Food service establishment wastewater characterization and management practice evaluation

Food service establishments that use onsite wastewater treatment systems are experiencing hydraulic and organic overloading of pretreatment systems and/or drain fields. Design guidelines for these systems are typically provided in State regulations and based on residential hydraulic applications. For the purposes of this research, hydraulic loading indicates the daily flow of water directed to the wastewater system. Organic loading refers to the composition of the wastewater as quantified by five-day biochemical oxygen demand (BOD5), total fats, oils and greases (FOG), and total suspended solids (TSS). The first part of this study included an analysis of the central tendencies of analytical data of four wastewater parameters from 28 restaurants representing a broad spectrum of restaurant types. Field sampling consisted of two sets of grab samples collected from each restaurant for six consecutive days at approximately the same time each day. These sets were collected approximately two weeks apart. The numerical data included BOD5, FOG, and TSS. The fourth parameter evaluated was daily flow.
Data exploration and statistical analyses of the numerical data from the 28 restaurants was performed with the standard gamma probability distribution model in ExcelTM and used to determine inferences of the analytical data. The analysis shows higher hydraulic and organic values for restaurant wastewater than residential wastewater. The second part of the study included a statistical analysis of restaurant management practices and primary cuisine types and their influence on BOD5, FOG, TSS, and daily flow to determine if management practices and/or cuisine types may be influencing wastewater composition and flow. A self-reporting survey was utilized to collect management practice and cuisine type information.
Survey response information and analytical data were entered into an ExcelTM spreadsheet and subsequently incorporated into SASTM statistical software for statistical analysis. Analysis indicated that the number of seats in a restaurant, use of self-serve salad bars, and primary cuisine types are statistically significant indicators of wastewater characteristics.