Ahmet Karagunduz

Influence of electrical field on COD removal and filterability of activated sludge

AbstractThree batch reactors were operated in order to investigate the effects of electrocoagulation and electrical field on chemical oxygen demand (COD) degradation rates, efficiencies, and filterability. The first reactor was operated with iron electrode, the second reactor was operated with relatively inert titanium electrode, and the last one was run as control without any electrical field. The electrical field application with iron electrodes increased the COD degradation rates at 0.5 and 2.5 V/cm with COD removals around 90%. However, the removal efficiencies decreased down to 70% at 5 V/cm. Increases in degradation rates were observed with titanium electrodes with time at all the three voltages. Activated sludge from the reactor with iron electrodes showed excellent filtration properties at 2.5 and 5 V/cm experiments. This was attributed to iron precipitates screening membrane foulants and preventing the formation of high resistive cake layer and pore structure rather than floc size increase. Elect...

Effect of sludge retention time on membrane bio-fouling using different type and pore size of membranes in a submerged membrane bioreactor

The objective of this study was to investigate the influence of sludge retention time (SRT) on membrane bio-fouling. An activated sludge reactor was operated at three different SRTs (10, 30, and 50 days). Submerged membrane experiments were performed when the mixed liquor suspended solids (MLSS) concentration reached the steady state conditions. MLSS concentrations reached the steady state at 3,109 ± 194, 6,209 ± 123 and 6,609 ± 280 mg/L for SRTs of 10, 30 and 50 days, respectively. The total soluble microbial products (SMP) were 20.1 ± 3.7, 16.2 ± 7.2 and 28.2 ± 8.4 mg/L at SRTs of 10, 30, and 50 days, respectively. The carbohydrate concentration in the supernatant was about two times more for SRT of 10 days than that for 50 days. The total amount of extracellular polymeric substances (EPS) extracted from the flocs were approximately 74.9 ± 11.9, 67.8 ± 15.0 and 67.5 ± 17.4 mg/g MLSS at three SRTs (10, 30, and 50 days) under the same organic loading rate. The viscosity of the biomass increased with the increasing SRT. The results of flux stepping tests showed that the membrane fouling at SRT 10 days was always higher than that of 30 and 50 days. Four different microfiltration membranes (cellulose acetate, polyethersulfone, mixed ester, and polycarbonate) with three different pore sizes (0.45, 0.22, 0.10 μm) were tested. Filtration resistances were determined for each membrane. Cake resistance was observed to be the most significant fouling mechanism for all membranes.

Influence of membrane fouling reducers (MFRs) on filterability of disperse mixed liquor of jet loop bioreactors.

The effects of membrane fouling reducers (MFRs) (the cationic polyelectrolyte (CPE) and FeCI(3)) on membrane fouling were studied in a lab-scale jet loop submerged membrane bioreactor (JL-SMBR) system. The optimum dosages of MFRs (CPE dosage=20 mg g(-1)MLSS, FeCI(3) dosage=14 mg g(-1)MLSS) were continuously fed to JL-SMBR system. The soluble and bound EPS concentrations as well as MLSS concentration in the mixed liquor of JL-SMBR were not changed substantially by the addition of MFRs. However, significant differences were observed in particle size and relative hydrophobicity. Filtration tests were performed by using different membrane types (polycarbonate (PC) and nitrocellulose mixed ester (ME)) and various pore sizes (0.45-0.22-0.1 μm). The steady state fluxes (J(ss)) of membranes increased at all membranes after MFRs addition to JL-SMBR. The filtration results showed that MFRs addition was an effective approach in terms of improvement in filtration performance for both membrane types.

