A new monitoring approach for sustainability assessment of subsurface utilities gasket materials against gasoline and chlorinated solvents: Field evaluation and model development.

Once installed, underground concrete pipes with rubber gaskets might be exposed to contaminated soil and groundwater. A pipe material monitoring capsule (PMMC) has been developed to evaluate volatile organic compounds (VOCs) breaking through three types of pipe gaskets; Neoprene, Buna-N, and Viton. The PMMCs were deployed in three contaminated sites: two with gasoline and one with chlorinated solvent (CS). A 3-D field-domain numerical model has been developed for each site to calibrate equivalent hydraulic parameters of each gasket material (ke, D) against benzene and PCE diffusion. The calibrated parameters were then used to compute the concentrations as well as rate of breakthrough of the two study contaminants. A protocol was developed for installing/retrieval of PMMCs to monitor PCE and benzene mass breaking through the gasket material with time. Employing PMMC, benzene concentrations breaking through the Neoprene and Buna-N after 4 months were approximately 70% and 60% respectively of the monitoring wells concentration. The corresponding value for PCE breakthrough after 4 months was 60% for both the Neoprene and Buna-N. Both gasket materials of Neoprene and Buna-N yielded similar performances, including higher rate of contaminant breakthrough compared to Viton. A nonlinear relationship of mass breaking through the gaskets of benzene and PCE with time was discerned from the modeling and field data.

Reducing fat, oil, and grease (FOG) deposits formation and adhesion on sewer collection system structures through the use of fly ash replaced cement-based materials.

The accumulation of fat, oil, and grease (FOG) deposits in sewer pipes reduces their conveyance and results in Sanitary Sewer Overflows (SSOs). Previous research has shown that concrete used in sewer lines is a significant source for calcium ion, which participates in the FOG deposit formation mechanism. However, no research has been conducted to understand the effect of calcium leaching from cement on FOG deposits formation and adhesion. This study quantifies the reduction in FOG deposit formation when Fly Ash (FA), a Supplementary Cementitious Material (SCM), is used to replace cement in the production of High Volume Fly Ash (HVFA) concrete materials. Results show that after 90 days of leaching test under controlled pH conditions, 75% and 86% reduction in calcium release were achieved from 50% and 75% FA replacement, respectively. After 30 days of FOG deposits formation tests on HVFA samples, 58% and 81% reduction in FOG deposit formation was found for 50% and 75% FA replacement, respectively. FTIR analyses of FOG deposits formed on concrete samples without FA replacement exhibited high calcium soap content (48%), while, FOG deposit formed on HVFA concrete materials showed low calcium soap percentage (22~29%). Furthermore, FTIR analyses report the first spatial variation found in FOG deposits that includes a surface layer of hard FOG deposits with high calcium soap absorbance and an outer layer of soft FOG deposits consisting of a low calcium absorbance. FTIR analyses revealed that the FOG deposit formation mechanism is affected by the availability of calcium and pH near the concrete surface. Finally, HVFA concrete materials were tested for compressive strength and durability against microbially induced concrete corrosion (MICC). After 180 days of sealed curing, HVFA concrete exhibited adequate compressive strength necessary for the sewer line construction and 50% FA replacement revealed satisfactory durability against MICC.