Iranian Journal of Chemical Engineering (IJChE)

Abstract This investigation was designed to evaluate the effects of bioaugmentation on maintaining the system stability under shock loading conditions, standardizing the effluent, and improving the sludge settlement. In this study, phenol was chosen as a model of mono-aromatic compounds which are found commonly in many industrial wastewaters, especially petroleum refineries and the petrochemical industry in Iran. Impacts of bioaugmentation with the best isolated microorganism on the system performance facing sudden toxic shock were investigated after acclimatizing the system with phenol, isolating the phenol degrading microorganisms, and selecting the best phenol degrading strain. Results indicated that this method was improved the efficiency of the system under shock loading from 30% to 94% and SVI from 333 ml/g to 80 ml/g. The effluent was standardized after bioaugmentation at a minimum HRTs of 10, 10, 12 and 24 h, respectively, and at influent COD of 800, 1000, 1500 and 2000 mg/l. The system efficiency and SVI were located in an average range of 99.4-99.9% and 50-71 ml/g, respectively, and the sludge growth was good, even under high organic loading rates after bioaugmentation. In conclusion, bioaugmentation could be used as an effective and efficient method to improve a CAS process facing sudden toxic pollutant shock loading.

Abstract  A case study is presented in which two modifications of activated sludge treatment of complex chemical wastewater are experimentally compared: a combination of common activated sludge with powdered activated carbon treatment (PACT), and bioaugmentation of activated sludge treatment (BAST). Industrial wastewater of Pars Oil Refinery that was passed through an oil recovery stage was used to investigate the effect of furfural on two treatment processes in the range between 100-2000 ppm. Furfural was added manually. For comparison, furfural, COD, MLSS (Mixed Liquor Suspended Solids) concentrations and SVI (Sludge Volume Index) were measured daily. The results show a little higher COD removal efficiency in PACT system and the same furfural removal in both methods. But, it should be mentioned that at low HRT (Hydraulic Retention Time), BAST system showed better results in both furfural and COD removal than PACT system. SVI measurement shows that settability of effluent sludge in BAST system was always better than in PACT system. Because of rapid growth of microbial biomass in BAST system, the MLSS concentration in this modification was higher than in PACT system and in this way, BAST system has a lower requirement to return sludge than PACT system. Finally, it could be concluded that BAST system may be an attractive alternative to existing PACT system and if the former is used, it will result in both high performance and optimum conditions with economical operation.