Does polyaluminum chloride coagulate with hydrolyzed coagulants?

Coagulation with hydrolyzing coagulants has been studied thoroughly, but the coagulation behavior of pre-hydrolyzed coagulants such as polyaluminum chloride (PACl), especially the coagulation mechanisms at various coagulant dosages and pH values of raw water, has not been systemically investigated and not been well understood , .

Is polyaluminium chloride better than polyelectrolyte – alum-based coagulation?

At the Barekese Water Treatment Plant in Ghana, an alternative, the polyelectrolyte – polyaluminium chloride (PAC) is also used in coagulation but limited information is available on the operating conditions required to achieve better performance than alum-based coagulation.

Why are aluminium based polymers used in water treatment?

These shortfalls in the use of alum have led to the synthesis of improved, aluminium-based polymers, which have been used extensively, over the few last decades, for treating water due to their high efficiency at lower dosages, and wider pH and temperature application ranges (Sahu & Chaudhari 2013).

How should coagulation pH be matched to raw water alkalinity?

PACl basicity should be matched to raw water alkalinity, so that coagulation pH is as close as possible to the pH of minimum solubility of the coagulant. The solids separation process used for treatment was also found to be important for coagulant selection.

What is the difference between Alum and PACL coagulation?

The restabilization zone of PACl coagulation disappears at a higher final pH value than that of alum coagulation. Moreover, the charge neutralization and sweep coagulation zones of PACl are broader in the ranges of coagulant dosage (as Al) and pH value than those of alum.

What are the disadvantages of alum coagulant?

Water Practice and Technology 1 October 2021; 16 (4): 1215–1223. doi: Alum, the predominant coagulant in conventional drinking water treatment schemes, has various disadvantages including the production of large volumes of sludge, lowering water pH (requiring pH adjustment using lime), limited coagulation pH range of 6.5 to 8.0, etc.