Effect Of Filler And Structure Form On River Water Purification Ability In Gabion Revetment

The study investigated the quantificational effect and the mechanism of three substratesincluding granite rubble, gravel and waste building blocks, and three structure form includingvertical, stepped and fish nest's type on river self-purification in Gabion revetment. The effectof three structure form on flow was also investigated based on River2D software.The results and conclusions are as follows:(1) With flowing26days under velocity of0.015m/s and hydraulic retention time of135s, N, P and organic compound removal rates by all the substrates increased gradually invarying degrees. NH3-N and organic compound removal rates by gravelmaintained at a highefficiency, among which the removal rates of NH3-N,TOC and DOC were up to65.26%,71.06%and78.06%respectively after operated26days. The removal rate of TP by graniterubble, gravel and waste building blocks reached89.20%,91.05%and94.71%respectivelyafter operated12days.(2) Lipid phosphorus contents and enzyme activities of microbial film (exceptphosphatase activity) by gravel were significantly higher than the other two substrates(p<0.05), the higher biomass and enzyme activities enhanced removal efficiency of nitrogenand organic compound.(3) With flowing26days under velocity of0.015m/s and hydraulic retention time of135s, N, P and organic compound removal rates by three structure form increased gradually invarying degrees. N, P and organic compound removal rates by gravel maintained at a highefficiency, among which the removal rates of NH3-N,TP, TOC and DOC were up to52.21%,65.36%,54.67%,48.21%respectively after operated26days.(4) Compared to the stone masonary river, the Gabion river with gravel s substrates couldreduce the river's flow rate,which the maximum flow rate reduced from0.96m/s to0.94m/swhen river flow at20m3/s and water depth at2.5m. For the three different structure forms ofGabion revetment river, the maximum flow rate had not changed, but each node of the river'sflow rate had changed, the size order of flow in central river was: vertical> stepped>fishnest's. (5) Taking the impact of self-purification capacity on river into consideration, theoptimal scheme would be using graver as substract and the type of fish nest as structure inGabion revetment.