Duk Chang

Phosphate filtering characteristics of a hybridized porous Al alloy prepared by surface modification

In this study, a porous Al alloy filter was designed for water purification systems. The combination of higher permeability for fluid flow and excellent filtering characteristics for removing pollutants is required for water purification. The filters macropore structure was controlled by a powder metallurgical process using granulated powders for high permeability and its micropore structure was generated by alkali surface modification on the macroporous sintered body for enhanced filtration efficiency. After surface modification, the specific surface area was increased by 10 times over the as-sintered specimen. Phosphate filtering characteristic was noticeably improved by a ligand exchange between phosphate and aluminum hydroxide formed by alkali surface modification.

Removal of bacterial pathogen from wastewater using Al filter with Ag-containing nanocomposite film by in situ dispersion involving polyol process

In this study, a filter with deposited Ag/Al(OH)(3) mesoporous nanocomposite film was fabricated to remove bacterial pathogens from wastewater. Mesoporous Al(OH)(3) film was generated on the Al foam body by alkali surface modification, followed by immersion in a polyol solution for 4h at an elevated temperature in order to deposit silver nanoparticles (Ag NPs). The Al(OH)(3) porous matrix showed a significant increase in specific surface area due to the large size of the voids between flakes, which reached several tens of nanometers. After in situ three-dimensional deposition of Ag NPs by a polyol process, the Ag NPs were nucleated and grown at the surface of the mesoporous Al(OH)(3) film. The filter with Ag/Al(OH)(3) mesoporous nanocomposite film showed a good bacterial pathogen removal rate within a very short contact time compared to the untreated Al foam filter. Filters with deposited Ag/Al(OH)(3) mesoporous nanocomposite film have great potential for application as antimicrobial filters for tap water purification, wastewater treatment, and other bio-related applications.

Novel phased isolation ditch system for enhanced nutrient removal and its optimal operating strategy

Abstract Phased isolation ditch system with intrachannel clarifier is a simplified novel oxidation ditch system enhancing simultaneous removal of biological nitrogen and phosphorus in municipal wastewater. The system employs two ditches with intra-clarifier, and eliminates external final clarifier, additional preanaerobic reactor, and recycle of sludge and nitrified effluent. Separation of anoxic, anaerobic, and aerobic phases can be accomplished by alternating flow and intermittent aeration. Its pilot-scale system operated at HRTs of 10–21 h, SRTs of 15–41 days, and a cycle times of 2–8 h showed removals of BOD, TN, and TP in the range of mixed liquor temperature above 10°C as high as 88–97, 70–84, and 65–90%, respectively. As the SRTs became longer, the effluent TN decreased dramatically, whereas the effluent TP increased. Higher nitrogen removal was accomplished at shorter cycle times, while better phosphorus removal was achieved in longer cycle times. Optimal system operating strategies maximizing the performance and satisfying both the best nitrogen and phosphorus removals included HRTs ranged 10–14 h, SRTs ranged 25–30 days, and a cycle time of 4 h at the mixed liquor temperature above 10°C. Thus, complete phase separation in a cycle maximizing phosphorus release and uptake as well as nitrification and denitrification was accomplished by scheduling of alternating flow and intermittent aeration in the simplified process scheme. Especially, temporal phase separation for phosphorus release without additional anaerobic reactor was successfully accomplished during anaerobic period without any nitrate interference and carbon-limiting.

Dynamic process response to sludge thickening behaviors in the anaerobic sequencing batch reactor treating high-solids-content waste.

Solid-liquid separation and its type greatly affected the stability and performance of the anaerobic sequencing batch reactor (ASBR) for municipal sludge digestion. Flotation thickening occurred in mesophilic ASBR, while solid-liquid separation in thermophilic ASBR followed a gravity thickening. The hydraulic retention time (HRT) and cycle period as well as the type of thickening were key parameters governing sludge thickenability and critical solids accumulation. Thickened sludge volume was a critical operating variable in the ASBR with the gravity thickening, which had a poor performance because of the loss of thickened solids, and sludge interface disruption or instability of sludge bed due to internal gas evolution. A cyclic mutual effect between thickened volume and gas production was a serious in the gravity thickening, whereas it was insignificant in the flotation thickening.

CHARACTERISTICS OF CRITICAL SOLID-LIQUID SEPARATION AND ITS EFFECT ON THE PERFORMANCE OF AN ANAEROBIC SEQUENCING BATCH REACTOR TREATING MUNICIPAL SLUDGE

Solid-liquid separation and its type greatly affected the stability and performance of an anaerobic sequencing batch reactor (ASBR) for municipal sludge digestion. Flotation thickening occurred in the mesophilic ASBR, while solid-liquid separation in the thermophilic ASBR followed gravity thickening. Hydraulic retention times (HRT) and cycle period as well as type of thickening were key parameters governing sludge thickenability and critical solids accumulation. Thickened sludge bed volume was a critical operating variable in the ASBR with gravity thickening, which had poor performance because of the loss of thickened solids, and sludge interface disruption or instability of sludge bed due to internal gas evolution. A cyclic mutual effect between thickened volume and gas production was serious in gravity thickening, whereas it was insignificant in flotation thickening.

Integrated nitrogen removal biofilter system with ceramic membrane for advanced post-treatment of municipal wastewater

ABSTRACT The pre-denitrification biofilm process for nitrogen removal was combined with ceramic membrane with pore sizes of 0.05–0.1 µm as a system for advanced post-treatment of municipal wastewater. The system was operated under an empty bed hydraulic retention time of 7.8 h, recirculation ratio of 3, and transmembrane pressure of 0.47 bar. The system showed average removals of organics, total nitrogen, and solids as high as 93%, 80%, and 100%, respectively. Rapid nitrification could be achieved and denitrification was performed in the anoxic filter without external carbon supplements. The residual particulate organics and nitrogen in effluent from biofilm process could be also removed successfully through membrane filtration and the removal of total coliform was noticeably improved after membrane filtration. Thus, a system composed of the pre-denitrification biofilm process with ceramic membrane would be a compact and flexible option for advanced post-treatment of municipal wastewater.

Field-scale electrolysis/ceramic membrane system for the treatment of sewage from decentralized small communities

ABSTRACT The electrolysis process adopting copper electrodes and ceramic membrane with pore sizes of 0.1–0.2 μm were consisted to a system for the treatment of sewage from decentralized small communities. The system was operated under an HRT of 0.1 hour, voltage of 24 V, and TMP of 0.05 MPa. The system showed average removals of organics, nitrogen, phosphorus, and solids of up to 80%, 52%, 92%, and 100%, respectively. Removal of organics and nitrogen dramatically increased in proportion to increment of influent loading. Phosphorus and solids were remarkably eliminated by both electro-coagulation and membrane filtration. The residual particulate constituents could also be removed successfully through membrane process. A system composed of electrolysis process with ceramic membrane would be a compact, reliable, and flexible option for the treatment of sewage from decentralized small communities.