Halil Hasar

ADSORPTION OF NICKEL (II) FROM AQUEOUS SOLUTION ONTO ACTIVATED CARBON PREPARED FROM ALMOND HUSK

Activated carbon was prepared from almond husk by activating without (MAC-I) and with (MAC-II) H(2)SO(4) at different temperatures. The ability of the activated carbon to remove nickel(II) ions from aqueous solutions by adsorption has been investigated under several conditions such as pH, carbonisation temperature of husk, initial concentration of metal ions, contact time, and adsorbent concentration. Optimal conditions were pH 5.0, the carbonisation temperature of 700 degrees C, 50 min of contact time and adsorbent concentration of 5 g/l. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon, prepared from almond husk at 700 degrees C, through the addition of H(2)SO(4). The removal of Ni(II) were found to be 97.8% at initial concentration of 25mg/l and the adsorbent concentration of 5 g/l. When the adsorbent concentration was increased up to 40 g/l, the adsorption density decreased from 4.89 to 0.616 mg/g for MAC-II. In the isotherm studies, the experimental adsorption data fitted reasonably well the Langmuir isotherm for both MAC-I and MAC-II.

Stripping/flocculation/membrane bioreactor/reverse osmosis treatment of municipal landfill leachate

This study presents a configuration for the complete treatment of landfill leachate with high organic and ammonium concentrations. Ammonia stripping is performed to overcome the ammonia toxicity to aerobic microorganisms. By coagulation-flocculation process, COD and suspended solids (SS) were removed 36 and 46%, respectively. After pretreatment, an aerobic/anoxic membrane bioreactor (Aer/An MBR) accomplished the COD and total inorganic nitrogen (total-N(i)) removals above 90 and 92%, respectively, at SRT of 30 days. Concentrations of COD and total-N(i) (not considering organic nitrogen) in the Aer/An MBR effluent decreased to 450 and 40 mg/l, respectively, by significant organic oxidation and nitrification/denitrification processes. As an advanced treatment for the leachate, the reverse osmosis (RO) was applied to the collected Aer/An MBR effluents. Reverse osmosis provided high quality effluent by reducing the effluent COD from MBR to less than 4.0mg/l at SRT of 30 days.

Role of intermittent aeration in domestic wastewater treatment by submerged membrane activated sludge system

Abstract In this study, the treatment of domestic wastewater in a lab-scale submerged membrane activated sludge system (sMBR) was investigated under different aeration intervals. The COD concentration of the system effluent varied generally between 5 and 25 mg/l and the COD removal at the organic loads of 0.6–0.8 kg COD/m3.d was observed to be above 98%. The total phosphorus content of the filtrate was decreased to a level that was less than 1 mg/l under the aerobic conditions in which the aeration was continuously made. A dramatic increase in the total phosphorus content of filtrate was observed under the aerobic + anoxic conditions in which the aeration was made at differential intervals. The filtrate was free of suspended solid (SS) and total coliform bacteria and a percent removal of 100 was achieved in terms of these parameters. The influent turbidity removal was 97–99.8%. Generally, the removal of total Kjeldahl nitrogen (TKN) and ammonium nitrogen varied in the ranges of 87.8–99.1% and in the ranges of 89.4–99.8%, respectively. While the nitrate concentrations in the filtrate increased to 26.8 mg/l under the aerobic conditions, it was determined that this value was decreased to 2.4 mg/l under the aerobic + anoxic conditions.

Performance of a sulfide-oxidizing, sulfur-producing membrane biofilm reactor treating sulfide-containing bioreactor effluent.

Sulfide-containing waste streams are generated in mining, petrochemical plants, tanneries, viscose rayon manufacture, and the gasification of coal. Colorless sulfur bacteria can oxidize sulfide to elemental sulfur (S°), which can be recovered, when oxygen is their electron acceptor. This study evaluated sulfide oxidation and S° recovery in an oxygen-based membrane biofilm reactor (MBfR) treating the effluent from a sulfidogenic anaerobic baffled reactor. Sulfide oxidation efficiency (37-99%) and S° recovery (64-89% of oxidized sulfide) could be controlled by manipulating the sulfide loading, oxygen pressure to the fibers, and hydraulic retention time (HRT). For example, too-low oxygen pressure decreased S° recovery due to decreased sulfide oxidation, but too-high oxygen pressure lowered S° recovery due to its oxidation to sulfate. Most importantly, high sulfide oxidation (>98%) and conversion to S° (>75%) could be achieved together when the sulfide loading was less than 1.7 mol/m²·d and the O₂ pressure was sufficient to give an O₂ flux of at least 1.5 mol/m²·d. However, higher sulfide loading could be compensated by a higher O₂ pressure, and the best performance occurred when the sulfide loading was high (2 molS/m²·d), the O₂ pressure was high (∼1 atm), and the HRT was short (1.9 h). Membrane fouling caused a low O₂ flux, which led to low sulfide-oxidation efficiency, but fouling could be reversed by mild acid washing.

Effect of anions on removing Cu2+, Mn2+ and Zn2+ in electrocoagulation process using aluminum electrodes

In the present study, the performance of electrocoagulation process with aluminum electrodes in the treatment of Cu(2+), Zn(2+) and Mn(2+) containing aqueous solutions was investigated by depending on type of anion in solution, considering some operating conditions such as initial metal concentration and pH. Results obtained from synthetic wastewater showed that type of anion in solutions has a significant effect on the metal removal. The initial concentration of zinc influenced significantly the performance of electrocoagulation process as compared with the results obtained from Mn and Cu metals. Anions studied did not generate an important difference between pH variations. Best removals for three metals were achieved with increasing the pH in the presence of both anions. Total removals of copper and zinc reached almost 100% after 5 min at pH values > 7. At the end of the experiments for 35 min, the Mn removals were 85 and 80% in the presence of sulfate and chloride anions, respectively.

