Total Organic Carbon Rejection Research Articles

Synergistic effects of PVDF membrane surface functionalization with polydopamine and titanium dioxide for enhanced oil/water separation and photocatalytic behavior

This study investigates the surface modification of poly(vinylidene fluoride) (PVDF) membranes using polydopamine (PDA) and titanium dioxide (TiO2) for effective separation of oily compounds and self-cleaning photocatalytic behavior. The aim was to improve the antifouling properties of the membrane, which was modified by varied PDA and TiO2 concentrations and evaluated regarding the water permeance, total organic carbon (TOC) rejection, and photocatalytic degradation activity. The results demonstrated considerable improvements in the membrane's antifouling properties, achieving a water permeance of 781 kg h−1 bar−1 m−2, TOC rejection of 87%, and methylene blue photocatalytic degradation of 97%, using dopamine (DA) and TiO2 concentration of 0.92 g L−1 and 1.4% (w/w), respectively, and a solution agitation speed of 106 rpm. Additionally, flux recovery reached 86% after the photocatalytic self-cleaning process, indicating that TiO2 improved the membrane's antifouling properties. These findings highlight the potential of PDA and TiO2 as effective surface modifiers for enhancing oil/water separation, reducing fouling, and promoting self-cleaning effect in photocatalytic PVDF membranes. This study’s outcomes provide valuable insights for developing efficient and sustainable membrane-based separation processes for oily wastewater treatment applications.

Integrating reverse osmosis and forward osmosis (RO-FO) for printing and dyeing wastewater treatment: impact of FO on water recovery.

Reverse osmosis (RO) alone has low water recovery efficiency because of membrane fouling and limited operating pressure. In this study, a combined reverse osmosis-forward osmosis (RO-FO) process was used for the first time to improve the water recovery efficiency of secondary effluent in printing and dyeing wastewater. The effects of operating pressure and pH on water recovery and removal efficiency of RO-FO were investigated. The results showed that the optimum conditions were an operating pressure of 1.5 MPa and a feed solution pH of 9.0. Under optimal operating conditions, most of the organic and inorganic substances in the wastewater can be removed, and the rejection of total organic carbon (TOC), Sb, Ca, and K were 98.7, 99.3, 97.0, and 92.7%, respectively. Fluorescence excitation-emission matrices coupled with parallel factor (EEM-PARAFAC) analysis indicated that two components (tryptophan and tyrosine) in the influent were effectively rejected by the hybrid process. The maximum water recovery (Rw, max) could reach 95%, which was higher than the current single RO process (75%). This research provided a feasible strategy to effectively recover water from printing and dyeing wastewater.

Kappa carrageenan-vanillin composite hydrogel for landfill leachate wastewater treatment

Removing heavy metals from landfill leachate wastewater treatment is an environmental challenge because of its complicated characteristics and composition. Although several chemical and physical processes were developed for landfill wastewater treatment, membrane technologies are still common. Nevertheless, membrane fouling, energy requirements and brine management are drawbacks of membrane technologies. This study proposed a biodegradable, gravity-driven kappa-Carrageenan-vanillin hydrogel for biologically treated leachate wastewater treatment to reduce the treatment cost and brine management problem. The composite hydrogel was synthesized using a facile method, with an average pore size of 2.58 ± 0.5 nm and acts as a water filter with super high flux and excellent rejection for heavy metal ions, divalent ions and other contaminants in the landfill leachate wastewater. The hydrogel filter achieved high rejection for divalent ions from salt feed solutions such as sodium chloride, magnesium sulphate, and copper sulphate. An average rejection of 42 ± 5 % was achieved for sodium chloride, 78 % ± 5 % for copper, 72 % ± 5 % for divalent magnesium ion, and 17 % ± 5 % for sulphate rejection. The hydrogel filter achieved a flux of 27 ± 5 LMH for landfill leachate wastewater with high rejection efficiency for total organic carbon, turbidity, and heavy metal separation. The filtration of the landfill leachate with the hydrogel resulted in a high rejection of total organic carbon (77 ± 3 %), 95 ± 3 % turbidity removal, 73 ± 5 % TDS removal, and 95–97 % colour removal. Heavy metal ions were rejected in the following order: Al (80 ± 3 %) > Ba (88 ± 2 %) > Pb (79 ± 3 %) > Cd (72 ± 3 %). The composite hydrogel filter is inexpensive, reliable, and highly efficient in removing contaminants under gravity filtration, requiring no external energy or high hydraulic pressures and ease of scalability for commercial applications.

