Water Treatment > Quality Water Solutions > Coagulation Control > Overview

Instruments that track coagulant performance are the eyes and ears of efforts to control clarification. They help define efficiency, signal excursions, and complement basic laboratory tests and routine analyses. Typical methods use pH, Zeta potential, streaming current instrumentation, as well as pilot filters and continuous coagulant residual analyzers.

Source water contaminants are either particulates, colloids or dissolved materials. In addition to improving the appearance, taste and odor of water, coagulation is a barrier to waterborne bacterial, viral and protozoan diseases. Coagulation can also help mitigate disinfection by-products (DBP) because many of their precursors are colloidal.

Particulates and colloids in water are associated with a "cloud" of negatively charged ions. Coagulants supply positive ions that neutralize this cloud so solids agglomerate or flocculate into particles large enough to settle out or be filtered. As the floc matrix grows, it also acts as a net that sweeps fine materials from the water by entrapment.

Simple laboratory tests provide discrete measurement of macro coagulant demand and performance. Instrumentation can fine tune this by monitoring the process on the micro level, i.e., at the interface between coagulant metal ions and the particulate or colloid at which it is aimed.

Good coagulant control should combine low cost methods that include routine laboratory tests and interpretation of operational data with instrumentation. By understanding the many general indicators that point to changing coagulant demand, a plant can respond appropriately long before treatment breaks down. These indicators go beyond turbidity and color to include odor, chlorine demand, microbial concentration, UV absorption and total organic carbon.

The data shed light on results from instruments like streaming current detectors that continuously monitor the microenvironment. Such instruments deepen and sharpen the level of response beyond that possible by operator observation alone. The two together, broad indicators and sophisticated instrumentation, assist operators in their duties and allow plants to make the best water at an acceptable cost.