Analysis of sewage purification by waste wateraquatic higher plants,

60 years since the 20th century, the domestic and foreign scholars have used to study sewage treatment plants. West Germany in 1974, built the first one for the Water meters treatment wetland, in the 20th century, China has implemented 80 water hyacinth purification ponds to the main sewage treatment and utilization of ecological engineering, pollution control and increase production to achieve a double benefit. In recent years, coastal mangrove wetland wastewater treatment have bargained for. Can be seen, whether constructed wetlands, clean pond or land treatment systems, sewage purification by aquatic higher plants have broad application prospects. In order to achieve better results and higher purification purification efficiency, it is necessary to purify water aquatic higher plants the mechanism of experimental study.

An aquatic macrophytes in wastewater purification mechanism

1.1 cattail plant purification of lead / zinc mine waste case study

Typha latifolia monocotyledonous perennial emergent plants, with rhizomes, stems and keep growing next to the other rapidly developing into a group, to form a clean pond and aquatic plant populations of absolute advantage. And Environmental Sciences, Zhongshan University, Shaoguan, where I lead / zinc mine tailings environmental monitoring stations for the port where large and heavy metals in waste water pollution in major design and use of local waste rock and gravel built a cattail purification ponds. According to the results of the untreated lead / zinc mine waste water containing Pb, Zn, Cd, exceeding the total suspended solids content, but after post-purification ponds, SS removal rate of 99%, Pb, Zn, Cd removal rate 84% ~ 90%, the index has reached industrial emissions standards. Dark gray water has been turned into clean water cattail community, cattail plants can thrive, pool and there was even a variety of algae, fish and malaccensis plants.

1.2 mangrove plant oil wastewater and urban sewage purification Case Study

Mangroves are unique to tropical coastal wetland ecosystems, including terrestrial ecosystems and aquatic ecosystems, with the anti-storm, to protect its ecological function, and its rich biological resources, beautiful scenery, with high economic value and aesthetic value . For sewage treatment, mangroves have a unique role.

Li Mei and other artificial wetlands with K. candel were a one-year trial of oil waste water purification, wastewater treatment was found with the oil concentration, the relative purification plants to oil ratio is: 50mg / L group, 75.76%, 100mg / L group 67.55%, while the 800mg / L group, 42.94%, showing that the purification efficiency increases with the concentration. Oil content of the size of root> leaf> stem> branch. Experiments also showed that: candel appropriate concentration of oily waste water purification should be not more than 200mg / L.

Avicennia marina mangrove is a perennial plant. Similarly, the normal, 5 times, 10 times the concentration of synthetic sewage to the artificial Avicennia marina wetland, the year proved: artificial Avicennia marina wetland of heavy metals in sewage purification rate of 88% or more, which purify rate of Pb 97.91%, Zn purification rate was 89.47%; N purification rate of 88.04%. For N, Pb, Zn was absorbed as a plant Avicennia marina structure elements, absorption of large, Guer purification of synthetic wastewater with the same corniculatum (purification rate of N: 60.58%, Pb: 93.62%), K. candel (purification rate of N: 60.58%, Pb: 93.44%) compared to the maximum purification rate. Visible, marina sewage containing heavy metals have a strong adaptability and tolerance.

1.3 Case Study of Pulp and Paper Effluent purifying herbs

Hao Dengfeng 7 selected aquatic plants such as: Water hyacinth, water, peanuts, large drift, duckweed, windmill grass, broad leaf Hong thin and bamboo, to establish the system of paper industry wastewater treatment plant will be made of three concentrations of mixed waste water injection level Plant your system. Through the experiment, seven kinds of plants on the removal of suspended solids in wastewater were 70%, of which water hyacinth, water, peanuts, windmill grass for more than 84%; on TN, TP removal ability of size: water hyacinth> big drift > Water peanut> duckweed, windmill Draft "Typha latifolia> wild rice stem.

But not CODCr and BOD5 removal efficiency to 50%. Wastewater by only water peanuts, water hyacinth removal markedly, the water removal rate of up to 9 days after peanut 73.33%, up 54.67% of water hyacinth, making black smelly water was relatively clear.

1.4 Mechanism of purification

1.4.1 Resistance of plant traits and their ability to

Aquatic plant living in an oxygen due to the long, low light environment, their morphological and anatomical structure of the formation of special characters. Roots, stems and leaves form a full ventilation organizations to ensure that organs and tissues to O2¡¯s needs; leaves were succulent, with thick cuticle, such as cattail epidermis, palisade tissue, pollution point of the root, stem, leaf epidermal cells closely arranged, etc. structure can suffer from pollution caused by resistance to the assimilation of functional decline, excessive transpiration of water, enhanced stain resistance and cattail plant resistance.

1.4.2 Plant uptake, accumulation

Aquatic plants developed root system, which will help absorb the water substance. Such as water hyacinth long process requires a lot of N, P nutrients, it grew rapidly absorbed, for the purification of eutrophic water effect is obvious; cattail plants absorb heavy metals from wastewater, the absorptive capacity in the order of root> rhizome> leaf , and in accordance with a certain proportion of habitat to draw from various elements to form a new dynamic equilibrium, to prevent excessive absorption of certain elements caused by poisoning. After the plants to absorb pollutants, especially heavy metals, pesticides and other synthetic organic compounds, etc., will be enriched, fixed in the body or the soil, reduce the amount of water pollutants. The results show that, Pb, Zn into the cattail body, mainly cortical cells accumulate in the cell wall, only a small amount into the cytoplasm, cell wall shows a higher affinity for heavy metals.

1.4.3 purification ponds settlement, the role of adsorption and filtration

Purifying pond water plants grew well developed root system, large contact area with water to form a dense filter layer. Such as Typha, its underground stems and roots in a crisscross pattern network of underground stems, water flow is slow, heavy metals and suspended particles are separated and settlement, to prevent water loss with. While the surface by ion exchange, chelation, adsorption, precipitation, insoluble gel for root adhesion and adsorption, aggregation of the bacteria suspension of micelles to the organic and metabolic products of the settlement down.

1.4.4 Biochemical role

The process of sewage purification plants, chemical reactions also play a significant role in this regard has been a lot of research. Photosynthesis of O2 and O2 in the atmosphere directly to the plants around to water diffusion, while root through the release of O2, oxidation and decomposition fallout around the root system; the other to the bottom of water bodies and the formation of many anaerobic soil matrix and aerobic cell, to create the conditions for the microbial activity and thus form a "rhizosphere zone." In this way, plant metabolites, and residues and dissolved organic carbon to the wetland in the colonies to provide food sources; the same time a large number of microorganisms in the biofilm matrix formed on the surface of gray, increasing the quantity and microbial catabolism of area, so that contamination of plant roots material (enrichment or settlement down) is microbial decomposition of use or removal of microbial metabolism in the degradation process. Eutrophic water, aquatic plant roots can rely on microorganisms to denitrifying bacteria, ammonification bacteria etc to speed up the NH3-N NO2-N and NO3-N in the transformation process, to facilitate the absorption and utilization of aquatic plants, reducing the bottom soil nutrients to the water release.

1.4.5 Competitive inhibition of the planktonic algae

Serious water eutrophication, algae blooms, water quality deterioration. Planting aquatic plants, compete with planktonic algae and nutrients needed for light and heat conditions, while secreted algal material, destruction of normal physiological metabolism of algae, algae dead force to prevent it brings toxins. This will improve the water transparency, improve water DO content, promotion of submerged plants and symbiotic bacteria growth, and further purify water.