Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits

Abstract

Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

Experimental investigation of oxygen transfer efficiency in hydraulic jumps, plunging jets, and plunging breaking waves

“…Liu et al (2004) demonstrated the direct relationship between head loss and turbulence kinetic energy. Ozkan et al (2014) measured the aeration efficiency related to the air-demand ratio and Froude number.…”

The role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency

“…Experimental studies on air‐demand ratio and the oxygen transfer efficiency in closed conduits were carried out by investigators (e.g. Campbell & Guyton, 1953; Escarameia, 2007; Haindl & Sotornik, 1957; Kalinske & Robertson, 1943; Mahmoudi‐Rad & Najafzadeh, 2021; Mortensen, 2009; Mortensen et al, 2011, 2012; Oveson, 2008; Ozkan et al, 2006, 2014, 2015; Rajaratnam, 1962; Shamsaei & Soleymanzadeh, 2006; Sharma, 1976; Speerli, 1999; Speerli & Hager, 2000; Speerli & Volkart, 1997; Stahl & Hager, 1999; Tuna et al, 2014; Unsal et al, 2008, 2009; USACE, 1964; Wisner, 1965). The comprehensive literature search did not identify any published analytical or physical studies investigating the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency.…”

A coupled hydrodynamic‐biokinetic simulation of three‐phase flow in an oxidation ditch using CFD

“…[4][5][6] Suitable design and optimization of this unit are then of crucial importance to the overall efficiency of the wastewater treatment process. [7][8][9] Since aeration is mainly used to enhance the transport of atmospheric oxygen to the mixed liquor to bio-oxidize organic contaminants, modelling studies have been mainly focused on the enhancements made in the bio-oxidization process. [10] Oxidation ditches (ODs) have been extensively implemented in many WWTPs and have proven to be reliable in terms of energy efficiency, low sludge production, resistance to shock load, constant water level, and continuous discharge.…”