Interactive Calculator · 2026
Organic Loading Rate Calculator
Find the volumetric organic loading rate (OLR) on a bioreactor from the flow, inlet BOD and reactor volume — the load the biology has to digest each day, in kg BOD per m³ of tank.
Your OLR against typical activated-sludge design ranges
Reactor inputs
Average daily influent flow.
Raw sewage ≈ 250–350 mg/L.
Working volume of the aeration tank.
Where your loading falls
Computed OLR of 0.15 kg BOD/m³.d — Extended aeration range. Bars show the mid-point of each typical range; the dashed line marks your value.
Extended aeration (0.1–0.3 kg BOD/m³.d) — Long sludge age, low load — small package STPs.
Conventional ASP (0.3–0.6 kg BOD/m³.d) — Standard activated-sludge municipal plants.
High-rate (0.6–1.2 kg BOD/m³.d) — Compact, heavily loaded reactors.
How this is calculated
- BOD load = flow × inlet BOD ÷ 1000 = 100 × 300 ÷ 1000 = 30 kg BOD/day.
- Organic loading rate = BOD load ÷ reactor volume = 30 ÷ 200 = 0.15 kg BOD/m³.d.
Volumetric OLR is an indicative design check for concept planning. A detailed design must also fix the F/M ratio, sludge age, oxygen demand and tank geometry — confirm with a qualified consultant before procurement.
Related Guides — Deep-dive reading
Understanding Organic Loading in STPs: OLR, F/M Ratio and Tank Sizing
What organic loading really means, why it — not just flow — decides how big your aeration tank must be, and the typical OLR and F/M ranges for ASP, MBBR, SBR and MBR, explained for the Indian context.
Sewage Treatment PlantsUnderstanding Hydraulic Retention Time (HRT) in STPs: The Complete Guide
What hydraulic retention time really means, how it sets the size of your reactor and the quality of your treated water, typical HRT figures for ASP, MBBR, SBR and UASB, and why HRT and SRT are two different clocks you must not confuse.
Sewage Treatment PlantsFluidized Bed Reactor (FBR) for Wastewater: Working, Media & Trade-offs
How a fluidized bed reactor grows a dense biofilm on fine sand or carbon media kept suspended by upflow, packs enormous treatment into a tiny volume, and why it is the tool of choice for high-strength industrial streams rather than ordinary apartment sewage.
Sewage Treatment PlantsRelated Tools — You may also find these useful
Air Requirement Calculator
Estimate the process air an aeration tank needs — enter flow, inlet BOD, O2 demand factor and transfer efficiency to get O2 demand and blower air in m3/day and m3/min.
STP CalculatorApartment STP Planner
Plan an apartment complex sewage treatment plant from flats and occupancy — get population load, sewage flow, recommended STP capacity in KLD, treatment technology and approximate space.
PlannerASP vs SBR Comparator
Weight seven criteria by importance to get a scored recommendation between the Activated Sludge Process and a Sequential Batch Reactor for your sewage treatment plant.
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