Kinetic investigation and optimization of a sequencing batch reactor for the treatment of textile wastewater

Discharging of untreated or partially treated textile wastewater is common in Ethiopia, and this has detrimental effect to the environment. It is difficult to treat textile wastewater by conventional biological processes. In this study, real textile wastewater was taken and treated using sequencing batch reactor using a biomass taken from domestic wastewater treatment plant. Cycle period, air flowrate and sludge retention time (SRT) were initially optimized using the response surface methodology. The optimum ratio of cycle period/air flowrate/SRT which gives a 57% COD removal and 54% color removal was found to be 25 h/15 L/h/16 day. Using two types of wastewater substrate concentrations and various hydraulic retention times at optimized condition, COD removal, color removal, sludge volume index (SVI) and mixed liquor suspended solid were measured. The maximum of COD removal (73%) and color removal (65.8%) was obtained at an organic loading rate of 0.078 kg COD/m3 day. SVI at the optimized condition was found to be 90–92 mL/g. Finally, a first-order kinetic model was used to represent the degradation of textile wastewater

Using Box–Behnken experimental design to optimize the degradation of Basic Blue 41 dye by Fenton reaction

Degradation of a Basic Blue 41 dye using Fenton reagent was examined at laboratory scale in batch experiments using Box-Behnken statistical experiment design. Dyestuff, hydrogen peroxide (H2O2) and ferrous ion (Fe2+) concentrations were selected as independent factors. On the other hand, color and chemical oxygen demand (COD) removal were considered as the response functions. The value of coefficient of determination (R-2) for both color and chemical oxygen demand removal with values 0.98 and 0.99 shows the best agreement between predicted value and experimental values. Perturbation plots indicated that iron dosage has the most effect on both color and COD removal. Normalized plot of residuals also indicated that the models were adequate to predict for both responses. Color and COD removal increased with increasing H2O2 and Fe2+ concentrations up to a certain level. High concentrations of H2O2 and Fe2+ did not result in better removal of color and COD due to hydroxyl radical being gradually consumed by both oxidant and catalyst. Percent color removal was higher than COD removal indicating the production of colorless compounds. The second-order polynomial model revealed optimal process factor ratio. The ratio of H2O2/Fe2+/dyestuff which gives a complete color removal and 95% COD removal was found to be 1195 mg/L/90 mg/L/255 mg/L

Characterization of crop residues from false banana/Ensete ventricosum/in Ethiopia in view of a full-resource valorization

Research ArticleFalse banana /Ensete ventricosum [Welw.] Cheesman/ is exploited as a food crop in Ethiopia where it represents an important staple food. The plant is harvested and large amounts of biomass residues are originated, mainly from the pseudo stem (i.e., fiber bundles obtained from the leaf sheaths after being scrapped to produce starchy food) and the inflorescence stalk. These materials were studied in relation to their summative chemical composition, composition of lignin, lipophilic and polar extracts. Moreover, their structural characteristics, in view of their valorization, were scrutinized. The analytical studies were performed with the aid of FTIR, GC/MS, Py-GC/MS and SEM. The fiber bundles are aggregates of mainly long and slender fibers with low ash, extractives and lignin contents (3.8%. 4.4% and 10.5% respectively) and high holocellulose and α-cellulose contents (87.5% and 59.6% respectively). The hemicelluloses in the fibers are mostly highly acetylated xylans and the lignin is of the H-type (H:G:S, 1:0.7:0.8). This lignin composition is in line with the FTIR peaks at 1670 cm-1 and 1250 cm-1.The inflorescence stalk has high ash content (12.3% in the main stalk and 24.6% in fines) with a major proportion of potassium, high extractives (25.9%), and low lignin and α-cellulose contents (5.8% and 17.9% respectively). The stalk includes numerous starch granules in the cellular structure with the predominant presence of parenchyma. The potential valorization routes for these materials are clearly different. The fiber bundles could be used as a fiber source for paper pulp production with the possibility of a prior hemicelluloses removal while the inflorescence stalk has nutritional value for food and fodder. Furthermore, it can also be used for sugar fermentation productsinfo:eu-repo/semantics/publishedVersio

Crystallization and postcrystallization of poly(ethyleneterephtalate) under processing conditions

Dottorato di ricerca in tecnologie chimiche dei nuovi materiali. Supervisori Stefano Piccarolo e Valerio BrucatoConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Utilization of Cactus Peel as Biosorbent for the Removal of Reactive Dyes from Textile Dye Effluents

