G. Eremektar

An OUR-based approach to determine the toxic effects of 2,4-dichlorophenoxyacetic acid in activated sludge

This study uses the oxygen uptake rate (OUR) measurement to measure toxicity effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on activated sludges fed with the wastewater from a small domestic wastewater treatment plant and peptone-based synthetic wastewater. Two 2l lab-scale batch reactors were run in parallel with the same F/M ratios (0.4 mg COD per mg VSS per day) to assess the inhibition effects of 2,4-D concentrations between 25 and 75 mg l(-1) considering at least a 100% dilution rate, as compared with a pesticide industry effluent containing 20,000-40,000 mg l(-1) COD, reaches a central treatment plant. It was noted that the OUR was decreased to 15 and 30%, respectively, when adding 75 mg l(-1) of 2,4-D to the domestic and synthetic reactors. Meanwhile, the addition of 25 plus 50 mg l(-1) of 2,4-D in sequence to the domestic wastewater reactor did not significantly affect the OUR profile. The OUR-based inhibition definition has been used in this research since the OUR methods have been frequently used and cited in the literature to study toxicity effects. However, the origin of the sludge used in the testing is also important. Synthetic wastewater may simulate the toxicity studies but with a higher response than actual systems, since the microorganisms are considerably becoming substrate-selective.

Evaluation of treatability for two textile mill effluents

Abstract The study emphasizes wastewater characteristics of two different textile plants as they apply to biological treatment. Although conventional characterization reveals no major differences, the effluents from the acrylic fiber and yarn dyeing plant exhibit all the properties of a non-biodegradable wastewater. Appropriate pretreatment consisting of partial chemical oxidation with H 2 O 2 reduces its COD content to 700 mg I −1 , almost entirely biodegradable whereas COD fractionation indicates that the effluents of the cotton knit dyeing plant contain 9% residual fractions. Experimental investigation shows that most kinetic and stoichiometric properties of both wastewaters are compatible with that of domestic sewage with the exception of a much slower hydrolysis rate.

Pre-Ozonation of Commercial Textile Tannins: Effects on Biodegradability and Toxicity

The effect of ozonation on the biodegradability and acute toxicity of two frequently used textile dye assisting chemicals, namely natural tannin (NT) having an initial chemical oxygen demand (COD0) of 1195 mg L−1; initial total organic carbon (TOC0) of 342 mg L−1; initial 5th-day biochemical oxygen demand (BOD5,0) of 86 mg L−1; initial ultraviolet absorbance at 280 nm wavelength (UV280,0) of 32.2 cm−1; initial ultraviolet absorbance at 254 nm wavelength (UV254,0) of 19.35 cm−1 and synthetic tannin (ST); with a COD0 of 465 mg L−1; TOC0 of 155 mg L−1; BOD5,0 of 6 mg L−1; UV280,0 of 11.78 cm−1; UV254,0 of 13.74 cm−1 was investigated. Synthetic wastewater bearing these tannin formulations was individually prepared and subjected to ozonation at varying doses (500 and 1000 mg h−1), and pHs (3.5 and 7.0) to elucidate the effect of ozone dose and pH on oxidation efficiency. Changes in the environmental sum parameters chemical oxygen demand (COD), total organic carbon (TOC), 5th-day biochemical oxygen demand (BOD5), ultraviolet absorbance at 280 nm wavelength (UV280) and ultraviolet absorbance at 254 nm wavelength (UV254), the latter two representing the aromaticity and double bonds of the studied textile tannins, respectively, were monitored during the course of ozonation. In the second part of the study, the biodegradability and acute toxicity of the raw and pre-ozonated textile tannins were evaluated in terms of the BOD5 parameter and an activated sludge inhibition test, respectively. Results indicated no significant changes in acute toxicity for NT, whereas the inhibitory effect of ST could be completely eliminated after 40 min ozonation at a rate of 1000 mg h−1 (i.e., at a specific ozone dose of 1.4 mg O3 (mg COD0)−1 and a pH of 3.5. In conclusion, pre-ozonation appeared to be potential pretreatment option to achieve complete detoxification and a fair biodegradability improvement of the otherwise refractory synthetic tannin.

