When a fast-food restaurant wastewater containing high strength of FOG is discharged into sewers, it builds up over time and clogs the sewer pipes. Similarly, when a fast-food restaurant wastewater flows into a drain field, it adheres to the surface of inlet pipes, gravel and soil, which will restrict the flow and eventually clog the drain field either physically or biologically. In this study, the Advanced Grease Interceptor System (AGIS) was used for enzymatic pretreatment of wastewater from a fast-food restaurant. This system uses aeration equipment, baffles, and a one-time inoculum with an in-situ condition in order to microbiologically breakdown FOG. The effect of the decomposed FOG in a drain field has not been previously studied, the focus of this research. The objectives of this study were to examine the impact of enzyme treatment on changes of the characteristic of triglyceride, design a bench-scale drain field and assess performance, and determine the impact of wastewater with/without enzyme pretreatment on clogging. LC/MS results showed that enzyme treatment impacted the characteristics of the triglycerides by breaking down the long chain fatty acid and reducing the number of double bonds. Bench-scale trenches with embedded soil moisture sensors for monitoring clogging proved to be a unique, and effective method to investigate the impact of diverse feedstocks. All bench-scale trenches removed a significant amount of COD, BOD5 and FOG, regardless of their initial concentrations. The results from the laboratory trenches showed that pretreatment of restaurant wastewater using an in-situ enzyme producing bacteria will delay clogging and premature drain field aging.
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