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Denim is a cotton fabric specifically used to manufacture jeans. Denim processing generates complex effluents with high levels of pumice stone, color and chemical oxygen demand (COD). There is therefore a need for advanced treatment methods to limit pollution of natural waters. Here, we hypothesized that Fenton oxidation, a method using Fe2+ and H2O2, could replace the traditional step of activated sludge treatment. We studied a daily composite sample at laboratory scale for preliminary settling, chemical settling and Fenton oxidation. We found that pumice stone can be effectively controlled by preliminary settling with partial COD removal and limited color removal. Chemical treatment improved COD removal, but color reduction still remained partial. Fenton oxidation decreased color below visual detection after 5 min and COD decreased to 110 mg/L after 30 min. These findings surpassed the performances of activated sludge treatment.

This study explored the environmental impact of the large-scale projects, the 3rd Bridge across the Bosphorus and 3rd Airport, carried out in the last decade leading to the massive deterioration of the northern forest area in Istanbul. Destroyed forest area was assessed through relevant changes in land classification detected by multi-temporal Landsat data of Istanbul between 2009 and 2016. The magnitude of destroyed carbon stocks and related CO2 emission together with the reduction in the CO2 absorption potential inflicted by massive land-use change were also calculated. Observed results indicated that approximately 15,000 ha of forest area was destroyed in 7 years, corresponding to a 7% ultimate loss in the total forest area. The total land cover change for the same period was determined as 11.5% of the study area. The extent of land cover changes indicated that more than 4.4 million tons of CO2 were additionally emitted to the atmosphere, due to observed reduction of carbon stocks between 2009 and 2016. More than 70% of the total C/CO2 emission associated with land cover changes could be attributed to the loss of forest land. In addition, destroyed forestland corresponded to a CO2 absorption loss of 0.3 million tons CO2/year equivalent to the emission of 830,000 people in Istanbul.

This study aims to establish the scientific link between the livestock wastes and energy recovery processes to implement the most appropriate technology at the highest economic benefit. The evaluation was based on the recovery of the potential energy of the mixture of four livestock wastes (cattle, sheep, goat, egg chicken) by four different energy recovery processes. Incineration, gasification, pyrolysis at 550°C and 750°C were applied as thermal processes together with the anaerobic digestion as biochemical process. The recovery performance of each process was evaluated within a defined design algorithm considering all significant parameters in seven geographical regions and in Turkey as a whole. Incineration seems to be the most efficient energy recovery process with 0.43 MWe/t for Turkey. Gasification took the second place in the energy recovery ranking with 0.34 MWe/t, 21% less than incineration. Pyrolysis expressed an energy recovery rate of 0.15 MWe/t at 550°C and a twice higher rate at 750°C, at a level close to gasification. Anaerobic digestion exerted a recovery potential of 0.21 MWe/t for the livestock waste considered. Energy recovery from livestock waste not only contributes to energy production, but also provides compliance with the concept of reducing emissions and sustainable environment.

The structure of existing activated models is inherently deficient in reflecting the major role of the membrane filtration. The study developed a novel model, MASM, for the membrane activated process. The effective filtration size imposed by the membrane module, entrapping larger particles, was adopted as the basis of the proposed model. The model defines a modified form of COD fractionation that accounts for the captured COD fractions as additional model components and utilizes related mass-balance relationships. It was implemented to test the fate of soluble hydrolyzable COD and the system performance of super-fast membrane activated sludge based on real data for the characterization and process kinetics of domestic sewage and denim processing effluents. Model evaluation was carried out for parallel systems with gravity settling and membrane filtration operated at a sludge age range of 0.5–2.0 d. Results reflected significantly better performance by the super-fast membrane activated sludge system for both wastewaters, underlining that it was crucially important to account for the captured COD fractions to provide an accurate evaluation of system behavior and effluent quality. This should also be identified as the major shortcoming of the ASM models for evaluating and predicting the system performance of activated sludge configurations with membrane separation.

The purpose of the study was the experimental evaluation of ultrafiltration as a potential innovative technology for the removal of organic matter of around 15,000 mg chemical oxygen demand (COD) per liter in the polymer industry wastewater. Particle size distribution (PSD) analysis served as the major experimental instrument along with conventional chemical settling. Biodegradation characteristics of the remaining COD after ultrafiltration were determined by model interpretation of the corresponding oxygen uptake rate (OUR) profile. The study first involved a detailed characterization of the polymer wastewater including PSD analysis of the COD content. Chemical treatability was investigated using lime alone and with ferric chloride as coagulants followed with a PSD assessment of the chemically settled effluent. Modeling of the OUR profile generated by the ultrafiltration effluent defined related biodegradation kinetics and provided information on the overall COD removal potential. PSD analysis indicated that more than 70 % of the total COD accumulated in the 220- to 450-nm size range. It indicated that ultrafiltration was potentially capable of removing more than 90 % of the COD with an effluent lower than 1,500 mg COD/L. Chemical settling with 750 mg/L of FeCl 3 dosing at a pH of 7.0 provided a similar performance. The ultrafiltration effluent included mainly hydrolysable COD and proved to be biodegradable, with the process kinetics compatible with domestic sewage. PSD evaluation proved to be a valuable scientific instrument for underlining the merit of ultrafiltration as the appropriate innovative technology for polymer wastewater, removing the major portion of the COD in a way that is suitable for recovery and reuse and producing a totally biodegradable effluent.

