1. The utility model provides a clean system is administered to black and odorous river step which characterized in that: comprises an undercurrent wetland purification river reach, an surface current wetland purification river reach, a near natural beach purification river reach and a near natural pollution reduction river reach which are sequentially arranged from a sewage entry river mouth to a main river channel of a downstream river;

an in-situ purification island and an underflow wetland are arranged on the underflow wetland purification river reach, an internal electrolytic matrix is arranged in the in-situ purification island, and the underflow wetland is arranged below the in-situ purification island;

the surface flow wetland purification river reach is provided with a side groove connected with a main river channel, surface flow artificial wetlands are arranged in the side groove, and the surface flow artificial wetlands are communicated with one another;

a lateral seepage ditch with the head and the tail ends connected with a main river channel is arranged on the near natural beach land purification river section, gravels and civil fabrics are paved on two sides of the lateral seepage ditch respectively, vegetation is arranged on the water slope bank close to two sides of the lateral seepage ditch, and lateral seepage walls are arranged on two sides of the lateral seepage ditch respectively;

the near natural pollution reduction river reach is provided with a heart island, and native pollution-resistant plants are planted on the heart island and the main river channel.

2. The black and odorous river step treatment and purification system of claim 1, wherein: the internal electrolytic matrix comprises a matrix module and internal electrolytic fillers arranged on the matrix module, microorganisms are attached to the matrix module, the internal electrolytic fillers are mixed materials of scrap iron and copper scraps, the mass ratio of the scrap iron to the copper scraps is 5:1, and the subsurface wetland is arranged at a horizontal level elevation position below the in-situ purification island.

3. The black and odorous river step treatment and purification system of claim 1, wherein: flow guide channels are arranged between the side grooves and the main river channel and between the surface flow artificial wetlands, and first emergent aquatic plants are planted on the side slopes of the flow guide channels.

4. The black and odorous river step treatment and purification system of claim 1, wherein: the surface flow constructed wetland comprises a reservoir wetland and a marsh wetland, wherein at least 1.2m of water is submerged on a soil layer of the reservoir wetland, a second emergent aquatic plant is planted on the reservoir wetland and floating leaf plants are planted on the reservoir wetland, at least 0.2m of water is submerged on a soil layer of the marsh wetland, and a third emergent aquatic plant is planted on the marsh wetland and extends to the top of a slope bank of the marsh wetland.

5. The black and odorous river step treatment and purification system of claim 1, wherein: the rubble has been laid with being close to main river course one side at the bottom of the ditch of side infiltration ditch the side infiltration ditch is kept away from main river course one side and is laid civil fabric, the side infiltration wall setting that is close to main river course one side is to between the toe in the middle of the bank of side infiltration ditch, and the side infiltration wall setting that keeps away from main river course one side is on the beach of homonymy side infiltration ditch upper port department.

6. The black and odorous river step treatment and purification system of claim 5, wherein: the depth of the side seepage wall is 2-4m from the surface of the beach, zeolite or ceramsite is filled in the side seepage wall, a PVC pipe is also arranged in the side seepage wall, and a plurality of air holes are arranged on the PVC pipe.

7. The black and odorous river step treatment and purification system of claim 1, wherein: the indigenous stain-resistant plants comprise submerged plants, fourth emergent plants, rooted floating-leaf plants, fifth emergent plants and shrubs, the submerged plants are planted in the main riverway, the fourth emergent plants and the rooted floating-leaf plants are planted at the main riverway slope bank, and the fifth emergent plants and the shrubs are sequentially planted on the main riverway slope from bottom to top from 0.5m below the normal water level.

8. The black and odorous river step treatment and purification system of claim 7, wherein: the slope-to-fall ratio of the upstream slope, the back slope and the slope banks at two sides of the river center island is respectively 1: 7. 1: 3. 1: and 5, sequentially planting the fifth emergent aquatic plant and shrubs on the slope surface from bottom to top, and planting ornamental plants with short crowns and strong adaptability in a strip-shaped mixed manner on the top of the estuary island.

