Isolation of high-salinity-tolerant bacterial strains, Enterobacter sp., Serratia sp., Yersinia sp., for nitrification and aerobic denitrification under cyanogenic conditions.

Cyanides (CN(-)) and soluble salts could potentially inhibit biological processes in wastewater treatment plants (WWTPs), such as nitrification and denitrification. Cyanide in wastewater can alter metabolic functions of microbial populations in WWTPs, thus significantly inhibiting nitrifier and denitrifier metabolic processes, rendering the water treatment processes ineffective. In this study, bacterial isolates that are tolerant to high salinity conditions, which are capable of nitrification and aerobic denitrification under cyanogenic conditions, were isolated from a poultry slaughterhouse effluent. Three of the bacterial isolates were found to be able to oxidise NH(4)-N in the presence of 65.91 mg/L of free cyanide (CN(-)) under saline conditions, i.e. 4.5% (w/v) NaCl. The isolates I, H and G, were identified as Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Results showed that 81% (I), 71% (G) and 75% (H) of 400 mg/L NH(4)-N was biodegraded (nitrification) within 72 h, with the rates of biodegradation being suitably described by first order reactions, with rate constants being: 4.19 h(-1) (I), 4.21 h(-1) (H) and 3.79 h(-1) (G), respectively, with correlation coefficients ranging between 0.82 and 0.89. Chemical oxygen demand (COD) removal rates were 38% (I), 42% (H) and 48% (G), over a period of 168 h with COD reduction being highest at near neutral pH.

Optimisation of bioflocculant production by a biofilm forming microorganism from poultry slaughterhouse wastewater for use in poultry wastewater treatment.

Poultry slaughterhouse wastewater contains nutrients that are sufficient for microbial growth; moreover, the wastewater has microorganisms which can be harnessed to perform specific functions. Additionally, these microorganisms can grow either in planktonic (free floating) mode or sessile (attached) mode. This study focused on the optimisation of bioflocculant production by quantifying flocculation activity, determined using kaolin clay (4 g/L), by isolates prevalent in poultry slaughterhouse wastewater. Subsequent to their identification and characterisation, six bacterial strains were initially isolated from the poultry wastewater. Although all the isolated microorganisms produced bioflocculants under different conditions, i.e. pH and temperature, the strain that produced bioflocculants with a higher flocculation activity was isolate BF-3, a Comamonas sp., achieving a flocculation activity of 93.8% at 32.9 °C and pH 6.5. Fourier transform infrared spectroscopy (FTIR) analysis of the bioflocculant of the isolate, showed the presence of hydroxyl, carboxyl, alkane and amine functional groups, an indication that the bioflocculant was a protein constituent.