H. Koseoglu

Impacts of membrane flux enhancers on activated sludge respiration and nutrient removal in MBRs

This paper presents the findings of experimental investigations regarding the influence of 13 different flux enhancing chemicals (FeCl3, polyaluminium chloride, 2 chitosans, 5 synthetic polymers, 2 starches and 2 activated carbons) on respirometric characteristics and nitrification/denitrification performance of membrane bioreactor (MBR) mixed liquor. Flux enhancing chemicals are a promising method to reduce the detrimental effects of fouling phenomena via the modification of mixed liquor characteristics. However, potentially inhibiting effects of these chemicals on mixed liquor biological activity triggered the biokinetic studies (in jar tests) conducted in this work. The tested polyaluminium chloride (PACl) strongly impacted on nitrification (-16%) and denitrification rate (-43%). The biodegradable nature of chitosan was striking in endogenous and exogenous tests. Considering the relatively high costs of this chemical, an application for wastewater treatment does thus not seem to be advisable. Also, addition of one of the tested activated carbons strongly impacted on the oxygen uptake rate (-28%), nitrification (-90%) and denitrification rate (-43%), due to a decrease of pH. Results show that the changes in kLa values were mostly not significant, however, a decrease of 13% in oxygen transfer was found for sludge treated with PACl.

Effects of chemical additives on filtration and rheological characteristics of MBR sludge.

The main goal of this study was to control the fouling phenomena in MBR using chemical additives. In the first phase of the study, SMP removal and bound EPS formation capacity of chemical additives were determined. Highest SMP removal (72%) was achieved by the Poly-2 additive. In the second phase of the study, short term filtration tests were conducted. Poly-1 exhibited highest performance based on membrane resistance, permeability and average TMP. According to the results obtained from constant shear rate tests in fourth phase, no significant change in viscosity with time was observed. Studies for the adaptation of rheograms to common flow models showed that chitosan and starch was not able to fit to Ostwald de Waele and Bingham models. At a shear rate of 73.4 s(-1) viscosities of all samples were close to each other. Chitosan and starch achieved highest viscosity values at the shear rate of 0.6 s(-1).

Biotemplated Luffa cylindrica for the oil spill clean-up from seawater

AbstractBiotemplated Luffa cylindrica (B-LC) is used to remove oil spills from Mediterranean seawater. The main objective of this work is to develop a biotemplated organic sorbent. L. cylindrica is coated with chitosan for efficient delivery of oil droplets throughout the lumens of fiber. Thus, L. cylindrica acted both as a natural sorbent and a chitosan carrier template. In second step, the optimum conditions for the efficient oil sorption of B-LC are determined. Besides seawater tests, DDI water tests are also performed in order to investigate the effect of background water chemistry. Both modified and raw L. cylindrica samples are studied for the determination of baseline sorption capacity. SEM and Fourier transform infrared spectroscopy analyses are performed for the characterization studies. Results showed that B-LC has a higher sorption capacity compared to the raw samples. It is understood that increasing temperature has an adverse effect on seawater oil sorption value. It is generally noticed that...

Boron Removal in Seawater Desalination by Reverse Osmosis Membranes – the Impacts of Operating Conditions

Production of drinking water through seawater desalination using reverse osmosis (RO) membranes is becoming increasingly attractive especially in coastal areas with limited freshwater sources. However, one challenge in such conventional desalination RO plants is the difficulty of meeting boron standards in product waters. Therefore, most of the current desalination plants employ additional treatment steps including pH adjustment of feedwater, dilution of RO permeate with other sources, ion exchange post-treatment of RO permeate, and/or double-pass staging for permeate. All these further treatment options increase the cost of desalination. Although membrane manufacturers have been developing modified RO membranes with enhanced boron removal capacities such membranes still should be improved from operational flux and pressure perspectives. The main objective of this work was to determine the impacts of operational conditions (membrane pressure, cross-flow velocity and flux) and water chemistry on boron rejections using two commercial RO membranes specified for enhanced boron removal (TorayTM UTC-80-AB and FilmtecTM SW30HR). A lab-scale cross-flow flat-sheet configuration test unit (SEPA CF II, Osmonics) was used for all RO experiments. Seawater samples were collected from the Mediterranean Sea, Alanya-Kizilot shores, south Turkey. For all experiments, mass balance closures were between 91 and 107%, suggesting relatively low loss of boron on membrane surfaces during 14 h of operation. Boron rejections were relatively constant (a maximum change of ±3%) during the 14 h of operation period for all experiments, suggesting that steady state dynamic membrane conditions were immediately achieved within couple hours. Boron rejections obtained with Toray and FilmTec membranes at pH of original seawater (8.2) and at other various operating conditions ranged between 85 and 92%, resulting in permeate boron concentrations of about 0.2–0.9 mg/L. On the other hand, for both membranes, much higher boron removals were achieved at a pH of 10.5 (>98%), resulting in permeate boron concentrations less than 0.1 mg/L. The charged boron species are expected to be dominant at pH values >9.24 (pKa of boric acid) compared to the neutral boric acid. Therefore, as expected, both membranes exhibited higher boron rejections at a pH of 10.5. Salt rejections (as measured by conductivity) were generally 97–99% at both pH values. Boron rejections were independent of feed water boron concentrations up to 6.6 mg/L. For each membrane type, permeate fluxes at constant pressure were generally lower at pH of 10.5. The ranges of permeate fluxes measured in all experimental conditions were 11–15, 13–17 and 19–21 L/m2-h for 600, 700 and 800 psi (41, 48 and 55 bar) pressures, respectively, after an operation period of 14 h. For all experimental conditions, permeate fluxes gradually decreased during the 14 h operation although a leveling off was observed after 12 h. At constant membrane pressure of 800 psi and pH of 8.2, feed flowrate thus the cross-flow velocity (0.9 and 0.5 m/s) did not exert any significant impact on boron rejection.

Water Flux and Reverse Salt Flux

Abstract Following the increase in the world population and the demand for economic development, the need for energy has increased day by day. Rapidly increasing global energy consumption is supplied mainly by fossil fuels bearing the risk of exhaustion with decreasing reserves, which now have the effect of carbon emissions and greenhouse gases. These concerns lead humanity to significantly reduce the use of fossil fuels. Salinity gradient energy (SGP), a type of hydroelectric energy, also has a high potential to displace fossil fuels. SGP is less periodic than sources like wind and solar energy. The osmotic pressure gradient energy uses the released energy during mixing of the water currents with different salinity The Gibbs free energy from mixing two solutions of different concentrations is an unnoticed source of energy. Salinity gradient energy, also referred to as osmotic energy or blue energy, can be derived from natural sources such as clean river water, salt water, and desalination of seawater. Various approaches have been developed to capture salinity gradient energy, but the most promising are pressure-retarded osmosis (PRO), reverse electrodialysis (RED) and forward osmosis (FO) processes. In this chapter theoretical approaches derived from the current literature is presented for the deep conceptual understanding of the water flux and reverse salt flux issues.