A Study Onthe Carbon Source Loss And Recoveryin The Activated Primary Tank System

The primary tank is a conventional wastewater treatment process which is with simple structure,running stability and favorbale effect,however,the urban sewage would loss abundant carbon source in the traditional primary tank and the nitrogen and phosphorus removal efficiency in the sewage was extremely low in wastewater treatment plant.This study analyzed the phenomena of the carbon source loss in the primary tank.The results showed that the removaefficiency of suspend solid and total carbon chemical demand in the sewage were 56.7±7.73%?43.71±5.42%respectively during the process of primary sedimentation.It can be concluded that the sedimentation of those granular matter in the primary tank was the main reason of carbon source lossin the wastewater treatment plant.In order to illustrate the carbon source recovering capacity in the sewage,the biodegradability of granular matter was detected in this study.The concentration of easily biodegradable organics was low in the sewage(13.1%of COD in the sewage),nevertheless,the slowly biodegradable organics reached up to 51.4%of COD in the sewage.In order to promote the carbon source recovering capacity,the transformation process of slowly biodegradable organics to slowly biodegradable organics should be accelerated.In order to solve this problem,primary sludge fermentation and sludge elutriation were applied to enhance the carbon source recovering capacity as well.This study came up with a new activated primary tank.This new activated primary tank was combined the sludge elutriation unit with the fermentation unit,and this kind of new primary tank was applied in the Xi'an No.4 wastewater treatment plant.The results showed that the SCOD and VFA in primary tank effluent increased 25?35%and 55?65%respectively,which could enhance the nitrogen and phosphorus removal efficiency significantly.Because of the increasing concentration of carbon source in the Xi'an No.4 wastewater treatment plant,the concentration of TN,NH4+-N and TP were 13.2±1.2 mg/L,0.68±0.29mg/L,0.41±0.14mg/L in the effluent of secondary sedimentation tank,which could achieve the new effluent standard in China.