What happens to alkalinity and pH when coagulants consume alkalinity?

When coagulants are added to water, they often react with alkalinity in the water, which primarily consists of bicarbonate and carbonate ions. This reaction typically involves the neutralization of these alkalinity compounds, leading to a decrease in the concentration of these ions, and consequently, a decrease in alkalinity.

As coagulants consume alkalinity, the balance of hydrogen ions in the water shifts, which tends to lead to a reduction in pH. A lower pH indicates more acidity in the water. This chain of events—where coagulants react with alkalinity, leading to a decrease in its levels and subsequently causing pH to drop—accurately describes the relationship between alkalinity and pH during the coagulation process.

Understanding this process is essential in water treatment because maintaining the optimal pH and alkalinity levels is crucial for effective coagulation and overall water quality management.