Browsing by Author "Yetis, Ulku"

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Ozonation pre and post-treatment of denim textile mill effluents: Effect of cleaner production measures
(ELSEVIER SCI LTDTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2016) Morali, E. Kaan; Uzal, Nigmet; Yetis, Ulku; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Uzal, Nigmet
Denim production, which is one of the leading sub-sectors of textile industry that generates considerable amount of wastewater with high pollution load both from dyeing and finishing processes. This sub-sector is therefore to consider cleaner production opportunities for these processes to reduce its wastewater generation and pollution load. In a denim-producing plant, the wastewater treatability studies have revealed that the most technically applicable cleaner production alternatives are caustic recovery from alkaline finishing wastewaters, and reuse of indigo dyeing wastewaters via the application of membrane filtration. In the present study, impact of the changes in the final effluent quality due to the foreseen cleaner production measures were considered in reference to the evaluation of impact on ozonation treatment of the effluent from a denim-producing plant. Ozonation was applied as pretreatment to the effluent from the plant before the foreseen measures (chemical oxygen demand, COD = 2750 mg/L; color = 3950 Pt-Co), and to the simulated effluent after the foreseen measures (COD = 3100 mg/L; color = 4500 Pt-Co); and also as post-treatment to the biologically treated effluent (COD = 800 mg/L; color = 3700 Pt-Co) before the foreseen measures. When applied to the effluent before the foreseen measures as pretreatment, ozonation provided 86% color and 46% COD removal with 3240 mg/h ozone dose in 70 min. However, less satisfactory results were obtained with the wastewater after the measures; with 86% color and 31% COD removals at 3960 mg/h ozone dose in 80 min. In parallel to the decrease observed in COD removal, ozone consumption was also much higher than that for the wastewater before the cleaner production measures. The findings have indicated that the environmental benefits to be brought by cleaner production measures have to be balanced against the risks to be encountered in the treatment of the final effluent. (C) 2016 Elsevier Ltd. All rights reserved.
Recovery of caustic from mercerizing wastewaters of a denim textile mill
(DESALINATION PUBL, 2015) Varol, Cihangir; Uzal, Nigmet; Dilek, Filiz Bengu; Kitis, Mehmet; Yetis, Ulku; 0000-0002-0912-3459; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Uzal, Nigmet
The objective of this study was to evaluate caustic recovery from mercerizing wastewater originating from a denim textile producing plant using membrane technology. For this purpose, ultrafiltration (UF) and nanofiltration (NF) processes were considered. In the first stage, in an attempt to control the possible membrane fouling, pretreatment alternatives of flocculation, centrifugation, and microfiltration were evaluated. These pretreatment application alternatives were unsuccessful as they did not provide considerable color and solids removal. In the second stage, UF and NF processes were tested using a tight UF membrane (GR95PP, Alfalaval) and three NF membranes (NP010 and NP030, Microdyn Nadir, and MPF34, Koch Membranes) to accomplish the caustic recovery without applying any pretreatment. The best performance was obtained with NP010 NF in terms of permeate flux along with color and COD rejections. Then, for this membrane the effects of transmembrane pressure (4.03 and 6.23 bar), cross-flow velocity (from 0.40 to 1.40 m/s), and feed temperature (20 and 40°C) were investigated. Temperature positively affected the permeate flux without significant loss in recovery and rejections. Caustic stream produced had about 98–100% of NaOH in the feed at a concentration of 30–40 g/L and therefore was recyclable after a concentration process.
Removal of pesticides from secondary treated urban wastewater by reverse osmosis
(SPRINGER, 2023) Ates, Nuray; Uzal, Nigmet; Yetis, Ulku; Dilek, Filiz B.; 0000-0002-0912-3459; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Uzal, Nigmet
The residues of pesticides that reach water resources from agricultural activities in several ways contaminate drinking water resources and threaten aquatic life. This study aimed to investigate the performance of three reverse osmosis (RO) membranes (BW30-LE, SW30-XLE, and GE-AD) in rejecting four diferent pesticides (tributyl phosphate, futriafol, dicofol, and irgarol) from secondary treated urban wastewater and also to elucidate the mechanisms underlying the rejection of these pesticides. RO experiments were conducted using pesticide-spiked wastewater samples under 10 and 20 bar transmembrane pressures (TMP) and membrane performances were evaluated. Overall, all the membranes tested exhibited over 95% rejection performances for all pesticides at both TMPs. The highest rejections for tributyl phosphate (99.0%) and irgarol (98.3%) were obtained with the BW30-LE membrane, while for futriafol (99.9%) and dicofol (99.1%) with the GE-AD membrane. The increase in TMP from 10 to 20 bar did not signifcantly afect the rejections of all pesticides. The rejection performances of RO membranes were found to be governed by projection area as well as molecular weight and hydrophobicity/hydrophilicity of pesticides. Among the membranes tested, the SW30-XLE membrane was the most prone to fouling due to the higher roughness.