Effect of Surfactants on Reverse Osmosis Membrane Performance

The aim of this study was to evaluate the performance of a reverse osmosis (RO) membrane in surfactant removal using various surfactant model aqueous solutions. The separation tests were performed with laboratory scale units in a dead-end configuration. Cellulose Acetate (CA) and Polyamide (PA) RO membranes were used with nonionic, anionic, or cationic surfactants at a wide range of concentrations. Membrane performance was evaluated using permeate flux and total organic carbon (TOC) rejection. The effects of surfactant type and concentration on RO membranes were assessed. Permeate flux of the PA membrane depended on the surfactant type and concentration. The separation of cationic surfactant aqueous solutions yielded the lowest permeate flux, followed by nonionic and anionic surfactant aqueous solutions, respectively. Surfactant adsorption on the membrane surface occurred at very low concentration of cationic and nonionic surfactants due to electrostatic and hydrophobic interactions, respectively, which affected permeate flux, and micelles did not affect the permeate flux of PA membrane. However, for CA membrane the permeate flux was not affected by the feed solution. Both membranes exhibited satisfactory TOC rejection (92–99%). This study highlights the importance of assessing interactions between membrane material and surfactant molecules to mitigate membrane fouling and guarantee a better performance of the RO membrane.

Fluoroalkylsilane grafted FeOOH nanorods impregnated PVDF-co-HFP membranes with enhanced wetting and fouling resistance for direct contact membrane distillation

Direct contact membrane distillation (DCMD) is a versatile thermal-driven membrane separation technique that can be used for seawater distillation and water recovery. Initially, the central composite design was used to optimize the concentration/molecular weight of pore former and operating feed/permeate flow rates. Further, a dual modification strategy was used to fabricate robust hydrophobic polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) membranes- (i) incorporation of fluoroalkylsilane (FAS) grafted FeOOH nanorods (F-g-FeOOH) into the membrane and (ii) surface coating of the membrane with FAS. The membrane with 0.015 wt% FeOOH nanorods (M2) displayed the highest water contact angle (132 ± 1.6ᵒ) with more than 99.98% salt rejection for 10,000 ppm NaCl solution (ΔT= 60 ℃ & feed/permeate flow rate = 20 L/h). The M2 membrane exhibited stable performance, and no pore wetting could be observed even when the feed contained polyhydric alcohol (5 wt% propylene glycol) or surfactant (80 ppm sodium dodecyl sulfate). The M2 membrane also displayed a stable permeate flux of 3.5 L/m2h and a total organic carbon rejection > 96% for up to 12 h for a saline feed (10,000 ppm NaCl) containing hexadecane/water emulsion (100 ppm oil). The prepared membranes were also determined to be suitable for long-term seawater desalination and exhibited a stable permeate flux of 10 L/m2h for 60 h with permeate conductivity < 5 µS/cm. The facile fabrication strategy holds the potential to be further explored to prepare membranes with excellent anti-wetting and anti-fouling properties.

Evaluation of the advanced oxidation process integrated with microfiltration for reverse osmosis to treat semiconductor wastewater

This study evaluated the filtration performance and energy consumption of three different reverse osmosis (RO) membranes (ESPA2-LD, RE4040-BE, and TMG10D) for treating semiconductor wastewater. A ceramic membrane combined with ozone for RO pre-treatment and the influence of ozone injection on the filtration and energy consumption efficiency of RO were investigated. A flat-sheet ceramic membrane comprising Al2O3/SiO2-ZrO2 was used to treat real and synthetic semiconductor wastewater as feed water. The deionized water (DI) permeabilities of RO membranes were 144.6, 94.22, and 156.6 LMH/bar, respectively. The microfiltration process that used ozone reduced the permeability of all RO processes, and the total organic carbon (TOC) removal rate decreased when ozone was applied. The application of ozone on power consumption was inconclusive, and its effect was unclear indicating an increase 3.37%, 4.48%, and 11.6% when filtrated with ozone, respectively. TMG10D showed the highest permeability followed by ESPA2-LD and RE4040-BE, for both, the real and synthetic wastewaters. However, ESPA2-LD showed the highest salt and TOC rejection followed by RE4040-BE and TMG10D. TMG10D exhibited the lowest energy consumption per ton of filtered water followed by ESPA2-LD and RE4040-BE. ESPA2-LD was determined to be the most suitable membrane in terms of the water quality stability and energy consumption in RO to treat semiconductor wastewater.

