Research On Biological Aerated Filter For Polluted River Water

BAF has higher energy consumption. Therefore, optimize the operation mode of BAF is significant for saving energy and reducing the operation cost of DWTP. In addition, a depth study of the structure of microorganisms and function bacteria of BAF would be helpful to the further understanding of BAF system, guarantee the stability of the system and improve the system process efficiency.In this study, a bench-scale and a pilot-scale BAF were established and use vocanic rock as the filler. The feasibility of pretreatment polluted raw water was investigated by a continuous bench-scale BAF under the air/water ratio of 1:1, flow rate 50 L/h, rate of filtration of 6.4 m/h. The results showed that BAF has a great ability to treatment polluted raw water during the experiment year. Temperature should be the main factor affecting biological reactor, however, the treatment efficiency of NH4+-N all greater than 85% by BAF.Based on the above experiment, the feasibility of energy-saving optimization operation was studied by compared with continuous operation mode by using intermittent aeration operation mode(the intermittent aeration circle were 1 h, 1.5 h, 2 h and 2.5 h, respectively), and the removal efficiency of pollutants of BAF under different water temperature was investigated through intermittent aeration operation as well, which showed that intermittent cycle of 1.5 h, in which BAF has an ideal removal efficiency to various pollutants. Among them, during normal temperature period, the average NH4+-N removal rate was 82.27% by BAF, even in the period of low temperature, the average removal rate still can reach 82.21%. Optimization of energy saving operation is feasible.In order to closer to actual engeneering, we expended the study results of bench-scale BAF to a pilot-scale BAF. The results indicated that the pilot-scale BAF still has a great performance during normal temperature period, even at low temperature, the pollutants removal capacity of the pilot-scale BAF was affected by the temperature, BAF still can achieve the aim of pretreatment. Optimized the pilot-scale BAF, researched the applicability of energy-saving optimization operation by compared with the continuous mode. The results indicated that the intermittent aeration is applicable, which can treat pollutants well, and the best intermittent cycle should be 1.5 h.In order to study the depth microcosmic reason of BAF efficiency operation in different period, the dominant and functional bacteria in the pilot-scale BAF were investigated during different water temperature period by molecular biotechnology PCR-DGGE, thus in the operation, to provide reference for the efficient operation of BAF at different periods. The results indicated that the bacterial diversity in the BAF is very rich, dominant bacteria in normal temperature period is Nitrospira, Bacillus, Rhodobacter and Sphingomonas, in low temperature period is Flavobacerium, Exiguobacterium and Clostridium. Nitrosomonas and Bacillus is advantage ammonia oxidization bacteria in normal temperature period, Nitrosomonas is the advantage ammonia oxidization bacteria in low temperature period. Nitrospira is advantage nitrification bacteria. The dominant bacteria are different during the different water temperature period. Therefore, increasing the influent ammonia concentration, or adding targeted dominant functional bacteria, before water temperature changed, can effectively deal with the fluctuation of BAF removal rate which caused by the temperature change. The results of this study provide reference to an actually operating biofilter in a DWTP.