Underground Water Contamination by Landfills

In the middle of last century, the disposal of solid waste in sanitary landfills had no form of legislation to regulate the way in which it occurred. At the beginning of the twenty-first century, most first world countries implemented legal measures and these landfills began to be sealed. However, most of the damage was already done, particularly at the level of soil and groundwater contamination. In this partucularly situation, the main problems are the registration of alkaline pH level, high conductivity, high concentration of chlorides, sulfates, bicarbonates and aluminum. How to fix this situation or reverse this trend??