Abstract: Electrochemical improvement of soft soil is an effective method for the soft soil strengthening. This paper presents the case history of soft soil treated by electro-chemical improvement project in Jinwan District of Zhuhai City. The water quality of the wastewater was tested and analyzed during the strengthening process. Affected by the properties of the electro-chemical improvement, the grouting solution and the geographical location of the project, the wastewater of this project has relatively high content of aluminum, sodium, chloride and total dissolved solids, and is rich in organic matter. It is a strong alkali solution, after the pH treatment, it can be discharged as the urban sewage water meets the discharging standards and will not affect the ecological environment. The Ca²⁺, Mg²⁺, Fe³⁺ ions and other heavy metal cations in soils can produce oxide/hydroxide precipitation during the electrochemical improvement, which promotes the consolidation of the soft soil and therefore improves the soil strength. The Al³⁺ in the soil will gradually be replaced with hydrogen ions produced by the electrolysis and form hydroxide precipitation, but at high pH value, part of the Al³⁺ will gradually dissolve and discharge from the cathode with the wastewater. It is suggested that the strong alkalinity and rich organic matter of the wastewater should be used for recycling, energy saving and emission reduction, so as to achieve the sustainable development of environmental protection.

Key words: Soft Soils, Electro-Chemical Soil Improvement, Wastewater, Water Quality Analysis