Pulsafeeder Simplifies Chloramination

Chlorination has become a standard in the control and purification of our municipalities’ water supply. Chlorination is typically controlled by either “flow pacing” or residual Chlorine (Cl) measurement at the effluent of the treatment facility. Approximate chlorination ratios average 1 pound of Chlorine gas/1 gallon 12.5% commercial Sodium Hypochlorite (NaOCl) or 15 gallons of 0.8% NaOCl (as typically provided via onsite generation) per 125,000 gallons of water for a desired 1ppm Chlorine residual.

Pre-Chlorination, or the injection of Chlorine prior to filtration, increases the efficiency of the filtration process but also facilitates the undesirable production of Trihalomethanes (TTHM). TTHM, a product of Chlorination and the naturally occurring organics found in surface water, is believed to cause serious adverse health effects and must be precluded.

Chloramination is the process of dosing a ratio of Chlorine to Ammonia that allows us to prevent the formation of TTHM. When using concentrations of 12.5% NaOCl and 19.0% NH3 (aq) at a 5:1 ratio we arrive at a dosed rate of 8 gallons NaOCl to 1 gallon NH3 (aq). For a 5 mgd plant, we might dose 40 gpd of 12.5% NaOCl with 8 gpd of NH3 (aq). This is readily accomplished with a dual headed or “Duplex” pump configuration and then “flow paced” to provide the requisite residual chlorine.

Reservoir Management brings about its own set of challenges with regard to Chloramination. Seasonal swings in naturally occurring organic concentrations preclude the conventional ratio of 5:1 NaOCL: NH3. These existing nitrate concentrations, accompanied by the dosing of additional ammonia, result in a food source for and subsequent production of the very products we wish to eliminate. Too little ammonia injection results in the production of dichloramine (NH2Cl) and nitrogen trichloride (NCl3) that result in an undesirable taste and smell in our drinking water. The innovative advances at Pulsafeeder allow us yet another opportunity to assist in the water management process. Through the application of a Duplex Pulsar with the accompaniment of the technologically advanced, Digital Logic Controller (DLC/M) we are able to meet the demands of the application. A duplex Pulsar is provided with the capacity of each head sized to meet the requisite residual Cl and the conventional ratio of 5:1 NaOCl: NH3 (aq). Residual analyzers are installed to provide the increase/decrease in flow (speed adjustment) while maintaining the 5:1 ratio. An additional signal, generated by spectrometer measurement of produced monochloramine, adjusts the volume (stroke) of the ammonia pump. As Cl in equals monochloramine production, the assumption is that there are no produced dichloramine or nitrogen trichlorides.

At Pulsafeeder we look forward to sharing in your endeavor towards the pursuit and management of our most valued resource “Clean Water”. Please contact us to discuss your local needs.