Feasibility of Treatment of Refinery Wastewater by a Pilot Scale MF/UF and UF/RO System for Reuse at Boilers and Cooling Towers

A pilot-scale hybrid membrane system, consisting of a ceramic microfilter (MF), two differentpolyvinyl chloride (PVC) and polyacrylonitrile (PAN) ultrafilters (UF), and a polyamide reverse osmosis (RO) filter, has been utilized to decrease harmful and damaging components in wastewater produced from Tehran Refinery with aim to be reused at boilers and cooling towers. Taguchi method was employed to find optimum operating conditions including transmembrane pressure, cross flow velocity (CFV), temperature, and backwash time. Further, analysis of variance (ANOVA) was performed to determine the significance of controlling factors on total organic carbon rejection and normalized permeate flux. MF (ceramic)/UF (PVC) system reduced, %: oil 99.7; chemical oxygen demand (COD) 82; biochemical oxygen demand (BOD) 79.3; conductivity 60.5; total dissolved solids (TDS) 52.6; turbidity 99.7 and total hardness 73.2. MF(ceramic)/UF (PAN) system reduced: oil, COD, BOD, conductivity, TDS, turbidity, and total hardness by 99.8; 84.2; 80.8; 62.72; 55; 99.9 and 78.4%, respectively. UF (PAN)/RO system decreased, %: oil 99.5; COD 99; BOD 99; conductivity 98; TDS 98; turbidity 98.7 and total hardness 99.94. Obtained treated wastewater by this system can be reused as feed water of boilers.

Oily wastewater treatment by adsorption-membrane filtration hybrid process using powdered activated carbon, natural zeolite powder and low cost ceramic membranes.

In this research, four types of low cost and high performance ceramic microfiltration (MF) membranes have been employed in an in-line adsorption-MF process for oily wastewater treatment. Mullite, mullite-alumina, mullite-alumina-zeolite and mullite-zeolite membranes were fabricated as ceramic MF membranes by low cost kaolin clay, natural zeolite and α-alumina powder. Powdered activated carbon (PAC) and natural zeolite powder in concentrations of 100-800 mg L-1 were used as adsorbent agent in the in-line adsorption-MF process. Performance of the hybrid adsorption-MF process for each concentration of PAC and natural zeolite powder was investigated by comparing quantity of permeation flux (PF) and total organic carbon (TOC) rejection during oily wastewater treatment. Results showed that by application of 400 mg L-1 PAC in the adsorption-MF process with mullite and mullite-alumina membranes, TOC rejection was enhanced up to 99.5% in comparison to the MF only process. An increasing trend was observed in PF by application of 100-800 mg L-1 PAC. Also, results demonstrated that the adsorption-MF process with natural zeolite powder has higher performance in comparison to the MF process for all membranes except mullite-alumina membranes in terms of PF. In fact, significant enhancement of PF and TOC rejection up to 99.9% were achieved by employing natural zeolite powder in the in-line adsorption-MF hybrid process.

Sequential Use of UV/H2O2—(PSF/TiO2/MWCNT) Mixed Matrix Membranes for Dye Removal in Water Purification: Membrane Permeation, Fouling, Rejection, and Decolorization

Abstract Performance of a hybrid ultraviolet/hydrogen peroxide (UV/H2O2)–mixed matrix membrane system for an azo dye, acid black 1 [AB1], removal in a water purification process was studied. Different mixed matrix membranes embedded with titanium dioxide (TiO2) nanoparticles, multi-walled carbon nanotubes (MWCNTs), and a mixture of them were fabricated by the phase inversion method. Mixed matrix membranes embedded with MWCNTs resulted in higher pure water flux, and mixed matrix membranes embedded with TiO2 showed lower flux declines in the presence of AB1. However, all the membranes exhibited very low total organic carbon (TOC) rejection and none of the mixed matrix membranes could decolorize the AB1 solution. UV/H2O2 pretreatment of the AB1 solution resulted in enhanced TOC rejection, decolorization, and enhanced antifouling membrane behavior. Combining UV/H2O2 with each type of polysulfone (PSF) mixed matrix membranes (PSF/TiO2, PSF/MWCNT, and PSF/TiO2/MWCNT) resulted in optimal performance in terms of ...

