| The eutrophic state of China's lakes and reservoirs has been very serious. There have been emergencies in the rapid increase trend, with outbreak of algae bloom size, frequency and intensity of algal toxins. Microcystis aeruginosa is the main species of cyanobacteria bloom in the eutrophic water, and with the eutrophication of water bodies in our country easily lead to the outbreak of water bloom. Flocculation is an effective way to remove algae and eutrophic material on water treatment in China. But traditional flocculant commonly used in water treatment, such as polyaluminum chloride (PAC) and polyacrylamide (PAM), etc. are prone to produce secondary pollution. Aluminum ions from hydrolysis of PAC enter human body through drinking water and it will lead to anemia, hair loss and dementia and other brain diseases. Organic pollutants are the same harm to human health by hydrolysis of PAM, such as acrylic acid and organic amine. Therefore, how to prepare a kind of novel environment-friendly water treatment flocculant, which is of less pollution and better flocculating performance, is a very important subject and an urgent task that need to be solved in water treatment field recently.In this paper, a kind of novel high-effect environment-friendly flocculant had been prepared by using the natural resources mineral. It used layered silicate clay minerals of sufficient source, microbe and various modifiers as the main raw materials, prepared modified clay flocculation. The flocculation effects were studied and the advantage of modified clay flocculation was analyzed. Algal bloom of Microcystis aeruginosa and the kinds of nutritious substances in water pollution were removed by the new modified layered silicate mineral / microbial flocculation materials. The adsorption behavior and mechanism of flocculation were also studied. Compares with the conventional flocculant, this new flocculant has more environmentally friendly function, lower price, higher effect and efficient application. The main research contents and results of this paper are included as following:1. By adopting the novel process, it took comparative test for the flocculating effect of Microcystis aeruginosa, on the preparation of natural clay material into modified clay flocculants. When modified clays dosage of 50 mg/L, the absorbance A680nm = 0.100 of the algal suspension, flocculating 4h after the removal of microcystis aeruginosa comparison, the removal capacity of clay mineral after a variety of modification can be more than 80% basically. Polysilicate iron modified clay flocculant had better effect than polysilicate aluminum, chitosan or polyacrylamide modified clay, flocculating of microcystis aeruginosa together. It had stronger coagulation ability, more compact flocs, faster particle settling velocity, and removal rate of more than 90%. Modified clay minerals had better flocculating affect, of which ferric polysilicate modified rectorite, sepiolite, palygorskite had better removal ability of microcystis aeruginosa. Modified rectorite by ferric polysilicate, had stronger coagulation ability, more compact flocs, faster particle settling velocity, and excellent removal ability of microcystis aeruginosa. It chose modified rectorite clay to do next research in the experiment, using ferric polysilicate as modifying agent, dosage ratio 1:10 of modifier and clay, ferric polysilicate modified rectorite dosage 50 mg/L or so, keeping flocculating for 240min, the removel rate of algae up to more than 95%, turbidity value from 55.0 NTU down to 3.1 NTU, removal rate of turbidity reached 94.4%. The flocculating efficiency increased dramatically.2. The preparation of modified rectorite was studied by analysing the affect factors, such as slurry concentration, ratio of clay and modifier, acid pH, ripening time of polysilicate, molar ratio of Si/Fe, aging time, dosage and so on. The experimental condition was confirmed by studying flocculation efficiency of microcystis aeruginosa, the concentration of rectorite pulp 10%, pH value 2, modifier weight ratio of rectorite 0.1, polysilicate ripening 45min, the molar ratio of Ferric-polysilicate about Si/Fe≈0.4, the aging reaction 90min. After full reaction, the mixed pulp was prepared into modified slurry through centrifugal dehydration to form standby mud. With the dosage of 10mg/L or so, it could achieve the algae removal rate of 89.0%, turbidity value removal of 90.4%.3. Removing algae using microorganism were studied by means of removal time experiment, microbial dosage experiment, and mcrocystins removal experiment. Compared to modified clay, the time required for microorganisms was longer, and the removal behavior had less effective, the flocculation to deal with algae didn't work. In the other side, microorganism had its own advantage of no organism left and complete catabolism. When the microorganism dosage was more than 5mg/L, the removal rate was up to 90% ten days later. Microorganism catabolism almost had no sediment, and modified rectorite compound had excellent flocculating efficiency, which were both required of water bloom removal. Flocculation composite material 2, adding microbial activation solution firstly, then adding the modified clay, algae removal rate of 89.3%, turbidity removal rate 90.8%. Modified clay and bacillus subtilis have a clear role in the removal microcystins MC-LR. 4. The new flocculant applied in the eutrophic water, with a variety of flocculant dosage to deal with the Han River, South Lake, and domestic wastewater. COD, TN, TP removal rates were significantly increased following the increasing dosage of composite flocculant. The removal rates are also better than the conventional flocculant PAC, treated water up to quality standards. Treated by three types of flocculants, Dosage of 20mg/L, the modified rectorite was better with the residual iron; when dosage was 35mg/L, the composite flocculant was better; dosage continue to increase, little change in the iron content. It can be seen, ferric polysilicate modified rectorite and composite materials in the dissolution of ions in aqueous solution are not obvious, and some continue to ion adsorption capacity of water bodies. It will not cause secondary pollution.5. The underside of sediment was calcined to remove the volatile organic matter adsorption for the secondary use of modified rectorite material. In dosage of 50mg/L, the removal rate was 89.2%, turbidity removal rate 74.2%; three times using modified rectorite material removal rate was 80.1%, turbidity removal rate 65.1%. Therefore, the modified rectorite has a good removal efficiency of the water bloom after microbial degradation, and it can be reused. The cost of new flocculant materials was lower than conventional flocculant, which have obvious advantages.6. The flocculatin of removal algae show mainly two aspects of synergistic effect, micro-organisms consumed nutritious substances and removed algal toxins, modified clay flocculated and adsorbted solid particle quickly. Modified clay flocculant in the flocculating process is mainly through the double-layer compression, electrochemistry adsorption, adsorption bridgework, netting capture sediment and so on. Bacillus subtilis consumed nutritious substances mainly through microbial competition, denitrification to get nitrogen off, polyphosphazenes to get phosphorus off, and the rapid decomposition of organic matter in water, enzyme secretion, and degradation of algal toxin. Therefore, the new flocculant not only enable the algal cells coagulation and other suspended particles agglomerate, but also consume and adsorb other nutritious substances in water to microbial remove N, P, COD, and Microcystin-LR, consequently solve the eutrophication problem of water bodies.
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