Influence of surfactants on unsaturated water flow and solute transport

Surfactants can reduce soil water retention by changing the surface tension of water and the contact angle between the liquid and solid phases. As a result, water flow and solute transport in unsaturated soil may be altered in the presence of surfactants. In this study, the effects of a representative nonionic surfactant, Triton X-100, on coupled water flow and nonreactive solute transport during unsaturated flow conditions were evaluated. Batch reactor experiments were conducted to measure the surfactant sorption characteristics, while unsaturated transport experiments were performed in columns packed with 40–270 mesh Ottawa sand at five initial water contents. Following the introduction of surfactant solution, the rate of water percolation through the sand increased; however, this period of rapid water drainage was followed by decreased water percolation due to the reduction in soil water content and the corresponding decrease in unsaturated hydraulic conductivity behind the surfactant front. The observed changes in water percolation occurred sequentially, and resulted in faster nonreactive solute transport than was observed in the absence of surfactant. A one-dimensional mathematical model accurately described coupled water flow, surfactant, and solute transport under most experimental conditions. Differences between model predictions and experimental data were observed in the column study performed at the lowest water content (0.115 cm3/cm3), which was attributed to surfactant adsorption at the air-water interface. These findings demonstrate the potential influence of surfactants additives on unsaturated water flow and solute transport in soils, and demonstrate a methodology to couple these processes in a predictive modeling tool.

Investigation of membrane biofouling in cross-flow ultrafiltration of biological suspension

The main objective of this study was to investigate the fouling mechanism of various types of ultrafiltration membranes with different pore sizes by the cross-flow filtration of biological suspensions. The cross flow experiments were conducted using two different membrane types (cellulose-UC- and polyethersulfone-UP-) with three different molecular weight cut off (MWCO) (5, 10, 30 kDa for UC and 5, 10, 20 kDa for UP). The most fouling was observed in UC030 membrane for which the initial flux and the final flux values were 205 L/m2/h and 89 L/m2/h, respectively. Higher porosity caused greater initial flux that transported colloids and SMP fractions to the surface filing up the pores or pore openings and causing more fouling. Almost no drop was observed in flux values of the membranes of UC005, UC005 and UP010, indicating that almost no fouling were occurred for these membranes. This was a result of the accumulation of foulants in the pores or in the pore openings. As MWCO increased, higher membrane flux was observed, on the other hand, lower SMP rejections were achieved. UC membrane with MWCO of 30 kDa showed the most rapid flux decline among all membranes which was attributed to its irregular and rough surface structure.

Recovery of real dye bath wastewater using integrated membrane process: considering water recovery, membrane fouling and reuse potential of membranes

ABSTRACT It has been recognized by the whole world that textile industry which produce large amounts of wastewater with strong color and toxic organic compounds is a major problematical industry requiring effective treatment solutions. In this study, reverse osmosis (RO) membranes were tested on biologically treated real dye bath wastewater with and without pretreatment by nanofiltration (NF) membrane to recovery. Also membrane fouling and reuse potential of membranes were investigated by multiple filtrations. Obtained results showed that only NF is not suitable to produce enough quality to reuse the wastewater in a textile industry as process water while RO provide successfully enough permeate quality. The results recommend that integrated NF/RO membrane process is able to reduce membrane fouling and allow long-term operation for real dye bath wastewater.

Influences of electroosmosis and electrophoresis on permeate flux and membrane fouling in submerged membrane bioreactors (SMBRs)

The objective of this study was to investigate the influences of electroosmosis (EO) and electrophoresis (EP) on the permeate flux in submerged membrane bioreactors. When a polymeric membrane is placed in between an anode and a cathode, both EO and EP occur simultaneously, causing enhancement in flux. Results showed that after 150 min of filtration, the permeate fluxes were 60, 115, 175 and 260 L/m(2)/h at 0, 30, 40 and 50 V, respectively. It was shown that the EO was linearly changing with increasing voltage, reaching up to 54 L/m(2)/h at 50 V. EP was found to be a significant process in removing soluble microbial products from the membrane surface, resulting in an increase in permeate flux as the filtration progressed. About 20-fold of smaller protein and carbohydrate concentrations were found in the cake layer when the electrical field (EF) was applied. However, the EF application promoted pore fouling, because of the calcium and magnesium scaling.

