Cheap and Efficient Coagulants

What are other cheap and efficient coagulants apart from Aluminium Sulphates? We are investigating some of the worse unsafe water sources (muddy water from rivers, ponds and wells) being used by some communities in some parts of Nigeria and how they treat the water before use. We discovered that some of them use Alum (Aluminum Sulphate) as the cheapest available solution to clarify the water and use bleach to disinfect. Our laboratory analysis of most of the "treated water" showed the presence of Aluminium at higher values than Nigeria Industrial Standard (NIS) and WHO guidelines for drinking water. Is there a cheaper chemical solution that coagulates and clarifies such water?