Study On Ammonia Nitrogen Wastewater Used In Circulating Cooling Water For Acid Production And Anti-scaling

With the increasing consumption of water resources and water pollution,water shortages have gradually become a bottleneck for human social and economic development.In addition,with the construction and the extraordinary development of the power industry,thermal power plants,which are large water users,have already targeted the recycling cooling water to the zero discharge of power plant water systems.Circulating cooling water has the largest demand for water in the whole plant,and it also has the greatest potential for water saving.Therefore,most power plants are seeking high recycled water concentration ratios to reduce the amount of fresh water and the discharge of concentrated water.When ammonia nitrogen is added to circulating water(amination operation),the circulating water system can provide a suitable growth environment for Nitrobacteria.They perform nitrification in circulating water towers,converting ammonia nitrogen into nitrous acid and nitric acid.That is equivalent to adding acid to the circulating water to reduce the alkalinity and reduce the scaling factor.As a result,the concentration ratio of recycled water can be increased,and the addition of circulating water treatment chemicals and the discharge of concentrated water can be reduced.This article starts from the study of enrichment culture of nitrifying bacteria,detection of nitrifying bacteria by fluorescence in situ hybridization,activity of nitrifying bacteria,and influencing factors.The Feasibility and Related technologies of Circulating Water Ammonia Treatment to Increase Concentration Ratio of Recycled Water have been studied.(1)Enrichment of nitrifying bacteria from aerobic activated sludge from sewage treatment plants.After 20 days,the MLSS,SV and SVI trends of mixed liquid sludge gradually became flat.The nitration strength of activated sludge increased from the initial 0.038mg(NH4+-N)/(ML· 24h)to 0.264mg(NH4?-N)/(mL·24h).The main microorganisms in activated sludge are ammonia oxidizing bacteria,and there is basically no nitrite oxidizing bacteria.And the experiments proved that the acid is produced by ammonia oxidizing bacteria.Fluorescence in situ hybridization method can detect ammonia oxidizing bacteria concentration in sludge within two days.Its bacterial concentration is 3.07×106cells/mL.(2)In the case of adequate dissolved oxygen and inorganic nutrients,the pH range is 7.2 to 7.8.The rate of acid production by ammonia oxidizing bacteria is 0.1509mmol/(mL·24h).With the increase of ammonia nitrogen concentration,the activity of ammonia oxidizing bacteria has gradually increased.Biocide of quaternary ammonium salt and 1227 have a greater impact on the activity of ammonia oxidizing bacteria.When the dosage is 25mg/L,the inhibition rate can reach over 90%.When the dosage of isothiazolone is 25 to 100 ppm,the inhibition rate of ammonia oxidizing bacteria is between 50%and 80%.And the concentration increased,there was no significant change in the sterilization rate.(3)Static test and dynamic simulation test proved that under the condition of not adding biocide,by controlling the concentration of ammonia nitrogen in water,the acid produced by ammonia oxidizing bacteria can reduce the increase of alkalinity in the process of circulating water concentration,and the pH value can also be controlled stably.However,after the addition of biocide,the activity of ammonia oxidizing bacteria is greatly affected.Therefore,it is necessary to increase acid production by adding additional nitrifying sludge.Ammonia oxidizing bacteria mainly grow on the packing layer of circulating water cooling tower.Its ammonia oxidizing bacteria concentration is in the order of 105?106cells/g,which contains more than 90%of total ammonia oxidizing bacteria in the entire system.10%of ammonia oxidizing bacteria grow on the sludge at the bottom of the storage tank,there is basically no ammonia-oxidizing bacteria in the storage tank.