Research And Application Of Micro-energy Consumption Pressurized Precipitation Cyanobacteria Treatment Technology And Equipment

The deep well pressurizing device and the double tank parallel pressurizing device have been proved to have a good treatment effect on the cyanobacteria accumulation with very low energy consumption in the previous studies.This paper intends to develop the pressurized dual-cyclone precipitation concentration technology of cyanobacteria slurry and the parallel pressurized dual-tank algae control vessel which can gather cyanobacteria and inactivate them in the early stage.In this paper,the concentration effect of coagulation and precipitation after pressurized deep well of cyanobacteria pulp in engineering application was studied and the dosage was optimized.Aiming at the double tank parallel pressurized alga control vessel,this paper mainly studies the influence of the internal structure of pressurized alga control vessel on the effluent and the actual alga control effect of pressurized alga control vessel.The main results are as follows:（1）Through the coagulation test,it is concluded that the optimal dosage range of PAC is 14%～26%of the dry weight of cyanobacteria.The coagulation and precipitation effect of pressurized cyanobacteria slurry in deep well is good.PAC dosage mainly affects the effluent quality of pressurized cyanobacteria slurry in deep well,and the lowest effluent turbidity is 1.16～1.88 NTU.（2）Through static precipitation test,it is concluded that the optimal dosage range of PAM is 0.3%-0.4%of the dry weight of cyanobacteria.PAM dosage mainly affects the precipitation rate of cyanobacteria slurry particles.At this time,the precipitation rate of cyanobacteria slurry particles can reach about 47 cm/min.（3）Through dynamic pilot test,the maximum surface load of the sedimentation tank can reach 10m3/（m2·h）.The surface load of the sedimentation tank is related to the outlet mode of the sedimentation tank.The algal slurry coagulated particles of the outlet from the lower hole can be precipitated earlier,and the coagulated particles deposited first can act as a filter layer to intercept fine particles and make the outlet water clearer.The maximum surface load of the outlet water from the lower hole reaches 10 m3/（m2·h）.The maximum surface load of outlet water from the upper hole is only 8.33 m3/（m2·h）.（4）Through actual monitoring,the effluent turbidity of cyanophyll-a slurry with an average solid content of 0.5%is 1.83～8.33 NTU,TN 0.30～5.20 mg/L and TP 0.03～0.26 mg/L after being treated by deep well pressurized coagulation precipitation and concentration engineering with an operating flow rate of 120～150 m3/h.The solid content of concentrated algal mud ranged from 3.54%to 4.98%,and the average solid content was 4.08%.The cyanobacteria pulp was concentrated 8.16 times.（5）Through Fluent hydraulic simulation,the optimal internal structure of the pressure tank is reciprocating with 12 grids.The fresh algae water in the type I pressurized tank（internal and external flow short flow plate）spreads faster,and is easy to mix with the pressurized water in the tank.The fresh water reaches the outlet faster,and the volume utilization efficiency of the tank is low.The diffusion rate of fresh algae water in type Ⅱpressure tank is slow,and the time of fresh water leakage from the outlet is later than that in type Ⅰ pressure tank.Fresh algal water did not escape from the type Ⅱ 12-cell pressure tank until 124s.Therefore,considering the effect of inlet water and economic factors,the optimal internal structure of the pressurized tank is 12 grids of type Ⅱ.Fluent was used to model the pressurized tank of the pressurized algae killing vessel,and two different choke plate forms were designed.The internal structure was separated by 8,10,12 and 14,and the water inlet simulation was carried out.It is concluded that the fresh water leakage ratio of type Ⅱ 12 separated pressurized tank is less at the end of 120s of inlet water.Suitable for engineering structures.（6）A five-day enclosure pressurized algae control experiment was carried out on cyanobacteria blooms with an aggregation area of 470.53 m2 and an initial average concentration of chlorophylls A of 9198.38 μg/L in surface water in the surface enclosure area of Taihu Lake with a processing capacity of 40 m3/h by pressurized algae control vessel.At the end of operation,the chlorophyll-A concentration of cyanobacteria was reduced by 98.7%,and the area of cyanobacteria aggregation was reduced by 93.7%.The pressurized algal control vessel had remarkable control effect on cyanobacteria bloom.