9. A gradient treatment and purification method for black and odorous rivers is characterized by comprising the following steps: the method comprises the following steps:

s1: dividing a main river channel from a sewage entry river mouth to a downstream river into an undercurrent wetland purification river section, an surface current wetland purification river section, a near natural beach purification river section and a near natural pollution reduction river section in sequence;

s2: constructing an in-situ purification island on the purification river reach of the subsurface flow wetland, wherein an internal electrolytic matrix is fused in the in-situ purification island, and constructing the subsurface flow wetland below the in-situ purification island;

s3: constructing a side groove connected with a main river channel on the surface flow wetland purification river reach, constructing surface flow artificial wetlands in the side groove, and communicating the surface flow artificial wetlands;

s4: constructing a side infiltration ditch of which the head and the tail end are connected with a main river channel on the near natural beach land purification river section, wherein broken stones and civil fabrics are paved on two sides of the side infiltration ditch respectively, vegetation is constructed on the bank close to the water slope on two sides of the side infiltration ditch, and side infiltration walls are also constructed on two sides of the side infiltration ditch respectively;

s5: and (3) remodeling a heart island on the near-natural pollution reduction river reach, and planting indigenous pollution-resistant plants on the heart island and the main river channel.

10. The black and odorous river step treatment and purification method of claim 9, wherein: in the step S2, the river dredging sludge is recycled, the coal cinder, the gravel and the sandstone are supplemented to form a purification island, and the internal electrolytic matrix is fused in the purification island to form a corrosive couple system for intensively decomposing the persistent organic pollutants remained in the water body.

Background

Along with the rapid development of economic society, the discharge amount of wastewater from production and living is remarkably increased, and after a large amount of wastewater is discharged into a river, the contents of COD (chemical oxygen demand), nitrogen and phosphorus pollutants and the like in the river are too high and far exceed the self-purification capacity of a water body, so that the water body is in a black and odorous state due to oxygen deficiency. Wherein, oxygen-consuming pollutants such as COD, ammonia nitrogen and the like are main black-causing odor-causing substances. The physicochemical environment of the black and odorous water body shows strong reduction property, the water body has peculiar smell and is not suitable for aquatic organisms to live, aquatic vegetation is degraded or even died, phytoplankton, zooplankton and benthonic animals only have a small amount of pollution-resistant seeds, a food chain is broken, food net support is broken, the structure of an ecological system is seriously unbalanced, and the function is seriously degraded or even lost. At present, river channels of some cities in China lack natural runoff, treated urban sewage and industrial wastewater are mainly used as incoming water, the urban sewage is directly discharged into the river channels, the river sections flowing through the cities are seriously polluted, seasonal or perennial black and odorous water occurs, and the health of water ecological systems and the quality of living environments of local residents are seriously influenced.

In the treatment process of the black and odorous rivers, on one hand, the drainage amount of the sewage in the drainage basin is reduced, and the pollution load entering the rivers is reduced; on the other hand, the key technology of industrial and urban life tail water ecological purification is applied in rivers, and the COD and ammonia nitrogen content of the industrial and urban life tail water in river reach is further reduced. The existing ecological purification technology of the black and odorous river water is mainly suitable for the black and odorous river with the ammonia nitrogen content lower than 15mg/L, the water quality of the black and odorous river is improved through bottom micro-aeration and submerged plants, and the self-purification capacity of the water body is improved through restoring the submerged plants. The surface ecological purification treatment method is not suitable for the treatment of rivers which lack natural runoff, mainly have treated urban sewage and industrial wastewater, and have COD and ammonia nitrogen concentration far higher than surface water V-type water quality, and the treated tail water has the problems of poor biodegradability and carbon source lack, and is difficult to solve only by aeration oxygenation, microorganisms and submerged plants are difficult to survive in the incoming water environment, and the water purification effect is poor.

Disclosure of Invention

The invention aims to provide a gradient treatment and purification system and method for black and odorous rivers, which are suitable for treating and purifying heavily polluted black and odorous rivers which lack natural runoff and mainly contain treated urban sewage and industrial wastewater as incoming water.

