Study on phosphorus removal using a coagulation system

This study has determined the conditions for operation of a phosphorus-removal system using coagulation–filtration to gain high efficiency and has confirmed its practicability. Sand of 0.6 mm in diameter, anthracite of 1.2 mm in diameter and a mixture of both were tested as filter media. The dual filter bed was proved to be superior in terms of pressure drop and breakthrough. This system was operated continuously for over 20 h. A blocked filter bed can be recovered by backwashing. Over 80% phosphorus removal efficiency is achieved at an LV of under 5.0 m h−l, when the PAC dose is controlled so that the Al/P mole ratio would be 3.0 for the first period, and then subsequently around 2.0. Flocs caught in the filter further adsorb the soluble phosphorus in the wastewater. Thus, the chemical requirement can be reduced compared to the chemical precipitation method.