High-strength waste is wastewater with biochemical oxygen demand (BOD), total suspended solids (TSS) or grease well above ordinary domestic sewage, common at restaurants, breweries, wineries and some industrial or food-processing operations, and it can overload a conventional septic tank and drainfield biologically even at a volume that would be perfectly manageable for household-strength wastewater.
A conventional septic tank and drainfield are designed around the biological characteristics of typical domestic sewage. Wastewater with meaningfully higher organic loading, from food preparation, fermentation byproducts, certain cleaning chemicals, or industrial process water, asks more of the same-size system, which is why high-strength categories are evaluated on characteristics of the waste itself, not just gallons per day.
Where a state or local program characterizes a facility as high-strength, the design response is typically some combination of pretreatment (removing or reducing the load before it reaches the main system), additional tankage or treatment capacity, or in some cases treating the wastewater as an industrial discharge under a different program entirely.
Restaurant and food-service kitchens, breweries and wineries, some agricultural processing, and certain industrial or manufacturing wastewater are the categories most often flagged for high-strength characterization, though the specific threshold and testing requirement is set by each state's program.
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Biochemical oxygen demand (BOD), total suspended solids (TSS) or grease levels well above typical domestic sewage, which asks more of a conventional treatment system per gallon than household wastewater does.
Yes. Because the issue is the biological and chemical load per gallon, not just the gallon count, a system with adequate volume capacity can still be overloaded by high-strength waste.
Typically some combination of pretreatment before the main system, added tankage or treatment capacity, or in some cases treating the discharge under an entirely different, industrial-type program. Which applies is a state and facility-specific determination.
Page last reviewed 2026-08-31.