Jaeweon Cho

Nanofiltration for water and wastewater treatment – a mini review

Abstract. The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals, mechanisms, fouling challenges and their controls.

A pilot-scale hybrid municipal wastewater reclamation system using combined coagulation and disk filtration, ultrafiltration, and reverse osmosis: removal of nutrients and micropollutants, and characterization of membrane foulants.

A pilot-scale municipal wastewater reclamation system using combined coagulation and disk filtration (CC-DF), ultrafiltration (UF), and reverse osmosis (RO) membrane has been built to investigate removal of water contaminants and fouling mitigation. The reclaimed water using the pilot system could meet draft regulations on wastewater reuse of the California Department of Public Health (DOC: 0.5 mgC/L; TN: 5 mgN/L). The removal of micropolluants by the CC-DF process and UF could not be evaluated by their MW, Log D, and charge characteristics. However, they were identified as governing factors affecting the removal of micropollutants by the RO. The CC-DF process might effectively remove particulate materials capable of contributing to cake layer formation on the UF membrane surfaces but the residual coagulants provided a strong effect on fouling formation of the UF membrane. Thus, hydrophobic fractions of the desorbed UF membrane foulants were higher than those of the desorbed RO membrane foulants.

Application of nanofiltration pretreatment to remove divalent ions for economical seawater reverse osmosis desalination

AbstractTo minimize scale formation potential in the applications of reverse osmosis (RO) membranes as a pretreatment unit, relatively loose nanofiltration (NF) membrane systems coupled with ultrafiltration (UF) were used to remove divalent ions from seawater. However, the UF did not reject any ions because of pore size. The rejection of divalent ions by NF was in order of sulfate (>95%), magnesium (>60%), and calcium (>30%) in every rejection experiment based on water recovery rate (40, 50, 60, 70, and 80%). In the UF/NF/RO hybrid pilot system, most of the divalent (>99%) and the monovalent (>97%) ions were effectively rejected with slightly increased divalent ion rejection compared to the UF/RO system. Seawater temperature influenced rejection of ions with regards to either the diffusion- or convection-dominant transport of ions through the membrane pores. Electric power consumption was also compared between the UF/NF/RO process and the UF/RO process. For different salinity conditions (28,000 and 45,000...

Role of wetland organic matters as photosensitizer for degradation of micropollutants and metabolites

Overall photodegradation of pharmaceuticals, personal care products (PPCPs) and pharmaceutical metabolites were investigated in order to evaluate their photochemical fate in aquatic environments in various natural organic matter (NOM) enriched solutions. Tested PPCPs exhibited different rates of loss during direct and indirect photolysis. Here, only ultraviolet (UV) light source was used for direct photolysis and UV together with (3)DOM(*)for indirect photolysis. Diclofenac and sulfamethoxazole were susceptible to photodegradation, whereas carbamazepine, caffeine, paraxanthine and tri(2-chloroethyl) phosphate (TCEP) showed low levels of photodegradation rate, reflecting their conservative photoreactivity. During indirect photodegradation, in contrast to the hydrophilic autochthonous NOM, allochthonous NOM with relatively high molecular weight (MW), specific ultraviolet absorbance (SUVA) and hydrophobicity (e.g., Suwannee River humic acid (SRHA)) revealed to significantly inhibit the photolysis of target micropollutants. The presence of Typha wetland NOM enhanced the indirect photolysis of well-known conservative micopollutants (carbamazepine and paraxanthine). And atenolol, carbamazepine, glimepiride, and N-acetyl-sulfamethoxazole were found to be sensitive to the triplet excited state of dissolved organic matter ((3)DOM(*)) with Typha wetland NOM under deoxygenated condition. This suggests that photolysis in constructed wetlands connected to the wastewater treatment plant can enhance the degradation of some anthropogenic micropollutants by the interaction with (3)DOM(*) in wetlands.

The role of a combined coagulation and disk filtration process as a pre-treatment to microfiltration and reverse osmosis membranes in a municipal wastewater pilot plant

A pilot study was conducted to assess the performance of a municipal wastewater reclamation plant consisting of a combined coagulation-disk filtration (CC-DF) process, microfiltration (MF) and reverse osmosis (RO) membranes, in terms of the removal of water contaminants and changes in characteristics of effluent organic matter (EfOM). The CC-DF and MF membranes were not effective for the removal of dissolved water contaminants. However, they could partially reduce the turbidity associated with the cake layer formation by particulate materials on the membrane surfaces. Furthermore, most of water contaminants were completely removed by the RO membranes. Although the CC-DF process could remove approximately 20% of turbidity, the aluminium concentrations considerably increased after the CC-DF process due to the residual coagulants complexed with both carboxylic acid and alcohol functional groups of EfOM. Those aluminium-EfOM complexes had a lower negative charge and higher molecular weight (>0.1 μm pore size of the MF membranes) compared to non-complexed EfOM. These results indicate that the control of the formation of the aluminium-EfOM complexes should be considered as a key step to use the CC-DF process as a pre-treatment of the MF and RO membranes for mitigation of membrane fouling in the tested pilot plant.

Removal of N-nitrosamines in a membrane bioreactor and nanofiltration hybrid system for municipal wastewater reclamation: Process efficiency and mechanisms

This study investigated the removal efficiency and mechanisms of water contaminants (mainly N-nitrosamines) during municipal wastewater reclamation by a membrane bioreactor (MBR) and nanofiltration (NF) hybrid system. The removal of bulk water contaminants was governed by the microbial activities in the MBR and molecular weight cut-off (MWCO) of the NF membranes. The removal of N-nitrosamines by the MBR was primarily attributed to biodegradation by aerobic bacteria, which can be determined by the reactivity of the amine functional groups with the catabolic enzymes (removal efficiency=45-84%). Adsorption and formation of membrane fouling can enhance the removal of N-nitrosamines by the NF membranes. However, size-exclusion is found to play a major role in the removal of N-nitrosamines by the NF membranes since the removal efficiencies of N-nitrosamines varied significantly depending on molecular weight of the N-nitrosamines and MWCO of the NF membranes (removal efficiency: NE90>NE70).

