| Since 1980s, biological aerated filter has been widely studied and used in wastewater treatment field all around the world. At present, it is a great subject of the sewage treatment technology research field to develop a low consumption, high efficient city sewage treatment technology for small-and-medium-sized towns in China. Developing lateral-flow BAF has offered a new thinking for solving this problem. The research is an innovation for biological aerated filter, lateral-flow biological aerated filter was made by assimilating the running mechanics of traditional biological aerated filter, it possesses the characteristic of clogging-prevented design and separated aeration system, which facilitates both anaerobic and aerobic reaction in one filter through flexible position setup of aeration and back flow spot. The paper mainly studied the hydrodynamic behavior of LBAF reactor; the effect of operational conditions on removal efficiencies of organic pollutants, suspended solids as well as nitrogen and phosphorus, and the method of phosphorus removal by using modified zeolite as well as the interrelated mechanics, besides, biofilm characteristic of LBAF was also discussed through analyzing biomass, biological activity and microorganism distribution. Hydrodynamic behavior on LBAF illustrated that the flow pattern of LBAF was between complete mixed flow and plug flow, and more approach to plug flow. Thehydrodynamic behavior of LBAF reactor was established in terms of diffusion model:With a theoretical analysis, the flow pattern of LBAF was helpful to special distribution of microorganism population and ensured full use of volume, as well as improved treatment efficiency, it was supposed to be a preferable flow pattern.Operating test of LBAF reactor under simultaneous nitrification and denitrification showed that LBAF reactor ran stably and had a strong capacity against impact loadings; removal efficiency of COD,SS,ammonia nitrogen, total nitrogen and total phosphorus increased with the increase of hydraulic loadings, while mean removal efficiency of SS and COD had a slight fall; mean removal efficiency of ammonia nitrogen and total nitrogen changed a lot with the increase of hydraulic loading; and removal efficiency of total phosphorus was low and changed little. When air/water ration increased from 7:1 to 10:1, removal efficiency of COD raised to some extent, and increased slowly until stable when the ratio was beyond 10:1;SS removal efficiency changed little when air/water ratio increase from 7:1 to 10:1 and effluent SS increased as air/water ratio beyond 10:1; when air/water ratio increase from 7:1 to 10:1, ammonia nitrogen removal efficiency got a sharp increase while total nitrogen removal efficiency increased little and more minor change happened when the ratio was beyond 10:1; for total phosphorus, the removal efficiency increased as air/water ratio below 10:1 and changed little after 10:1. Simultaneous nitrification and denitrification was identified through analysis of nitrogenous compounds along the flow path of LBAF under complete aeration, and additional OUR, substrate oxygen adsorption rate as well as bacteria count acted as supplement.Backwash began when water level became high enough to resulting in worsen effluent ammonia. Operation cycle was prolonged due to"S"type flow channel and size grading of the filler adopted along water flow direction, which enhanced the capacity to handle pollutants of the filter bed, thus, head loss increased slowly during operation time and difficult to be blocked.Predenitrification experiment showed that preferable removal efficiencies of carbon, nitrification and denitrification were achieved in the process. Nitrification happened in aerobic zone while denitrification occurred in anaerobic zone. The critical factor for total nitrogen removal in predenitrification process was dissolved oxygen. General dissolved oxygen was higher when anaerobic/aerobic volumetric ratio was 1:6.14 than that of 1:3.76, and 1:3.76 volumetric ratio was employed which favored predenitrification. Total nitrogen removal efficiency changed a little when reflux ratio increased from 1:1 to 2:1, so did COD and ammonia nitrogen.Compare simultaneous nitrification and denitrification with predenitrification, it is clear that simultaneous nitrification and denitrification was preferable when influent COD was low and denitrification was not required. While predenitrification was adopted when nitrogen was required to be removed. If influent COD was high, pre denitrification would be employed although there was no denitrification requirement. The stability of predenitrification was better than simultaneous nitrification and denitrification in removal of COD, ammonia nitrogen and total nitrogen.Removing phosphorus by activated zeolite through adsorption method was an approach based on zeolite structure characteristics, the procedure to make activated zeolite was as follows: firstly zeolite was broken into 0.3~0.6mm, mixed it with MgSO4 and Al2(SO4)3 and ensure the mass ratio to be 2:2:1, secondly adjusted pH to be 8 using NaOH, and stirred the mixture for 30min, then dried the mixture to be solid, and roasted the solid at temperature 300℃for 1 hour. The activated zeolite had strong adsorption capacity for phosphorus in wastewater. And it can be reused by reproduced solution, which was made by 30mL5%NaOH and 30mL5%Na2CO3, the reused activated zeolite still had strong adsorption capacity, after four times repeated reproduction the adsorption capacity basically maintained stable.Mini adsorption dynamic test of activated zeolite implied that, when velocity was 0.41m/h and original phosphate concentration were 6.4mg/L and 3.5mg/L respectively, accumulated processing water were 518.4 and 1022.3 times that of the adsorbent when it attained breakthrough point; when original phosphate concentration were 6.4mg/L and the velocity was 0.35m/h, accumulated processing water was 653.3 times that of the adsorbent when it attained breakthrough point.Through investigation of phosphorus removal from wastewater by adsorption, it is believed that in the course of adsorption, ion exchange, dispersion force and capillary force took an important action and determined the zeolite adsorption capacity.From measurements of biomass and biological activity sampled from fillers of LBAF reactor, it is clear that biomass declined significantly during the operation cycle from stage A to stage B, biofilm activity changed little while bacteria transited from heterotrophic to autotrophic ones. Observation of biofacies showed, biofilm got thinner gradually from stage A to stage B, and the color changed from black to light brown, while along the flow path, with degradation of organic substrate biofacies transmitted from low to top grade, and formed a complete food chain. In conclusion, different location grew their compatible culture to treat wastewater properly.
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