The Study Of Lake’s Cyanobacteria’s Sedimentation And Concentration After Being Pressured

In order to improve the efficiency of that the cyanobacteria was concentrated and reduce energy consumption, Applied pressure can crushed cyanobacteria balloon, and than the cyanobacteria lose balloon buoyancy to so easy to sedimentation and isolate. This article focused on and studied the effect of cyanobacteria’s natural precipitation,concentration and compaction after pressuring and the impact of compaction height and compaction time for algae mud rate.the effect of cyanobacteria’s coagulation,sedimentatio and compaction after pressuring and parameter optimization of algae mud centrifugal dewater, and on this basis concentrate on pressurized coagulation sedimentation process cyanobacteria dynamic test, resulting in a safe, efficient and economical algal separation processes. The main findings are as follows:(1) When cyanobacteria was pressurized and natural precipitate, the water which content is greater than 99.3% can precipitate, while the moisture content of less than 99.3% was sticky, can not precipitates. Moisture content of greater than 99.3% in the precipitation column algae crowded precipitation rate is between 0.48m/h-1.22m/h, the smaller the higher the concentration of algae slurry precipitation speed. The turbidity of the supernatant after precipitation between 66 ～230NTU, chlorophyll-a concentration of 202～943mg/m~3. The supernatant need coagulation sedimentation process, when dosage of the coagulant is 50mg/L, the effluent turbidity reduced to between 6.69-50NTU, chlorophyll-a decreased to between 30.5-170mg/m~3. After Pressurized cyanobacteria natural sedimentation, moisture content is between 98.1%～98.3%, after 12h two concentrations of algae mud sedimentation moisture content fell by only 0.314% and 0.204%, showing that the time for moisture content of natural settling down algae mud is not obvious. Algae mud’s height difference is 80cm, moisture content of algae mud decreased 0.806%, algae mud concentration time increased to 2.93 from 1.58, showing that the height of the algae mud for moisture content is obvious. Natural precipitation concentrated algae settling velocity is slow, the water is poor, and need secondary treatment, algae water separation efficiency is low.(2) Cyanobacteria rate after pressureed coagulation sedimentation is faster than the natural sedimentation rate, when algae-liquid is the same original, the natural sedimentation’s rate is 0.65m/h, coagulation and sedimentation’s rate reach to 2.24m/h, sedimentation speed increase 3.45 time. The supernatant turbidity can be reduced to 13.3NTU, chlorophyl-a drops to 64.8mg/L, so coagulation and sedimentation is better than natural precipitation. Therefore, further experiments for coagulants and coagulant dosage optimization, optimum dosage of coagulant (PAC) than on dry algae is 1/20, and optimum dosage of flocculant (PAM) than on dry algae is 1/1500, and the optimal dosage suitable for treating water content greater than 99% of the original algal-liquid.(3) When centrifuge dehydrate algae-mud, the overall effect of the centrifugal and energy consumption to select that the best centrifugal rotation is 3000 r/min, centrifuged time is 30 min, and dehydrated algae mud moisture content is 90.60%.(4) The dynamic test is basis on static results, when PAC dosage than on dry algae mass to 1/20, the effluent turbidity dropped to 1.44NTU. Chlorophyll-a down to 5.99mg/m~3, algae-mud moisture content down to 96.59%, algae concentrated 5.7 time, algae water separation effect is obvious. In the best PAC dosage, when PAM dosage than on dry algae is 1/1500, the effluent turbidity dropped to 1.95NTU. Chlorophyll-a down to 6.71mg/m~3, algae mud moisture content down to 96.57%, algae concentrated 5.8 time, so comprehensiving economic effect and water separation technology, optimum dosage of PAC than on dry algae is 1/20, and optimum dosage of PAM than on dry algae is 1/1500.(5) In dynamic tests, for high concentrations of raw algae (water content 99%), when PAC dosage than on dry algae mass to 1/20, turbidity dropped to 4.61NTU chlorophyll-a down to 9.78mg/m~3. In summary, under the PAC dosage than on dry algae mass to 1/20, PAM dosage than on dry algae mass to 1/1500, The separation effect of high concentration algae liquid is obvious.(6) When the water flow is from 6m~3/h to 9m~3/h, turbidity and chlorophyll-a change significantly, turbidity kept 1-4NTU, chlorophyll-a less than 8mg/m~3, but when the water flow to 10m~3/h, turbidity increased to 6.68NTU, chlorophyll-a increased to 12.49mg/m~3. With the increase of the original algal flow, the moisture content of algae mud gradually reduce, moisture content can be reduced to 96.29% minimum. From the view of effect of algae water separation technology, the PAC dosage than on dry algae mass 1/20, PAM dosage of dry algae mass 1/1500, algae influent flow should be controlled less than 9m~3/h.(7) The energy of algae pressurized process is 0.008kw · h/m~3, and the total energy cost is 0.055 yuan/m~3, far less than 0.658 yuan/m~3 of the total energy consumption of existing high-speed rotation process cost. In a similar consumption of drug, the total processing cost saves 0.604 yuan/m~3.