Filiz B. Dilek

Treatment of tectilon yellow 2G by Chlorella vulgaris

Treatment of mono-azo dye, tectilon yellow 2G (TY2G), by Chlorella vulgaris was investigated. COD removal efficiencies were determined as 69, 66 and 63% for the initial TY2G concentrations of 50, 200 and 400 mg/l, respectively, whereas acclimation of C. vulgaris caused them to increase to 88, 87 and 88%, respectively. Absorbance spectral profiles obtained for unacclimated algae showed that the peak observed initially at 450 nm disappeared and the one at 220 nm decreased remarkably while there was a new peak formation at 350 nm, indicating the conversion of TY2G to an end product which was further confirmed as aniline by high-performance liquid chromatographic analysis. In the case of acclimated algae, no aniline production was detected. The main mechanism of the removal was bioconversion in the case of unacclimated algae and degradation in the case of acclimated algae. Moreover, the higher the initial algal concentration, the higher is the COD removal efficiency achieved in a much shorter time.

Effectiveness of algae in the treatment of a wood-based pulp and paper industry wastewater

In this study, the ability of algae to treat a wood-based pulp and paper industry wastewater was investigated. Tests were performed in batch reactors seeded with a mixed culture of algae. Under different lighting and initial wastewater strength conditions, changes in COD, AOX and color contents of reactors were followed with time. Algae were found to remove up to 58% of COD, 84% of color and 80% of AOX from pulp and paper industry wastewaters. No remarkable differences were observed in COD and color when light intensity and wastewater strength were changed, while AOX removals were strongly affected. Algal species identification studies revealed that some green algae (Chlorella) and diatom species were dominant in the treatment. The study also showed that algae grew mixotrophically, while the main mechanism of color and organics removal from pulping effluents was partly metabolism and partly metabolic conversion of colored and chlorinated molecules to non-colored and non-chlorinated molecules. Adsorption onto algal biomass was not so effective.

Combined effects of Ni(II) and Cr(VI) on activated sludge

Abstract The combined effects of Ni(II) and Cr(VI) on activated sludge kinetics were studied in this paper. The metals were added to a synthetic medium with a chemical oxygen demand (COD) of 1300 mg 1 −1 to give various combinations of Ni(II) and Cr(VI). Activated sludge performance, in terms of COD removal, was not adversely affected in an acclimatized culture by the metal combinations, compared with the single metals. The combination effects of Ni(II) and Cr(VI) on biokinetic constants, i.e. the maximum specific growth rate, μ m , was found to be stimulatory in general. The same effect was observed on the half-saturation substrate concentration, K s . Effects were therefore classified as synergistic with respect to these constants.

Colour and AOX removal from pulping effluents by algae

Abstract A mixed culture of algae was used to treat pulping mill effluent in terms of removing both colour and adsorbably organic halides (AOX). The removal of AOX from pulping effluent increased with increasing initial colour value of the effluent. However, for the total mill effluent (composed of both pulping and bleaching effluents), AOX removal was found to be independent of initial colour value, and was around 70%. Up to 80% removal of colour from pulping effluent was achieved within 30 days under continuous lighting conditions. It was found that algae reduced the colour of pulping effluent of relatively low initial colour more efficiently than that of high initial colour. Under simulated field lighting conditions, up to 60% colour removal from pulping effluent was observed after 60 days of exposure, whereas for the total mill effluent it was up to 64% after 45 days. Total organic carbon and lignin (UVA280) were also removed to a significant extent, suggesting that the mechanism of colour removal might not be transformation of the coloured lignin molecules to non-coloured ones. Analysis of alkaline extraction of the algal biomass and material balance findings indicated that the main colour removal mechanism was metabolism rather than adsorption. The experimental results were also analysed using multiple regression techniques and a mathematical model was developed to express the removal of colour from pulping effluents in terms of initial colour value, exposure time and lighting periods as well as interactions between these variables.

Adoption of European Union's IPPC Directive to a textile mill: Analysis of water and energy consumption

The present study was undertaken as part of the first application and evaluation of the BREF (Best Available Techniques; BAT Reference Document) Textile Document within the context of the European Unions Integrated Pollution Prevention and Control (IPPC) Directive to a large scale textile mill in Turkey. The BAT requirements for the denim manufacturing textile mill were selected in cooperation with the factory management. Detailed mass balance calculations were conducted to evaluate the overall effect of the selected BAT options. The initial findings indicated that the adoption of the selected BAT options resulted in considerable savings in water and energy consumption in the mill. Besides the installation of flow meters and use of semi-counter current rinsing in the most water-intensive processes, minimization of wash waters in the water softening plant, reuse of the concentrate stream from the reverse osmosis plant and compressor cooling waters provided a 29.5% reduction in the total specific water consumption of the mill, reaching the lower limits suggested by the BREF Textile Document. In terms of energy consumption, use of waste heat from finishing wastewater streams in heating up the wash waters, heat insulation and maintenance applications in addition to BAT measures taken for water minimization reduced specific energy consumption by 9% achieving the limits set by the BREF Textile Document.

