Research On Two-step A/O Process For Chemical-industry Wastewater With High Concentration KN

With the rapid development of economy, the organic chemical industry has developed rapidly. Mass production of emerging organic products resulted that the production of chemical-industry wastewater with high Kjeldahl nitrogen (KN) increased significantly. if such wastewater wasn't effectively disposed and directly discharged into the natural environment, it's bound to cause serious environmental pollution, human health and social development will be adversely affected.The integrated wastewater of a large-scale chemical group corporation is came from many chemical productive equipment, the integrated wastewater mainly contains alcohol formaldehyde wastewater, ammonia wastewater, sulfuric acid wastewater, AC wastewater, PVC wastewater, nylon wastewater, pentaerythritol wastewater, fluorine chemical wastewater, calcium carbide wastewater. On account of the poor discharge regularity, the quality and quantity of this wastewater volatile significantly. because of containing some wastewater with high concentration of KN, such as AC wastewater, nylon wastewater, fluorine chemical wastewater, it also has complex characteristics of containing high organic nitrogen, high Kjeldahl nitrogen, high toxicity, complicated background components. In addition, calcium carbide was used to neutralize the wastewater in the pretreatment, resulting in a large number of wastewater containing calcium and SS, It caused that the A/O-O membrane technology of the sewage treatment plant was inefficient. The concentration of effluent ammonia was severely over standard, some large equipments such as AC equipment was forced to be closed. To solve the above-mentioned problems, based on the original trial process we bring forward and study double A/O nitrogen removal process. Owning to the high concentrations of calcium, We also study the effect of calcium on nitrification with such chemical wastewater.According to the wastewater characteristics and the actual treatment process in this sewage treatment plant. Double A/O technology is put forward and studied, ammoniation of organic nitrogen, removal of carbon, degradation of toxic substances and removal of nitrogen were placed in separate reaction system, the first A/O subsystem was used for the removal of COD, ammoniation of organic nitrogen and degradation of toxic substances; the second A/O subsystem was used for the ammonia nitrification. In order to meet the follow-up development of the group corporation, we study the treatment characteristics and the impact property of the double A/O process under the different concentration of KN. In the 124d' stable operation, in the effluent, the organic nitrogen loading increases gradually from 15mg/L to 100mg/L,the KN loading from 60mg/L to 180mg/L,the COD loading from 400mg/L to 1600mg/L.In the low-nitrogen loading period(the 1st-46th day), the gained parameters of influent were 23.0-59.4mg/L,54.9-90.6mg/L,382.6-804.0mg/L for ammonia loading, KN loading, COD loading respectively. the gained parameters of effluent were 9.5-17.6mg/L,13.4-23.5mg/L,36.4-88.3mg/L for ammonia concentration, KN concentration, COD concentration respectively. The average removal efficiency were 74.80 % ,74.76 % ,92.10 % respectively; In the high-nitrogen loading period(the 47th-124th day), the gained parameters of influent were 51.1-241.5mg/L, 125.8-301.6mg/L,487.0-1691.0mg/L for ammonia loading, KN loading, COD loading respectively.The gained parameters of effluent were 0.6-21.8mg/L,0.9-22.6 mg/L, 51.6-124.9mg/L for ammonia concentration, KN concentration, COD concentration respectively. The average removal efficiency were 88.90 % ,90.30 % ,93.63 % respectively;In the 61st-62nd day, the impact study of KN loading whose concentration was 300mg/L in the influent was performed, 5 days later, the ammonia concentration of effluent decreased to 21.1 mg/L (below 30 mg/L), make pollutant meet the standard steadily; In the 101st-113rd day, the low-temperature simulation study was performed., We canceled heating device to simulate natural conditions in the winter, due to the lower temperature, the effect of nitrification was influenced significantly. the ammonia concentration of effluent was 51.4-72.8mg/L, an average of 58.79mg/L,when the temperature was recovered to 25-28℃, the effect of nitrification recovered speedy, 4 days later, the ammonia concentration of effluent was kept at 15.8-21.8mg/L. The experimental results demonstrate that the double A/O process has good treatment characteristics and impact property with high concentration of org-N and KN. To explore the effect of calcium on nitrification, according to the present situation and the follow-up developments of this Chemical Industry Group Corporation, in the second phase of the trial, We design a 3×3 group reactors with low nitrogen (60mg/ L), medium nitrogen (120mg/L), high nitrogen (180mg/L) concentrations of low calcium (600mg/L), medium calcium (900mg/L), high calcium (1200mg/L) concentration in order to research the effect of calcium on nitrification. The experimental results demonstrate that, in the 45days' stable running, at the low-nitrogen (NH₄⁺-N concentration of 60mg/L) condition, the effect of low calcium (Ca²⁺ concentration of 600mg/L), medium calcium (Ca²⁺ concentration of 900mg/L), high calcium (Ca²⁺ concentration of 1200mg/L) on biological nitrification were not obvious; at the medium-nitrogen (NH₄⁺-N concentration of 120mg/L) condition, the effect of low calcium (Ca²⁺ concentration of 600mg/L) on biological nitrification was not obvious while the effect of medium calcium (Ca²⁺ concentration of 900mg/L), high calcium (Ca²⁺ concentration of 1200mg/L) were significant; at the high-nitrogen (NH₄⁺-N concentration of 180mg/L) condition, the effect of low calcium (Ca²⁺ concentration of 600mg/L) on biological nitrification was not obvious while the effect of medium calcium (Ca²⁺ concentration of 900mg/L), high calcium (Ca²⁺ concentration of 1200mg/L) were significant. At the same concentration of calcium, along with the increase in the concentration of ammonia nitrogen, the ammonia loading of system increased, the efficiency of nitrification decreased.