Kyung-Guen Song

Removal of ions in nickel electroplating rinse water using low-pressure nanofiltration

Abstract This study investigated the performance of nanofiltration (NF), which is more economic than reverse osmosis (RO) and requires lower pressure for the removal of cations and anions in simulated nickel electroplating rinse water environments. Removal rates according to changes in basic parameters such as pressure, crossflow velocity, pH, ion types and ion concentrations were observed. In single-salt system experiments NF removed more Ni2+ in NiSO4 solution than in NiCl2 solution. As concentration increased in single-salt systems, removal rate of sulfate salts and some chloride salts (in the system with cations of +1 valency) decreased, whereas chloride salts with cations of +2 valency increased. In the experiment with multi-salt systems, the removal rate of ions showed a logarithmic increase with pressure until 3 kgf/cm2 (0.294 MPa), and beyond this value the removal rate stabilized. Change in crossflow velocity did not affect the ion removal, but change in pH was a significant factor for Cl− removal rate. Furthermore, the removal rate of Cl− was heavily dependent on the amount of SO42− present in the same system. In experiments using simulated nickel electroplating rinse water below a pressure of 3 kgf/cm2, the removal efficiencies of ions increased greatly with increased influent salt concentration and pressure, whereas beyond 3 kgf/cm2, the removal efficiency stabilized. This result indicated that 3 kgf/cm2 is the optimum pressure for NF application against nickel electroplating rinse water.

Performance of membrane bioreactor system with sludge ozonation process for minimization of excess sludge production

This study investigated the effects of sludge ozonation on excess sludge minimization and enhancement of nutrient removal in membrane bioreactor (MBR). Two modified Ludzack-Ettinger (MLE) type MBR system were operated in parallel with or without a batch-type sludge ozonation process. A -flat type microfiltration membrane (pore size 0.4 μm) was used. The specific ozone dosage was set at 0.1 gO3lgSS. In the control run (without sludge ozonation), the daily sludge production was about 1.04 gld. However, in the ozone run (with sludge ozonation), the daily sludge production was negligible. In addition, the MLSS concentrations and the volatile fraction of MLSS in the reactor maintained constant around 8,000 mg/L and 0.75, respectively, without excess sludge. The concentration of effluent was maintained at a satisfactory level in both runs. Furthermore, the MBR system with sludge ozonation process showed relatively better nutrient removal than without sludge ozonation. It revealed that ozonated sludge might be completely degraded in the reactor and effectively used as a carbon source. During the operation, the transmembrane pressure was maintained lower than 10 kPa under 0.36 mld of flux regardless of presence of sludge ozonation. Application of sludge ozonation to the MBR system was significantly effective for minimization of excess sludge production as well as for enhancement of nutrient removal.

Treatment of domestic wastewater using microfiltration for reuse of wastewater

Abstract This study was conducted to evaluate the applicability of microfiltration in treating domestic wastewater for reuse. A hollow fiber microfiltration membrane was used in the pilot test. The pore size of the membrane was 0.1 μm and effective surface area was 20 m 2 . The maximum capacity of the pilot plant was 10m 3 /d. The microfiltration system could be operated for 120 days without any cleaning procedure. It was found that agitation in the membrane tank had an effect on fouling prevention. In particular, the bi-directional agitation significantly reduced fouling. Chemical cleaning was effective in recovering of permeate flux and resistance, but in spite of chemical cleaning, fouling slowly progressed. According to the particle size distribution, in the membrane tank particles were transformed into smaller size by agitator-induced shear force. Based on mass balance analysis, about 60% of dissolved TOC mass removal in the system was attributed to biodegradation, indicating its important role. But suspended solids and colloidal matter were removed by the sieve mechanism of the membrane. Effluent quality was found to be lower than 30 mg/L of COD, 10 mg/L of BOD, 10 mg/L of TOC, 1 NTU of turbidity and 2 mg/L of SS, respectively. It satisfies the standard for wastewater reuse.