In order to solve the technical problem, the invention provides a black and odorous river step treatment and purification system, which comprises an undercurrent wetland purification river section, an surface current wetland purification river section, a near natural beach purification river section and a near natural pollution reduction river section which are sequentially arranged from a sewage entry river mouth to a main river channel of a downstream river;

an in-situ purification island and an underflow wetland are arranged on the underflow wetland purification river reach, an internal electrolytic matrix is arranged in the in-situ purification island, and the underflow wetland is arranged below the in-situ purification island;

the surface flow wetland purification river reach is provided with a side groove connected with a main river channel, an artificial wetland is arranged in the side groove, and the surface flow artificial wetlands are communicated with one another;

a lateral seepage ditch with the head and the tail ends connected with a main river channel is arranged on the near natural beach land purification river section, gravels and civil fabrics are paved on two sides of the lateral seepage ditch respectively, vegetation is arranged on the water slope bank close to two sides of the lateral seepage ditch, and lateral seepage walls are arranged on two sides of the lateral seepage ditch respectively;

the near natural pollution reduction river reach is provided with a heart island, and native pollution-resistant plants are planted on the heart island and the main river channel.

As a further improvement of the invention, the internal electrolytic matrix comprises a matrix module and internal electrolytic fillers arranged on the matrix module, microorganisms are attached to the matrix module, the internal electrolytic fillers are a mixture of scrap iron and copper scraps, the mass ratio of the scrap iron to the copper scraps is 5:1, and the subsurface wetland is arranged at a horizontal level elevation below the in-situ purification island.

As a further improvement of the invention, flow guide channels are arranged between the side grooves and the main river channel and between the surface flow constructed wetlands, and first emergent aquatic plants are planted on the side slopes of the flow guide channels.

As a further improvement of the invention, the surface flow constructed wetland comprises a reservoir pond wetland and a marsh wetland, wherein the soil layer of the reservoir pond wetland is at least submerged in 1.2m of water, the reservoir pond wetland is planted with second emergent aquatic plants and floating leaf plants are planted in intervals, the soil layer of the marsh wetland is at least submerged in 0.2m of water, and the marsh wetland is planted with third emergent aquatic plants and extends to the top of a slope of the marsh wetland.

As a further improvement of the invention, the gravels are laid on the bottom and the side close to the main river channel of the side infiltration channel, the civil fabric is laid on the side of the side infiltration channel far away from the main river channel, the side infiltration wall close to the main river channel is arranged between the middle of the slope of the side infiltration channel and the slope toe, and the side infiltration wall far away from the main river channel is arranged on the beach at the upper opening of the side infiltration channel at the same side.

As a further improvement of the invention, the depth of the side seepage wall is 2m-4m from the surface of the beach, zeolite or ceramsite is filled in the side seepage wall, a PVC pipe is also arranged in the side seepage wall, and a plurality of air holes are arranged on the PVC pipe.

As a further improvement of the invention, the indigenous pollution-resistant plants comprise submerged plants, fourth emergent plants, rooted floating-leaf plants, fifth emergent plants and shrubs, the submerged plants are planted in the main riverway, the fourth emergent plants and the rooted floating-leaf plants are planted at the main riverway slope, and the fifth emergent plants and the shrubs are planted on the main riverway slope from 0.5m below the normal water level in sequence from bottom to top.

As a further improvement of the invention, the slope-to-fall ratio of the upstream slope, the downstream slope and the slope banks at two sides of the estuary island is respectively 1: 7. 1: 3. 1: and 5, sequentially planting the fifth emergent aquatic plant and shrubs on the slope surface from bottom to top, and planting ornamental plants with short crowns and strong adaptability in a strip-shaped mixed manner on the top of the estuary island.

The invention provides a gradient treatment and purification method for black and odorous rivers, which comprises the following steps:

s1: dividing a main river channel from a sewage entry river mouth to a downstream river into an undercurrent wetland purification river section, an surface current wetland purification river section, a near natural beach purification river section and a near natural pollution reduction river section in sequence;

s2: constructing an in-situ purification island on the purification river reach of the subsurface flow wetland, wherein an internal electrolytic matrix is fused in the in-situ purification island, and constructing the subsurface flow wetland below the in-situ purification island;

s3: constructing a side groove connected with a main river channel on the surface flow wetland purification river reach, constructing surface flow artificial wetlands in the side groove, and communicating the surface flow artificial wetlands;

s4: constructing a side infiltration ditch of which the head and the tail end are connected with a main river channel on the near natural beach land purification river section, wherein broken stones and civil fabrics are paved on two sides of the side infiltration ditch respectively, vegetation is constructed on the bank close to the water slope on two sides of the side infiltration ditch, and side infiltration walls are also constructed on two sides of the side infiltration ditch respectively;

s5: and (3) remodeling a heart island on the near-natural pollution reduction river reach, and planting indigenous pollution-resistant plants on the heart island and the main river channel.

