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.

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.

Delipidation is a method of defatting that is generally associated with the removal of residual lipids or lipid groups from matrices in which they are present in minute quantities. The bio-delipidation of protein-rich poultry slaughterhouse wastewater (PSW) pre-treated with a dissolved air flotation (DAF) system was developed using microbial lipases from bacterial strains isolated from the PSW. The efficacy of the bio-delipidation system was quantitatively characterised by comparing the quality parameters i.e. fats, oil and grease (FOGs), turbidity, total suspended solutes (TSS), chemical oxygen demand (COD) and protein concentration of the DAF pre-treated PSW and bio-lipidized samples. As hypothesised, the bio-delipidation system was able to effectively reduce the levels of these quality parameters when crude lipases of Bacillus cereus AB1 (BF3) and Bacillus cereus CC-1 (B30) strains were used. Strain-dependent quality characteristics were also observed in bio-delipidized samples. The study successfully managed to complement physical reduction techniques (DAF) with biological strategies (bio-delipidation) for improved PSW quality, with potential industrial applications.

This study reports on the microbial screening for a bio-delipidation system of lipid-rich slaughterhouse wastewater, and on the optimal conditions for lipase production and activity. In this study, swaps were collected from the poultry slaughterhouse discharge point for screening, isolation and characterisation of lipolytic microorganisms using molecular techniques. Bacillus cereus strains AB1 (BF3) and CC-1 (B3O) were identified using 16S rRNA techniques. Maximal lipase production for both strains was observed between pH 6-8 and 45-60 °C. Optimal lipase activity for BF3 and B30 was achieved at pH 8 and 60 °C, and at pH 8.83 and 45°C, respectively. After partial purification, increased activity was observed for BF3 and B30 strains. Solvents, metal ions and detergents (triclosan and trichlorocarbonilide) affected lipase activity. It was concluded that BF3 and B30 strains were suitable candidates for bio-delipidation systems.

In this study, the use of metallo-phenolic tolerant microbial consortia was proposed for its biosurfactant supported COD reduction, under high metallo-phenolic conditions, with high concentrations of phenol and heavy metals (Zn 2+ and Cu 2+ ) up to 850mg/L and 35mg/L, respectively.Results indicated that the toxicants had insignificant inhibition; albeit, comparative analysis indicated reduced emulsification efficiency of the biosurfactants under high toxicant loading, which will reduce the degreasing capabilities, thus reduced nitrification as the mass transfer will subsequently be reduced. The results showed potential for the consortia to be used in various types of wastewater including phenol and hydrocarbon contaminated water.