Biomedical subjects

D Orhon

Publications and source records attributed to D Orhon.

At least 19 recordsLinked to original sources

PubMed2007

Respirometric evaluation and modeling of glucose utilization by Escherichia coli under aerobic and mesophilic cultivation conditions.

The study presents a mechanistic model for the evaluation of glucose utilization by Escherichia coli under aerobic and mesophilic growth conditions. In the first step, the experimental data was derived from batch respirometric experiments conducted at 37 degrees C, using two different initial substrate to microorganism (S(0)/X(0)) ratios of 15.0 and 1.3 mgCOD/mgSS. Acetate generation, glycogen formation and oxygen uptake rate profile were monitored together with glucose uptake and biomass increase throughout the experiments. The oxygen uptake rate (OUR) exhibited a typical profile accounting for growth on glucose, acetate and glycogen. No acetate formation (overflow) was detected at low initial S(0)/X(0) ratio. In the second step, the effect of culture history developed under long-term growth limiting conditions on the kinetics of glucose utilization by the same culture was evaluated in a sequencing batch reactor (SBR). The system was operated at cyclic steady state with a constant mean cell residence time of 5 days. The kinetic response of E.coli culture was followed by similar measurements within a complete cycle. Model calibration for the SBR system showed that E. coli culture regulated its growth metabolism by decreasing the maximum growth rate (lower microH) together with an increase of substrate affinity (lower K(S)) as compared to uncontrolled growth conditions. The continuous low rate operation of SBR system induced a significant biochemical substrate storage capability as glycogen in parallel to growth, which persisted throughout the operation. The acetate overflow was observed again as an important mechanism to be accounted for in the evaluation of process kinetics.

Acetates↗

PubMed2006

Critical appraisal of respirometric methods for metal inhibition on activated sludge.

This paper evaluates the merit of oxygen uptake rate measurements for the assessment of metal inhibition on activated sludge. For this purpose, experiments are conducted to calculate EC50 levels of nickel and hexavalent chromium using the ISO 8192 procedure, yielding results that are highly variable and difficult to correlate, depending on the type of substrate and the initial food to microorganism ratio. Similar experiments based on continuous respirometric measurements to give the entire oxygen uptake rate profile provide a much better insight on the impact of inhibition on different biochemical processes taking place in the reactor. The results indicate that percent reduction of the amount of dissolved oxygen utilized after an appropriate reaction time is a much better index for the assessment of the inhibitory effects.

Chromium↗

PubMed2006

Performance evaluation of SBR treatment for nitrogen removal from tannery wastewater.

Performance of SBR treatment for nitrogen removal from tannery is evaluated for a wide range of wastewater temperature between 7 and 30 degrees C. A pilot-scale SBR unit fed with plain-settled wastewater is operated on site for this purpose. Effective nitrogen removal is sustained by adjustment of the sludge age from 28 to 5 days. Concentration profiles of nitrogen compounds within a selected complete SBR cycle during the steady state operation at different wastewater temperatures and sludge ages are evaluated by model simulation. System performance is also interpreted in terms of modeling and stoichiometric calculation. Additional nitrate loss was observed during aerobic period when the aeration intensity was reduced by the factor of 50%.

Industrial Waste↗

PubMed2005

The effect of temperature and sludge age on COD removal and nitrification in a moving bed sequencing batch biofilm reactor.

This study investigates the effect of temperature and the sludge age on the performance of a moving bed sequencing batch biofilm reactor (MBSBBR) for COD removal and nitrification. The experiments are conducted in a lab-scale MBSBBR operated at three different temperatures (20, 15 and 10 degrees C) with a synthetic feed simulating domestic sewage characteristics. Evaluation of the results revealed that removal of organic matter at high rates and with efficiencies over 90% was secured at all operation conditions applied. The nitrification rate was significantly influenced by changes in temperature but complete nitrification occurred at each temperature. The nitrification rates observed at 20 and 15 degrees C were very close (0.241 mg NO(x)-N/m2d, 0.252 mg NO(x)-N/m2 d, respectively), but at 10 degrees C, it decreased to 0.178 mg NO(x)-N/m2d. On the other hand, the biomass concentration and sludge age increased while the VSS/TSS ratios that can be accepted as an indicator of active biomass fraction decreased with time. It is considered that, increasing biofilm thickness and diffusion limitation affected the treatment efficiency, especially nitrification rate, negatively.

