Lead Inhibition on Urea Hydrolyzing Microorganisms Under Batch Conditions

ABSTRACT

Lead, Pb(II), inhibition of microbial calcium precipitation by ureolytic microorganisms was carried out with a glucose containing mineral medium under batch conditions over an incubation period of 120 hours. Substrate removal rate fitted a zero order up to 70^th hour and first order kinetic after that time for all samples containing lead concentrations of 0–64 mg/L. The increase of Pb(II) concentrations from 0 to 64 mg/L reduced constant of substrate degradation rate from 10.26 to 4.04 mg glucose/L h, and from 0.027 to 0.005 1/h for zero (k₀) and first order kinetic constant (k₁), respectively. The Pb(II) at concentration higher than 16 mg/L mainly inhibited both substrate removal and nitrification process. Although nitrification was inhibited at higher concentrations of lead, its inhibition caused precipitation of calcium due to high pH and alkalinity levels in the samples. As a result that a modified Monod inhibition model was applied to BOD data, BOD removal rate inhibited non-competitively. The non-competitive inhibition constants (K_I) were 10.4 mg/L for K_S, and 37.3 mg/L for R_max at Pb(II) concentration of 64 mg/L.

Keywords:

• inhibition
• lead
• non-competitive
• ureolytic microbial activity
• calcium precipitation