Investigation of the Effect of Initial Biomass on Nitrate and Phosphate Removal from Synthetic Wastewater by Selected Bacteria Isolates

Abstract

Although nitrogen and phosphorus are important nutrients to the existence of living organisms, their presence in excessive amounts in wastewater could have detrimental effects to humans and other living organisms.  The present investigation was aimed at ascertaining the effect of initial biomass concentration on the nutrient removal efficiency of four bacterial species in synthetic wastewater under shaking flasks conditions. Four different initial biomasses [2.91 x 10⁸ cfu/mL, 5.82 x 10⁸ cfu/mL, 8.73 x 10⁸ cfu/mL and 1.16 x 10⁹ cfu/mL (Klebsiella sp.); 6.31 x 10⁸ cfu/mL, 1.26 x 10⁹ cfu/mL, 1.89 x 10⁹ cfu/mL and 2.52 x 10⁹ cfu/mL (Pseudomonas sp.); 1.75 x 10⁸ cfu/mL, 3.49 x 10⁸ cfu/mL, 5.24 x 10⁸ cfu/mL and 6.98 x 10⁸ cfu/mL (Lysinibacillus sp.), and 7.1 x 10⁸ cfu/mL, 1.42 x 10⁹ cfu/mL, 2.13 x 10⁹ cfu/mL and 2.84 x 10⁹ cfu/mL (Staphylococcus sp.)] were used for the study. For nutrient removal studies, the respective initial biomasses of the test isolates were inoculated into flasks containing the wastewater media. Aliquot samples were taken at the beginning of the study and every 24 h for 96 h for the estimation of growth rate, pH, phosphate and nitrate concentrations in the wastewater, using standard methods. The results revealed only slight phosphate decreases in the wastewater after the expiration of incubation. All the test isolates showed significant nitrate removal ability except the Lysinibacillus sp. After 96 h incubation 68.36 to 90.67 %, 91.80 to 95.29 %, 3.20 to 11.48 % and 86.77 to 94.33 % of nitrate was removed in the presence of the Klebsiella sp., Pseudomonas sp., Lysinibacillus sp. and Staphylococcus sp., respectively. The study was able to reveal the phosphate and nitrate removal ability of the isolates at the different initial biomasses used for the investigation.

Keywords: Bacteria, wastewater, nutrient removal, phosphate, nitrate