A new model for the activated sludge process with membrane separation is presented, based on the effective filtration size. A new size threshold is imposed by the membrane module. The model structure requires a modified fractionation of the chemical oxygen demand and includes chemical oxygen demand fractions entrapped in the reactor or in the flocs as model components. This way, it offers an accurate mechanistic interpretation of microbial mechanisms taking place in membrane activated sludge systems. Denim processing wastewater was selected for model implementation, which emphasized the significance of entrapped fractions of soluble hydrolysable and soluble inert chemical oxygen demand responsible for better effluent quality, while underlining the shortcomings of existing activated sludge models prescribed for systems with conventional gravity settling. The model also introduced particle size distribution analysis as a new experimental instrument complementing respirometric assessments, for an accurate description of chemical oxygen demand fractions with different biodegradation characteristics in related model evaluations.

In this study, the ammonia removal efficiency for high ammonia-containing wastewaters was evaluated via partial nitrification. A nitrifier biocommunity was first enriched in a fill-and-draw batch reactor with a specific ammonium oxidation rate of 0.1 mg NH₄ ⁻-N/mg VSS.h. Partial nitrification was established in a chemostat at a hydraulic retention time (HRT) of 1.15 days, which was equal to the sludge retention time (SRT). The results showed that the critical HRT (SRT) was 1.0 day for the system. A maximum specific ammonium oxidation rate was achieved as 0.280 mg NH₄ ⁻-N/mg VSS.h, which is 2.8-fold higher than that obtained in the fill-and-draw reactor, indicating that more adaptive and highly active ammonium oxidizers were enriched in the chemostat. Dynamic modeling of partial nitrification showed that the maximum growth rate for ammonium oxidizers was found to be 1.22 day⁻¹. Modeling studies also validated the recovery period as 10 days.

The study provided a critical appraisal of the extended aeration process as a single-sludge system for nitrogen removal, emphasizing its inherent deficiencies. For this purpose, the system was designed first using the prescribed procedure in the German practice, ATV A-131. The design used the basic data reported in different studies related to conventional characterization and chemical oxygen demand (COD) fractionation defining the biodegradation characteristics of domestic wastewater. A critical appraisal of the design was made with emphasis on the fate of biodegradable COD and oxidized nitrogen in the anoxic phase by process modeling and evaluation. The results obtained were evaluated using basic stoichiometry and mass balance for major nitrogen fractions. The A-131 design based on a total sludge age of 20 days defined a system with a hydraulic residence time of 1.2 days where half of the volume was operated under anoxic conditions; the effluent nitrate concentration was reduced to 8.3 mg N/L with an internal recycle (nitrate) ratio of 4.9. Model evaluation of the prescribed design indicated that oxidized nitrogen was totally consumed within the first 25–30 % portion of the anoxic volume. The remaining volume was forced to operate under anaerobic conditions, where no appreciable endogenous decay would occur. ATV A-131 procedure, relying on empirical coefficients and expressions, was neither consistent with process stoichiometry nor justifiable by modeling. Evaluations based on modeling and process stoichiometry revealed significant inherent weaknesses of extended aeration for providing a sustainable basis for nitrogen removal.

The conceptual framework for the hydrolysis of slowly biodegradable substrate is reviewed by means of a model evaluation of the OUR profiles resulting from different rate expressions and the merit of each proposed mechanism is evaluated on the basis of experimental results. The sensitivity of the experimental evaluation technique, with specific emphasis on parameter identifiability, is investigated in assessing the values of the maximum specific hydrolysis rate, kh and the half-saturation coefficient for hydrolysis, Kx. The results of extensive studies for the experimental assessment of the hydrolysis rate coefficients for both domestic sewage and a number of industrial wastewaters are summarized. Furthermore, the question of organics with different hydrolysis rates is addressed by identifying readily and slowly hydrolyzable COD fractions. Dual hydrolysis approach is evaluated in terms of its implication on process kinetics and especially on the assessment of the endogenous decay mechanism.