High-pH magnesium coagulation-flocculation in wastewater treatment

Chemically enhanced wastewater treatment is attracting substantial interest, especially for wastewaters that are not amenable to treatment by conventional biological treatment strategies. Among the currently employed chemical unit processes in wastewater treatment, coagulation-flocculation has received considerable attention for yielding high pollutant removal efficiency. Over the past years, several authors have investigated the role of magnesium ions as a potential coagulant for the chemical clarification of wastewater. This paper presents a comprehensive review of high-pH-magnesium coagulation-flocculation processes in wastewater treatment, describes their applicability and reveals the contribution of such treatment strategies to the chemical clarification of various wastewaters. More importantly, the paper discusses the advantages, disadvantages and process efficiency. of high-pH-magnesium coagulation-flocculation in relation to various sources of magnesium ions. The characteristics of sludges produced from lime-based chemical wastewater treatment. processes are also discussed. Finally; factors impacting the economics,of the, process are considered to estimate the costs incurred. (C) 2002 Elsevier Science Ltd. All rights reserved.