Microbial solubilization of lignites

Abstract Biological solubilization and subsequent gasification of lignite samples from three of the largest reserves in this country, which are also characterized by high sulphur contents and low calorific values, were investigated in this project. Several white-rot fungi were screened for their ability to solubilize lignites and Phanerochaete chrysosporium was found to depolymerize Elbistan lignites with 60% efficiency. Acetate served perfectly as the primary carbon source. Whereas, Can lignites could be depolymerized only after lengthy pre-treatment with 8N HNO 3 while Beypazari lignites were completely inert to biological attack. Gasification tests with the solubilize material revealed 21% energy recovery through gaseous methane product.

Nutritional and cultural parameters influencing antidipteran delta-endotoxin production

In this study, various nutritional and cultural parameters influencing diptera-specific delta-endotoxin synthesis by Bacillus thuringiensis subsp. israelensis HD500 were investigated. Of various inorganic nitrogen sources, the highest yields of Cry11Aa and Cry4Ba proteins were obtained on (NH(4))(2)HPO(4). Among carbon sources, inulin, dextrin, maltose, lactose, sucrose, whey and glycerol were all stimulatory, while glucose, starch and molasses were suppressive. High concentrations of inorganic phosphate (50 to 100 mM K(2)HPO(4)) were required for an effective synthesis of Cry4Ba. Mn was the most critical element for the biosynthesis of both toxins at 10(-6) M concentration. Mg and Ca favored production when provided at 8 x 10(-3) M and 5.5 x 10(-4) M concentrations, respectively, while Fe, Zn and Cu negatively influenced biosynthesis. Cry4-toxin synthesis was best at neutral pH and also when the organism was grown at 25 degrees C. Throughout the study, the extent of growth and sporulation of the producer organism was also monitored.

The growth behavior of Chlorella vulgaris in the presence of 4-chlorophenol and 2,4-dichlorophenol.

Toxicity of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) on the growth of Chlorella vulgaris was investigated in batch reactors. Results revealed that 4-CP did not adversely affect the growth of algae up to 20mg/L, however higher concentrations inhibited growth appreciably and no growth was detected at 100mg/L. 4-CP also caused some physiological changes in the algal cells as increasing initial 4-CP concentration caused a linear decrease in chlorophyll a (chl-a) content of the cell. 2,4-DCP up to 20mg/L did not exert toxic effect on the growth of C. vulgaris, rather an induction effect was evident. Unlike a linear decrease with 4-CP, no exact correlation between 2,4-DCP concentration and chl-a content of the cell was observed, but it was certain that the presence of 2,4-DCP caused some physiological changes in the cell of C. vulgaris. No biodegradation of 4-CP and 2,4-DCP was observed over a 30-day incubation.

Effects of CU (II) on a chemostat containing activated sludge

Abstract The purpose of this study was to evaluate the toxic effects of Cu(II) on a chemostat containing activated sludge. Different concentrations of Cu(II) (0.5, 1.0, 5.0, and 10.0mgL‐1) were maintained in a laboratory‐scale completely mixed activated sludge unit, without recycle, treating simulated wastewater. The feed solution contained 650 mgL‐1 protein (corresponding to 1300 mgL‐1 COD) as a source of carbon. Experimental results indicated that the treatment efficiency was not adversely effected by the presence of Cu(II) up to the concentration of 10.0 mgL‐1. Moreover, some stimulatory effects of Cu(II) on the biokinetic parameters were observed.

Modeling chlorophenols degradation in sequencing batch reactors with instantaneous feed-effect of 2,4-DCP presence on 4-CP degradation kinetics

Two instantaneously fed sequencing batch reactors (SBRs), one receiving 4-chlorophenol (4-CP) (SBR4) only and one receiving mixture of 4-CP and 2,4-dichlorophenol (2,4-DCP) (SBRM), were operated with increasing chlorophenols concentrations in the feed. Complete degradation of chlorophenols and high-Chemical oxygen demand (COD) removal efficiencies were observed throughout the reactors operation. Only a fraction of biomass (competent biomass) was thought to be responsible for the degradation of chlorophenols due to required unique metabolic pathways. Haldane model developed based on competent biomass concentration fitted reasonably well to the experimental data at different feed chlorophenols concentrations. The presence of 2,4-DCP competitively inhibited 4-CP degradation and its degradation began only after complete removal of 2,4-DCP. Based on the experimental results, the 4-CP degrader’s fraction in SBRM was estimated to be higher than that in SBR4 since 2,4-DCP degraders were also capable of degrading 4-CP due to similarity in the degradation pathways of both compounds.