For wastewater treatment facility, odour control unit capacity is estimated based on the two parameters: · The Air volume of odour causing process tanks · Air exchange factors to be considered for the process tanks While estimating the air volume of the process tanks, if it is a fixed water level tank, freeboard air volume shall be considered; if it is fluctuating water level, it is advised to consider the air volume from the lowest water level . Air exchange factors are very critical in designing the odour control system capacity and which impacts the size and efficiency of the odour removal. Most of the regional municipalities have made clear guidance on the air exchange factors to be considered while estimating the odour control system capacities. Typically, for inlet works, air exchange factors are considered in the range of 12-15 of the volume of the air. And for the sludge treatment facility, it will be 6-...