Sewage pipes with structural defects cause ground subsidence owing to the occurrence of cavities, and trenchless rehabilitation is the primary repair method. Most trenchless rehabilitation uses the cured-in-place pipe (CIPP) method with a tube liner. UV photo curing has recently gained prominence for solving problems such as construction quality and high energy consumption associated with conventional thermal curing methods. This study developed a glass fiber tube liner and a hybrid power supply system with a uninterruptible power supply (UPS) and batteries to improve construction quality and shorten construction time when using UV photo curing. The tube liner had a flexural strength of 236.3 MPa and a flexural modulus of 10.5 GPa. These results are 7.88 and 6.2 times higher than the KS M3550-9 standards of 30 MPa and 1.7 GPa, respectively. Therefore, improved construction quality and post-construction sewage pipe lifespan were expected. A field test of construction with UV photo curing, using the glass fiber tube liner and the hybrid power system developed in this study, demonstrated successful performance in terms of power supply stability, UV photo-curing efficiency, and construction quality. Total working time was 121 min for construction of a 50 m section of the D600 using CIPP, significantly reducing construction time compared to conventional UV photo-curing technology.

UV photo-curing methods, which offer an alternative to conventional thermal curing, are widely employed in trenchless rehabilitation of sewage pipelines. However, enhancing construction safety and quality requires the optimization of GRP-CIPP thickness, reduction of VOC emissions during the UV photo-curing process, and development of fire prevention technologies owing to potential fire hazards during construction. In this study, a low-level VOC-CIPP (LV-CIPP) incorporating internal and external gas-blocking films was utilized to significantly reduce the concentration of styrene emissions generated during the UV photo-curing process. Additionally, a non-combustible air conversion system was developed and implemented to mitigate fire risks during the construction process. Fire risk can be substantially reduced by maintaining the oxygen concentration of the CIPP inflow air below the threshold defined by oxygen dilution extinguishing conditions.

Sewage pipes with structural defects cause ground subsidence owing to the occurrence of cavities, and trenchless rehabilitation is the primary repair method. Most trenchless rehabilitation uses the cured-in-place pipe (CIPP) method with a tube liner. UV photo curing has recently gained prominence for solving problems such as construction quality and high energy consumption associated with conventional thermal curing methods. This study developed a glass fiber tube liner and a hybrid power supply system with a uninterruptible power supply (UPS) and batteries to improve construction quality and shorten construction time when using UV photo curing. The tube liner had a flexural strength of 236.3 MPa and a flexural modulus of 10.5 GPa. These results are 7.88 and 6.2 times higher than the KS M3550-9 standards of 30 MPa and 1.7 GPa, respectively. Therefore, improved construction quality and post-construction sewage pipe lifespan were expected. A field test of construction with UV photo curing, using the glass fiber tube liner and the hybrid power system developed in this study, demonstrated successful performance in terms of power supply stability, UV photo-curing efficiency, and construction quality. Total working time was 121 min for construction of a 50 m section of the D600 using CIPP, significantly reducing construction time compared to conventional UV photo-curing technology.

UV photo-curing methods, which offer an alternative to conventional thermal curing, are widely employed in trenchless rehabilitation of sewage pipelines. However, enhancing construction safety and quality requires the optimization of GRP-CIPP thickness, reduction of VOC emissions during the UV photo-curing process, and development of fire prevention technologies owing to potential fire hazards during construction. In this study, a low-level VOC-CIPP (LV-CIPP) incorporating internal and external gas-blocking films was utilized to significantly reduce the concentration of styrene emissions generated during the UV photo-curing process. Additionally, a non-combustible air conversion system was developed and implemented to mitigate fire risks during the construction process. Fire risk can be substantially reduced by maintaining the oxygen concentration of the CIPP inflow air below the threshold defined by oxygen dilution extinguishing conditions.