Biofilms↗

PubMed2005

Effect of primary sludge fermentation products on mass balance for biological treatment.

Laboratory batch experiments were conducted at 20 degrees C to investigate the potential of primary sludge fermentation for the generation of readily biodegradable substrate and to evaluate the effect of fermentation products on mass balance for organic carbon, nitrogen and phosphorus, emphasizing COD fractionation. Fermentation converted between 18 to 30% of the initial volatile suspended solids in the sludge into soluble biodegradable COD. The volatile fatty fraction of the soluble COD was approximately 85% after the fermentation process. The average volatile fatty acid composition in fermentation involved 50% acetic acid, 33% propionic acid, 9% butyric acid and 8% valeric acid, indicating that the most important volatile fatty acid obtained during the biological fermentation process was acetate with more than half of total VFA concentration, which is one of the most important carbon sources for denitrification and biological nutrient removal processes. The recoverable fraction of the fermented sludge supernatant could potentially increase the readily biodegradable COD content of the primary effluent by 5%, together with a potential increase of the soluble nitrogen and phosphorus content by 2%.

Fatty Acids, Volatile↗

PubMed2005

Evaluation of denitrification potential of rotating biological contactors for treatment of municipal wastewater.

In this study the effect of retention time and rotation speed in the denitrification process in two full-scale rotating biological contactors (RBC) which were operated parallel and fed with municipal wastewater is evaluated. Each rotating biological contactor was covered to prevent oxygen input. The discs were 40% submerged. On the axle of one of the rotating biological contactors lamellas were placed (RBC1). During the experiments the nitrate removal performance of the rotating biological contactor with lamellas was observed to be less than the other (RBC2) since the lamellas caused oxygen diffusion through their movement. The highest nitrate removal observed was 2.06 g/m2.d achieved by a contact time of 28.84 minutes and a recycle flow of 1 l/s. The rotation speed during this set had the constant value of 0.8 min(-1). Nitrate removal efficiency on RBC1 was decreasing with increasing rotation speed. On the rotating biological contactor without lamellas no effect on denitrification could be determined within a speed range from 0.67 to 2.1 min-1. If operated in proper conditions denitrification on RBC is a very suitable alternative for nitrogen removal that can easily fulfil the nutrient limitations in coastal areas due to the rotating biological contactors economical benefits and uncomplicated handling.

Bioreactors↗

PubMed2005

Recent practices on wastewater reuse in Turkey.

Reuse of wastewater for irrigational purposes in agriculture has been a widely applied practice all around the world compared to such applications in industries. In most of the developing countries, high costs of wastewater treatment stimulate the direct reuse of raw or partly treated effluent in irrigation despite the socio-cultural objections in some countries regarding religious rituals towards consuming wastewater. In Turkey, reuse applications in agriculture have been in use by indirect application by means of withdrawing water from the downstream end of treatment plants. Such practices affected the deterioration of surface water resources due to the lack of water quality monitoring and control. However, more conscious and planned reuse activities in agriculture have recently started by the operation of urban wastewater treatment plants. Turkey does not face any severe water scarcity problems for the time being, but as the water resources show the signs of water quality deterioration it seems to be one of the priority issues in the near future. The industrial reuse activities are only at the research stage especially in industries consuming high amounts of water. In-plant control implementation is the preferred effort of minimizing water consumption in such industries. The current reuse activities are outlined in the article forming an example from a developing country.

Agriculture↗

PubMed2005

Evaluation of the performance of the Tyson Foods wastewater treatment plant for nitrogen removal.

In this paper, the performance of the Tyson Foods wastewater treatment plant with an average flow rate of 6500 m3/d was evaluated before and after upgrading of the treatment system for nitrogen removal. This study was also covered with an additional recommendation of BIOWIN BNR program simulation after the modification period to achieve an additional nutrient removal. The results clearly show that the upgrading was very successful for improved nitrogen removal, with a 57% decrease on the total nitrogen discharge. There also were slight reductions in the discharged loads of biological oxygen demand, total suspended solids, ammonium and total phosphorus with denitrification, even though the effluent flow was higher during operation of the nitrogen removal configuration.

Bioreactors↗

PubMed2005

Biological treatability of raw and ozonated synthetic penicillin formulation effluent.

