For ARD filters, reactive barriers are often the methods of choice. Some problems are recognised though; iron precipitation cause hydraulic changes and inhibition of neutralising phases. Instead of filter/barrier installation alkalinity is suggested to be added in an aqueous phase (leach beds). Addition of a highly alkaline solution to different ARD results in a rapid, almost instant neutralisation, precipitation of metals (Fe, Al) as well as almost quantitative coprecipitation and sorption of trace metals at near neutral pH. Generation of alkalinity on-site, added to ARD as an aqueous phase, would be a fast and simple ARD treatment method.