No abstract

In this study, electrooxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effect of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions of EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum condition; pH 9.5, applied current desitiy 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electrooxidation time, the obtained removal efficiencies were 86.5% and 91.1% for COD and ammoniacal nitrogen, respectively. The efficiency was enhanced to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.

BACKGROUND This study used particle size distribution (PSD) to reveal how chemical conditioning inflicted changes on different chemical oxygen demand (COD) size fractions to improve the potential of two‐phase membrane separation as an effective preliminary step for the sustainable management of olive processing wastewaters. RESULTS Experiments were designed to explore: (i) the potential of membrane separation as a pretreatment step; and (ii) the way in which chemical conditioning improved the removal potential of membrane treatment. Particle size distribution analysis was conducted to observe changes inflicted on different COD size fractions by chemical conditioning. The chemically enhanced membrane process achieved 95% COD removal, reducing the effluent COD to 6000–8000 mg L−1 range and the total phenol down to 100 mg L−1. Chemical conditioning also removed a significant portion of soluble COD, so that the resulting PSD fingerprint in the effluent was properly reshaped to allow effective removal by membrane treatment. CONCLUSION The investigated treatment schemes involving pretreatment of oil wastewater by chemical conditioning together with membrane filtration offered high COD reduction in the effluent and biodegradable permeate when properly diluted for co‐treatment with a compatible wastewater stream. The use of chemical conditioning prior to membrane filtration improved final permeate quality and ultrafiltration membrane flux. © 2016 Society of Chemical Industry

In the following study, two methods were employed in which olive mill wastewaters were treated by using reverse osmosis membranes (BW30 and XLE). In the first, wastewater was centrifuged and then passed through the reverse osmosis whereas in the second, an ultrafiltration was placed between the centrifuge and the reverse osmosis. The reverse osmosis experiments were conducted under 10, 15, 20, and 25 bar. The chemical oxygen demand (COD) removal efficiencies under 25 bar were found to be 97.5% for both BW30 and XLE membranes. The highest conductivity removal rates obtained under 25 bar for BW30 and XLE membranes were found to be 95.6 and 96.2%, respectively. As for the highest permeation flux values obtained under 25 bar, they were separately determined for BW30 and XLE as 15.3 and 21.2 L m−2 h−1, respectively. The performances of the membranes were also evaluated in terms of their mass transfer coefficients. According to this, all mass transfer coefficients were found to be <1 and also in proximate to one another; this clearly reflects the results as COD and conductivity removals were approximate and there was a lack of any significant difference, whether ultrafiltration was applied or not.

An autopsy of spiral wound RO membrane operated in brackish water treatment was conducted to understand the origin and extent of foulants and fouling mechanisms. Structural and chemical characterization was determined by visual inspection and instrumental analysis such as SEM-EDS and XRD. It was observed that the membrane surfaces were completely covered with a gray/brown pollutant layer in all membrane sheets. SEM images proved accumulation of mineral pollutants on membrane surface. Also, the high levels of Al and Si which was attributed to aluminum silicates originating from feed water were determined on membrane surfaces. Additionally, the XRD analysis results showed that the foulant sample collected from membrane surfaces include halloysite, SiO2 and LiCl components. Fujiwara result proved that no damage was occurred on the membrane surface due to oxidation. Consequently, a fouling control strategy for RO-based brackish water treatment plants was also recommended to increase the membrane life.