As a further improvement of the invention, in the step S2, river dredging sludge is recycled, coal cinder, gravel and sandstone are supplemented to form a purification island, and an internal electrolytic matrix is fused in the purification island to form a corrosive couple system to intensively decompose persistent organic pollutants remained in the water body.

The invention has the beneficial effects that: in different areas of a river reach where industrial and urban life tail water is discharged, internal electrolytic substrates are respectively adopted to reinforce undercurrent wetland purification, surface current artificial wetland water quality purification coupling, near-natural artificial beach soil lateral seepage combined purification and near-natural river pollution ecological reduction, so that the problem of poor biodegradability of the tail water is solved, the pollutants are reduced step by step, the river ecological environment is restored, the river self-cleaning capacity is improved, and the aim of comprehensively improving the river reach ecological environment is fulfilled; in the first section, the electrolytic matrix strengthens the undercurrent wetland purification river reach, and refractory substances in the river inflow water with low biodegradability and seriously unbalanced carbon-nitrogen ratio are decomposed into organic molecules which can be utilized by microorganisms, so that dissolved oxygen and carbon sources in the water are improved; the water quality of the second stage of the surface flow constructed wetland is purified and coupled with the river reach, a large amount of plants and microorganisms of the surface flow constructed wetland can absorb and degrade carbon sources and micromolecular organic matters generated by the first stage of technology, the degradation capability of the river channel on COD and ammonia nitrogen is improved, and a main channel-side channel structure is built at the second stage of the river reach, so that the flood discharge of the river channel is facilitated; the third section of near-natural artificial beach land-soil lateral infiltration combined purification river reach mainly utilizes a wide flood beach which is easy to appear at the rear end of a river channel, builds a lateral infiltration ditch lateral infiltration wall by combining topography, and improves the efficiency of denitrified nitrogen and phosphorus removal by utilizing soil, a water-bearing layer and the lateral infiltration wall and the incoming water which has recovered a carbon source; the fourth section is close to natural pollution to reduce river reach, a heart island is remolded, indigenous pollution-resistant plants are planted on the heart island and the main river channel, the natural river structure is restored, the self-cleaning capacity of the river is improved, and pollutants are further reduced; the first two river sections adopt a large amount of artificial intervention means, the biochemical property of the water coming from the river channel is firstly improved, the degradation capability of the river channel on COD and ammonia nitrogen is then improved, after the water quality is purified and the water environment is improved, the second two river sections adopt near-natural means to natural means, vegetation is restored, ecological diversity is restored, the original self-cleaning function of the river channel is restored, and the four river sections gradually reduce the artificial intervention means and restore the ecosystem of the benign cycle of the river.

Drawings

FIG. 1 is a schematic diagram of the system architecture of the present invention;

FIG. 2 is a schematic of the purification process of the present invention;

FIG. 3 is a schematic side sectional view of an in situ purification island of the present invention;

the reference numbers in the figures illustrate: 1. purifying the river reach by the subsurface flow wetland; 11. sludge; 12. a water permeable cloth; 13. a coal cinder layer; 14. a gravel layer; 15. planting soil; 16. an internal electrolysis strengthening purification reactor; 17. leveling the water level; 2. purifying river reach in surface flow wet land; 3. purifying river reach near natural beach; 4. the near natural pollution is reduced in river reach; 5. sewage enters a river mouth; 6. a downstream river.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Example one

Referring to fig. 1 and fig. 2, an embodiment of the present invention provides a black and odorous river step treatment and purification system, including an underflow wetland purification canal section 1, an overflow wetland purification canal section 2, a near-natural beach purification canal section 3 and a near-natural pollution reduction canal section 4, which are sequentially arranged on a main river channel from a sewage entry 5 to a downstream river 6;

an in-situ purification island and an underflow wetland are arranged on the underflow wetland purification river section 1, an internal electrolytic matrix is arranged in the in-situ purification island, and the underflow wetland is arranged below the in-situ purification island;

a side groove connected with the main river channel is arranged on the surface flow wetland purification river section 2, surface flow artificial wetlands are arranged in the side groove, and the surface flow artificial wetlands are communicated with one another;

a side seepage ditch with the head and the tail end connected with the main river channel is arranged on the near natural beach land purification river section 3, both sides of the side seepage ditch are respectively paved with gravels and civil fabrics, both sides of the side seepage ditch are provided with vegetation on the water slope bank, and both sides of the side seepage ditch are also respectively provided with side seepage walls;

the nearly natural pollution reduction river reach 4 is provided with a heart island, and native pollution-resistant plants are planted on the heart island and the main river channel.

