Application of coagulation magnetic separation technology in eutrophic water treatment

What is eutrophic water body

Due to the discharge of excessive nutrients (nitrogen and phosphorus) in natural water, various aquatic organisms, plants, especially algae, proliferate and grow abnormally, and a phenomenon that deteriorates water quality is called water eutrophication (called "bloom" for fresh water and "red tide" for ocean). The eutrophication of water body is serious in China, and how to effectively control eutrophication lakes has become the primary problem of water environment protection in China.

Comparison of treatment schemes for eutrophic water bodies

At present, there are mainly the following methods to control eutrophication and algae removal technologies at home and abroad:

1. Physical methods: including sediment dredging, water diversion dilution or water change, filtration and adsorption, ultrasonic algae removal, sediment covering method, shading method, etc.;

2. Physical and chemical methods: coagulation and sedimentation, adding drugs and air flotation, etc.;

3. Chemical methods: chemical agent method, electrochemical method, photocatalytic oxidation method, ozone oxidation method, etc.;

4. Biological method: including planting aquatic higher plants, breeding filter-feeding fish such as silver carp and bighead carp, artificial biological floating islands, etc.;

5. Other measures: mechanical algae removal, etc.

Although the above measures have achieved certain results, there are different technical defects. The key to control lake eutrophication is to remove algae, and the most fundamental thing is to remove nutrients such as nitrogen and phosphorus and algae from water body in time to control the growth level of algae. In view of the characteristic pollutants in water, we adopt "coagulation and magnetic separation technology", which provides a new and effective way to reduce eutrophication of lake water and inhibit cyanobacteria outbreak.

Unique advantages of coagulation magnetic separation technology in eutrophic water treatment

Coagulation magnetic separation technology is an innovation based on magnetic separation technology. The magnetic species loaded in it are magnetic substances after surface modification, which combine with some pollutants in water through covalent bonds and ionic bonds, so as to achieve the purpose of cleanup separation and sewage treatment. It has excellent removal effect on phosphorus, one of the "culprits" of water eutrophication, and has a good removal effect on suspended solids, colloidal substances, heavy metal ions, algae cells and other pollution factors in water.

The magnetic floc formed by this process does not need precipitation, but realizes cleaning and highspeed separation through a strong magnetic separation equipment manufactured by using rare earth permanent magnet technology, which not only realizes efficient treatment, but also greatly saves the occupied space of equipment, and makes the integration of treatment devices possible.

The principle of coagulation magnetic separation is as follows: firstly, adding self-developed magnetic flocculant to eutrophic water body for coagulation treatment; Through the formation of magnetic floc, the flocs containing pollutants are quickly salvaged from the water body by using magnetic field, thus solving the problem of nitrogen and phosphorus pollution in the water body; The flocculant can be recycled after the flocculant is treated by the magnetic powder recovery system.

Application of coagulation magnetic separation technology in eutrophic water treatment

For largescale natural water bodies such as lakes and rivers, putting coagulation magnetic separation equipment on floating boats can realize watershed management more effectively.

Coagulant delivery, mixing, flocculation, magnetic separation, magnetic flocculant recovery, sludge disposal, water quality detection and other processes are all integrated on a floating boat with a length of 25 meters, a width of 10 meters and a draft of 1 meter. The floating boat travels 4 ~ 5 kilometers every day (working about 8 hours), and treats about 10,000 cubic meters of eutrophic water every day.

Working principle and parameters of floating ship

The basic working principle of the floating ship is: the front and back of the floating ship are opened, and the hull travels on the lake at a certain speed. After the lake water flows into the reservoir, the water and magnetic flocculant are pumped into the impinging stream reactor for rapid mixing reaction; After coagulation, the sewage enters the flocculation area of hydraulic partition, and after adding flocculant, it forms magnetic floc; When flowing through the magnetic separation area, the magnetic floc is adsorbed by the magnetic disk and taken away from the water surface. When the magnetic disk is transferred to the magnetic isolation slag discharge belt, it is scraped away from the magnetic disk for recovery treatment, and the clean water flows through the magnetic disk to complete the purification process.

Working parameters: disk diameter: 1600mm;; Number of disks: 40; Disk gap: 65mm;; Power of disk pack reducer: 11kW;; Disk speed: 1 ~ 1.2 r/min; Voltage: 380V/50Hz;

Treatment process flow

Operation process of water treatment of eutrophic water body

1. Selective sewage interception and proper control of organic matter content in water are necessary conditions for treatment;   

2. Carry out giant magnetic separation and circulation purification on water body, reduce suspended solids, algae, phosphate and other pollutants in water body, eliminate key factors affecting water landscape effect and water quality, reduce the degree of rich oxidation of water body, and make water body become clear and transparent quickly;

3. Carry out artificial oxygenation on water bodies to restore the self-purification ability of the ecosystem composed of "indigenous" microorganisms to water bodies; Planting a certain number of aquatic plants artificially and stocking a suitable number of fish schools. Artificial aquatic plants can synthesize organic matter from inorganic matter, which is beneficial to realize the material balance of ecosystem. Fish schools can control the growth of algae. When fish grow to a certain number, artificial fishing not only controls its number, but also removes some nitrogen and phosphorus from water.

Embodiments