Research On "Bioflocculation-Multistage Constructed Wetland Infiltration Bed" For Wastewater In Small Town

Aiming at developing a kind of wastewater treatment technique that high efficiency, low invest, low operation cost and operation simply, object to the problem of low efficiency and jammed easily in traditional constructed wetland, The treatment technique of"bioflocculation—multistage constructed wetland infiltration bed"was put up. Hydrolyzing acidification, bioflocculation and settling were incorporated in the pretreatment system. Multistage was adopted in constructed wetland, the area of nitrification and denitrification were set in this system, and substance of cinder and limestone were added to intensify phosphorus removal, which can enhanced the efficiency of nitrogen and phosphorus removal. At the same time, scientific graduation of substance was adopted, to improve hydraulic character protect blocked up. By experiment, plant of high efficiency nitrogen removal and substance of high efficiency phosphorus removal were screened out. The key parameters of bioflocculation, biological/chemical flocculation and multistage constructed wetland infiltration bed were put out, this system have good performance of adaptability to higher concentration town wastewater and low temperature in winter, and widden the applying area. The main conclusions can be made in this experiment:①In the experiment of filtering plant that high efficiency of nitrogen removal, the result showed that, When the NH4+-N and TN load separately is 3.0gNH4+-N/m2.d and 3.61gTN-N/m2.d, in the constructed wetland that plant Coix lachrymajobi L, canna, rush and Arundo donaxl, the NH4+-N removal rate separately is 55.7%, 54.4%, 44.7% and 42.0%`; the TN removal rate separately is50%,48.4%,41.7% and 40.0%; the efficiency of nitrogen removal is:Coix lachrymajobi L>canna>rush>Arundo donaxl.②In the experiment of filtering substance of phosphorus removal, the result show, influent concentration of PO43--P 2.9mg/L, HTR=4h, effluent concentration of PO43--P in gravel,broken brick and cinder each is 2.0mg/L,1.0mg/L and 0.4mg/L. removal rate each is 31.0%,75.9% and 86.2%. Efficiency of phosphorus removal is cinder>broken brick>gravel. In the constructed wetland of admixture of cinder and gravel, efficiency of phosphorus removal increased with cubage proportion of cinder :gravel. HRT=2, the cubage proportion of cinder :gravel each is 0,0.3,0.5 and 0.7, influent concentration of PO43--P =3.1mg/L, effluent concentration of PO43--P seperately is 2.6mg/L,1.9mg/L,1.6mg/L and 1.55mg/L, removal rate each is 16.1%,38.7%,48.4%and 50%, removal rate rised with the cubage proportion of cinder :gravel increased, and effluent pH increased also,effluent pH increased from 7.3 to 10.3. The optimal cubage proportion of cinder :gravel is 0.3 by experiment.③The research of pretreatment show that, temperature 20~35℃, influent concentration of COD,NH4+-N and PO43--P each is 741mg/L,89.48mg/L and 5.7mg/L, effluent concentration from bioflocculation system demonstration engineeringⅠis 260mg/L,76mg/L and 4.5mg/L, removal rate separately is 65%,14.98% and 21%. influent concentration of COD,NH4+-N and PO43--P each is 490mg/L,90.20mg/L and 5.7mg/L, effluent concentration from bioflocculation system demonstration engineeringⅡis 250mg/L,80.94mg/L and 4.73mg/L, removal rate separately is 49%,10.27% and 17.8%.④Temperature 20℃~ 35℃, When the organic and nitrogen load are 41gCOD/m2.d and 11.69gTN/m2.d, influent high concentration of COD,NH4+-N,TN and PO43--P each is 352mg/L, 70.12 mg/L, 82.54 mg/L and 4.5 mg/L, effluent concentration of PO43--P seperately is 47mg/L, 32.62 mg/L, 39.76 mg/L and 2.0 mg/L, the removal load separately is 42.43gCOD/m2.d,5.95gTN/m2.d and 0.35gPO43--P/m2.d.⑤After cinder and limestone were added to multistage construced wetland infiltration bed, temperature 25~30℃, 1.72gTN/m2.d removal load be increased in constructed, removal rate increased 13.6%; 0.11gTN/m2.d removal load be increased in constructed, removal rate increased 15.4%.⑥The analysis to treatment efficiency show that, the treatment efficiency of"bioflocculation—multistage constructed wetland infiltration bed"is higher, compared to traditional constructed wetland, its removal load of COD, TN and PO43--P each increased more than2.72gCOD/m2.d,1.59 gTN/m2.d and 0.08gPO43--P/m2.d...