Cyanobacterial and microcystins dynamics following the application of hydrogen peroxide to waste stabilisation ponds

摘要

Cyanobacteria and cyanotoxins are a risk to human and ecological health, anda hindrance to biological wastewater treatment. This study investigated theuse of hydrogen peroxide (H₂O₂) for the removal of cyanobacteriaand cyanotoxins from within waste stabilization ponds (WSPs). The dailydynamics of cyanobacteria and microcystins (commonly occurring cyanotoxins)were examined following the addition of H₂O₂ to wastewater withinboth the laboratory and at the full scale within a maturation WSP, the finalpond in a wastewater treatment plant. Hydrogen peroxide treatment atconcentrations ≥ 0.1 mg H₂O₂ μg−1 total phytoplanktonchlorophyll a led to the lysis of cyanobacteria, in turn releasingintracellular microcystins to the dissolved state. In the full-scale trial,dissolved microcystins were then degraded to negligible concentrations byH₂O₂ and environmental processes within five days. A shift in thephytoplankton assemblage towards beneficial Chlorophyta species was alsoobserved within days of H₂O₂ addition. However, within weeks, theChlorophyta population was significantly reduced by the re-establishment oftoxic cyanobacterial species. This re-establishment was likely due to theinflow of cyanobacteria from ponds earlier in the treatment train,suggesting that whilst H₂O₂ may be a suitable short-termmanagement technique, it must be coupled with control over inflows if it isto improve WSP performance in the longer term.