Viability of microbial mass in a submerged membrane bioreactor

In this study the viability of biomass in a submerged membrane activated sludge system (sMBR) which treats domestic wastewater was investigated by dealing with non-biodegradable COD, specific oxygen uptake rate and MLVSS during operation for 100 days. It was shown that the viability of biomass in the bioreactor was reduced at the 50% level because of the accumulation of inert compounds and the reduction in the activities of poor biomass. After inoculating the bioreactor again, the specific OUR increased because of young biomass entering into the bioreactor. It was shown that there was an exponential relationship between OUR and MLVSS and there was a logarithmic relationship between specific OUR and MLVSS.

Evaluation for Agricultural Usage with Speciation of Heavy Metals in a Municipal Sewage Sludge

This study was carried out to evaluate the agricultural usage of an anaerobically digested sludge in the contents and fractions of heavy metals. Therefore, a sequential extraction scheme according to the BCR’s (Community Bureau of Reference) guidelines and total acid digestion were applied to sewage sludge samples. The results of total heavy metal concentrations in sewage sludge showed that the highest total concentrations were Fe, Zn and Mn. When Turkish, Europe and US EPA directives were compared with each other by depending on the use of sludge for agricultural purposes, all the heavy metals determined for this sludge were below the maximum permitted levels, except for Cd. This sludge should not be applied to land due to its high Cd content. The results of heavy metal fractions indicated that some metals (Cd, Mn, Pb, and Fe) distributed mainly in the residual fraction. All fractions of Zn showed no variation. Cu and Cr were most abundant in the oxidizable phase while Ni was in exchangeable phase. Although total content of Ni in the sludge is lower than the maximum levels allowed by all the directives, it tends to be easily moved and dispersed in the environment. Due to its high mobility, the examined sewage sludge may cause phyto-toxicity after its agricultural application.

Effect of EDTA as washing solution on removing of heavy metals from sewage sludge by electrokinetic

This paper presents the effect of ethylene diamine tetraacetic acid (EDTA) as a washing solution on the electrokinetic process for removal of Cr, Pb and Zn from sewage sludge. The sequential chemical extraction scheme according to the guidelines of BCR (Community Bureau of Reference) was applied to the sludge samples to evaluate the effect of EDTA on metal fractionation during electrokinetic processes. The highest removals of the heavy metals were 34% for Cr, 27% for Pb and 20% for Zn with 0.1N EDTA. The removal priority of the metals by electrokinetic process was found to be Cr>Pb>Zn. According to the results of BCR analysis, addition of EDTA did not create the inter-transformation of Cr, Pb and Zn although the metal concentration decreased.

Simultaneous removal of organic matter and nitrogen compounds by combining a membrane bioreactor and a membrane biofilm reactor.

Hydrogen-based membrane biofilm reactors (MBfR) have been applied to the denitrification of nitrate-containing water and wastewater. Adding an aerobic membrane bioreactor (MBR) to a MBfR provides significant nitrification and organic oxidation because most wastewater also contains a significant concentration of organic material and ammonium nitrogen. This study describes experiments that investigate the removal of organic and nitrogenous compounds in the combined MBR/MBfR system. The experiments demonstrate that the MBR/MBfR combination successfully performs COD oxidation and nitrogen removal for organic and ammonium loads in the ranges of 1000-4300gCOD/m(3)-d and 200-230gN/m(3)-d, respectively. Total-nitrogen removal was controlled by nitrification in the MBR, because the MBfR denitrified all of the NO(3)(-) provided by the MBR. The nitrate flux in the MBfR was in the range of 4-8gN/m(2)-d for cases of almost complete denitrification (>99 %); the H(2) flux was varied from 1.4 to 2.8gH(2)/m(2)-d.

Removal of Zinc(II) by Activated Carbon Prepared from Almond Husks under Different Conditions

Activated carbon was prepared from almond husks by activation at different temperatures in the absence (MAC-I) and presence (MAC-II) of H2SO4. The ability of the activated carbon to remove zinc(II) ions by adsorption from aqueous solutions was investigated, varying several conditions such as pH, the carbonisation temperature of the husk, the initial concentration of metal ions, the contact time and the adsorbent concentration. The optimum conditions were found to be a pH value of 5.5, a carbonisation temperature of 700°C, a contact time of 60 min and an adsorbent concentration of 4 g/l. The results obtained indicated that effective uptake of Zn(II) ions was achieved when the carbon prepared by heating almond husks at 700°C was activated by the addition of H2SO4. A 92% removal of Zn(II) ions was achieved at an initial concentration of 20 mg/l and an adsorbent concentration of 4 g/l. When the adsorbent concentration was increased to 40 g/l, the adsorption density decreased from 4.5 mg/g to 0.47 mg/g for MAC-II. The Langmuir and Freundlich constants were both calculated, and the data found to be fitted reasonably well by the Langmuir isotherm. The adsorption capacities for MAC-I and MAC-II as calculated from the Langmuir isotherm were 30.864 mg/g and 35.336 mg/g, respectively.