Montana DEQ - Circular DEQ 2 - Design Standards for ... - Force Flow

Supplemental Treatment Process Chapter 110111.3 Feed Systems111.31 LocationAll liquid chemical mixing and feed installations should be installed oncorrosion resistant pedestals and elevated above the highest liquid levelanticipated during emergency conditions. The chemical feed equipmentmust be designed to meet the maximum dosage requirements for the designconditions. Lime feed equipment should be located so as to minimize thelength of slurry conduits. All slurry conduits must be accessible forcleaning.111.32 Liquid Chemical Feed SystemLiquid chemical feed pumps should be of the positive displacement typewith variable feed rate. Pumps must be selected to feed the full range ofchemical quantities required for the phosphorus mass loading conditionsanticipated with the largest unit out of service. Consideration should begiven to systems including pumps and piping that will feed either ferric oraluminum compounds to provide flexibility. Refer to Section 111.51.Screens and valves must be provided on the chemical feed pump suctionlines.An air break or anti-siphon device must be provided where the chemicalsolution stream discharges to the transport water stream to prevent aninduction effect resulting in overfeed.Consideration must be given to providing pacing equipment to optimizechemical feed rates.111.33 Dry Chemical Feed SystemEach dry chemical feeder must be equipped with a dissolver that is capableof providing a minimum 5-minute retention at the maximum feed rate.Polyelectrolyte feed installations should be equipped with two solutionvessels and transfer piping for solution make-up and daily operation.Make-up tanks must be provided with an educator funnel or otherappropriate arrangement for wetting the polymer during the preparation ofthe stock feed solution. Adequate mixing should be provided by a largediameter,low-speed mixer.155