Chemical pre-treatment of synthetic Procaine Penicillin G (PPG) effluent with ozone (applied dose = 1440 mg/h; treatment duration = 60 min) at pH = 7 was investigated. Successive biological treatability studies were performed with raw, ozonated penicillin formulation effluent and synthetic readily biodegradable substrate as simulated domestic wastewater. The PPG effluent additions were adjusted to constitute approximately 30% of the total COD in the reactor. Ozonation of PPG effluent resulted in practically complete removal of the parent pollutant accompanied by 40% COD abatement. Speaking for the raw PPG effluent, prolonged acclimation periods were necessary to obtain significant COD removal efficiencies. Batch activated sludge treatment experiments and respirometric studies have demonstrated that the selection of true retention time is extremely crucial for having high amount of slowly hydrolysable substrate or complex wastewater, like pharmaceutical effluent. The effect of ozonation time on biological treatability performance of PPG has been evaluated in the study. Pre-ozonation of PPG effluent did not improve its ultimate biodegradability.

Anti-Bacterial Agents↗

PubMed2004

Effects of pH and substrate on the competition between glycogen and phosphorus accumulating organisms.

This article evaluates effects of pH and substrate on the competition between glycogen (GAOs) and phosphorus accumulating organisms (PAOs). A sequencing batch reactor system was operated for enhanced biological phosphorus removal (EBPR) with acetate as the sole carbon source and acetate added domestic wastewater at different influent acetate/phosphate ratios. Some batch tests were performed using acetate added domestic wastewater at different influent acetate, phosphate ratios, with different initial pH values of acetate and domestic wastewater mixture. The resulting experimental data supported the presence of GAOs for all tested HAC P ratios, especially under P limiting conditions for acetate as sole carbon source. Strong evidence is observed that acetate added domestic wastewater system had higher PAOs fraction than acetate system as sole source carbon, with using model components, namely substrate uptake, glycogen utilization and P release.

Bacteria↗

PubMed2004

Modelling and calibration of phosphate and glycogen accumulating organism competition for acetate uptake in a sequencing batch reactor.

This paper improves the modeling of enhanced biological phosphate removal, by introducing the mechanistic description of a mixed culture of glycogen and phosphate accumulating organisms competing for acetate, and glycogen metabolism of the latter. A new process stoichiometry is defined for the mixed culture based upon previously developed metabolic concepts and models. The proposed model is tested with and used for the calibration of experimental data generated by a sequencing batch reactor operated with acetate feeding at a P/Ac ratio of 0.05 mgP mg(-1)COD. The calibration yielded acceptable numerical results for all the model coefficients tested and supported the validity of selected metabolic relationships for process stoichiometry. It also defined conditions that allow the system to sustain glycogen accumulating organisms with significant impact on process behaviour and performance.

Acetates↗

PubMed2003

Operational strategies for a small wastewater treatment plant using OUR, microscopic analysis, and toxicity test.

This study was focused on determining the optimal operational conditions of a small domestic wastewater treatment plant (SWP) with a flow rate of 1000 m3 d(-1) using oxygen uptake rate (OUR) data, microscopic analyses, and effluent toxicity testing with Daphnia magna in parallel to wastewater characterization. Chemical analyses of nine samples, taken from different points of the treatment plant over a nine months period, presented strong domestic wastewater characteristics. The plant performance for meeting discharge standards was not sufficient enough for TP parameter. Aeration capacity and sludge recycle ratio were adjusted to improve the performance of the system and to prevent any operational problems, such as bulking. Although the inflow was 100% toxic, effluent toxicity following treatment was decreased to 5%. Filamentous bacteria were in "excessive" amount. The dominant filamentous bacteria species were determined as Nostocoioda limicola II. Reevaluation of the discharge limits with respect to nutrient removal, geographic location, and receiving water quality subject to treatment effluent discharges.

Animals↗

PubMed2003

Modification of Activated Sludge Model no. 3 considering direct growth on primary substrate.

This paper provides the structural framework for the proposed modified version of Activated Sludge Model No. 3 (ASM3), where direct heterotrophic growth on readily biodegradable substrate is included as a new process and provision is made so that growth on internal storage compounds is started sequentially, after the depletion of the external primary substrate pool. The results have provided strong indication that there was a need for considering direct growth on primary substrate as a significant biological mechanism.

