Gizem Karaca

Removal of polycyclic aromatic hydrocarbons from municipal sludge using UV light

Abstract This study includes research into using UV light to remove Polycyclic Aromatic Hydrocarbons (PAHs) from municipal sludge. The effectiveness of TiO2 as a photocatalyst on this UV application was also determined. Sludge samples that were taken from an urban wastewater treatment plant (UWWTP) were exposed to UV-C light in a specially designed setup. The total concentration of Σ12 PAH in the sludge, which was 1339 ng g−1 of dry matter initially, decreased by 2–77% after 24 h of UV application. The concentrations of some PAH isomers increased after the UV application, which revealed that isomer transformations could emerge due to the effects of temperature and photodegradation. UV light was found to remove 3-ring light compounds more effectively than 4–6-ring heavy compounds. A total PAH decrease of 77% was achieved by adding an amount of TiO2 equal to 0.5% of the dry weight of the sludge although the removal rate of PAHs from the sludge decreased when the TiO2 dosage was increased. It is possible tha...

Removal of polycyclic aromatic hydrocarbons (PAHs) from industrial sludges in the ambient air conditions: Automotive Industry

Removal of polycyclic aromatic hydrocarbons (PAHs) existed in automotive industry treatment sludge was examined by considering the effects of temperature, UV, titanium dioxide (TiO2) and diethyl amine (DEA) in different dosages (i.e., 5% and 20%) in this study. Application of TiO2 and DEA to the sludge samples in ambient environment was studied. Ten PAH (Σ10 PAH) compounds were targeted and their average value in the sludge was found to be 4480 ± 1450 ng/g dry matter (DM). Total PAH content of the sludge was reduced by 25% in the ambient air environment. Meteorological conditions, atmospheric deposition, evaporation and sunlight irradiation played an effective role in the variations in PAH levels during the tests carried out in ambient air environment. Moreover, it was observed that when the ring numbers of PAHs increased, their removal rates also increased. Total PAH level did not change with the addition of 5% DEA and only 10% decreased with 5% TiO2 addition. PAH removal ratios were 8% and 32% when DEA (20%) and TiO2 (20%) were added, respectively. It was concluded that DEA was a weak photo-sensitizer yet TiO2 was effective only at 20% dosage.

Effects of Temperature and Photocatalysts on Removal of Polycyclic Aromatic Hydrocarbons (PAHs) from Automotive Industry Sludge

This study was carried out to investigate the removability of polycyclic aromatic hydrocarbon (PAH) compounds existed in automotive industry treatment sludge. The impacts of temperature, UV, titanium dioxide (TiO2), and diethyl amine (DEA) were studied in a controlled device which was specifically designed for this study. Sludge samples were collected from the treatment plant of an automotive manufacturing facility in Bursa, Turkey. The ∑10 PAH concentration value in the sludge was 4480 ± 1450 ng/g dry matter (DM). ∑10 PAH removal ratio was 30% at 37°C without UV irradiation. Moreover, the PAH content in the sludge was reduced up to 65% through applying UV irradiation. This figure reached 100% by using photo-catalysts (TiO2 or DEA) at the rate of 20% of the DM of the sludge.

Migration of PAHs in food industry sludge to the air during removal by UV and TiO2

This study was conducted to investigate the evaporation ratios of polycyclic aromatic hydrocarbons (PAHs) from the food industry treatment sludge. Five PAH compounds having different ring numbers were targeted. The effects of temperature, UV and TiO2 on PAH evaporation were also studied. All applications were performed in a specially designed apparatus. The air in the apparatus was vacuumed to collect the evaporated PAHs on the PUF cartridges. Then, these PUF cartridges were extracted for determination of PAHs. The PAH concentrations were measured by a gas-chromatography mass-spectrometer (GC-MS). 91% of the initial ∑5 PAHs in the sludge was evaporated into the air at the end of the UV application. However, this value decreased to 21% when UV was not employed. Initial and final PAH levels in the sludge were measured to determine the removed PAHs which refer to the addition of degraded and evaporated PAHs. The results indicated that the UV-TiO2 application at high temperatures was considered an appropriate PAH removal method because it restricted the evaporation of PAHs while it removed high levels of PAHs. PAHs were mainly removed from the sludge by degradation rather than evaporation with this application.

Temporal and spatial variations in PAH concentrations in the sediment from the Nilufer Creek in Bursa, Turkey

The objective of this study was to identify the temporal variations in PAH concentrations in the sediment at different locations on the Nilufer Creek moving along an industrial city. The distribution of various PAH species and their possible sources were determined. Sediment samples were taken from at eight different locations on the Nilufer Creek for a one‐year period. Temporal concentration profiles were in the range of 15–9600 ng g−1 dry matter (dm). PAH concentrations reached their maximum values in the winter (9600 ng g−1 dm). Molecular diagnostic ratios of PAHs showed that the pollution in the Nilufer Creek in the fall, winter and summer seasons was mostly pyrolytic. It was observed that 3–4 ring species predominated in all seasons in the Nilufer Creek sediment.

Stabilization and solidification of waste phosphate sludge using Portland cement and fly ash as cement substitute

Stabilization and solidification of the waste phosphate sludge (WPS) using Portland cement (PC) and fly ash (FA) were studied in the present work. The WPS content in the cement mortars varied from 5% to 15%. Setting times were measured, and unconfined compressive strengths (UCS) were determined for the mortars cured in water for 3, 7, 28, 56, and 90 days. Zinc and nickel leaching of the solidified products were measured according to the Toxicity Characteristic Leaching Procedure. Setting times were extended as the WPS content in the paste samples increased. The UCS values of the mortar containing 5% WPS solidified by using 95% PC were similar to the reference sample. Use of 10% FA as cement substitute increased the UCS values by 10% at the end of curing period of 56 days. The WPS contained initially 130.2 mg L− 1 of zinc and 22.7 mg L− 1 of nickel. The zinc and nickel leached from the 5% WPS solidified by using 95% PC were measured as 3.8 mg L− 1 and 0.4 mg L− 1, respectively. These metal concentrations were below the limits given by the U.S. Environmental Protection Agency for landfilling the solidified wastes.

Application of various methods for removal of polycyclic aromatic hydrocarbons from synthetic solid matrices

In the present study, removal of polycyclic aromatic hydrocarbons (PAHs) from synthetic solid matrices with various methods was investigated. PAH removal experiments were conducted in a specifically designed UV apparatus for this study. Polyurethane foams (PUF) cartridges were used to remove PAHs from the incoming air and to capture PAHs from the evaporated gases. Sodium sulphate (Na2SO4) was used as a synthetic solid matrices. The effects of temperature, UV radiation, titanium dioxide (TiO2) and diethylamine (DEA) dose on the PAH removal were determined. TiO2and DEA were added to the Na2SO4 sample at the rate of 5% and 20% of dry weight of samples. PAHs’ removal from the Na2SO4 enhanced with increasing temperature. ∑12 PAH content in the Na2SO4 reduced up to 95% during UV light application. Moreover, the ∑12 PAH removal ratio was calculated as 95% with using 5% of TiO2, and increasing of TiO2 dose negatively affected PAH removal. PAH concentration in the samples decreased by 93% and 99% with addition of 5% and 20% DEA, respectively. Especially, 3- and 4-ring PAH compounds evaporated during the PAH removal applications. As expected, evaporation mechanism became more effective at high temperature for light PAH compounds. It was concluded that PAHs can successfully be removed from synthetic solid matrices such as Na2SO4 with the applications of UV light and UV-photocatalysts.