Treatment of toxic organic wastewaters with chemical oxidation, carbon adsorption and bioaugmentation

The research was designed to treat toxic organic wastewaters containing resorcinol, vanillin and salicylic acid at optimum conditions using chemical oxidation, activated carbon adsorption and bioaugmentation. The parameter for determining treatability was total organic carbon (TOC) removal. Chemical oxidation was carried out using two oxidants, Fenton's reagent (H₂O ₂ and FeSO₄) and potassium permanganate. Carbon adsorption involved using six activated carbons: Norit PAC 20B, Norit E Supra USP, Darco KB, Norit SX2, Darco S-51 and Hydrodarco C. Bioaugmentation involved using two LLMO types, E-1 and C-1. The effect of sequence in the arrangements of the three treatment processes was determined. Kinetics analyses by time and curve fitting methods were used in determining the reaction rates and orders.; The results showed that the highest TOC removal percentages of 72.77%, 73.93% and 79.91% were achieved using Fenton's reagent with resorcinol, vanillin and salicylic acid respectively. With the KMnO₄ highest TOC percentage removal for resorcinol, vanillin and salicylic acid were 89.61%, 75.15% and 80.43% respectively, however large sludge volumes were accumulated. Bioaugmentation was ineffective in treating the three organic compounds. Using the Langmuir, Freundlich and BET isotherms to determine carbon adsorption capabilities, Norit PAC 20B, Norit SX2 and Norit E Supra USP performed better than the other activated carbons in the removal of the organic compounds during activated carbon treatment. The X/m values (weights of organic compound adsorbed per unit mass of the activated carbon) determined could be used in the design of powdered activated carbon systems. The application of chemical oxidation using Fenton's reagent followed by activated carbon adsorption may be the best treatment arrangement for the three organic compounds. Kinetics data determined by time and curve fitting analyses showed that the majority of the reactions had reaction orders greater than 2, or were second-order reactions. The reaction rate values varied widely. In cases where the results of the two kinetics analyses did not agree, the choice of an analysis with a higher correlation coefficient may be employed. The kinetics results could be used in the design of activated carbons reactor volume.