The following points will highlight the four main ways through which the demand of oxygen in sewage is expressed. The ways are: 1. Biochemical Oxygen Demand (BOD) 2. Chemical Oxygen Demand (COD) 3. Total Oxygen Demand (TOD) 4. Theoretical Oxygen Demand (ThOD). Way # 1. Biochemical Oxygen Demand (BOD): Biochemical oxygen demand (BOD) may be defined as the amount of [...]
The disposal of sewage without treatment or after treatment may be carried out by the following two methods: 1. Dilution or the Disposal of Sewage in Water 2. Land Treatment or the Disposal of Sewage on Land. Method # 1. Disposal by Dilution: In this method, the raw sewage or the treated sewage (or the effluent from treatment plants) is [...]
When sewage is discharged into a natural stream or river, the organic matter present in the sewage gets oxidized by bacteria and converted to simple, inoffensive, stable substances. In this process of oxidation the dissolved oxygen (DO) content of the river or stream water is utilized. Due to this deficiency of dissolved oxygen is created in river or stream water. [...]