Eui-Jong Lee

Influence of microbubble in physical cleaning of MF membrane process for wastewater reuse

Currently, there is a growing emphasis on wastewater reclamation and reuse all over the world due to restricted water resources. Among a variety of wastewater reuse technologies, the use of microfiltration membranes (MF) is one of the popular processes because it has the ability to successfully eliminate particulates and colloidal matters. However, successful fouling control is not easy because effluents from the activated sludge process still contain small particulates and colloidal matters such as extracellular polymeric substance (EPS) and soluble microbial products (SMP). On the other hand, microbubbles have advantageous properties compared to common bubbles, but there hasn’t been reporting of the use of microbubbles in physical cleaning instead of aeration. Encouraging results were obtained herein through the application of microbubbles for physical cleaning. In evaluation of the cleaning efficiency, the efficiency of microbubbles was observed to be twice as high as that of aeration, except during the course of the initial 30xa0min. Total organic carbon (TOC) concentration of the membrane tank after treatment with microbubbles was more than twice as high as that after aeration for physical cleaning. The membrane cleaned with microbubbles also had the smoothest surface, with a roughness of 42.5xa0nm. In addition, microbubbles were found to effectively remove EPS and make the structure of the gel layer loose. In particular, the microbubbles had the ability to remove proteins through the effect of pyrolytic decomposition. Therefore, in FT-IR spectra of the membrane surfaces taken before and after physical cleaning, while each treatment showed similar peak positions, the peak values of the membrane treated with microbubbles were the lowest. Through various analyses, it was confirmed that microbubbles can remove foulants on the gel layer in spite of their very low shear force. This means that microbubble cleaning has full potential for use as a physical cleaning method in the wastewater reclamation process.

Application of dissolved air flotation (DAF) with coagulation process for treatment of phosphorus within permeate of membrane bioreactor (MBR)

AbstractIt is well known that eutrophication is one of the main issues with regard to environmental pollution and that phosphorus is the most critical among various nutrients. Consequently, effluent water quality of wastewater treatment plants has been recently reinforced in Korea. Many studies have been made on membrane bioreactor (MBR) processes, some of the more advanced wastewater treatment processes. However, MBR processes are relatively vulnerable to biological phosphorus treatment in comparison with conventional activated sludge processes. Alternately, dissolved air flotation (DAF) processes were applied as post-treatment of MBR processes in order to decrease T-P concentration of the final effluent. It was observed that T-P removal efficiency was 51.2% and that T-P concentration of the final effluent ranged from 0.49 to 1.62xa0mg/L with addition of 15xa0mg/L of alum to the rapid mixing reactor of DAF processes. The next step includes the addition of anionic polymers and bentonite to slow and rapid mixi...

Combined coagulation/ceramic membrane ultrafiltration system for reclamation of degreasing washing water

AbstractCurrently, there is growing emphasis on wastewater reclamation and reuse around the world. In this study, a combined coagulation/ceramic membrane ultrafiltration system was used to treat degreasing washing water under high pH/alkalinity conditions containing surfactants, organic matter and other materials resulting from rinsing processes in the plating industry. Coagulant exists as sol or gel species that was not suitable for complexation with smaller surfactants and organic matter under high pH/alkalinity conditions. A pH neutralization process was introduced to improve the removal efficiency of the coagulant prior to coagulation. An optimal coagulant (ferric chloride), optimal coagulation pHxa05, and optimal coagulant dosage (700xa0mg Fe/L) were proposed as a result of coagulation tests. Under slightly acidic conditions, species distribution of ferric chloride consisted of monomers and medium polymers that were favorable for the formation of surfactant–coagulant or organic matter–coagulant complexes...

An analysis of the effects of osmotic backwashing on the seawater reverse osmosis process

Fouling control is an important consideration in the design and operation of membrane-based water treatment processes. It has been generally known that chemical cleaning is still the most common method to remove foultants and maintain the performance of reverse osmosis (RO) desalination. Regardless of the chemical membrane cleaning methods applied effectively, however, frequent chemical cleaning can shorten the membrane life. In addition, it also increases operating and maintenance costs due to the waste chemical disposal. As an alternative, osmotic backwashing can be applied to RO membranes by diluting the concentration polarization (CP) layer. In this study, the effects of osmotic backwashing were analysed under different total dissolved salts (TDSs) and backwashing conditions, and the parameters of the osmotic backwashing were evaluated. The results of the analysis based on the properties of the organic matters found in raw water showed that the cleaning efficiency in respect to the fouling by hydrophilic organic matters was the greatest. Osmotic backwashing was carried out by changing the TDS of the permeate. As a result, the backwashing volume decreased with time due to the CP of the permeate and the backwashing volume. The difference in the osmotic pressure between the raw water and the permeate (Δ π) also decreased as time passed. It was confirmed that when the temperature of the effluent was high, both the cleaning efficiency and the backwashing volume, which inpours at the same time, increased. When the circulation flow of the effluent was high, both the cleaning efficiency and the backwashing volume increased.

A comparative study on per capita waste generation according to a waste collecting system in Korea

As cities are becoming increasingly aware of problems related to conventional mobile collection systems, automated pipeline-based vacuum collection (AVAC) systems have been introduced in some densely populated urban areas. The reasons are that in addition to cost savings, AVAC systems can be efficient, hygienic, and environmentally friendly. Despite difficulties in making direct comparisons of municipal waste between a conventional mobile collection system and an AVAC system, it is meaningful to measure the quantities in each of these collection methods either in total or on a per capita generation of waste (PCGW, g/(day*capita)) basis. Thus, the aim of this study was to assess the difference in per capita generation of household waste according to the different waste collection methods in Korea. Observations on household waste show that there were considerable differences according to waste collection methods. The value of per capita generation of food waste (PCGF) indicates that a person in a city using AVAC produces 60xa0% of PCGF (109.58xa0g/(day*capita)), on average, compared with that of a truck system (173.10xa0g/(day*capita)) as well as 23xa0%p less moisture component than that with trucks. The value of per capita generation of general waste (PCGG) in a city with an AVAC system showed 147.73xa0g/(day*capita), which is 20xa0% less than that with trucks delivered (185xa0g/(day*capita)). However, general waste sampled from AVAC showed a 35xa0%p increased moisture content versus truck delivery.