Highly condensed polyvinyl chloride latex production by forward osmosis: Performance and characteristics

Forward osmosis (FO) has attracted attention in industry because of its low energy consumption and low fouling tendency. In this paper, the condensation of polyvinyl chloride (PVC) latex with FO as a pretreatment step prior to the final drying process was investigated. The effect of agitation speed, FO membrane type, and the NaCl concentration of the draw solution (DS) were evaluated. For the membrane performance, the water flux, NaCl flux, and total organic carbon (TOC) flux were evaluated. When the feed solution was sufficiently agitated, a PVC concentration of 75wt% was achieved using model seawater as the DS. FO performance was experimentally compared with reverse osmosis (RO) performance using similar apparatus and the same water flux conditions. The TOC rejection in FO was higher than that in RO. Latex condensation using FO was characterized by a decrease in outlet water flux by cake-enhanced osmotic pressure, a decrease in inlet water flux by the capillary force resistance in the cake layer, and an increase in TOC rejection by the retarded forward diffusion of solutes. The control of cake-layer formation was important for the condensation of PVC latex by FO.

Membrane Treatment of Secondary Effluent for Subsequent Use

Granular-media filtered secondary effluent from a full-scale plant was subsequently treated at pilot-plant scale by combinations of low- and high pressure membranes. The feedwater was split between microfiltration (MF) and ultrafiltration (UF) treatment trains; ferric chloride (4 mg/L) was added to the UF feedwater. Filtrate from each of these trains became the feedwater to three different types of high-pressure membranes operating in parallel, two reverse osmosis (RO) units and one nanofiltration (NF) unit; no chemicals (e.g., chlorine) were added ahead of the high-pressure membranes to control biofouling.Both the low- and high pressure membrane systems were operated at constant flux such that fouling was measured by an increase in transmembrane pressure (TMP). Membrane selectivity was measured by the rejection of total organic carbon (TOC), selected inorganic parameters, particle counts, turbidity and a virus challenge study. Specific flux was higher and the average TMP was lower for the UF system than for the MF system.The fouling rate of three types of high-pressure membranes, as measured by the initial specific flux after cleaning and by the subsequent decline in specific flux, was lower for those receiving pretreatment by UF than by MF. The choice of membrane pretreatment did not affect rejection efficiency of any of the three high-pressure membranes.This title belongs to WERF Research Report SeriesISBN: 9781843397595 (eBook)

THM precursor rejection by UF membranes treating Scottish surface waters

Trihalomethanes (THMs) are known to be generated from specific fractions of natural organic matter (NOM) present in surface waters used for potable water supply. The overall specific THM formation propensity (THMFP) can be expressed in terms of yield – the mass of THM generated per unit mass of permeate total organic carbon (TOC).A study of permeate water quality, with specific reference to TOC rejection and THM yield, has been conducted for membrane-based potable water supply plants across Scotland. The study encompassed 35 operating plants fitted with “tight” UF membranes, and was based on 18months of water quality (WQ) data. Literature data used to calculate yield for comparable pilot or full scale membrane plants challenged with various real waters and operating under similar conditions indicate permeate THM yields predominantly in the range of 20–50μg total THMs (tTHMs) per mg TOC across a range of membrane characteristics.Outcomes from the study revealed average yields within the range of 10–70μg THMs/mg TOC, with TOC passage averaging 18%, roughly in keeping with published values for comparably selective membranes. Data for THM distribution revealed that, counter-intuitively, increased bromine substitution lead to slightly reduced total THM levels.

