Chemical Injection: Just the Right Amount
Chemical injection systems range from simple self-sufficient/self monitoring chemical dosing systems with small tanks, to multichemical injection systems, controlled by process feedback via programmable logic controllers (PLC's). Regardless of the application, Reverse Osmosis-based, or RO-centric systems are usually designed to operate with minimum possible use of pre and post treatment chemicals. Reverse osmosis systems are inherantly chemical-lean and only use what is necessary to make minor adjustments to the balance and nature of constituents in the feed and product water. A water treatment system that relies on the extremely efficient use of chemicals, reduces operating costs, environmental impact and, in many cases, reduces or eliminates the need for waste disposal.
Chemical Dosing Systems are often used to:
q Lower Operating Cost
q Prevent Reverse Osmosis (RO) Membrane Scaling (Scale Inhibitors)
q Chlorinate, or Dechlorinate Process Water depending on its Position in the Water Treatment Train (Biocides/Biocide Removal)
q Inject RO Membrane Cleaning Chemicals into the Feedwater Stream of an RO Cleaning Station
Chemical dosing pumps may operate as stand-alone chemical injection controllers, or may interface with system-based logic controllers (PLC's).
Depending on the position in the Water Treatment Train, and the constituents in a given process water, Chemical Dosing may provide a cost-effective solution to pretreatment, treatment, or post treatment. Antiscalants and Antifoulants are common chemical options for pre-conditioning the feedwater of Reverse Osmosis systems, keeping contaminants from precipitating onto RO Membranes so that they pass safely into the Waste Water (Concentrate) Stream.
Chemical dosing storage tanks come iin a variety of sizes to accomodate operation conditions and water chemistry requirements. Many of these tanks are designed to accept chemical pumps and provide a packaged solution for managing chemical feed into incoming feedwater, or outflowing product water.
Advantages of Chemical Dosing Include:
q Low Capital Cost Pre or Post Treatment of Process Water
q Small Space Requirements
q Low Operating Cost
q Extremely Important Component of Pretreatment Strategy for RO
q The Larger the Water Demand from and RO, the more likely that Chemical Dosing will be the most Cost-effective Choice
Pretreatment Chemicals:
q Antiscalants
q Antifoulants
q Biocides
q Coagulants/Flocculants
q Acid
q Chlorine
q Dechlorination
pH Adjusting Systems:
pH Adjustment Systems are often used to:
q Raise, or Neutralize the pH after a Reverse Osmosis (RO) System
Reverse Osmosis (RO) Systems can lower the pH of Process Water by 1 to 2 points, creating slightly acidic water. Unaltered, this slightly acidic water can pose a risk to certain types of downstream piping and equipment, or be unsuitable for particular applications. Neutralizing pH is commonly accomplished by passing the Process Water through a Calcite Filter, or by using a Chemical Dosing System for Caustic Dosing.
pH adjusting systems may be in the form of a liquid injectection system or a pass-through media filter.
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