Cagatayhan B. Ersu

Heavy metal content and distribution in surface sediments of the Seyhan River, Turkey

Chemical fractionation of seven heavy metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) was studied using a modified three-step sequential procedure to assess their impacts in the sediments of the Seyhan River, Turkey. Samples were collected from six representative stations in two campaigns in October 2009 and June 2010, which correspond to the wet and dry seasons, respectively. The total metal concentrations in the sediments demonstrated different distribution patterns at the various stations. Cadmium was the only metal that was below detection at all stations during both sampling periods. Metal fractionation showed that, except for Mn and Pb, the majority of metals were found in the residual fraction regardless of sampling time, indicating that these metals were strongly bound to the sediments. The potential mobility of the metals (non-residual fractions) is reflected in the following ranking: Pb > Mn > Zn > Cu > Ni > Cr in October 2009 and Mn > Pb > Zn > Cu > Ni > Cr in June 2010. The second highest proportion of metals was bound to organic matter/sulfides, originating primarily from anthropogenic activities. Non-residual metal fractions for all stations were highest in June 2010, which may be linked to higher organic matter concentrations in the sediment samples with 1.40% and 15.1% in October 2009 and June 2010, respectively. Potential sediment toxicity was evaluated using the Risk Assessment Code (RAC). Based on RAC classification, Cd and Cr pose no risk, Cu and Ni pose low risk, Pb and Zn were classified as medium risk metals, while the environmental risk from Mn was high. In addition, based on the sediment quality guidelines (SQG), the Seyhan River can be classified as a river with no, to moderate, toxicological risks, based on total metal concentrations.

Impact of solids residence time on biological nutrient removal performance of membrane bioreactor.

Impact of long solids residence times (SRTs) on nutrient removal was investigated using a submerged plate-frame membrane bioreactor with anaerobic and anoxic tanks. The system was operated at 10, 25, 50 and 75 days SRTs with hydraulic retention times (HRTs) of 2 h each for the anaerobic and anoxic tanks and 8 h for the oxic tank. Recirculation of oxic tank mixed liquor into the anaerobic tank and permeate into the anoxic tank were fixed at 100% each of the influent flow. For all SRTs, percent removals of soluble chemical oxygen demand were more than 93% and nitrification was more than 98.5% but total nitrogen percent removal seemed to peak at 81% at 50 days SRT while total phosphorus (TP) percent removal showed a deterioration from approximately 80% at 50 days SRT to 60% at 75 days SRT. Before calibrating the Biowin((R)) model to the experimental data, a sensitivity analysis of the model was conducted which indicated that heterotrophic anoxic yield, anaerobic hydrolysis factors of heterotrophs, heterotrophic hydrolysis, oxic endogenous decay rate for heterotrophs and oxic endogenous decay rate of PAOs had the most impact on predicted effluent TP concentration. The final values of kinetic parameters obtained in the calibration seemed to imply that nitrogen and phosphorus removal increased with SRT due to an increase in anoxic and anaerobic hydrolysis factors up to 50 days SRT but beyond that removal of phosphorus deteriorated due to high oxic endogenous decay rates. This indirectly imply that the decrease in phosphorus removal at 75 days SRT may be due to an increase in lysis of microbial cells at high SRTs along with the low food/microorganisms ratio as a result of high suspended solids in the oxic tank. Several polynomial correlations relating the various calibrated kinetic parameters with SRTs were derived. The Biowin((R)) model and the kinetic parameters predicted by the polynomial correlations were verified and found to predict well the effluent water quality of the MBR at 35 days SRT.

