Impacts of biological additives, part 2: Septic tank effluent quality and overall additive efficacy

The efficacy of 1,200+ septic tank additives on the market has always been a concern due to the previous lack of independent, replicated, third-party, field-scale research studies. Twenty experimental units (well-maintained, full-size, functioning septic tanks) were pumped out 2-3 years before being assessed in the study presented here. These units were treated with one of three biological additives or a control in a double-blind study. Effluent data analyzed using a mixed linear model showed that the overall treatment effect was significant for effluent five-day biochemical oxygen demand (BOD ₅) concentrations. One additive had significantly lower effluent BOD ₅ concentrations in septic tank effluent than the control and the other two additives had the same BOD ₅ as the control. No statistically significant effluent total suspended solids concentration effect occurred for any additive. These results were also considered in concert with two prior related studies regarding microbiological contents as well as sludge and scum accumulation rates across three prior-maintenance levels in 48 septic tanks.