Fabrication of a high-flux thin film composite hollow fiber nanofiltration membrane for wastewater treatment

A high-flux thin film composite (TFC) hollow fiber nanofiltration (NF) membrane was fabricated using a barrier layer of polypiperazine amide synthesized via interfacial polymerization (IP) on a previously prepared dual-layer (PES/PVDF) hollow fiber substrate, which was synthesized via the two-step TIPS/NIPS method. The permeability of the TFC membrane was smaller by an order of magnitude than that of the substrate, which was due to the formation of a thick barrier layer. The structure of the barrier layer was controlled via the addition of cyclic ethers (dioxane, oxolane and trioxane). By increasing the polarity of cyclic ethers, the thickness of the barrier layer and the dense layer was reduced due to the piperazine concentration in the organic phase. Comparing with oxolane and trioxane, the addition of dioxane resulted in a narrower pore size as that of the conventional IP process, which was ascribed to the narrow IP reaction zone via the immiscibility of interface. With the addition of dioxane up to 2wt%, the barrier layer became thinner, the pure water flux of the resultant membrane was improved and the dextran rejection was maintained. The novel hollow fiber NF membrane has a permeability of 16.6Lm−2h−1bar−1, a MWCO of 330Da and a tensile strength of 10.3MPa. This membrane had a higher rejection of total organic carbon and a lower rejection of total dissolved solids of the secondary effluent from a petrochemical industry plant, which proves the potential of this membrane in municipal, agricultural and industrial wastewater treatment.

Dynamic cross-flow filtration of oilfield produced water by rotating ceramic filter discs

Abstract The purpose of this research paper is to assess the effects of the process parameters—membrane rotational speed (1,200, 1,500 and 1,800 rpm), volume concentration factor (VCF) and feed characteristics—in terms of oil and total organic carbon (TOC) separation capability, permeability and permeate quality. For this, a series of membrane filtration experiments were carried out systematically using rotating ceramic filter discs in a fed-batch operating mode. The variation of membrane rotational speed was found to minimize the membrane fouling in a significant amount. High oil (>99%) and TOC rejection (>98%) was achieved with both microfiltration (MF) and ultrafiltration (UF) membranes, independent of the rotational speed and the feed concentration The experimental results are presented for the dynamic cross-flow MF (0.2-μm pores) and UF (7-nm pores) of oilfield produced water as well as oily model solutions (OMS).

The performance of polyamide nanofiltration membrane for long-term operation in an integrated membrane seawater pretreatment system

An ultrafiltration–nanofiltration (UF–NF) integrated membrane system (IMS) was operated for 500h to examine the performance of the NF membrane in seawater desalination pretreatment. The rejection of divalent ions, TDS, TOC and UV254 by the NF membrane as well as the permeation flux decreased gradually with operating time before each chemical cleaning procedure, while the calculated Stiff and Davis Stability Index (S&DSI) increased gradually from negative up to positive. The result indicates that there exists inorganic fouling during the long run. However, the IMS produced excellent effluent with 93.6% removal of total organic carbon (TOC) for long-term operation. The TOC concentration of the NF permeation samples was in the range of 0.06–0.35mg/L. The chemical cleaning results indicated that inorganic fouling should be preferentially paid attention to, and a combination of citric acid cleaning and NaOH cleaning may achieve an optimal cleaning efficiency. The long-term operation reveals that the membrane is more prone to fouling gradually after chemical cleaning.

Oily wastewater treatment using mullite ceramic membrane

Abstract This paper presents performance of a microfiltration (MF) ceramic membrane for treatment of oily wastewaters. Mullite MF membranes were synthesized from kaolin clay. The effects of different operating parameters such as pressure (0.5–4 bar), volumetric flow rate (0–2 m/s), temperature (15–55°C), oil concentration (250–3000 ppm) and salt concentration(0–200 g/l) on permeate flux (PF), fouling resistance (FR), fouling and rejection (R) were investigated. In order to determine the best operating conditions, 250–3000 ppm condensate gas in water emulsions were employed as synthetic feed. The rejection of total organic carbon (TOC) for the synthetic feeds was found to be more than 94%. The results show that by increasing temperature and pressure, the PF increases. Also, by increasing oil content and salt concentration, the membrane is fouled rapidly and the PF decreases. At low salt concentration (0–25 g/l), PF increases with increasing salt concentration, but at high salt concentration (25–200 g/l), it decreases with increasing salt concentration. Increasing volumetric flow rate causes PF to increase and FR reduce.

