SRT and F/M Ratio

Solids retention time and food-to-microorganism ratio with conventional-activated-sludge check.

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Formula and source

SRT (solids retention time, days) = (MLSS_lb in tank) / (TSS_lb wasted per day + TSS_lb lost in effluent per day). F/M ratio = BOD_lb_per_day / MLVSS_lb_in_tank. Conventional activated sludge typical: SRT 5-15 d, F/M 0.2-0.5.

Metcalf & Eddy (Wastewater Engineering: Treatment and Resource Recovery), 5th edition by name. Water Environment Federation MOP-8 (Design of Municipal Wastewater Treatment Plants) by name.

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