Effects of internal recycling time mode and hydraulic retention time on biological nitrogen and phosphorus removal in a sequencing anoxic/anaerobic membrane bioreactor process

This study investigated the effects of internal recycling time mode and hydraulic retention time (HRT) on nutrient removal in the sequencing anoxic/anaerobic membrane bioreactor process. Denitrification and phosphorus release were reciprocally dependent on the anoxic/anaerobic time ratio (Ax/An). As Ax/An increased, nitrogen removal rate increased but phosphorus removal rate decreased. The increasing Ax/An provided the longer denitrification period so that the organic substrate were consumed more for denitrification rather than phosphorus release in the limited condition of readily biodegradable substrate. Decreasing HRT increased both nitrogen and phosphorus removal efficiency because as HRT decreased, food-to-microorganism loading ratio increased and thus enhanced the biological capacity and activity of denitrifying bacteria. This could be verified from the observation mixed liquor suspended solids concentration and specific denitrification rate. The change of Ax/An and HRT affected phosphorus removal more than nitrogen removal due to the limitation of favourable carbon source for phosphorus accumulating organisms.

Application of nanofiltration for recycling of paper regeneration wastewater and characterization of filtration resistance

Abstract The potential of using nanofiltration (NF) membranes in purification of the effluent from paper regeneration wastewater treatment plant was investigated. The change of filtration resistance for various NF membranes and the mechanisms responsible for the resistance were identified. The mahyority of the pollutants remaining in the wastewater were mostly nonbiodegradable and ware less than MWCO 3000 in size, indicating micro- or ultrafiltration may not be applicable. Among the five NF membranes used in this study, NTR-759HR showed the highest rejection efficiency; 98.5% and 99.5% for TOC and color, respectively. The TOC concentration of the permeate could be maintained at less than 0.7 mg/L regardless of the concentration of the feed solution. However, the permeate flux steadily decreased with time up to 50% of the initial value at the recovery rate of 89%. To investigate the possible mechanisms responsible for the reduction of permeate flux, the observed total filtration resistance was divided into three categories; (1) the intrinsic membrane resistance for pure water (Rm), (2) resistance due to concentration polarization (Rcp), and (3) resistance due to membrane fouling (Rf). The increase of filtration resistance for NTR 7410 could be explained by membrane fouling while those for NTR-759HR and NTR-7250 are attributed to the osmotic pressure build-up due to concentration polarization. The different mechanisms for the flux reduction were studied.

Effects of effluent organic matter characteristics on the removal of bulk organic matter and selected pharmaceutically active compounds during managed aquifer recharge: Column study

Soil column experiments were conducted to investigate the effects of effluent organic matter (EfOM) characteristics on the removal of bulk organic matter (OM) and pharmaceutically active compounds (PhACs) during managed aquifer recharge (MAR) treatment processes. The fate of bulk OM and PhACs during an MAR is important to assess post-treatment requirements. Biodegradable OM from EfOM, originating from biological wastewater treatment, was effectively removed during soil passage. Based on a fluorescence excitation-emission matrix (F-EEM) analysis of wastewater effluent-dominated (WWE-dom) surface water (SW), protein-like substances, i.e., biopolymers, were removed more favorably than fluorescent humic-like substances under oxic compared to anoxic conditions. However, there was no preferential removal of biopolymers or humic substances, determined as dissolved organic carbon (DOC) observed via liquid chromatography with online organic carbon detection (LC-OCD) analysis. Most of the selected PhACs exhibited removal efficiencies of greater than 90% in both SW and WWE-dom SW. However, the removal efficiencies of bezafibrate, diclofenac and gemfibrozil were relatively low in WWE-dom SW, which contained more biodegradable OM than did SW (copiotrophic metabolism). Based on this study, low biodegradable fractions such as humic substances in MR may have enhanced the degradation of diclofenac, gemfibrozil and bezafibrate by inducing an oligotrophic microbial community via long term starvation. Both carbamazepine and clofibric acid showed persistent behaviors and were not influenced by EfOM.

Application of microfiltration with a novel fouling control method for reuse of wastewater from a large-scale resort complex

Abstract A study was conducted to investigate the treatability of a new microfiltration system utilizing agitator-induced flushing of the membrane to prevent fouling for wastewater reclamation. A hollow-fiber membrane was immersed in the tank and permeate was filtered through the membrane by intermittent suction using a pump. Influent from the large-scale resort complex was used. In the tank an agitator was operated at 350 rpm, with clockwise (4s) - stop (1s) - counter-clockwise (4s) rotation cycle. Membrane pore size, permeate flux and suction mode were studied. The optimal operational setting was determined to be 0.02 m/h flux, with 10-min suction and 2-min idle permeate pumping cycle. This setting was capable of 77 days of continuous operation without chemical cleaning. Below 20 mg/L of COD, 3.5 mg/L of TOC, 0.2 NTU of turbidity and no suspended solids were contained in the effluent. This system was adequate for the reuse of wastewater for secondary applications such as in toilet flushing.

