Decanter
Choosing Polymers for Centrifuges.
Introduction
For most applications, decanter centrifuges will not work without polyelectrolytes. In evaluating the life cycle costs of a centrifuge installation, the polymer cost is larger than the maintenance, power, and labor costs put together.
The success of the centrifuge depends upon the reaction between the sludge and the polymer. It is no exaggeration to say that the polymer selection determines the success of the project. There are three steps to the selection process, each more important than the others:
1. Make up small quantities of test solutions. 2. Evaluate the reaction between the solutions and a sample of the sludge. 3. Make repeatable observations.
Predicting the performance of the centrifuge from the polymer testing is thought of by the unknowing as a Zen art. It is really an assemblage of careful observations of the sludge-polymer reaction, coupled with knowledge of the treatment process, and experience at other treatment plants. Even so, jar testing cannot answer the question "Is this the best polymer?" it will narrow the selection down to a manageable number.
Life before Polymers
Before the invention of polymers, drying beds dewatered most sludge. They are still used occasionally today. While they are undeniably simple to build and fool proof to operate, they are a source of odor, take up a lot of room, are subject to weather, and require a lot of labor. So they are not such a good solution. Mechanical dewatering of the sludge is usually preferred. In the early days, this consisted of vacuum filters and pressure filters using Lime and Ferric Chloride to condition the sludge. These were large cumbersome systems with low capacity, and poor (by modern standards) performance.
The first successful centrifuges used in sewage dewatering were basket centrifuges. Sludge poured into the spinning centrifuge, and compacted under 1000 g or less. When full, the
Introduction
For most applications, decanter centrifuges will not work without polyelectrolytes. In evaluating the life cycle costs of a centrifuge installation, the polymer cost is larger than the maintenance, power, and labor costs put together.
The success of the centrifuge depends upon the reaction between the sludge and the polymer. It is no exaggeration to say that the polymer selection determines the success of the project. There are three steps to the selection process, each more important than the others:
1. Make up small quantities of test solutions. 2. Evaluate the reaction between the solutions and a sample of the sludge. 3. Make repeatable observations.
Predicting the performance of the centrifuge from the polymer testing is thought of by the unknowing as a Zen art. It is really an assemblage of careful observations of the sludge-polymer reaction, coupled with knowledge of the treatment process, and experience at other treatment plants. Even so, jar testing cannot answer the question "Is this the best polymer?" it will narrow the selection down to a manageable number.
Life before Polymers
Before the invention of polymers, drying beds dewatered most sludge. They are still used occasionally today. While they are undeniably simple to build and fool proof to operate, they are a source of odor, take up a lot of room, are subject to weather, and require a lot of labor. So they are not such a good solution. Mechanical dewatering of the sludge is usually preferred. In the early days, this consisted of vacuum filters and pressure filters using Lime and Ferric Chloride to condition the sludge. These were large cumbersome systems with low capacity, and poor (by modern standards) performance.
The first successful centrifuges used in sewage dewatering were basket centrifuges. Sludge poured into the spinning centrifuge, and compacted under 1000 g or less. When full, the