| With the rapid development of social economy and the continuous enhancement of human activities,part of the untreated domestic sewage is being arbitrarily discharged,which seriously pollutes the ecological environment in rural areas and poses a serious threat to the water quality of surrounding natural water bodies such as lakes and rivers.The discharge of rural domestic sewage has the characteristics of relatively scattered generation sources and emission sources,high nitrogen and phosphorus content,and large variability in water volume over time.The use of a centralized processing device not only has a huge investment,but also has high operation and management costs,so ecological floating beds with simple,efficient,low energy consumption and low investment have been widely used as emerging in situ restoration technologies.In view of the current confusion of floating bed plants in the market,the purification effect of plants in different climate,water quality and other environmental conditions is uneven,in this study,14 common plants in Hunan were selected for the warm-season floating-bed plant screening test(cold-season floating-bed plants were selected 6 species form them that can survive in winter),and experiments on simulating domestic sewage produced by septic tank effluent under laboratory conditions,study the purification effect of different floating bed plant configuration modes on domestic sewage.After comprehensive analysis,a floating bed plant configuration mode with better purification effect in cold and warm seasons was screened out.Floating bed plants and stuffings are combined for testing,monitoring and analysis the dynamic changes of chemical oxygen demand(CODCr),ammonia nitrogen(NH3-N),total nitrogen(TN),and total phosphorus(TP)with time,which are aimed at screening composite ecological floating bed systems that can be applied.The main research results are as follows:1 Floating bed plant screening test(1)In the warm-season plant screening test,plant height,root length,and biomass growth rate of Acorus calamus and Ipomoea aquatica among 14 floating-bed plants have significant advantages(P<0.05).I.aquatica,Canna indicaand and Thalia dealbata have a high accumulation of TN and TP,and have high potential for purification of sewage.The ratios of TP absorption of C.indica and and Iris tectorum Maxim above ground and below ground are as high as 114.52 and 62.30.The ratios of TN absorption of Iris ensata and C.indicaand above ground and below ground are as high as 125.74 and 43.07.The removal rates of CODCr,TN,NH3-N and TP of the 14 floating-bed plants have significant advantages compared with the blank control group(P<0.05),and the net removal rates are between 6.30%-36.80%,11.92%-20.97%,22.92%-29.28%,and 5.51%-41.24%.The results of comprehensive cluster analysis of sewage purification showed that among the herbaceous plants,Pontederia cordata,A.calamus,C.indica,I.tectorum Maxim,I.aquatica and T.dealbata has strong comprehensive purification ability;among the woody plants,the comprehensive purification ability of Ilex latifolia Thunb is strong.(2)In the cold-season plant screening test,the plant height,root length,and biomass of the root system of Iris pseudacorus and Rosa chinensis are at the forefront,indicating that it has a strong ability to adapt to sewage;in all treatment groups,the I.ensata TN accumulation rate of above-ground and TP accumulation rate of Above-ground and below-ground have significant advantages(P<0.05).The TN accumulation rate of the underground part of the floating-bed plants in all experimental groups is higher than that of the above-ground part.The TP accumulation rate of the plants is mostly above-ground in the woody plants,while the herbs are the opposite.The removal rate of CODCr,TN,NH3-N and TP was 3.89%-14.25%,1.13%-10.54%,2.80%-19.04%and 6.13%-18.08%for all plant treatment groups.The plants with strong purification ability and good cold resistance are I.tectorum Maxim and Rosa chinensis.From the results of comprehensive cluster analysis of sewage purification,the plants with high purification ability have I.tectorum Maxim,I.latifolia Thunb and R.chinensis,and Ligustrum lucidum is medium purification ability plants,I.pseudacorus and I.ensata are low-purity plants.2 Study on the purification effect of floating bed plant and packing composite model on sewage.Through the screening test,4(2)single plant treatment groups,4(2)plant and stuffing composite treatment groups,1 single stuffing treatment group,1 blank control group,etc.a total of 10(6)test groups were set in the warm(cold)season floating bed plant and stuffing composite test.They monitored the water quality indicators of each test group during the 40-day test and measured the growth characteristics of the plant root system in each system at the end of the test.The main conclusions are as follows:(1)From the various indicators of the plant root sy stem in the warm season,it can be seen that the composite stuffing will promote the growth of the average root diameter to a certain extent,but in the case of quantitative quantification of pollutants,there will be a competitive relationship with the plant root system,so that the plant growth status and purification capacity are lower than that of a single plant floating bed in the composite floating bed.In terms of the net removal rate of CODCr,TN,and TP,the overall presentation of the stuffing composite group>single plant group>single stuffing group,shows that the composite stuffing can promote floating bed purification capacity for pollution to a certain extent,and the effect of plants is greater than that of stuffing.(2)The root index of the floating bed plants in the cold season shows that the general trend is similar to that in the warm season.The root growth status of the herbaceous plant group is stronger than that of the woody plant group,and it is inhibited by the composite stuffing on the floating bed to some exert during the experiment.In terms of water purification,the advantages of the composite stuffing in the early stage of the experiment were obvious.At the end of the test,the purification ability of each treatment group was expressed as stuffing composite group>single plant group>single stuffing group>blank control group,and the plant effect was still greater than the stuffing effect. |
PDF Full Text Request