In recent years, the construction of sewage treatment plants has been heating up in order to treat urban sewage. The large-scale implementation of sewage treatment plants can indeed reduce the COD reduction of urban domestic sewage in a short period of time. However, some local urban sewage has passed fish ponds and natural The ecological purification of wetlands can also greatly reduce the COD concentration. From this:. ['A single centralized governance model does not conform to the laws of environmental protection itself.', 'Pollution is at the cost of energy and money.', 'Measures to reduce emissions should be adapted to local conditions, combining multiple methods.', 'For the purpose of pollution control, energy conservation and emission reduction cannot be combined.']