Development of a slow polycolloid-releasing substrate (SPRS) biobarrier to remediate TCE-contaminated aquifers

•A slow polycolloid-releasing substrate (SPRS) to provide substrates is developed.•The SPRS can continuously supply substrate to enhance TCE dechlorination.•The SPRS contains vegetable oil, cane molasses, and two types of surfactants.•Addition of SRPC can create anaerobic conditions and form an active biobarrier.•A more complete TCE removal is reached using SPRS via biodegradation and sorption. In this study, an in situ slow polycolloid-releasing substrate (SPRS) biobarrier system was developed to continuously provide biodegradable substrates for the enhancement of trichloroethylene (TCE) reductive dechlorination. The produced SPRS contained vegetable oil (used as a slow-released substrate), cane molasses [used as an early-stage (fast-degradable) substrate], and surfactants [Simple Green™ (SG) and soya lecithin (SL)]. An emulsification study was performed to evaluate the globule droplet size and stability of SPRS. The distribution and migration of the SPRS were evaluated in a column experiment, and an anaerobic microcosm study was performed to assess the capability of SPRS to serve as a slow and long-term carbon-releasing substrate for TCE dechlorination. The results show that a stable oil-in-water (W/O, 50/50) emulsion (SPRS) with uniformly small droplets (D10, 0.93μm) has been produced, continuously supplying primary substrates. The emulsion containing the surfactant mixture (with 72mg/L SL and 71mg/L SG) had a small absolute value of the zeta potential, which reduced the inter-particle repulsion, leading the emulsion droplets to adhere to one another after collision. The addition of SPRS creates anaerobic conditions and leads to a more complete and thorough removal of TCE through biodegradation and sorption mechanisms.