Analyzing Activated Sludge Process Performance Data
Tze-Wen Chi
DOI: 10.2190/96V0-7XNJ-VJNX-7YU4
Abstract
Because of their important impacts on the environment, the biochemical oxygen demand (BOD) and total suspended solids (TSS) concentrations in effluent streams are critical performance measures for wastewater treatment plants. Wastewater effluent standards often specify the concentration limit for each of these pollutants. Most often, the reported BOD of treatment plant effluent is the sum of the residual unassimilated dissolved BOD and the BOD embedded in escaping biological solids of the clarifier effluent. To meet this effluent standard, a treatment plant must have adequate aeration for substrate removal and sludge formation suitable for separation. This article proposes a method to analyze the activated sludge treatment performance data for the estimation of dissolved BOD and BOD embedded in TSS. the estimation is useful for better control of operation and for the mathematical modeling, by Monod's reaction formulation, that governs the relation between the substrate concentration (S) and bacteria concentration (X). In the secondary clarifier effluent, S is the dissolved BOD while X represents the escaping biological solids or TSS. the proposed method applies the log-linear regression to derive a regression of dissolved BOD on TSS. This basic model is then utilized in conjunction with bootstrap to estimate the dissolved BOD and the BOD embedded in TSS. the analysis of a set of sixty-seven secondary biological municipal wastewater treatment plants yields an estimate of 2.65 mg/ℓ with standard deviation of 1.18 mg/ℓ for dissolved BOD and 0.605 with standard deviation of 0.083 for the ratio of BOD and TSS.
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