[Effect of different combination system of constructed wetland on zooplankton community structure].

The effect of the different combination system of constructed wetland on zooplankton community structure was studied with different hydraulic loading [0.6 m3 x (m2 x d)(-1), 0.8 m3 x (m2 x d)(-1), 1.0 m3 x (m2 x d)(-1]. And the seasonal change of the effect was measured with the same hydraulic loading. The results show that different combination system with hydraulic loading 0.8 m3 x (m2 x d)(-1) on zooplankton community structure is more effective than others; the effect in spring, summer and autumn are more notable than in winter, otherwise the effect in autumn is the most notable; the effect on macro-zooplankton is more obvious than on micro-zooplankton and there are some species in the effluent water of wetland but not in influent water. Ponds of the systems weaken the effects on zooplankton community structure and the effect of combination system (down-flow --> aerobic and anaerobic pond) is the worst of all combination system, and in contrast to others down-flow --> up-flow --> horizontal-flow wetland and down-flow --> horizontal-flow wetland present distinct effects on zooplankton.

[Comparison of algal removal efficiencies in different ecological treatment systems and their combinations].

The algal removal efficiencies and their trends of 8 experimental ecological treatment systems, which belonged to 5 groups, were studied under different hydraulic loading rates (HLR). The algal removal efficiencies were compared according to the seasonal changes under the optimum HLR. Gravel-bed horizontal-flow wetland, down-flow wetland, up-flow wetland, aerobic ponds or facultative ponds combined these systems. The results show that the best HLR is 0.8m3/(m2 x d) in all the experimental systems. The systems including aerobic pond and down-flow wetland show a stronger resistance to hydraulic shock loading, as well as horizontal-flow wetland. The algal removal rates of all the systems peaked to over 94% in summer and bottomed in winter that varied from 34% to 90%. It was the combined form that determined the removal efficiency of the ecological treatment systems. The combination system of down-flow and up-flow wetland present the highest capacity of algal removal efficiency and lower seasonal fluctuation, while the gravel-bed horizontal-flow wetland system present the lowest efficiency and higher seasonal fluctuation.

[Temporal and spatial characteristics of substrate enzyme activities and bacteria physiological groups in constructed wetland].

Six enzymes and five bacteria physiological groups from the substrate (soil) of integrated vertical flowing constructed wetland are chosen to study temporal and spatial characteristics. The research results show that significant differences existed in each enzyme during different months (p < 0.05). The enzyme activities of cellulase, protease and phosphatase were significantly higher in June, September and December than those in March; The enzyme activity of beta-glucosidase in June was significantly higher than those in other months; While urease activities in both September and December were extremely significantly higher than those in March and in June (p < 0.01); But the dehydrogenase was different from the above-mentioned enzymes, which had higher enzyme activities in June and in December than in March and in September. Compared with the temporal characteristics, the spatial characteristics of all six enzymes show consistency: the enzyme activities in the down-flow chamber were significantly higher than those in the up-flow chamber (p < 0.05), and all of the enzyme activities in both chambers were relatively lower with the increasing depths of substrate layers. The numbers of bacteria physiological groups were at peak in June and September and their spatial characteristics were the same with enzyme activities.

[Nitrification and denitrification in the integrated vertical flow constructed wetlands].

Nitrification and denitrification in the different layers of the integrated vertical flow constructed wetlands (IVCW) are studied. The results show the constants rate of nitrification and denitrification in the strata of IVCW were 0.01 - 6.35microg x (gxd)-1 and 3.37 - 4.19microg x (gxd)-1 respectively. The most probable number (MPN) method are employed to determine the number and distribution of nitrifying and denitrifying bacteria in the strata of the system. The results show that the numbers of nitrifying and denitrifying bacteria were 7.5 x 10(3) - 1.1 x 10(5) MPN x g(-1) and 7.5 x 10(6) - 1.1 x 10 MPN x g(-1) respectively. The positive correlation between bacteria and their action was obvious (r = 0.9661, p < 0.001, r = 0.7722, p < 0.025). It is also observed that the number of nitrifying bacteria and nitrification rate was decreased along the direction of the water in the IVCW, while denitrifying bacteria and denitrification rate was increased. And there was the significant negative correlation between nitrification and denitrification rate(r = -0.9776, p < 0.001).

[Studies on clogging of the constructed wetland].

The parameters of substrate related to clogging, such as the grain size, the filtration rate and organic substance in the substrate, were investigated in the integrated vertical-flow constructed wetland (IVCW). The substrate of IVCW was collected by a specific sampling tube in situ and the infiltration experiment showed that the filtration rate of substrate increased with the depth of substrate and the minimum filtration rate existed 15-30 cm below the surface of substrate. The amount of organic substances in upper 15 cm layer of the substrate was limited and even less in deeper layer after fifty two-month running, and this revealed that IVCW was operating steadily and no clogging was observed. Considering the factors related to clogging, the strategy to prevent and recover the clogging phenomenon was put forward.