1.下水道管線在頂冠及靠近常水位的位置常会生腐蝕,進而影響下水道管線的壽命,說明造成下水道管線腐蝕的原因及可能的控制方法。(15分)

7. To improve the nitrogen removal eficiency, an anoxic and aerobic (AO) process is proposed in a secondary municipal wastewater treatment plant. Please draw a schematic diagram and describe all the process, role of microorganisms, and mechanisms for nitrogen removal.(10分)