Biodegradation, Environmental↗

PubMed2003

Estimation of stoichiometric and kinetic coefficients of ASM3 under aerobic and anoxic conditions via respirometry.

Activated Sludge Model No. 1 (ASM 1) has been used extensively for the design and simulation of biological treatment systems. Batch respirometric experiments have been described in the model for the determination of model coefficients and respirometric studies have been proved to be useful in kinetic parameter estimation and wastewater characterisation for ASM 1. Activated Sludge Model No. 3 (ASM3) has also introduced a number of kinetic and stoichiometric coefficients with the new processes defined in the model, also suggesting some default values. Recent studies on the application of ASM3 are limited to special cases in terms of parameter determination. Proper calibration of ASM3 parameters can be a difficult task without involving respirometric procedures as experimental tools. Respirometric batch tests were conveniently used in this study in order to estimate ASM3 parameters and the main kinetic and stoichiometric model coefficients were successfully and uniquely determined for aerobic and anoxic conditions for acetate.

Bioreactors↗

PubMed2003

Scientific basis for the design of small activated sludge systems.

The study presents an evaluation of the oxygen requirement and sludge production, modeled in terms of fundamental processes reflecting different biochemical transformations in activated sludge systems. Modern modeling concepts define substrate utilization and endogenous decay as major processes requiring final electron acceptors. Substrate and sludge components may be defined in terms of different parameters. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) are the traditional substrate parameters. COD also serves to define biomass along with volatile suspended solids (VSS) parameter. Estimation of oxygen requirement and sludge production for aerobic activated sludge systems covering basic biochemical processes are defined for different substrate and sludge parameters, considering that each calculation is associated with a different stoichiometry on the basis of a selected parameter set. The German regulations are examined and the biochemical bases of the coefficients in the regulatory expressions are set in terms of fundamental model constants.

Biomass↗

PubMed2003

Design procedure for carbon removal in contact stabilization activated sludge process.

The contact stabilization activated sludge process (CSASP) has been adopted and applied in full scale plants treating domestic sewage. Acquiring smaller volume thereby reducing costs and achieving the same treatment efficiency as the conventional activated sludge plants are the main advantages of the CSASP. This activated sludge modification is especially ideal for small to mid-scale plants where influent wastewater contains a high fraction of particulate COD. The simulation results reveal that the same amount of mass sludge can be retained in the system with almost 30% volume reduction compared to conventional activated sludge plants. It is also found that the CSASP treatment efficiency increases when the particulate COD fraction of an influent domestic wastewater increases. The most important process component in the design of CSASP is the sludge distribution factor (alpha) which directly affects the effluent characterization. Having most of the biomass in the stabilization reactor (meaning low alpha values) decreases the nominal hydraulic retention time (thetaHN) of the system. However the sludge distribution factor must be high enough to ensure an acceptable effluent quality.

Biomass↗

PubMed2003

Effect of temperature on the nitrogen removal performance of a sequencing batch reactor treating tannery wastewater.

The effect of temperature on the nitrogen removal performance of the sequencing batch reactor technology is evaluated for tannery wastewater. The study involved the operation of a pilot-scale sequencing batch reactor installed on site to treat the plain-settled effluent. The nitrogen balance of the system is observed for a wide temperature range between 9 to 30 degrees C. The results are evaluated by means of model calibration of COD, nitrate and ammonia nitrogen concentration profiles during cyclic operation. The fates of the major nitrogen parameters are also interpreted on the basis of fundamental stoichiometry for nitrification and denitrification.

Animals↗

PubMed2002

Effect of ozonation on the biological treatability of a textile mill effluent.

Ozonation applied prior to biological processes, has proved to be a very effective chemical treatment step mostly for colour removal when soluble dyes are used in textile finishing operations. Its impact on biological treatability however has not been fully evaluated yet. This study evaluates the effect of ozonation on the quality of wastewater from a textile mill involving bleaching and reactive dyeing of cotton and synthetic knit fabric. The effect of ozonation on COD fractionation and kinetic coefficients defining major biological processes is emphasised. The results indicate that the extent of ozone applied greatly affects the remaining organic carbon composition in the wastewater. The relative magnitude of different COD fractions varies as a function of the ozone dose. Ozonation does not however exert a measurable impact on the rate of major biological processes.

Coloring Agents↗