Research On Partial Nitrification Performance And Characteristics Of Urban Sewage

In recent years,the nitrogen removal process via nitrite have attracted more and more attention for its carbon saving , aeration saving and less sludge production,etc. At present, this type of process has been successfully applied in high ammonia water treatment. For example, sludge digestion, landfill leachate, etc. If this type of technology has been used in domestic sewage treatment, it will bring in huge economic and social benefits. Recently, people have done a lot in this respect., but still no breakthrough. The main reason is that, the partial nitrification of domestic sewage has not been resolved. Thus its application is limited.The goal of this topic was the stable partial nitrification of domestic sewage. It had propose a joint process for domestic sewage treatment, this joint technology was UBAF +partial nitrification+ANAMMOX. The partial nitrification reactor taken the form of UBAF. In this experiment, the partial nitrification properties of the actual domestic sewage had been fully investigated. The test results are as follows:1) The start-up and stable operation of UBAF was adequately studied. The optimal ratio of air to water, inflow CODcr loading, backwashing cycle time was 3.8:1, 3.0 kgCODcr /(m³ ? d), 6 7d respectively in this BAF formation and the way of inflow. In these conditions, the secondary effluent was keep stable at low COD (<70mg / L), high nitrogen retention rate (> 85%). To sum up, the key to ensure the success of start-up and stable operation were the up-flow way of the influent and the limited DO concentration which was maintained at a relatively low level (<1.5mg / L).2) Around 100 days,the sub-nitrifying reactor was successfully launched at high TIC concentration through room temperature (19℃) and mild temperature(33±1℃),the nitrite accumulation rate of the effluent was more than 90%. The startup mode of high TIC and mild temperature provided a reference for the quick startup of sub-nitrifying of low substrate concentration domestic sewage. SEM electron micrograph showed that after the successful startup of the reactor, the bacteria within the reactor was mainly Nitrosomonas genus (Nitrosomonas), and showed a cluster aggregation growth.3) The substrate along the sub-nitrifying filter was investigated. The statistics showed that 20 80cm height along the filter is the primary nitrosation reaction zone, 81.9% of the NH4 +-N and 85.2% of the NO2 -- N removal were obtained in this interval. And the average of NO₂^--N generation rate is 0.40 kg / (m³Â·d); SND is also relatively severe, TN removal rate was 25.6%. 4) The influence of hydraulic loading, COD concentration, DO concentration, alkalinity /TIC concentration, temperature and backwashing on nitrification performance was studied. The results showed that: the optimal hydraulic loading was 0.40m³ / (m²Â·h), the optimal DO concentration in the reaction zone was 1.2 1.8mg / L; An appropriate increase in influent COD concentration (less than 120mg / L) would enhance the SND effect, and did not affect the rate of accumulation of nitrite. TIC concentrations in normal domestic sewage (about 80mg / L), can obtain a more satisfactory effect of nitrite (nitrite accumulation rate of 82%, the accumulation level of 25mg / L); The mild temperature (30 35℃) was the most favorable condition for nitrite accumulation, which was the main reason for the achieving and maintaining of a high level nitrite accumulation.