performances were almost comparable and constant.

Identification and quantitative evaluation of nitrogen-converting organisms in a full-scale leachate treatment plant

The presence of ammonia nitrogen in landfill leachates poses a significant problem for treatment plant operators. The nitrification-denitrification process mostly carries out the nitrogen conversion in biological treatment systems. However, recent research shows that other processes by anaerobic ammonia-oxidizing bacteria (Anammox) and ammonia-oxidizing archaea (AOA) were also responsible for the removal of nitrogen in biological systems. In this study, the nitrogen-converting microorganisms in the Bursa Hamitler Leachate Treatment Plant were identified and monitored by using molecular tools. Fluorescent in situ hybridization (FISH) and slot-blot hybridization results showed that the Nitrosomonas and Nitrospira species were the dominant ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), respectively. Quantitative real-time PCR results indicated that AOB, NOB, AOA and Anammox bacteria exist in the leachate treatment plant. However, the removal of ammonia can be ascribed mainly to nitrification because AOB (1.5%) and NOB (11.3%) were predominant among all nitrogen-converting bacteria. The results of the phylogenetic analysis based on amoA and 16S rDNA gene revealed that the uncultured bacterium clone 4-24, Kuenenia stuttgartiensis genome fragment KUST_E and the uncultured Crenarchaeota clone NJYPZT-C1 belong to AOB, Anammox and AOA populations, respectively, and were the dominant species in their cluster.

Solidification/stabilization of landfill leachate concentrate using different aggregate materials

The application of reverse osmosis for the treatment of landfill leachate is becoming widespread in Turkey as well as in Europe. A major drawback of this process is the production of concentrate, which could be as much as 30% of the feed stream, and high concentrations of salts and contaminants. The reverse osmosis concentrate is disposed of by using several methods including re-infiltration, drying, incineration and solidification/stabilization. In this study, solidification/stabilization (S/S) technology was studied for the treatment of reverse osmosis concentrate produced from landfill leachate. In order to benefit from its capability to absorb heavy metals, ammonia and some other pollutants, zeolite and different aggregate materials were used in solidification experiments. Main pollutants in the leachate concentrate, TOC, DOC, TDS and ammonia were successfully solidified and approximately 1% of TOC, DOC, TDS and ammonia remained in the eluate water. The results indicated that the landfill disposal limits could be attained by solidification/stabilization process.

Monitoring of population shifts in an enriched nitrifying system under gradually increased cadmium loading

The 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 15mg/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.

Spatial and temporal analysis of black carbon aerosols in Istanbul megacity.

Black carbon (BC) is an important component of particulate matter due to its effects on human health and climate. In this study, we present the first BC concentrations measured in the Istanbul megacity (~15 million inhabitants). Two measurement campaigns have been conducted to measure BC and fine particulate matter (PM2.5) concentrations at four locations, characterized by different traffic densities. In the first campaign, BC daily mean concentrations have been found to be between 4 μg/m(3) and 10 μg/m(3). In the second campaign, BC and PM2.5 have been measured at the site with the highest traffic density for an entire year. Annually averaged BC contributes by 38 ± 14% to the PM2.5 levels (annual average BC: 13 μg/m(3) and PM2.5: 36 μg/m(3)). Diurnal variations of BC concentrations followed those of traffic density (correlation coefficient of 0.87). These measurements are essential to identify the sources of BC and PM2.5 concentrations in Istanbul and develop mitigation measures.

Investigation of nitrogen converters in membrane bioreactor

In this study, the activity and diversity of nitrogen converters, ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), ammonia-oxidizing archaea (AOA) and Anammox bacteria in a pilot-scale membrane bioreactor (MBR) were investigated and monitored using amoA and 16S rDNA-based molecular tools. The pilot-scale MBR (100 m3/day) was located inside the full-scale Pasakoy Advanced Wastewater Treatment Plant (WWTP), and operated for approximately 5 months without sludge purge. During 148 days of operation, volatile suspended solids (VSS) concentration increased from 2,454 mg/L to 10,855 mg/L and the average organic carbon and ammonia nitrogen removal rates were 92% and 99%, respectively. Real-time PCR results indicated that the fraction of AOB increased from 2.94% to 4.05% when VSS concentration reached to 3,750 mg/L throughout 148 days of operation. At higher VSS concentrations, the fraction of AOB declined gradually to 1.15% while the fraction of Nitrospira population was varied between 8.23 and 13.01%. However, significant change or any positive and negative correlations between VSS concentration and Nitrospira population were not observed in this period. The phylogenetic analysis revealed that MBR harbored diverse AOB community which was related to the Nitrosomonas and Nitrosospira lineage. Candidatus Nitrospira defluvii was the only detected NOB in this study.

