Person: ÇALLI, BARIŞ
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ÇALLI
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BARIŞ
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Publication Metadata only Extent of bioleaching and bioavailability reduction of potentially toxic heavy metals from sewage sludge through pH-controlled fermentation(PERGAMON-ELSEVIER SCIENCE LTD, 2021) TUĞTAŞ KARNABAT, ADİLE EVREN; Yesil, Hatice; Molaey, Rahim; Calli, Baris; Tugtas, Adile EvrenUtilization of anaerobically stabilized sewage sludge on arable lands serve as a renewable alternative to chemical fertilizers as it enables recycling of valuable nutrients to food chain. However, probable pres-ence of heavy metals in sewage sludge restricts the use of stabilized sludge on lands. In this study, a novel approach based on pH-controlled fermentation and anaerobic metal bioleaching was developed to reduce ecotoxicity potential of fermented sludge prior to its land application. Sewage sludge was sub-jected to pH-controlled fermentation process at acidic, neutral, and alkaline pH levels with the aim of increasing metal solubilization and decreasing bioavailable metal fractions through anaerobic bioleaching. Alkaline reactor performed the best among all reactors and resulted in 3-fold higher hydrolysis (34%) and 6-fold higher acidification (19%) efficiencies along with 43-fold (in average) higher metal solubiliza-tion than that of neutral pH reactor. As a result of alkaline fermentation, 32-57% of the metals remained as bioavailable and 34-59% of the metals were encapsulated as non-bioavailable within solid fraction of fermented sludge (biosolid), whereas 8-12% of total metal was solubilized into fermentation liquor. Our results reveal that anaerobic bioleaching through alkaline fermentation enables biosolid production with less metal content and low bioavailability, facilitating its utilization for agricultural purposes. (c) 2021 Elsevier Ltd. All rights reserved.Publication Metadata only A hybrid dry-fermentation and membrane contactor system: Enhanced volatile fatty acid (VFA) production and recovery from organic solid wastes(PERGAMON-ELSEVIER SCIENCE LTD, 2021) TUĞTAŞ KARNABAT, ADİLE EVREN; Yesil, Hatice; Calli, Baris; Tugtas, Adile EvrenAnaerobic dry-fermentation of food wastes can be utilized for the production of volatile fatty acids (VFA). However, especially for high load fermentation systems, accumulation of VFAs may result in inhibition of fermentation process. In this study, separation of VFAs from synthetic mixtures via a vapor permeation membrane contactor (VPMC) system with an air-filled polytetrafluoroethylene (PTFE) membrane was assessed at various temperatures and permeate solution concentrations. In addition, a pioneering integrated leach-bed fermentation and membrane separation system was operated with undefined mixed culture for the purpose of enhanced VFA production along with its recovery. Hybrid system resulted in 42% enhancement in total VFA production and 60% of total VFAs were recovered through the VPMC system. The results of this study revealed that integrated system can be exploited as a means of increasing organic loading to fermentation systems and increasing the value of VFA production. (c) 2021 Elsevier Ltd. All rights reserved.Publication Metadata only Removal and recovery of heavy metals from sewage sludge via three-stage integrated process(PERGAMON-ELSEVIER SCIENCE LTD, 2021) TUĞTAŞ KARNABAT, ADİLE EVREN; Yesil, Hatice; Molaey, Rahim; Calli, Baris; Tugtas, Adile EvrenHeavy metal contamination of sewage sludge is one of the concerns preventing its land application. Traditional processes applied for stabilization of sewage sludge are still inadequate to serve sustainable solutions to heavy metal problem. In this study, fermentation and bioleaching potentials of sewage sludge were investigated in anaerobic reactors for either non-pretreated or ultrasonicated sludge at three different pH regimes (free of pH regulation, acidic, and alkaline). The results of the study revealed that combination of ultrasonication pretreatment and alkaline fermentation performed the best among the other cases, resulting in 33.7% hydrolysis, 10.5% acidification, 11-33% metal leaching, and up to 25% reduction in bioavailability of potentially toxic heavy metals. Bioleaching effluent obtained from the best performing reactor was subjected to membrane-based metal recovery. A supported liquid membrane impregnated with a basic carrier successfully recovered soluble metals from the bioleaching effluent with an efficiency of 