| Through different working condition experiments, effect of hydraulic loading on antioxidant enzyme (superoxide dismutase, catalase) and digestive enzyme (cellulose, alkaline phosphatase) activities of earthworm in biofilter were studied. The results indicated that antioxidant enzyme and digestive enzyme activities of earthworms responded to hydraulic loading stresses differently. SOD and CAT activities of earthworms increased with the increase of hydraulic loading in the scale of 2.4-6.7 m3·(m2·d)-1, earthworms resisted external environmental stress by coordination function of antioxidation system, so they could survive in different conditions. In addition, digestive enzyme activity, digest ability, sludge reduction and stabilization effect showed excellent correlation (p<0.05). When the hydraulic loading was 4.8 m3·(m2·d)-1, earthworm biofilter showed a high level of AKP, FP and digest rate(41.47%), which was notably better than that of other conditions, sludge and organic matter reduction rate came to the maximum, 48.2% and 65.5% respectively. However, higher level of hydraulic loading ［≥6.0 m3·(m2·d)-1］restrained AKP and FP activity markedly and metabolism level was affected, sludge reduction rate had certain decadence, so it was unfavorable for earthworm biofilter to bring the ecological function into play. At last it is recommended that the hydraulic loading of earthworm biofilter should not exceed 6.0 m3·(m2·d)-1. |