Feasibility Analysis of In-Plant Control for Water Minimization and Wastewater Reuse in a Wool Finishing Textile Mill

Abstract This study evaluates the feasibility of water minimization and wastewater reuse for a wool finishing textile mill. The evaluation process is based upon a detailed analysis on water use, process profile and wastewater characterization, indicating a potential for 34% reduction in water consumption and for 23% of wastewater recovery for reuse. Wastewater reuse requires treatment and results in a remaining wastewater stream with stronger character and consequently more costly to treat. The feasibility includes technical considerations for appropriate treatment alternatives and related cost factors for water consumption, treatment for reuse and for discharge either to sewer or to receiving media.

Inert COD fractions in two‐stage treatment of a pulp and paper mill effluent

Two-stage biological treatment schemes are often prescribed for pulp and paper mill effluents with high COD concentrations, in order to meet effluent standards. Recent conceptual developments in biological treatment of wastewaters indicate that the stoichiometry of the inert organic components is the key issue in performance predictions and the kinetics of degradable organic fraction play a relatively less important role in the compliance of effluent limitations. Besides, the differentiation between initially inert COD and inert metabolic products is very important in two-stage systems, as what is biodegradable for one phase may become non-biodegradable for the next phase in which a different microbial community is sustained. In this study a pulp and paper mill effluent is characterized in terms of its inert COD fractions and the changes induced by two-stage biological treatment to these fractions are observed.

Coagulation-Flocculation of Wastewaters from a Water-Based Paint and Allied Products Industry and its Effect on Inert COD

In this study, treatability of wastewaters generated from a water-based paint and allied products industry has been investigated. As the industry already houses a treatment facility that consists of a coagulation-flocculation unit followed by an activated sludge process, the experimental study focuses on using the existing treatment plant in the most efficient way. In this context the COD removal efficiencies and operating costs of different coagulants i.e., sodium bentonite, alum, FeCl3 and FeSO4 have been evaluated. By assessing the refractory COD content of the subsequent activated sludge system outlet, the coagulant yielding the optimal output has been addressed. The outcomes reveal that the optimum result can be obtained by applying 50 mg L−1 of FeCl3 coagulant at the original pH of the effluent.

Fate of inert cod fractions in two‐stage biological treatment of a strong wastewater

Abstract In this study, the effluent of an alcohol distillery after passing through a chemical treatment is characterized in terms of its inert COD Suctions and the changes likely to be induced by two‐stage biological treatment on the magnitude of these fractions are observed. The experimentally obtained results indicated that the anaerobic treatment gives lower soluble inert COD fractions than a corresponding aerobic treatment for the investigated wastewater. Therefore, the preference of anaerobic treatment instead of an aerobic one as the first stage is ascertained. The anaerobic first stage has a COD removal efficiency of 96 %, whereas with a subsequent aerobic treatment 79 % removal can be achieved on the basis of the stoichiometry of the inert COD. The anaerobic full‐scale plant performance of 80 % can be improved up to 96 %.

The pollution profile of alcohol distilleries treating beet sugar molasses

Fermentation of molasses and refining the produced alcohol by distillation is a common agroindustrial activity. The wastewaters originating from the process, especially the spent mash, are highly concentrated and contain TDS of over 50,000 mg/l as well as organic matter. Character of wastewaters varies with production application which affects the treatability characteristics. In this study four alcohol distillery plants treating beet sugar molasses are investigated to assess production applications and wastewater characteristics. Process profiles for three major modes of operation are prepared. Use of open steam and recycle of spent mash was calculated to affect the wastewater volume up to 25%. COD load is found to be practically unchanged with recycle while TDS increased significantly. Nature of COD and treatability characteristics are also expected to vary with recycle.

Urban wastewater treatment plants and reuse potential in Turkey: selected examples from the western cities

The present study refers to the outcomes of a detailed survey on the current situation of Turkish Urban Wastewater Treatment Plants (UWWTPs). The survey covers the identification of the population served by UWWTPs, presentation of the current technologies (physical, biological and advanced) applied in the countrys UWWTPs, prevailing effluent disposal criteria, detailed assessment of UWWTPs selected from the Western part of Turkey representing highly urbanised and industrialised districts, and elucidation of needs for upgrading the selected UWWTPs to comply with the current discharge standards and irrigation water quality criteria. Following an extensive data collection and evaluation step, Turkeys most recent situation in the number of UWWTPs, effluent produced in Turkish municipalities both quantity-and quality-wise, urban wastewater treatment types and disposal methods as well as reuse potential of treated urban wastewater have been presented and discussed.