Irena Petrinić

Ultrafiltration of oil-in-water emulsion by using ceramic membrane: Taguchi experimental design approach

In this study, a Taguchi experimental design methodology was used to determine the importance of process parameters influencing the ultrafiltration (UF) of oil-in-water emulsions. Four parameters including pH (5–11), oil concentration (φ) (0.5–3% (v/v)), temperature (T) (25–45°C) and trans-membrane pressure (TMP) (1–5 bar) were studied at three levels. The highest flux was used as optimization criterion. In order to reduce the number of experiments, a Taguchi method was applied. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the optimization criterion.Filtration experiments were performed in a cross-flow operation at a total recycle condition in a laboratory-scale plant. The ceramic UF membrane with a pore size of 50 nm was employed in a tubular module with an active area of 0,418 m2. We used water-soluble cutting oil mixed with water as a model oil-in-water emulsion. During the experiment, the drop size and zeta potential distributions were evaluated.The optimum conditions for UF providing the highest flux were found at TMP = 5 bar, pH = 7, and φ = 0.5 v/v%. The pH of emulsion had the highest impact on COD retention. The results of this study could be used as a guideline for operating UF systems with ceramic membranes at optimal conditions.

Assessing the quality of raw cotton knitted fabrics by their streaming potential coefficients

Raw cotton knitted fabrics of Greek, Indonesian, and Indian origin were investigated through surface characterization before and after processing. Surface modifications of all the knitted cotton fabrics were objectively evaluated through zeta potential measurements within a range of the electrolyte solution pHs, and swelling over time. Streaming potential coefficients of different cotton knitted fabrics were applied in order to establish a correlation between the properties of the raw and treated cotton knitted fabrics of different origins. The rate of swelling was calculated from the streaming potential coefficients of the raw knitted fabrics before and after different treatments. Swelling rate for different origins and different treatments of cotton knitted fabrics and the correlation coefficients were obtained using linear regression. Additionally, a data cluster analysis was performed in order to group different origins of cotton, while all the treatments were sorted according to zeta potential and the rate of swelling coefficients. The obtained results showed differences among the clusters, depending on the origin of the cotton knitted fabrics and treatments they were exposed to.

Decolourisations and biodegradations of model azo dye solutions using a sequence batch reactor, followed by ultrafiltration

The main objective of this study was to investigate the efficiency of biological treatment of azo dye-containing wastewater with a sequencing batch reactor system, followed by ultrafiltration. The performance of the system was quantified by measuring the chemical oxygen demand and azo dye concentration. The biodegradation was carried out under combined alternating anaerobic and aerobic conditions with Nylosan Yellow E2RL SGR as a model azo dye contaminant. The bioprocess revealed a maximal reduction in chemical oxygen demand and dye removal efficiency of 91 and 85%, respectively. After ultrafiltration of effluent from the biological treatment, the efficiency increased to 94% for chemical oxygen demand and to 97% for the azo dye decolourisation. Samples of activated sludge from the bioprocess were collected for microbial characterisation. Bacteria and fungi were isolated and identified by 16S rRNA gene and ITS1-5.8S rDNA-ITS2 sequence analysis, respectively. Serratia marcescens and Klebsiella oxytoca were the most common bacteria with the highest number present during the aerobic and anaerobic phases of the bioprocess. In addition, a high number of Elizabethkingia miricola, Morganella morganii, Comamonas testosteroni, Trichosporon sp. and Galactomyces sp. were detected. Taken together, our results demonstrated that the sequencing batch reactor system combined with ultrafiltration is an efficient technique for treatment of wastewater containing azo dye. Moreover, the ultrafiltration effectively removes the microbiota from the final effluent resulting in stable product water.

