Centrifugal & Positive Displacement Blowers

Blowers in wastewater treatment plants function as a good air diffuser system. There are basically two different types of blowers used in today’s treatment plant like the Centrifugal Blower and another type is the Positive Displacement Blower. Centrifugal units are mostly employed in plants whereby the demand exceeds at least 80 cubic meters of free air per minute and this type is often known to emit high-pitched noise unless a silencer is installed.

Blowers must be designed to meet wide range of airflow demands and as such, it is important that regulators must be installed to control the flow. This can be achieved either by using valves at the inlet point, creating a bypass loop line, or by using adjustable diffusers. The workaround of a blower is often compared to that of a centrifugal pump especially on the operating point aspect, which is an intersection between the system curve and head-capacity curve. Performance of a centrifugal blower is often determined by air density whereby at lower temperature, density will increase and thus this leads to higher operating pressure.

Compared to centrifugal types, a positive displacement blower are only used if the need of the system does not surpass the 80 cubic meters of free air per minute limit and for those application that require higher discharge pressure. This type of unit is often selected based on the criteria that wide variation of water level is expected. However, unlike centrifugal blower, control can only be achieved using variable speed drive or another way is to use combined units of positive displacement blowers working in tandem.
Related wastewater management topic: Trickling Filter System

Recommended Engineering Books