Metal Coagulant Research Paper

3 Coagulation

3.1 Definition

Coagulation is a process used for neutralization of charges and forming a viscous mass to bridge particles forms a mass large enough to settle in the filter.

Coagulation is important process in several wastewater treatment operations. A common ex-ample is the removal of chemical phosphorus and other is in the overloaded wastewater treatment plants, leading to the practice of chemically enhancing primary treatment (CEPT) to decrease suspended solids and organic masses from primary clarifiers.

3.2 The Coagulants

The frequently used metal coagulants lies into two general categories: based on aluminum and iron. The aluminum coagulants includes aluminum chloride, aluminum sulfate and sodium aluminates. The iron coagulants

The most extensively used metal coagulant is perhaps the aluminium sulfate (“alum”). Other Al coagulants are aluminum chloride (AlCl3.6H2O) and sodium aluminate (NaAlO2).

The application of simple metal coagulants (conventional) is common because of their rel-atively low cost and the simpler application route.

3.5.2 Pre-polymerized coagulant

Their properties were intensively examined and have proved to be more efficient in lower dosages, in wider temperature, pH and colloids concentration ranges, than the con-ventional simpler ones, leading to cost and operative more effective treatment.

This aluminium anionic form is claimed to be the precursor for the polymeric Al13 creation. Al13(AlO4Al12(OH)24(H2O)126+,7+) with ε-Keggin structure is one of many possible PACl polymeric compounds, like dimmers (e.g. Al2(OH)24+), trimers (e.g. Al3(OH)45+) among several others, even larger than Al13 i.e. with more than 13 aluminium atoms (e.g. Al30O8(OH)56(H2O)2418+), which continuously transform from one form to another.

The production of pre-polymerized coagulants includes the partial neutralization of an Al so-lution with a base