Experimental Research On Removal Of Algae In Feedwater By Microwave-enhanced Coagulation Process

In recent years, the phenomenon of eutrophication in many lakes and reservoirs are more and more serious, resulting cyanobacteria bloom. This phenomenon not only cause serious environmental pollution, but also led to the shortage of domestic water resources in many areas.The removal of alage by traditional process in water treatment plant is poor, especially during the outbreak of blue-green algae, a large number of algal cells is difficult to completely kill, then it lead to algae regeneration, not only reduce the final algae removal efficiency, but also seriously affect the normal operation of the water treatment system. In order to improve shortage situation in current water, sucessed in using algae-containing water for urban water supply, this article intends to use microwave enhanced-coagulation to eliminate algae. The experimental study designed to examine the feasibility of new technology, and to explore the best mode of operation and operating parameter, and simple design to improve the water supply process, give a comprehensive evaluation, to provide technical reference for future equipment research and practical engineering applications.Firstly, use two modes of operation (ie,"Microwave irradiation+coagulation, microwave pretreatment-coagulation) to complete microwave enhanced-coagulation for algae removal experiments by using single factor test, those factors include coagulant types, mixedthe dosage of coagulant, the influence of influent pH, the microwave power and irradiation time. Then give a preliminary analysis generated the possible reason for the existence of this phenomenon, the experimental results show that in-several commonly used coagulant, the PAC is best, while the raw water pH value in the range of8-9.Secondly, the contrast in the the three coagulation conditions under algaecide effect showed that microwave irradiation has a good coagulant effect, especially "microwave pretreatment-coagulation," works best, such as, using the drug dose approximates the same algaecide rate of about73%, only conventional treatment dose of about1/4; coagulant dosage is similar to60mg/l, algae rateup to93.6%, compared with the single coagulation method is higher than52.2%.Finally, the combination of the orthogonal experiment comprehensive analysis of the most important factor is the microwave power, followed by coagulant dosage of PAC, again for the irradiation time; optimal process parameters:microwave power700W, irradiation time2min mixedcoagulant PAC dosage of50mg/L, influent pH value of8-9, algae removal, turbidity and suspended solids removal rates were95.6%,93.0%,96.8%, water turbidity1.7NTU, suspended solids concentration of2.37mg/L.Microwave could completely kill effect algal cells; bioassays found no significant effect on the structure of the algal cells after moderate or strong microwave pretreatment, on the surface there is no release of intracellular substances, indicatingwithin a certain range of security; algae floc characterization by SEM and found that the microwave enhanced coagulation treatment with algae floc is more dense than the single coagulation containing algae floc, gathered more. Preliminary analysis of the microwave enhanced coagulation and efficient algae removal mechanism due to the biological effects of microwaves and speed up chemical reactions mechanism, microwave improve the algae aggregation and precipitation, thereby enhancing the effect of removing the algae coagulation and sedimentation.The technology can be realized to a certain extent enhanced coagulation for algae removal, lower cost of water is feasible.