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By Vinay Kumar Dhar

Freshwater share is just merely 3% of total water available on our planet earth. With the rising population, the demand for freshwater is also rising. Due to this, we have to conserve water as well as reuse the freshwater by treating it through wastewater treatment plants. When the wastewater reaches the treatment plant, it carries a lot of impurities and foreign material like phosphates which make the water unusable for drinking & cleaning. In such scenarios, we use chemical dosing to mitigate these challenges.

In chemical dosing, we treat the wastewater with accurate chemical dosing agents like pH neutralizers, anti-foaming agents, coagulants, and flocculants to remove high levels of chemicals present in it.

Ideally, wastewater effluent flowing into the sewer should have a pH value of 7 i.e. it should not be too acidic or too basic. This will help to prevent undesirable chemical reactions when effluent mixes with wastewater. pH neutralization is very important. If it goes directly into the river, it may harm marine life & disturb the ecosystem. Most Industrial units use various types of basic & acidic chemicals which are flushed into the drain. It is difficult to maintain the pH value. Therefore, to neutralize it, industries conduct pH adjustment by controlling the dosing of sodium hydroxide (NaOH) to ensure the pH value of effluent outflow to the sewer is under state guidelines.

Foaming is the formation of air bubbles within the wastewater. It causes increased mechanical wear on pumps and blocks screens& filters causing blockage of drainage, thus reducing the efficiency of wastewater treatment. The foam also gets deposited on storage tanks and eventually leads to an increase in maintenance costs. To nullify the effect of foaming, controlled dosing of anti-foaming chemical agents with low viscosity is used. These anti-foaming agents cause the air bubbles to rupture and break down the foam formation. Choosing the right antifoaming agents & correct dosing will greatly reduce the maintenance costs and chemical consumption.

Lastly, the combination of flocculants & coagulants is used in optimal combination to remove the suspended solids and clarify water. Positively charged coagulants have a low molecular weight which neutralizes the charge of suspended solids. Coagulants also offset the repulsive effect that stops the negatively charged particles to aggregate. After this, Flocculants with high molecular weights are used to bind together these positively charged neutralized particles into large aggregations (also known as flocs), to increase the water clarification.

Importance of Controlled Dosing
Choosing the right chemical for dosing depends upon the effluent compositions & design of the wastewater treatment plant. More importantly, the operator should know where to add chemicals in the wastewater treatment process and in what quantity, and at what time. As overdosing of chemicals will increase wastewater treatment costs and the presence of chemical agents in the outflow to the sewer, this will surpass the regulatory limits. Similarly, underdosing will reduce the efficiency of wastewater treatment.

Selection of Pumping Technology
After carefully deciding the right amount of chemical dosing, the system operators should choose the accurate pumping system to ensure minimalistic deviation (+/- 1%) inflow like the Roto RJ Series Dosing Pump. After ensuring flow, the components of the pumping system should be able to withstand the dosing chemicals. Most importantly, selecting the right service partner will reduce the overall maintenance costs & greatly minimize downtime.

About the Author
Vinay Kumar Dhar is the Vice President of Roto Pumps Ltd.

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