COD (Chemical Oxygen Demand) of Raw Municipal Sewage

COD (Chemical Oxygen Demand) is a measure of the amount of chemical oxygen required to oxidize all the organic and inorganic compounds in water. Raw municipal sewage is the untreated wastewater that is collected from households, institutions, and industries through a network of sewer pipes. The COD of raw municipal sewage can vary depending on the source and the level of treatment it receives.

Range of COD in Raw Municipal Sewage

The range of COD in raw municipal sewage is an important parameter to determine the pollution level of the wastewater and the treatment required to make it safe for discharge into the environment. The correct option for the range of COD in raw municipal sewage is option 'C', which is 90-120 mg/litre. This range is based on the average values of COD in raw municipal sewage collected from different sources and locations.

Factors Affecting COD in Raw Municipal Sewage

The COD of raw municipal sewage can be affected by various factors such as the type and quantity of organic and inorganic compounds present in the wastewater, the pH, temperature, and the time of collection. The presence of high levels of organic matter such as food waste, human waste, and industrial effluents can increase the COD of raw municipal sewage. Similarly, the presence of inorganic compounds such as heavy metals, salts, and ammonia can also contribute to the COD value.

Importance of Measuring COD in Raw Municipal Sewage

Measuring the COD of raw municipal sewage is essential to assess the level of pollution and the treatment required to make it safe for discharge. It helps in designing and operating the wastewater treatment plants to achieve the desired level of effluent quality. The COD value is also used to calculate the chemical dosages required for the treatment process and to monitor the performance of the treatment plant.