With the accelerating process of urbanization and industrialization, the pressure on urban river ecosystem is increasing, and the problem of river wastewater pollution is becoming increasingly prominent. Scholars at home and abroad have done a lot of research on it. The common causes of river wastewater pollution are as follows:
- Domestic sewage is directly discharged into the river without treatment or treatment not up to standard.
- Industrial sewage is directly discharged to the river.
- Pollutants brought by rainfall: in the initial stage of rainfall, a large number of pollutants on the surface flow into the rainwater pipe network with the surface runoff, and then carry the pollutants deposited in the rainwater pipe network, and finally discharge into the water body to form pollution to the river.
River pollution is mainly caused by a large number of pollutants entering the water body in a short time. Source control and sewage interception is the first and most critical step of river treatment. However, because municipal sewage interception is a difficult and time-consuming project, and it is difficult to implement the sewage interception plan in many areas, especially in the junction of old urban areas and suburbs, it is difficult to realize the comprehensive sewage interception of lakes in a short time.
Therefore, in order to realize the treatment of river pollution, it is necessary to treat the sewage outlet that has not been intercepted, eliminate or reduce the impact of the sewage discharged from the sewage outlet on the river water quality, and ensure the effective implementation of other follow-up remediation methods.
Therefore, we have begun to focus on the sewage treatment of urban river outfall, and set up wedge wire screen sewage treatment equipment on both sides of the river. However, the current equipment treatment methods have the following disadvantages: the equipment process is not simple, the investment is large, the buried equipment or the equipment set on the shore covers a large area and the operation cost is high.
At present, the treatment technology of sewage outlet in river regulation also includes separating the sewage discharged from the sewage outlet from the river water with impermeable enclosure around the sewage outlet, planting emergent plants and phytoplankton in the enclosure, and hanging microbial filler. This measure has the following disadvantages:
- The enclosure can not well separate the sewage from the river water. The sewage will still flow into the river and pollute the water body.
- The sewage discharged from the sewage outlet will inhibit the growth of plants and even cause plant death, so plants can not play the role of purifying sewage.
- There may be mixed flow of rain and sewage at the sewage outlet, so the sewage discharge is large during the rainfall period, causing serious pollution to the river.