Recycle Alum Sludge

http://search.yahoo.com/search;_ylt=ArM0jMQ9GCpeGYbYegqTiM.bvZx4?p=recycling+coagulant+from+aluminum+sludge+&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701

thank you. but actually today ive done some research and browsing. so eventually i found more questions:

1. mostly people use acidification for recycling than alkaline treatment. but acidification will produce a liquid coagulant as Al3+ which is has a by-product as acid sludge. isnt it same as producing more problem because of it's acid nature?

2. instead of producing an acid sludge, why dont people choose alkaline treatment which has more persentage recovery aluminium and doesnt produce acid sludge as its by-product?

sry it's so confusing for me.

Sorry I don't have any idea about that.