The Start-up And Operation Of A~2/O Pilot Scale System With Municipal Wastewater

After the municipal wastewater treatment plants (WWTP) has been built up, the first and also the most important problem is how to start up the system economically, rapidly and efficiently. The pilot scale system employed an improved WWTP system and operation method to get successful start-up and stable operation. The main research results are as follows:(1) For the start-up of the pilot scale system, using the primary sediment effluent as the influent to start up the aeration tank,10 days later ,the mix liquid suspend solid(MLSS) concentration was about 220 mg/L,it can not achieve successful start-up.While using raw sewage as the influent to start up the aeration tank under the same cultivation condition,10 days later,the MLSS concentration was around 500 mg/L, the effect was not significant.(2) For the start-up of the pilot scale system, using the raw sewage with amount of primary sediment sludge and some flocculation at the end of the aeration period of culture cycle, the hydraulic loading rate was improved step by step,10 days later, the MLSS concentration in the the aeration tank reached to 3000 mg/L. So it will be very convenient and rapid to start-up the the pilot scale system in this way, what is more, the primary sediment sludge is byproduct,it can be obtained almost without cost, it can also save much human and material resources.(3) The system was operated with 30～50% of return activated sludge(RAS), under10h of hydraulic retention time(HRT), and 12 days of sludge retention time, 100% of mix liquid sludge return, average temperature was 28℃. The average removal efficiency of TCOD, SCOD, NH4+-N, TN, TP reached 80%,83%,98%,55.83%, 40%.(4) Although the system has a good effect on nitrogen removal, the removal efficiency of TP only reached to 40％and kept an effluent phosphate concentration reached to 2 mg/L, large amount of phosphate release has not been detected yet in the anaerobic tank, so the system is weak in phosphate removal. According to the ORP instrument ,in anaerobic tank ,the ORP reached to 40mv, and large amout of nitrate significantly affects the release of phosphate. So it needs to induce the growth PAOs in the next step.The feasible way is to enlarge anaerobic tank and change return activated sludge ratio.