Engineering Test Research On The Expanded Bed Composite Biofilter For Treatment Of The Black And Odorous River

With the rapid development of China’s economy and the continuous improvement of people’s living standards,the water consumption of people’s production and living has also increased rapidly.The resulting sewage discharge has caused river pollution,and black odor phenomenon is becoming more and more common in urban rivers.It’s a serious threat to the physical and mental health of the residents and the construction of the ecological environment.In order to curb the increasing pollution of urban rivers in China as soon as possible,it is imperative to research suitable and efficient methods for treating the black and odorous river.For the black and odorous river,the expanded bed composite biofilter is developed.It adopts special suspended ceramsite filter material,the surface of which is rough,hydrophilic and easy to form the natural biofilm.Its specific gravity is close to water.It is easy to fluidize and not easy to be knotted.The filter head loss is small.When backwashing,water consumption and energy consumption is low.The process integrates purification functions such as pre-filtration pretreatment,reflux denitrification,and biodegradation nitrification.The effluent water quality is stable and reliable.The process is simple and energy efficient.In order to facilitate the process promotion,an integrated equipment of expanded bed composite biofilter was developed and used to treat the black and odorous river,and relevant experimental research was carried out.The equipment is equipped with automatic control and remote control system.It runs automatically,and can also be monitored and operated by mobile phone software to achieve unmanned operation.The equipment is highly automated,compact and less space demand.In addition,valves,pipes,fans and other devices are built in.It easy to install,construct and manage.The river is treated by downstream water intake,equipment purification,upstream water discharge and dilution.On the one hand,the water from the equipment dilutes the river sewage,which reduces the concentration of pollutants in the river.On the other hand,it brings about nitrates and microbial strains,which will help to treatment.The sewage treatment is extended from the equipment to the river itself,which greatly enhances the treatment capacity and has strong impact load resistance.The equipment adopts a two-stage continuous water inlet and natural biofilm formation method and runs continuously for 24 days.The effluent COD_Cr,NH₃-N and TN removal rates reached 75%,95%and 24%.The effluent quality was stable and the equipment was successfully start-up.The effects of influent hydraulic loads,reflux ratios and air/water ratios on the removal of pollutants were analyzed.When the hydraulic load increases,the removal effect of the equipment on COD_Cr,NH₃-N and TN is continuously weakened.When the reflux ratio and the air/water ratio increase,the removal effect of the equipment on COD_Cr,NH₃-N and TN almost increases firstly and then decreases.The results show that the influent hydraulic load is6.25 m³/（m²·h）,the reflux ratio is 75%,and the air/water ratio is 3:1,which is the best operating condition of the equipment.Analyze and research the equipment backwashing.The first filter is backwashed by two methods:upper flushing,air flushing adding lower draining.The second filter uses air flushing and draining for backwashing,The air flushing intensity of the first filter is 8 L/（m²·s）during backwashing,and the air flushing intensity of the second filter is 8¹2L/（m²·s）during backwashing.The first stage filter backwashing cycle is generally 1² days.The second stage filter backwash cycle can reach about 7 days.Equipment backwashing is energy efficient and has a long backwash cycle.The first filter backwashing cycle is generally 1² days.The second filter backwash cycle can reach about 7 days.Equipment backwashing is energy efficient and has a long backwash cycle.The equipment is used to treat the river sewage and it is continuously and stably operated for 15 days under the best operating conditions.The average removal rates of COD_Cr,NH₃-N and TN in the rivers reached 83.7%,95.2%and 26.1%by equipment.The river has almost no removal effect on NH₃-N,and the average removal rates of COD_Crr and TN reached 62.4%and24.3%.The average removal rates of COD_Cr,NH₃-N and TN in the rivers reached 76.9%,51.9%and 50.1%by comprehensive treatment.In the absence of dredging and interception,the rivers after the treatment have achieved the goal of not being black and odorous,providing new ideas for the treatment of the black and odorous rivers.