Effect of Fe (II) concentration on filter headloss and effluent water quality

Bu çalışmanın amacı sulardaki Fe(II) konsantrasyonunun filtre yük kaybı ve çıkış suyu kalitesine etkisini deneysel olarak incelemektir. Çalışma laboratuvar ölçekli iç çapı 30 mm ve yüksekliği 1000 mm olan pleksiglassdan imal edilmiş silindirik filtre kolonları kullanılarak gerçekleştirilmiştir. Kolonlara 0.50-0.59 mm çapları arasında ve 40 cm yüksekliğinde silisli kum doldurulmuştur. Çalışmada musluk suyu, dört farklı Fe (II) konsantrasyonu (0.5, 1.0, 2.5, 5.0 mg/L) ve iki farklı yükleme hızı (5.6, 11.20 m3/m2.saat) kullanılmıştır. Ham suyun alkalinite değeri, ani pH değişimlerine karşı 150 mg/L CaCO3 değerine ayarlanmıştır. Alkalinite ayarlamasında sodyum karbonat ve pH düşürmede karbondioksit kullanılmıştır. Filtre çıkış suyunda su kalitesini temsilen bulanıklık değeri ve filtrenin demir giderim verimini belirlemek için çıkış suyunda toplam demir(TFe) ölçülmüştür. Filtrede oluşan yük kayıpları ve filtre yatağı boyunca yük kaybı değişimi incelenmiştir. Sonuç olarak,  2.5 ve 5.0 mg/L gibi yüksek TFe konsantrasyonlarında yük kaybının 0.5 ve 1.0 mg/L’ye göre çok daha hızlı meydana geldiği ve tıkanmanın tüm filtre yatağı boyunca değil yoğun bir şekilde filtrenin üst kısmında olduğu, 0.5 ve 1.0 mg/L gibi düşük TFe konsantrasyonlarının yük kaybı oluşumunu çok az etkilediği, filtre çıkışında TFe’nin standart değerinin (0.2 mg/L) altında kalması açısından 2.5 ve 5.0 mg/L TFe konsantrasyonlarında 5.60 m/saat ve daha düşük filtre hızlarının uygulanmasının uygun olacağı belirlenmiştir. Anahtar Kelimeler: Filtrasyon, demir (II) oksidasyonu, yük kaybı,  demir giderimi.The aim of this study is to determine the effect of Fe(II) concentration on filter headloss and effluent water quality. In the scope of the study, a plexiglas cylindrical columns having inner diameter of 30 mm and height of 1000 mm were employed in laboratory scale studies. These filter columns were filled with silica sands having 0.59 mm equivalent diameter, 2.64 g/cm3 density and shape factor of 0.80. It was ensured that the ratio between inner diameter of filter column and diameter of sand was greater than 50. Settling velocity of silica sand was calculated as 8.07 cm/s by column settling experiment results. The porosity of the sand was determined in the experimental study as 0.36. Filter columns were fed by a 100 L-tank. The oxygen required for the oxidation process was provided by a fine bubble diffuser set on the bottom of the tank.  In this study, tap water having 2.5-3.5 mg/L of total organic carbon, 9.5-11 mg/L of dissolved oxygen and temperature of 15-16 0C was used. Alkalinity value of 90-110 mg CaCO3/L of tap water was adjusted to 150 mg CaCO3/L with sodium carbonate (Na2CO3). Increased pH value was decreased to 7.0 injecting carbon dioxide. To ensure Fe(II) concentration, desired ferrous ammonium sulfate (FeSO4(NH4)2SO4.6H2O)  was added to water. Nitric acid ((HNO3)) was used to preserve iron samples for metal analysis.  Perkin Elmer 2100 DV Induced Coupled Plasma Optical Emission (ICP-OES) was used for iron measurement. Cations and anions of tap water were measured by using DIONEX ICS?1500 Ion Chromatograph (IC). Experimental studies were carried out at four different Fe(II) concentrations (0.5, 1.0, 2.5 and 5.0 mg/L) and two different filter velocities (5.60 and 11.20 m/h). Turbidity and total iron concentration were measured at the influent and effluent of the filter. 0.81, 1.2, 7.0 and 15.0 NTU of turbidity in the filter influent were obtained by oxidation of  Fe(II) in the feed tank. Turbidity in the filter effluent for 2.5 mg/L of iron concentration was increased for first 150 minutes and than decreased. It is thought that this was due to longer ripening period of the filter for 2.5 mg/L of iron concentration. On the other hand, it was observed that low filter velocities had to be applied for high iron concentrations and turbidity removal efficiency was not changed importantly in the high filtration velocities in the course of time. Total iron concentrations in the filter effluent were apparently decreased by the increasing filtration period. Although filter headloss was increased linearly at all iron concentrations, it was apparently high for 5.0 mg/L of iron concentration according to other concentrations (0.5, 1.0 and 2.5 mg/L). Headloss changes among filter bed height were investigated and it was noted that headloss curves among filter bed were very different. While headloss curves among filter bed height were parabolic for low filter velocities, they were in the shape of two linear curves at 90 minutes and longer for high filter velocities. While headloss was decreasing to 35 cm deep from top of the filter bed linearly, it was suddenly changed its direction following more step linearly. It was observed that headloss was increased by elevated filter velocities. The results obtained in this study can be summarized as follows: In the case of 0.5 and 1.0 mg/L total iron concentrations and a porosity of 0.36, iron removal can be achieved by rapid sand filters (5-15 m/h) ensuring water quality standards described in TSS-266 (TS-266, 1997) In the higher total iron concentrations such as 2.5 and 5.0 mg/L, headloss occurrence was more rapid than for 0.5 and 1.0 mg/L and clogging happened in top layers of the filter rather than among all the filter height. It was observed that low concentrations of total iron such as 0.5 and 1.0 mg/L did not affect filter headloss occurrence. It was determined that filter velocities lower than 5.60 m/h were more appropriate for 2.5 and 5.0 mg/L total iron concentrations to ensure filter effluent quality and TSS-266 standard. Turbidity removal efficiency was affected by Fe(II) concentration rather than filter velocities. Maximum filter operation time was calculated according to net headloss occurrence rate, filter velocity and raw water iron concentration using experimental results. It was found that the ratio between velocities 11.20 and 5.60 m/s was 0.5 for maximum operating times. Keywords: Filtration, ferrous oxidation, filter headloss, iron removal