17 – Membrane technologies for water treatment and reuse in the textile industry

Textile wastewater is a challenging feed stream for treatment by membrane separation because of its complex composition and the presence of reactive components. Here we briefly present examples of reverse osmosis-, nanofiltration- and ultrafiltration-based systems as well as membrane bioreactor technology for textile wastewater remediation. However, for all of these approaches the general issue of (bio)fouling represents a major obstacle for full-scale industrial implementation. Forward osmosis (FO) membranes have recently attracted considerable interest because the low fouling propensity of FO membranes makes them an intriguing supplement to existing methods. We present the FO principle with some current FO membrane developments including biomimetic aquaporin FO membranes, and exemplify how they can be used to concentrate textile dyes.

Analytical Assessment of the Thermal Decomposition of Cotton-Modacryl Knitted Fabrics

Fabric flammability is affected by various factors such as the fibre composition, fabric construction, FR (flame retardant) finish, oxygen concentration and environmental conditions (moisture content, heat). Inherently FR fabrics are synthetics which have been changed at the molecular level to make the fabrics thermally stable and able to pass FR tests. The thermal properties of knitted fabrics produced from cotton, modacryl and their blends were investigated in this paper. The design of FR knitted fabrics and an optimal blend ratio were evaluated by different thermoanalytical methods: the flame behaviour and thermal stability with the limited oxygen index (LOI), thermal gravimetric analysis (TGA), coupled thermal gravimetry – Fourier transform infrared technique (TG-FTIR) and microscale combustion calorimetry (MCC). Surface characterisation of the knitted fabrics designed was evaluated by the streaming potential method. Knitted fabric in the blend ratio C50:M50 proved to possess the most favourable FR characteristics, additionally confirmed by optimal hydrophilic properties evaluated through zeta potential measurement.

Micropollutant Degradation Mechanism

The organic pollution is a major concern during the treatment of drinking-water as organic micro-pollutants might show disruptive and toxic properties. Organic micro-pollutants are found in surface and groundwaters at different concentrations, mostly between 0,1 and 100 μg/L (Panno&Kelly, 2004). Pesticides are known contaminants of concern. 363 kt of pesticides were used between 1980 and 1990 in the USA. From among triazine pesticides, atrazine and its metabolites, deethylatrazine and deisopropylatrazine, can still be found in drinking-water supplies throughout the EU, due to their usage as maize and sugar beet pesticide. They are slowly biodegradable microbiologically (Reid et al, 2003). They have to be removed from drinkingwater sources because they are classified as possible human carcinogens (Legube et al, 2004). Atrazine, with the chemical name 2-chloro-4-(ethylamino)-6-(isopropylamino)-striazine (C8H14ClN5, MCIET = 215,7 g/mol) is soluble in water at 30 mg/L and half live in soil for atrazine is 15−100 days (Ralebitso et al, 2002). Atrazine is classified as a class C carcinogen. Chromosom damage to chinese hamster egg cells were observed if they were exposed to 0,005−0,080 μmol/L of atrazine, within two days. Two well-known atrazine metabolites, deethylatrazine and deisopropylatrazine, were found to be potentially carcinogenic, therefore the admissible levels for each pesticide individually in water are set at 0,1 ug/L, and the sum should not exceed 0,5 μg/L in EU (Thurman et. al, 1994). US EPA (US Environmental Protection Agency) set the total admissible levels for atrazine, deethylatrazine and deisopropylatrazine in groundwater at 3 μg/L (Richards et al, 1995). A study by US EPA in 2003 showed that triazines – atrazine, simazine and propazine – as well as metabolites – deethylatrazine and deisopropylatrazine in deethyldeisopropylatrazine – have the same mechanism concerning endocrine disruptions. Anumnerated compounds act the same way on human bodies, therefore, US EPA introduced the sum of all chloro−s−triazines. Atrazine removal from drinking water sources is impossible using chlorination, aeration, filtration or coagulation. Quite effective technologies include activated carbon, ozonation, membrane separatoin, and biofiltration. The most efective are RO and NF membranes (Jiang&Adams, 2006). During a study of atrazine degradation within concentrations ranging from 5 to 1700 ng/L, the only metabolite found was deethylatrazine within a concentration range from 10−850 ng/L (Garmouna et al., 1997).