Specifically, the construction of the subsurface flow wetland purification river reach 1: adopting an internal electrolysis matrix reinforced subsurface flow wetland purification technology in the subsurface flow wetland purification river section 1 to establish a subsurface flow constructed wetland model system: firstly, metal copper is used as a cathode, metal iron is used as an anode, the potential difference of the electrodes is increased, and an aeration process is added to generate Fe²⁺Is oxidized into Fe in the subsequent reaction³⁺The mass ratio of iron to copper is 1:0.2 and the gas-water ratio is 9:1, and the iron chips and the copper are mixedThe scraps are uniformly mixed and then added into the matrix module, and electrons flow through the matrix in the ion exchange process to promote the ion exchange of the matrix, so that the adsorption effect of the matrix is promoted. Wherein, microbes are cultured and attached on the surface of the substrate and exchange with electron transfer formed between the two electrodes, so that the activity of the microbes is improved, and the microbes can further utilize organic molecules obtained by electrochemical decomposition as a carbon source, thereby solving the problem of lack of carbon source of the incoming water, improving the biodegradability of the incoming water and realizing the efficient removal of pollutants; constructing a river channel in-situ purification island: an internal electrolysis strengthening purification reactor 16 is fused on an in-situ purification island to be used as a core part for promoting removal of pollutants, dredging sludge of a river channel is recycled, common matrixes such as coal cinder, gravel and the like are used as auxiliary materials to form the purification island, an underflow wetland is constructed above and below a horizontal level 17 under the island by 50cm to realize effective interception, filtration and purification effects on the pollutants in a water body, the in-situ purification island is constructed by referring to a graph 3, the underflow wetland is divided into a gravel layer 14, a coal cinder layer 13 and a permeable cloth 12 at the horizontal level 17 under the island, planting soil 15 is arranged above the underflow wetland, sludge 11 is arranged below the underflow wetland, the internal electrolysis strengthening purification reactor 16 is arranged on the island, and water flows pass through the in-situ purification island and the underflow wetland.

After the internal electrolytic matrix reinforced subsurface flow wetland purification technology is applied, the contribution rate to improving the transparency is more than 15 percent, the contribution rate to reducing COD is up to 40 percent, and NH is reduced₃The contribution rate of N reaches 50%, the contribution rate of TP is reduced by more than 40%, and the biodegradability of river sewage can be improved by 40%. Generally, the undercurrent wetland purification river reach 1 is applied to the first river reach from a sewage entry 5 to a downstream river 6, and refractory substances in the river incoming water with low biodegradability and serious carbon-nitrogen ratio imbalance are decomposed into organic molecules which can be utilized by microorganisms, so that the dissolved oxygen in the water is improved, and the subsequent river reach can better purify the sewage.

Constructing a surface flow wetland purification river reach 2: by adopting a surface flow artificial wetland water quality purification coupling technology, aiming at the dual requirements of river flood discharge and water quality purification, a main groove-side groove structure of a river is built, river side grooves are built on two sides (or one side) of a river bed, and the surface flow artificial wetland is built in the side grooves: pool wetlands and swamp wetlands. The main river water is guided through the diversion channelLeading to surface flow artificial wetlands, and alternately connecting the wetlands through diversion channels. The side slope ratio of the diversion trench is 1: 3, mainly planting bulrush and cattail which are emergent aquatic plants, and planting density is 3-5 plants/m². The pond wetland slope ratio is 1: 3, ensuring that 1.2m of water is submerged on the soil layer, and planting emergent aquatic plants of reed and cattail (3-5 plants/m)²) The floating-leaf plants of water lily, water chestnut and lotus are planted in the planting box. The side slope ratio of the marsh wetland is 1: 3, ensuring that 0.2m of water is submerged on the soil layer, and planting emergent aquatic plants of calamus and shallot (3-5 plants/m)²) And extends to the top of the bank. Through the functions of filtration, adsorption, coprecipitation, ion exchange, plant absorption, microbial decomposition and the like of the surface flow artificial wetland water quality purification coupling technology, the degradation capability of the riverway to COD and ammonia nitrogen is improved, and the pollution purification function of the riverway is strengthened.