Molecular Analysis of Microbial Communities in Nitrification and Denitrification Reactors Treating High Ammonia Leachate

Abstract Molecular analysis of microbial populations in two bench-scale nitrification and denitrification reactors fed with high ammonia landfill leachate was conducted in this study by using DGGE, cloning, and FISH techniques in addition to classical efficiency control parameters. Nitrification tank was operated with a computer-controlled alkalinity dosing system to supply the alkalinity intermittently as consumed on the basis of on-line pH monitoring. By keeping the pH at 7.0 with this system, 99% nitrification efficiency and rates of about 0.14–0.18 mg -N/mgVSS day were obtained. Meanwhile, as ammonia oxidizing bacteria Nitrosomonas and Nitrosococcus mobilis-like cells and as nitrite oxidizing bacteria Nitrobacter-related cells were intensively indicated. Moreover, some aerobic denitrifiers as Thauera species were also identified. After the termination of pH adjustment in the preceding anaerobic reactors, nitrification tank was loaded with more biodegradable COD as a result of reduced COD removal in anaerobic reactors. Microbial diversity was immediately affected from this alteration and heterotrophic carbonaceous bacteria and aerobic denitrifiers have dominated. To provide the former high efficiencies, retention time has increased from 24 to 48 h and a second pump dosing HCl was included to the automatic control system. Subsequent to these precautions, numbers of ammonia (Nso190) and nitrite oxidizing bacteria (NIT3) were comparatively increased. In denitrification system, about 98% denitrification efficiencies were obtained at 2000 mg/L NO x -N concentrations if sodium acetate was supplied as carbon source. Meanwhile, with 20 gVSS/l biomass concentration, denitrification rates of about 1.34 mgNO x -N/mgVSS day were obtained. All sludge samples have represented similar DGGE patterns and Paraccoccus-related species were identified as dominant denitrifying bacteria.

Long-term assessment of nitrification in a full-scale wastewater treatment plant

In this study, long term nitrification performances and microbial composition in a full-scale oxidation ditch type wastewater treatment plant (WWTP) were monitored and evaluated using different molecular methods; fluorescent in situ hybridization (FISH), slot-blot hybridization and quantitative real-time polymerase chain reaction (PCR) method. In situ and membrane hybridization results indicated that Nitrosomonas species were identified as the dominant ammonia oxidizing bacteria and Nitrospira related species were detected as the prevailing nitrite oxidizing bacteria in a full-scale wastewater treatment plant throughout 2 years of operation. Real-time PCR using the LightCyclerinstrument has been developed for the quantification of ammonia monooxygenase (amoA) and 16S rRNA genes. Results suggest that real-time PCR analysis, amoA/16S rRNA ratio, is an alternative method to understand nitrifying bacterial population and activity in wastewater treatment plant compared with the FISH and slot-blot hybridization assays. The autotrophic/heterotrophic bacterial ratio and their influence on reactor performances were investigated using real-time PCR amoA/16S rRNA gene copy ratios and the results showed that this ratio varied from 3.6% to 8.3% during operational period.

Comparative Analysis of Nitrifying Bacteria in Full–Scale Oxidation Ditch and Aerated Nitrification Biofilter by Using Fluorescent In Situ Hybridization (FISH) and Denaturing Gradient Gel Electrophoresis (DGGE)

In this study, nitrification performances and composition of nitrifying populations in a full–scale oxidation ditch and a high–rate submerged media nitrification biofilter were comparatively analyzed. In addition to different reactor configurations, effects of differing operational conditions on the nitrification efficiency and bacterial diversity were also explored and evaluated thoroughly. In microbial analysis of sludge samples fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) techniques were used complementary to each other. The extended aeration oxidation ditch subjected to the study is operated as a nitrogen and phosphorus removal system consisting of anaerobic, anoxic, and aerobic zones. The high–rate submerged media aerated filter is operated as nitrification step following the conventional activated sludge unit and the nitrified wastewater is discharged to the sea without complete nitrogen removal. In situ hybridization results have indicated that Nitrosomonas–like ammonia oxidizing and Nitrospira–related nitrite oxidizing bacteria were intensively present in vigorous flocs in nitrification biofilter while carbonaceous bacteria belong to beta subclass of Proteobacteria were considerably dominant in oxidation ditch. Low quantities of nitrifiers in oxidation ditch were also confirmed by the dissimilarity in intensive bands between two systems obtained with DGGE analysis.

Case study of PM pollution in playgrounds in Istanbul

In a world where at least 50% of the population is living in urban environments, air pollution and specifically particulate matter (PM) have become one of the most critical issues for human health. Children are more susceptible than adults to air pollution and its adverse effects because they inhale and retain larger amounts of air pollutants per unit of body weight. In this study, PM pollution, particularly PM10 and PM2.5, at selected playgrounds were investigated in Istanbul city. Istanbul is a megacity of over 15 million inhabitants, and on-road traffic is increasing rapidly (over 3 million vehicles on the road). To estimate the effect of traffic emissions on children, the location of the playgrounds were selected according to traffic density. Measurements were carried out at five different playgrounds throughout the city in 2009. Field results show that the values of PM10 and PM2.5 have reached critical limits at the playgrounds close to the main roads, especially at P-1. Thus, we focused on this location and investigated a source other than traffic emissions. One of the episode days has been observed on 5–7 March 2009. Evaluations of meteorological events are very important to determine air pollution sources and their long-range transport. Therefore, the Weather Research and Forecasting model (WRF) was used to simulate and forecast meteorological parameters and the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) applied to investigate long-range transport. According to the WRF model outputs, there was a low-pressure system over Geneva gulf on the 500-hPa level, and its core had been located over Britain on 5 March 2009 00UTC. The system had been sweeping dust from the Sahara Desert and carrying the air particles over Istanbul. Similarly, backward HYSPLIT analysis showed that air particles had moved through Istanbul from Northern Africa.