Membrane integrated process for advanced treatment of high strength Opium Alkaloid wastewaters

In this study, an integrated aerobic membrane bioreactor (MBR)-nanofiltration (NF) system has been applied for advanced treatment of Opium processing wastewaters to comply with strict discharge limits. Aerobic MBR treatment was successfully applied to high strength industrial wastewater. In aerobic MBR treatment, a non-fouling unique slot aeration system was designed using computational fluid dynamics techniques. The MBR was used to separate treated effluent from dispersed and non-settleable biomass. Respirometric modeling using MBR sludge indicated that the biomass exhibited similar kinetic parameters to that of municipal activated sludge systems. Aerobic MBR/NF treatment reduced chemical oxygen demand (COD) from 32,000 down to 2,500 and 130 mg/L, respectively. The MBR system provided complete removal of total inorganic nitrogen; however, nearly 50 mgN/L organic nitrogen remained in the permeate. Post NF treatment after MBR permeate reduced nitrogen below 20 mgN/L, providing nearly total color removal. In addition, a 90% removal in the conductivity parameter was reached with an integrated MBR/NF system. Finally, post NF application to MBR permeate was found not to be practical at higher pH due to low flux (3-4 L/m2/hour) with low recovery rates (30-40%). As the permeate pH lowered to 5.5, 75% of NF recovery was achieved at a flux of 15 L/m2/hour.

Recent developments of electromembrane desalination processes

ABSTRACT Electromembrane processes use the electric potential difference as the driving force to move charged ions through ion-selective membranes. These membranes have negative or positive charged functional groups and can be named as cation- and anion-exchange membranes (CEM and AEM) depending on the sign of the permeating ions. As the electrical force is applied, the membranes allow the permeation of oppositely signed ions and separate the ionic species from an aqueous solution and from other uncharged species. Electromembrane processes are well-established techniques and have gained importance in many areas such as desalination processes, energy production, food processing, molecular separation, water treatment and recovery and membrane concentrate treatment. The desalination with electromembrane process is widely used today for the production of high-quality water from seawater or brackish water. The main electromembrane desalination processes are categorized as electrodialysis (ED), electrodeionization (EDI), capacitive deionization (CDI), reverse electrodialysis (EDR), electrodialysis with bipolar membranes (EDBM). In this review article, the most popular electromembrane desalination processes have been evaluated with their theoretical basis and technological background. The main objectives of the review are (1) to describe the technological background of electromembrane processes (2) to summarize past and present attempts towards scaling up and commercialization of electromembrane desalination process (3) to present a critical review of their advantages and limitations (4) to outline the R&D activities with cost analysis. GRAPHICAL ABSTRACT

A study on near zero liquid discharge approach for the treatment of reverse osmosis membrane concentrate by electrodialysis

ABSTRACT A lab-scale electrodialysis (ED) which consisted of 11 pieces of cation-exchange membranes and 10 pieces of anion-exchange membranes was used to treat concentrated brine of Reverse osmosis (RO) membrane. The effect of operating parameters such as applied voltage, flowrate, and operating mode was investigated to measure the performance of a lab-scale ED. Three different voltages (5, 10, and 15 V) and flowrates (20, 30, and 40 L/h) were applied in order to optimize the operating conditions of the ED system. The maximum TDS removal efficiencies were 85%, 97%, and 98% for 5, 10, and 15 V, respectively. It was concluded that the desalination efficiencies were almost the same at flowrates values of 20, 30 and 40 L/h. The TDS concentration of the treated brine in the concentrate compartment rises to the highest value of 25,400 mg/L with desalination rate of 92.5% after five cycle operation. Moreover, the desalinated brine can be used as fresh water. GRAPHICAL ABSTRACT