Characteristics And Efficiency Investigation Of Suspended Carrier Biofilm For Treating Highly Concentrated Organic Wastewater

Biofilm process as a biological wastewater treatment process has its own unique traits compared to activated sludge process. Investigation performed on the mechanism of biofilm formation and detachment is helpful to know the working principle of biofilm, which gives instructions on how to maintain appropriate biofilm thickness and obtain relatively higher biofilm activity, also provides theoretical support for the application of biofilm process in practical wastewater. What's more, it's very significant to develop novel and effective and stable biological process for the treatment of highly concentrated and toxic organic wastewater, which are really needed and can greatly improve the current deteriorated environment. In this dissertation, a new tube chip type of polyethylene that was mixed with nano-size inorganic materials was used as bio-carrier for the moving-bed biofilm reactor (MBBR). The mechanism of biofilm formation and detachment grown on this kind of suspended bio-carrier, the treatment efficiency and effectiveness of this bio-carrier in the removal of C,N nutrients from highly concentrated wastewater and the feasibility of shortcut nitrification of low C/N ratio wastewater were investigated.The mechanism of biofilm formation and detachment was first investigated. The concept of biomass flux and biomass retention time (BRT, also called biofilm age) was proposed and defined. And a mathematical expression of biomass flux was derived from the combination of substrate balance and microorganism growth kinetics, which can describe the correlations between attachment, detachment, growth and decay in biofilm. BRT determines and indicates the average retention time of cell or particles in the biofilm. The BRT was measured by experiments at different dilution rate. It's found that the dilution rate was a crucial factor to BRT and BRT played a great role in the biofilm structure, activity, composition and sludge production in the biofilm process. Results showed that the biomass flux increased but overall BRT decreased with the dilution rate increasing. As the dilution rate was increased from 1 to 8day-1, The biomass flux increased from 0.2852 to 2.1001 gSS/(m2·d) and the corresponding BRT decreased from 13.12 to 2.49day. Shorter BRT...