Principle and advantages of loaded flocculation magnetic separation (BFMS)
BFMS technology is to add magnetic powder to the traditional flocculation process to enhance the flocculation effect, form high-density flocs and increase the proportion of flocs, so as to achieve the purpose of efficient decontamination and rapid sedimentation. The ionic polarity and metal characteristics of magnetic powder, as the core of floc, greatly enhance the flocculation binding ability of suspended pollutants in water, reduce the dosage of flocculant, and have better effect in removing suspended substances, especially phosphorus, bacteria, viruses, oil and heavy metals than traditional processes. Because the specific gravity of magnetic powder is as high as 5.0× 10? kg/m？ , about twice as much as sand. The specific gravity of floc mixed with magnetic powder increased, and the floc quickly settled, with the speed exceeding 20 meters per hour. The whole water treatment can be completed in about 10 minutes from the water inlet to the water outlet. Magnetic powder in sludge is separated by magnetic drum according to its own characteristics, and then recovered and recycled in the system. The high gradient magnetic filter captures the residual fine particles in the water flow, and the magnetic filter automatically cleans according to the set requirements to achieve the purpose of highly purifying the effluent. It is reported that BFMS is used for advanced water treatment in the United States, and magnetic filters can remove 26 nm bacteria. The following figure illustrates the processing of BFMS process.
Magnetic separation process of supported flocculation by BFMS method
Flocculation/+loading flocculation+precipitation separation+magnetic filtration
Coagulation+biological flocculation+solid separation+magnetic separation
This technology was rarely used in engineering before, because the magnetic seed recovery technology has not been well solved, but now this technical difficulty has been successfully broken through, and the magnetic seed recovery rate has reached over 99%. This technology has also been demonstrated and operated in American commercial projects. Our company applied for a number of patents in China, which formed our own intellectual property rights. In the past three years, our company has successfully conducted a number of experiments with different operating parameters in urban sewage treatment, reclaimed water reuse, surface water and groundwater treatment, tap water treatment, river water treatment, lake water treatment, high phosphorus wastewater treatment, paper-making wastewater treatment, mine wastewater treatment, oil refining and oilfield wastewater treatment, and achieved good results; 10000 tons/day trial operation was put into operation in Qingdao Licun estuary municipal sewage for one month in May 2007, and the operation was good. The effluent from the sewage treatment plant in Beijing Jinyuan Economic Development Zone has been deeply dephosphorized for more than one month, and the treatment effect is good. As an Olympic emergency urban sewage treatment project, Beijing Qinghe Sewage Treatment Plant has installed six sets of 4× 1 10,000 tons/day and 2× 5,000 tons/day BFMS systems, and the comprehensive treatment effect is good. This technology has been used in the first phase project of Dongying Shengli Oilfield (5000 tons/day) to treat the oil production sewage of Shengli Oilfield, and the 500 tons/day groundwater BFMS project and the 30000 tons/day oil production water BFMS project are also being implemented.
Compared with other processes, magnetic separation technology has the following advantages:
1) BFMS process can be applied to primary, secondary and tertiary municipal sewage, reclaimed water, various industrial sewage and drinking water.
2) The treatment effect is good, and the effluent quality is equivalent to that of ultrafiltration membrane. BFMS process can effectively remove particulate pollutants, microbial pollutants and some pollutants that have been dissolved in water, such as COD, BOD, suspended solids, total phosphorus, chromaticity and turbidity, especially for phosphorus. It can also be combined with biological method to remove nitrogen very effectively and economically.
3) Strong impact load resistance and unique impact resistance to water quality. When there is a problem in the previous process or other harmful metal ions enter the sewage treatment system, the sewage can directly enter the magnetic separation system, and the system can still maintain a high removal effect and greatly remove pollutants in the water.
4) The floor space is very small. The building area of 20000t/d BFMS system is about 400㎡, and the total building area of walkway, dosing and operation facilities is about 700㎡.
5) Less investment and obvious advantages over membrane treatment.
6) Low operating cost and long service life of equipment. In addition to normal maintenance, there is no need to replace parts, and the secondary investment is high.
7) Convenient operation and management, quick start and simple operation and management.