Characteristics Of The Typical Northern Water Resource Algae And Its Impact On The Water Plant Treatment Efficiency

Above 30%of our city water resources are the lakes and reservoirs,providing more than 20% supply water.In the drought northern city,lakes play more important roles.However,in recent years,due to various factors,such as internal and external pollution,globe warming and adverse management,lakes and reservoirs water quality deteriorating keep worsening and eutrophication become worse and worse.Associated with eutrophication,many species of phytoplankton, especi(?)of algae cause the water bloom.A large number of algae not only affect the water landscape,but also deteriorate the water quality,and increase drinking water treatment difficulty and cost.Furthermore,the algae toxin causes serious health hazards released by algae,which pose a serious threat to urban water supply security.However,the conventional treatment process,in which solid and bacteria suspended is used as treatment aim,is limited for algae-laden water.The production costs are doubled,while it is hard to guarantee the supplying water quality.Thus,the algae impact has become a common problem to drinking water industry,.Reasonable and effective algaecide technology becomes a research focus.At present,the algaecide technology in drinking water develops rapidly,and has developed a series of treatment technologies such as the physical,chemical and biological methods.However, there are two problems of these results mentioned above:ⅰ) the research only focuses on the treatment process improvement,but gives little regard to the community structures of algae, which is real determinant factor for water quality characteristics and treatment difficulty;ⅱ) most of these algaecide process need increasing facilities and equipments and operation costs.In this paper,a water plant in Changchun has been taken as the study object.First the algae species structure and its changes regulation in the Shitoukoumen reservoir is studied.The evaluation results of the reservoir water quality in 2005～2008 show that except iron,other targets can meet surface water environmental standardsⅢand the reservoir are suitable as a source of city drinking water.But the nitrogen and phosphorus of reservoir has reached the level of middle eutrophication.The monitoring results showed that algae indexes indicate obvious seasonal characteristics:in winter,algae concentration is 5,000～10,000/L,chl-a is 0.8～1.2μg/L; in spring,algae outbreak increase sharply,from 10,000/L to 300～400×10~4/L.In summer and autumn,algae density can achieve 1100×10~4/L.The algae species proportion are significantly different in different seasons:in spring,green algae and diatoms dominate,while cyanobacteria and green algae dominate in summer and winter.Monitoring results also showed that,a strong hydraulic disturbance prevented the stratified water bodies,which make algae distribution was essentially the same on the vertical direction.Comparative analysis from temperature,light intensity,N/P,DO,pH,turbidity and Fe,come to the conclusion:to the northern reservoir algae, the water temperature and the water body changes is the most critical factor.The effect of algae on water plant treatment has been analyzed systematically considering the production data,from treatment efficiency,agent consume and filter running.In treatment efficiency:sedimentation and the filter effluent turbidity are 4.5NTU和1.3NTU in high algae period,which are higher than that of other period.The small size floating particles,floats out of the sedimentation tanks,increases the filter handle load.The consumption of agent:the average dosage in high algae period is 1.7 times of that in other period,even reachs 2.8 times in 2000.It can be seen that the existence of algae has made a substantial increase in the chlorine and coagulant agent of water plants in order to guarantee the water quality.In filter running:filter is plugged rapidly by the algae and the filtration cycles(serious only 2～3 hours) is reduced sharply. In severe cases,a chain of filter failure may even trigger.Over the years,the chain of filter failure is most serious in Jul and Aug,which is just the Shitoukoumen reservoir maximum period of the algae outbreak.The monitoring results of the algae removal rate of the plant process show:algae removal rate of sedimentation tanks is low at 40.4%～56.8%;the total removal rate of water plant can only reachs 54.6%～76.4%.The sedimentation's algae removal rate is 45.3%in high algae period, which is lower than that in other period.The total removal rate is 73.6%higher than 67.9%of the other period.Because the recycling tank keeps more stable environmental conditions,and the filter backwash water recovery system is just in the blank area between pre-and post-filtration chlorination,the backwash water recovery system has became another source of algae,cyclops and bacteria.In high algae period,shitoukoumen reservoir's algae density is more than 10~7/L,and mainly of them are the small-size cyanobacteria and green algae.Because micro-algae have the larger specific surface area,a large charge is required to compress the electric double-layer.The four coagulation removal mechanisms are limited on the micro-algae.In view of this,the PS is introduced into PAFC as a catalyst and stabilizing agent,so a new type algaecide flocculant CSPAFC is developped.Applying composite and copolymerization method,two types CSPAFC are prepared in the laboratory.By transmission electron microscopy,X-ray diffraction and electrical experiment,the new