Rotary drum thickener, Siljan RotoMaster

The first Siljan RotoMaster prototype was installed in 1988 in the waste water treatment plant of Bylandet in the community of Smedjebacken, Sweden. The performance of the first Siljan RotoMaster was very good.

Since then, more than 150 rotary drum thickeners of this type has been installed in municipal waste water treatment plants in Sweden and many other countries.

Rotary drum thickeners have also been installed within the pulp and paper industry, chemical industry and process industry, among others.

The main function of the Siljan RotoMaster is as follows: The incoming sludge to be thickened, is flocculated by means of a suitable polymer (Poly electrolyte) into larger particles. The sludge and polymer is mixed in a conical mixer and the mixture is allowed to flocculate in a static mixer, for the smaller machines, or in a flocculation reactor for the bigger machines (more than 35 m3/h). The flocculated sludge then enters into the rotating drum of the Siljan RotoMaster.

The drum of the Siljan RotoMaster consists of a strong filter cloth with a suitable mesh size. The drum is rotating at a low speed, about 10 rev./minute. The water will pass through the filter cloth, while the sludge will be retained on the inside of the drum and a thickening to 5-12% DS of the sludge will occur.

The filter cloth is cleaned by high pressure water spraying from the outside of the filter cloth.

In this process, the flocculated sludge is treated gently, the polymer consumption is kept at a low level and the sludge thickening results is a stable and easy to control process.

The DS-content of the thickened sludge is controlled by the incoming DS-content, the rate of polymer addition, the rotation speed of the drum and the slope of the drum. While many factors e.g. drum rotation speed, sludge type and feed rate of the polymer effect the DS content, the Siljan RotoMaster consistently thickens sludge to 5-12% dry solids content with a minimum of operator input.

20 years of experience show that the drum thickener has an excellent function with a very long service life, often exceeding 10 years for the critical components, such as the filter cloth, motor and gearbox, bearings etc. The first machine taken into service in Smedjebacken, Sweden, is still in service without any problems. This machine was upgraded with a PolySave unit during the year 2000, which improved its performance and lowered the polymer consumption.

Siljan Allards AB, Tel. +46(0)248-125 35 Fax +46(0)248-137 85
E-post info@siljanallards.com www.siljanallards.com