The Effect of Pb2+ Short Term Stress on the Anammox Biomass—A Batch Test Experiment

Abstract

The anaerobic ammonium oxidation process for treating industrial wastewater is widely preferred since Anammox bacteria has been discovered, due to energy savings and cost reduction comparing to classical biological methods. However high concentration of heavy metals contained in such type of wastewater is well known inhibitor for biological processes and may limit the bacteria activity, as well as worsen the effectiveness of wastewater purification. The present state of the art shows that high concentration of certain heavy metals (Pb2+) can be found in municipal waste landfill leachates, therefore their negative effect may occur. The main goals of this research were to: (a) to study the negative effect of Pb2+ on the Anammox process in short term exposures. The inhibition of lead salt on the Anammox bacteria activity and nitrogen removal rate were determined by batch test, based on gas measurements procedure. Inhibition effects were monitored over 80 min experimental runs. Also, the kinetic parameters of the inhibition were investigated. A non competitive inhibition model successfully described the relationship between microbial inhibition and metal concentration. Data has shown that Pb2+ is toxic for Anammox bacteria biomass. The results showed that lead caused 16.2% of the Anammox activity decrease in highest tested concentration of 10 mg L–1 of Pb2+. However, the 50% inhibition has not been reached the IC50 has been calculated at 39.94 mg L. It was also suggested that long term exposure on the heavy metal presence might be more toxic. Thus, the soluble concentration of lead should be monitored on wastewater treatment plants not only before applying Anammox process to the treatment plants, but also during their operation to prevent negative changes in the processes. Also, further investigation should be introduced to understand the matter of the toxicity and the possibility to carry out the process in the heavy metal presence.