Electric Flocculation Depth Study Of Nitrogen And Phosphorus Removal

Although Domestic wastewater belongs to organic wastewater of relatively low concentration, the content of organic polymer material and nitrogen, phosphorus and other nutrients are also in high levels. As the increasing of activicies of environmental resource development by human, a large number of domestic wastewater, industrial wastewater contained nitrogen and phosphorus nutrients are discharged into the rivers and lakes, increasing the load of water nitrogen and phosphorus, which the direct consequence is eutrophication. Therefore the development of urban secondary wastewater treatment plant's nitrogen and phosphorus removal process is imminent.Electrolytic flocculation technology is a water treatment technology developed in recent years and possesses the distinctive feature of efficiency, stability and no auto-adding chemical agents compared with traditional methods. However we don't pay sufficient attention to it due to the issue of energy consumption. In this paper, we use electric flocculation to deeply treat the outlet of secondary treatment and explore its effect of nitrogen and phosphorus removal.The test uses dual aluminum plate and study the effect of treatment by respectively changing the electrolysis time, plate distance, current density, pH value of raw water and other parameter, according to the indicators of the removal rate of NH3-N, TP and COD; orthogonal test method is used to obtain the best operating conditions of treatment.The effect of flocculation is poor because of the short electrolysis time; current efficiency will be reduced, and power consumption, aluminum consumption and processing costs are increasing due to the long electrolysis time. Electrolysis time should be controlled within 30 min; the effect of electrocoagulation is best within the neutral and alkaline conditions; with the increase of current density, the removal rates of COD, NH3-N, TP are also increased, the current density can be controlled in 7.82-15.6A/m2 considered the energy consumption; COD removal rate is decreased with the increase in plate spacing, plate spacing on the impact of phosphorus removal rate is not great, ammonia nitrogen removal rate is increased as the electrode spacing decreased, the electrode spacing can be controlled within the limits of 1.0-2.0cm as the other factors are taken into account in actual applications. These four influencing factors of the electrolysis time, pH value of the raw water, plate spacing, current density in single factor analysis are carried out by orthogonal test, and in final comprehensive balance, we obtain the best test solution of pH value of raw water 8.0, plate spacing 1.5 cm, current density 15.6A/m2, electrolysis time 25min.The test calculates the consumption volume of the electrode material by handling 1m3 of water through weighing before and after experiment electrode material's net weight, and finally the aluminum electrode's consumption is 2.5g/m3; we use the electric current, voltage and electrolysis time in flocculation process to calculate the power consumption of the outlet of secondary treatment by electrocoagulation, which is 5 degrees/ton finally. The test use electrocoagulation to deal with the outlet of secondary treatment in urban wastewater treatment plant, the final of test are COD removal rate reached more than 70%, TP reached over 70%, NH3-N above 30%. COD and TP concentration after deeply treated have reached the GB18918-2002 first-class A level standard by electrocoagulation.