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Squeezing the Most Out of Your Decision: A Suppliers Unbiased Approach for Selection of Dewatering Equipment
Shaun Hurst, Denis Piche
ANDRITZ Separation, United States of America;
Over 7,000,000 dry tons of biosolids have to be treated every year in the United States. Selection of the optimum dewatering equipment is important for every facility. The type of equipment can be dependent upon multiple factors including: plant size, disposal of the dewatered biosolids, money (capital costs / operating costs), area or footprint available, and others. This presentation will provide a guide for consultant engineers, owners and contractors for evaluating biosolids dewatering options.
The centrifuge, belt filter press and screw press operation will be explained. Next the pros and cons of each equipment will be presented including the major points of selection; dryness, polymer consumption, capture rate, footprint, throughput capacity etc. Then the dewatering parameters of different sludge types such as anaerobically digested sludge and waste activated sludge will also be presented in regards to each dewatering equipment. These numbers will be based upon numerous laboratory, pilot scale and installation performance results.
11:15am - 12:00pm
Polymer 101: Chemistry, Handling, Dilution Water, and Optimization
UGSI Solutions, Inc., United States of America;
Coagulation or flocculation is an essential stage in many solid-liquid separation processes of municipal and industrial wastewater treatment plants. The aggregation of particles into larger and easily removable forms is necessary for efficient separation by sedimentation, filtration, or dewatering.
History of coagulant and flocculant in water and wastewater treatment is briefly illustrated. Since the chemistry of coagulant and flocculant is very different, the mechanism of coagulation and flocculation is also fundamentally different. Three types of polymers are discussed in regards to physical form, molecular weight, charge density, and size distribution. Proper way of handling and storage of dry or emulsion polymer is reviewed as well as the shelf-life of neat polymer and diluted polymer solution.
Quality of dilution water has tremendous impact on the efficiency of polymer solution. Hardness representing a major portion of the ionic strength of dilution water plays an important role in polymer activation. Considering the increasing trend of utilizing reclaimed water for polymer mixing at wastewater treatment plants, chlorine level of dilution water is to be maintained below 3 mg/L. When reclaimed water is used, aging of polymer solution must be carefully evaluated. Chlorine, suspended solids, and dissolved ions included in reclaimed water are reacting with polymer and resulting in degraded polymer solution during aging.
Preparing efficient polymer solution is one of several key components for successful solid-liquid separation. Due to its unique property of polymer, polymer make-down requires well established scientific understanding. It includes the concept of two-stage mixing; very high energy mixing to prevent fisheye formation at initial mixing stage, followed by low energy mixing to minimize damaging polymer chains. Two-step dilution and adequate residence time are also required to achieve fully extended molecular structure of polymer in solution. Various publications and product brochures by polymer manufacturers are also reviewed and presented.