The Study Of Different Operation Modes On Vertical-flow Constructed Wetland Purifying The Higher Polluted River Water And The Characteristic Analysis

Vertical flow constructed wetland is more and more popular, that’s because its higher land utilization efficiency and decontamination ability in three-dimensional,vertical flow constructed wetland can be divided into continuous flow and tidal flow according to operation mode, the former’s defect cannot meet the system’s oxygen desire, the overall environment is anoxic and anaerobic, thus overall performance was limited, especially for serious eutrophication water treatment; tidal flow constructed wetland simulate the tidal rise and back, the way of "rapid water distribution uniformity,natural gravity drainage" enhanced the oxygen environment; in addition, the vertical flow constructed wetland has a greater resistance to the waste water load, so this paper tries to use this method to purify higher polluted river water.In order to study the constructed wetland in purifying higher contaminated water performance and provide theoretical thesis and data support for the application in low temperature region, we assembled a vertical flow constructed wetland system experiment device, the research content is as follows:(1)DO change characteristics in tidal and continuous running;(2)SS, organic matter, nitrogen and phosphorus removal performance in tidal and continuous running;(3) the characteristics of nitrogen and phosphorus removal in low temperature(10℃ or less)in different operation modes;(4)using statistical methods to analyze main effect factor in nitrogen and phosphorus removal in vertical flow constructed wetland system.The results are as follows:(1)the tidal mode greatly improves the oxygen concentration of constructed wetland system, a large amount of oxygen into the waterwhich is "split into pieces" well, its dissolved oxygen level can get very high naturally;drainage quickly can also bring oxygen into the deeper layer of the matrix,strengthening the constructed wetland contact with air; tidal mode of water can create the aerobic and anaerobic environment, provide suitable conditions for microbial life activities and optimize the performance of constructed wetland;(2)during the whole experiment, the water loading has strong fluctuated, but compared with continuous flow, the tidal flow constructed wetland has better removal effect and better resistance on loading changing, under continuous flow operation mode,SS, TN, NH4+_N and TP, PO43-_P, COD and BOD5 average removal rate is 90.80%,17.60%, 34.03%, 65.62%, 37.20%, 75.80% and 37.20%, respectively; under the tidal flow operation mode, SS, TN, NH4+_N and TP, PO43-_P, COD and BOD5 removal efficiency gradually decreased with the extension of time and eventually tend to maximum, the finally removal rate is 90.48%, 37.60%, 51.60%, 54.11%, 41.38%,77.11% and 41.38%, respectively;(3)under the condition of low temperature(10 ℃ or less), the effect of nitrogen and phosphorus removal in three kinds of operation mode(continuous flow, single stage tidal flow and multistage tidal flow) is:single stage tidal flow are better than continuous flow in nitrogen remove, multistage tidal flow is better and stable than single stage tidal flow in nitrogen remove; for phosphorus, tidal flow efficiency drops compared with continuous flow, in continuous flow operation, TN, NH4+_N, TP and PO43-_P average removal rate is 1.5%, 1.1%, 62.8% and 1.1%, respectively, in single stage tidal flow operation, TN, NH4+_N and TP and PO43-_P average removal rate is 16.5%, 33.2%,39.2% and 33.2%, respectively; in multistage tidal flow operation, TN, NH4+_N, TP and PO43-_P average removal rate is 37.2%, 89.3%, 57.5% and 89.3%, respectively;(4)using the method of statistical analysis-redundancy analysis(RDA), taking an example of nitrogen and phosphorous, concluded that: the water environment influence factor in nitrogen and phosphorus removal including SS, carbon source concentration and temperature, and they has a positive correlation with TN removal, in turn, DO showed a negative correlation with TN removal; ORP, DO has a positive correlation with NH4+_N removal, p H, SS has a positive correlation with the TP removal; p H and PO43-_P removal were positively correlated and the correlation is very significant.