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Effects of persulfate, peroxide activated persulfate and permanganate oxidation on treatability and biodegradability of leachate nanofiltration concentrate

Guvenc Senem Yazici, Varank Gamze, Demir Ahmet

Environment Protection Engineering

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2020

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Vol. 46, nr 3

97--108

EN

The effects of persulfate (PS), peroxide activated persulfate (P-PS) and permanganate (PM) oxidation processes on leachate nanofiltration (NF) concentrate treatment have been activated. Additionally, COD fractions were determined and compared before and after each oxidation process. The total COD removal efficiencies by the oxidation processes using PS, P-PS, and PM as the oxidants were determined to be 24.5%, 32.9%, and 39.5%, respectively. The biodegradable COD fraction increased from 6.37% to 9.25%, 11.51%, and 13.64% after the PS, P-PS, and PM oxidation processes, respectively. About 25%, 34%, and 46% removal efficiencies of the inert COD content of the concentrate were obtained after the PS, P-PS and PM oxidation processes, and the soluble COD fraction increased from 71.1% to 87.2%, 89.0% and 84.6% by the PS, P-PS and PM oxidation processes, respectively. Although the highest removal efficiencies were achieved by PM oxidation with the lowest operational cost, all of the processes may be suggested as efficient methods for conversion of insoluble COD into the soluble COD fraction and for inert COD removal. The results of the study showed that the PS, P-PS, and PM oxidation processes may be effectively utilized as post-treatment techniques for leachate NF concentrate treatment.

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Scattering of Sound Waves in Two Stepped Non-uniformly Lined Duct

Tiryakioglu Ayse, Demir Ahmet

Archives of Acoustics

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2020

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Vol. 45, No. 3

511--520

EN

Scattering of sound waves in two stepped cylindrical duct which walls are coated with different acoustically absorbent materials is investigated by using Wiener-Hopf technique directly and by determining scattering matrices. First, by using Fourier transform technique we obtain a couple of modified Wiener-Hopf equations whose solutions involve four sets of infinitely many unknown expansion coefficients providing systems of linear algebraic equations. Then we determine scattering matrices of the problem and we state the total transmitted field by using generalized scattering matrix method. Numerical results are compared for different parameters.

3

Sound Wave Radiation from Partially Lined Duct

Tiryakioglu Burhan, Demir Ahmet

Archives of Acoustics

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2019

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Vol. 44, No. 2

239--249

EN

The radiation of sound waves from partially lined duct is treated by using the mode-matching method in conjunction with the Wiener-Hopf technique. The solution is obtained by modification of the Wiener-Hopf technique and involves an infinite series of unknowns which are determined from an infinite system of linear algebraic equations. Numerical solution of this system is obtained for various values of the problem parameters, whereby the effects of these parameters on the sound diffraction are studied. A perfect agreement is observed when the results of radiated field are compared numerically with a similar work existing in the literature.