Study On Chemical And Biological Characters Of Biofilm Attached On The Porous Carriers

Rapid industrialization in developing countries has resulted in generation of large amount of effluent day by day. Looking for a reasonable way to wastewater treatment and without producing secondary pollution is the problem to be solved. Nowdays, biofilm is the most commonly used biological method to treat the effluent.This study regarded crushed stone globular aggregates(CSGA) as carriers for wastewater treatment. About this study,measuring water quality indicators and biological indicators of different spaces in the large-scale pilot plant. Biofilm thickness is measured by CLSM.Biofilm activity is measured by FCM and CLSM separately and comparing this two methods. Besides all, this study also contains a same system without carriers to compare excess sludge with the system having carriers. Kriging spatial interpolation method is used to analysis datas getting following results:1 Concentration of COD is decreasing with the increase of the height from the bottom of pilot plant, and decreasing along the flow direction; Concentration of T-N and T-P do not change a lot; concentration of T-N decreased along the flow direction.2 When biofilm thickness recached 28.5 μm, biofim activity and COD removal reach maximum value. It is more useful for microorganism to decompose organic substances, so biofilm activity plays a positive role on COD removal. When biofilm thickness recached 27 μm, biofilm activity become 72%, it is the best time for removing T-P. When biofilm thickness recached nearly 27.8 μm, biofilm activity become 76%, concentration of T-N fall below the minimum value, removal rate of T-N has perfect effect.It is helpful to remove organic nitrogen, When biofilm thickness recached 28.5 μm,biofilm activity become 82%, NH3-N reach the best removal. So when the biofilm thickness should be controled from 27 to 28.5 μm,it is the best condition for all kinds of organic matter in water to remove.3 The system without carriers produce amount of excess sludge is about 10 times of the denice with carriers, so CSGA also play an important role on excess sludge reduction inlarge-scale pilot plant.4 Comparing two methods of measuring biofilm activity(FCM,CLSM), It shows the data from CLSM is a little higher than FCM, but measurement data were analized by Paired-sample T test with SPSS, P=0.296>0.05 These resluts indicate that there are no significant difference between both of measurement methods.So, requirements of biofilm thickness and biofilm activity is different for different organic matter. Controling biofilm thickness is the major key for wastewater treatment.The results of this study provide a theoretical support of gravel biofilm process design for excess sludge reduction in situ.