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.

What is the optimal pH range for Pac coagulation?

The optimal pH range for PAC coagulation performance was 7.5 to 8.0. The coagulation process in conventional water treatment could be enhanced and the ensuing water pH decline reduced appreciably by applying the right dosage of polyaluminium chloride and appropriate process conditions of pH, fluid mixing speed matrix and residence time.

How can pre-polymerized coagulant be produced?

Several efforts have been made to produce the pre-polymerized coagulant with properties, similar to the properties of a commercially available PAC solution, using appropriate, commonly found laboratory equipment and without the application of extreme conditions (in terms of temperature or pressure).

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 is polyaluminium chloride synthesized?

Synthesis of polyaluminium chloride 2.1.1. Preparation of solutions (min 37%). Granular Al was introduced slowly and in small portions to continuous magnetic stirring. After the introduction of the fi rst heating was not needed. without heating. A portion of NaOH solution (10 –50%) was placed in a 500 mL flask on a magnetic stirrer.

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.