acility for chemicals for a small treatment facility is shown on Fig. 6-10 识g.6-10 plant. The chemical storage tanks are containment structure in and (b) chemicol storage Dry Chemical-Feed Systems A dry chemical-feed system typically consists of a storage hopper, dry chemical feeder, a dissolving tank and a pumped or gravity distribution system Fig 6-11 Schematic of opical dry Chemical-feed system Bin gate hopper for Anemative supplies depending on sorage Drain Control Soleno D Gravity to applicaton Pressure- The units are sized according to the volume of wastewater, treatment rate, and optimum form an arch such as lime are equipped with positive agitators and a dust-collection system. Dry chemical feeders are of either the volumetric or the gravimetric type. In the volumetric type the volume of the dry chemical fed is measured whereas in the gravimetric type the weight of chemical fed is measured. Of the dry chemical-feed systems, the loss in weight feed system is used most commonly in wastewater-treatment operations. With a dry feed system, the dissolving operation is critical. The capacity of the dissolving tank is based on the detention time, which is directly related to the wettability or rate of solution of the chemical. When the water supply is controlled for the purpose of forming a constant-strength solution, mechanical mixers should be used. Depending on the flow pattern within the mixing tank, it may be necessary to add baffles for effective mixing. In smaller mixing tanks. the mixer can be set at an angle to avoid the use of baffles Solutions or slurries are often stored after dissolving and discharged to the application point at metered rates by chemical-feed pumps 6-186-18 facility for chemicals for a small treatment facility is shown on Fig. 6-10. Dry Chemical-Feed Systems A dry chemical-feed system typically consists of a storage hopper, dry chemical feeder, a dissolving tank, and a pumped or gravity distribution system. The units are sized according to the volume of wastewater, treatment rate, and optimum length of time for chemical feeding and dissolving. Hoppers used with powdered chemicals that are compressible and can form an arch such as lime are equipped with positive agitators and a dust-collection system. Dry chemical feeders are of either the volumetric or the gravimetric type. In the volumetric type the volume of the dry chemical fed is measured whereas in the gravimetric type the weight of chemical fed is measured. Of the dry chemical-feed systems, the loss in weight feed system is used most commonly in wastewater-treatment operations. With a dry feed system, the dissolving operation is critical. The capacity of the dissolving tank is based on the detention time, which is directly related to the wettability or rate of solution of the chemical. When the water supply is controlled for the purpose of forming a constant-strength solution, mechanical mixers should be used. Depending on the flow pattern within the mixing tank, it may be necessary to add baffles for effective mixing. In smaller mixing tanks, the mixer can be set at an angle to avoid the use of baffles. Solutions or slurries are often stored after dissolving and discharged to the application point at metered rates by chemical-feed pumps. Fig. 6-10 Fig. 6-11 Schematic of typical dry Chemical-feed system