Anaerobic digested sludge, a byproduct of anaerobic digestion, has high water content and low dewaterability, increasing the burden of subsequent treatment and associated costs. If not properly managed, it can lead to environmental issues such as pathogen contamination, odor generation, and leachate leakage. Microwave treatment can effectively improve sludge dewaterability. However, research on its application to the dewaterability of anaerobic digested sludge remains limited. This study aims to evaluate the improvement in the dewaterability of anaerobic digested sludge according to output power and specific energy. Under the conditions of 500 W output power and 5,000 kJ/kg TS specific energy, the water content of the dewatered cake was reduced by 11.21-16.64% compared to the conditions without microwave treatment, depending on the dosage of polyaluminum chloride (PAC). These findings suggest that microwave treatment can enhance the dewaterability of anaerobic digested sludge and serve as a potential solution for environmental mitigation.

To enhance chlorine ion removal and increase the current charging capacity of a desalination battery system, carbon nanotubes were applied to a carbonaceous electrode. Two types of composite electrodes were fabricated by attaching multiwalled carbon nanotubes (MWCNTs) to a carbon felt (CF) electrode via dip coating (D-CNT@CF) and electrophoresis (E-CNT@CF). These composite electrodes were then tested within a desalination battery system to evaluate their chlorine ion removal efficiency and current charging performance during the charging process. Microflocs of MWCNTs were observed on the surface of D-CNT@CF, whereas a uniform coating of MWCNTs was achieved on the surface of E-CNT@CF. Performance evaluations revealed that chlorine ion removal rates improved by 3.5% for D-CNT@CF and by 19.4% for E-CNT@CF compared to that of CF. Furthermore, the time required to reach maximum current charge was 40.0% for D-CNT@CF and E-CNT compared to CF. @CF decreased by 60.0%. These findings suggest that surface modification of carbonaceous electrodes through electrophoresis can result in a more stable coating and improve the performance of desalination battery systems.

This study applied a filter press for dewatering that uses pressure to reduce the water content of sludge generated in sewage treatment plants and evaluated the improvement of dewaterability under various coagulation conditions according to the type of coagulants, amounts, and pH conditions. The improvement of dewaterability was evaluated by measurement of time to filter (TTF), change in zeta potential, and sludge cake generated after filter press dewatering. It was found that under the applied coagulation conditions, inorganic coagulants were suitable for filter press dewatering. The optimum conditions were PAC with a dose of 70 mg/gTS, pH 10 for mixed sludge, and PAC with a dose of 100 mg/gTS, pH 6 for anaerobically digested sludge. Under optimal coagulation conditions, the water content of the sludge cake was 57% and 65%, respectively, marking a reduction by 19-27% compared to conventional centrifuge dewatering.

The study objective was to evaluate the enhanced removal of high concentrations of phosphorus from synthetic wastewater (solely phosphorus-containing) and real wastewater (pig manure) by using carbon nanotube (CNT)-coated steel slag. Generally, phosphorus removal by steel slag is attributed to Ca2+ eluted from the slag. However, in this study, CNT was used to control the excess release of Ca2+ from steel slag and increase the phosphorus removal. The phosphorus removal rate by the uncoated steel slag was lower than that of the CNT-coated steel slag, even though the Ca2+ concentrations were higher in the solution containing the uncoated steel slag. Therefore, the phosphorus removal could be attributed to both precipitation with Ca2+ eluted from steel slag in aqueous solution and adsorption onto the surface of the CNT-coated steel slag. Furthermore, the protons released from the CNT surface by exchanging with divalent cations acted to reduce the pH increase of the solution, which is attributed to the OH- eluted from the steel slag. The adsorption isotherm and kinetics of the CNT-coated steel slags followed the Freundlich isotherm and pseudo-second-order model, respectively. The maximum adsorption capacity of the uncoated and CNT-coated steel slags was 6.127 and 9.268 mg P g-1 slag, respectively. In addition, phosphorus from pig manure was more effectively removed by the CNT-coated steel slag than by the uncoated slag. Over 24 hours, the PO4-P removal in pig manure was 12.3% higher by the CNT-coated slag. This CNT-coated steel slag can be used to remove both phosphorus and metals and has potential applications in high phosphorus-containing wastewater like pig manure.