And (3) constructing a near natural beach purification river reach 3: a near-natural artificial beach land-soil lateral seepage combined purification technology is adopted, and a lateral seepage ditch is built by utilizing a lateral ditch based on the wide characteristic of a flood beach and combined with the construction of a main ditch-lateral ditch structure of a river channel for a river with a beach land width larger than 150 m. The channel is arranged to guide water from the main river channel to the side infiltration ditch, the tail end of the side infiltration ditch is naturally intersected with the main river channel, and river water which is not subjected to side infiltration in the side infiltration ditch naturally flows back to the main river channel. The depth of the side infiltration ditch is 2m, and the side slope ratio is 1: 3. macadam with the grain diameter of 3-5cm and the thickness of 20 cm is paved at the bottom of the ditch and at the side of the ditch close to the main river channel, and geotextile is paved at the side of the ditch far away from the main river channel to prevent water from permeating into the outer side of the levee. Plants such as salix mongolica, medlar, grass-leaved sweetflag, dwarf lilyturf tuber, iris or allium fistulosum are planted on the water surfaces of the two sides of the ditch to prevent water and soil loss of the slope bank and increase the stability of the slope bank. And (3) digging a side seepage wall downwards at one side of the side seepage ditch close to the main river channel, vertically digging downwards from the middle of a ditch slope bank to a slope toe, wherein the depth of the side seepage wall is 2-4m from the surface, and zeolite or ceramsite with the particle size of 2-3cm is filled in the wall. And (3) vertically digging a side seepage wall downwards on the beach near one side of the side seepage ditch and 8-12m away from the upper opening edge of the side seepage ditch, wherein the wall and the side seepage ditch are in the same direction, the depth of the side seepage wall is 2-4m away from the surface of the beach, and zeolite with the particle size of 2-3cm is filled in the wall. And arranging ventilation PVC pipes with the diameter of 10cm in the side seepage walls, and forming holes at different depths of the PVC pipes to reoxygenate aquifers of the side seepage walls. By utilizing the vegetation, soil, aquifer and side seepage wall of the beach land in the river levee, pollutants are removed intensively, the denitration nitrogen and phosphorus removal efficiency is improved, and the river water quality is purified.

Construction of a near-natural pollution reduction river reach 4: by adopting the ecological pollution reduction technology of the near-natural river channel, indigenous pollution-resistant and pollution-purifying plants are planted in the main river channel side slope, the river heart island and other areas, the natural river structure is restored, the self-purification capacity of the river is improved, and pollutants are further reduced. Firstly, river habitat survey is carried out, and vegetation screening and configuration are carried out according to the characteristics of indigenous organisms in a drainage basin. Submerged plants with strong pollution resistance, such as hornworts, eel grass, hydrilla verticillata and the like can be dispersedly planted in the riverway. Emergent aquatic plants and rooted floating-leaf plants with strong stain resistance and water logging resistance, such as scripus triqueter, calamus, allium fistulosum, iris tectorum, scirpus yagara, thalictrum ramosissimum, ranunculus lanceolatus and the like, are respectively planted on the river slope bank. The main riverway side slope is provided with vegetation from 0.5m below the normal water level, emergent aquatic plants and shrubs are planted from bottom to top in sequence, and the height of the vegetation is from short to high. For example, iris, calamus and shallot are arranged at the lower part of the ramp, medlar is arranged at the middle part, and amorpha fruticosa is arranged at the lower part. The river core island formed by utilizing a wider favorable terrain and the existing impact in the river channel is remodeled on the premise of not influencing flood discharge, and the slope-to-fall ratio of an upstream slope, a downstream slope and two side slope banks of the river core island is respectively 1: 7. 1: 3. 1: and 5, planting emergent aquatic plants and shrubs on the slope surface in sequence from bottom to top. For example, in the following 1: the water-facing slope surface of 7 and 1: 5, planting emergent aquatic plants and shrubs on the slope banks at the two sides from bottom to top in sequence, wherein the lower parts are the emergent aquatic plants including allium mongolicum regel, calamus and iris tectorum, the middle part is medlar, and the upper part is amorpha fruticosa. In the following steps of 1: 3, emerging plants and shrubs are sequentially planted on the backwater slope surface from bottom to top, the lower parts of the emerging plants are planted with reed, cattail and radix ophiopogonis, and the upper parts of the emerging plants are planted with amorpha fruticosa. In order to restore and increase the vegetation coverage at the top of the island and simultaneously increase the landscape effect on the island, plants with low crown, more branches and strong adaptability and higher ornamental and economic values, such as crape myrtle, metasequoia, willow or mulberry, are selected and planted in a strip-shaped mixed mode. After the sewage is subjected to the former triple purification, the tail end of the river reach utilizes various elements imitating natural forms, such as a estuary island, a beach land, a side trough and the like, to rebuild a flow path close to the nature and water flows with different flow velocity zones, and the purification capability of the nature is improved. And through vegetation restoration, the surrounding environment of the river channel is improved, the biodiversity of the riparian wetland ecosystem is increased, the function of the natural wetland ecosystem is restored, and the heterogeneity and the stability of the habitat are improved.

