Aeration systems rely on blowers to move air through the system’s pipework and diffusers and into the biological treatment process. As the industry moves toward more energy-efficient controls and technologies, understanding aeration blower selection and operation is crucial.
A blower and its accessories (such as an intake filter) are only one part of the aeration system that also includes diffusers, pipes, and aeration controls. Most aeration blower equipment falls into one of two main types: centrifugal or positive displacement. The volumetric output of a centrifugal blower is a function of the needed pressure across the blower. In positive displacement blowers, the output is proportional to the blower’s rotational velocity.
Blowers: An Introduction to the Basics of a Flowing Liquid
Effluent quality standards can’t be accomplished or water resource recycling plants (WRRFs) can run efficiently without careful consideration of blower selection and operation. To create an energy-efficient aeration system that dependably meets treatment objectives, blower equipment selection should consider influential loading patterns, ambient variables, operating strategy, and equipment technology.
Technologies for aeration blower tools include:
- Positive Displacement: Two- or three-lobed rotary blowers compress the same amount of air with each rotation. Smaller facilities and those requiring discharge pressures that vary with side water depths often use this technology. When purchasing a rotary lobe blower, shop here to get the whole system in a single soundproof housing.
- Traditional rotary lobe blowers are being replaced with hybrid rotary lobe-screw blowers, which are more recent, feature lobes that are twisted like those on screw compressors, and claim to be more efficient than their predecessors.
Centrifugal blowers with many stages generally feature anything from two to eight separate impellers. The pressure of the air is gradually raised as it travels through the several stages, reaching the desired discharge pressure in the final step.
The wastewater sector has used this technology extensively.
To achieve the necessary pressure at the blower’s discharge, single-stage centrifugal blowers must run at higher speeds despite only having one impeller. The primary distinctions between single-stage machines are the methods used to increase blower speed and the bearings used.
With integral-gear powered blowers, the impeller speed is increased beyond that of the motor by use of a gear box. Read more about impeller speed for to better understand its importance. The driving shafts from the gearbox to the blower are supported by conventional bearings. Guide vanes at the blower’s input and diffuser vanes at the exit provide for volume control.
Its name comes from the fact that a direct-drive blower’s (turbo blower) impeller is connected directly to the drive shaft of the motor. With a variable frequency drive, blower output is adjusted. Turbo blowers, which combine air and magnetic bearings, have been on the rise over the last decade.
In the past, blower sizing was often done using worst-case site parameters, including the worst-case flow and load characteristics. Traditional blower designs have only concerned themselves with the oxidation of biological oxygen demand (BOD) and maybe the removal of ammonia, but have not given any thought to the nutrient oxidation. In most cases, operating circumstances of a facility fall well short of those assumed during design, leading to a number of inefficiencies.
Nature of the Environment
The location and climate of a wastewater treatment plant have a major impact on the efficiency of the associated blower equipment. Selecting an aeration blower requires taking into account a broad variety of environmental factors. Some examples of these environmental factors are:
- The amount of oxygen present in a given volume of air varies with the site’s elevation. At higher elevations (where the air is “thinner”), the mass of oxygen in the atmosphere is less than it is at sea level. To transport oxygen at higher heights, the apparatus must create more air.
- Due to the lower density of air at higher temperatures, less oxygen is carried in a given volume of air. More space is needed for the same amount of oxygen as the temperature rises. The effectiveness of a blower may change significantly depending on the time of day, the season, and other environmental factors.
- The amount of compressed air (https://en.wikipedia.org/wiki/Compres) needed is affected by the relative humidity because water vapor in the air is measured. Relative humidity tends to be highest in the morning and gradually drops over the day, reaching its lowest point in the afternoon.
- The blowers have to adjust their output throughout the day to account for the changing flows and loads.
- The pressure of the blower’s output is affected by the depth of water in the aeration tanks’ side walls.
Problems with Operations
Depending on its specific needs, each WRRF has a unique blower operating strategy. Aeration requirements for aerobic biological therapy might vary from one situation to the next, hence blowers should be adjustable to provide the necessary amount of air.