Retrofitting municipal sewage treatment plants using an innovative membrane-bioreactor system

Most of the municipal sewage treatment plants (MSTPs) being operated in Korea were designed for wastewater with average concentrations of municipal sewage. However, they are in fact being operated at low organic loading. Thus, most of the secondary small-scale sewage treatment plant cannot satisfy the effluent standard. An innovative ultrafiltration membrane-bioreactor (MBR) system was proposed to retrofit the existing MSTP. The objective of this study was to investigate the feasibility of applying ultrafiltration MBR to the conventional activated sludge process in order to improve the treatment efficiency of the plant. The tested membrane was a UF of 50 kDa and an effective surface area per module was 8.4m2. The UF was operated with about 2m/s of the crossflow velocity. In preliminary experiments, the MBR was more effective than the direct ultrafiltration of sewage for the enhancement of effluent quality and the preventing fouling. In the crossflow membrane-bioreactor (CFMBR) system, the COD concentration of the effluent was maintained at less than 10 mg/L, regardless of the influent COD concentration. The total nitrogen and total phosphorus of the effluent were 5 mg/L and 1 mg/L, respectively. The CFMBR system could completely remove pin-flocs which occurred in the sedimentation tank due to the low organic loading. The water qualities of the effluent obtained from all the experiments in this study were satisfied to the guidelines for the effluent discharge. Stable operation of a CFMBR, as judged by the effluent COD, SS and T-N concentrations, was achieved with low organic wastewater for 40 days without chemical washing.

Removal of metal from acid mine drainage using a hybrid system including a pipes inserted microalgae reactor.

In this study, the microalgae culture system to combined active treatment system and pipe inserted microalgae reactor (PIMR) was investigated. After pretreated AMD in active treatment system, the effluent load to PIMR in order to Nephroselmis sp. KGE 8 culture. In experiment, effect of iron on growth and lipid accumulation in microalgae were inspected. The 2nd pretreatment effluent was economic feasibility of microalgae culture and lipid accumulation. The growth kinetics of the microalgae are modeled using logistic growth model and the model is primarily parameterized from data obtained through an experimental study where PIMR were dosed with BBM, BBM added 10 mg L(-1) iron and 2nd pretreatment effluent. Moreover, the continuous of microalgae culture in PIMR can be available. Overall, this study indicated that the use of pretreated AMD is a viable method for culture microalgae and lipid accumulation.

LED light stress induced biomass and fatty acid production in microalgal biosystem, Acutodesmus obliquus.

Microbial algal system can serve as a potential source for the production of much high value bioproducts and biofuels. The quality and intensity of light are the key elements to optimize the production of algal biomass and fatty acid contents. This study presents the effect of differential LED flashing light conditions on the growth of microalgae, Acutodesmus obliquus. The induced light stress was optimized for its biomass and fatty acid content. The microalgae are exposed to various frequency of intermittent LED flashing light (blue and red lights) at three different phases in the 18 day cell growth (log, lag and stationary phase). The frequency of light flashing rate was adjusted to 120, 10, 5, 3.75, and 1 times per min. The effect of light stress on growth and fatty acids composition of A. obliquus induced an increase in algae growth and fatty acid production. Different optimal timing for light stress was subjected to elucidate the effect of light stress on algae growth and fatty acid production. The results showed an increase in the algae growth (1.2mg/L of chl a content) under light stress condition at FT10 (flashing time, 10 times per min) from the initial day (log phase) compared with the control experiment (0.4 mg/L of chl a content). However, the total fatty acids (71 mg/g) and volumetric FAME production (9.4 ml/l) level was found to be significant under FT5 (flashing time, 5 times per min), adopting flashing light from day 10 (stationary phase). TEM studies also revealed the deposition of lipid to be largest in the 18 day old cells under flashing light (FT5) condition, representing maximum accumulation of lipids bodies (up to 770 nm diameter in particle size) occupying approximately 42% of the total area of the cell.