Easily available organic substrates (e.g., peanut, walnut and almond shells and luffa sponge) were evaluated as potential filter material for permeable biobarrier systems. Higher removal efficiencies and rate constants were observed for lower (20%) substrate (e.g., peanut, walnut and luffa sponge) percentages indicating to the importance of substrate percentage. Rate constants were higher for total inorganic nitrogen removal (≥0.137 mg N/L/d) than for nitrate removal (≥0.127 mg N/L/d) in the batch bioreactors promising the capability of microorganisms in consuming substrate released nitrogen compounds. Continuous flow biobarriers revealed greater removal efficiencies (<1 mg NO3−–N/L) and rate constants (≥2.38 mg NO3−–N/L/d) that were related to better microbial performance with increased substrate contact. Different dissolved oxygen levels observed for peanut shell (≤7.45 mg O2/L) and luffa sponge columns (<3 mg O2/L) were indicating to the existence of different mechanisms and microorganisms during simultaneous heterotrophic nitrification and aerobic or anoxic denitrification. Luffa sponge was found to be the best candidate as a biobarrier substrate for a longer timescale, although walnut and almond shells may be excellent materials both supporting the denitrification process and permeability of barrier system.

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In order to increase the reuse of wastes and residues, as required by the Waste Framework Directive, the potential use of waste, residue and natural minerals as low-cost permeable reactive barrier (PRB) materials was investigated. The performance of a kitchen waste compost, sepiolite and steel slag was compared with that of volcanic slag, pumice and activated carbon in removing specific contaminants from landfill leachate. The experiments represented that the activated carbon removed 27% of the ammonium (NH4+), 75% of the chemical oxygen demand (COD) and 100% of the phosphate (PO43–), zinc (Zn2+) and nickel (Ni2+) from the landfill leachate. Volcanic slag exhibited removal efficiencies of 50% COD and 100% PO43– and pumice exhibited removal efficiencies of 20% NH4+, 27% Zn2+, 65% COD and 100% PO43–. The reactive materials were also checked for their potential in releasing unwanted constituents and represented different levels of the solute (e.g., PO43–, SO42–, NH4+) release. Among the reactives, sepiolite was found to be the reactive material reflecting a minor release (e.g., Zn2+, Cd2+ and Ni2+), but also delivering removal efficiencies of 40, 50, 65, 95, 97, 98, 98 and 100% for Ni2+, COD, Zn2+, SO42–, Cl–, F–, NH4+ and PO43–, respectively. The results show that the studied materials have the potential as reactives for PRB systems treating high strength contaminant plumes.

In this study, for the treatment of rice field drainage water; The NO3-N and NH4-N treatment yields of Elodea Densa (Egeria), Lemna Minor (Duckweed), Micranthemum Micranthemoides (Micra), Pistia (Water Lettuce), Ceratophyllum Demersum (Foxtail) plants were investigated. Synthetic drainage water was created by analyzing the literature and the rice field drainage water contents taken from Samsun Bafra region. Artificial wetland studies were carried out separately in order to understand the treatment ability of each plant, and as a batch and continuous system at room temperature for the coexistence of all plants. Periodically pH, electrical conductivity (EC), dissolved oxygen (DO), nitrate (NO3-N), ammonium (NH4-N) values were measured in flower plugs. In the experiments carried out individually as a result of the studies, the wetland plant with the highest nitrate removal efficiency (77%) at the end of 1 day; Elodea Densa was found to be the plant with the highest ammonium removal efficiency (76%) as Pistia. It was observed that the plant treatment efficiency increased as the hydraulic waiting time increased. In their joint system study, at the end of the first day, the NO3-N removal efficiency was 40%, while the NH4-N removal efficiency was 51%. It was concluded that the wetland plants used successfully reduced the ammonium and nitrate content of the drainage water and showed resistance to the drainage water with high salinity content. In the wetland experiments carried out under continuous flow, at the end of the 16th day, NH4-N was reduced from 0.80 mg/L to 0.10 mg, while NO3-N was reduced from 1.90 mg/L to 1.40 mg/L. Studies have generally revealed the importance of plant type as well as waiting time.

a b s t r a c tSoils contaminated by polycyclic aromatic hydrocarbons (PAHs) pose potential risks to human health and the environment. In this study a combined physical-chemical treatment involving soil washing and advanced oxidation was investigated. A fluorene contaminated loamy soil was treated with a washing solution containing a non-ionic surfactant polyoxyethylene 20 cetyl ether (Brij 58). The washing solution containing fluorene (48.5-54.3 mg/L) was afterwards treated with Fenton and electro-Fenton oxidation. The conventional Fenton oxidation results revealed a fast removal of fluorene (>84%) within the first 15 min. COD removal representing the general destruction of washing solution remained at about 10%, but increased to 81% when the reaction time was increased to 480 min using 2% hydrogen peroxide (H 2 O 2 ). The corresponding fluorene removal was about 98%. The pseudo-second order rate constants observed for fluorene (0.0016 L/mg min) and COD (1.5 × 10 -6 L/ mg min) oxidation supported these results by indicating to a faster oxidation of fluorene. Increase in the H 2 O 2 concentration similarly influenced the oxidation of COD rather than fluorene. The COD removal efficiency increased from 43% to 97% when the H 2 O 2 concentration was increased from 2% to 10% for a treatment time of 120 min. Electro-Fenton oxidation studies with a current density of 15 mA/cm 2 and an electrolyte conductivity of 2 mS/cm revealed even better results enabling a reduction in reaction time. 60 min of reaction time with 2% H 2 O 2 represented removal efficiencies of 98% and 91% for fluorene and COD, respectively.