Oxygen Utilization Rate as a Control Parameter for the Aerobic Stage in Dual Digestion

Abstract

From a study of the performance of the autothermal thermophilic aerobic stage (45 m3) of a full-scale dual digestion plant, operated with pure oxygen, it was found that: (1) VS and/or COD removal are poor parameters for estimating biological heat generation; (2) the biological heat generation is proportional to oxygen utilized at 13.0 MJ/kgO, a value which conforms closely to that obtained from bioenergetics and thermodynamics, (3) the maximum biological heat generation rate was limited by the maximum oxygen utilization rate of the sludge (OURbio), and (4) because the aerobic reactor is oxygen limited, the temperature could be completely and instantaneously controlled with oxygen feed rate up to OURbio; (5) CO2 generation in the vent gas was 0.68 mol CO2/mol O2 utilized instead of 1.0 usually assumed.

Municipal waste sludge digestion in an autothermal aerobic sequencing batch reactor

“…Two are obvious and well documented in previous research works: the concentration of degradable TCOD and oxygen supply and availability (Messenger et al 1990). These two factors can be readily manipulated to achieve successful operation (Messenger et al 1993b).…”

New systematic methodology for incorporating dynamic heat transfer modelling in multi-phase biochemical reactors

“…Aeration is a key factor in aerobic digestion from the point of view of biological reaction and heat balance. If the process is working with oxygen concentrations under the stoichiometric value (oxygen limiting conditions), the oxygen transfer will mark the substrate consumption rate of the system and therefore the sludge heating (Messenger et al, 1990). Thus, the digester temperature can be controlled with the air flow, until the substrate is exhausted or the stoichiometric oxygen value is reached.…”

“…There are several papers which have included temperature prediction in the general model, the studies carried out by Novotny and Krenkel (1973), Argaman and Adams (1977), Sedony andStenstrom (1995), la Cour Jansen et al (1992), Gillot and Vanrolleghem (2003), Makinia et al (2005) and Lippi et al (2009) being some of the most representative works in water line modelling. In the field of municipal sludge digestion, almost all heat transfer models published in literature focus on the representation of the ATAD (Vismara, 1985;Messenger et al, 1992Messenger et al, & 1993Pitt et al, 1994;Lapara et al, 1999;Gómez et al, 2007;and de Gracia et al, 2009), focusing less on anaerobic digestion. All these publications propose a detailed and accurate heat transfer model for a precise prediction of the temperature.…”

On-line monitoring equipment for wastewater treatment processes: state of the art

“…Here, all heat flows in and out of the reactor must be known, including for instance heat transfer through reactor walls, heat loss with the (gas and liquid) mass flows across the reactor boundaries, mechanical heat input and heat exchange with the temperature control system. Systematic overviews of such heat balances are given in Messenger et al (1990) and Van Kleeff et al (1993). The latter authors also focus attention on the problems inherent to this type of "whole reactor calorimetry": changes in heat transfer coefficients as a result of wall growth or changing hydrodynamic conditions and the precautions to be taken when the heat balance is used under dynamic conditions.…”