How will leachate typically re-circulate in a leachate recirculation system; specifically how is it reintroduced into the landfill?

Leachate circulation was often done using spray irrigation or using actual water trucks or tank trucks. Unfortunately, there can be too much evaporation loss, and a considerable problem with odors. It is more common now to reintroduce the leachate into the landfill through infiltration trenches or blankets.  The trenches can be nothing more than ditches cut into the waste a few feet with some rock back fill and perforated pipe, you can add a geo textile fabric around the rocks to prevent it from moving out into the waste mass. From there it's covered back over and the leachate can be pumped through this, essentially, French drain system that allows the leachate to dissipate out into the landfill.  The advantage of this over irrigation is obvious: you won’t have evaporation or transpiration loss or odor issues. But, you can have problems because you can't get the leachate to move out very far into the waste mass. So, now at sites that are using recirculation it’s not uncommon to build what are called leachate blankets. Before the cap is placed on the landfill, an interim layer (that can be something like crushed tire chips, crushed glass or possibly rock) is laid down. This “blanket” should be about a .5-meter or 1.5-foot thick, then the final cover is put over the top of that and pipes will infiltrate into it. As the liquid goes through the pipes it can spread out quickly through the blanket and then precipitate downward through the entire landfill.