Evaluation of partial nitrification efficiency as a response to cadmium concentration and microplastic...

The partial nitrification efficiency response to the presence of cadmium (Cd²⁺) and microplastics was investigated. Microplastics polyvinylchloride (PVC) abundance was 0-10,000 particles/L, and Cd²⁺ concentration was 0-10 mg/L. Cd-only inhibited the NH₄⁺-N oxidation rate 1.21, 1.23, and 1.18 times with concentrations at 1, 5, and 10 mg/L, respectively. PVC-only inhibited NH₄⁺-N oxidation rate 1.01, 1.21 and 1.05 times with PVC abundance at 1000, 5000 and 10,000 particles/L, respectively. The ammonia oxidation rate was improved with the co-existence of PVC and Cd²⁺ at the conditions PVC1000 and PVC5000, which could be attributed to the PVC. PVC at 1000 particles/L could act as carrier and mitigate the negative effect of Cd²⁺ to the partial nitrification process. Moreover, the partial nitrification process was largely inhibited with PVC abundance at 10,000 particles/L. First-order kinetic models could simulate the NH₄⁺-N, NO₂^-N, and NO₃^--N changes in the partial nitrification process.