Ayşegül Pala

Color removal from cotton textile industry wastewater in an activated sludge system with various additives

The low biodegradability of many dyes and textile chemicals indicates that biological treatment is not always successful in the treatment of cotton textile wastewater, in terms of color removal. In this study, a specific organic flocculant (Marwichem DEC), powdered activated carbon (PAC), bentonite, activated clay and commercial synthetic inorganic clay (Macrosorb) were directly added into the activated sludge laboratory pilot plant model. Before dosage, the optimum sludge retention time and hydraulic retention time were determined as 30 days and 1.6 days, respectively. The Monod kinetic constants were determined as Y = 0.76 kg MLSS/kg COD, Kd = 0.026 l/day, K(S) = 113.3 mg/L, k = 0.42 l/day and mu(max) = 0.32 kg MLSS/kg COD day. Under these conditions the average COD removal was 94% and color removal was 36%. The addition of these materials did not change COD removal significantly. The most effective materials were found to be DEC and PAC for color removal. While the color removal efficiency for 120 mg/L DEC addition was 78%, it was 65% for 100 mg/L, 77% for 200 mg/L and 86% for 400 mg/L PAC addition. The advantage of DEC compared to PAC was the lower sludge production. Statistical analyses using multiple linear regression indicate that there is no relationship between the effluent color with the influent color and total suspended solids (TSS) for DEC and PAC addition. On the other hand, when only bentonite, activated clay and Macrosorb were added, the effluent color was primarily dependent on the influent color and the TSS concentration had little effect. When the data is examined by using Kruskal-Wallis H and Mann-Whitney U tests and it was found that there was a significant difference between the color data groups.

Determination of arsenic removal efficiency by ferric ions using response surface methodology

Arsenic contamination of drinking water is a serious problem in many parts of the world. The precipitation/coprecipitation method was used for arsenic removal from drinking water by ferric chloride, ferric sulfate and ferrous sulfate as coagulant. A Box-Behnken statistical experiment design method was used to investigate the effects of major operating variables such as initial arsenate concentration (10-1000 microg L(-1)), coagulant dose (0.5-60 mg L(-1)) and pH (4-9) were investigated. Experimental data were used for determination of the response functions coefficients. Predicted values of arsenate removal obtained using the response functions were in good agreement with the experimental data. Fe(III) ions were more effective and economic than Fe(II) ion due to required lower coagulant dose and pH. In the low initial arsenate concentrations, the highest arsenate removal efficiency was required high ferric chloride and ferric sulfate dose of 50 and 40 mg L(-1), while in the high initial arsenate concentrations, the highest arsenate removal efficiency was provided at low ferric chloride and ferric sulfate dose of 37 and 32 mg L(-1), respectively. This study showed that Box-Behnken design and response surface methodology was reliable and effective in determining the optimum conditions for arsenic removal by coagulation and flocculation.

Importance of particulate biodegradable organic compounds in performance of full-scale biological phosphorus removal system.

In this study, biological treatment performances of two parallel treatment lines operating with and without primary sedimentation were investigated. The research was carried out in a large-scale enhanced biological phosphorus removal (EBPR) process. Influent and effluent of treatment lines were characterized continuously during the study. In addition, anaerobic anoxic and aerobic EBPR activities were investigated by batch tests using fresh activated sludge samples. All of the environmental and operational conditions of the treatment lines were statistically compared. Evaluation of effluent compositions indicated that EBPR performances of treatment lines were significantly different. Results of the research also indicated that settling characteristics of the activated sludge process could be improved significantly with increasing particulate biodegradable organic compound (pbCOD) loading rate. Batch test results revealed that anaerobic, anoxic, and aerobic biochemical reaction rates of activated sludge cultivated on increased pbCOD loading rate were significantly higher compared to activated sludge cultivated on soluble substrate forms.

Arsenic removal from drinking water by electrocoagulation using iron electrodes

Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm−2), initial arsenic concentration (50–500 μg L−1), operating time (0–15 min), electrode surface area (266–665 cm2), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L−1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm−2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm2 taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L−1 for electrode surface area of 266 cm2. The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.

The Effect of Benzene, Toluene, and o-Xylene on COD Removal in an Aerobic Fluidized Bed Reactor Utilizing Acetic Acid as the Main Carbon Source

A laboratory-scale fluidized bed reactor (FBR) model was operated to examine the effect of BTX on the removal of COD in the presence of acetic acid, which was readily degradable. An activated sludge culture was taken from a petrochemical industry wastewater treatment plant and acclimated first to acetic acid (up to 2,000 mg COD/L), and then to BTX (up to 3 mg/L) as a total concentration. Microbial oxygen uptake rates are controlled during the adaptation period. Then this culture is used as inoculum in the FBR unit. The system was initially operated with a total BTX concentration of 6 mg/L, and concentrations of 12 and 18 mg/L, respectively, were tried during an operational period of 42 days, while the theoretically estimated COD concentration (due to the acetic acid in the system) was kept constant, remaining at 2,000 ± 75 mg/L. An organic loading rate of 1.3 kg/m3/day and a hydraulic retention time of 36 h are the fixed operating parameters used during this study. It was seen that the dissolved COD conce...

The COD Removal Performance of an Aerobic Fluidized Bed Reactor

Aerobic fluidized bed reactors (FBRs) are used as a new technology in wastewater treatment. In this study, an aerobic fluidized bed reactor with granulated activated carbon (GAC) as carrier material was operated under different conditions, including batch-loading, semicontinuous loading, and continuous loading. The FBR effluent was studied for changes in Chemical Oxygen Demand (COD). In this study, acetic acid was used as a carbon source. During the course of the study while the FBR was operating continuously initial COD influent concentration of the acetic acid was 1,000 ± 100 mg/L. Additional continuous flow investigations were conducted with the influent COD at 2000, 3,000 and 4,350 ± 125 mg/L. The total operation period was 5 months including a 1-month start-up process. Organic loading rate increased from 1.0 kg/day/m3 to 14.4 kg/day/m3. This was achieved by changing the influent water COD concentration and/or the hydraulic loading rate. The average effluent dissolved COD concentration was 141 ± 38 mg...

Nutrient Cycling and Coastal Pollution in İzmir Bay, Turkey

Description of Izmir City and Izmir Bay Izmir is the second most important industrial and commercial center of Turkey. The city and its surrounding catchment has a surface area of 12825 km2. Besides industrial activities the city also has agricultural and tourism activities. The increase of population, concentration of industry and rapid development created extensive urbanisation which has significantly disturbed the natural balance of its environment.