algaecide coagulant microcosmic characteristic is studied.The CSPAFC prepared by copolymerization is less crystalline,better micro-disordered and have higher degree of polymerization,which means that the product quality is more stable;the relatively high internal spatial structure means that it has better ability to bridge and absorption in flocculate reaction;at the same time,the electrical properties experiments show that the copolymerization method CSPAFC electricity ability in flocculation is more advantaged. Through the coagulation experiments for Hun-River micro-polluted water in winter,the new coagulant was investigated from the treatment efficiency and economic factors.The results indicate that,assisted by PAM,CSPAFC have the better treatment capability than the conventional coagulant for the micro polluted water.CSPAFC,prepared by copolymerization, has the best removal result of turbidity,color and CODmn,and shows more obvious economic advantages.The high algae water coagulation experiment in object water plant indicates that, compared with the conventional flocculant,CSPAF has the better treatment effect,in effluent turbidity,effluent aluminum and algae remove rate.At the optimal dosage conditions,2# CSPAFC has the better treatment effect than that of 1 #,especially the algae removal capabilities. While the algae removal capacity is the key to the development of new flocculant goal.Detection of products microstructure and coagulation treatment experiment shows that the CSPAFC,by copolymerization,has a distinct advantage at quality and treatment performance. On this basis the copolymerization method CSPAFC production process of the preparation is carried out.From the three stages production applications test in object water plant,the results show that: the new coagulant is better than the traditional ones.When the raw water turbidity increased sharply from around the 10 NTU to 40 NTU,using a new flocculant,has the more stable treatment effect.The sedimentation effluent turbidity is less than 3.6 NTU.while the conventional coagulant treatment system reached 4.4 NTU.During the stability running period, the test result of organisms and algae in filter effluent and disinfection by-product in finished water show that:the new coagulant has obviously technological superiority.In the process optimization,through on-site verification testing of the water plant flocculation process parameters showed:the water plant flocculation tank water dynamical conditions are not reasonable,velocity gradient exist including a sudden increase in the middle of the reaction.That affected the efficiency of coagulation treatment.But the rate of perforation of the holes flower wall at the end of flocculation tank was low,easily to make particles broken.On this basis, through the simulation coagulation experiments,process reconstruct plan has been brought forward.Optimized five-stage reaction GT are,respectively,(98.1,2),(72.6,3),(49.4,5), (28.6,10),(11.3,25 ).That was the design basis for the process reconstruct.In order to inspect actual results of the process of reconstruct engineering,the parallel treatment experiment and limits of load test were carried out,between reconstructed flocculation tank and not modified flocculation tank,during the reconstruction engineering.The parallel experiment results show that:the water dynamical of the modified flocculation tank is more reasonable,sedimentation effluent turbidity stabilized at 1NTU below,the algae removal efficiency is better than non-modified flocculation tank.At the same time,the water plant agents consume reduced significantly,which reduce the flocculant consume by 53%and coagulation aid by 50%on average.And the limit load test shows that,to ensure that water quality in premise, the maximum capacity of non-modified flocculation tank was 2700m~3/h,while the treatment ability of the modified flocculation tank could reach 3200 m~3/h,increased by 18.5%than the original process. Comprehensive comparison production data,it can be concluded that:after the agent strengthening and process optimization,the treatment efficiency improved significantly in high algae period and period of low temperature and low turbidity.In high algae period,the effluent turbidity decreased from 0.96NTU to 0.21NTU,and after filtration the total removal of algae increased from 70.6%to 96.7%.While in period of low temperature and low turbidity,the effluent turbidity decreased from 0.92 NTU to 0.33NTU,and after filtration the total removal of algae increased from 81.5%to 91.3%.The water plant runs stably in the 2008,and after the implement of technical achievements,the effluent turbidity was under 0.3 NTU,meeting the production assessment standards of the water Company.Although the high algae period extended in 2008,the total algae removal rate was 95.9%～96.8%.Through the analysis of the agent cost of water plant,it can be concluded that:after the application of research achievement,consumption has been significantly lower than that of Compare water plant,agent costs of water gradually reduced from 0.107yuan/m~3 to 0.064yuan/m~3,the agent consumption of water plant reduced 40.2%.Accordance with the water plant design capacity of 26.5×10~4m~3/d,pharmaceutical costs saved 4,159,000 Yuan,a very significant economic benefits.In summary,through the agent strengthen and technology optimize to control the algae impact is feasible.To the existing water plants seriously impacted by algae,but unable to increase pretreatment and depth of the existing process,the results of this study provides a practical value.