A dry polymer eductor is used when powder must be combined with water to create the perfect mix of chemical concentrations. Dispersers can effectively wet 2.27 kg (5 lb) of powder for every 37.8 to 56.7 L (10 to 15 gal.) of water supplied to the unit, resulting in a 4 to 6% concentration of flocculant in the water. This mixture must then be mixed thoroughly with additional water until the powder is dissolved completely and the desired solution concentration obtained. Water supply pressures from 20 to 100 psig (1.37 to 6.89 barg) can be used.
The dry polymer eductor is a ‘small job’ device and operates in a similar manner to a ring jet; the nozzle having the same basic characteristics.
What are polymers?
A polymer is a very large organic molecule; it is a chain of monomer subunits. Some of the monomer molecules have positive or negative charges.
• Polymer chains vary in length from thousands to millions of monomer units.
• If each monomer molecule was the size of a pearl, the chain length of most polymers would be 400 to 8,000 feet long!
• In wastewater treatment processes, polymers are used to coagulate suspended solids and produce large curds of solid materials (floc).
Why add polymers?
- Primary clarification improves solids settling and reduces biochemical oxygen demand (BOD) load on system. Biochemical oxygen demand (BOD) is a measure of how much oxygen is required to biologically decompose organic matter in the water. Total suspended solids (TSS) is the total amount of suspended materials in the water. Both measure the strength of wastewater discharges.
- Secondary clarification improves solids compaction SVI (Sludge Volume Index), removes suspended solids, and increases hydraulic throughput capacity.
Typical Applications Include:
Once considered for use primarily in wastewater treatment applications, a Dry Polymer Eductor could be used for any dry powder or granular product.
Flocculants, or flocculating agents (also known as flocking agents), are chemicals that promote flocculation by causing colloids and other suspended particles in liquids to aggregate, forming a floc. Flocculants are used in water treatment processes to improve the sedimentation or filterability of small particles. For example, a flocculant may be used in swimming pool or drinking water filtration to aid removal of microscopic particles which would otherwise cause the water to be turbid (cloudy) and which would be difficult or impossible to remove by filtration alone.
Many flocculants are multivalent cations such as aluminium, iron, calcium or magnesium. These positively charged molecules interact with negatively charged particles and molecules to reduce the barriers to aggregation. In addition, many of these chemicals, under appropriate pH and other conditions such as temperature and salinity, react with water to form insoluble hydroxides which, upon precipitating, link together to form long chains or meshes, physically trapping small particles into the larger floc.
Long-chain polymer flocculants, such as modified polyacrylamides, are manufactured and sold by the flocculant producing business. These can be supplied in dry or liquid form for use in the flocculation process. The most common liquid polyacrylamide is supplied as an emulsion with 10-40% actives and the rest is a non-aqueous carrier fluid, surfactants and latex. This form allows easy handling of viscous polymers at high concentrations. These emulsion polymers require “activation” – inversion of the emulsion so that the polymers molecules form an aqueous solution.
The table below shows the flow rate of water in gpm at various supply pressures with standard orifice settings.
Dry Polymer Eductor Water Flow Rate
|Pipe Size||Water Supply Pressure @ Inlet (PSI)|
|20 (PSI)||40 (PSI)||60 (PSI)||80 (PSI)||100 (PSI)|
|3/4″||8 GPM||12 GPM||15 GPM||17 GPM||20 GPM|
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