Oily wastewater treatment using mullite ceramic membrane

Abstract This paper presents performance of a microfiltration (MF) ceramic membrane for treatment of oily wastewaters. Mullite MF membranes were synthesized from kaolin clay. The effects of different operating parameters such as pressure (0.5–4 bar), volumetric flow rate (0–2 m/s), temperature (15–55°C), oil concentration (250–3000 ppm) and salt concentration(0–200 g/l) on permeate flux (PF), fouling resistance (FR), fouling and rejection (R) were investigated. In order to determine the best operating conditions, 250–3000 ppm condensate gas in water emulsions were employed as synthetic feed. The rejection of total organic carbon (TOC) for the synthetic feeds was found to be more than 94%. The results show that by increasing temperature and pressure, the PF increases. Also, by increasing oil content and salt concentration, the membrane is fouled rapidly and the PF decreases. At low salt concentration (0–25 g/l), PF increases with increasing salt concentration, but at high salt concentration (25–200 g/l), i...

MODELING OF MEMBRANE FOULING AND FLUX DECLINE IN MICROFILTRATION OF OILY WASTEWATER USING CERAMIC MEMBRANES

One of the major problems in pressure-driven membrane processes is reduction of flux far below the theoretical capacity of the membrane. The results of an experimental study of fouling mechanisms of ceramic membranes in separation of oil from synthesized oily wastewaters are presented. Mullite microfiltration (MF) membranes were synthesized from kaolin clay as MF ceramic membranes. The rejection of total organic carbon (TOC) for the synthetic feeds was found to be more than 94% by these membranes. Hermia's models were used to investigate the fouling mechanisms of membranes. The effect of pressure, cross flow velocity (CFV), temperature, oil concentration, and salt concentration on flux decline were investigated. The results showed that the cake filtration model can well predict the flux decline of mullite ceramic membranes; average error of this model is less than 7%. The results show that by increasing pressure from 0.5 to 4 bar, porosity of the cake layer on the mullite membranes decreases from 25.68% to 14.98%. After the cake filtration model, the intermediate pore blocking model was found to well predict the experimental data with an average error less than 10.5%.

Enhancement of Oily Wastewater Treatment by Ceramic Microfiltration Membranes using Powder Activated Carbon

AbstractResults of a hybrid microfiltration‐powdered activated carbon (MF‐PAC) system for the treatment of synthetic oily wastewaters with mullite and mullite‐alumina (50 % alumina content) ceramic membranes are presented. The experiments were conducted to determine the effects of the presence of PAC on MF process performance in terms of flux decline, membrane fouling, and total organic carbon (TOC) rejection. The experimental results demonstrate that PAC addition at low concentration (200–400 ppm) increases permeate flux by 19.6 % for mullite and 61 % for mullite‐alumina MF membranes. However, high PAC concentration (1200 ppm) decreases the permeate flux by 22 % for mullite and 25 % for mullite‐alumina MF membranes. Also, TOC rejection increases from 93.8 to 97.4 % for mullite and from 89.6 to 92.4 % for mullite‐alumina MF membranes.

Oily wastewater treatment by ultrafiltration using Taguchi experimental design

In this research, results of an experimental investigation on separation of oil from a real oily wastewater using an ultrafiltration (UF) polymeric membrane are presented. In order to enhance the performance of UF in API separator effluent treatment and to get more permeation flux (PF), effects of operating factors on the yield of PF were studied. Five factors at four levels were investigated: trans-membrane pressure (TMP), temperature (T), cross flow velocity (CFV), pH and salt concentration (SC). Taguchi method (L(16) orthogonal array (OA)) was used. Analysis of variance (ANOVA) was applied to calculate sum of square, variance, error variance and contribution percentage of each factor on response. The optimal levels thus determined for the four influential factors were: TMP, 3 bar; T, 40˚C; CFV, 1.0 m/s; SC, 25 g/L and pH, 8. The results showed that CFV and SC are the most and the least effective factors on PF, respectively. Increasing CFV, TMP, T and pH caused the better performance of UF membrane process due to enhancement of driving force and fouling residence. Also, effects of oil concentration (OC) in the wastewater on PF and total organic carbon (TOC) rejection were investigated. Finally, the highest TOC rejection was found to be 85%.