Ultrafiltration of ink and latex wastewaters using cellulose membranes

Ultrafiltration (UF) studies were conducted on latex and ink rinse wastewaters to assess the potential of concentrating the wastewater and recovering the permeate for reuse and recycling purposes. The physicochemical characteristics of the ink and latex wastewater suggested that the quality of both wastewaters was strongly dependent on the rinse process. A 4-fold and 7-fold concentration of ink and latex wastewater, respectively, may be achieved depending on the initial physicochemical characteristics of the wastewater. The UF system concentrated the latex wastewater to a total solids (TS) concentration of 275 g/L (approx. 28%) and to 99 g/L (approx. 10%) for ink wastewater. The permeates had turbidities ranging from 0.13 to 0.4 NTU. However, a significant percentage of the TS remained in the permeate of the ink wastewater which may require further treatment before it can be reused. For latex wastewater, it is likely that the retentate can be reused along with the permeate for rinsing purposes. For the ink wastewater, both pore blocking and cake resistance models were able to describe the change in flux with time. However, for the latex wastewater, pore blocking seemed to describe the flux with time data better than the cake resistance models. The fouling coefficient, K, for the pore blocking model was found to be a function of the TS present in the latex wastewater.

Environmental implications of a hydrogeochemical survey for drinking water in Kirsehir region

A hydrogeochemical survey of springs was carried out in Kirsehir, Turkey and fluoride, heavy metals, and mineral contents were analyzed. The highest fluoride levels were detected in Mahmutlu with 2.1 ppm. The fluoride content of Pohrenk was, on average, 1.1 ppm. Consequently, dental fluorosis and dental stains were observed in both villages. Although the fluoride concentrations were within the suggested limits, dental stains and fluorosis were commonly observed among the villagers especially kids. The fluoride concentrations of 0.7–1.0 ppm were the lowest in Cevirme, which is to the northwest of fluoride ore. The heavy metal concentrations of resources around the three villages were compared with and were found lower than WHO’s provisional guideline values. However, the Fe, Zn, and Cr concentrations in hot springs were much higher than cold springs with as much as 100 ppb for Fe, 50 ppb for Zn, and 15 ppb for Cr.

Removal of Basic Textile Dyes from Aqueous Solutions through Adsorption by Eucalyptus camaldulensis Barks

In this study, the adsorption capacities of Eucalyptus camaldulensis barks were investigated as an alternative tertiary treatment for the removal of textile dyes [Basic Blue (BB41) and Basic Yellow (BY51)] commonly used in the textile industry. The first set of experiments employed an initial dye concentration of 100 mg/ℓ and 3 g of tree barks in order to determine the contact time for breakthrough. Then, the adsorption isotherm constants were obtained for BB41 and BY51 employing concentrations varying between 25 mg/ℓ to 800 mg/ℓ and between 25 mg/ℓ to 500 mg/ℓ, respectively, using the same amount of E. camaldulensis barks. The constants determined via the Langmuir and Freundlich isotherms indicated that both isotherm models were adequate for explaining the adsorption process. According to the Langmuir isotherm, the maximum adsorption capacities (Qmax) of the E. camaldulensis barks for BB41 and BY51 were 164.17 mg/g and 54.68 mg/g, respectively. The applicability of various kinetic models was also investigated. The results indicated that the adsorption kinetics conformed to intra-particle diffusion. Finally, the dimensionless constant separation factor for the adsorbent/adsorbate system was determined.

Extended Aeration Activated Sludge Reactor (EAASR) for Removal of Nitrobenzene: Air Stripped or Biologically Removed?

Abstract In this study, the performance of an extended aeration activated sludge reactor (EAASR) was investigated for the removal of nitrobenzene (NB), a commonly used organic chemical in various industries. In a set of experiments, increasing NB concentrations between 1 and 800 mg/L were applied to the EAASR. Synthetic wastewater containing NB was successfully treated up to 92.0 and 100.0% in terms of chemical oxygen demand (COD) and NB removal. The major NB removal mechanism in this EAASR was assessed to be air stripping after kinetic evaluation as compared to somewhat limited bacterial degradation of NB. Although NB is known to be toxic, the removal efficiency of NB was never below 97.4% even at high NB concentrations. Under lower NB concentrations, it was found that the bacterial floc formation was intact with existing Ciliata and Rotifera. However, at higher NB concentrations, free swimming Ciliata and Rotifera specimens disappeared while the flocs became smaller and dispersed.