Referring to fig. 2, the invention flows out black and odorous water from a sewage inlet 5, passes through a corresponding graph A of an undercurrent wetland purification river section 1, namely, the biochemical property of the black and odorous water is improved by utilizing an internal electrolysis matrix reinforced undercurrent wetland purification technology and then enters an upstream wetland purification river section 2, the upstream wetland purification river section 2 corresponds to a corresponding graph B, namely, the degradation capability of COD and ammonia nitrogen is improved by utilizing a water quality purification coupling technology of an upstream artificial wetland, so that the black and odorous water is gradually changed into first-class A water and then enters a near natural beach purification river section 3, the near natural beach purification river section 3 corresponds to a graph C, namely, the water is denitrified by utilizing a near natural beach-soil side infiltration combined purification technology to remove ammonia and phosphorus, the improvement is that surface quasi-class V water enters a near natural pollution reduction river section 4, the near natural pollution reduction river section 4 corresponds to a graph D, namely, the river self-purification capability is improved by utilizing a near natural river pollution ecological reduction technology, the water is improved to surface quasi IV water, the pollutants are reduced step by step, the river ecological environment is restored, the river self-purification capacity is improved, the goal of comprehensively improving the river basin ecological environment is reached, after 4-stage reduction and purification, the sewage transparency is improved by 80-90 percent on average, the COD is reduced by about 50 percent, and NH is reduced₃N is reduced by 70-80%, TP is reduced by 30-40%.

Example two

The embodiment of the invention provides a gradient treatment and purification method for black and odorous rivers, which comprises the following steps:

s1: dividing a main river channel from a sewage inlet 5 to a downstream river 6 into an undercurrent wetland purification river section 1, an surface current wetland purification river section 2, a near natural beach purification river section 3 and a near natural pollution reduction river section 4 in sequence;

s2: constructing an in-situ purification island on the purification river reach 1 of the subsurface flow wetland, fusing an internal electrolytic matrix in the in-situ purification island, and constructing the subsurface flow wetland under the in-situ purification island;

s3: constructing a side groove connected with the main river channel on the surface flow wetland purification river reach 2, constructing surface flow artificial wetlands in the side groove, and communicating the surface flow artificial wetlands;

s4: constructing a side seepage ditch with the head and the tail ends connected with a main river channel on a near natural beach land purification river section 3, paving broken stones and civil fabrics on two sides of the side seepage ditch respectively, constructing vegetation on a bank close to a water slope on two sides of the side seepage ditch, and constructing side seepage walls on two sides of the side seepage ditch respectively;

s5: and (3) remodeling the heart island on the near-natural pollution reduction river reach 4, and planting indigenous pollution-resistant plants on the heart island and the main river channel.

As a further improvement of this embodiment, in step S2, the river dredging sludge is recycled, the coal cinder, gravel and sand are supplemented to form a purification island, and the internal electrolysis matrix is fused to the purification island to form a corrosive couple system, so as to enhance the decomposition of the persistent organic pollutants remaining in the water.