Science Walden: new horizons of combined ecological sanitation with separated urine/feces and treatment wetlands

AbstractA new engineering concept, designed with separated urine/feces and graywater recovery, was proposed, and the first steps in taking this concept from the planning stage to implementation have been taken using pilot experiments within a small village. The village employs ecological toilet, equipped with 24u2009h ventilation, and constructed treatment wetlands consisting of both vertical and horizontal subsurface wetlands for graywater recovery. The quality of recovered graywater was similar to that of the water found in the adjacent stream, which is a concept of zero discharge system with graywater. Separated urine, in either fresh or stored form, was diluted with collected rainwater and with reused water without any detergent from a sink, to be supplied to vegetable garden as fertilizer. Separated dried feces were composted in the garden for approximately 3u2009months and then used as fertilizer. Dried and composted feces, together with stored urine, were characterized in terms of microbial community using...

Humification of effluent organic matters through a surface-flow constructed wetland.

Dominant fractions of wastewater effluent organic matter (EfOM) were changed from polysaccharides (PS) to polyhydroxyaromatics (PHA), throughout the constructed treatment wetland connected to a wastewater treatment plant, as measured using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The changes in the fractions were also identified, with respect to molecular weight (MW) distributions of the effluent organic matters, as measured using high performance size exclusion chromatography equipped with both UV and fluorescence detectors, for aromatic/hydrophobic and protein-like organic substances, respectively; organic matter, with MWs of approximately 2,500 and 20,000 Da, and approximately 38,000 Da, as measured by the UV and fluorescence detectors, respectively, were newly formed after the wetlands, especially for the samples of the Typha wetland in June and August against in December. Thus, with the above two different analyses, the humification type of transformation of EfOM through the treatment wetland, was believed to occur, probably due to biological transformation (from the comparison of results in June and August with those in December). It was anticipated that the humification of EfOM could reduce biodegradable organic portions of wastewater effluents even though total organic carbon levels were not reduced that much after the treatment wetland.

Sorption of pharmaceuticals to soil organic matter in a constructed wetland by electrostatic interaction

There is a growing interest in the removal of pharmaceuticals from wastewater because pharmaceuticals have potential ecotoxicological effects. Among several removal mechanisms, the sorption of pharmaceuticals to sediment organic matter is an important mechanism related to the mobility of pharmaceuticals. This study investigated the sorption of pharmaceuticals to soil organic matter (SOM) by electrostatic interactions. SOM located on the surface of soil/sediment generally has a negative charge because of the functional groups present (i.e., carboxylic and phenolic groups). Thus, the electrical characteristics of SOM can induce electrical attraction with positively charged chemical compounds. In this study, SOM was extracted from soils under different aquatic plants (Acorus and Typha) in a constructed wetland in Korea. Experiments were carried out with the following three pharmaceuticals with different electrical characteristics at pHu202f7: atenolol (positive charge; pKa 9.5), carbamazepine (neutral; no pKa), and ibuprofen (negative charge; pKa 4.9). The SOM in the Acorus pond had a higher hydrophobicity and electrical charge density than that in the Typha pond. Regarding the sorption efficiency between SOM and charged pharmaceuticals, atenolol showed highest sorption efficiency (~60%), followed by carbamazepine (~40%) and ibuprofen (<~30%). In addition, the removal efficiency of the targeted pharmaceuticals in the constructed wetland was estimated by comparing the concentrations of the pharmaceuticals at sampling points with flowing water. The results showed that the removal efficiency of atenolol and carbamazepine was almost 50%, whereas that of ibuprofen was only ~10%. A comparison of the results of lab-scale and field experiments showed that electrostatic interaction is one of the major pharmaceutical removal mechanisms in a constructed wetland.

Validation of a biotic ligand model on site-specific copper toxicity to Daphnia magna in the Yeongsan River, Korea

The objective of this study was to determine whether the water effect ratio (WER) or biotic ligand model (BLM) could be applied to efficiently develop water quality criteria (WQC) in Korea. Samples were collected from 12 specific sites along the Yeongsan River (YSR), Korea, including two sewage treatment plants and one estuary lake. A copper toxicity test using Daphnia magna was performed to determine the WER and to compare to the BLM prediction. The results of the WER from YSR samples also indicated significantly different copper toxicities in all sites. The model-based predictions showed that effluent and estuary waters had significantly different properties in regard to their ability to be used to investigate water characteristics and copper toxicity. It was supposed that the slight water characteristics changes, such as pH, DOC, hardness, conductivity, among others, influence copper toxicity, and these variable effects on copper toxicity interacted with the water composition. The 38% prediction was outside of the validation range by a factor of two in all sites, showing a poor predictive ability, especially in STPs and streams adjacent to the estuary, while the measured toxicity was more stable. The samples that ranged from pH 7.3-7.7 generated stable predictions, while other samples, including those with lower and the higher pH values, led to more unstable predictions. The results also showed that the toxicity of Cu in sample waters to D. magna was closely proportional to the amounts of acidity, including the carboxylic and phenolic groups, as well as the DOC concentrations. Consequently, the acceptable prediction of metal toxicity in various water samples needs the site-specific results considering the water characteristics such as pH and DOC properties particularly in STPs and estuary regions.