3D-RBC+BCO Combined Process For Treatment Of High Ammonia Nitrogen Wastewater And Its Biological Characteristics

Most of the high ammonia nitrogen wastewater pollution sources from agricultural non-point source pollution in China,and also one of the key issues addressed by the national“13th Five-Year Plan”water pollution prevention and control action plan.The concentration of pollutants such as COD,NH₄⁺-N and SS in high ammonia nitrogen wastewater of livestock and poultry breeding wastewater is very high,and discharge into the receiving water will cause potential harm to the ecological environment and human health.The existing treatment process is mainly based on the combination of anaerobic-aerobic or anaerobic-natural processes,which has a good removal of conventional organic matter,but it is still difficult to remove high-concentration ammonia nitrogen.In view of the difficulty of removing high-concentration ammonia nitrogen in such wastewater,it is imperative to develop efficient and economical water treatment technology.In this study,the raw swine wastewater after the solid-liquid separation of the pig farm and the biogas liquid after anaerobic fermentation were taken as the research objects.In view of the characteristics of high organic matter and high ammonia nitrogen in the raw,based on the partial heterotrophic nitrification-aerobic denitrification?HN-AD?compound bacteria have the characteristics of high ammonia nitrogen resistance,high organic matter and high efficiency nitrogen removal.The membrane-hanging technology has built a three-dimensional structure rotating biological contactor+biological contact oxidation?3D-RBC+BCO?combined process.The aerobic 3D-RBC pretreatment is used to replace anaerobic fermentation,the carbon source in the raw swine wastewater is fully used for denitrification,and the source is significantly reduced in pollutant concentration;the 3D-RBC effluent is further processed with the help of the BCO unit to meet the discharge requirements.The start-up process of 3D-RBC and BCO unit microbial inoculation,the removal effect of pollutants in the parameter optimization stage,and the changes of microbial community structure were studied.According to the water quality characteristics of biogas slurry oligotrophic and high ammonia nitrogen,the 3D-RBC+BCO combination process was started by using the HN-AD compound bacteria hanging film that is resistant to high ammonia nitrogen and adapts to poor nutrient growth.The start-up of microbial agents under oligotrophic conditions was studied,and the effects of dissolved oxygen?DO?concentration and C/N ratio on pollutant removal were investigated.At the same time,with the help of high-throughput sequencing technology,the micro-mechanism of combined process can still be used to efficiently denitrify under oligotrophic conditions.The main conclusions are as follows:1.The 3D-RBC pretreatment pig farm raw wastewater was started using the HN-AD compound bacteria hanging film,and it took only 15 days to complete the 3D-RBC fast film hanging.By adjusting the linear velocity and C/N of the disc,the enrichment of HN-AD bacteria in the reactor and the start of the process were achieved in only 65 days.Using this process to deal with the original liquid,the removal rate of COD,NH₄⁺-N,TN is as high as69.8%,87.9%and 79.5%,the pollutant reduction effect is significantly better than the traditional process.High-throughput sequencing results indicate that the dominant bacteria with HN-AD function in the biofilm gradually changed from Halomonas,Acinetobacter to Comamonas,Hydrogenophaga,etc.,and the relative abundance of the latter gradually increased.Scanning electron microscope results are also consistent with the results of biodiversity analysis,confirming that Comamonas and Hydrogenophaga play a major role in reducing the source of ammonia nitrogen.2.The 3D-RBC effluent was treated with the HN-AD bacteria biologically enhanced BCO process.In the early stage of sludge acclimation,it was found that when the concentration of NH₄⁺-N is higher than 500 mg/L,the removal rate of pollutants is significantly reduced.After being biologically fortified with HN-AD,the tolerance of NH₄⁺-N concentration can be higher than 600 mg/L and can maintain efficient removal of pollutants.Using HN-AD biologically enhanced BCO to treat 3D-RBC effluent,the average removal rates of NH₄⁺-N,TN and COD were 86.9%,70.5%and 74.4%,respectively,and the effluent concentration was much lower than that of Limits of Pollutant Emission Standards for Poultry Farming?GB18596-2001?.High-throughput sequencing results showed that the dominant bacteria belonging to HN-AD bacteria in the biofilm increased from the genus Alcaligenes to the biologically enhanced Diaphorobacter,Acinetobacter,and Thauera,and the relative abundance of Acinetobacter significantly higher than the inoculum.It is confirmed that HN-AD bacteria such as Acinetobacter play a key role in the deep denitrification of 3D-RBC.3.Under real biogas slurry conditions,using HN-AD compound bacteria as inoculants,only 12d and 18d were used to complete the 3D-RBC and BCO reactors,respectively.The removal rates were stable at 94.8%,95.7%and 80.1%,respectively,and the effluent was better than the Class B standard of urban sewage plants.In the process of optimizing the DO and C/N ratio of the 3D-RBC reactor,the removal rates of COD,NH₄⁺-N and TN and other indicators after the addition of the bottom exposure were reduced by 25.4%,15.4%and15.5%,respectively.High-throughput sequencing results showed that the biodiversity of the3D-RBC disc biofilm increased significantly after the increase of the bottom exposure,but the abundance of HN-AD dominant bacteria was significantly reduced,resulting in a reduction in denitrification efficiency;oligotrophic Acinetobacter,Pseudomonas bacteria Genera is the key to 3D-RBC's efficient denitrification of real biogas slurry.Increasing the C/N ratio will significantly reduce its abundance,which will affect the denitrification effect.