The method can be applied to the Jianlu river, the Jianlu river is basically not supplemented and flowed in by natural runoff, the main runoff sources are domestic sewage and industrial wastewater, and the runoff source is a sewage discharge channel of Zhengzhou city.

The total discharge of 43 industrial enterprises in the Jianlu river tributary, namely the Soxhlet river catchment area in 2006 is about 1.62 million t/d, wherein the discharge amount of industrial sewage is 0.85 million t/d, and accounts for 52.5 percent of the total discharge amount; the discharge amount of the domestic sewage is 0.77 ten thousand t/d, which accounts for 47.5 percent of the total discharge amount. COD is monitored to be 88mg/L in a garden road, a beard and a river bridge at 10 months and 8 days in 2007; NH (NH)₃N is 20.8 mg/L. Aiming at the serious pollution condition of the river channel of the Jianlu river basin, a 10-kilometer river reach is selected as a technical demonstration area in the Soxhlet river.

The method is characterized in that the method comprises the following steps of (1) demonstrating an engineer river dam (N34 degrees, 52 '13.5 degrees, E113 degrees, 34' 02.1 ') to a cable-whisker river entering Jialu river estuary (N34 degrees, 52' 09.1 degrees, E113 degrees, 43 '30.3') with the total length of 18.48 km and the width of a river channel of 120 m-170 m; the daily treatment water amount is 50,000-400,000 t; wherein, an internal electrolysis matrix reinforced undercurrent wetland purification technology demonstration section is constructed for 7.68 km, an surface current artificial wetland water quality purification coupling technology demonstration section is constructed for 4.07 km, a near natural artificial beach land-soil lateral infiltration combined purification technology demonstration section is constructed for 3.76 km, and a near natural river pollution ecological reduction technology demonstration section is constructed for 2.97 km.

Before the beginning of the demonstration project (5 months in 2009), after the civil engineering project is finished (9 months in 2009), and after the vegetation recovery project is finishedAfter 9 months in 2010 and after vegetation is completely recovered (9 months in 2011), 5 sampling points are respectively arranged at the effluent and the downstream of the demonstration project for monitoring the water quality change; the mean results show that: three different stages, respectively, increased transparency by 46.11%, 81.27%, 84.68% compared to before the exemplary engineering; COD_MnReduced by 22.92%, 35.77%, 49.42%, NH₃N was reduced by 35.82%, 58.57%, 76.61%, and TP by 7.33%, 16.97%, 35.83%.

In 2011 after the demonstration project is completely finished, water quality monitoring is carried out from the water inlet section to the water outlet section of the demonstration project along the water flow and the subsection nodes of the demonstration project; the results show that: the contribution rates of the demonstration section of the internal electrolyte matrix reinforced subsurface wetland purification technology to the reduction are respectively 16.40 percent of transparency and COD_Mn 35.51%、NH₃49.06 percent of-N and 43.74 percent of TP, and the demonstration sections of the artificial wetland water quality purification coupling technology are respectively 10.43 percent of transparency and COD_Mn 21.06%、NH₃24.33 percent of N, 34.59 percent of TP, 19.43 percent of transparency and 19.43 percent of COD respectively in the demonstration section of the near natural artificial beach land-soil lateral infiltration combined purification technology_Mn 14.45%、NH₃12.07 percent of N, 17.18 percent of TP, and the transparency of 53.74 percent and the COD of the demonstration section of the near-natural river pollution ecological reduction technology_Mn28.99%、NH₃-N 14.54%、TP 4.49%。

Before demonstration engineering, the river reach is basically a sewage channel, plants are rare, fishes are extinct, and birds do not inhabit. When the demonstration engineering is implemented, 12 aquatic and hydrophytes are planted in sequence; but with the effective improvement of water quality and habitat, more than 70 plants are naturally recovered; meanwhile, benthonic animals, aquatic insects and fishes recover naturally, particularly wild ducks, snipes, small grebes, black water chickens, rice seedling chickens and small aigrette inhabit in groups and forage for river sections, and the quality of river water is obviously improved; the appearance of large-scale spontaneous fishermen (fishermen) at the downstream section of the demonstration river indicates that citizens recognize the effect of water quality improvement.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.