Decision Support System for Manganese Forecasting and Proactive Treatment in Subtropical Water Reservoirs

Abstract

Water utilities around the world have adopted raw water treatment procedures in order to deliver to consumers the water that meets the drinking water quality standards set by national or international regulations. The raw water not only must be purified from harmful constituents that can cause waterborne diseases, but aesthetical standards must also be maintained to avoid customer complaints, which would reduce the confidence of the community towards the drinking water supplier. Potable water having a high concentration of manganese is one of the most widespread aesthetic issues reported by customers. Manganese in reservoirs is a trace metal typically present in small amounts. However, concentrations as small as 0.1 mg/L can cause water discoloration, staining, and even metallic taste. Many international drinking water standards set the upper acceptance limit to 0.05 mg/L for water delivered to the consumers; yet many water utilities such as Seqwater, in South East Queensland, Australia, usually target concentrations of manganese dissolved in the treated water lower than 0.02 mg/L, in order to avoid potential adverse customer reactions to discoloured water. The manganese removal procedure usually is limited to pre-filter chlorination, but for very high manganese levels, the addition of potassium permanganate is performed, because of the faster oxidation reaction.