Anaerobic treatment of complex chemical wastewater in a sequencing batch biofilm reactor: Process optimization and evaluation of factor interactions using the Taguchi dynamic DOE methodology

Abstract

The Taguchi robust experimental design (DOE) methodology has been applied on a dynamic anaerobic process treating complex wastewater by an anaerobic sequencing batch biofilm reactor (AnSBBR). For optimizing the process as well as to evaluate the influence of different factors on the process, the uncontrollable (noise) factors have been considered. The Taguchi methodology adopting dynamic approach is the first of its kind for studying anaerobic process evaluation and process optimization. The designed experimental methodology consisted of four phases--planning, conducting, analysis, and validation connected sequence-wise to achieve the overall optimization. In the experimental design, five controllable factors, i.e., organic loading rate (OLR), inlet pH, biodegradability (BOD/COD ratio), temperature, and sulfate concentration, along with the two uncontrollable (noise) factors, volatile fatty acids (VFA) and alkalinity at two levels were considered for optimization of the anae robic system. Thirty-two anaerobic experiments were conducted with a different combination of factors and the results obtained in terms of substrate degradation rates were processed in Qualitek-4 software to study the main effect of individual factors, interaction between the individual factors, and signal-to-noise (S/N) ratio analysis. Attempts were also made to achieve optimum conditions. Studies on the influence of individual factors on process performance revealed the intensive effect of OLR. In multiple factor interaction studies, biodegradability with other factors, such as temperature, pH, and sulfate have shown maximum influence over the process performance. The optimum conditions for the efficient performance of the anaerobic system in treating complex wastewater by considering dynamic (noise) factors obtained are higher organic loading rate of 3.5 Kg COD/m3 day, neutral pH with high biodegradability (BOD/COD ratio of 0.5), along with mesophilic temperature range (40 degrees C), and low sulfate concentration (700 mg/L). The optimization resulted in enhanced anaerobic performance (56.7%) from a substrate degradation rate (SDR) of 1.99 to 3.13 Kg COD/m3 day. Considering the obtained optimum factors, further validation experiments were carried out, which showed enhanced process performance (3.04 Kg COD/m3-day from 1.99 Kg COD/m3 day) accounting for 52.13% improvement with the optimized process conditions. The proposed method facilitated a systematic mathematical approach to understand the complex multi-species manifested anaerobic process treating complex chemical wastewater by considering the uncontrollable factors.

Effect of Sulfate Loading Rate and Organic Loading Rate on Anaerobic Baffled Reactors Used for Treatment of Sanitary Landfill Leachates

“…An anaerobic sequencing batch biofilm reactor was optimized using the Taguchi experimental design. Improved conditions for CODr (50% increase) were observed at an OLR of 3.5 g.L -1 .day -1 , neutral pH, BOD/COD ratio of 0.5, and low sulfate concentration (0.7 g/L) (Venkata Mohan et al, 2005). That work reached similar conclusions to those presented here: optimal reactor performance is reached at high OLR and low sulfate concentrations.…”

Biomineralization of 2-Chlorophenol in an UASB Reactor with Starch Water as co-substrate

“…The pH is the integral expression of the acid based condition of any anaerobic treatment process as well as an intrinsic index of the balance between the two of the important microbial groups [16] Compared to influent pH (5.7-7.4), the outlet pH (7.5-8.2) was higher. The same results were obtained and reported by Venkatamohan et al (2005) [17]. …”

Integration of acidogenic and methanogenic processes for simultaneous production of biohydrogen and methane from wastewater treatment

“…The system encourages the culture of slow growing organisms and can achieve homogeneous biomass distribution. This leads to improved reaction potential for stable and robust systems which is well suited for treating highly variable wastewater [12,15,[56][57][58][59][60][61]. Further, the selection of effective biomass is possible in this system and the biomass concentration could be uniformly maintained along the height of the bed [57,62].…”