Dogan Karadag

Use of magnesit as a magnesium source for ammonium removal from leachate

Using magnesit (MgCO(3)) as a low cost source of magnesium ions in the struvite precipitation for the removal of high ammonium content of leachate was evaluated. Optimum molar concentration and pH conditions were analyzed to minimize the struvite solubility. Since solubility of magnesit in water is low, HCl was used to obtain soluble Mg. Maximum soluble Mg was obtained for the addition of 2 M HCl to the 1 M MgCO(3). Struvite precipitation with magnesit was effective for the removal of ammonium, suspended solid, phosphate and turbidity. Economical evaluation was made comparing the costs of two magnesium sources, MgCl(2) and MgCO(3). The economical analysis has shown that operation cost of struvite precipitation can be reduced about 18% by using MgCO(3) instead of MgCl(2). High salt concentration after struvite precipitation has no inhibitory effect on the anaerobic reactor performance.

Thermophilic biohydrogen production by an anaerobic heat treated-hot spring culture.

Batch experiments were conducted to investigate the thermophilic biohydrogen production using an enrichment culture from a Turkish hot spring. Following the enrichment, the culture was heat treated at 100 degrees C for 10 min to select for spore-forming bacteria. H(2) production was accompanied by production of acetate, butyrate, lactate and ethanol. H(2) production was associated by acetate-butyrate type fermentation while accumulation of lactate and ethanol negatively affected the H(2) yield. H(2) production was highest in the temperature range from 49.6 to 54.8 degrees C and optimum values for initial pH and concentrations of iron, yeast extract and glucose were 6.5, 40 mg/l, 4-13.5 g/l, respectively. PCR-DGGE profiling showed that the heat treated culture consisted of species closely affiliated to genus Thermoanaerobacterium.

The production of electricity from dual-chambered microbial fuel cell fueled by old age leachate

ABSTRACT In this study, electricity production from old age landfill leachate was investigated using dual chambered microbial fuel cell with Ti-TiO2 electrodes. The effect of organic loading rate on microbial fuel cell performance was examined by changing the hydraulic retention time and leachate chemical oxygen demand (COD) concentration. Microbial diversity at different conditions was studied using PCR-DGGE profiling of 16 sRNA fragments of microorganisms in the liquid media of the anode chamber and of the biofilm on the anode electrode. Both COD removal and current density were positively affected with increasing organic loading rate. The highest microbial fuel cell performance was achieved at hydraulic retention time of 0.5 day and organic loading rate of 10 g COD/L.day. The performance of the microbial fuel cell reactor decreased when hydraulic retention time was reduced to 0.25 day. The investigation of the microbial dynamics indicated that abundance of bacterial species was considerably dependent on the operational conditions. The microbial fuel cell reactor was mainly dominated by Geobacter, Shewanella, and Clostridium species, and some bacteria were easily washed out at lower hydraulic retention times.

Anaerobic treatment of ozonated membrane concentrate

AbstractA concentrate stream is generated by the application of nanofiltration (NF) membranes in wastewater reuse. Due to the high concentrations of pollutants, disposal of NF concentrates is an important problem. In this study, ozonation and anaerobic treatment processes were performed to treat cotton dyeing textile mill wastewater NF concentrate. After ozonation, the concentration of biochemical oxygen demand (BOD5) increased while dissolved chemical oxygen demand (DCOD) decreased. Thus, biodegradability of the concentrate was increased by the ozonation process. The average removal efficiencies of DCOD, BOD5, and sulfate () in the anaerobic process were achieved about 72, 76, and 68%, respectively. These results indicated that the combination of ozonation and anaerobic treatment showed a remarkable performance for the removal of pollutants from NF concentrate.

Adsorption of Different Reactive Dyes onto Surfactant-Modified Zeolite: Kinetic and Equilibrium Modeling

This study deals with the kinetic and equilibrium modeling of adsorption of the commercially important reactive azo dyes, Black B (C.I. Reactive Black 5), Red 3BS (C.I. Reactive Red 239) and Yellow 3RS H/C (C.I. Reactive Yellow 176) onto a Turkish zeolite mineral. To increase the adsorption capacity of the zeolite, the surface of natural samples was modified with a typical quaternary amine surfactant hexadecyltrimethylammonium bromide (HTAB). A series of batch adsorption tests were carried out at 298 K and the pseudo-first–order, pseudo-second-order kinetic models and intraparticle diffusion model were used to evaluate the kinetic data. The pseudo-second-order model provided excellent kinetic data fitting (R 2 > 0.997) for these three dyes. The free energy changes ΔG for dye adsorption onto HTAB-zeolite were calculated. The negative values of ΔG indicate that the adsorption process is spontaneous and thermodynamically favorable. The Freundlich and Langmuir equations were also applied to describe the equilibrium isotherms for three reactive dyes and isotherm constants were determined. The Langmuir model agrees very well with experimental data while the adsorption behavior of all reactive dyes is favorable (0< R L < 1).

Post-treatment of anaerobically-treated compost leachate by membrane systems: emphasis on molecular weight distribution

Compost leachate contains high concentrations of organic matter, sulphate and ammonia which requires combined treatment systems. In case of the use of membrane containing combined systems, the effect of pretreatment on molecular weight distribution (MWD) is important in terms of appropriate membrane selection. In this study the leachate from Istanbul full-scale composting plant was firstly treated in an anaerobic fluidized bed reactor (AFBR). Performance of the reactor was low due to the inhibiton by high ammonia content while treatment efficiencies of COD and SO4 2– were around 41% with 50% ammonia removal. During the anaerobic treatment high molecular weight materials were mostly converted to low molecular fractions. However, changes in the distribution of molecular fractions differed in each pollutant parameters. Subsequent membrane treatment scheme was determined according to the molecular weight distribution analyses. Particular and collodial materials from AFBR effluent was effectively treated by MF and UF membranes. Post-treatment studies were performed using four different NF and RO membranes and performance comparison was made based on removal efficiency and flux changes. BW30 membrane provided the lowest treatment efficiency while other TXN45, NF90 and XLE membranes had similar effluent quality. Effluent from all membrane systems met discharge limits and optimum treatment scheme has been suggested as AFBR+MF+UF+TXN45 based on operational flux values.