Extreme chromium transformation and immobilization via ferrous coupling surfactant-enhanced nanofiltration process

Study on surface water treatment by hybrid sand filtration and nanofiltration

ABSTRACTDespite the great advance in nano-filtration (NF) process development in various applications, its performance in water treatment is still impeded by the undesired fouling phenomenon, which is not yet fully understood nowadays. In this study, a comprehensive investigation on the fouling behavior, more specifically the combined fouling behavior with the presence of more than one type of foulant was carried out under various solution chemistries and feed hydraulic pressures. The interaction between the model organic foulant (alginate) and inorganic foulant (silica colloid) was systematically studied with nano-filtration membranes, with a more severe fouling observed in the combined fouling than individual foulants. However, the results also revealed that the commonly observed synergistic effect of combined fouling in the forward osmosis process was not present in the nano-filtration process. In addition, the solution chemistries (pH and calcium ions) and feed hydraulic pressure were also found to have certain influence on the combined fouling, especially the feed hydraulic pressure which exhibited a more pronounced impact on the flux decline than the other factors, thus in turn, affecting more on the reversibility of the membrane fouling.

BackgroundAs an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran.MethodsThis study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl−1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied.ResultsResults showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91.ConclusionsComparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process.The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na.

Toward real textile wastewater treatment: Membrane fouling control and effective fractionation of dyes/inorganic salts using a hybrid electrocoagulation – Nanofiltration process

Secondary effluent reclamation and reuse has been considered as an alternative for agricultural irrigation water. Whilst all constituents in the reclaimed wastewater could affect plant growth and soil characteristics, the most important parameters for agricultural irrigation are salinity and SAR (Sodium Adsorption Ratio). Salinity affects the availability of crop water and sodium causes clay soils to disperse. Membrane technologies, especially NF (Nano-Filtration) and RO (Reverse Osmosis), have played in a key role reclaiming the secondary effluent. RO can remove monovalent and divalent cations simultaneously. However NF processes reject preferably divalent cations and most monovalent ions are allowed to pass through the NF membranes. This could make them have different SAR values for both NF and RO processes. Therefore the primary objective of this study is to examine if the SAR values of the reclaimed water could be changed while they undergo NF and RO processes. The measured SAR values of the secondary effluent, NF permeate, and RO permeate were 1.78, 4.67, and 0.72 respectively. The SAR value after NF (4.67) increased to more than twice that of the feed solution, whereas the SAR of the RO permeate decreased to 0.72. In general, the higher SAR the water has, the greater risk the soils have. Although the SAR value after NF was within the safe range, this increased SAR value will affect permeability of soil, thus limiting the reclaimed wastewater use for as agricultural irrigation water. Consequently, when the NF system is used for the reclamation of the secondary effluent, SAR has to be examined first because potentially it tends to increase the SAR value.

High recovery rate NF–FO–RO hybrid system for inland brackish water treatment

Hybrid of Adsorption and Nanofiltration Processes as a Capable Removal Method for HANs Removal

Comparative analysis of salt cleaning and osmotic backwash on calcium-bridged organic fouling in nanofiltration process

The influence of membrane fouling on the retention of the trace organic contaminant sulfamethoxazole by a nanofiltration (NF) process was investigated. Organic fouling caused a severe flux decline possibly due to pore blocking and adsorption directly after the commencement of the fouling layer development. Such membrane-foulant interactions were absent for colloidal fouling, which resulted in a more gradual flux decline. Membrane charge played a significant role in the separation process of inorganic salts, where the retention was the highest in a caustic environment (high pH) due to more swollen membrane material caused by the higher negative charge on the membrane. Organic fouling and a combination of colloidal and organic fouling led to a significant increase in the membrane negative charge. The influence of membrane fouling on solute retention was dependent on the fouling behaviour and the physicochemical properties of the model foulants, where the model foulants probably contributed to an increase in the retention of charged solutes due to enhanced electrostatic interactions. Organic fouling caused an increase in the retention of inorganic salts and sulfamethoxazole due to pore blocking. In contrast, colloidal fouling caused a decrease in the retention of inorganic salts due to cake-enhanced concentration polarisation. However, the presence of a colloidal fouling layer did not reduce the retention of sulfamethoxazole. A mixture of colloidal and organic matter improved the retention of inorganic salts. A similar conclusion can be inferred for sulfamethoxazole at pH 4 when the compound exists in a neutral form.

Ceramic nanofiltration and membrane distillation hybrid membrane processes for the purification and recycling of boric acid from simulative radioactive waste water

Advanced treatment of pulp and paper mill wastewater by nanofiltration process: Effects of operating conditions on membrane fouling

Optimization of filtration conditions for CIP wastewater treatment by nanofiltration process using Taguchi approach

The oily wastewater treatment using the nanofiltration process The objective of this work was to investigate the possibility of oily wastewater treatment using the nanofiltration (NF) process. The NF studies were carried out with a permeate obtained from ultrafiltration (UF) (used for the treatment of the oily wastewater from metal industry). The influence of transmembrane pressure on a permeate flux, the degree of the rejection of oil and inorganic compounds was investigated. The studies on the NF treatment of oily wastewater demonstrated a high effectiveness of the rejection of oil and inorganic compounds. The permeate obtained from the treatment was free of oil. Moreover, the retention coefficient of the inorganic compounds was higher than 75% for all the cations examined (Na+, K+, Mg2+, Ca2+, Zn2+, Cu2+) and higher than 95% for sulphates. Therefore, the permeate obtained in the NF process can be reused for fresh emulsion preparation.

Modeling the impacts of feed spacer geometry on reverse osmosis and nanofiltration processes

Modeling of arsenic, chromium and cadmium removal by nanofiltration process using genetic programming