Simultaneous Purification Of Sediment And Overlying Water With Intermittent Disturbance In Contaminated Water

Surface water was contaminated seriously in China at present, almost all shallow rivers and lakes are polluted, which harmed the water environmental health and could be the pollution sources to the big area water fields. Thus the restoration of shallow rivers and lakes is the important research subject in the environmental protection field. The existing water restoration technology can be divided into two kinds: one kind is aimed to the contaminated overlying water, such as ecologic water compensation, artificial reaeration etc, the other kind is aimed to the contaminated sediment,such as sediment dredging, sediment masking etc.these techniques have revealed some flaws: single bject, low efficiency and the effect lasted short time. So this paper explored new water restoration technology,and carried out experimental research of the new technology.A new polluted rivers and lakes repairing technology: Intermittent Strong Disturbance Technology was put forward, this technology was aimed to force the sediment which contains organic compounds and microorganism resuspend,then dispersed in the overlying water,extended the contact area of sediment and overlying water, promoted the material exchange,changed the distribution of dissolved oxygen, enhanced microorganism activy, and the contaminated overlying water and sediment can be purified simultaneously.The pollutant contents of overlying water, pollutant contents and morphological changes of sediment were studied by changing the disturbance velocity, duration, frequency and tempreture, different polluted rivers and lakes were tested with various optimum parameters of every testing item,then field test was carried out,and to apply the experiment results to projects,a contaminated water restore equipment was designed.The pilot tests showed that: 1) the concentration of pollutants of overlying water had the change law of quick increase-slow decrease-steady state. this was mainly because the pollutants released into the overlying water,and the microorganism proliferated, then the microorganism adsorpted and degradated the pollutants in overlying water and sediment,then reached the dynamic equilibrium of release and degradation. 2) the velocity and the duration of disturbance had great influence on the water restoration effect, the faster the velocity was and longer the the duration of disturbance, the better purifying effect of overlying water and sediment,the economic and reasonable velocity and the duration of disturbance was90r·min-1 and 60 s. 3) the simultaneous purification efficiency of sediment and overlying water increased with temperature raised, when the water temperature was 5~20℃. However, the water temperature of 20~30℃ had no significant effect on the simultaneous purification efficiency of sediment and overlying water, so the selected temperature was 20℃. 4)perturbation frequency had little influence on this technology. 5) explored the purification effect with the optimal parameters, the results showed that the removal of COD and NH4+-N of overlying water could reach 75.2% and 58.1%, DO could be above 5.00mg·L-1 from below2.00mg·L-1, the removal of SCOD and NH4+-N of sediment could reach 76.8% and 70.0%respectly, then the contaminated overlying water and sediment were purified simultaneously.Field experiment was carried out on the base of the good results of laboratory experiment,the field experiment showed that the the removal of COD and NH4+-N of overlying water in Wanjia River were 65.7% and 76.6% respectly, the removal of SCOD and NH4+-N of sediment in Wanjia River were 76.4% and 78.9% respectly, removal of COD and NH4+-N of overlying water in Dongchang River were 72.0% and 82.9% respectly, the removal of SCOD and NH4+-N of sediment in Dongchang River were 84.2% and 68.4% respectly, so the Intermittent Strong Disturbance Technology could purfy the contaminated overlying water and sediment simultaneously.A contaminated water restore equipment was designed based on the systems theory,after the functional analysis,an optimal scheme was chosen from many schemes,and structural design of the boat was done based on the optimal scheme,the contaminated water restore boat can disturb the sediment, reap the aquatic, collect the floats,so the boat not only can puer water,also can remove the aquatic and floats,use the sediment as fertilizer,and the structure of the boat is compact,it needs less energy and it can be handled easily.