Ulku Yetis

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.

Mechanistics of nickel sorption by activated sludge

Biomass from activated sludge reactors operating at different dilution rates (0.09, 0.16, and 0.24/h) was used to examine the effect of sludge age on Ni2+ removal characteristics, running batch adsorption tests. The kinetic studies have revealed that sludge grown at all dilution rates, exhibits both active and passive uptake of Ni2+. Although percentages of active and passive uptake changed with the age of activated sludge biomass, passive uptake was the dominant mechanism in Ni2+ sorption. The data obtained were interpreted in the form of adsorption isotherms. At all dilution rates, linear adsorption isotherms were obtained, indicating the presence of equilibrium between biomass and the free nickel species.

Decolorization of wastewater of a baker's yeast plant by membrane processes

The aim of this study is to develop a membrane-based treatment scheme to remove colorants from the effluent of a bakers yeast plant. For this purpose microfiltration (MF), ultrafiltration (UF) and nanofiltraton (NF) membranes with differing molecular weight cut-offs (MWCOs) were tested. To evaluate the effectiveness of membrane processes in treating the waste stream, optical density (OD), COD, color measurements together with permeation fluxes were used. Effects of pretreatment methods (coagulation and coarse filtration) and feed composition on OD, color, COD were studied. In addition, gel filtration analysis was employed to characterize feed and permeate streams in terms of MW distribution of organics that are present. Maximum rejections obtained were 94%, 89% and 72% for OD, color and COD, respectively, when 0.8 microm microfiltration membrane and 400 Da NF membrane were used in series. It was also observed that addition of intermediate UF steps did not increase overall rejections and final permeate flux of NF membrane. Based on these observations, an efficient scheme was offered.

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.

Effect of nickel(ii) on activated sludge

Abstract There is little information in the literature to describe the effects of heavy metals on activated sludge kinetics. The purpose of this study is to evaluate the toxic effect of nickel on activated sludge. Different concentrations of Ni(II) (5.0, 10.0 and 25.0 mg l −1 ) were maintained in a laboratory-scale completely mixed activated-sludge unit, without recycle, treating, simulated wastewater. The feed solution contained 650 mg l −1 protein (corresponding to 1300 mg l −1 COD) as a source of carbon. Experimental results indicated that the treatment efficiency was not adversely affected by the presence of nickel up to a concentration of 10.0 mg l −1 . However, a concentration of 25.0 mg l −1 Ni(II) caused serious upsets in the system, while 5.0 mg l −1 Ni(II) in feed solution had some stimulatory effects. The maximum specific growth rate, μ m , of the culture also doubled when the nickel concentration was 5.0 mg l −1 and better floc formation was noticed at this nickel concentration.

Effect of chromium(VI) on activated sludge

Abstract Hexavalent chromium, which is frequently encountered in the tannery effluents and in the electroplating wastes, is normally considered toxic to the activated sludge culture. Often a physico-chemical pretreatment prior to biological treatment is considered necessary. However, in this study it has been shown that an acclimatized activated sludge culture is fully capable of coping with the Cr(VI)-containing wastes and moreover the culture was significantly stimulated by up to 25 mg l−1 Cr(VI). None of the tested concentrations of this metal were inhibitory to the mixed culture under investigation. In fact, all of the concentrations tested, 1, 5, 10 and 25 mg l−1 Cr(VI), significantly stimulated the maximum growth rate, μm, of the culture. Furthermore, the biomass yield of the activated sludge culture markedly increased in the presence of Cr(VI) while the effect on the biomass decay or maintenance constants was variable.

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.

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.

Effect of chromium(VI) on the biomass yield of activated sludge

Effect of 1‐25 mg/l of influent Cr(VI) concentrations on true biomass yield ( Yt) and decay coefficient (kd) of activated sludge units was investigated in this study. To this purpose, completely mixed, once-through laboratory scale activated sludge units with acclimated cultures were operated. After obtaining dilute-out curves for each Cr(VI) concentration, the values of Yt and kd were determined. The results revealed that presence of Cr(VI) caused stimulatory effects on biomass yield and maintenance up to the Cr(VI) concentration of 25 mg/l. Lower Cr(VI) concentrations exerted higher stimulation of the system. Extended oxidation due to the presence of Cr(VI) and/or increased synthesis of cellular material due to the stimulatory effects of Cr(VI) were thought to be the mechanisms of the observed stimulation.

Nanofiltration and Reverse Osmosis for Reuse of Indigo Dye Rinsing Waters

A membrane based treatment strategy was developed for the possible recycling of rinsing wastewater from indigo dyeing to the process itself. Performances of three different nanofiltration (NF) (NF 270 and NF 90, Dow Film Tech, USA and NF 99, Alfa Laval, Denmark) and two different reverse osmosis (RO) (HR 98 PP and CA 995 PE, Alfa Laval, Denmark) membranes were investigated with wastewater collected from the first post-rinsing tank of indigo dyeing process of a denim manufacturing plant. Dead-end microfiltration with a 5 µm filter was employed to remove coarse particles and minimize fouling of further NF and RO membranes. For NF and RO, a lab scale plate-and-frame membrane module was operated at a pressure of 5.07 bar and at a 0.62 m/s cross-flow velocity. The permeate quality from all the tested NF and RO membranes was acceptable for reuse in terms of COD and color. However, only the permeate from HR 98 PP RO and NF 90 membranes were with an acceptable conductivity. On the other hand, NF 270 membrane was superior to all the other NF and RO membranes in terms of the permeation rate. Flux declines obtained for all membranes were higher than 50% but fouling was not considerable and completely reversible. The good performance of NF 270 in terms of permeate quality (permeate conductivity, color, and COD values were 4.3 mS/cm, 8 Pt-Co, and 87 mg/L, respectively) together with a higher flux makes this membrane preferable over the other membranes to recycle denim textile rinsing wastewaters.