Biological treatment of wastewater in aeration tanks: Theoretical bases for process calculations

Abstract

This article describes the method, based on the kinetics of enzyme reaction, for calculating treatment rates for wastewater effluents of varied concentrations in mixing aeration tanks and continuous flow aeration tanks. Using this method would make it possible to optimize the parameters of the biological treatment of wastewater. In addition, the authors illustrate that partitioning of the aeration space of the mixing aeration tank in a separate KU‐200 compact installation, which is intended for wastewater treatment from small sources, would make it possible to increase its efficiency by a factor of 1.8.

Intensification of a mixing aeration tank operation by using hydraulic partitioning

“…Scientists don't recommend using a continuous-flow aeration tank without regeneration of the activated sludge for wastewater treatment, having a concentration of organic contaminants (BOD 20 ) of more than 150 mg/L (Henze et al 2002;Voronov 2009). Using the technology of the activated sludge regeneration may allow to increase the concentration of organic contaminants at the continuous-flow aeration tank inlet up to 350 mg/L (Andreyev et al 2017).…”

“…The sludge mixture passed the first cell of biological treatment and enters the second one. Since the concentration of organic contaminants in the sludge mixture in the first cell L out 1 is higher than the concentration of organic contaminants in the sludge mixture in the second cell L out 2 L out 1 > L out 2 , where K p ≈ const , one can record (Andreyev et al 2017) (4)…”

“…The hourly wastewater flow fed into the aeration tank is (Andreyev et al 2017) A concentration of organic contaminants (BOD full ) is L in = 250 mg/L at the inlet of the mixing aeration tank, and it is L out = 15 mg/L at the outlet of the mixing aeration tank. The estimated sludge dose, providing the aeration period value of T a = 11.6 h is a = 1.3 g/L.…”

“…The calculated concentration of organic contaminants in the cells of the partitioned mixing aeration tank is defined as (Andreyev et al 2017):…”

“…where ρ max is a maximum oxidation rate of organic contaminants with the ash-free substance of the activated sludge, mg/(g h); C O is the dissolved oxygen concentration in the sludge mixture, mg/L; K 1 is a constant characterizing the properties of organic contaminants, mg/L; K O is a constant characterizing the impact of dissolved oxygen on the biological treatment, mg/L; L out is a concentration of organic contaminants at the outlet of the mixing aeration tank, mg/L; a is the activated sludge dose accepted on the basis of the efficiency of the secondary clarifiers, g/L; and ϕ is the inhibitory factor of the biological treatment with the activated sludge disintegration products, L/g (Andreyev et al 2017).…”