Meteorological parameters as an important factor on the energy recovery of landfill gas in landfills

The effect of meteorological factors on the composition and the energy recovery of the landfill gas (LFG) were evaluated in this study. Landfill gas data consisting of methane, carbon dioxide, and oxygen content as well as LFG temperature were collected from April 2009 to March 2010 along with meteorological data. The data set were, first, used to visualize the similarity by using self-organizing maps and to calculate correlation factors. Then, the data was used with ANN to further analyze the impacts of meteorological factors. In both analysis, it is seen that the most important meteorological parameter effective on LFG energy content is soil temperatures. Furthermore, ANN was found to be successful in explaining variations of methane content and temperature of LFG with correlation coefficients of 0.706 and 0.984, respectively. ANN was proved itself to be a useful tool for estimating energy recovery of the landfill gas. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769202

Effect of organic and inorganic matters on the oxidation of Fe(II) in raw water from Omerli Dam

In Turkey, particularly in Istanbul, almost all of the surface and underground water sources contain ferrous iron [Fe(II)] at high concentration levels, which generate serious problems in use of water for industrial processes and at drinking water treatment plants. Ferric iron [Fe(III)] on the other hand precipitates as Fe(OH)(3) and blocks the filters installed at water treatment plants, decreasing efficiency. Also, the period for re-wash of filters shortens which increases the cost. In natural waters, high iron concentrations are found together with natural organic and inorganic substances. Humic substances found in underground water sources prevent the oxidation of Fe(II). It was shown in recent studies that oxidation of Fe(II) was decreased dramatically by organic compounds found in humic substances. Although atmospheric oxidation of Fe(II) is a well known method in practice over decades, effects of organic and inorganic substances on the oxidation rate have only recently been investigated. Literature review showed that the research in the area of effect of organic and inorganic substances over the oxidation of Fe(II) was not satisfactory. Since high concentrations of Fe(II) exist in the surface and underground water and it is critically important for the purpose of drinking and industrial use, it will lead to research and development regarding the methods for treatment of Fe(II). An experimental study was carried out by aeration at constant pH, temperature, alkalinity, and mixing conditions in a laboratory scale batch reactor system, which was fed with raw water obtained from entrance of Omerli Dam Treatment Plant and deionized water. Oxidation was performed for different concentrations of Fe(II). Effects of additional organic and inorganic materials on the oxidation mechanism of Fe(II) were investigated. Potassium hydrogen phthalate (KHP) as organic material and Mn(II), Zn(II), and Ni(II) as inorganic materials were used

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 SO42- 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