Coagulant dosing in a Water Treatment Plant is a highly complex stage, as too much can increase operating costs and lead to the accumulation of chemical substances that are harmful to health in the water, while too little can prevent Turbidity from being eliminated, saturating the filters and damaging the quality of the final water. It is therefore essential that this control is carried out efficiently.
It is common for companies in general to aim to reduce costs, but it is necessary to look at the process holistically, considering all the variables so that there are no undesired effects. Controlling coagulant dosage through Turbidity is an example of a cost-cutting attempt that which can harm the process.
Water coagulant
Water treatment basically consists of 9 stages:
- Water collection
- Coagulation
- Flocculation
- Decanting
- Filtration
- Disinfection
- Fluoridation
- Final control
- Distribution
The coagulation stage consists of dosing a chemical reagent, usually aluminum sulfate, with a positive charge that will interact with the negative charges of the particulate materials (colloids, clay, organic matter, etc.), forming flocs with a larger mass, making decantation possible. This dosage of chemical product must be very well controlled so that the suspended solids are correctly flocculated and decanted. If this flocculation is not effective, the water will arrive at the filtration stage with a high quantity of solids, generating a greater need to backwash the filters and reducing their useful life.
On the other hand, excessive dosage of chemical products can make the water harmful to the health of the population due to the common use of Aluminum in the composition, in both cases there is financial damage involved.
Some water treatment plants use a Turbidity analyzer to control the dosage of coagulant, but this is not ideal, since this control is done by means of a correlation and mathematical approximation, greatly reducing the accuracy and reliability of the measurement. Furthermore, we know that Turbidity is affected by factors such as the shape and size of the particles, which can lead to a misinterpretation of the amount of coagulant required.
Digimed, with over 45 years experience in analytical instrumentation for water treatment, has observed that the ideal is to use a specific analyzer for monitoring loads (Coagulant monitor - AI-ZT-HP). This type of equipment directly evaluates the interaction between the loads of the chemical product and the particles in suspension, informing us when it is really necessary to increase or decrease the dosage.
The Turbidity analyzer should be used at the water collection, output filter, final monitoring and distribution, ensuring complete compliance with drinking water standards.
Digimed supplies analyzers for both coagulant and Turbidity control. Browse our website or contact our application engineering team.
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