Since the gas:water ratio was 5:1, DO in water in the
bio-contact oxidation tank was high (over 3 mg/L). In
this oxygen-enriched condition, the biofilms on the waste
oyster shell were mainly composed of oxygen-enriched
biofilms. Thus, preliminary analysis of the pollutant degradation
mechanism on theory indicated two processes. The
first process involved the pollutants including organic matter,
ammonia, etc., adhering on the biofilms. The second
process was that these pollutants adhering on biofilms were
degraded, absorbed and metabolized by the microbes in the
biofilms.