PFAS removal from landfill leachate by ozone foam fractionation: System optimization and adsorption quantification

Landfills are the primary endpoint for the disposal of PFAS-laden waste, which subsequently releases PFAS to the surrounding environments through landfill leachate. Ozone foam fractionation emerges as a promising technology for PFAS removal to address the issue. This study aims to (i) assess the effectiveness of the ozone foam fractionation system to remove PFAS from landfill leachate, and (ii) quantify equilibrium PFAS adsorption onto the gas-water interface of ozone bubbles, followed by a comparison with air foam fractionation. The results show that ozone foam fractionation is effective for PFAS removal from landfill leachate, with more than 90 % long-chain PFAS removed. The identified operating conditions provide valuable insights for industrial applications, guiding the optimization of ozone flow rates (1 L/min), dosing (43 mg/L) and minimizing foamate production (4 % wettability). The equilibrium modelling reveals that the surface excess of air bubbles exceeds that of ozone bubbles by 20-40 % at a corresponding PFAS concentration. However, the overall removal of PFAS from landfill leachate by ozone foam fractionation remains substantial. Notably, ozone foam fractionation generates foamate volumes 2 - 4 times less, resulting in significant cost savings for the final disposal of waste products and reduced site storage requirements.

A Magnetic Resonance Imaging Study of the Significance of the Distal Femoral Physis During Medial Patellofemoral Ligament Reconstruction

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction in adults often utilizes screw fixation in the distal femur. The aim was to define the safety of similar fixation in young patients, with respect to their open physis.

PURPOSE

To define the age-related relationship between the femoral insertion of the MPFL and the medial aspect of the distal femoral physis on magnetic resonance imaging (MRI) scans. The study investigates whether screw fixation at this point is safe with respect to patient age and screw inclination.

STUDY DESIGN

Cross-sectional study.

METHODS

Retrospective review of the MRI scans of 159 skeletally immature patients. The femoral insertion of the MPFL was defined with respect to the distal femoral physis. The predicted paths of 2-cm screw fixation were simulated both parallel to the joint line and 45° distally oblique; physeal and joint penetration were noted when present. Results are plotted against age and compared as quartile ranges.

RESULTS

The femoral insertion of the MPFL was found to be distal to the distal femoral physis in all patients by an average of 10 mm (range, 2-16 mm). The mean distance increases slightly with age in a nonlinear relationship (r = 0.51, P < .001) from 9 mm at age 10 years to 12 mm by age 16 years. For the classic, parallel screw, the risk of physeal breach is high for all age groups (mean, 64%). For the novel, oblique screw, joint penetration and physeal breach were less prevalent (mean, 13%), and importantly, the vast majority of these breaches were in younger children (age <9 years 9 months). With oblique screws, older children were at significantly lower risk than younger children (<3% vs 48%; P < .001).

CONCLUSION

This study accurately defines the relationship between the femoral insertion of the MPFL and the distal femoral physis in children and adolescents. A high risk of potentially poor outcomes was found during anatomic reconstruction of the MPFL in children utilizing classic (parallel) screw fixation, irrespective of age. However, in children older than 10 years, a 20-mm screw, from the anatomic MPFL insertion and directed 45° distally oblique, should be safe in 98% of patients.