Biozeolite capping for reducing nitrogen load of the ancient canal in Yangzhou City

Biozeolite capping for reducing nitrogen (N) load of an eutrophic canal in Yangzhou City was studied. Biofilm formation on biozeolite was cultivated by use of isolated nitrifiers and denitrifiers. Varying conditions including dissolved oxygen (DO) and origins of isolated bacteria were considered in our experiments. Long-term sediment incubation experiment results showed that the reduction efficiency of total nitrogen (TN) of overlying water by biozeolite capping were in the range of 47.61–57.64% under the condition of DO<1 mg L⁻¹. There was no obvious difference in TN reduction efficiency between natural biozeolite (indigenous bacteria) and artificial biozeolite (isolated bacteria). However, the reduction efficiency of TN and nitrate nitrogen (NO₃⁻-N) were respectively in the ranges of 67.38–76.12% and 69.38–76.12% under the condition of DO 1.5–5 mg L⁻¹. The reduction efficiencies of TN and NO₃⁻-N by artificial biozeolite were improved by 25.99–27.25% and 17.50–24.15% respectively than those by natural biozeolite. Moreover, no significant difference was found for reducing N load by the isolated bacteria with different origins. TN contents of surface sediments and ammonia nitrogen concentrations of sediment interstitial water in biozeolite capping systems declined obviously after experiments. Biozeolite capping is an effective technique for reducing N load of the Yangzhou canal.