Study On Depth Treatment Of Nitrogenous Substances In Contaminated Groundwater Based On Electrochemistry And Biofilm Coupled

Groundwater is significant for drinking water sources,however nitrate pollution has been more serious and threatened to human health year after year.It become a worldwide environmental problem in groundwater,and is in urgent need of restoration,treatment and protection.Current research of existing treatment methods had their advantages and disadvantages,aiming at the lack of carbon source for groundwater biological nitrogen removal.Therefore,this study proposed a new technology of biomass + micro-electrolysis chemistry-catalyzed granule coupling carrier,which achieved biological denitrification process coupled with chemical galvanic reactions.It could provide sufficient electrons for heterotrophic denitrifying bacteria and autotrophic denitrifying bacteria to realize high efficiency of nitrogen removal.Thus,the technology could provide new thoughts and methods for depth denitrification for groundwater.In this study,the self-made biomass + micro-electrolysis chemistry-catalyzed granule coupling carrier(referred to as B+MC coupling carrier)was used as filling carrier of processing device.The oxygen environment of shallow groundwater was simulated by constructing aerobic reactor to provide new renovating technology,at the same time,the anaerobic and anoxia environment of deep groundwater was simulated by constructing anaerobic reactor to compare,analyze and explore nitrate removal.The reactor started up rapidly,and biofilm formation was successful at around 15 d.With the removal of nitrate,nitrite,ammonia and the change of COD and pH values in the system as the control index,the process was optimized to achieve efficient nitrogen removal through the analysis of hydraulic retention time(HRT),dissolved oxygen(DO),operation mode and other factors,as well as carbon release rate,loss rate and economic benefit.The results showed that:under the best process conditions of HRT=12 h and DO=2.0?3.0 mg/L,the concentration of nitrate in aerobic reactor was decreased by 29.54 mg/L of the influent to an average concentration of 2.53 mg/L,which average removal rate was more than 91.24%,while under the best process conditions of HRT=14 h the concentration of nitrate nitrogen in anaerobic reactor was treated by 29.54 mg/L of the influent to an average concentration of 1.03 mg/L,which average removal rate was more than 96.32%.The effluent nitrate nitrogen of two reactors could achieve or surpass the class ? standard of "groundwater quality standard"(GB/T 14848-2017).The average concentration of nitrite nitrogen in the effluent of aerobic reactor and anaerobic reactor were 0.02 mg/L and 0.03 mg/L respectively,which met the water quality standard of drinking water.The effluent ammonia nitrogen of the aerobic reactor was less than 0.50 mg/L,which also reached the drinking water quality standard.The two reactors maintained good nitrogen removal for long term operation about 120 d without clogging.The relationship between the structure and function of microbial community in aerobic reactor and anaerobic reaction was analyzed by high-throughput sequencing technology.The results showed that the dominant bacteria in two reactors had denitrification functions(such as Thiobacillus,Ferritrophicum,Denitratisoma,etc.),and some bacteria had the function of degrading cellulose(such as Clostridium,Longilinea,etc.).The coupling relationships between heterotrophic denitrification,autotrophic denitrification and galvanic reaction in two reactors were discussed.This study could provide a more economical method for groundwater remediation contaminated by nitrate or ammonia,without additional carbon source or buffer and no secondary pollution.