Textile industries generate large quantities of dye containing wastewater which pose a serious environmental problem. Currently, biosorbents have become desirable for the removal of dyes from textile effluents. In this study, batch experiments were conducted to investigate the biosorption characteristics of cactus peel on the removal of reactive red dye from aqueous solutions. The effects of solution pH, biosorbent dosage, contact time, and initial concentration were studied. The interaction effects of process variables were analysed using response surface methodology. The results showed that removal efficiency increased as initial dye concentration and solution pH decreased and as biosorbent dosage and contact time increased. The highest removal efficiency (99.43%) was achieved at solution pH, initial dye concentration, biosorbent dose, and contact time of 3.0, 40 mg/l, 6 g, and 120 min, respectively. From regression analysis, the Langmuir isotherm was found to better (R2 = 0.9935) represent the biosorption process as compared with the Freundlich isotherm (R2 = 0.9722). Similarly, the pseudo-second-order model was seen to represent very well the biosorption kinetics. The results show that cactus peel has good potential for the removal of reactive red dye

Integration of sequencing batch reactor and homo-catalytic advanced oxidation processes for the treatment of textile wastewater

It is unusual to observe completely treated textile wastewater in Ethiopia. It is impossible to get better quality of treated effluent with a single treatment stage. Therefore, in this study the removal of COD and color was carried out on a wastewater which was obtained from acrylic fiber processing textile industry using a single-stage Fenton oxidation, single-stage sequencing batch reactor (SBR) and also with the integration of SBR with Fenton oxidation. Optimum amount of process factors was used for both Fenton oxidation and SBR treatment stages. The combination of SBR and Fenton oxidation was revealed better removal efficiency than single SBR-stage treatment. The effluent obtained from SBR at steady-state conditions indicated a maximum COD and color removal of 74.1% and 64.6%, respectively. The effluent obtained from Fenton followed by SBR (Fenton + SBR) at steady-state conditions was indicated a maximum COD and color removal efficiency of 86.3% and 84%, respectively. The effluent obtained from SBR followed by Fenton (SBR + Fenton) for three Fenton oxidation experimental runs indicated a maximum COD and color removal of 80.2% and 73.6%, respectively. Among the three wastewater treatment schemes, chemical treatment before biological stage (Fenton + SBR) was the best treatment option and also showed better quality of effluent

Photocatalytic Decolorization of Methylene Blue by N-doped TiO2 Nanoparticles Prepared Under Different Synthesis Parameters

Although several studies concerning the preparation of nitrogen doped titanium dioxide visible-light active photocatalyst have already been reported, the effects of dopant concentration and calcination temperature have been rarely investigated. This paper focuses on the preparation of nitrogen doped titanium dioxide (N-doped TiO2) under different calcination temperature and nitrogen dopant concentration synthesizes by sol-gel method. The physicochemical characteristics of the prepared samples were examined using X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), Brunauer Emmett Teller (BET) analyzer, and UV-Vis spectrometer. Methylene blue was used in this study as a test chemical. The results demonstrated that the sample prepared under calcination temperature of 600 oC show 8.33 and 5.57 % of rutile TiO2 phase depends on the dopant concentration. Furthermore, the sample prepared at a lower calcination temperature of 400 oC and nitrogen to titanium (N/Ti) molar ratio of 2 and 6 exhibited larger specific surface area of 80.18 and 77.07 m2g-1, respectively. The photoactivity of the catalyst was also investigated on methylene blue decolorization using the different N-doped TiO2 sample. The experiments demonstrated that the sample prepared at higher N/Ti molar ratio (6) and lower calcination temperature (400 oC) demonstrates about 80 % efficiency under visible light. It was concluded that the higher photoactivity of the N-doped sample prepared at higher dopant concentration and lower calcination temperature is due to synergistic effects of higher surface area, smaller crystal size and higher nitrogen content in the crystal lattice of TiO2

Graphical comparison of enset fiber bundle and inflorescence stalk chemical composition with other biomass sources.

<p>Graphical comparison of enset fiber bundle and inflorescence stalk chemical composition with other biomass sources.</p

Summative chemical composition (mass % o.d. material) and monosaccharide composition (molar % of total monosaccharaides) of the enset fibers and stalks (stalk main and stalk fines).

<p>Summative chemical composition (mass % o.d. material) and monosaccharide composition (molar % of total monosaccharaides) of the enset fibers and stalks (stalk main and stalk fines).</p