39-68%. This study reveals that the proposed three-stage process, ultrasonication pretreatment-alkaline fermentation-supported liquid membrane, effectively produces stable sludge with reduced heavy metal toxicity and recovers metals from organic waste streams. (C) 2021 Elsevier Ltd. All rights reserved.Publication Metadata only Enhanced heavy metal leaching from sewage sludge through anaerobic fermentation and air-assisted ultrasonication(PERGAMON-ELSEVIER SCIENCE LTD, 2021) TUĞTAŞ KARNABAT, ADİLE EVREN; Molaey, Rahim; Yesil, Hatice; Calli, Baris; Tugtas, Adile EvrenInterest in using stabilized sewage sludge in agriculture is mainly to benefit from its nutrient content, soil conditioning properties, and water holding capacity. Therefore, sludge management practice needs to be directed from treatment liability towards the recovery of chemical assets embedded in sludge. In this study, anaerobic fermentation process integrated with a new treatment method; i.e., air-assisted ultra-sonication, was used to assess the leaching of heavy metals (HM) from waste activated sludge (WAS). Fermentation processes resulted in 9390 mg COD/L of volatile fatty acids (VFAs) production, 26% Ni solubilization and up to 3.4% solubilization of other target metals (Cu and Zn). Application of the air-assisted ultrasonication as a post-treatment to fermentation process stimulated the migration and transformation of HMs to the liquid fraction of the digestate. Applying specific energy input greater than 9 kJ/g total solids (TS) through ultrasonication and supplying air with constant flow rate of 0.875 L of air/(L of digestate.min) resulted in leaching of more than 83% of Ni, 82% of Cu and 80% of Zn. (C) 2021 Elsevier Ltd. All rights reserved.Publication Metadata only Anaerobic fermentation of organic solid wastes: volatile fatty acid production and separation(IWA PUBLISHING, 2014) TUĞTAŞ KARNABAT, ADİLE EVREN; Yesil, H.; Tugtas, A. E.; Bayrakdar, A.; Calli, B.Anaerobic fermentation of organic municipal solid waste was investigated using a leach-bed reactor (LBR) to assess the volatile fatty acid (VFA) production efficiency. The leachate recycle rate in the LBR affected the VFA composition of the leachate. A six-fold increase in the recycle rate resulted in an increase of the acetic acid fraction of leachate from 24.7 to 43.0%. The separation of VFAs via leachate replacement resulted in higher total VFA production. VFA separation from synthetic VFA mix and leachate of a fermented organic waste was assessed via a counter-current flow polytetrafluoroethylene (PTFE) membrane contactor. Acetic and propionic acid permeation fluxes of 13.12 and 14.21 g/m(2).h were obtained at low feed pH values when a synthetic VFA mix was used as a feed solution. The highest selectivity was obtained for caproic acid compared to that of other VFAs when synthetic VFA mix or leachate was used as a feed solution. High pH values and the presence of suspended solids in the leachate adversely affected the permeation rate.Publication Metadata only Influence of volatile fatty acids in anaerobic bioleaching of potentially toxic metals(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2021) TUĞTAŞ KARNABAT, ADİLE EVREN; Molaey, Rahim; Yesil, Hatice; Calli, Baris; Tugtas, Adile EvrenPotentially toxic metals are common contaminants associated with sewage sludge, and limited information is available on migration and transformation behavior of potentially toxic metals during anaerobic digestion (AD) process. The aim of this study was to reveal the influence of volatile fatty acids (VFAs) on the solubilization of metals through VFAs-metal complexation. Addition of readily biodegradable extra carbon source at organic loading rate (OLR) of 17.65 gVS/L.d resulted in accumulation of 67,255 mg chemical oxygen demand (COD)/L as VFAs. Low pH values due to VFAs accumulation enhanced the solubilization of Ni and more than 22% of its total concentration became soluble. Subsequent to consumption of VFAs and increase of pH to neutral levels (similar to 7.5), solubility of Ni decreased below 10% of its total concentration. Contrarily, the solubility of Cr reached to 25% of its total concentration at neutral pH values. Presumably the complexation of Cr with dissolved organic matter (DOM) have increased its concentration in the liquid fraction at neutral pH values. Fractionation analysis of metals revealed that AD process altered Cu and Zn speciation between organically-bound and residual fractions, and hence solubility of Zn and Cu remained consistently low over the entire period of the AD process.