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Aeration

Aeration involves processes that increase the levels of dissolved oxygen (DO) in water which can be achieved through various techniques and technologies. CRS is able to supply aeration equipment or provide a completely engineered solution to meet the client’s needs.

DO can be used to oxidise organics and metals, precipitating the species from water to allow for their filtration or settling. Another use for aeration is the removal of noxious gases such as methane and hydrogen sulphide which cause odour issues and carbon dioxide which affects the water’s pH. Methods for introducing air into water can be separated into three broad categories: surface aeration and sub-surface aeration and aeration towers.

Surface aerators provide highly turbulent mixing, resulting in the formation of a spray that enhances the mass transfer of oxygen to the water by increasing the surface area of the water that is exposed to air.

Subsurface aerators introduce air directly at the bottom of the water body and allow the bubbles to rise through. This can achieved though jet aerators which inject air via a high pressure stream with a venturi, drawing air into the jet via the venturi principle. Coarse and fine bubble diffusers pump air into the bottom of the water causing the formation of bubbles. In coarse bubbling, bubbles are generally >2mm in diameter while bubbles under 2mm diameter are considered fine. Coarse bubbling allows for better mixing but less oxygen transfer, and vice versa for fine bubbling.

Aeration towers utilise packing materials which allow the water to form thin films on their surfaces or small droplets as they fall through, thus increasing the surface area available for contact with air. Water is often introduced at the top of the towers and allowed to trickle through the packing material, while a counter-current air stream is provided by a fan or blower.

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