Utilization of wastewater in concrete structures and its impact on biomineralization

Abstract

Using treated wastewater in concrete production is an innovative approach to advance sustainable construction practices, successfully addressing environmental and economic concerns. The motivation behind undertaking this study arises from the urgent requirement for sustainable building materials and techniques that may effectively reduce the environmental consequences associated with the construction industry. The primary objective of this study is to investigate the feasibility, benefits, and potential impacts on the durability and lifespan of concrete buildings by replacing freshwater with treated wastewater in the construction and curing of concrete structures. Microbial concrete is produced by adding microbes to the concrete mix. These microbes contribute to the formation of calcium carbonate crystals inside the pores of the concrete, a process known as microbial induced calcium carbonate precipitation (MICCP). This results in a denser concrete microstructure, with higher compressive strength, lower initial surface absorption rates and lower initial and secondary absorption rates. In this study, treated wastewater was used instead of fresh water to cast and cure the mortar specimen. Microbes were mixed with the treated wastewater, along with nutrient media (NB) supplemented with calcium chloride and urea. From the experimental data, it was observed that the urease activity and calcium carbonate precipitation was higher in treated wastewater 2 TW 2 (450 U/ml and 0.372 mg/100ml respectively) and treated wastewater 1 TW1 (423 U/ml and 0.333 mg/ml respectively) as compared to FW (413 U/ml and 0.289 mg/100ml respectively). The specimen prepared using treated wastewater combined with bacteria demonstrates no major difference in compressive strength. However, there is a significant decrease in the sorptivity coefficient of specimen made with treated wastewater, 0.0024 (T2B), compared to those made with freshwater, 0.0193 (FB). The experimental results were approximately the same for the specimens cast and cured in treated wastewater and freshwater, suggesting that treated wastewater can be effectively substituted for freshwater in concrete production. This methodology enables the conservation of freshwater resources, which are encountering increasing difficulties due to urbanization and climate change, but also offers a feasible mechanism for efficiently handling the significant quantities of wastewater generated daily.