Empirical model for the autotrophic biodegradation of thiocyanate in an activated sludge reactor

Abstract

Aims: The aim of this investigation was to develop an empirical model for the autotrophic biodegradation of thiocyanate using an activated sludge reactor. Methods and Results: The methods used for this purpose included the use of a laboratory scale activated sludge reactor unit using thiocyante feed concentrations from 200 to 550 mg l )1 . Reactor ef¯uent concentrations of <1 mg l )1 thiocyanate were consistently achieved for the entire duration of the investigation at a hydraulic retention time of 8 h, solids (biomass) retention of 18 h and biomass (dry weight) concentrations ranging from 2 to 4 g l )1 . A biomass speci®c degradation rate factor was used to relate thiocyanate degradation in the reactor to the prevailing biomass and thiocyanate feed concentrations. A maximum biomass speci®c degradation rate of 16 mg )1 g )1 h )1 (mg thiocyanate consumed per gram biomass per hour) was achieved at a thiocyanate feed concentration of 550 mg l )1 . The overall yield coef®cient was found to be 0á086 (biomass dry weight produced per mass of thiocyanate consumed). Conclusions: Using the results generated by this investigation, an empirical model was developed, based on thiocyanate feed concentration and reactor biomass concentration, to calculate the required absolute hydraulic retention time at which a single-stage continuously stirred tank activated sludge reactor could be operated in order to achieve an ef¯uent concentration of <1 mg l )1 . The use of an empirical model rather than a mechanistic-based kinetic model was proposed due to the low prevailing thiocyanate concentrations in the reactor. Signi®cance and Impact of the Study: These results represent the ®rst empirical model, based on a comprehensive data set, that could be used for the design of thiocyanate-degrading activated sludge systems.

Genome‐resolved metagenomics of a bioremediation system for degradation of thiocyanate in mine water containing suspended solid tailings

“…A bacterium of the phylum Deinococcus–Thermus occurred in both the solids 1 and solids 2 samples (Figure ). To our knowledge, this is the first reporting of a Deinococcus–Thermus in bioreactors inoculated with the ASTER ™ microbial consortium (du Plessis et al., ; Huddy et al., ; Kantor et al., ; R. S. Kantor, R. J. Huddy, I. Ramsunder, B. C. Thomas, S. Tringe, R. L., Hettich, S. T. L., Harrison, J. F. Banfield, in review; van Buuren et al., ; van Zyl et al., ). We reconstructed a draft Truepera_1 genome that is 1.22 Mbp in length with 90% of expected single copy genes (Table S1).…”

“…Although SCN − is not as toxic as CN − , it is known to be harmful to humans and aquatic organisms (Boening & Chew, ; Erdogan, ; Shifrin, Beck, Gauthier, Chapnick, & Goodman, ), requiring the use of chemical or biological methods for its removal. The use of microbes for biological remediation of SCN − from contaminated wastewater has been successful at both the laboratory scale (Boucabeille, Bories, Ollivier, & Michel, ; du Plessis, Barnard, Muhlbauer, & Naldrett, ; van Zyl, Harrison, & van Hille, ; van Zyl, Huddy, Harrison, & van Hille, ) and in commercial operations (van Buuren, Makhotla, & Olivier, ). Engineers have developed and commercialized a SCN − biodegradation process known as Activated Sludge Tailings Effluent Remediation (ASTER ™ ) that involves continuous feeding of SCN − ‐containing solutions into aerated bioreactors to promote microbial degradation (van Buuren et al., ).…”

Thermodynamic Data of Fusarium oxysporum Grown on Different Substrates in Gold Mine Wastewater

“…The danger of such waste to both human and ecological systems is well known. Several reports have been published on microbial remediation of industrial wastewater containing cyanide; however, there is minimal commensurate uptake of such technology by the industry despite the LaRonde and Homestake gold mines in Canada, including Gold Fields Limited, demonstrating the feasibility and robustness of such biological process for cyanide remediation [1][2][3]. To date, there are no datasets on physical properties of microorganisms that could be deployed for sustainable environmental engineering applications for free cyanide bioremediation, i.e.…”

Evaluation of the ASTERTM process in the presence of suspended solids

“…The cultivated yeast isolate, Euk#1, is related to a Candida species. Candida humulis has previously been shown to be present in the ASTER™ microbial consortium (du Plessis et al, 2001). To date we have not identified a fungal species closely related to Fusarium oxysporium, within the solids reactor system.…”

“…To date we have not identified a fungal species closely related to Fusarium oxysporium, within the solids reactor system. F. oxysporium has been previously shown to be capable of cyanide degradation as well as being present in the ASTER™ microbial consortium (du Plessis et al, 2001). …”