1, physical method
Physical methods mainly refer to dredging sediment, mechanical algae removal, water diversion and sedimentation, and water transfer. Dredging the contaminated bottom means removing pollutants from the system. It can greatly reduce the pollution contribution rate of sediments to the overlying water body, thus improving the water quality. The purpose of water diversion is to introduce clean water from upstream or nearby polluted rivers through the regulation of water conservancy facilities (such as gates and pumping stations) to improve the water quality of downstream polluted rivers. This method often treats the symptoms rather than the root cause.
2. Chemical methods
Chemical methods such as coagulation and sedimentation, adding chemicals to kill algae, adding iron salts to promote phosphorus precipitation, and adding lime to remove nitrogen. The research shows that this method has a good removal effect on turbidity, eoD, ss, TP, TN and heavy metals, and the daily dosage is small. However, this way of river sewage treatment is easy to cause secondary pollution.
3. Ecological-biological method Ecological-biological method (mainly including river aeration reoxygenation, biofilm method, bioremediation method, land treatment method, aquatic plant purification method, etc. )
(1) bioremediation technology
It refers to an engineering technology system that uses microorganisms and other organisms to degrade toxic and harmful pollutants in water or soil into CO2 and water in situ, or convert them into non-toxic and harmless substances. There are two main types of bioremediation technologies for river sewage treatment. One is to directly add one or more microbial strains that have been cultured and screened into the polluted river water. Experiments show that the removal rate of cOD is above 90%. The other is to add microbial growth promoters (nutrients) to polluted river water to promote the growth of "indigenous" microorganisms. After the pesticide is put into use, it can promote the growth of microorganisms that degrade pollutants by promoting growth. Microorganisms in the river will change from anaerobic to aerobic, and organisms will change from low to high, and the biodiversity of organisms will continue to increase, so that BOD5 and COD in the polluted water body will decrease rapidly, dissolved oxygen will increase obviously, and black odor will be eliminated. This method has obvious effect on eliminating black odor and increasing dissolved oxygen in water.
(2) Land treatment technology
Land treatment technology is an ancient and effective river sewage treatment technology. It takes land as the treatment facility, and uses the adsorption, filtration, purification and self-regulation functions of seven kinds of soil and plants to achieve the purpose of purifying water quality to a certain extent.
(3) Purification of aquatic plants
This method is a sewage purification method that makes full use of the natural purification function of aquatic plants. For example, duckweed and reed in wetland are used to purify a certain water area. The discharge of domestic sewage will cause odor, insect pests and landscape impact, so the above problems should be considered comprehensively when choosing, such as planting reeds in the downwind of spring and summer.
(4) River aeration method
Artificial aeration and reoxygenation refers to the artificial oxygenation of rivers under anoxic (or anaerobic) conditions, so as to enhance the self-purification ability of rivers, improve water quality and improve or restore the ecological environment of rivers. River aeration reoxygenation generally adopts two forms: fixed oxygenation station and mobile oxygenation platform. The process has the advantages of simple equipment, flexibility and reliability, less investment, quick effect, convenient operation, wide adaptability and no harm to aquatic ecology, and is suitable for the treatment of urban landscape rivers and micro-pollution source water.
(5) Biofilm technology
It means that microbial communities are attached to the surface of some carriers in the form of membranes. Through contact with sewage, microorganisms on the biofilm absorb and assimilate organic substances in sewage as nutrients, thus purifying sewage. At present, the commonly used biofilm technologies in river sewage treatment mainly include contact oxidation between gravels, contact oxidation in ditches (canals), purification by biological activated carbon packed tower, thin-layer flow method and undercurrent purification method, among which contact oxidation method is more commonly used.
Two, commonly used aquatic plants in river regulation are:
1. Lentinus edodes: perennial emergent ornamental plant, 5- 15 cm in height, alternate leaves, long stalks, shield shape, 2-4 cm in diameter, wavy edges, grass green and radial veins. It is often used for planting clumps and patches on the shore of water bodies, and is a good material for courtyard waterscape, especially for landscape detail design.
2. Submerged plants: Perennial emergent or submerged plants, with a plant length of 50-80 cm, upright stems at the upper part and submerged leaves at the lower part, are mostly five leaves, which are aquatic flowers with high ornamental value. Plant them into clusters, and after the plants are formed, there will be a pleasing green in the environment.
3. Purple taro: The height of the plant can reach1.2m. There are stems and bulbs underground, and the petioles and veins are purple-black, which is very eye-catching. The leaves are huge and are mainly used as foliage plants by the water.
4. Umbrella grass: also known as Phyllostachys pubescens, a perennial wet plant, with a plant height of 40- 150cm, stout stems, upright growth, nearly round stems and clumps, and flowering from July to September. It is often decorated in the crevices of rockery rocks on the banks of streams and has unique natural scenery.
5. Residual flowers: perennial emergent plants, with a plant height of 2 ~ 3m and a plant width of 2m. It blooms in July, grows vigorously, likes humidity and fears drought, and is suitable for water floating platform landscaping. The plants are beautiful and free, and the leaves are green and lovely. It is a top-grade flower for waterscape greening.
6. Canna mosaic: the plant height is 50 ~ 80 cm, the leaves are yellow-green, and the raceme is drawn from the top of the stem. The flowering period is from July to 10, and the annual green period is 240 days. Bonuses are burning and leaves are shining. Besides ornament, it can also purify air and water.
7. Canna: The plant height can reach 100 ~ 150 cm, with alternate leaves, broad oval shape and colorful colors, which is suitable for shallow water planting in wetlands. Has that function of purifying air and protect the environment. It is an ideal flower for greening, beautifying and purifying the environment.
8. Purple-leafed canna: plant height 100 ~ 150 cm, purple leaves, broad elliptic lanceolate, racemes leading from the top of the stem, flowering from July to 10, with a green period of 240 days throughout the year.
9. Arundo donax: The stem height is 1 ~ 3m, the stem diameter is nearly lignified, the leaf width is 1 ~ 3.5cm, with white stripes, and the stem on the ground is straight and has internodes, resembling bamboo. It is mainly used as the background material of waterscape gardens, and can also be decorated around bridges, pavilions and pavilions, and can be potted for garden viewing.
10, barracuda: perennial emergent or wet herb with large leaves, 20-80 cm high, changeable leaf shape, blue flowers, erect scape, usually higher than the leaf surface, and flowering from July to 10. Barracuda has green leaves, attractive colors and long flowering period, which can be used for family potted plants and pond culture, and can also be widely used for landscaping.
1 1. Iris sibirica: the plant height is 40 ~ 59 cm, and the flowering period is from May to June. The biggest feature of this variety is evergreen all the year round. It is a rare aquatic flower that can see both leaves and flowers, and it is an aquatic plant with high ornamental value.
12, Acorus calamus: a perennial erect herb, which likes warmth, cold resistance and fear of drought. It blooms from April to June and is the darling of aquatic flowers. It is yellow and beautiful, like butterflies flying among flowers, and has high ornamental value.
13. Acorus calamus: perennial aquatic flower with erect roots, 50-80 cm long, large purple flowers with yellow spots in the middle, and flowering from late April to late May. Flowers are big and beautiful, with rich colors and green leaves like swords, which are of high ornamental value.
14. Water lilies: perennial aquatic flowers with clustered leaves floating on the water surface, with a diameter of 6 ~ 1 1 cm, white flowers with a diameter of 3 ~ 6 cm, and flowering from mid-May to September. Large-scale planting and vigorous growth can present a magnificent landscape.