Study On High Efficiency Denitrification Of Landfill Leachate By Intermittent Aeration Sequencing Batch Reactor

Wih economic development and acceleration of urbanization in our country,the municipal solid waste has increased rapidly, which has generated large amount of landfill leachate. If ont treated properly, it will cause serious water pollution. Using traditional biological treatment of landfill leachate such as A/O and SBR, the effluent TN is usually unable to meet the emission requirement. But it always needs to add a large quantity of carbon source which leads to a great increase of the cost. In rencent years, the combined process of UF-NF-RO was widely used in the treatment of landfill leachate in order to make the effluent TN meet the emission requirement of GB16889-2008. But there were serious clogging of the membrance and outstanding membrane concentration polarization. Considering the characteristic of high ammonia, low COD/TN in the mature landfill leachate, the nitrogen removal efficiency in two combined intermittently aerated sequencing batch reactors(IASBR) was investigated. In the experiment period,the sodium acetate was added ioto the two reactors to modulate the COD/TN at about 3. The results showed that the effluent COD, NH4+-N, TN in the raw leachate and first IASBR was 4050 mg?L-1, 1200 mg?L-1, 1500 mg?L-1 and 1100 mg?L-1, 20 mg?L-1, 250 mg?L-1 respectively. The effluent COD and TN in the second IASBR was less than 800 mg?L-1 and 40 mg?L-1. Conditions in the reactors were cotrolled as follows: temperature at(25±2)℃, pH at 8.0 to 8.5, DO at 0.5 to 1.0 mg/L and HRT in the first and second IASBR at 5 d and 4 d. The COD, NH4+-N, TN removal efficiency reached 80%, 98% and 97% respectively. Biodegradable organics, ammonia and total nitrogen were mainly eliminated in the first IASBR, while nitrogen was further removed in the second IASBR to meet the emission requirement of GB16889-2008. Meanwhile endogenous denitrification was found in the first IASBR.The analysis of GC-MS shows there are many organics in the landfill leachate including acids, olefins, alcohols, aromatic compounds and so on. After the secondary treatment of IASBR, acids are thoroughly degraded and toxic matters are decreased greatly. The toxicity test shows the geneic toxicity of the landfill leachate, first IASBR, second IASBR are 51.2, 21.6 and 19.3ug4-NQO/L respectively. After the fisrt IASBR, the genetic toxicity of water quality decreases greatly, while after the second IASBR, it decreases slightly.