Design Guide for Community Water Systems - The Water, Sanitation ...

3. Tubing for conveying ammonia solutions shall be Type 1 PVC,polyethylene or materials recommended by the manufacturer.4. Feed lines shall be installed in a manner to prevent formation ofgas pockets and shall terminate at a point of positive pressure.5. Storage tanks and unsealed carboys or barrels shall be vented tothe outside with a vent approved by the department.5.4.5. Carbon dioxidea. Recarbonation basin design shall provide:1. A minimum detention time of twenty minutes,2. Two compartments, each with a depth of eight feet, as follows:1. A mixing compartment having a detention time of at least threeminutes; and2. A reaction compartment.b. If a carbon dioxide solution is added and rapid mixing is provided, totaldetention time and basin depths may be reduced. However, supportingdata for the proposed reductions must be included as a part of the predesignsubmittals.c. Plants generating carbon dioxide from combustion shall have open top,recarbonation tanks in order to dissipate carbon monoxide and carbondioxide. Special considerations shall be given to building ventilationwhen open recarbonation tanks are housed in a building.d. Where liquid carbon dioxide is used, adequate precautions must be takento prevent carbon dioxide from entering the plant from the feed lines orrecarbonation process. Since liquid carbon dioxide is a cryogenic and acompressed gas, the recommendations of the Compressed GasAssociation, Inc. shall be followed when specifying storage and feedingfacilities.e. Provisions shall be made for draining recarbonation basins and removingresiduals.5.4.6. Phosphates.a. Stock phosphate solution must be kept covered and disinfected by carryingapproximately ten milligrams per liter free chlorine residual.b. Phosphates can act as a nutrient for biological growth in water distributionsystems. Therefore, disinfection equipment shall be provided that issufficient to maintain disinfectant residuals throughout the distributionsystem at levels necessary to control biological growths. Heterotrophicbacteria studies should be done routinely to ensure that biological growthsare controlled through out the distribution system.5.4.7. Powdered activated carbon.a. Powdered activated carbon feed and storage facilities.1. Powdered activated carbon shall be handled as a potentiallyAug. 29, 2003Page 111