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BOD test bottles at the laboratory of a wastewater treatment plant. Biochemical oxygen demand (also known as BOD or biological oxygen demand) is an analytical parameter representing the amount of dissolved oxygen (DO) consumed by aerobic bacteria growing on the organic material present in a water sample at a specific temperature over a specific time period.
The model describes how dissolved oxygen (DO) decreases in a river or stream along a certain distance by degradation of biochemical oxygen demand (BOD). The equation was derived by H. W. Streeter, a sanitary engineer, and Earle B. Phelps, a consultant for the U.S. Public Health Service, in 1925, based on field data from the Ohio River. The ...
The reactions take place by the joint participation of several microorganisms living within the pond. The organic matter is measured as biochemical oxygen demand (BOD). BOD values in the pond effluent are lower than in the influent, reflecting the removal of organic matter. This pond biome uses organic matter from the wastewater as food.
Because the Ultimate BOD is so time consuming, the 5-day BOD has been almost universally adopted as a measure of relative pollution effect. There are also many different COD tests of which the 4-hour COD is probably the most common. There is no generalized correlation between the 5-day BOD and the ultimate BOD.
With UASB (but also EGSB and ECSB), the process of settlement and digestion occurs in one or more large tank(s). The effluent from the UASB, which has a much reduced biochemical oxygen demand (BOD) concentration, usually needs to be treated further, for example with the activated sludge process, depending on the effluent quality requirements.
The ratios were obtained using the criterion that choked flow occurs when the ratio of the absolute upstream pressure to the absolute downstream pressure is equal to or greater than ([+] /) / (), where is the specific heat ratio of the gas. The minimum pressure ratio may be understood as the ratio between the upstream pressure and the pressure ...
The number of transfer units (NTU) method is used to calculate the rate of heat transfer in heat exchangers (especially parallel flow, counter current, and cross-flow exchangers) when there is insufficient information to calculate the log mean temperature difference (LMTD). Alternatively, this method is useful for determining the expected heat ...
Mathematically the flow coefficient C v (or flow-capacity rating of valve) can be expressed as =, where Q is the rate of flow (expressed in US gallons per minute), SG is the specific gravity of the fluid (for water = 1), ΔP is the pressure drop across the valve (expressed in psi).