DIRK – Sludge Thickening at Wessex Water.Services Limited

Wessex Water Services Limited provide water and sewerage services in the South West of England covering an area of 10,000 square kilometers including Dorset, Somerset, Bristol, Bath, most of Wiltshire and parts of Gloucestershire and Hampshire. Drinking water is supplied to around 1.2million people in 513,000 properties and sewerage services to 2.5million people.

Dirk European Holdings Limited were awarded a contract for the supply of a mobile drum thickener for sludge thickening at Dorchester
WwTW, Dorset.

The project involved mechanical thickening of 20m3/hour of co-settled primary and humus sludge with a feed dry solids of 1.5%. The thickened sludge, 6% dry solids, is then pumped to a thickened sludge storage tank before being fed to the on-site digesters.

The drum thickener has a simple design with low operational costs making it an economical alternative to gravity thickeners, centrifuges and dissolved air flotation units.

Solids capture rate is usually greater than 99% with clear filtrate being returned to the wastewater treatment process.

Advantages of drum thickener

•	Compact and robust construction
•	Little maintenance due to easy access for changing the filter cloth
•	Low emissions from the filter drum enclosure
•	Water saving by re-use of filtrate as spray water for filter cloth washing
•	Optimal flocculation with variable polymer / sludge ration
•	Degree of thickening adjustable by variable drum rotation speed
•	Automatic shut-down in case of failure

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