Study On The Purification Of Urban River By Hydrolysis Acidification-Composite Flow Constructed Wetland

With the rapid development of economy, the pollution of urban river is gettingworse and worse. Constructed wetland as an ecological purification method has theadvantages of economical,environmental and low energy, and has a good ecologicalbenefits, etc. Use constructed wetland treat the contaminated river water has someadvantages, however, the long-term run of constructed wetland will exist seriouscongestion problems, therefore this study proposed using hydrolysis acidificationintensive pretreatment to reduce the pollutant loads of wetland and improve theremoval efficiency of the system, and at the same time prevent clogging.In view of the river pollution status in Chinese cities, this study choosed an urbanriver in Nanning City, Guangxi Province, to make experimental study, use the majorscience and technology sub-project of the research and demonstration of urbanblack-odor river exogenous block and ecological purification key technology as thebasis, combined process of hydrolysis acidification-composite constructed wetland iscarried out in a pilot study in order to provide a reference for follow-up projectdemonstration and the governance of the urban river. The main content of this studyincludes: studied the removal efficiency of the combined process and the effects ofhydraulic loading; studied the impact of different types of wetland,plants and fillers onthe removal efficiency; investigated the removal of loading by the hydrolysisacidification strengthen pretreatment.The results showed that:In this experiment, directly used the pending river as startup water, have shownthat the gradient concentration of water to start the reactor is feasible.Maximum abatement in permanganate-index by the pretreatment hydrolysis andacidification is51.07%, TP is31.25%, ammonia nitrogen is7.72%, TN is20.97%,analysis can be found that in the system there is a certain contribution to the removal ofpermanganate-index,TP, TN by hydrolysis acidification, but did not remove theammonia nitrogen, the ammonia nitrogen removal of the system relied on the role ofconstructed wetland.Hydrolysis acidification and composite constructed wetland system are quite goodin permanganate-index、TP、NH₄⁺-N and TN removal, the best hydraulic loading of thesystem is0.25m³/（m²·d）, under this hydraulic loading, the average removal ofpermanganate-index is63.79%, TP is80.85%, NH₄⁺-N is71.78%, TN is50.72%. Compared the removal of different combination of wetland, revealed that thecomposite flow wetland are relatively good in the removal of nitrogen and, volcanicpacking is slightly better than gravel （<5%）, but not better as gravel onpermanganate-index removal, the differernt in fillers did not result in significantdiffererces in the removal of phosphorus. The subsurface constructed wetland withwindmill grass is well on permanganate-index removal, and wetlands with calamus areoverall bad on pollutant removal. For the cost of volcanic is relatively high, then theoptimal combination of the analysis obtained in this pilot wetland is the wetland ofmyriophyllum+canna+windmill grass+gravel+composite flow.