Abstract: In this paper, the eutrophication secondary disasters in urban malodorousback river were reviewed from the forming and treatment of “malodorousback”, and the disaster forms and control and preventive measures. The results indicated that with the implementation of many treatment projects, technologies and measures in pollution control and remediation, pollution load of urban malodorousback river was greatly reduced, water quality had been much improved, and the “malodorousback” disappeared gradually. All these resulted to the nutrient that can be utilized by plant was at high level, and the damaged ecosystem of urban river was restored and constructed. Once those environmental factors were very suitable, the major outbreak of eutrophication secondary disasters (e.g. algal bloom, Lemna minor L, Eichhorniacrassipes.) could be unavoidable. For its part, the control and preventive measures of eutrophication secondary disasters must be based on the treatment and remediation of “malodorousback”. In addition, we realized that the outbreak of eutrophication secondary disasters would be an unavoidable stage of the treatment and remediation of “malodorousback”, and the current focus on pollution control and remediation of urban river should be changed from the severe pollution treatment (e.g. “malodorousback”) to the nutrient (Nitrogen, phosphorus, etc.) control.

Key words: urban malodorous, back river, eutrophication, algal bloom, formation mechanism, control and preventive measures