Experimental Research On The Treatment Of Roof Rainwater By The Microsand Coagulation

As the human economy make a spurt of progress, the contradiction of water supply and demand have become increasingly prominent, while the water environmental damage is gradually increased. Water resources pollution to the water shortages bring greater pressure. Speeding up the process of city urbanization bring, city hardened area increases, the runoff coefficient increasing, city original natural hydrological cycle is destroyed, the amount of rainfall resources loss. At the same time, it also brings a series of other problems, groundwater should not be added, decline of underground water level, the city flood control of the ability that fight calamity is abate, intensified the urban heat island effect. Then, rain and flood control using in easing the shortage of water resources and to some extent to improve the city water environment field show is very important and realistic significance.On residential and commercial areas of the roof, the road several underlying surface runoff water quality monitoring analysis, the conclusion:the quality of residential roof runoff water is best, the quality of business district roof runoff water, residential area road runoff quality is poor, the commercial area of road runoff quality is the worst. But the water quality along with the duration of rainfall variation are similar, namely in the rainfall runoff process, pollutant concentrations along with rainfall duration increases, tends to stability at last. Because rainfall has random sex and stability characteristics, the concentrations of all pollutants in rainfall runoff process there will be some fluctuations, but the overall trend. Rainfall in the nitrogen and phosphorus content is very low, basically reach the water quality requirement. After15min waste stream, residential roof rainwater CODCr reach about80mg/L, surface runoff in the waste stream after CODCr is about200mg/L, and rainwater runoff pollutants CODCr and SS have good correlation. Commercial area of the roof rainwater by20min split-flow, roof rainwater runoff CODCr drops to about170mg/L, and the CODCr and SS also have good correlation. However, the commercial area road runoff pollution is very serious, and rain water containing oil, heavy metals and other pollutants, not as the reuse water. Finalized residential roof rainwater is most suitable for the collection and use of water, after a certain physicochemical treatment can directly use. This paper proposes using micro sand coagulation process to treat the waste stream after the roof rainwater, through the experiment to analysis the optimum combination of parameters, the results is:Micro sand coagulation process to treat the waste stream after the roof rainwater effluent quality fully meet the water quality requirement, compared with conventional coagulation process for organic matter removal rate higher, and required a shorter. The optimum adding amount:Micro sand diameter is40μm, micro sand dosage is1.0g/L, the coagulant dosage of PAFC is25mg/L, the coagulant dosage of PAM is0.3mg/L. Removal effect of organic matter on the sequence of factors:micro particle size, coagulant, coagulant and coagulant interaction, fine sand, dosage of coagulant dosage.This paper tries to analyse the micro sands flocculation process feasibility and superiority from the point of flocculation kinetics. Micro vortex theory analysis:when the scale of micro vortex and the size is the most similar, flocculation reaction is the most complete. The flocculation reaction in a substantial increase in the proportion of turbulent micro vortex, can greatly increase the effective collision of the particle number, improve the flocculation effect. In the prophase of coagulant flocculation, adding micro sand and mixing can increase the proportion of the micro vortex in some extent.In view of the rain water treatment system uses the most widespread artificial wetland system, this article unifies the project example and micro sands flocculation process to make comparative analysis. The results were as follows:Micro sands flocculation process in occupation area saving, maintenance management is also more simple than the artificial wetland, water quality good, but to fully meet the requirements of the use, more suitable for the city’s future development needs.