[Study on running characteristics of aerating subsurface flow wetlands].

Aim at the low dissolved oxygen concentration and nitrogen removing efficiency in constructed wetlands, the running parameters of aeration measure, influence on plants and bacteria, the dissolved oxygen concentration and purifying efficiency after aeration were studied. The results show that aeration should be run in the forepart of wetland. The best gas-flow ratio is 6. Continuous aeration is adopted. The influence of aeration on plants in wetlands is inconspicuous. The quantity of nitrifying bacteria and denitrifying bacteria are increased. Aeration improves the oxygen condition, which is under 0.6 mg/L before aeration but over 1 mg/L after aeration. The purifying efficiency of wetlands is improved, removing efficiency of organic matter increases 10%, and removing efficiency of total nitrogen is higher than 60%. So aeration has the value of research and application.

[Study on the oxygen condition in subsurface flow wetlands in operation].

Horizontal flow wetlands with various kinds of plants grown were studied on their operation characteristics and oxygen condition in treating the sewage out from the primary sedimentary basin. The rules of oxygen condition changed with space and time were studied. Researches showed the oxygen concentration was low in wetlands, and it appeared as a rule that low in both ends, but high in middle of beds. It descended in upright direction. The oxygen concentration changed with seasons as summer > spring > autumn > winter. In one day, the highest oxygen concentration appeared on 14:00, and the concentration was higher in forenoon than afternoon. Reed > canna > camellia > dracaena sanderiana > ipomoea aquatica forsk by comparison of ability of oxygen supply. Experiments demonstrate that the study of oxygen condition in constructed wetlands is propitious to reveal the purifying mechanism of wetlands and improve the purifying efficiency.