Kinetic Study and Modeling of Aerobic Biological Oxidation of Organic Wastewater

Abstract

The complex organic wastewater from agrochemical industry consists of a large number of solids and dissolved compounds. For the design and scale-up of any activated sludge reactor, it is desirable to know the kinetics of oxidation, which strongly depends upon the nature of wastewater and the microorganism. In the present work, the kinetics of aerobic biological oxidation of an agrochemical plant waste is investigated, having initial COD of 800-1200 mg/L. Experiments are performed at five different dissolved oxygen (DO) levels; viz. (i) 1.5 to 2.5 mg/L, (ii) 2.5 to 3.5 mg/L, (iii) 3.5 to 4.5 mg/L, (iv) 4.5 to 5.5 mg/L, and (v) 5.5 to 6.5 mg/L. For each DO level five mixed liquor suspended solids (MLSS) are studied in the range of 6000-20000 mg/L. The maximum percentage reduction of COD is 74.1%, 74.8%, 89.9%, 73.3% and 89.6% at different DO levels of 1.5-2.5 mg/L, 2.5 to 3.5 mg/L, 3.5 to 4.5 mg/L, 4.5 to 5.5 mg/L, and 5.5 to 6.5 mg/L and MLSS concentrations from 6000 to 20000 mg/L, respectively. An attempt is made to propose the kinetics of substrate utilization that does not actively support growth of organism. A kinetic model is proposed to understand the effect of DO and MLSS concentration.

Kinetic studies on agrochemicals wastewater treatment by aerobic activated sludge process at high MLSS and high speed agitation

“…The previous experiments [16] showed that a DO level of 2.5 mg L À1 and an MLSS concentration of 9000 mg L À1 have resulted in the maximum COD reduction of 74.77% as shown in Table 3.…”

“…The oxygen transfer was sufficient by surface aeration and no air sparging was needed. Further, negligible foaming was observed [11,16,22,23]. Table 6 shows the effluent analysis indicating TN deficiency for aerobic suspended growth process, whereas the amount of TP was sufficient.…”

“…The treatment rates can be expressed as a function of instantaneous substrate concentration based upon the nature of substrates having different degradation profiles and concentration of micro-organisms. In the literature a number of such models are available [10][11][12][13][14][15][16]. The total rate of substrate consumption can be obtained for growth of bacteria metabolizing one compound using other low concentration compounds by the following equation [13]:…”

“…(6) particularly incorporates the effect of the initial COD (S 0 ) of the system, the effect of DO and MLSS of the system, on substrate consumption rate [10,11,16]. When the DO level is constant, Eq.…”

Performance appraisal of microbial inoculants treating polluted surface water through bench‐scale investigation

“…32 Several previous studies also demonstrated the evaluation of the kinetic coefficients for various wastewater treatments. 39,96,97 Kinetic coefficients for a wastewater treatment system at different VSS concentrations were determined in a study by Karkare et al 98 In research conducted by Naghizadeh et al, 99 the kinetic coefficient for the Monod equation was estimated in a submerged membrane reactor used to treat sewage. The measured values for k d , Ks, k and Y were 0.51 (day −1 ), 65.5 mg L −1 , 1.78 (day −1 ) and 0.6 mgVVS mgCOD −1 , respectively.…”